Previous diagnoses, opioid use affect opioid dosing at end of life
MedWire News: Premorbid conditions and a chronic use of opioids may affect opioid dosing during and after terminal withdrawal of mechanical ventilation, say US researchers.
The team also reports that higher doses of morphine after terminal extubation are associated with a longer time to death.
One possible explanation for this latter finding is that "patients who survive longer are at risk of suffering longer and quite understandably may need escalating and higher doses of opioids and anxiolytics," write Mark Mazer (East Carolina University, Greenville) and colleagues in the Journal of Pain and Symptom Management.
The team investigated opioid administration in 74 terminally ill patients on mechanical ventilation, in order to determine if dosing "was commensurate with the published guidelines and reports." All patients were expected to die shortly after ventilation withdrawal.
Patients were aged a mean 60 years, and 34 (46%) were women. A total of 32 (43%) patients had sepsis with concomitant acute respiratory failure, 20 (27%) had a chronic obstructive pulmonary disease, 17 (23%) had experienced an acute primary neurological event, and 14 patients (19%) were persistently comatose secondary to hypoxic ischemic encephalopathy after cardiopulmonary resuscitation.
The usual infusion rate of morphine recommended for patients undergoing withdrawal of life-sustaining therapy is 0.05-0.50 mg/kg per hour, note the researchers, who observed a mean 5.3 mg dose of morphine given to patients in their cohort during the hour before ventilation withdrawal.
Mean doses were slightly higher among patients who died before extubation compared with those who died after, at 5.5 versus 5.2 mg, however, the mean dose given to patients during the hour they survived after extubation was significantly higher, at 10.6 mg.
Of the 38 (51%) patients who were receiving morphine before terminal weaning, doses given both before (for those who died before) and after (for those who died after) extubation were higher compared with the respective mean doses for all patients, at 10.7 and 15.5 mg. The increased dose given to patients who lived past extubation was significantly higher than that given to them before extubation.
Analysis showed that morphine doses given before extubation did not correlate with age, gender, or a chronic pulmonary diagnosis, but did correlate with home opioid use (9.4 vs 4.5 mg in those who did vs did not use morphine at home), and significantly so with sepsis with concomitant respiratory failure (8.9 vs 2.6 for those with vs without sepsis).
Mazer and co-researchers note that these associations were also true for the dose of morphine given during the last hour of life after extubation.
The mean time to death in the cohort ranged between 4 minutes and 934 minutes. While the dose of morphine given before extubation did not correlate with time to death, a higher dose given after extubation was associated with time to death, such that each 1 mg/hour of morphine delayed death by 7.9 minutes.
"As higher palliative doses of morphine are associated with longer times to death after terminal extubation, we urge clinicians to prescribe as much morphine as is needed to assuage pain and dyspnea in this setting," conclude Mazer et al.
By Sarah Guy