Patient selection: This should be used in patients with indications for parenteral morphine (see above) or for whom alternative methods have failed.
NOTE: The assumption is that the patient has been on chronic, around the clock narcotic medication and is opioid tolerant. These patients have an oral-to-parenteral morphine equivalence of 2:1 or 3:1 rather than the 6:1 seen in patients with acute exposure.
Steps:
(1) Calculate the total 24 hour parenteral opioid dose in milligrams based on the around the clock and rescue doses.
(a) If nonmorphine agents are used, use an equianalgesic table to estimate the equivalent morphine dose.
(b) Convert oral morphine doses to parenteral morphine doses by dividing the oral dose by 3.
(2) Determine the routine doses:
(a) Divide the total 24 hour parenteral dose by 24 to determine the hourly dose.
(b) A rescue dose of 50% of the hourly dose can be given every 2 hours as needed.
(3) If severe pain is present at the start of management, then do both of the following:
(a) Give a loading dose by infusion (not by push) that is twice the hourly dose.
(b) Increase the hourly dose by 20%, reducing the dose once the pain is under control.
If the opioid requirements are unknown or if the total daily parenteral dose equivalent is < 12 mg (< 0.5 mg per hour) then:
(1) Determine the appropriate dose by giving intermittent intravenous bolus doses every 2 hours for 24 hours.
(2) Start at Step 1 of the protocol.
After a few days of the regimen, re-evaluate the patient for
(1) the number of rescue doses being administered
(2) side effects
(3) the adequacy of pain control
and recalculate the regimen.
