Pre-Anaesthetic Medication

Pre-anaesthetic Medication: 

Pre-anaesthetic Medication Dr. M. Khurram Mahmood

Slide 4: 

Anaesthesia Loss of sensation

General Anaesthetics: 

General Anaesthetics General anaesthetics are the drugs used to produce general anaesthesia resulting in loss of all modalities of sensation, particularly pain, alongwith controlled reversible loss of consciousness, adequate muscular relaxation and loss of reflex activity to carry out operative procedures safely on a patient

Slide 6: 

The goal of general anesthesia is to create a reversible condition of comfort, quiescence, and physiological stability before, during, and after a surgical procedure

Local Anaesthetics: 

Local Anaesthetics Local anaesthetics as distinguished from general anaesthetics as they abolish the pain and other sensations in localized areas without affecting the degree of consciousness of the patient

Anaesthesia requirements: 

Anaesthesia requirements loss of all modalities of sensation, particularly pain controlled reversible loss of consciousness adequate muscular relaxation loss of reflex activity GAs are not safer drugs (resp & cardiac depression)

Definition – Pre-anaesthetic Medication: 

Definition – Pre-anaesthetic Medication Use of the drugs prior to the administration of a general anaesthetic agent, with the important object of making anaesthesia safer & more agreeable to the patient

OBJECTIVES Pre-anaesthetic Medication: 

OBJECTIVES Pre-anaesthetic Medication Sedation - anxiety & apprehension Relief of Pre-operative & Post-operative Pain Inhibition of Parasympathetic NS: (i) To decrease salivary & bronchial secretions prevent reflex laryngospasm (ii) To prevent cardiac arrest due to vagal stimulation (Halothane)

OBJECTIVES Pre-anaesthetic Medication…: 

OBJECTIVES Pre-anaesthetic Medication… d. Synergic effect with GAs smooth & rapid induction with reduced GA dose e. Anti-emetic effect f. To decrease gastric acid secretion g. To counteract certain adverse effects of the anaesthetic agents

OBJECTIVES Pre-anaesthetic Medication…: 

OBJECTIVES Pre-anaesthetic Medication… No drug can achieve all these objectives combination of drugs used

Drugs used to achieve these objectives: 

Drugs used to achieve these objectives Sedatives / Anxiolytics Opioid Analgesics Anticholinergic Drugs Antiemetics Other Drugs

CLASSIFICATION – Pre-anaesthetic Medication : 

CLASSIFICATION – Pre-anaesthetic Medication Sedatives / Anxiolytics Benzodiazepines Barbiturates Butyrophenones Phenothiazines Chloral hydrate & Paraldehyde Opioid Analgesics Morphine Pethidine Buprenorphine

CLASSIFICATION – Pre-anaesthetic Medication : 

CLASSIFICATION – Pre-anaesthetic Medication Anticholinergic Drugs Atropine SO 4 Scopolamine (Hyoscine) Synthetic Anticholinergics – Glycopyrrolate Antiemetics Phenothiazins (Promethazine and Trimeprazine) Cyclizine Trimethobenzamide Benzquinamide Metoclopramide

CLASSIFICATION – Pre-anaesthetic Medication : 

CLASSIFICATION – Pre-anaesthetic Medication Other Drugs Antibiotics H 2 Receptor Antagonists, Gastric Antacids & Omeprazole Other drugs for special problems

Sedatives / Anxiolytics …. anxiety & apprehension : 

Sedatives / Anxiolytics …. anxiety & apprehension Benzodiazepines Barbiturates Butyrophenones Phenothiazines Chloral hydrate & Paraldehyde

Sedatives / Anxiolytics …. anxiety & apprehension: 

Sedatives / Anxiolytics …. anxiety & apprehension Benzodiazepines Most widely used Safety, muscle relaxant & less respiratory depression & amnesic effect Useful for pt as well for the facilitation of anesthetic state Diazepam Most widely used – 5 to 10mg orally or parenterally Nitrazepam, Lorazepam, Midazolam

Sedatives / Anxiolytics …. anxiety & apprehension: 

Phenothiazines Antipsychotic drugs Possess sedative, antiarrhythmic, antiemetic & antihistaminic properties MOA : blockade of D 2 receptors, other effects (blockade of alpha adrenoceptors, hitaminic (H 1 ) & 5-HT 2 receptors) Adverse effects : Potentiate the effects of barbiturates & morphine  respiratory depression & arterial hypotension Promethazine & trimeprazine (H 1 antagonists) are commonly employed Sedatives / Anxiolytics …. anxiety & apprehension

Sedatives / Anxiolytics …. anxiety & apprehension: 

Sedatives / Anxiolytics …. anxiety & apprehension Butyrophenones Antipsychotic drugs Droperidol & Haloperidol Similar actions like phenothiazine Barbiturates Low Therapeutic Index Potent Enzyme Inducers : Drug Interactions Risk of Physical Dependence Severe withdrawal Syndrome

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain : 

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain Commonly employed drugs Morphine (10 – 15mg IM) Pethidine (50 – 100mg IM) Buprenorphine (0.3mg IM)

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain: 

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain Have sedative & analgesic properties Buprenorphine has longer DOA than Morphine & Pethidine  the amount of GA required Needed whenever there is existing pain or as an supplement to an anesthetic agent Can be given before or at end of operation – without waiting for the pt to complain of pain

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain: 

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain Disadvantages Depress respiration  resp arrest Morphine the tone of smooth muscle such as bronchial muscles  worsen the condition of pt having pulmonary insufficiency (emphysema , kyphoscoliosis) Cause vasomotor depression, they  the ability of circulation to respond to stress, often delays awakening

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain: 

Opioid Analgesics- Relief of Pre-operative & Post-operative Pain Disadvantages Morphine – induces vomiting & has an antidiueretic effect Morphine – interfere with pupillary reactions, stages of anesthesia cannot be distinguished Pethidine – produce tachycardia by its vagolytic action Morphine & Pethidine are histamine liberators

Anticholinergic Drugs- Inhibition of Parasympathetic NS: 

Anticholinergic Drugs- Inhibition of Parasympathetic NS Bronchial & salivary secretions can collect in the lungs and can predispose the pt infection & reflex laryngospasm Atropine SO 4 - an hr before operation (I/V or I/M-0.6 mg) Scopolamine (Hyoscine) - generally combined with morphine to block the vagal actions

Anticholinergic Drugs- Inhibition of Parasympathetic NS: 

Anticholinergic Drugs- Inhibition of Parasympathetic NS  salivary & resp secretions and also prevent reflex parasympathetically induced hypotension, bradycardia, reflex laryngospasm and even cardiac arrest (Lessen the possibility of cardiac arrhythmias during the induction stage) due to blockade of cardiac vagal action tachycardia

Anticholinergic Drugs- Inhibition of Parasympathetic NS: 

Anticholinergic Drugs- Inhibition of Parasympathetic NS Synthetic Anticholinergics – Glycopyrrolate Long acting quaternary amine Less central actions Less tendency to cause excessive tachycardia preferred

Antiemetics – Anti-emetic effect: 

Antiemetics – Anti-emetic effect Phenothiazines such as Promethazine and Trimeprazine  help to prevent post operative N & V (central dopaminergic blockade & antimuscarinic effects) Other drugs such as Cyclizine (antihistaminic effect) 50 mg, Trimethobenzamide 200mg ( Substituted Benzamide Antiemetic like Metoclopramide, possesses D 2 Antagonist & mild anti- histaminic activity) Benzquinamide 25 – 50 mg (dopaminergic receptor blockade)

Antiemetics – Anti-emetic effect: 

Antiemetics – Anti-emetic effect Metoclopramide – dual MOA As Antiemetic It has potent Antiemetic & antinausea effect Blocks D 2 receptors in CTZ of the medulla (area postrema) As Prokinetic agent It can selectively stimulate gut motor function Blocks D 2 receptor in GIT & blocks the normal inhibitory effect of Dopamine on cholinergic smooth muscle stimulation--- ↑ motility.

Other Drugs: 

Other Drugs Antibiotics (Cephalosporins) H 2 Receptor Antagonists (Ranitidine)and Gastric Antacids (sodium citrate) PPIs (Omeprazole). to prevent acid aspiration pneumonitis and Mendelson’s syndrome

Other Drugs: 

Other Drugs drugs for special problems such as Chronic Lung Diseases, Emphysema, Chronic Heart Diseases, Diabetes Mellitus, Hypertension, Under nutrition, debilitated & old people

Preanesthetic Agents: 

Preanesthetic Agents Drug Classification Generic Name Desired Effect Benzodiazepines Diazepam Midazolam Reduce anxiety, Sedation, Amnesia, “Conscious sedation” Antihistamines Hydroxyzine Sedation Opioid analgesics Morphine Meperidine Fentanyl Remifentanil Sedation to decrease tension, anxiety, and provide analgesia Phenothiazines Promethazine Sedation, antihistaminic, antiemetic, decreased motor activity Anticholinergics Atropine Glycopyrollate Inhibit secretion, bradycardia, vomiting, and laryngospasms GI Drugs Ondansetron Cimetidine Metoclopramide Antiemetic Decrease gastric acidity Decrease stomach contents

Preanesthetics: 

Preanesthetics Preanesthetic medications – drugs given generally prior to anesthesia (may be given during or after, as well) in order to: Decrease anxiety without producing excessive drowsiness Facilitate a rapid, smooth induction without prolonging emergence Provide amnesia for the perioperative period Relieve pre-and post-operative pain Minimize undesirable side effects of anesthetics