med 18

 

 Administer activated charcoal (1 g/kg) to all patients with intact airway reflexes as it

will readily bind to and decrease the absorption of cyclic

antidepressants. Orogastric lavage can be considered in

symptomatic patients who present within an hour of

ingestion after carefully weighing the benefits of removing a

highly toxic drug against the inherent risks of the procedure.

...... Sodium Bicarbonate Therapy

Because the cardiotoxicity of CA poisoning results from

the blockade of myocardial Na+ channels, treatment with

IV sodium bicarbonate (NaHC03

) remains the mainstay

of therapy. Sodium bicarbonate has been shown to improve

electrical conduction and increase myocardial contractility.

The indications for initiation of therapy are as follows:

• QRS complex > 100 msec

• Refractory hypotension

• Terminal R-wave amplitude in lead a VR >3 mm

• Ventricular dysrhythmia

Administer an initial bolus of 1-2 mEq/kg (1 ampule of

NaHC03 contains 50 mEq) and repeat as necessary until

the patient improves or the serum pH reaches 7.5-7.55.

After the initial stabilization, continue treatment with a

NaHC03 infusion at a rate of 2-3 mL!kg/hr.

...... Hypotension

Refractory hypotension is probably the most common

cause of death in cases of CA overdose. Initiate aggressive

volume resuscitation with IV boluses of normal saline, but

CHAPTER 60

Activated charcoal if airway intact

and bowel functional (1 gjkg).

Greater than 6 hours after an acute

ingestion and no evidence of

tachycardia, hemodynamic instabil ity,

CNS abnormal ities, or ECG changes

Medically clear,

consider psych iatric

consult

.A Figure 60-2. Cyclic antidepressants diag nostic algorithm. CNS, central

nervous system; ECG, electroca rd iogram; RAD, right axis deviation.

be wary of patients with underlying cardiopulmonary c onditions so as to not precipitate life-threatening pulmonary

edema. Persistent hypotension that is unresponsive to isotonic crystalloid boluses and NaHC03 therapy warrants

the initiation of vasopressor support. Norepinephrine

(1 meg/min titrated to a max of 30 meg/min) is the agent

of choice as it directly antagonizes the effects of cyclic

antidepressants on the a-adrenergic receptors.

..... Seizures

Most seizures occur within the first 3-4 hours after ingestion. Seizures are typically brief and tonic-clonic in nature.

Benzodiazepines such as diazepam or lorazepam are the

initial treatment of choice. Seizures that are refractive to

benzodiazepines require treatment with IV phenobarbital

(15 mg!kg), although careful attention must be paid to the

patient's hemodynamic status. Phenytoin should be avoided

because it is ineffective in patients with CA poisoning and

may actually exacerbate the cardiotoxicity of these agents.

DISPOSITION

..... Admission

Admit all symptomatic patients to a monitored setting.

Those with signs of moderate to severe poisoning

( eg, lethargy, hypotension, prolonged QRS duration) and

all patients who require treatment with IV NaHCO 3 require

admission to an intensive care unit. Obtain psychiatric

consultation for all patients with intentional overdoses.

..... Discharge

Patients who remain symptom-free throughout an observation period of no less than 6 hours may be safely discharged

home provided they are cleared from a psychiatric perspective .

SUGGESTED READING

Liebelt E. Cyclic antidepressants. In: Flomenbaum NE, Goldfrank

LR, Hoffman RS et al. Goldfrank's Toxicologic Emergencies.

8th ed. New York, NY: McGraw-Hill, 2006, pp. 1083-1097.

Liebelt EL, Ulrich A, Francis PD, et al. Serial electrocardiogram

changes in acute tricyclic antidepressant overdoses. Grit Care

Med. 1 997;25:1721.

Graudins A, Dowsett RP, Liddle C. The toxicity of antidepressant

poisoning: Is it changing? A comparative study of cyclic and

new serotonin-specific antidepressants. EmergMed (Fremantle).

2002; 14:440-446.

Mills KC. Cyclic antidepressants. In: Tintinalli JE, Stapczynski JS,

Ma OJ, Cline DM, Cydulka RK, Meckler GD, eds. Tintinalli's

Emergency Medicine: A Comprehensive Study Guide. 7th ed.