In this episode, I’ll discuss using actual vs ideal body weight for dosing of sedatives in critically ill patients.
The majority of sedative medications used in critically ill patients to allow them to tolerate mechanical ventilation and other aspects of ICU care are lipophilic. As such, the medications have a greater volume of distribution in obese patients yet there is not a lot of data on whether it is best to dose these medications using ideal or actual body weight in the obese patient population.
A group of authors published in AJHP a single-center retrospective observational cohort study looking at the impact of ideal vs actual body weight on analgesic and sedative requirements in critically ill patients with obesity in an effort to add to the available data on this topic.
The study cohort was a before-after population in a hospital that converted their dosing strategy from an actual body weight into an ideal body weight approach for fentanyl, ketamine, propofol, and dexmedetomidine.
All patients in the study had a BMI over 30, and there were 46 patients analyzed in the actual body weight group and 31 in the ideal body weight group.
The primary outcome was cumulative morphine milligram equivalent (MME) requirements during the fentanyl continuous infusion. Secondary outcomes were cumulative sedation doses and the durations of mechanical ventilation, ICU stay, and hospital length of stay (LOS). Efficacy was evaluated using RASS and CPOT scores, as well as as-needed analgesic and sedative requirements, in MME and midazolam equivalents.
The ideal body weight group had a statistically significantly lower cumulative IV MME requirement at just 538 vs 931 for the actual body weight group. This difference was nearly entirely due to lower doses of fentanyl in the ideal body weight group. There were no significant differences found for any of the other sedatives or for as needed opioids and benzodiazepines nor was there for duration of mechanical ventilation, ICU LOS, or hospital LOS.
The authors concluded:
Utilizing IBW dosing decreased cumulative opioid requirements in critically ill patients with obesity without resulting in increased doses of other sedatives or as-needed medications.
Presumably, the lower dose of fentanyl would show up as a benefit in reduced delirium if a large enough cohort was studied. For hospitals that wish to gain the benefits of lower sedative use with ideal body weight, simply starting with a lower dose of fentanyl or even using a fixed rather than non-weight based dosing scheme may be a quicker and easier route to implementation when compared with the effort needed to change order sets, smart pump libraries, policies, and staff education for all critical care sedative medications.
The article in this episode is a selection from my Hospital Pharmacy Academy’s weekly literature digest. Have you ever felt like your physician colleagues are one step ahead of you with new literature developments? Every week, Academy members are provided a summary curated and explained by me of the top hospital pharmacy-related articles published that week from over 20 major journals and sources to save you time and keep you up to date with the literature. To get immediate access, go to pharmacyjoe.com/academy.
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