Abstract
Background: Patient-controlled sedation (PCS) is increasingly used for moderate sedation. Detailed understanding is essential for maintaining safety and giving the most benefit. We wanted to explore the associations between patients’ characteristics, perioperative pain and anxiety, the procedure, and the calculated concentrations at the effect site (Ce) of propofol. We also wanted to analyse the pharmacokinetic profiles of propofol and alfentanil during PCS, and their association with respiratory complications. Methods: 155 patients were double-blinded and randomised to have propofol or propofol and alfentanil for PCS during gynaecological surgery. Pharmacokinetic simulation of Ce and multiple regressions aided the search for correlations between explanatory variables and concentrations of drugs. Results: In group propofol, treatment for incontinence, anterior repair, and the patient’s weight correlated the best (B-coef = 0.20, 0.20 and 0.01; r = 0.69; r² = 0.48). When alfentanil was added, alfentanil and the patient’s weight were associated with Ce of propofol (B-coef = ǂ.40 and 0.01; r = 0.70; r² = 0.43). Logistic regression indicated that age and Ce of drugs were related to ten cases of respiratory complications. Conclusions: Patients’ weights and the type of surgery performed were associated with the Ce of propofol; this knowledge could be used for refinement of the doses given during PCS. Because the pharmacokinetic profiles of propofol and alfentanil are different, the alfentanil effect becomes predominant during the time course of sedation. In order to reduce the risk of early and late respiratory depression, alfentanil should not be added to propofol in the same syringe.
Highlights
Minor procedures can be managed successfully using local anaesthesia and moderate sedation with propofol [1], and American [2] and European guidelines [3] give specific recommendations for the use of propofol by nonanaesthetists
Propofol given for patient-controlled sedation (PCS) is an option for moderate sedation, and is often combined with opioids for the control of pain [5]-[7], respiratory events have been reported when remifentanil [8] or alfentanil [9] were added to propofol
The patients’ weight and the type of surgery performed were associated with the Ce of propofol; this knowledge could be used for the refinement of the doses given through Patient-controlled sedation (PCS)
Summary
Minor procedures can be managed successfully using local anaesthesia and moderate sedation with propofol [1], and American [2] and European guidelines [3] give specific recommendations for the use of propofol by nonanaesthetists. Propofol given for patient-controlled sedation (PCS) is an option for moderate sedation, and is often combined with opioids for the control of pain [5]-[7], respiratory events have been reported when remifentanil [8] or alfentanil [9] were added to propofol. Knowledge about accumulated doses of propofol and opioids, and the factors that explain why patients request repeated doses, is limited, but could help to improve safety. We wanted to analyse the pharmacokinetic profiles of propofol and alfentanil during PCS, and their association with respiratory complications. Conclusions: Patients’ weights and the type of surgery performed were associated with the Ce of propofol; this knowledge could be used for refinement of the doses given during PCS. In order to reduce the risk of early and late respiratory depression, alfentanil should not be added to propofol in the same syringe
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