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229 Cards in this Set
- Front
- Back
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What is Standard I?
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Perform and document a thorough preanesthesia assessment and evaluation.
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What is Standard II?
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Obtain and document informed consent, or verify that informed consent has been obtained and documented.
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What is Standard III?
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Formulate a patient-specific plan for anesthesia care.
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What is Standard IV?
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Implement and adjust the anesthesia care plan based on patient's response to the interventions. Intervene as needed to keep patient in optimal physiological condition.
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What is Standard V?
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Monitor, evaluate and document the patient's condition as appropriate. All monitoring devices should have alarms on and audible. The CRNA sa
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What is Standard VI?
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Document pertinent anesthesia-related information in a timely manner.
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What is Standard VII?
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Evaluate patient status and determine when it is safe to transfer care.
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What is Standard VIII? |
Adhere to appropriate safety precautions. Ensure that equipment is ready. Make sure anesthesia machine is set to monitor inspired oxygen concentration continuously with an oxygen analyzer.
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What is standard IX?
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Verify that infection control policies and procedures exist. Adhere to policies.
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What is standard X?
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Participate in ongoing review and evaluation of anesthesia care to assess quality and appropriateness.
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What is standard XI?
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Respect and maintain the basic rights of patients
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Define cultural awareness
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A collection of skills that allow individuals to be cognizant of the similarities and differences among cultural groups
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Define diversity
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All the ways in which individuals and groups differ and recognizing how these differences should be valued
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What is equity?
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Fair treatment, access, opportunity and advancement for all individuals and groups
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What is cultural competence?
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A collection of skills that improve understanding, sensitivity, appreciation, and responsiveness to cultural differences and interactions resulting from them
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Define inclusion
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The act of creating an environment where any individual or group can be and feel welcome, respected, supported, and valued to fully participate
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What is general anesthesia?
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A drug-induced reversible depression of the CNS resulting in lots of response to and perception of all external stimuli
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Name three different types of general anesthesia
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IV induction with inhalational maintenance, Total IV anesthesia, inhalational anesthesia
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Describe stage one of general anesthesia
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Amnesia and analgesia: respirations are present and quiet with intact reflexes
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Describe stage two of general anesthesia
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Excitement or delirium: Respirations are irregular increased muscle tone involuntary movements dilated peoples disconjugate gaze vomiting or aspiration
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Describe stage III of general anesthesia
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Surgical anesthesia: ranges from LOC with regular respirations, decreased muscle tone, absent cough or gag reflex and normal pupils to total muscle relaxation, nonreactive pupils and cessation of spontaneous respirations |
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Describe stage four of general anesthesia
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Anesthetic overdose: irreversible anesthesia, pupils fixed and dilated, cardiac arrest imminent, no respirations, require cessation of all anesthetics, ventilation with 100% oxygen and supportive measures |
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List the 5 steps in the administration of general anesthesia |
1) Pre-op preparation 2) Induction of anesthesia 3) Maintenance of anesthesia 4) Emergence from anesthesia 5) Post-op |
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Sodium pentothal |
IV anesthetic, induction occurs within one arm-Brian circulation time (60 seconds) |
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Brevital |
IV anesthetic, onset of action in 30-40 seconds, duration of action of 5-7 minutes, used with ECTs. |
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Propofol |
IV anesthetic, used for short procedures, reduces nausea, patients wake up "bright eyed and bushy tailed", can have a continuous infusion without cumulative effects |
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Etomidate |
IV anesthetic, lasts 3-5 minutes, used for patients with impaired CV function (often in geriatrics) |
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Ketamine |
IV anesthetic, "dissociative anesthesia", characterized by intense analgesia, amnesia, cataleptic state of unconsciousness, used for hemodynamically unstable patients |
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What is the Unitary Hypothesis?
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Oldest theory: suggests that all anesthetic agents have a common mechanism of action:; anesthetics dissolve into nerve-cell membranes and produces structural change, results in depressed function of nerves
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What is the Meyer-Overton Theory?
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Implies a unitary molecular site of action and suggests that anesthesia results when a specific number of anesthetic molecules occupy a crucial hydrophobic region of the (the # of molecules at the site, not the type)
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What is the multi-site agent specific theory?
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More than one site and MOA is involved for anesthetic agent and different anesthetics have varying effects at each site, molecular targets are ion channels that regulate the flow of ions across the membrane
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What are 2 types of ion channels?
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Voltage-sensitive: open and close depending on cell membrane voltage, represented by Na, K, Cl, CA Ligand-gated: Nicotinic cholinergic receptors and amino acid receptors |
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What happens with activation of gamma aminobutyric acid receptors?
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Cell hyperpolarization or an increase in ion conductance that prevents depolarization leads to inhibition of neuronal activity.
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How do general anesthetics affect GABA receptors?
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They increases the sensitivity of the receptors and lead to inhibition of neuronal excitability
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What are 3 sites of action of anesthetics?
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Cerebral cortex, brain stem (inhibit brainstem reticular formation and depress blood flow and glucose metabolism, selectively depress several brain regions) spinal cord (decrease transmission of noxious information ascending from spinal cord to brain |
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What does the upper airway consist of?
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The nose, mouth, pharynx (naso, oro, laryngo), and larynx |
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Where is the pharynx?
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Extends from the base of the skull to the bottom of the cricoid cartilage anteriorly and the bottom of the C6 vertebrae posteriorly
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Where is the nasopharynx?
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Behind the nasal cavity and above the soft palate, extends from the posterior nares to the oropharynx, including adenoids
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Where is the oropharynx?
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Extends from the soft palate to the base of the lingual surface of the epiglottis. Includes soft palate, tongue, tonsils, vallecular and epiglottis.
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Where is the laryngopharynx?
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Extends from the level of the hyoid bone to the opening of the esophagus at the level of the cricoid cartilage
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List some functions of the larynx.
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Maintain patent airway Guards against aspiration Vocalization |
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What is the narrowest part of the adult upper airway?
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The glottis opening
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How many cartilages make up the larynx?
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3 unpaired: thyroid, cricoid and epiglottis 3 paired: arytenoids, corniculates, cuneiforms |
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What is the membrane between the hyoid bone and the thyroid cartilage called?
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Thyrohyoid membrane
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Where is the cricothyroid membrane?
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Below the thyroid cartilage and above the cricoid cartilage
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What is the largest cartilage in males?
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the thyroid cartilage, "Adam's apple"
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What is the anterior attachment for the vocal cords? |
the thyroid cartilage
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What is the most prominent cartilage in females?
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the cricoid cartilage
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Where is the cricoid cartilage?
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at the level of C4-5-6 in adults and C-4 in infants
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What is the narrowest portion of the upper airway in pediatrics?
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Cricoid cartilage
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What is the only complete ring in the larynx?
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the cricoid cartilage
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What's the purpose of the epiglottis?
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it is leaf shaped and covers the glottis opening to prevent entrance of solid foods or liquids into the airway
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Where is the vallecula?
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in between the bases of the tongue and the epiglottis
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Describe the arytenoid cartilages.
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Sit on the cricoid cartilage and has a muscular process that is the insertion of the posterior and lateral cricoarytenoids. Each has a vocal process that is the posterior attachment of the vocal cords. |
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Describe the corniculate cartilages.
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Each is attached to the apex of an arytenoid cartilage. Situated in the posterior part of the aryepiglottic folds. |
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Describe the cuneiform cartilages.
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Elongated structures located slightly posterior to corniculates at the base of the epiglottis.
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What are the aryepiglottic folds?
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Folds of mucous membrane attaching the arytenoid cartilages to the epiglottis
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What are the false vocal cords?
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Folds of mucous membranes that are attached to a narrow band of fibrous tissue(true vocals)
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What are the true vocal cords?
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two bands of yellow, elastic fibrous tissue; the anterior attachment is the thyroid cartilage and the posterior attachment is the arytenoids
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Describe the trachea.
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begins at the inferior border of the cricoid cartilage, continues about 10-15cm; bifurcates at level of sternal angle (junction of T4 and T5); composed of 16-20 incomplete cartilaginous rings |
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What side of the trachea is the cartilage on: anterior or posterior
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Anterior
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List the extrinsic muscles of the larynx. What do they do?
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Sternohyoid, sternothyroid, thyrohyroid, omohyoid. These muscles move the larynx as a whole. |
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List the intrinsic muscles of the larynx.
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Posterior cricoarytenoid Lateral cricoarytenoid Arytenoids Cricothyroid Thyroarytenoid |
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How does movement of the posterior cricoarytenoids affect the vocal cords?
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They rotate the arytenoids outward, thus abducting the vocal cords. They are the only muscle that abducts the cords. |
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How do the lateral cricoarytenoids move the vocal cords?
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They adduct the vocal cords by rotating the arytenoids inward.
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How do the transverse and oblique arytenoids move the vocal cords?
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They adduct the vocal cords by approximating the arytenoids.
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How do the thyroarytenoids affect the vocal cords?
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They relax and shorten the cords by drawing the arytenoids forward.
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How do the cricothyroids move the vocal cords?
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They tense and elongate the vocal cords by drawing up the arch of the cricoid and lifting back its lamina
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What provides the sensory innervation of the pharynx?
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CN IX - glossopharyngeal
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What CN provides the motor function for the pharynx?
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CN X - vagus *primary motor function is swallowing* also CN IX - glossopharyngeal |
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Which nerves innervate the tongue?
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CN V - trigeminal CN VII - facial (taste) CN IX - glossopharyngeal (taste plus sensation) CN X - vagus: internal branch of the superior laryngeal nerve CN XII - hypoglossal (motor innervation) |
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Which CN gives motor function to the upper esophageal sphincter?
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CN IX - glossopharyngeal
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What does the internal branch of the superior laryngeal nerve do?
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Supplies sensory innervation above the vocal cords
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What does the external branch of the superior laryngeal nerve do?
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Supplies the motor innervation to the cricothyroids
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What does the recurrent laryngeal nerve do?
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Supplies motor innervation to all muscles of the larynx except the cricothyroids Supplies sensory innervation to the subglottis and trachea |
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Where does the recurrent laryngeal nerve get its name from?
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Because they follow a recurrent course from the vagus nerve. The right side wraps around the subclavian before going up to the larynx and the left side wraps around the aorta.
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Unilateral damage to the recurrent laryngeal nerve can do what?
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Cause hoarseness
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Bilateral damage to the recurrent laryngeal nerve can do what?
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Cause complete airway obstruction
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How is the upper portion of the larynx supplied with blood?
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Aorta supplies common carotid artery which splits into the internal and external carotid artery. The superior thyroid artery branches off the external carotid artery. The superior laryngeal artery branches of the superior thyroid artery.
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How is the lower portion of the larynx supplied with blood?
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Subclavian artery gives rise to the thyrocervical trunk. The inferior thyroid artery branches off that. The inferior laryngeal artery comes off the inferior thyroid artery.
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What are three parts of evaluating a patient's airway?
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Careful pre-op physical examination of the head and neck. Review of medical history. Any previous airway difficulty |
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List some potential difficult airway predictors.
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Short muscular neck obesity prominent dentition cranio-facial deformities recessed chin restricted neck range of motion enlarged tongue cervical collar or traction external trauma |
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What is the lemon law?
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L: look externally, E: evaluate 3-3-2, M: Mallampati score, O: obstruction, N: neck mobility
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What is 3-3-2?
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3: temporal mandibular joint - should allow 3 fingers between incisiors 3: thyromental distance - should be 3 fingers between mentum and hyoid bone 2: should be 2 fingers between the hyoid bone and the thyroid cartilage (identifies larynx in relation to base of tongue) |
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What does it mean if the thyromental distance is less than or greater than three fingers?
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Less than: mandibular space may be too small, obstructs visualization of the glottis opening Greater than: elongates oral axis, more difficult to align the three axis |
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What does it mean if there are more or less than 2 fingers between the hyoid bone and the thyroid cartilage?
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Less than: anterior larynx Greater than: obstructive view of the glottis opening d/t increased distance from base of tongue |
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What makes up a Class I Mallampati score?
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You can see the faucial pillars, uvula, soft and hard palate (PUSH)
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What makes up a Class II Mallampati score?
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You can see the uvula, soft palate and hard palate (USH) (also the base of the faucial pillars)
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What makes up a Class III Mallampati score?
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You can see the soft palate and the hard palate (SH) (also the base of the uvula)
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What makes up a Class IV Mallampati score?
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You can only see the hard palate (H)
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What might you hear if you have an obstructed airway?
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Snoring - obstruction of upper airway by tongue Gurgling - obstruction of upper airway by liquids Wheezing - narrowing of lower airways Stridor Complete airway obstruction is silent |
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What can you do to alleviate airway obstruction?
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Perform chin lift Insert oral or nasal airway |
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What airway would you place in a patient with a basilar skull fracture?
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Oral
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Which airway would you place in a patient with a gag reflex?
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Nasal
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What does a positive "prayer sign" indicate?
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this is when a patient is unable to approximate the palmar surfaces of the phalangeal joints while pressing their hands together, thought to represent cervical spine immobility, seen in patients with poorly controlled diabetes
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Name some differences in an infant airway
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Head is larger larynx is more cehphalad and anterior laryns starts at C1-2 and is at C3-4 by age 2 Larger tongue longer, omega shaped epiglottis (at 8 years old, airway resembles an adults) |
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What is the smallest portion of a pediatric airway?
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Cricoid
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Where do you put your fingers when ventilating with a mask?
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On the bone, not the soft tissue; downward pressure applied with thumb and index finger, middle and ring finger grasp mandible to facilitate atlanto-occipital extension, little finger slides under angle of jaw and thrusts it anteriorly
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What are the facial landmarks that must be approximated by the mask cushion to achieve effective seal?
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nasal bridge, two malar eminences (below eyes), alveolar ridge (below mouth)
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What are the signs of successful mask seal and ventilation?
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mask fogging, chest rise with positive pressure, breath sounds on auscultation, firm/taught/full reservoir bag, ETCO2 on exhalation
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How do you measure a nasal airway?
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measure from nares to meatus of ear |
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Name a disadvantage of an oral airway
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can cause laryngospasms if put in too early or too far
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What is a LMA?
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a supraglottic cuff device that surrounds and covers the supraglottic area and provides sufficient seal to allow for positive pressure ventilation to be delivered (only up to 20cm H2O pressure or else it will bypass cuff and go into esophagus)
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Name/describe several types of LMAs
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LMA Classic - multi use LMA Unique - single use, pretty basic LMA Supreme - elliptical airway tube, bite block, drain tube which can pass OG LMA Flexible - non-kinkable, do not use for emergency airway LMA Proseal - has tunnel for OG tube, higher sealing pressure (works better with PPV), not for emergency airway, bite block, inserted with a metal introducer LMA Fastrach - facilitates blind intubation, epiglottic elevating bar, guide channel for ETT |
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What are some indications for LMA placement?
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Routine procedures as an alternative to mask Procedures where tracheal intubation is not necessary |
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What are some contraindications to LMA
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"full" stomach gross obesity pregnancy trauma hiatal hernia decreased lung compliance positioning Relative contraindications: blood or fluid in pharynx, recent local radiation, type and length of surgery |
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How do you know if your LMA is placed correctly?
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during placement: resistance at end of insertion when inflating cuff you will see: outward movement of LMA, anterior displacement of larynx, inability to advance LMA further after placement: black line midline with incisors, able to generate airway pressure, able to ventilate manually, condensation of expired gases, CO2 on capnography, movement of anesthesia bag with return of spontaneous resp. |
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What do you do if your patient regurgitates following LMA insertion?
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tilt head down - disconnect anesthesia circuit - deepen anesthesia - suction through LMA - consider intubation
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What size LMA would you use in a 5kg baby? 5-10kg? 10-20kg? What is the max cuff inflation volume for each?
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5kg: 1, up to 4ml 5-10: 1.5, up to 7ml 10-20: 2, up to 10ml |
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What size LMA would you use in a 20-30kg child? 30-50? What is the max cuff inflation volume for each?
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20-30: 2.5, up to 14ml 30-50: 3, up to 20ml |
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What size mask would you use in a 50-70kg adult? 70-100kg? Over 100kg? What is the max cuff inflation volume for each?
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50-70: 4, up to 30ml 70-100: 5, up to 40ml over 100: 6, up to 50ml |
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How do you determine ETT size for children over 2 years old?
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(age in years)/4 + 4 |
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What size ETT would you use in an infant under 1 year? How about a child under 2 years?
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1 year: 4-4.5mm 2 year: 4.5-5mm |
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What is the average size ETT for an adult female?
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7.0-7.5
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What is the average size ETT for an adult male?
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7.5-8.0
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How do you estimate the depth of ETT insertion?
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3 x ETT size (mm) *tube is 4mm x3 = 12cm* |
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How do you estimate the depth of ETT insertion in a newborn?
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6 + weight in kg *baby weighs 2kg - insert 8 cm* |
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How do you estimate depth of insertion in a child over 2 years?
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12cm + (age in years/2) *kid is 4 - 4/2=2 + 12 = 14cm* |
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What is the average depth of ETT insertion in an adult female?
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19-21cm
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What is the average depth of ETT insertion in an adult male?
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21-24cm
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There are two types of laryngoscope blades. What are they called and how do they work?
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Miller: straight tongue with slightly curved tip, works by directly lifting the epiglottis *may be challenging to use this blade with soft tissue or a large floppy epiglottis, #2 is standard blade size Macintosh: curved blade, works by indirectly lifting the epiglottis, tip needs to be in the vallecula, #3 is standard blade size |
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What are some indications for tracheal intubation?
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need a patent airway, prevent aspiration, pt requires frequent suctioning, facilitate PPV of lungs, maintain adequate oxygenation by allowing for peep, operative position other than supine, operative site involves airway, difficult mask airway, upper airway disease, paralysis needed for procedure
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There are three axes: the oral axis, pharyngeal axis, and laryngeal axis. What must happen in order for successful intubation?
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They must all be aligned. One achieves this by proper head and neck placement during laryngoscopy.
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What is the greatest obstacle to laryngoscopy?
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The tongue
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What complications can occur at intubation?
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Trauma to teeth, lips, tongue, pharynx, larynx, nose Fracture/luxation of c-spine Hemorrhage Trauma to eye Aspiration of gastric contents Esophageal intubation (distention of stomach) Retropharyngeal dissection/abscess |
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What patient population is at high risk for atlanto-occipital instability and possible subluxation during intubation?
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Down's syndrome
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Describe the Cormack and Lehane Grading System for vocal cords
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Grade 1: all or most of glottis is seen Grade 2: only posterior portion of glottis is seen Grade 3: only epiglottis is seen Grade 4: no recognizable structures |
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What is de-nitrogenation? How do you do it? Why do it?
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the elimination of nitrogen from the lungs and body tissues during a period of breathing pure oxygen, achieved by getting a tight seal with O2 mask and giving 100% O2 for 5-10mins, it washes out the nitrogen and builds up a reserve in functional residual capacity so that if patient is apneic, they can draw O2 from FRC and maintain O2 sat
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Who should get de-nitrogenation?
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geriatrics, obese, peds, full stomach, pregnant, reflux hx, incompetent esophageal sphincter
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Can you de-nitrogenate with a nasal cannula?
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NO! But you can pre-oxygenate with one.
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What complications can occur while intubated?
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obstruction of the airway rupture of trachea/bronchus aspiration of stomach contects displacement of tube ignition of tube ruptured cuff |
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What complications can occur at extubation?
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difficult extubation airway obstruction aspiration of stomach contents |
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What complications can be seen post extubation?
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Sore throat Damage to lingual nerve Glottic edema Vocal cord paralysis Infections Laryngeal ulcer/fibrosis |
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How do you confirm placement of ETT?
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Direct visualization of tube going through vocal cords Presence of sustained physiologic end-tidal CO2 Condensation in tube Auscultation of chest and epigastrum |
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What is the Mendelson Syndrome?
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seen after aspiration of acid liquid significant alveolar-capillary breakdown and intense capillary congestion of the alveolar walls, interstitial edema and alveolar hemorrhage, hypoxemia, destruction of surfactant, alveolar edema, atelectasis gastric pH below 2.5 and a volume of ~25mL are critical factors for development of pulmonary injury |
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What can you expect to see following aspiration of a non-acid liquid?
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Immediate decrease in PaO2, atelectasis, pulmonary edema Pulmonary values usually return to normal after 24 hours |
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List the signs/symptoms of aspiration
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Hypoxemia most reliable sign coughing rales, rhonchi, wheezing bronchospasm cyanosis/shock pulmonary edema positive chest xray |
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Which anesthetic drugs can decrease tone of the lower esophageal sphincter?
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anticholinergics, thiopental, opiates, some inhaled agents, nitrous
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Which anesthetic drugs can increase the tone of the lower esophageal sphincter?
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antacids, metoclopramide, edrophonium & neostigmine, succinylcholine, pancuronium
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What is the Sellick's maneuver?
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Cricoid pressure: posterior displacement of the cricoid cartilage against the cervical vertebrae to prevent regurgitation and aspiration of stomach contecnts
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When is cricoid pressure applied and how much force is necessary?
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It is initiated before induction at about 20 Newtons force and increased to 40N following induction. Maintain force/pressure until intubation is successful.
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What is BURP?
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Backwards Upwards Rightwards Pressure - used to facilitate visualization of the glottis during intubation
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What is rapid-sequence induction?
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1)Pre-oxygenate 2)Sellick's maneuver 3)Induction meds given bolus 4)Succs of NDMB agent given 5)No artificial ventilation 6) Rapid intubation |
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What patients would RSI be indicated for?
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Patients at high risk of aspiration
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What is a modified RSI?
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Breaths given following induction meds and initiation of cricoid pressure
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What are the two types of extubation?
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Awake and deep
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Why would you give Lidocaine before extubation? What dosage?
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It may reduce the cough reflex and hyperdynamic response. Give 1.5mg/kg IV about 3 mins prior.
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What may happen if blood or excessive secretions enter the larynx after extubation?
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Laryngospasm
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What causes a laryngospasm?
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Spasm of adductor muscles closing, snapping shut the vocal cords - lateral cricoarytenoid is main muscle activated
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How do you treat laryngospasms?
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1) Gentle PPV with 100% O2 2) IV lildocaine 3) Consider propofol or deepening anesthesia 4) Succinylcholine .25-1mg/kg 5) Laryngospasm notch |
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What is a bronchospasm?
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Reflex response to intubation due to increase in bronchial smooth muscle tone which causes closure of small airways, most common in asthmatics/smokers
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How do you treat a bronchospasm?
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1) Deepen anesthesia 2) Inhaled beta-agonists (albuterol) 3) IV epinephrine |
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What is negative pressure pulmonary edema?
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pulmonary edema following intubation due to forceful inhalation against a closed glottis (or obstructed airway), this causes a drastic decrease in intrathoracic pressure that pulls fluid from the pulmonary capillaries (Nagelhout page 602) |
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How much is 1 atmosphere?
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760 mmHg
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What is pressure?
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a consequence of gas molecules "banging" against the container walls *measured in atmospheres, mmHg or kilopascals* |
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Boyles' Ideal Gas Law
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At a constant temperature, pressure is inversely proportional to volume. - if pressure increases, volume decreases - if volume increases, pressure decreases (boyles' = "boils", to remember temperature is constant) |
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Give an example of Boyle's Law
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Squeezing an ambu bag increases the pressure and decreases the volume During inspiration, intrapulmonary pressure falls and volume increases. With expiration, intrapulmonary pressure increases and lung volume decreases. |
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Use Boyle's Law to calculate how much gas is left in a cylinder at 500 psi.
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Capacity/Cylinder Service pressure = remaining content/cylinder gauge pressure 660L (in a full tank) = xL 2200psi 500psi x=150L O2 |
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Charles' Ideal Gas Law
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At a constant pressure, volume is directly proportional to temperature. *describes how gases tend to expand when heated* reference Seinfeld video clip |
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Give an example of Charle's Ideal Gas Law
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If air is left in the inflatable cuff of an LMA, during heat sterilization, the air within the cuff expands.
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Gay-Lussac's Ideal Gas Law aka "third gas law"
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At a constant volume, pressure is directly proportional to temperature.
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Give an example of Gay-Lussac's Law
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Increasing the temperature of a cylinder containing a gas increases the pressure and can lead to explosion.
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Ideal Gas Law aka "universal gas law" or "combined gas law"
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The states of an amount of gas is determined by its pressure, volume and temperature: PV=nRT unifies Charles, Boyle, and Gay-Lussac laws. *increasing or decreasing any of the values will require increasing or decreasing other values to keep the equation balanced. |
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Give an example of the ideal gas law
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PV=nRT A gas is released from a cylinder, thus the pressure inside decreases. The volume is constant, so as the gas goes out, the pressure decreases. n decreases so p decreases |
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Dalton's Law of Partial Pressure
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The total pressure in a mixture of gases is equal to the sum of the pressures of the individual gases.
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How do you calculate the partial pressure of a gas?
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multiply the percent of the gas by the atmospheric pressure *with a combination of gases, the total of all should be equal to the atmospheric pressure - so with room air at 760mmHg the O2 is 21% and N2 is 79%, pp of O2 is 160mmHg and pp of N2 is 600mmHg, together they equal 760mmHg* |
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Henry's Law
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The amount of a gas that is dissolved in a liquid is proportional to the partial pressure of the gas over liquid "as pressure increases, solubility of gas increases" |
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What is O2's solubility coefficient? How do you determine the amount of O2 dissolved in the blood?
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O2's coefficient is .003mL/dL/mmHg multiply the PaO2 by the coefficient |
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What is CO2's solubility coefficient? How do you determine the amount of CO2 dissolved in the blood?
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CO2's coefficient is .067mL/dL/mmHg multiply the PaCO2 by the coefficient |
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Graham's Law of Effusion
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The rate of effusion of a gas is inversely proportional to the square root of its molecular weight (larger molecules diffuse slower) *helium is a lighter gas and diffuses faster than oxygen, which is heavier* |
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Fick's Law
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The amount of gas diffusing across a semi-permeable membrane is directly proportional to: the partial pressure gradient, the solubility of the gas and the membrane area inversely proportional to: the membrane thickness and the molecular weight of the gas (explains why nitrous causes diffusion hypoxia) |
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What is the concentration effect?
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Gases move from areas in which they are in high concentration to where the concentration is lower (diffusion)
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Define diffusion
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process of movement of one type of molecule through space as a result of random motion - from high to low
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Define effusion
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process of gas molecules escaping through microscopic holes in their container (like helium in a balloon) |
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What is the 2nd gas effect?
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Administration of a faster drug (ie Nitrous) during administration of a relatively slow drug (ie isoflurane) can speed the onset of the slower drug (Nagelhout page 80) |
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What is diffusion hypoxia?
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When N2O is stopped it floods into the alveoli from the blood, taking the place of O2 and N2 in the process, this can cause hypoxia. To avoid this, administer 100% O2 for several minutes following the termination of N2O
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What is adiabatic cooling?
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the process of reducing heat through a change in air pressure caused by volume expansion
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Joule Thompson Effect
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when a compressed gas is allowed to escape freely into OPEN space, the process is adiabatic and cooling occurs example: cylinder cools and condensation forms after opening the valve *joule is cool* |
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What is adiabatic heating?
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If a cylinder of compressed gas is opened into a CLOSED space, the pressure in the closed space will rise rapidly and the temperature will also rise rapidly.
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What is a critical temperature?
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the temperature at and above which vapor of a substance cannot be liquefied, no matter how much pressure is applied *critical temperature for water is 374 degrees celcius* |
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How does Oxygen move?
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gets to the alveoli by bulk flow through conducting airways during inspiration, once at the alveoli bulk flow changes to diffusion; oxygen then moves through the gas phase in the alveoli according to partial pressure gradient; at the alveolar-capillary interface, O2 moves from gas to liquid where it then must dissolve and diffuse through multiple things including plasma, a majority enters erythrocytes and combines to Hgb and gets taken to the tissues where it diffuses from the erythrocytes and moves into tissue cells
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What are some limitations to gas transfer?
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-the diffusion coefficient is dependent upon the physical properties of the gases and the A-C membrane -the A-C membrane surface area & thickness can be altered by changes in lung volume, cardiac output, pulmonary capillary blood volume |
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Define Diffusing Capacity
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Rate at which O2 and CO2 are diffused between the lungs and the blood
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What can decrease diffusion capacity?
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-thickening of the barrier -decreased surface area -decreased uptake by erythrocytes -ventilation-perfusion mismatch |
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List for factors which influence the flow of oxygen from the alveoli to capillaries
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1) V/Q mismatch 2) right to left shunt 3) diffusion defects 4) CO |
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What does oxygen delivery to the tissues depend on? |
-The amount of O2 entering the lungs -The adequacy of pulmonary gas exchange -The blood flow to the tissue -The capacity of the blood to carry oxygen |
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What is the normal range of the O2 content of arterial blood? |
16 to 22 mL's 02/100 mL |
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What is a normal hemoglobin in a male? In a female? |
Male: 13-18 Female: 12-16 |
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What does SaO2 represent? |
The percentage of hemoglobin saturated with O2 |
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What does PaO2 represent? |
The arterial oxygen partial pressure |
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What does DO2 stand for? VO2? |
DO2 = oxygen delivery VO2 = oxygen consumption |
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How do you calculate oxygen delivery? |
CaO2 x cardiac output x 10 |
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How is oxygen mostly transported in the blood? What other way is it transported? |
Most of the oxygen is bound to hemoglobin on the red blood cell. There is a small amount that is dissolved in the plasma. |
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How do you calculate the oxygen that is dissolved in plasma? |
.003 x PaO2 |
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What is a normal PaO2 in a healthy patient? |
Around 100mmHg |
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What is the constant used to calculate dissolved 02? |
.003 |
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How do you calculate the oxygen that is bound to hemoglobin? |
Hgb x 1.34 x SpO2 = mL of O2/100mL of blood |
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What is the constant used when calculating bound oxygen? |
1.34 |
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What value tells us the total number of O2 molecules in arterial blood? |
CaO2 |
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How do you calculate the oxygen content of arterial blood? |
CaO2 = (Hgb x 1.34 X SaO2) + (PaO2 X .003)
*bound + dissolved |
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If you have a SaO2 of 75% what can you predict your PO2 to be? What if it's 90%? |
40mmHg 60mmHg at 90% |
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What is the normal resting O2 consumption range? |
250-400 mL O2/min |
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How do you estimate for PaO2 those on oxygen therapy? |
Multiply FiO2 X 5
Example: FiO2 is 50% = 250mmHg |
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How do you calculate the venous oxygen content in blood? |
CvO2 = (.003 X PvO2) + (1.34 X Hgb X mixed venous Hgb sat%) |
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How do you calculate oxygen delivery? |
DO2 = CaO2 X CO X 10 |
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What is the normal range for oxygen delivery? |
950-1150cc |
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How do you calculate oxygen consumption? |
Vo2 = (CaO2 a CvO2) X CO X 10 Normal range is 240-300 cc/min |
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If you have a patient with a hemoglobin of 15, CaO2 is 20 and CvO2 is 15, cardiac output is 2.5, what is the oxygen consumption? |
Vo2=125cc/min (Vo2 = (CaO2-CvO2) x CO x 10 *normal is 240-300* |
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Name some factors that increase O2 consumption (Vo2)
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surgery trauma burns sepsis pyrexia shivering seizure pain/anxiety SNS drugs infection |
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Name some factors that can decrease O2 consumption (Vo2)
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sedation/analgesics muscle paralysis shock hypothermia mechanical ventilation hyponutrition antipyretics |
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What is the normal O2 extraction ratio? (Vo2/Do2)
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0.2-0.3 |
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What does a rising O2 extraction ratio indicate?
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inadequate tissue oxygenation
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What does the difference between CvO2 and CaO2 indicate?
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Gives a good estimate of O2 delivery and O2 demand
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Your patient: Hgb 15 PvO2 40 mixed venous sat 75% PaO2 100 arterial sat 98% CO 5 Calculate the oxygen consumption of this patient. |
240 CaO2 = 19.99 CvO2 = 15.19 Vo2= (CaO2-CvO2) x CO x 10 |
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What is the oxyhemoglobin dissociation curve?
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an S-shaped curve that relates oxyhemoglobin saturation and partial pressure of O2 in the blood, determined by "hemoglobin's affinity for oxygen", helps us understand how blood carries and releases O2, P50 is used to indicate changes in the curve
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What does P50 correlate to in mmHg in the oxyhemoglobin dissociation curve?
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It lines up with 26.6mmHg on the O2 partial pressure side of the oxyhemoglobin dissociation curve; P50 refers to the position on the curve where Hgb is 50% saturated
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What does a rightward shift of the oxyhemoglobin dissociation curve mean?
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indicates an increased P50 and lowers hemoglobin's affinity for O2 -- meaning Oxygen is released to the tissues
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What does a leftward shift of the oxyhemoglobin dissociation curve mean?
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indicates a decreased P50 and increases hemoglobin's affinity for oxygen -- meaning Oxygen stays on the hemoglobin
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What PO2 can you expect with an oxyhemoglobin saturation of 50%? 75%? 90%?
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50% = 26.6 PO2 75% = 40 PO2 90% = 60 PO2 |
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What does the S-shape of the oxyhemoglobin dissociation curve demonstrate about saturation?
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-large changes in PO2 in the flat portion of the curve only causes minor changes in saturation -small changes in PO2 in the steep portion of the curve can cause large decreases in saturation |
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What are some things that can cause a rightward shift to the oxyhemoglobin dissociation curve?
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CADET = CO2, Acid (low pH), 2,3-DPG, Exercise, Temperature (increased levels) |
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What can cause the oxyhemoglobin dissociation curve to shift to the left?
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Decreased temp or 2,3-DPG Alkalosis (increased pH) Funny hemoglobins: carboxy, meth, fetal Low phosphate Remember: left starts with L and Lower levels of the above causes a leftshift |
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What is the Bohr effect?
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a low pH or high PCO2 that causes decreased affinity of hemoglobin for oxygen, shifts the curve to the right meaning P50 increases
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What is 2,3-DPG?
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an organophosphate created in erythrocytes during glycolysis; increased production occurs when there is diminished peripheral tissue O2 availability (hypoxemia, chronic lung disease, anemia); low levels are seen in septic shock and hypophosphatemia
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Which is more soluble: CO2 or O2?
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CO2, it is 20x more soluble than O2
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How is CO2 mainly transported in the blood?
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as bicarbonate ion (HCO3) - 90% of CO2 is transported this way
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Explain the conversion of CO2 to HCO3?
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CO2 generated in the cell, diffusion brings CO2 across the membrane and into plasma, it goes into the RBCs and binds with H2O (using carbonic anhydrase as catalyst) and converts to carbonic acid, it then breaks down into HCO3 and H, HCO3 then diffuses out of RBCs
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When HCO3 goes out of the RBC, what goes into the cell to maintain neutrality? What effect can this have on the cell?
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Chloride enters cell. osmolarity increases and swelling of the cell can occur
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What is the Haldane effect?
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the curve shifts based on how saturated the hemoglobin are; deoxygenated blood can carry increased amounts of CO2 and oxygenated blood has a reduced CO2 capacity; allows the blood to load more CO2 at the tissue level and unload CO2 at the lung (about 50% of CO2 excreted by lungs); high O2 concentrations increase unloading of CO2 and low oxygen concentrations increase loading of CO2 onto the hemoglobin
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