Efficacy of Lipid Emulsion Therapy in Treating Cardiotoxicity from Diphenhydramine Ingestion: A Pooled Analysis

Objective: Summarize the evidence that LET rescues cardiac ion channel blockade (QRS, QTc widening) or hypotension attributable to diphenhydramine overdose. Background: Lipid emulsion therapy (LET) has been most thoroughly studied to reverse local anesthetic systemic toxicity (LAST). Case reports suggest that LET can successfully rescue cardiovascular collapse from bupropion, amitriptyline, and propranolol. The efficacy of LET against refractory hypotension and dysrhythmias from diphenhydramine, a commonly ingested lipophilic cardiotoxic agent, is less well described. Methods: We searched MEDLINE, EMBASE, and Google Scholar for English-language full-length case reports of diphenhydramine (DPH) intoxication in patients older than 17. We extracted data with a PRISMA-compliant protocol, dividing the case reports into two groups, one that received LET and one that did not. We performed a pooled analysis to compare the change in mean arterial pressure (MAP), QRS duration, and QTc duration between the two groups. Results: We identified 22 cases. Lipid emulsion therapy (LET) was used in 6 cases. In all 6 cases, LET was administered because the patient suffered from hypotension refractory to traditional resuscitation. The group the received LET and the group that did not receive LET were comparable in age, gender, amount ingested, and frequency of seizures. The mean arterial pressure (MAP) decreased by 4.5 ± 11.5 mm Hg in those who did not receive LET compared to an increase in MAP 37 ± 17.5 mm Hg in those who did receive LET. The QRS narrowed by 29 ± 33.875 ms (no LET group) vs 68 ± 49.5 ms (LET group) and QTc by 168.5 ± 126.75 ms (no LET group) vs 134 ± 88 ms (LET group). All values expressed as median ± interquartile range. 2 out of the 6 patients who received LET expired, as compared with 4 out of 12 in the group that did not. The 2 patients who received LET and expired passed after withdrawal of care. Conclusion: LET may improve MAP in patients with hypotension refractory to vasopressors due to diphenhydramine toxicity. This study found no significant effect of LET on QRS or QTc duration. These results are limited by a small sample size, reporting bias of case reports, incomplete data, and heterogeneity. A pooled analysis of case reports suggests that LET may rescue hypotension when other methods have failed in patients with hypotension attributable to diphenhydramine overdose. Grants: None