Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
46 Cards in this Set
- Front
- Back
|
Minimum Alveolar Concentration (MAC)
|
Concentration of anesthetic in the brain that prevents movement of 50% of subjects in response to a standard surgical incision.
|
|
|
Partial Pressure
|
PA = nA RT
V PB = nB RT V PT = PA + PB |
|
|
Solubility of a gas in a liquid
|
Solubility is the volume of gas dissolved in a unit volume of liquid at a stated temperature. The amount of gas dissolved in a liquid is proportional to the partial pressure in the gas phase and the partition coefficient of the gas.
|
|
|
Partition Coefficient
|
Ratio of the solubility of an agent in two media, such as blood and brain or lung and blood at equilibrium.
Example: Halothane has a blood-gas partition coefficient of 2.3 which means that the number of moles in the blood phase is 2.3 X the number of moles in the gas phase (lungs). |
|
|
Stages of Anesthesia
Stage 1 |
Amnesia / Analgesia
pupils small, nystagmus muscle tone, reflexes intact |
|
|
Stages of Anesthesia
Stage 2 |
Delirium / Excitement
unconscious pupils dilated, divergent muscular movement; vomiting increased RR, BP, HR airway reflexes intact: laryngospasm |
|
|
Stages of Anesthesia
Stage 3 |
Surgical Anesthesia
small pupils gaze fixed and midline increased frequency and regularity of respiration; decreased tidal volume net result: decreased minute ventilation since Ve=Vt x RR loss of protective airway reflexes |
|
|
Stages of Anesthesia
Stage 4 |
Overdose / Apnea
shallow or absent respirations dilated, non-reactive, mid-position pupils suppression of CNS activity cardiovascular collapse |
|
|
Factors affecting MAC
|
a. Decreases with extremes of age.
b. Decreases with hypothermia and increases with hyperthermia. c. Decreases with preanesthetic administration of narcotics, benzodiazepines and barbiturates. d. Decreases with acute ethanol intoxication, increases with chronic alcoholism. e. The effect of nitrous oxide concurrently administered with a potent agent is additive (70% nitrous oxide + 1 MAC potent agent = 1.7 MAC). |
|
|
Nitrous oxide
|
Respiratory
Alveolar ventilation is maintained. Cardiovascular It is a mild myocardial depressant in healthy patients. It activates the sympathetic nervous system. |
|
|
Halothane
Respiratory effects |
It is a potent bronchodilator. It causes a stereotypical increase in respiratory rate and decrease in tidal volume. It depresses the normal response to hypoxia and shifts the carbon dioxide curve down and to the right. It is commonly used in pediatrics for inhalational induction.
|
|
|
Halothane
CV effects |
It is a potent negative inotrope. Ventricular end-diastolic pressures increase. It has little direct effect on systemic vascular resistance. Like all potent agents it causes a dose-dependent decrease in mean arterial pressure. It markedly inhibits baroreceptor function. Halothane decreases sympathetic outflow. It, therefore, causes a decrease in heart rate by this mechanism. It decreases rate of conduction making reentry more likely. It decreases SA-node automaticity as well. It sensitizes the heart to the arrhythmogenic effects of circulating catecholamines
|
|
|
Halothane
Neurologic effects |
The EEG pattern is slowed and of high amplitude. Cerebral blood flow increases and so intracranial pressure may increase with its administration. It decreases cerebral metabolic rate for oxygen. It has muscle relaxant properties.
|
|
|
Isoflurane
Respiratory effects |
An effective bronchodilator, it impairs hypoxic drive and shifts the carbon dioxide response curve further to the right than does halothane. It is very irritating to the airways.
|
|
|
Isoflurane
CV effects |
It differs from halothane in that it is an ether. Ethers tend to stabilize the myocardium and are less arrhythmogenic. It is a positive chronotrope and decreases inotropy less than halothane does. This coupled to a decrease in systemic vascular resistance results in better preservation of cardiac output. It does, however, cause a dose-dependent decrease in blood pressure. There is less depression of baroreceptor function than with halothane.
|
|
|
Desflurane
|
Desflurane is very similar to isoflurane in terms of physiologic effects. It has the lowest blood:gas partition coefficient of any inhalational agent, so an advantage is rapid wake-up. It is not used for inhalational induction since it is very pungent and is associated with a high incidence of breath holding, coughing, and laryngospasm
-deSFLURane: SFLUR looks like SULFUR, and this one is stinky (not used for inhalation induction) |
|
|
Sevoflurane
|
Sevoflurane has essentially no odor and is a very smooth agent for inhalational induction. It is a very cardio-stable drug and its blood:gas partition coefficient confers fairly rapid induction and emergence characteristics.
S is for: Smooth Smells good Stable heart Solubility low Save me from toxic intermediates |
|
|
Sevoflurane
Side effects |
Sevoflurane undergoes biotransformation and hydrolysis in soda lime (which is used for carbon dioxide absorption in anesthesia machines) to potentially toxic intermediates such as Compound A and B which may cause renal injury and carbon monoxide.
|
|
|
Nitrous oxide
Side effects |
Impairs DNA synthesis when given for a prolonged period of time. Prolonged exposure may result in megaloblastic anemia and neuropathies. Nitrous oxide is also highly diffusible into air-filled spaces and so it may increase the size of a pneumothorax or pneumocephalus.
|
|
|
Malignant Hyperthermia (MH)
|
Susceptibility may be associated with a specific genotype involving the ryanodine receptor which is responsible for calcium transport at the level of the sarcoplasmic reticulum. MH is familial.
Patients with myopathies are particularly at risk, such as Duchenne’s Muscular dystrophy and myotonic dystrophy , however, it can occur in patients with no known specific risk factors. It is potentially triggered by all of the potent agents and by depolarizing muscle relaxants such as succinylcholine. It is characterized by a hypermetabolic state (hyperpyrexia, tachycardia, hypercarbia, hypoxia, progressive acidosis) and by muscle rigidity, rhabdomyolysis and frank myonecrosis with secondary renal failure in survivors. It is fatal if untreated. |
|
|
Malignant Hyperthermia (MH)
Treatment |
Treatment consists of administering dantrolene, which binds to the ryanodine receptor and interferes with calcium flux. Treatment also consists of rapid surface and luminal cooling, hydration, diuresis, treatment of acidosis, hyperkalemia and alkalinization of the urine to prevent intratubular precipitation of myoglobin.
Non-triggering intravenous agents can safely anesthetize patients and families who may be susceptible to MH. Dantrolene must always be available in any anesthetizing location and can be life-saving. Dan rescues his friend Ryan (the ryanodine receptor) from drowning in a pot of boiling water (malignant hyperthermia) Dan is so HOT! (remember it's related to malignant hyperthermia) |
|
|
Propofol
Properties |
isoproyl phenol - lipid soluble
a. Rapid induction. b. Rapid awakening. c. Significant anti-emetic properties. d. Exhibits a context sensitive half-life when administered as an infusion for prolonged periods of time (its half-life increases with the length of infusion). Not "Proper" for "pro"longed use especially in people with mitochondrial disorders |
|
|
Ketamine
Properties |
Structure - phenylcyclidine derivative similar to PCP
Properties a. Potent amnestic. b. Potent analgesic. |
|
|
Etomidate
Properties |
Properties
a. Rapid induction and emergence. b. Remarkably cardiovascularly stable. c. No increased intracranial pressure. "Tom" is for "tomahawk": good for patients with major head trauma (no increased in intracranial pressure) Like an Eton man: seems perfect (no increase in ICP, quick induction/emergence, few CV effects) but will make you vomit, twitch, and mess with your hormones |
|
|
Remifentanil
|
Potent, ultra-short acting synthetic opioid of the phenylpiperidine class that undergoes rapid hydrolysis by plasma esterases
Remembered, Felt Nil - analgesic/sedative, but no amnesic effects "Remi-" rhymes with "memory" b/c it won't take your memory (not amnesic) |
|
|
Remifentanil
Properties |
Properties
a. Short half-life requires that it be administered by continuous infusion. b. Half life is not context sensitive c. Decreases HR and RR- effect may be dramatic. No effect on SVR when administered alone. Remembered, Felt Nil - analgesic/sedative, but no amnesic effects "Remi-" rhymes with "memory" b/c it won't take your memory (not amnesic) |
|
|
Remifentanil
Uses |
Uses
a. Produces sedation and analgesia without amnesia. Used for surgery and painful procedures |
|
|
Remifentanil
Side effects |
Side Effects
a. Acute tolerance to the drug may occur b. Increased opioid requirement during post-operative convalescence has been reported following remifentanil use intra-operatively. c. Profound bradycardia, apnea and chest wall rigidity may occur |
|
|
Etomidate
Uses |
Include patients with head injuries associated with increased intracranial pressure due to brain edema or an intracranial hematoma, patients in severe heart failure due to cardiomyopathy and patients with severe forms of pulmonary hypertension
|
|
|
Etomidate
Side effects |
Side effects
a. High incidence of post-operative nausea and vomiting. b. Inhibition of adrenal 11-beta-hydroxylase activity, causing a decrease in serum gluco and mineralocorticoid levels, even after a single dose. c. Myoclonus on injection. |
|
|
Propofol
Uses |
a. Short procedures.
b. Procedures outside the operating room. |
|
|
Propofol
Side effects |
a. Cardiovascular properties similar to barbiturates (depression).
b. Can contribute to bradycardia. |
|
|
Ketamine
Uses |
Originally designed for use on healthy patients who have suffered major trauma because it stimulates the sympathetic nervous system.
|
|
|
Ketamine
Side effects |
a. Marked sialorrhea; usually given with an antisialogogue.
b. Myocardial depression; however, its activation of the sympathetic nervous system usually overrides this effect. c. Emergence phenomena such as hallucinations; can be countered by co-administration of benzodiazepines. d. Increased intracranial pressure. e. Causes dissociation between limbic and thalamic systems; patients appear cataleptic. |
|
|
Dexmedetomidine
Properties |
Structure- an imidazole; presynaptic alpha-2 agonist
Properties a. Decreases BP and HR b. Causes sedation c. May cause a decrease in minute ventilation, but patients will almost invariably respond to verbal/tactile stimulation to breathe when used alone |
|
|
Dexmedetomidine
Uses |
a. Produces sedation only; no amnesia or analgesia. Used for surgery and sedation in the ICU setting.
b. May be useful for treatment of post-operative delirium or shivering. |
|
|
Post-operative issues
Drug induced Liver Injury (DILI) |
Very rare. Formerly called “Halothane Hepatitis”, there is now evidence that other potent agents may very rarely be associated with an autoimmune-based hepatitis.
The mechanism of injury involves antibody formation to a protein-hapten conjugate. The hapten is a metabolite of the parent vapor. Hepatitis may develop 3 weeks after exposure. Females seem to be at increased risk as are individuals with known autoimmune diseases. It is associated with both an increase in transaminases and cholestatic jaundice. |
|
|
Post-operative Nausea and Vomiting (PONV)
|
principally associated with nitrous oxide, the opioids and the potent vapors. It is treated or prevented by administering a variety of antiemetics. Propofol is anti-emetic. Steroids may play a role in decreasing PONV when given as a single intra-operative dose and combined with a 5-HT3 antagonist.
|
|
|
Post-operative shivering
|
Shivering is a consequence of changes in thermal regulation brought on by both general and regional technique. It may be independent of hypothermia or may accompany hypothermia. Surface warming and/or administration of alpha-2 agonists treat it. Small doses of meperidine may also be helpful (if not otherwise contraindicated).
|
|
|
Awareness during surgery
|
More likely to occur under total intravenous anesthesia (TIVA) than under anesthesia with a volatile agent
With TIVA the principle analgesic is opioid, given in high doses. This approach usually results in hemodynamic stability but provides no amnesia. A benzodiazepine and sometimes nitrous oxide are relied upon for antegrade amnesia |
|
|
Scopolamine,
|
A centrally acting muscarinic antagonist may be given to help ensure both retrograde and antegrade amnesia. Scopolamine, may prolong emergence and contribute to emergence delirium.
|
|
|
Mitochondrial Disorders and General Anesthesia
|
Avoid the prolonged use of propofol for maintenance of anesthesia and to use neuromuscular relaxants judiciously.
For anesthetics consider local, opioid, benzodiazepine alone or in combination. Remifentanil, dexmedetomidine |
|
|
PropofolInfusion Syndrome (PRIS)
|
Progressive hepatic encephalopathy and lactic acidosis, lipemia, rhabdomyolysis, CVS collapse
-Follows prolonged infusions (48h or less?) and large cumulative doses -Pathophysiology: –May interfere with long chain FA transport into mitochondia and β-oxidation resulting in lower energy utilization |
|
|
Halothane
|
Gas used for inhalation anesthetics
-HALO for increased intracranial pressure. -H for historical, hydrocarbon -THANE for makes your heart and feeling WANE. |
|
|
Isoflurane
|
Vapor used for inhalation anesthetics
-"IsoFLurane keeps your heart FLowing" (less CV effects than halothane) |
|
|
Dantrolene
|
Used as treatment for malignant hyperthermia
Dan rescues his friend Ryan (the ryanodine receptor) from drowning in a pot of boiling water (malignant hyperthermia) Dan is so HOT! (remember it's related to malignant hyperthermia) |
