Propofol in the ED: Check your doses!

Letters

CJEM 2002;4(1):3-6

To the editor:

Doses of 16-33 mg/min for patient-controlled sedation were repeatedly quoted in Dr. Ducharme's commentary.¹ These doses would be expected to result in general anesthesia within 10 minutes! Propofol infusions in the range of 20-40 mcg/kg/min (i.e., 1.5-3 mg/min for a 70-kg patient) titrated to patient response with boluses of approximately 200 mcg/kg (15 mg) are more commonly used for procedural sedation. (Product monograph recommendations for surgical diagnostic sedation are for 25-75 mcg/kg/min after 0.5-1.0 mg/kg bolus over 3 to 5 minutes.)

I have difficulty understanding how Dr. Ducharme could author a commentary on propofol that repeatedly quotes infusion rates for sedation that are over 10 times those recommended and used clinically. Although Dr. Ducharme undoubtedly has experience with intermittent mini-dose titration of propofol, his commentary suggests this is not the case with administering propofol infusions. Readers who utilize Dr. Ducharme's recommended propofol infusion rates of 16-33 mg/min for sedation will quickly find themselves managing an apneic, unconscious patient. Dr. Ducharme's proposed study on patient-controlled sedation using propofol in doses of greater than 25 mg/min would undoubtedly be a short, unpublished study.

I do, however, agree with Dr. Ducharme's comments that mini-dose titration of propofol (20 mg every 45-60 seconds) for sedation during cardioversion minimizes the incidence of apnea and hypotension and allows for rapid emergence for the procedure. In obese patients I have found that positioning the patient in the right lateral decubitus position (recovery position) prior to cardioversion has several advantages.

1. The anterior-posterior placement of the paddles in the obese patient provides a more direct route of energy through the heart and in my experience is associated with a high success rate.

2. Airway obstruction is less likely to occur in the recovery vs. the supine position (as there is a tendency for obstruction to occur as a result of the tongue falling back when the patient is in the supine position).

3. Airway assistance and manoeuvres (jaw thrust, chin lift, positive pressure ventilation) are essentially never required in the recovery position when propofol is titrated properly.

4. Having the patient position himself in the recovery position prior to the procedure saves the staff from manually turning the unconscious patient on his side at the end of the cardioversion.

5. Obstructed respiratory efforts in the supine position generate positive intra-abdominal and negative intra-thoracic pressures, which increases the likelihood of gastric regurgitation and or aspiration.

6. The recovery position is preferable to the supine position for suctioning should regurgitation occur.

Patrick Sullivan, MD 
Associate Professor 
Department of Anesthesia 
University of Ottawa 
Ottawa, Ont.

Reference

1. Ducharme J. Propofol in the emergency department: another interpretation of the evidence [commentary]. CJEM 2001;3(4):311-2.