what are the adjuncts in anaesthesia

Histamine receptor Antagonists

H₁Receptor Antagonists 

H1 antagonist also have antimuscarinic or antiserotonergic which can be used for a multitude of therapeutic purposes

• suppression of allergic symptoms, cough, nausea and vomiting.
• sedation

Used as premedicaton because of antiemetic and mild hypnotic 

They maintain the ventilatory drive during sedation and their sedative effects can potentiate other CNS depressants such as Benzodiazepines,barbiturates and opioids.

H₂ Receptor antagonists

• Reduce gastric acid output ad raise gastric pH
• As a premedication to reduce peri operative risk of aspiration pneumonia
• Dosage is at bedtime and again at least 2hr before in the morning of surgery
• Rapid iv injection rarely associated with hypotension and arrhythmia
• Mild dose reduction in signifiant kidney impairment as renal elimination
• Weak inhibitor of Cytochrome P-450 hence no significant drug interaction

Antacids

• Neutralize the gastric acidity by giving  base to react with hydrogen ion to form water
• Unlike H2 blockers have an immediate effect
• Present in 2 forms- Particulate and Non-Particulate
• Non particulate are widely used as less damaging to heart 
• Dosage is 0.3M solution of Sodium Citrate 15-30ml orally 30min prior to induction
• Drug interaction by alteration in gastric pH like slowing absorption and elimination of Digoxin,Rantidine whereas phenobarbital elimination s prolonged

Metoclopramide

It is a Prokinetic Drug and increases the Lower Esophageal Sphincter tone, speeds gastric emptying and lowers gastric fluid volume

• It is cholinomimetic at intestinal smooth muscles and dopamine antagonist in CNS
• It is a antiemetic 
• Rapid injection may cause abdominal cramping and hypertensive crisis with pheochromocytoma 
• Sedation, nervousness and extra pyramidal signs with dopamine antagonism
• Concurrent usage with phenothiazines can increase extrapyramidal S/E

Proton Pump Inhibitor

• Pantoprazole inhibit the secretion of hydrogen ions and reduce gastric volume 
• Dosage 40mg 2hr prior to induction 
• Interferes with P-450 enzymes and decreases the clearance of diazepam, warfarin and phenytoin
• Repeat doses with caution in severe liver impairment as liver elimination

5-HT₃ Receptor Antagonists

Ondansetron is a antiemetic  due to blocking of serotonin 5HT3receptors at CTZ 

• Effective antiemetic in post op nausea and vomiting
• Prophylaxix in high incidence of N/V in Laparoscopy Surgery, Neurosurgeries
• Can Slightly prolong QT interval in ECG
• Given either prior to induction or at the end of the surgery

NSAIDS

Ketorolac and Diclofenac provide analgesia by inhibiting prostaglandin synthesis

• alternative to opioids in post operative pain management as they do not cause sedation, respiratory depression or N/V
• Inhibit platelet aggregation and prolong bleeding time cautious use in post op haemorrhage
• Dose reduction in renal impairment 
• Contraindicated in patients allergic to aspirin and NSAIDS

Clonidine

Alpha adrenergic agonist which  decreases sympathetic activity, enhance parasympathetic tone and reduce catecholamines

• Used as anti hypertensive
• Adjunct to Local anaesthetic agents in Epidural anaesthesia 
• As a premedication 
• Side effects sedation, bradycardia, dizziness, dry mouth
• Dose reduction in renal impairment

Dexmedetomedine

• Alpha agonist with selective activity
• Dose dependent sedation,anxiolysis and some analgesia
• Opioid Sparing role with no significant respiratory depression
• Side effects are bradycardia hypotension