Adjuncts to Anesthesia

Herwin B. Bautista, M.D.Department of Anesthesia

H1 – Receptor Antagonists

Mechanism of action

Antimuscarinic or atropine likeAntiserotinergic (antiemetic)

Clinical use Suppression of allergic symptomsSedation, antiemesisBlocks bronchoconstriction

Dosage 25-50 mg oral, IM, or IV

Drug interactions Potentiates other CNS depressants(opioids, barbiturates)

H2 – Receptor Antagonists

Mechanism of action

Reducing gastric outputRaising gastric pH

Clinical use Treatment of peptic doudenal and gastric ulcer, GERD, Zollinger-Ellison syndrom

Dosage Bedtime then 2 hours prior to surgery as premedication

Drug interactions Cimetidine reduces hepatic blood flow and binds to cytochrome P-450

Antacids

Mechanism of action

Neutralizes gastric acidity

Clinical use Treatment of gastric and doudenal and gastric ulcer, GERD, Zollinger-Ellison symdrom

Dosage 15-30 ml sodium or potassium citrate 15-30 mins. prior to induction

Drug interactions Changes in the absorption and elimination of digoxin, cimetidine, and ranitidine

Metoclopramide

Mechanism of action

Dopamine antagonistProkinetic in the upper GI tract

Clinical use Speeds gastric emptying timeTreatment of diabetic gastroparesisPatient with risk of aspiration pneumonia

Dosage 10-20 mg oral, IM, or IV

Drug interactions Antimuscarinic drugs blocks GI effects of metoclopramide

Proton Pump Inhibitors

Mechanism of action

Binds to proton pump of parietal cells in gastric mucosa –inhibit secretion of hydrogen ion

Clinical use 20-40 mgs oral or IV

Dosage Omeprazole interferes with P-450 and decrease clearance of diazepam, warfarin and phenytoin

Drug interactions

5-HT3 Receptor Antagonists

Mechanism of action

Antiemesis with no effect in GI motility

Clinical use Postoperative vomitingPost-chemotherapy vomiting

Dosage Ondansetron 4 mg IVDolasetron 12.5 mg IV

Drug interactions No significant drug interactions

Ketorolac

Mechanism of action

NSAID for analgesia by inhibiting prostaglandin synthesis

Clinical use Postoperative pain management

Dosage 30-60 mg IM15-30 mg IV

Drug interactions Aspirin decreases protein binding Decreases postoperative opioid requirement

Doxapram

Mechanism of action

Peripheral and central nervou system stimulantCentral respiratory centers stimulant

Clinical use Treatment for drug induced respiratory depression

Dosage 0.5-1 mg/kg IV bolus

Drug interactions Exaggerate the CVS effects of MAO inhibitors

Naloxone

Mechanism of action

Competitive antagonist at opioid receptors

Clinical use Reversal of opioid induced respiratory depression

Dosage 0.5-1 ug/kg every 3-5 mins. until reversal is achieved

Drug interactions Naloxone may antagonize the antihypertensive effect of clonidine

Flumazenil

Mechanism of action

Specific and competitive of benzodiazepines

Clinical use Reversal of benzodiazepine sedation and overdosage

Dosage 0.2 mg IV every minute till reversal is achieved