Anesthesia Pearls – Flashcards
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What is the risk of halothane anesthesia?
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Hepatitis with fever, eosinophils and jaundice
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How do volatile anesthetics affect respiratory muscle function?
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They depress synaptic transmission, preferentially affecting the intercostal muscles.
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What percentage of anesthetics induce atelectasis at 1h post-surgery? At 24h post-surgery?
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90% at one hour, 50% at 24h
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What antiemetic agent increases gastric motility?
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reglan
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How often is phrenic nerve paralysis found after cardiac surgery?
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in fewer than 10% of patients
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What conscious sedation agent is often used with children that increases cardiac work, secretions, and BP, and is not associated with respiratory depression?
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ketamine
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What muscle is typically the first to recover from paralytic therapy?
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the diaphragm
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What variable are associated with severe atelectasis following cardiac surgery?
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The number of saphenous vein grafts, the use of internal mammary artery grafts, the length of cardiac by-pass time and whether or not the pleural space was entered.
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What is the classic mechanism of phrenic nerve injury during cardiac surgery?
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Phrenic nerve frostbite from the cardioplegia solution. The phrenic nerve can also be mechanically injured in the dissection of the internal mammary artery because of its anatomic proximity.
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What proposed mechanism of atelectasis is unique to cardiac surgery?
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Cardioplegia solution finding its way into the pulmonary circulation. It is postulated that the high potassium chloride content of the solution damages pulmonary endothelial cells.
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How can the incidence of post-cardiac surgery atelectasis be decreased?
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The use of careful technique in mobilizing the internal mammary artery, using a pericardial insulating pad, avoiding entry into the pleural space and recovery of as much cardioplegia solution as possible before it enters the pulmonary circulation.
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What is the death rate from anesthesia in patients with an ASA class I or II?
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1 in 200,000
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T/F: Clindamycin prolongs the effect of nondepolarizing muscle relaxants.
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true
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What is the inheritance pattern and incidence of pseudocholinesterase deficiency?
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autosomal recessive with an incidence of about 1 in 3000
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How is the allowable blood loss for a patient calculated?
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in adults, estimated blood volume is 60-70cc/kg. ABL = EBV x (Hg [initial] -Hg [final]/Hg[initial])
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In patients planned for a CABG, what is the incidence of carotid disease?
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up to 38%
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How does renal failure affect the cardiac status of a patient?
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These patients are often plagued by hypertension volume overload, anemia, accelerated atherosclerosis and electrolyte abnormalities.
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What med is associated with decrease splanchnic blood flow?
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vasopressin--therefore used in GI bleeds
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T/F: Beta-blocker eye drops can cause bronchoconstriction in patients under anesthesia
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true
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What patients may have detrimental side effects from succinylcholine?
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Those with closed-angle glaucoma, space-occupying intracranial lesions and those with severe crush injuries of the lower extremity.
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Patients requiring an emergency tracheostomy for an obstructed airway may develop what postoperative pulmonary complication?
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pulmonary edema
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What is the treatment for malignant hyperthermia?
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Cessation of anesthesia, administration of dantrolene and general supportive measures.
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Which local anesthetics are amide compounds?
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lidocaine and bupivocaine
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What is the FEV1 below which a patient may not have general anesthesia?
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there is no absolute cutoff. There are reports of patients having general anesthesia safely with an FEV1 of around 450mL.
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Why do we wrap the sodium nitroprusside bottle in aluminum foil?
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To avoid the breakdown products of SN. Most notably CYANIDE, light enhances the formation of CN.
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What is the benefit of preoperative pulmonary prophylactic measures in patients with COPD?
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Decreased pulmonary complications.
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Should surgery be delayed in an asthmatic patient who is wheezing?
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If the patient does not always wheeze and their pulmonary status can be improved, then delaying the surgery would seem reasonable. There are some asthmatic patients who, in spite of the appropriate medications, always wheeze. There may be no benefit to delaying surgery in these patients.
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What makes midazolam particularly useful in the outpatient setting?
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It has a relatively short onset of action and an elimination half-life of 2-4h.
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What tole might oral clonidine play in the preoperative period?
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As an alpha-2 adrenergic agonist, it can reduce anesthetic requirements and has been used to provide sedation and anxiolysis while maintaining hemodynamic stability.
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Which local anesthetic produces toxicity at the lower dose?
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Tetracaine.
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By what mechanism does pulse oximetry provide accurate measurement of oxygen saturation?
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Pulse oximetry is based on Beer's law, which relates the concentration of a solute in suspension (in this case, hemoglobin) to the intensity of light transmitted through the solution.
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What is the definitive clinical test for complete reversal of neuromuscular blockade?
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The ability of the patient to sustain a head lift from the bed for 5 minutes.
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What is the standard endocarditis prophylaxis for dental, oral or upper airway procedures in adult patients at risk?
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Amoxicillin, 3gm orally, 1h before the procedure and 1.5gm 6h after the initial dose.
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What is the cause of most anesthetic-related deaths?
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Human error (50-75%).
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What are the most common problems associated with adverse anesthetic outcomes?
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Those related to the airway (i.e., inadequate ventilation, unrecognized esophageal intubation and unrecognized disconnection from the ventilator).
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How does the presence of an upper respiratory infection in an infant influence the perioperative risk of respiratory complications?
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Intubation results in edema and a greater reduction in cross-sectional area of the trachea.
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What is the best time to administer oral ranitidine for prophylaxis against acid aspiration?
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60min before induction of anesthesia
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What is the single most important factor predicting postoperative cardiac morbidity?
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History of CHF
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What PaO2 level does cause a significant change in oxygen saturation begin to occur?
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less than 80mmHg
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What factors increase the risk of perioperative cardiac complications?
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Greater than 5 premature ventricular contractions per minute, withdrawal of beta-blockers and topical nitrates, presence of CHF and known 3-vessel CAD.
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What is the principal anesthetic technique used in patients with significant pulmonary disease?
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Intubation at a deep level of anesthesia.
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What does end-tidal CO2 measurement reflect?
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Metabolism, circulation and ventilation.
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What is the mechanism of action of metoclopramide?
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It inhibits dopamine and enhances the release of acetylcholine, resulting in an increased rate of gastric emptying and increased LES tone. It also inhibits the chemoreceptor zone.
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What are the extrapyramidal effects of droperidol?
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Acute dystonia, parkinsonism and akathesia
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What is the single most important factor that determines the length of stay after general anesthesia in ambulatory patients?
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post-anesthesia nausea
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What are the advantages of propofol over volatile agents in pediatric ambulatory patients?
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Decreased postoperative nausea and vomiting and a decreased incidence of airway obstruction.
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How does neostigmine decrease postoperative nausea and vomiting?
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It increases LES pressure and counteracts the increased risk of regurgitation of gastric contents after atropine administration (which lowers LES).
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What are the advantages of oral midazolam over oral ketamine as a premedicant?
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Oral midazolam has a shorter recovery time and lower cost.
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What factors should the ideal premedication in children 1-6y of age possess?
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An atraumatic route of administration, rapid and reliable onset, minimal side effects and rapid elimination.
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What is a reliable alternative induction technique in a 5y/o struggling child who refuses the mask and cannot be managed by IV induction because of lack of accessible veins?
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A sedating intramuscualr injection of ketamine (3mg/kg)
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What are the most common anesthetic complications seen in the PACU?
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Nausea, vomiting and airway compromise.
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T/F: All local anesthetics are weak bases and produce vasodilation
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false. Cocaine is the exception.
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After an oral dose of midazolam, when is it appropriate to separate children from their parents?
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between 10 and 30 min
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What patients are best suited for oral ketamine?
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severely stressed and mentally handicapped individuals.
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How should the recovery phase of an ambulatory patient differ from that of an inpatient?
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It should be as brief as possible and be associated with minimal postanesthetic sequelae.
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What may result from an intra-arterial injection of thiopental?
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Crystal formation and local norepinephrine release that may culminate in thrombosis and severe ischemia of the extremity.
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What is the treatment for an intra-arterial injection of thiopental?
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Intravascular dilution and perivascular infiltration with local anesthetic, sympathetic block of the extremity and anticoagulation with heparin.
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How does the half-life of flumazenil compare to that of midazolam?
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the half-life of flumazenil is shorter
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What effect does etomidate have on the cardiovascular and respiratory systems?
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none
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What effects of ketamine discourage its use in patients with increased intracranial pressure?
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It causes sympathetic nervous system stimulation, with a rise in BP, HR and ICP.
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What factors determine cerebral blood flow?
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Arterial CO2 and O2 tension, systemic arterial BP, head position, jugular venous obstruction and PEEP.
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What are the cardiovascular effects of propofol?
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Cardiovascular depression, by a combination of direct myocardial effects and vasodilatation.
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What is the second gas effect of nitrous oxide?
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The ability of nitrous oxide to increase the uptake of other, more potent, inhaled agents.
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What is the most sensitive indicator of a falling cardiac output during surgery?
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Mixed venous oxygen tension will decrease.
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What anesthetic considerations must be taken into account in a patient with sickle cell disease?
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Adequate hydration and oxygenation. Spinal or local anesthesia should be used whenever possible.
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What are the advantages of nitrous oxide?
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It has a low solubility, is nonflammable, easy to administer and inexpensive.
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Among the currently available potent inhaled anesthetic agents, which ones have a pleasant odor and are not irritating to the airway?
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Halothane and sevoflurane.
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What anesthetic considerations must be taken into account in a patient with ascites?
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Ascites decreases the ventilation-perfusion ratio in the basilar sections of the lung, decreases diaphragmatic excursion, compresses the vena cava and increases the volume of distribution of anesthetic drugs.
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What effect does halothane have on the liver?
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Halothane undergoes significant metabolic degradation, generating compounds that may cause halothane-associated hepatic toxicity.
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What are the cardiovascular effects of isoflurane?
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Myocardial depression, decreased systemic vascular resistance and myocardial steal in patients with CAD.
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What patient population might have a decreased amount of pseudocholinesterase?
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Patients taking anticholinesterase medications for glaucoma or myasthenia gravis, chemotherapeutic drugs and patients with a genetically atypical enzyme.
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What are the adverse side effects of succinlycholine?
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Cardiac dysrhythmias, fasciculations, hyperkalemia, myalgia, myoglobinuria, increased pressures (ocular, gastric and cranial), trismus, allergic reactions and it is a trigger for malignant hyperthermia.
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What is the mechanism of action of nondepolarizing neuromuscular blocking agents?
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They combine with nicotinic cholinergic postjunctional receptors. However, they do not activate the receptor or directly block the channel.
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Which neuromuscular blocking agent might be best in an ambulatory patient with significant renal or liver disease?
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Atracurium. It undergoes spontaneous degration
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Which inhalational agent is the most offender in terms of sensitizing the myocardium to catecholamines?
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Halothane
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What are the limits of epinephrine injection when given for hemostasis?
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Clinically, epinephrine is limited to 2mcg/kg with isoflurane. Epinephrine concentrations greater than 1:100,000 increase the risk of ectopy without improving hemostasis.
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How is mivacurium metabolized?
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By plasma cholinesterease, at a rate approximately 70-88% that of succinylcholine. Prolonged recovery has been reported in patients homozygous for atypical pseudocholinesterase enzyme.
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Which nondepolarizing neuromuscular blocking agent might be best in an ambulatory patient who is particularly sensitive to blood pressure changes?
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vecuronium. It is the only neuromuscular blocking agent essentially devoid of cardiovascular side effects.
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Why is regional anesthesia associated with a lower incidence of deep venous thrombosis than general anesthesia?
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The maintenance of spontaneous ventilation.
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What effect does local infiltration of bupivacaine have on postoperative pain after laparoscopic tubal ligation?
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Mesosalpinx infiltration of 0.5% bupivacaine significantly lower pain intensity and need for postoperative narcotic analgesics.
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What regional nerve blocks can be performed to provide postoperative analgesia after inguinal hernia repair in children?
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Ilioinguinal and iliiohypogastric nerve blocks.
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What is an effective alternate analgesic to opioids in a 22y/o healthy female having a laparosocpic tubal ligation?
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Preoperative ketolorac.
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In terms of duration of action, how does a single dose of fentanyl (1mcg/kg IV) compare with a single dose of ibuprofen (800mg PO)?
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The therapeutic effects of a single dose of ibuprofen may last more than 4h, whereas fentanyl lasts no longer than 2h.
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What are the advantages of using propofol instead of thiopental for induction and/or maintenance in pediatric patients undergoing ambulatory surgery?
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Conintuous infusion of propofol is a well-tolerated anesthetic technique in children. The speed and quality of recovery after propofol are superior to that observed after thiopental and/or halothane administration and it is associated with an extremely low incidence of vomiting.
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What are the benefits of using sevoflurane over isoflurane in adult ambulatory surgical patients?
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Sevoflurane results in faster recovery and decreased side effects.
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What are the possible mechanisms for opioid-induced nausea and vomiting?
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Delayed gastric emptying, sensitization of the vestibular center and direct action at the chemoreceptor trigger zone.
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At what age are infants usually not bothered by separation anxiety?
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Less than 6 months of age.
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T/F: A child with congenital heart disease is not a candidate for ambulatory surgery.
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False. A child who has stable congenital heart disease and is being followed by a pediatrician or cardiologist may be an appropriate candidate for ambulatory surgery.
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What are the advantages of regional anesthesia?
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It bypasses many of the potential sources of minor or major morbidity associated with general anesthesia.
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What is the maximum dose of bupivacaine with epinephrine?
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3mg/kg
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Which local anesthetic offers the least likelihood of systemic toxicity when performing intravenous regional anesthesia?
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Prilocaine; due to its short plasma half-life.
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After performing an axillary block, why might the medial aspect of the upper arm occasionally by spared?
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If it is innervated by the intercostobrachial nerve (T2), which is not part of the brachial plexus. In many individuals, however, this area is primarily innervated by the medial cutaneous nerve o the arm that is part of the brachial plexus and can be anesthetized with an axillary block.
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What are the landmarks in performing a midline lumbar spinal block?
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The iliac crest and the L4 and L5 spinal processes (and/or L3 spinous process).
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What is the most feared toxicity of ketorlac?
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renal toxicity
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What indicates a subarachnoid or subdural injection while test-dosing an epidural with local anesthetic?
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The onset o significant anesthesia of more than 2 or 3 segments within 5 minutes of injection.
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At what level does the subarachnoid space terminate in children?
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The S2-3 or S3-S4 space.
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What is transient radicular irritation?
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Back pain with radiation down one or both buttocks or legs occurring within 24h after surgery.
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What is the best parameter in predicting successful weaning from mechanical ventilation?
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rapid shallow breathing index (RR/TV)
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What are the possible causes of TRI?
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Specific local anesthetic toxicity, needle trauma, neural ischemia and pooling of local anesthetics secondary to small-gauge pencil point needles.
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How would you determine a loading dose for a drug to reach an effective plasma concentration quickly?
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The loading dose is equal to the product of the desired plasma concentration and the volume of distribution.
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What signs and symptoms are associated with ionic contrast media administration?
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Flushing, tachycardia, nausea, volume contraction, high urine osmolality and nephropathy. True allergic reactions to the iodine may precipitate anaphylaxis requiring urgent treatment.
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What effects do magnetic fields have on pacemakers?
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The effects are variable. The magnetic fields may generate an internal electrical circuit that affects the pacemaker microcircuitry resulting in failure of normal output. There is also a possibility that the mode of the pacemaker may be switched (i.e., demand to asynchrony).
