A young female on antidepressants presents to the emergency with altered sensorium and hypotension, ECG reveals wide QRS complexes and right axis deviation. Next best step for the management of this patient:
Ans. a. Sodium bicarbonate (Ref: Harrison 19/e p172)A young female on antidepressants presents to the emergency with altered sensorium and hypotension. ECG reveals wide QRS complexes and right axis deviation. The clinical features and ECG findings typically suggest a diagnosis of tricyclic antidepressant poisoning. Antidote for TCA poisoning is sodium bicarbonate administered IV100 mEq (1--2 mEq/kg), and repeated every few minutes until BP improves and QRS complexes begin to narrow. Hemodialysis should not be used since TCAs are highly protein-bound with large volume of distribution.Tricyclic Antidepressant OverdoseTCA overdose is caused by excessive use or overdose of a TCA drug.It is a commonly used antidepressant & in children prescribed for bed-wettingQPathophzysiology:Most of the toxic effects of TCAs are caused by four major pharmacological effects:Anticholinergic effectsQExcessive blockade of norepinephrine reuptake at the preganglionic synapseQDirect alpha adrenergic blockadeQBlock sodium membrane channels with slowing of membrane depolarization, thus having quinidine-like effects on the myocardiumSigns and Symptoms:Peripheral ANS, CNS & heart are the main systems that are affected following overdose.Initial or mild symptoms typically develop within 2 hours and include tachycardia, drowsiness, a dry mouth, nausea & vomiting, urinary retention, confusion, agitation & headacheQ.More severe complications include hypotension, cardiac rhythm disturbances, hallucinations & seizuresQ.CCG abnormalities are frequent: MC is sinus tachycardia & intraventricular conduction delay resulting in prolongation of the QRS complex & PR/QT intervalsQ.Seizures, cardiac dysrhythmias & apnea are the most important life-threatening complicationsQ.TreatmentInitial treatment: Gastric decontaminationQ of the patient.This is achieved by administering activated charcoal lavage, which adsorbs the drug in the GIT either orally or via a nasogastric tube. Activated charcoal is most useful if given within 1-2 hours of ingestionQ.Other decontamination methods, such as stomach pumps, ipecac- induced emesis, or whole bowel irrigation are not recommended in TCA poisoningQ.Supportive therapy is given if necessary, including respiratory assistance, maintenance of body temperature, etc.Administration of IV sodium bicarbonateQ as an antidote has been shown to be an effective treatment for resolving the metabolic acidosis and cardiovascular complications of TCA poisoning.If sodium bicarbonate therapy fails to improve cardiac symptoms, conventional antiarrhythmic drugs, such as phenytoin & magnesium can be used to reverse any cardiac abnormalities.Hypotension is initially treated with fluids along with bicarbonate to reverse metabolic acidosis (if present).If the patient remains hypotensive despite fluids, then further measures, such as the administration of epinephrine, norepinephrine, or dopamine can be used to increase blood pressure.Seizures often resolve without treatment but administration of a benzodiazepine or other anticonvulsive may be required for persistent muscular over activity.There is no role for physostigmine in the treatment of tricyclic toxicity as it may increase cardiac toxicity and cause seizuresQ.In cases of severe TCA overdoses that are refractory to conventional therapy, intravenous lipid emulsion therapy has been reported to improve signs & symptoms in moribund patients suffering from toxicities involving several types of lipophilic substances. Therefore, lipids may have a role in treating severe cases of refractory TCA overdose.Tricyclic antidepressants are highly protein-bound and have a large volume of distribution. Therefore, removal of these compounds from the blood with hemodialysis, hemoperfusion or other techniques is unlikely to be of any significant benefitQ.
Sodium bicarbonate
Hemodialysis
Fomepizole
Flumazenil
Pharmacotherapy Management of Children and Adolescents