Postoperative patient-controlled analgesia with alfentanil: Analgesic efficacy and minimum effective concentrations

Abstract

Forty ASA I-III patients recovering from major abdominal or orthopedic operations were investigated in an open clinical study to evaluate analgesic efficacy and threshold plasma concentrations of alfentanil during the early postoperative period using patient-controlled analgesia (PCA) by means of the On-Demand Analgesia Computer. Alfentanil demand dose was 212 micrograms, continuous infusion rate 25 micrograms/hr, hourly maximum dose 1.5 mg/hr; the lockout time was set to 1 min. The duration of PCA was 18.1 +/- 5.2 hr (mean, SD) during which time 23.8 +/- 14.2 demands per patient were recorded, resulting in an average alfentanil consumption of 4.99 +/- 3.03 micrograms/kg/hr. Patient acceptance of PCA was high. Side effects were only of minor intensity and never gave rise to concern. Based on our own earlier PCA experience with other opiate analgesics, alfentanil proved to be about 1/15th as potent an analgesic as fentanyl and about 6-7 times more potent than morphine if both intensity and duration of effect were considered. Minimum effective alfentanil plasma concentration (MEC) varied greatly and could be best described by a lognormal distribution (range 0.6-99.2 ng/mL, median 14.9 ng/mL). Intraindividual MEC variability was consistently lower than intersubject variability (37.0% vs 65.2%).

Concentration‐Effect Relationships for Intravenous Alfentanil and Ketamine Infusions in Human Volunteers: Effects on Acute Thresholds and Capsaicin‐Evoked Hyperpathia

“…In our study, the effect of alfentanil began at the 75 ng/ml plasma level, suggesting the threshold analgesic plasma concentration of alfentanil to be somewhere between 50 and 75 ng/ml. A previous study by Lehmann et al, 51 who looked at the minimum effective plasma concentration (MEC) of alfentanil on postoperative pain, showed a large intersubject variability (a finding consistent with our study). The MEC ranged from 0.6 to 99.2 ng/ml.…”

Randomised double‐blind comparison of morphine vs. a morphine–alfentanil combination for patient‐controlled analgesia

“…After surgery, patients were randomly allocated, by drawing of shuffled, coded envelopes, to receive postoperative analgesia by PCA using one of two solutions: morphine 0.5 mg.ml ¹1 plus alfentanil 0.083 mg.ml ¹1 (group MA, n ¼ 40) or morphine 1 mg.ml ¹1 alone (group M, n ¼ 40). The ratio of alfentanil to morphine (1 : 6) was based on published data on equipotency ratios for opioids used for PCA calculated according to pain scores and drug consumption [4,5]. The PCA solutions were prepared by an anaesthetist or investigator who was not involved with subsequent patient assessments.…”

A comparison of patient-controlled analgesia fentanyl and alfentanil for labour analgesia

“…10 All patients in the alfentanil group had a maternal serum concentration greater than 14.9 ng·ml -1 , the MEAC of alfentanil. 11 …”