Premedication and Drugs Used for Premedication

To reduce anxiety and fear in patients before surgery, the following approaches and medications can be considered:

1. Preoperative Visit: Establish rapport with the patient, discuss their concerns, and provide reassurance.

2. Benzodiazepines: These are ideal agents for reducing anxiety and providing relief. They also offer anterograde amnesia and light sedation. Benzodiazepines are typically administered orally 1-2 hours before surgery. Some examples include:

   • Diazepam
   • Lorazepam
   • Temazepam (preferred for day-case)
   • Midazolam (associated with shorter recovery time)

   Benzodiazepines generally have minimal effects on cardio-respiratory function. However, diazepam is not recommended for children. In children, oral antihistamines can be used as an alternative.

3. Clonidine: Clonidine can also be used for sedation, either orally or intravenously.

4. Dexmedetomidine: Dexmedetomidine is another sedative with anxiolytic and analgesic properties. It is considered effective, particularly in children, and can be used as an alternative to benzodiazepines.

5. Opioids: Medications like morphine and pethidine can also help relieve anxiety and provide sedation.

1. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): NSAIDs are commonly used, especially in day surgery, unless contraindicated.

2. Paracetamol: Paracetamol is a useful medication for pain relief and can help reduce the required dose of anaesthetic agents.

3. Opioids: Opioids are the drugs of choice for acute pain relief. They can cause variable sedation, cardio-respiratory depression, nausea, and vomiting. Be aware that morphine may precipitate bronchospasm.

4. Clonidine: Clonidine has both analgesic and sedative effects and can be considered for pain management.

Managing airway secretions is essential during surgery. Here are some considerations and medications:

• Older Agents and secretions: Ether and cyclopropane are older agents that can stimulate the production of airway secretions, unlike modern agents like halothane.

• Anticholinergics: Medications like atropine, hyoscine, and glycopyrrolate can help reduce airway secretions. However, they are not routinely used today because modern agents typically do not produce significant secretions.

• Ketamine: Ketamine tends to promote airway secretions.

• Enhance the hypnotic effects of anesthetics through sedation using barbiturates, opioids, or benzodiazepines.
• Using these agents for premedication can reduce the dose of general anesthetics required and mitigate their side effects.

• Useful in young patients or those undergoing repeated general anesthesia.
• May allow a lighter plane of anesthesia by reducing the risk of awareness during surgery.
• The most effective agents for promoting amnesia are the benzodiazepines, such as lorazepam and midazolam.

• Essential to improve patient comfort after surgery.
• Use antiemetics to counteract the effects of anesthetic agents.
• Common antiemetics include ondansetron, dexamethasone, droperidol, metoclopramide, and perphenazine.
• Some of these medications may have disadvantages, such as high cost and the potential for causing orthostatic hypotension.

Patients with a risk of regurgitation or vomiting of gastric contents or those undergoing procedures with a high incidence of nausea and vomiting (such as laparoscopy) should receive agents to reduce gastric volume and acidity. This is particularly important in 'full stomach cases,' including emergency cases and all cesarean section (C/S) cases.

The agents used for this purpose include:

• H2-receptor blockers like ranitidine, which reduce acid secretion and gastric volume.
• Gastrokinetic agents like metoclopramide, which hasten gastric emptying.
• Proton pump inhibitor omeprazole.
• Antacid (non-particulate) like 0.3 molar sodium citrate, 30 ml, which neutralizes gastric acid. Because it is non-particulate, it does not cause further lung damage if aspiration occurs.

Vagal reflexes that can lead to bradyarrhythmia or even cardiac arrest may occur in certain situations, such as during ophthalmic surgery (due to traction on eye muscles) or with repeated administration of suxamethonium, or during induction of anesthesia with halothane.

These reflexes can be attenuated by premedication with anticholinergic agents, including:

• Atropine
• Hyoscine
• Glycopyrrolate

During the induction of anesthesia, laryngoscopy and tracheal intubation often trigger marked sympatho-adrenal activity, resulting in responses like tachycardia, hypertension, and increased catecholamine concentrations. While these responses can be undesirable in healthy individuals, they can be harmful in patients with conditions like hypertension or ischaemic heart disease.

To mitigate this vasopressor or laryngopressor hemodynamic response, the following agents can be used:

• β-blockers (e.g., propranolol as premedication)
• Esmolol
• Magnesium sulfate
• Opioids (e.g., fentanyl)
• Calcium channel blockers
• Lidocaine

• Naturally occurring, derived from poppy seeds.
• Used for premedication and analgesia.
• Undergoes significant first-pass effect when given orally.
• CNS Effects:
  • Causes anxiety and euphoria.
  • Depresses the respiratory center.
  • Reduces pain sensation and metabolic rate.
  • Stimulates the chemoreceptor trigger zone (causing nausea and vomiting).
  • Stimulates the oculomotor nerve, causing miosis (constricted pupils).
• Respiratory System:
  • Causes histamine release leading to bronchoconstriction (contraindicated in asthma).
• Gastrointestinal Tract:
  • Causes constipation and delayed gastric emptying.
• Dosage: 0.1-0.15 mg/kg body weight intramuscularly (im) or intravenously (iv).
• Duration of action: 4-5 hours.

• Synthetic opioid analgesic.
• One-tenth as potent as morphine.
• 60% protein bound.
• Hepatic metabolism results in an active metabolite, norpethidine.
• Has similar effects as morphine.
• Has anticholinergic effects.
• High doses may cause convulsions and myocardial depression.
• Dosage: 1 mg/kg body weight.
• Duration of action: 2-4 hours.

• Produce anterograde amnesia, anxiolysis, minimal sedative effects.
• Also have anticonvulsant properties.
• They act by enhancing GABA-mediated inhibition in the CNS.
• Diazepam acts by depressing the limbic system to relieve tension and anxiety. It produces anterograde amnesia for events occurring shortly before injection.
• Diazepam has minimal CVS effects. Used to reduce hallucinations of ketamine analgesia & to produce basal analgesia in regional anaesthetic techniques.
• Metabolism produces active metabolites with long half-lives. Some benzodiazepines have no active metabolites: midazolam (only water-soluble benzodiazepine), temazepam, and lorazepam.

• Centrally acting drugs which produce a state of detachment from the environment & inhibit purposeful movement.
• Have α-blocking & antiemetic effects e.g. Droperidol and haloperidol.
• Droperidol has a faster onset of action and a shorter half-life and is useful in anaesthesia.
• Droperidol is given in combination with fentanyl to produce neuroleptanalgesia (awake analgesia). Combination of butyrophenone, opioid, N2O produces neuroleptanaesthesia characterised by profound analgesia, sedation, antiemesis, cardiovascular stability.

• Anticholinergic agent, inhibits all the muscarinic actions of acetylcholine.
• Tertiary ammonium compound crossing the blood-brain barrier to cause central effect (excitation).
• CVS. Tachycardia (initially bradycardia), cutaneous vasodilatation.
• CNS. Excitement, hallucination, and hyperthermia especially in children.
• RS. Bronchodilatation, reduced secretions, and increased dead space.
• GIT. Reduces salivation, lower esophageal sphincter tone, and motility.
• Other effects: ↓sweating and mydriasis. Should not be used in pyrexic patients.
• Dosage: 0.3-0.6 mg for premedication, 0.01-0.02 mg/kg in children.
• Dose for reversal of neuromuscular blockade with anticholinesterase inhibitor is 0.02 mg/kg.
• Dose recommended for peri-arrest arrhythmias to block vagus completely is 3 mg.

• Tertiary ammonium compound like atropine, crossing the blood-brain barrier with central effects (sedation).
• Has greater sedative, antiemetic, and antisialogogue effects than atropine.
• Has less action on the heart (less tachycardia) and bronchial muscle (less bronchodilator effect).
• CNS. Depresses CNS causing drowsiness, amnesia. Not a central stimulant like atropine.
• Causes restlessness and excitement especially in old patients leading to confusion/excitement, hence it is best avoided in the elderly.
• Dose: 4 µg/kg

• Quaternary ammonium compound - has minimal central effects.
• Causes less tachycardia than atropine.
• Reduces salivary, sweat gland activity more than atropine.
• Acts longer than atropine.
• Dosage: 4-5 µg/kg, im/iv. Dose for reversal of neuromuscular blockade with anticholinesterase inhibitors is 10-15 µg/kg.