These authors gather 300 patients – 100 non-obese, 100 obese, and 100 morbidly obese – who all received a 4mg intravenous dose of morphine for median initial pain levels of ~8 on a scale to 10. Upon reassessment a median of ~1 hour after administration, the median pain level in all groups had fallen to 2 or 3. This somewhat tailors along with other work, which observed substantial numbers of patients with adequate response following even doses of morphine of less than 4mg. The authors therefore conclude:
“BMI does not predict the analgesic response to a single dose of intravenous morphine in the ED. This is true even for patients who are morbidly obese. We suggest using fixed doses rather than weight-based doses of morphine for acute pain in obese patients.”However, this retrospective study fails to capture and control for many of the other factors associated with opiate response, including age, substance abuse history, pre-hospital pain control – along with all the other contextual factors lost through chart abstraction. Additionally, patients at Maricopa Medical Center in Phoenix are not hardly generalizable to, well, nearly anywhere in the world.
Ultimately, this limited study leads to an erroneous, and potentially harmful conclusion that weight-based doses are unnecessary. Aggressive, titrated or weight-based, pain control is not in any fashion refuted by this work.
“Analgesic response to morphine in obese and morbidly obese patients in the emergency department.”