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Chapter: Modern Medical Toxicology: General Principles: General Management of Poisoning

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Stabilisation: Management - General Management of Poisoning

– Respiratory insufficiency – Circulatory Failure – Cardiac Arrhythmias – CNS Depression

MANAGEMENT

Respiratory insufficiency

First establish an open airway:

·              Remove dentures (if any).

·              Use the chin lift and jaw thrust, to clear the airway obstructed by the tongue falling back.

·              Remove saliva, vomitus, blood, etc. from the oral cavity by suction or finger-sweep method.

·              Place the patient in a semi-prone (lateral) position.

·              If required, insert an endotracheal tube.

·              If ventilation is not adequate, begin artificial respiration with Ambu bag.

Oxygen therapy:

This is done to raise the PaO2 to at least 45–55 mmHg (6.0 Kpa to 7.3 Kpa). Begin with 28% oxygen mask. Depending on the response as assessed by periodic arterial gas analysis, either continue with 28% or progress to 35%. If the condition is relentlessly deteriorating, consider assisted ventilation.

Circulatory Failure

·              Correct acidaemia, if present.

·              Elevate foot end of the bed (Trendelenberg position).

·              Insert a large bore peripheral IV line (16 gauge or larger), and administer a fluid challenge of 200 ml of saline (10 ml/kg in children). Observe for improvement in blood pressure over 10 minutes. Repeat the fluid bolus if BP fails to normalise and assess for signs of fluid overload.* Haemodynamic monitoring should be considered in those adult patients who do not respond to 2 litres of infusion and short-term low-dose

·              vasopressors such as dopamine and noradrenaline. Obtain an ECG in hypotensive patients and note rate,

·              rhythm, arrhythmias, and conduction delays.** In patients, who do not respond to initial fluid challenges, monitor central venous pressure and hourly urinary output. Patients with severe hypotension may need more sophisti- cated haemodynamic monitoring (pulmonary artery cath- cated haemodynamic monitoring (pulmonary artery cath- eter and intra-arterial pressure monitoring).

·              Vasopressors of choice include dopamine and norepineph- rine. The doses are as follows:

o     Dopamine: Add 200 mg (1 ampoule usually), to 250 ml of 5% dextrose in water to make a solution of 800 micrograms/ml. Begin with 1 to 5 micrograms/kg/ min (maximum being 15 to 30 micrograms/kg/min), and titrate the dose to maintain systolic BP between 90 and 100 mmHg. Monitor BP every 15 minutes.

o     Noradrenaline: Add 8 mg (2 ampoules usually) to 500 ml of 5% dextrose solution to make a concentration of 16 micrograms/ml. Start at 0.5 to 1 ml/min and titrateto a clinical response. Monitor BP every 5–10 minutes until a clear trend is established.

Cardiac Arrhythmias

·              Obtain an ECG, institute continuous cardiac monitoring and administer oxygen.

·              Evaluate for hypoxia, acidosis, and electrolyte disturbances (especially hypokalaemia, hypocalcaemia, and hypomag- nesaemia).

·              Lignocaine and amiodarone are generally first line agents for stable monomorphic ventricular tachycardia, particularly in patients with underlying impaired cardiac function. Sotalol is an alternative for stable monomorphic ventricular tachy- cardia. Amiodarone and sotalol should be used with caution if a substance that prolongs the QT interval and/or causes torsades de pointes is involved in the overdose.

·              Unstable rhythms require cardioversion.

·              Atropine may be used when severe bradycardia is present and PVCs are thought to represent an escape complex.

Lignocaine:

––  Dose -

--  Adult: 1 to 1.5 mg/kg IV push. For refractory VT/VF an additional bolus of 0.5 to 0.75 mg/kg can be given over 3 to 5 minutes. Total dose should not exceed 3 mg/kg or more than 200 to 300 mg during a one hour period. Once circulation has been restored begin maintenance infusion of 1 to 4 mg per minute. If arrhythmias recur during infusion repeat 0.5 mg/kg bolus and increase the infusion rate incrementally (up to a maximum of 4 mg/minute).

Child: 1 mg/kg initial bolus IV; followed by a continuous infusion of 20 to 50 micrograms/ kg/minute.

Lignocaine Preparation:

- Add 1 gm of lignocaine to 250 ml of dextrose  5% in water, to make a 4 mg/ml solution. An increase in the infusion rate of 1 ml/minute increases the dose by 4 mg/minute.

CNS Depression

Till recently it was recommended that in every case where the identity of the poison was not known, the following three antidotes (called the Coma Cocktail) must be administered (intravenously):

·              Dextrose—100 ml of 50% solution

·              Thiamine (Vitamin B )—100 mg

·              Naloxone—2 mg

The rationale for the coma cocktail was that since a significant proportion of poisoned comatose patients in whom the identity of the poison was unknown comprise cases of overdose from opiates, alcohol, and hypoglycaemic agents, these drugs would work in such cases to at least indicate the possible diagnosis. Even if a particular case was not due to any of these causes, administration of these antidotes was considered relatively harmless. However, there is an increasing dissatisfaction among toxicologists with regard to the true dissatisfaction among toxicologists with regard to the true that it has no place in practice.

All patients with depressed mental status should receive 100% oxygen in a mask, (high flow—8 to 10 litres/min).


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