Response to dopamine vs norepinephrine in tricyclic antidepressant-induced hypotension.

OBJECTIVE: To compare the efficacy of dopamine (DA) with that of norepinephrine (NE) in the treatment of refractory hypotension caused by tricyclic antidepressants (TCAs).

METHODS: A retrospective analysis was used to compare blood pressure responses in concurrent case series of patients treated with vasopressors for TCA-associated hypotension. The patients were adults (aged > or = 16 years) treated at 2 urban teaching hospitals from 1983 to 1994. All patients were diagnosed as having TCA ingestion (positive serum toxicologic assay), were hypotensive [systolic blood pressures (SBPs) < or = 90 mm Hg], and required vasopressor therapy. The patients were grouped by initial vasopressor treatment (i.e., NE vs DA).

RESULTS: There were 26 hypotensive adult patients who met study criteria. All 26 patients remained hypotensive after initial treatment of their TCA-associated hypotension with crystalloid infusion and alkalinization. The NE and DA groups were similar in age, sex, and proportion of patients with single and co-drug ingestion. The NE group, however, had a significantly lower average SBP at study entry (56 vs 74 mm Hg, p = 0.04). Nine of 15 (60%) patients responded to DA (5-10 micrograms/kg/min) and 11/11 (100%) patients responded to NE (5-53 micrograms/min). The difference in response rates was statistically significant (p = 0.02). Six patients in whom DA (max rate 10-50 micrograms/min/kg) failed to raise the SBP subsequently responded to NE (max rate 5-74 micrograms/ min) when this drug was later used. One patient receiving NE (12 micrograms/min) developed ventricular ectopy, successfully treated with lidocaine. There were no ischemic complications from either NE or DA. Patients who failed DA therapy tended to be older (39 vs 30 years, p = 0.08), to be more hypotensive at study entry (64 vs 81 mm Hg, p = 0.008), and to remain hypotensive even at higher doses of DA (24 vs 7 micrograms/min/kg, p = 0.002).

CONCLUSION: While this was not a prospective randomized study, NE appears advantageous over DA as the first-line vasopressor agent for those patients who require vasopressor support in the setting of TCA-induced hypotension that is refractory to IV fluid and serum alkalinization.