Beta-blocker overdose in an LPN

Are vasopressors useful in toxin-induced cardiogenic shock?

OBJECTIVE

Overdoses with cardio-depressive medications can result in toxin-induced cardiogenic shock (TICS), a life-threatening condition characterized by severe hypotension and ineffective tissue perfusion. Vasopressors are often employed in the treatment of shock to increase heart rate and blood pressure. We sought to conduct a systematic review of the literature to evaluate the effectiveness of vasopressors in improving hemodynamic function and survival in the treatment of TICS.

DATA SOURCES

We searched PubMed, EMBASE, TOXLINE, and International Pharmaceutical Abstracts.

STUDY SELECTION

We included studies evaluating the use of vasopressors in humans or animals with TICS. We limited human study types to randomized controlled trials, clinical trials, observational studies, and case reports.

DATA EXTRACTION

Our search yielded 913 citations and 144 of these met our inclusion criteria. 130 were human case reports and 14 were animal studies.

DATA SYNTHESIS

Human case report data showed vasopressors were ineffective more often than they were partially or fully effective. In the majority of animal studies, vasopressor treatment failed to improve hemodynamic parameters and resulted in decreased survival.

CONCLUSIONS

Human case reports and controlled animal experiments lead to different conclusions about vasopressors in TICS. Most animal studies indicate that vasopressors impair hemodynamic function and increase mortality. In contrast, human case reports suggest that vasopressors are often ineffective but not necessarily harmful.

Electrocardiographic changes associated with beta-blocker toxicity

STUDY OBJECTIVE

We sought to characterize the ECG changes associated with symptomatic beta-blocker overdose.

METHODS

The study population consisted of a prospective cohort of patients reporting to 2 regional poison centers with beta-blocker overdose. Each patient received an ECG on presentation and a structured follow-up. The inclusion criteria for symptomatic overdose included heart rate of less than 60 beats/min or systolic blood pressure of less than 90 mm Hg; symptoms consistent with decreased end-organ perfusion; therapeutic intervention with cardioactive medication; and corroboration by 2 of the authors that this was a clear-cut case of symptomatic beta-blocker overdose with cardiovascular toxicity. Exclusion criteria included cardioactive coingestants, age younger than 6 years, and no available ECG.

RESULTS

Of 167 patients, 13 were determined to have symptomatic exposures. First-degree heart block (>200 ms) was the most common ECG finding (10/12) and also had the greatest likelihood ratio (5.31) when comparing those with symptomatic exposures with those with asymptomatic exposures. Comparing the asymptomatic with the symptomatic groups, the mean PR interval was 167 ms (95% confidence interval [CI] 162 to 171 ms) versus 216 ms (95% CI 193 to 238 ms), the mean QRS interval was 89 ms (95% CI 87 to 91 ms) versus 112 ms (95% CI 92 to 132 ms), the mean QTc interval was 422 ms (95% CI 417 to 428) versus 462 ms (95% CI 434 to 490 ms), and the mean heart rate was 72 beats/min (95% CI 69 to 74 beats/min) versus 66 beats/min (95% CI 59 to 73 beats/min). Two cases of symptomatic acebutolol exposure appeared unique by demonstrating disproportionate prolongation of the QTc interval, an RaVR height of 3 mm or greater, and associated ventricular tachydysrhythmia.

CONCLUSION

The majority of clinically significant beta-blocker intoxications demonstrate negative dromotropic effects on ECG. Several ECG differences in acebutolol intoxication might reflect unique pathophysiologic processes relative to other beta-blockers.

Acebutolol overdose resulting in fatalities

Two fatal cases of Acebutolol intoxication are presented that demonstrate its clinical characteristics and potential lethality. A review of the literature suggests that acebutolol is one of the most toxic beta blockers when taken as an overdose. In addition to demonstrating characteristics of membrane-stabilizing activity, both fatal cases demonstrate significant QTc prolongation and ventricular tachycardia. The latter findings suggest an impact on ventricular repolarization not seen with Propranolol intoxication. Clarification of these findings has important implications regarding identification and treatment of this potentially fatal intoxication.

Acebutolol overdose treated with hemodialysis and extracorporeal membrane oxygenation

A case involving a 27-year-old woman who ingested an overdose of acebutolol is presented. Extracorporeal membrane oxygenation was initiated to stabilize the patient's condition before commencing hemodialysis. S-diacetolol (the N-acetelation product of acebutolol) was cleared with hemodialysis. It is suggested that extracorporeal membrane oxygenation may be of short-term benefit in the treatment of overdoses with beta-adrenergic agents such as acebutolol when accelerated clearance with hemodialysis is anticipated.