PREANAESTHETIC MEDICATION

By:Himani Manju Malhotra

2nd MBBSRoll no: 52

• What are pre-anaesthetic drugs?

• Why are pre-anaesthetic drugs given?

• What are the drugs whichare included in pre-anaesthetic

medication?

• When are these drugs given?

WHAT & WHYPreanaesthetic medication refers to the use of drug before

anaesthesia to make it more pleasant & safe.The aims are:1) To relieve anxiety.2) To provide haemodynamic stability.3) To induce sedation & reduce metabolic rate.4) To provide analgesia and amnesia.5) To decrease the chances of aspiration.6) To control oral &respiratory secretions.7) To prevent postoperative nausea and vomiting.8) To control infection.

PREANAESTHETIC MEDICATION

• Benzodiaze-pines like diazepam(5-10mg) & lorazepam(2mg oral or 0.05 mg/kg i.m. 1hour before), produce tranquility & smoothen induction. Diazepam is also centrally acting skeletal muscle relaxant.

• There is loss of recall of perioperative events with little respiratory depression or post operative vomiting. They counteract CNS toxicity of local anaesthetics & are being used along with pethidine/fentanyl for minor surgical and endoscopical procedures.

1-SEDATIVE-ANTIANXIETY DRUGS

2-OPIOIDS-TO PROVIDE ANALGESIA

• Earlier morphine was given, it showed disadvantage of-i. Respiratory depressantii. Causes peripheral vasodilatation responsible for

hypertension.iii. Shows anti-diuretic action.iv. Causes meiosis.• Use of opioids is now mostly restricted to those having

preoperative pain. When indicated, fentanyl is mostly injected i.v. just before induction.

• Given i.v. just before induction or i.m. 1 hour before surgery.

3-ANTICHOLINERGICS• Earlier Atropine was used, which is now replaced

by Glycopyrolate.Atropine showed the following advantages-i. Atropine prevents vasovagal shock.ii. It causes drying up of secretions making

intubation easy.iii. It increases heart rate.However, it showed CNS effects due to which it was

replaced by Glycopyrolate.

ACTION ATROPINE GLYCOPY-ROLATE

1-Antisecetory ++ +++

2-Tachcardia +++ ++

3-CNS effects + -

4-Bronchodilatation ++ ++

4-H2 BLOCKERS/PROTON PUMP INHIBITORS

• Rantidine(150mg) or omeprazole(20mg) or famotidine(20mg) are given night before and in the morning. They benefit by raising the pH of gastric juice & may also reduce its volume & thus chances of regurgitation. The chances of reflux & damage to lungs on aspiration (Mendelson’s syndrome) is minimal if volume of gastric juice is <25ml & pH is >3.5. prevention of stress ulcers is another advantage.

5-ANTIEMETICS

• Ondensetron (4-8mg) i.v. is selective 5-HT3 blocker has been found highly effective in reducing the incidence of post-anaesthetic nausea & vomiting. It is practically devoid of side-effects & has become antiemetic of choice in anaesthetic practice.

6-TO CONTROL INFECTIONS

• The timing of antibiotic should be adjusted so that peak blood kevels are achieved at the time of skin incision. Mostly, antibiotic is given i.v. 5-10 minutes before incision. If given orally, should be given 1-2 hours before the surgery.

7-TO DECREASE CHANCES OF ASPIRATION

Patient should be fasting for 8 hours for solid food & 3-4hours for clear fluids. Clear juices only inc water and juice without pulp, tea coffee are considered as unclear fluids so full fasting of 8 hours is needed.

FOR CHILDREN- 6-8 hours for solid food & 2-3 hours for clear fluids is sufficient.

FOR INFANTS(on milk)-fasting for 4 hours for milk & 2hours for water is sufficient.

THANKYOU!