Episode 206: Gabapentin is associated with postoperative respiratory failure, can IV labetalol be continued after the 300 mg maximum has been reached, and a resource for building a smart pump library

In this episode I’ll:

1. Discuss an article about gabapentin and the link to postoperative respiratory failure.
2. Answer the drug information question “Can IV labetalol be continued after the 300 mg maximum has been reached?”
3. Share a resource for building a smart pump drug library.

Article

Multimodal Analgesic Therapy With Gabapentin and Its Association With Postoperative Respiratory Depression

Lead author: Alexandre Cavalcante

Published in Anesthesia & Analgesia July 2017

Background

Gabapentin is commonly used pre-operatively as part of a multimodal analgesic strategy to lower the use of opioids in the postoperative period. The hope is that less opioid use will lead to a lower incidence of opioid related adverse effects such as respiratory failure. However gabapentin is a CNS depressant, and may also contribute to the incidence of postoperative respiratory failure. The authors of this study sought to determine whether gabapentin was associated with respiratory depression during phase-I postanesthesia recovery after major laparoscopic procedures.

Methods

The study was a retrospective review of over 8000 patients who underwent major laparoscopic procedures lasting at least 90 minutes. Multivariable and propensity score–matched analyses were performed to assess potential associations between preoperative gabapentin use and postoperative respiratory depression.

Results

Postoperative respiratory depression occurred in 15% of cases. In multivariable analysis, gabapentin was associated with respiratory depression (odds ratio, 1.47; P < .001).

These results remained statistically significant in a subgroup of patients who did not have analgesia supplemented by intrathecal opioids.

Elderly patients were at higher risk of respiratory depression.

Patients who experienced respiratory depression had statistically significant increased rates of admission to a higher level of care in the postoperative period.

Conclusion

The authors concluded:

The use of gabapentin is associated with increased rates of respiratory depression among patients undergoing laparoscopic surgery. When gabapentinoids are included in multimodal analgesic regimens, intraoperative opioids must be reduced, and increased vigilance for respiratory depression may be warranted, especially in elderly patients.

 

Discussion

This is a single-center retrospective study, which cannot prove causality. More evidence is needed before deciding to remove gabapentin from multimodal perioperative analgesia regimens.

I do think it is reasonable based on this data to consider empirically reducing opioid doses in elderly patients also receiving gabapentin, given the potential association with respiratory depression.

Drug information question

Q: Can IV labetalol be continued after the 300 mg maximum has been reached?

A: If necessary, with extra monitoring.

Prescribing information for IV labetalol lists a maximum dose of 300 mg, without any explanation of how or why this maximum dose was set. In most patients, hypertension should be controlled after this dose is reached and the patient can be transitioned to another antihypertensive.

However, some patients have refractory hypertension where continued administration of labetalol may be the only option. In this case, when no better options exist, labetalol has been continued. Labetalol has a half-life of 6 hours, which is long for an IV antihypertensive.

Use beyond 300 mg carries a risk of prolonged hypotension and/or bradycardia. Be vigilant for hypotension and bradycardia with higher doses of labetalol, and ensure that treatment such as glucagon or high dose insulin therapy can be initiated immediately if necessary.

Resource

The resource for this episode is the ISMP Guide to Building a Smart Infusion System Drug Library.  This guide covers the design, configuration, testing and go-live phases of smart pump implementation. If you have or are implementing smart pumps at your facility, review this guide against the process being implemented by the pump manufacturer to ensure maximum safety.

 

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If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.

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