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177 Cards in this Set
- Front
- Back
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What are the benefits of endotracheal intubation?
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*Establish patent airway
-important in case of emergency -Allows for more efficient delivery of O2 or O2 & Gas to aveoli *Prevent aspiration of vomit/ secretions -Loss of swallowing reflex under anesthesia *Intermittent Positive Pressure Ventilation (IPPV)-can bag patient -Decrease gas exposure to staff |
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What are 3 types of ET tubes?
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-Murphy (most common)
-Cole tubes (small animals, exotics, birds) -Cuffless ET tube -for small animals & exotics -sometimes a cuffed tube can be very difficult to insert |
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What are the qualities of a cole tube?
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-Used for small animals and exotics
-Skinny end is inserted into trachea -tied behind ears so wider part creates seal around tracheal opening -Are easily dislodged |
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What are some basic qualities of Murphy ET tubes?
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-Most commonly used
-Beveled end makes it easier to insert -Has Murphy eye on the end to prevent complete obstruction -has a cuff -has a pilot line with pilot balloon -radio-opaque strip |
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What are the pilot line and balloon used for?
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To inflate and deflate the ET tube cuff
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What does the Pilot balloon have to prevent deflation?
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self-sealing valve
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What are the benefits of a cuffed ET tube?
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-Prevents aspiration
-Prevents leakage of gas into the room -Prevents animal from breathing room air -do NOT hold ET tube in place |
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How are ET tubes usually sized?
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By internal diameter
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How is appropriate ET tube size determined?
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-Based on animals ideal weight
-Brachycephalics tend to have smaller tracheal diameter -Opening of tube is usually same diameter as distance between nares |
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What size should you always choose in regards to ET tubes?
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Always choose largest size that will pass easily and not damage larynx or trachea-less resistance to respiration.
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Length of tube is important as well as diameter and ideally it should match the length between tip of nose and _____________
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Thoracic inlet/ manubrium
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What issues do ET tubes that are too long cause?
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Endobronchial intubation-
- only one lung is being ventilated (may hear different lung sounds) -unventilated lung may be at risk for atelectasis -May see increased resistance to respiration. |
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What is one other way to make sure the ET tube is inserted to the proper length?
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Cuff should just disappear into trachea
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When inserting ET tube, is it better to hold teeth or lips?
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Lips
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What are the basic steps for intubation?
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-Lube with sterile water or lube
-Hold tube like a pencil with curve down -Visualize epiglottis -With tube-pull epiglottis down ventrally. -Visualize vocal folds -whiter in color -tube should pass between vocal folds and cuff should JUST disappear into trachea |
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What are some ways to confirm tube is in trachea?
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-Best way is to visualize tube in trachea
-use fingers to feel for tube between vocal folds -Feel air with exhalation -tube will cloud with exhalation -Reservoir bag moves with resipration -PALPATE for one tube -If animal can vocalize, tube is not in trachea |
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If ET tube is in esophagus:
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-Animal will not stay anesthetized
-inflation of cuff will not fix a suspected leak -Reservoir bag will not move much -Animal can vocalize -Animal may become hypoxic since O2 is being delivered to stomach |
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Cuff inflation basic facts:
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-Cuffs do not always need to be inflated
--ALWAYS check first and throughout anesthesia if cuff needs to be inflated or inflated more (listen and smell for suspected leak) |
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What are 2 ways to know how much air to use to inflate cuff?
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1. Back pressure on syringe tells you when to stop is easiest
-this is the only way with NRB 2.Use the pressure manometer while ventilating -will hear a slight leak at 20cm H2O pressure -No leak at 15 cm H2O |
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What species is more prone to tracheal damage with over-inflation of a cuff?
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cats
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What are some issues related to over-inflation of ET tube cuff?
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-Compression of tracheal lumen
-Pressure necrosis and tracheal rupture |
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What are some reasons that cats are more difficult to intubate?
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-Smaller
-Larynx sits deeper in the neck--->harder to visualize -Vocal folds cover more of the glottis -More prone to laryngospasms and closes tightly |
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What are a few ways to make intubating cats easier?
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-Use a stylet with tube to make tube more rigid
-should not extend beyond end of tube and is removed once tube is placed -Use lidocaine to decrease layngospasms |
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What is the preferred way to administer Lidocaine to cats when used to assist intubation?
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Draw up 0.1 of lidocaine, remove needle
Place one drop on each vocal fold |
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How does a laryngoscope assist intubation?
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Blade depresses tongue and a light source assists visualization
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What are some possible associated with endotracheal intubation?
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-Pressure necrosis of lining of trachea (more common in cats)
-Plugged tube (esp. cats-mucus plug) -Kinked tube -Stimulation of vagus nerve which leads to decreased HR, RR -Trauma to Larynx, Pharynx, vocal folds -common for animal to cough for up to 2 days -Recovering animal could chew tube |
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How do you decide animal should be extubated?
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-Animal should show signs of recovery
-Once animal is in recovery-untie gauze and attach syringe to pilot ballon to be able to remove tube quickly -Extubate after 2 good successive swallows or if animal tries to stand and/or chews tube |
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How are ET tubes cleaned?
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-Not usually sterilized
-Cleaned with dilute antiseptic like chorhex, which is milder to tissues. -Is OK to submerge under water -Inflate cuff to remove all mucus. -use brush or pipe cleaner to clean inside -Rinse with water and hang to air dry |
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What is the goal of induction agents?
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Unconsciousness for intubation
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If an animal is on inhalants and complications with those ensue, what is typically done?
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Turn off gas and give CRI of Propofol
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What are the reflexes do we keep track of during anesthesia?
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-Corneal
-Ear flick -Palpebral -Pedal -Jaw tone -Eye position -Pupil size -Swallowing |
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What is the corneal reflex and what should happen with this reflex?
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-Animal should blink and withdraw the eye into the orbit
-should be present during safe planes of anesthesia -not routinely done w/dogs and cats unless we think they are dying |
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What is the Ear flick reflex and what should happen with this reflex?
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-Gently touch hairs inside of ear and observe for ear flick
-may be present or absent during safe/surgical planes of anesthesia -may or may not be helpful due to its inconsistent results -Absent at safe surgical depths |
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What is the Palpebral reflex and what should happen with this reflex?
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-AKA Blink reflex
-When medial canthus is gently tapped, blink is typical result -Usually disappears during safe surgical planes of anesthesia |
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What is the Pedal reflex and what should happen with this reflex?
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-When digit or pad is squeezed, animal withdraws limb
-Should be ABSENT during safe/surgical planes of anesthesia |
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In regards to Jaw tone and safe stages/planes of anesthesia, what should be seen?
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-When jaw is opened, jaw tone is lessened but still somewhat present in adults.
-puppies and kittens have weak tone -if adult animal is slack, the are too deep |
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In regards to Eye position and safe stages/planes of anesthesia, what should be seen?
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-Eyes typically rotate ventromedially
-Exopthalmic breeds may not do this -If eyes are central, animal may be too deep or possibly too light |
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In regards to pupil size and safe stages/planes of anesthesia, what may be seen?
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-Should be slightly dilated
-Anticholinergics may also cause this |
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In regards to Swallowing and safe stages/planes of anesthesia, what should be seen?
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-Should be absent-one reason why we intubate
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In regards to stages and planes of anesthesia, Stage I is nicknamed what because what happens?
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Voluntary excitement phase
Struggling, vocalization and other signs of fear and excitement |
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In regards to stages and planes of anesthesia, when does Stage I occur and what signs will we see in the typical animal?
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*occurs immediately after administration of injectable or inhalant
-Animal is conscious but disoriented -Can't intubate yet -show reduced sensitivity to pain -HR, RR can be normal or increased -All reflexes present -Eyes central -*MAY LICK OR SNIFF |
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In regards to stages and planes of anesthesia, Stage II is nicknamed what because what happens?:
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Involuntary Excitement Stage
-Rapid movement of limbs, vocalization, struggling. -Looks like animal is fighting anesthesia but these are not conscious actions |
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In regards to stages and planes of anesthesia, when does Stage II occur and what signs will we see in a typical animal?
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*Begins with loss of consciousness
-All reflexes present -Animal is able to chew and swallow -Sighing/licking are common -Pupils dilated -Breathing may be irregular -May appear to hold breath -Still cannot intubate |
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Why does the excitement occur in Stage II anesthesia?
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Because anesthetics selectively depress neurons in the brain that control and inhibit the function of motor neurons, more common when barbituates are given too slowly.
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What is a concern for Stage II for animals and staff?
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A struggling animal can injure itself, the restrainer or anesthetist.
This struggling can result in a release of Epinepherine which can result in cardiac arrythmias and arrest |
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How do we deal with the involuntary excitement issues that arise in Stage II?
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Try to eliminate or shorten Stage II with induction of anesthesia, with the right PAs and induction with IV anesthetics.
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In regards to stages and planes of anesthesia, Stage III, Plane 1, when does it occur and what are the unique features of this stage?
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*Light plane of anesthesia
-Can be intubated-able to open mouth wide & pull on tongue -Respiratory pattern becomes regular -muscles relax -reflexes become slower -eyes start to rotate ventral/medial -Palpebral reflex still present -**Not able to withstand surgery yet** |
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In regards to stages and planes of anesthesia, Stage III, Plane 2, when does it occur and what are the unique features of this stage?
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*Medium plane of anesthesia**
-Suitable for MOST surgical procedures -will see some response to surgical stimulation (increased HR & RR) but Pt will remain unconscious and immobile -Respirations regular but shallow (8-30bpm) -HR & BP mildly decreased -eyes central rotated -3rd eyelid prolapsed -dilation of pupils -protective reflexes diminished or absent -Palpebral, pedal reflexes absent -relaxation of muscle tone, moderate jaw tone |
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In regards to stages and planes of anesthesia, Stage III, Plane 3, when does it occur and what are the unique features of this stage?
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**deep plane of anesthesia**
-Significant depression of circulation and respiration -EXCESSIVELY deep for most surgical procedures -Shallow respirations <12 per min -decreased HR, even with surgical procedures -Hypotension, reduced pulse strength -Increased CRT -Eyes central, pupils dialated Reflex activity absent -Marked muscle relaxation-slack jaw tone |
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In regards to stages and planes of anesthesia, Stage III, Plane 4, when does it occur and what are the unique features of this stage?
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**Anesthetic OVERDOSE**
-Too deeply anesthetized -*Danger of respiratory and cardiac arrest -Rocking ventilatory pattern-ventilation with abdominal muscles, thoracic muscles become relaxed -Eyes central, pupils FULLY DILATED and NO PUPILLARY LIGHT REFLEX -Eyes become dry -Muscle tone is flaccid -Drop in HR, BP, pale MM, prolonged CRT ***Turn Vaporizer down or off*** |
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In regards to stages and planes of anesthesia, Stage IV when does it occur and what are the unique features of this stage?
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*cessation of respiration
*cardiac arrest Death ** CPR is needed to save patient's life |
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Why is the induction phase considered a vulnerable stage?
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Because animal is moving from conscious to unconsciousness and the ET tube is not in yet.
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What is the basic procedure for induction at Bel-Rea and most clinics?
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-PA given
-IVC placed -Propofol given-IV, slowly, titrated to effect -Intubated -O2 Flow meter turned on -Attached to patient -Monitor respirations-good, steady, even? -turn on vaporizer -pass esophageal stethoscope -inflate cuff if needed -lube eyes -monitor |
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Induction checklist-what are some items that need to be taken care of prior to Induction?
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-know patient. be familiar with breed,
P/E, lab radiograph findings -Classify anesthetic risk accordingly -Know what drugs you are using and their +/- effects and possible interatctions -Have fluids ready -Place IV Cath -Anesthetic machine is checked and ready to go -O2 tank level, ISO/Sevo level, Pressure check, granules, passive scavenge -Eye lube is ready -Esophageal steth ready -measure from tip of nose to mid-sternum -Endotrach tube & supplies ready -check cuff prior to inflating |
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What is the goal of anesthetic induction agents?
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Create unconsciousness
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What are the commonly used Anesthetic Induction agents?
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-Barbituates
-Cyclohexamines (dissociatives) -Propofol -Etomidate -Neuroleptoanalgesia -Guaifenesin-not an anesthetic but a very good muscle relaxant used with other drugs (GKX used with Equines) |
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What are the 3 main uses of Barbituates, an anesthetic induction agent?
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-induces anesthesia
-maintain general anesthesia -anticonvulsants -Euthanasia |
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Barbituates are classified according to their duration. What are the 3 classes?
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-Ultra-short-methohexital, thiopental (no longer used)
-Short-pentobarbital -Long-phenobarbital (anticonvulsant) |
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Phenobarbital is a long acting barbituate with a duration of general anesthesia of _______ hours and is primarily used as an ___________ .
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6-12 hours
anticonvulsant |
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Short acting barbituate Pentobarbital qualities:
Onset: Duration: |
-Onset following IV is 30-60 secs.
-Duration of GA is 1-3 hours -Used as a euthanasia solution (double the anesthesia dose) **NOT reversible** |
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the Ultra-Short barbituates Thiopental, Methohexital last for how long?
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10-20 minutes
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What are some common features of ALL barbituates?
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*CONTROLLED substances**
NOT reversible -NO analgesia -IV administration only ---->irritating to perivascular tissues |
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Barbituates vary in:
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Lipid solubility
Distribution in the body Onset of action Duration |
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How does lipid solubility affect the speed of barbituates effects?
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The MORE lipid soluble the barbituate, the faster acting the drug
-Quicker onset -shorter duration of anesthesia -more rapid activity |
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High lipid solubility enhances Barbituates ability to cross the BBB and enhance entry into brain to produce
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unconsciousness
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High lipid solubility of Barbituates also enhances entry into what other tissues but at a lesser amount due to less blood supply than the brain?
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Muscles and fat
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Barbituates with the highest lipid solubility are the ____________
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ultra-short acting
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In regards to barbituates, how do they move through the body to produce their effects? Remember, these follow the laws of diffusion....
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-Following IV administration, barbituates enter the brain due to high lipid solubility and good blood supply brain receives.-UNCONSCIOUSNESS results
-Blood levels decrease as the drug moves to brain -Drug then starts moving back to blood and is redistributed to muscle and esp. fat. -As Drug leaves the brain, animal starts to regain consciousness -move from fat and muscles to be metabolized by the liver and excreted in the urine |
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Barbituates recovery occurs due to:
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-Redistribution from the brain to muscle and especially fat
-Metabolized by liver -Excreted in the urine |
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What animals have increased potency and duration in regards to barbituates?
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-Sighthounds
-Really skinny animals -Recovery involves redistribution from brain to fat and these animals have little to no body fat |
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What effects do barbituates have on the CNS?
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-CNS depression
degree depends on dose & type sedation to surgical anesthesia -Are anticonvulsants phenobarbital -Excitement occurs during induction and recovery -prolonged Stage II (involuntary) -less likely with Ultra short |
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What effects are seen on the respiratory system with Barbituates?
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-Potent respiratory depressants
-Decreased RR & depth -Respiratory acidosis & hypoxemia -Apnea with rapid administration or high doses -Intubation is always recommended **NOT reversible |
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What is one procedure where barbituates are not recommended and why?
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C-sections
Respiratory depression of neonates |
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What effects do Barbituates have on the cardiovascular system?
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-Cardiovascular depressants
-Euthanasia solutions are concentrated pentobarbital -Decreased BP and cardiac output **Increases hearts sensitivity to epinephrine-will see arrythmias (PVCs) |
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In the blood, some barbituates will bind with protein and only unbound barbituates will enter the brain, so an animal with hypoproteinemia will have what happen?
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More unbound barbituates in the blood lead to more in the brain so drug is more potent
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If an animal has hepatic or renal disease, what kind of recovery should be expected and why?
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Prolonged recovery
Due to delayed metabolism and excretion |
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With barbituates, the induction and recovery phase have what concerns and how can we minimize these?
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-Perivascular or slow administration can result in Stage II excitement
-give 1/3 to1/2 dose as bolus, then titrate to effect to minimize -PA tranquilizers & opioids can help decrease this phase |
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Why are barbituates given IV?
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-Perivascular administration is very irritating due to their alkaline nature
-Perivascular injection will result in pain, swelling, tissue necrosis and sloughing within about 2 days -If injected perivascular, immediately infiltrate area w/equal volume of isotonic saline, +/- Lidocaine |
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Thiopental is and Ultra-short acting and was
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the most commonly used short acting barbituate used as an induction agent or sole agent for short diagnostic or surgical procedures.
(no longer made) |
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Methohexital/Brevital is an expensive ultra-short acting barbituate that is best for use in:
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Sight hounds since recovery is less dependent on fat metabolism and is rapidly detoxified by the liver.
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Barbituates should not be used for repeated doses because
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effects are cumulative and recovery will be prolonged.
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What are the 2 Cyclohexamines/dissociatives used for Induction?
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-Ketamine/Ketaset, Ketalar, Vetalar
-Tiletamine (in Telazol with Zolazepam) -common induction agents or as sole agents for short procedures -Used in many animal species-cats, dogs, horses, birds, reptiles, lab animals |
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What are some basic facts about Cyclohexamines/dissociatives?
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CONTROLLED substances
-NOT reversible Some analgesia -IV or IM administration -IM is irritating but does not cause tissue sloughing |
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How do Cyclohexamines/dissociatives affect the CNS?
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CNS STIMULATION rather than depression like most anesthetics
-disrupts/scrambles nervous system pathways -Trance like anesthesia-animal appears awake but immobile and unaware |
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How do Cyclohexamines/dissociatives affect the cardiovascular system?
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-Most animals will show tachycardia (unlike most anesthetics that cause bradycardia)
-Will use glycopyrrolate instead of atropine. Lower HR w/o causing bradycardia -use with caution in animals with cardiac problems |
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How do Cyclohexamines/dissociatives affect the respiratory system?
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-Can cause Apneustic respiration which is characterized by holding of breath at end of inspiration with a prolonged pause after inspiration.
-Can be stimulated to breath by tapping nose or rubbing thorax |
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With Cyclohexamines/dissociatives, muscle tone is
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Increased-->catalepsy
-opposite most anesthetic agents -Spontaneous random limb movements unrelated to pain may result -Diazepam may result |
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With Cyclohexamines/dissociatives, some reflexes remain intact and may be
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exaggerated
-Pharyngeal and laryngeal reflexes remain but should still be able to intubate -Palpebreal reflex may be exaggerated -these can make it difficult to assess depth |
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With Cyclohexamines/dissociatives, what effects can we expect to see with the eyes?
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Palpebral reflex can be exaggerated
-Eyes remain open, central with dilated pupils -Nystagmus, especially in cats -Ptyalism -Increased salivation, anticholinergics will decrease this |
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Cyclohexamines/dissociatives tend to provide more analgesia to ___________ and less to ___________
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skin and limbs
viscera |
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Cyclohexamines/dissociatives are metabolized by what in dogs and cats?
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Dogs metabolize them through the liver but cats just excrete it through kidneys and skip the liver
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Ketamine is the MOST common induction agent used, can be used alone for short procedures. What are the advantages of IV administration of this drug?
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-Faster onset of action
-Decreased dose compared to IM -No tissue irritation |
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What are the advantages of IM administration of Ketamine?
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-Fractious cats/wild animals
-Can also be squirted into mouth and oral Ketamine takes effect in about 5-10 minutes |
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Ketamine IV administration onset and duration are?
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O of A-30-90 seconds
D-3-10 minutes |
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Ketamine IM administration onset and duration?
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O of A-2-4 minutes
Duration: dog-20-30 minutes cat 30-60 minutes Complete recovery in 2-6 hours |
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It is very common to combine Ketamine with _____________, and for what effects?
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A tranquilizer such as Diazepam, acepromazine, medetomidine, xylazine, guaifenesin(horses)
-increases muscle relaxation, smoother recovery, decreases seizure potential (diazepam) |
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What are some of the more common Ketamine combos?
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-Ket-Val-very common, safe IV induction in dogs and cats & can mix in same syringe
-Ketamine-midazolam- IV or IM -Ketamine-xylazine-common in equines |
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Tiletamine is a newer dissociative found only in Telazol and is often mixed with what to get what effect?
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Zolazepam-(benzodiazepam tranq)
decreases risk of seizures, increases muscle relaxation, smoother recovery |
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Telazol can be given what routes?
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IV, IM or SQ
-very useful for aggressive dogs and cats -used for capturing wildlife |
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Propofol is a common IV induction agent or sole agent for short procedures, apporved for dogs but also used in cats. What are some other important facts about this drug?
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-Oil in water emulsion , looks milky white
-NOT controlled -NO analgesia -NOT reversible but metabolized quickly |
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What are the effects of Propofol on the cardiovascular system?
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-Hypotension immediately after injection **Give FLUIDS!
-usually of short duration in healthy patients -may be prolonged in some patients -Avoid use in animals with pre-existing hypotension (shock, blood loss) |
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What are the effects of Propofol on the respiratory system?
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Respiratory depression
-transient apnea can occur following rapid IV administration -give slowly over 20-60 seconds -titrate to effect while monitoring respirations carefully for first couple of minutes |
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Propofol is a very _________ anesthetic agent with rapid onset, short duration of anesthesia and smooth recovery. It is __________metabolized with ________ "hang over" and a wide margin of safety.
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short
rapidly minimal |
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Propofol onset of action is less than 60 seconds and duration of anesthesia is ________
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5-10 minutes
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Propofol is short acting, can be administered repeatedly to maintain anesthesia because it __________
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does not accumulate in tissues
-intermittant boluses given every 3-5 minutes to maintain anesthesia or as a CRI |
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Propofol has a limited shelf life due to not having preservatives and because it contains
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soybean oil and lecithin which support the growth of bacteria
-Manufacturer says to use bottle w/in 6 hours--many say it is ok tp extend to 24 hours |
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Etomidate/Amidate is a rapid acting, ultra short, non-barbituate, non-cumulative anesthetic that has what other qualities?
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NO analgesia
Good muscle relaxation -NOT controlled -NOT reversible, but metabolized rapidly -Very expensive -more commonly used in humans |
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Etomidate/Amidate has what effects on the body?
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-minimal effects on cardiovascular function
-Mild respiratory depression (transient apnea with induction -Wide margin of safety -Excellent induction agent for difficult cardiac cases and high risk patients -Induces rapid loss of consciousness, rapid smooth recovery |
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Neuroleptoanalgesics are not used in what animals for induction but can be used in which population?
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-young, healthy animals-does not produce unconsciousness
-Sick/debilitated animals |
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Guaifenesin, GG or GGE is a
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-Muscle relaxant, not anesthetic
-given to large animal to induce -Usually in combo with ketamine, diazepam and or xylazine |
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What is the triple drip?
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Common induction combo used in horses.
Xylazine-sedation and analgesia Guaifenesin IV, muscle relaxant Ketamin IV for recumbancy |
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What is the purpose of Inhalent anesthetics?
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For induction and maintenance of anesthesia of anesthesia
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Liquid anesthetics are vaporized and delivered by _______
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carrier gas- O2 to patient through inspiratory tubing via an ET tubing or mask/chamber
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Gas anesthetics cross the aveoli to the blood stream and rate of diffusion is controlled by
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Concentration between aveoli and bloodstream
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During induction, concentration of gas in alveoli is ________ and concentration of gas in bloodstream is ____________
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alveoli -high
bloodstream- low |
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Tissues such as the brain with _______ blood flow are quickly saturated with anesthetic gases.
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greater
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Depth of anesthesia is determined by
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concentration of anesthetic in the brain
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Anesthesia is maintained by
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insuring concentration of anesthetic in alveoli, blood and brain is maintained
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During recovery, the concentration of anesthetic is reduced and recovery begins when
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-Begins when concentration of gas in blood is less than brain, gas diffuses to the blood, then ...
-concentration of gas in alveoli is less than blood, which allows anesthetic gas to diffuse from blood to aveoli and then be exhaled. |
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Animals should breath 100% O2 for ______ after vaporizer is turned of because:
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up to 5 minutes
-Filling alveoli w/100% O2 creates a steep concentration steep concentration gradient between blood and alveoli which speeds up recovery -Allows exhaled anesthetic gas to go to scavenge |
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Common inhalants require precision vaporizers and these are _________ which means
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VOC-vaporizer out of circuit
they sit out of the breathing circuit because they they create high resistance to gas flow |
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Respirations do or do not affect vaporizer output.
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DO NOT-vaporizer sits outside breathing circuit
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What are the inhalant gasses?
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-Nitrous Oxide (N2O)-Laughing gas
-Halothane/Fluothane-discontinued -Isofluranne/Aerrane, Florane, Isoflo) -Sevoflurane/Ultane, Sevoflo -Desflurane/Suprane |
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Use of Nitrous oxide has declined in veterinary medicine recently but has what advantages?
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-Wide margin of safety due to minimal effect on cardiovascular, respiratory, hepatic and renal systems
-Provides good analgesia and muscle relaxation -Usually used in conjunction with other agents to improve analgesia and muscle relaxation. |
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Use of N2O can ___________ amount of inhalant anesthetic, which reduces adverse effects of inhalants and speeds up recovery.
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decrease
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N2O is delivered from a blue tank attached to anesthesia machine with it's own flowmeter & is mixed with _______________
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O2 to become the carrier gas for inhalent anesthetics, so patient breathes a mixture of O2, N2O, and inhalant gas
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N2O comes in a blue tank with the N2O in a liquid and gas pressurized state but pressure gauge reads only pressure of gas in tank. As gas leaves tank, the liquid N2
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evaporates and becomes a gas, therefore pressure gauge will not change until all of the liquid has evaporated and the gas begins to be used up.
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N2O cannot be used as a sole carrier gas and must be mixed with _______ at a rate of no more than __________
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O2
1.5 to 2 times O2 flow |
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What are some other risks associated with N2O?
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-likes to diffuse into air filled spaces and will increase air in those spaces, so avoid use in GDV, intestinal obstruction, pneumothorax
-Diffusion Hypoxia-during recovery large N2O molecules leave aveoli rapidly and can displace O2 molecules, so VERY important that animal breath 100% O2 and be ventilated for 5 minutes after tuning N2O off. |
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What are the basic effects of inhalant anesthetics on respiratory system?
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Respiratory depression/hypoventilation-
*decreased RR & TV *can lead to respiratory acidosis (hypercapnea) & atelectasis |
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What are the basic effects of inhalant cardiovascular system?
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Cardiovascular depression
*vasodialation * decreased cardiac output *bradycardia *hypotension *decreased tissue/organ perfusion (kidneys---nephrons...) |
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Inhalant anesthetics tend to increase the hearts sensitivity to
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epinephrine, although no so much of an issue with Iso and Sevo
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Effects of inhalant anesthetics are dose related with reversible CNS depression and provide what kind of muscle relaxation and analgesia?
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Fair to good muscle relaxation
Slight analgesia during administration and post-op |
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Inhalants are classified by 3 physical properties which are:
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-Vapor pressure
-Solubility -MAC- minimum alveolar concentration |
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Why do we ventilate animals during anesthesia?
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-To blow off Co2
-To prevent atlectasis |
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Vapor pressure measures
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tendency of liquid gas to go from liquid to gas.
-Inhalant with high vapor pressure WANT to be a gas and therefore evaporate readily |
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Due to their high vapor pressure , if the concentration delivered to patient is not precisely controlled with the precision vaporizer, the concentration of the gas delivered to the patient
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can easily become fatal.
Precision vaporizer is required to precisely control the % of gas and each inhalant has its own type of vaporizer |
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Solubility coefficient (blood:gas solubility coefficient) measures
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the solubility of an anesthetic gas in rubber tubing, blood, fat and other tissues
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Solubility provides info on __________ of induction, depth change and recovery.
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speed
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Inhalants with LOW solubility will move rapidly to brain because inhalants with low solubility are INSOLUBLE and therefore do not _____
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want to stay dissolved in blood, fat tissues etc, so move QUICKLY to brain.
Gas goes from aveoli-->blood to brain--->brain. Low soluble means it does NOT dissolve in blood or tissues (does not stick)--so moves quickly to the brain |
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LOW solubility = ________ gas
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Fast gas
Faster induction, faster depth changes and recovery |
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High soluble/ solubility inhalants are ____________
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Slower--slow to be absorbed by tubing, blood, fat, tissues, brain
which results in a slower induction, slower depth changes, and slower recovery |
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Inhalant gases from lowest to highest solubility-therefore from fastest to slowest (SIH).....
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Sevo
Iso Halothane |
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Does solubility affect amount of drug given?
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NO
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Inhalants with Low solubility are best for mask/chamber induction because
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-faster induction, less struggling, stress and allow for rapid recovery
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Minimum Aveolar Concentration (MAC) is the
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minimum alveolar concentration (%) of a gas that produces no response to surgical stimulation in 50% of the patients.
-Measures % of gas in alveoli |
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MAC gives an indication of _________
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potency
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The higher the MAC, the __________ potent the inhalant gas.
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LESS
-because the gas requires a higher % in the alveoli to reach the point where there is no response to surgical stimuli. |
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The Lower the MAC, the __________
potent the inhalant gas. |
MORE
-because the gas requires less to reach a point where there is no response to surgical stimulation. |
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A gas that has a high MAC value is less potent, so requires ________ vaporizer settings to maintain surgical anesthesia.
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higher
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MAC values help us know vaporizer settings.
1 x MAC = 1.5 x MAC= 2 x MAC = are general guidelines |
light anesthesia
surgical plane of anesthesia deep anesthesia |
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What are some items that will affect MAC and vaporizer settings?
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Age & condition of Pt
Disease PA and induction drugs |
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Inhalant anesthetics from lowest to highest MAC, so most to least potent:
(HIS) |
Halothane
Isoflorane Sevoflorane -Sevo has the highest MAS, so is the least potent and will require higher vaporizer settings to maintain a surgical plane of anesthesia. |
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What are some adverse effects of Halothane?
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*Sensitizes heart to epinephrine induced arrhythmias
-increase vagal tone-bradycardia -decreases myocardial contractility and cardiac output **vasodialtor-cause hypotention and hypothermia **Respiratory depression-decreased RR and TV |
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Halothane is metabolized ____ by liver and the rest is eliminated by respiratory tract.
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20%
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Halothane has what positive effects?
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-Adequate/fair muscle relaxation
-Slight analgesia |
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Malignant hyperthermia is an adverse effect that can happen with any inhalent but tends to happen more with Halothane. What is it?
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Rare but often fatal disorder of thermoregulation that will result in the animals showing increased temperature, muscle rigidity and cardiac arrhythmias
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What are the basic properties of Isoflorane?
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-High vapor pressure (vaporizer goes up to 5%)
-Low solubility---means it is fast -rapid induction, depth change and recovery (changes within 1-2 minutes) -has pungent odor but rapid induction makes this great for mask/chamber induction |
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Isoflorane has a higher MAC and induction with injectable on board typically requires starting at what % setting on vaporizer?
For mask/chamber? |
2.5%
3-5% |
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What is the typical maintenance % for ISO?
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1.5-2.5%
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What effects does ISO have on the body?
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Commonly used inhalant with wider margin of safety than Halothane
-Little effect on the heart-safest -Will cause vasodialation -Respiratory depression-more than halothane, decreased RR and TV |
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How much of Isoflorane is actually metabolized?
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0.2%, rest is exhaled
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What are some other benefits/effects of Isoflorane?
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Excellent muscle relaxation
-little or no analgesia post-op so Pre-emptive and post-op analgesia very important to prevent wind-up |
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Sevoflorane is the newest inhalant anesthetic with the following properties:
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-Lowest solubility-fastest gas
-Highest MAC-least potent, higher vaporizer settings needed -Rapid changes in depth of anesthesia-within 3-4 breaths *Rapid recovery so ***don't turn off vaporizer until Sx is complete -non-pungent odor, less irritating to MM, so may be more tolerable for mask/chamber induction |
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Induction % with Sevo with injectable PA on board usually starts at ______ and for mask/chamber?
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4%
6-8% |
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What % is Sevo vaporizer set at for maintenance?
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2.5-4%
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What are the effects of Sevoflorane on the body?
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-Greater effect on the heart than ISO but still considered safe
-Causes Vasodialation -Causes respiratory depression-slightly more than ISO -Moderate muscle relaxation -**Little or no analgesia post-op *manufacture states that cognitive and motor functions return simultaneously which results in a smoother recovery |
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Desflurane/Suprane is the least soluble of all inhalants, has highest MAC and vapor pressure is extremely high requiring a heated vaporizer. What does this mean in regards to speed of this inhalant?
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Lowest solubility means fastest but highest MAC means least potent
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What is the main benefit for Induction chambers?
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Requires little physical restraint
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What are some disadvantages of induction chambers?
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Difficult to monitor patient in chamber
-No control of airway -Not a good induction method for brachycephalics or animals w/respiratory or cardiovascular problems |
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What are the 2 ports on an induction chamber for?
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-inlet for gas, O2
-Outlet for scavenge -Attached to RB system with pop-off valve closed. |
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What is the basic induction chamber procedure?
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-Deliver 100% O2 at a 3-5L/min rate for about 5 minutes to get patient used to chamber and ***increase O2 saturation of Hgb
-Gradually add inhalant anesthetic -Increase amount by 0.5% every 10 seconds to allow them to get used to the smell -Require higher vaporizer settings 3-5% ISO and 6-8% SEVO |
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What do you want to see in order to know animal is ready to be removed from chamber to be intubated?
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-Loss of righting reflex
--Tap and shake chamber and animal does not get up |
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What is one risk to staff with induction chambers?
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Exposure to gasses when animal is removed from chamber.
--Put lid back on as quick as possible |
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Mask induction works best with ISO and SEVO, but sevo smells better. This technique MAY be beneficial for induction of high risk patients because
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if problems occur, can immediately discontinue induction
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Mask induction is NOT recommended for what types of patients?
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Brachycephalics
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What types of breathing systems can be used with Mask induction?
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Rb & NRB both
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