VASOPRESSORS These are mostly sympathomimetic drugs The sympathetic

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VASOPRESSORS

VASOPRESSORS

 • These are mostly sympathomimetic drugs. The sympathetic nervous system causes vasoconstriction of

• These are mostly sympathomimetic drugs. The sympathetic nervous system causes vasoconstriction of the skin and splanchnic vessels (stimulation of “alpha” receptors). Also stimulates heart, that is increases the force of contraction and the rate of the heart (stimulation of “beta”receptors). • Some vasopressors act by stimulating the “alpha” receptors causing peripheral vasoconstriction) thus increasing the venous return and raising the BP. Others act on the heart, that is on “beta”RECEPTORS AND RAISE THE BP.

ADRENALINE (Epinephrine) • Available for IV, IM and S/C injection. – 1: 1000 (1

ADRENALINE (Epinephrine) • Available for IV, IM and S/C injection. – 1: 1000 (1 mg/ml) & – 1: 10, 000 (1 mg/10 ml) Uses & mode of action: Resuscitation of seriously ill patients Treatment of anaphylactick shock Treatment of hypotension intra-operatively As an additive to LA to prolong duration Acts on alpha 1, beta 1 and beta 2 receptors. Dose: Bolus 100 microgm – IV depending on the patient’s condition. Some may require a continuous infusion (2 -20 microgm/min) with careful monitoring. During resuscitation from cardiac arrest the injection can be given directly into the heart or down the lumen of an endotracheal tube if there is no venous access.

 • Systemic effects: • CVS: Increase in heart rate and force of cardiac

• Systemic effects: • CVS: Increase in heart rate and force of cardiac contraction. Increase in systolic BP. • RS: Relaxes bronchial smooth muscle causing bronchodilatation. • Side effects: • Ventricular arrhythmias • Hypertension • May cause arrhythmias during anaesthesia with halothane.

EPHEDRINE • Available for IM and IV injection in concentrations of 30 mg/ml and

EPHEDRINE • Available for IM and IV injection in concentrations of 30 mg/ml and 50 mg/ml. • Uses and mode of action: • Treatment of hypotension due to vasodilatation e. g. after spinal or epidural. • Ephedrine acts on alpha 1, beta 1 and 2 receptors and mainly causes a rise in heart rate and BP. • Dose: 3 -10 mg IV as a bolus- may require to be repeated. • Duration of action: 5 -15 mins. • Side effects: • Tachycardia • Hypertension • Arrhythmias during halothane anaesthesia.

METRAMINOL (Aramine) • Available for IV, IM or S/C injection or IV infusion in

METRAMINOL (Aramine) • Available for IV, IM or S/C injection or IV infusion in concentration of 10 mg/ml • Uses and mode of action • Acts on alpha 1 receptors • Increases BP and cardiac output • Treatment of hypotension following spinal. • Dose: 1 mg bolus IV • 1 -20 mg/hour by IV infusion

ISOPRENALINE • • • Available for IV and IM injection. Uses and mode of

ISOPRENALINE • • • Available for IV and IM injection. Uses and mode of action Acts on beta 1 and beta 2 receptors Causes an increase in force of contraction and heart rate. Used for treatment of complete heart block or severe bradycardia. Dose: 5 -20 micrograms bolus 0. 5 -10 micrograms/min by infusion Side effects: May cause tachycardia and ventricular arrhythmias. May worsen coronary perfusion in ischaemic heart disease.