Review of Pharmacology - 9E (2015)

Review of Pharmacology
87. Ans. (a) ACE inhibitors (Ref: CMDT 2014/45-47)
• All antihypertensives should be continued in peri-operative period except ACE inhibitors, Angiotensin receptor
blockers and diuretics. ACE inhibitors and ARBs should be stopped 24 hours before surgery to prevent intraoperative
hypotension. Diuretics should be stopped once the patient is kept NPO (Nil per oral) to prevent intraoperative
volume depletion and electrolyte abnormalities.
• Statins should be continued if the patient is taking them, especially because preoperative withdrawal has been associated
with a 4.6-fold increase in troponin release and a 7.5-fold increased risk of myocardial infarction (MI) and
cardiovascular death following major vascular surgery.
• Corticosteroid therapy in excess of prednisone 5 mg/day or equivalent for more than five days in the 30 days preceding
surgery might predispose patients to acute adrenal insufficiency in the perioperative period. Surgical procedures
typically result in cortisol release of 50-150 mg/day, which returns to baseline within 48 hours. Therefore, the recommendation
is to continue a patient’s baseline steroid dose and supplement it with stress-dose steroids tailored to the
severity of operative stress.
Anaesthesia
General principles are
• Perioperative medication use should be tailored for each patient.
• Medications should be continued to avoid perioperative disease decompensation and withdrawal.
• Medications that interact with anesthesia or increase the risk of perioperative complications might need to
be stopped.
• Stop ACEI/ARB 24 hours before surgery.
• Stop diuretics once NPO.
• Continue statins.
• Continue CNS-active drugs.
• Insulin may require adjustment.
• Stop metformin 24 hours before surgery.
• Stop sulfonylureas the night before surgery.
• Stop OCPs and HRT four weeks before surgery, if possible.
• Stop nonselective NSAIDs two to three days before surgery, but continue COX-2 inhibitors.
• Continue outpatient dosing of corticosteroids and add a stress dose.
• Stop DMARDs and biologics one week before surgery.
• Stop herbal medicines one to two weeks before surgery.
88. Ans. (a) Slow induction and recovery (Ref: Goodman and Gilman 12/e p547-548)
Xenon is very close to the ‘ideal agent’.
Advantages of Xenon Anesthesia
• Inert (probably nontoxic to liver and kidney with no metabolism)
• Minimal effect on CVS function
• Lowest blood solubility (Lowest blood gas partition coefficient) therefore rapid induction and recovery.
• Does not trigger malignant hyperthermia
• Environmental friendly
• Non-explosive.
89. Ans. (b) Ketamine (Ref: Katzung 11/e p437)
Ketamine increases all pressures (blood pressure, intracranial tension, intraocular pressure) in the body. It is therefore
intravenous anaesthetic of choice for shock and should be avoided in hypertensive patients (increases blood pressure).
Further it is contraindicated in glaucoma (increases IOP) and head injuries (increases ICT).
90. Ans. (c) Intravenous Regional Anaesthesia (Ref: Short textbook of Anaesthesia by Ajay Yadav 2/e p148)
Prevention of conditions that favor sickling is the basis of peri-operative management.
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• Supplemental oxygen is recommended during and after regional anaesthesia/GA.
• Circulatory stasis can be prevented with hydration and anticipation of intraoperative blood loss in order to
avoid acute hypovolemia
• Normothermia is desirable because hyperthermia increases the rate of gel formation, and hypothermia produces
vasoconstriction that impairs organ blood flow.
• The use of a tourniquet and hence Bier’s block (intravenous regional anaesthesia) is contraindicated because
blood stasis can cause local acidosis, hypoxia with sickling of cells.
• Drugs commonly used for anaesthesia should not have significant effects on the sickling process.
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