Pharmacokinetics of sufentanil in patients undergoing abdominal aortic surgery

[Sufentanil during anesthetic induction of remifentanil-based total intravenous anesthesia: a randomized controlled trial]

BACKGROUND

Postoperative pain represents an important concern when remifentanil is used for total intravenous anesthesia because of its ultrashort half-life. Longer acting opioids, such as sufentanil, have been used during induction of remifentanil-based total intravenous anesthesia as a means to overcome this shortcoming. However, the effectiveness and safety of such strategy still lacks evidence from randomized clinical trials. Hence, we aimed to assess the postoperative analgesic efficacy and safety of a single dose of sufentanil administered during the induction of remifentanil-based total intravenous anesthesia.

METHODS

Forty patients, scheduled for elective open abdominal surgery, were randomized to receive remifentanil-based total intravenous anesthesia with or without a single dose of sufentanil upon induction. We assessed the postoperative morphine consumption administered through a patient-controlled analgesia pump. Self-reported pain scores and the occurrence of nausea, vomiting, pruritus, agitation, somnolence and respiratory depression were also assessed up to 2 days after surgery.

RESULTS

The mean difference between the sufentanil and control groups regarding morphine consumption in the post-anesthetic care unit and at 12, 24 and 48h after surgery were -7.2mg (95%CI: -12.5 to -2.1, p<0.001), -3.9mg (95%CI: -11.9 to 4.7, p=0.26), -0.6mg (95%CI: (-12.7 to 12.7, p=0.80), and -1.8mg (95%CI: (-11.6 to 15.6, p=0.94), respectively. Neither self-reported pain nor the incidence of adverse events were significantly different between groups at any time point.

CONCLUSION

Our findings suggest that the administration of sufentanil during induction of remifentanil-based total intravenous anesthesia is associated with decreased early postoperative opioid consumption.

[Sufentanil during anesthetic induction of remifentanil-based total intravenous anesthesia: a randomized controlled trial]

BACKGROUND

Postoperative pain represents an important concern when remifentanil is used for total intravenous anesthesia because of its ultrashort half-life. Longer acting opioids, such as sufentanil, have been used during induction of remifentanil-based total intravenous anesthesia as a means to overcome this shortcoming. However, the effectiveness and safety of such strategy still lacks evidence from randomized clinical trials. Hence, we aimed to assess the postoperative analgesic efficacy and safety of a single dose of sufentanil administered during the induction of remifentanil-based total intravenous anesthesia.

METHODS

Forty patients, scheduled for elective open abdominal surgery, were randomized to receive remifentanil-based total intravenous anesthesia with or without a single dose of sufentanil upon induction. We assessed the postoperative morphine consumption administered through a patient-controlled analgesia pump. Self-reported pain scores and the occurrence of nausea, vomiting, pruritus, agitation, somnolence and respiratory depression were also assessed up to 2 days after surgery.

RESULTS

The mean difference between the sufentanil and control groups regarding morphine consumption in the post-anesthetic care unit and at 12, 24 and 48h after surgery were -7.2mg (95%CI: -12.5 to -2.1, p<0.001), -3.9mg (95%CI: -11.9 to 4.7, p=0.26), -0.6mg (95%CI: (-12.7 to 12.7, p=0.80), and -1.8mg (95%CI: (-11.6 to 15.6, p=0.94), respectively. Neither self-reported pain nor the incidence of adverse events were significantly different between groups at any time point.

CONCLUSION

Our findings suggest that the administration of sufentanil during induction of remifentanil-based total intravenous anesthesia is associated with decreased early postoperative opioid consumption.

Do we have today a reliable method to detect the moment of loss of consciousness during induction of general anaesthesia?

This review aims to give an overview of the current state of monitoring depth of anaesthesia and detecting the moment of loss of consciousness, from the first clinical signs involved in anaesthesia to the latest technologies used in this area. Such techniques are extremely important for the development of automatic systems for anaesthesia control, including preventing intraoperative awareness episodes and overdoses. A search in the databases Pubmed and IEEE Xplore was performed using terms such anaesthetic monitoring, depth of anaesthesia, loss of consciousness, as well as anaesthesia indexes, namely BIS. Despite the several methods capable of monitoring the hypnotic state of anaesthesia, there is still no methodology to accurate detect the moment of loss of consciousness during induction of general anaesthesia.

Pharmacokinetics of sufentanil during long-term infusion in critically ill pediatric patients

The aim of this study was to develop a population pharmacokinetic model of sufentanil and to assess the influence of covariates in critically ill children admitted to a pediatric intensive care unit. After institutional approval, 41 children were enrolled in the study. Blood samples for pharmacokinetic (PK) assessment were collected from routinely placed arterial catheters during and after discontinuation of infusion. Population nonlinear mixed-effects modeling was performed using NONMEM. A 2-compartment model described sufentanil PK sufficiently. Typical values of the central and peripheral volume of distribution and the metabolic and intercompartmental clearance for a theoretical patient weighing 70 kg were VC = 7.90 l, VT  = 481 L, Cl =  5.3 L/h, and Q = 38.3 L/h, respectively. High interindividual variability of all PK parameters was noted. Allometric/isometric principles to scale sufentanil PK revealed that to achieve the same steady-state sufentanil concentrations in plasma for pediatric patients of different body weights, the infusion rate should follow the formula (infusion rate for a 70-kg adult patient, μg/h) × (body weight/70 kg)(0.75). Severity of illness described by PRISM score, the monitored physiological and laboratory parameters, and coadministered drugs such as vasopressors were not found to be significant covariates.

[Brain death diagnosis after sedation with propofol or sufentanil. Recommendations for the usage of toxicological analytics]

BACKGROUND

Before the clinical diagnosis of brain death is made, toxicological analyses are often performed for the exclusion of effective serum levels of previously applied sedating drugs. For propofol and sufentanil there are no uniform recommendations for the usage of toxicology test results.

OBJECTIVES

To develop a standard practice in the diagnosis of brain death after therapeutic application of one of these drugs.

MATERIAL AND METHODS

Based on the current literature and the available analytical assays, an ad hoc working group consisting of specialists in toxicology and intensive care medicine compiled recommendations for the usage of toxicological analytics in the diagnosis of brain death at the Rostock University Hospital.

RESULTS

For propofol, current analytical assays allow the quantification of serum concentrations of 0.2 μg/ml and lower; the execution of clinical brain death diagnostics is recommended by the ad hoc group only at propofol serum levels lower than  0.4 μg/ml. For sufentanil, the currently prevalent assays set lower determination limits of about 0.2 ng/ml in serum and 0.1 ng/ml in urine, which is above the cautiously adopted lower therapeutic serum concentration of 0.02 ng/ml. Therefore after negative determination of sufentanil (< 0.2 ng/ml) in blood serum, the following alternative procedures are recommended: (1) the execution of clinical brain death diagnostics under administration of naloxone; or (2) at intact renal function the additional negative determination of sufentanil in urine (< 0.1 ng/ml). If an assay allowing the detection of sufentanil at ≤ 0.01 ng/ml is available, brain death diagnostics should be carried out only at a serum level lower than  0.02 ng/ml.

CONCLUSION

These recommendations may serve as a proposal for similar standards in other hospitals.

Cholestasis and endogenous opioids: liver disease and exogenous opioid pharmacokinetics

A class of endogenous opioids is upregulated in liver disease particular to cholestasis, which contributes to symptoms in liver disease such as pruritus, hypotension and encephalopathy. Symptoms associated with cholestasis are reversed or at least ameliorated by mu opioid receptor antagonists. Palliation of symptoms related to cholestatic liver disease also involves bile acid binding agents. Opioid receptor antagonists, unlike bile acid binding agents, have been reported to relieve multiple symptoms, except for pruritus, and improve liver function as demonstrated in experimental cholestasis. Exogenous opioid pharmacology is altered by liver disease. Dose reduction or prolongation of dose intervals is necessary depending on the severity of liver disease.

Effects of sufentanil or ketamine administered in target-controlled infusion on the cerebral hemodynamics of severely brain-injured patients*

OBJECTIVE

The manual injection of a bolus of opioid in patients with brain injury induces an increase in intracranial pressure related to a decrease in mean arterial pressure. Such an effect has not been observed with the use of ketamine. The use of target-controlled infusion would minimize or suppress this adverse effect of opioid. This study evaluated the effects of an increase in plasma concentrations of sufentanil or ketamine administered by target-controlled infusion on cerebral hemodynamics.

DESIGN

Prospective, randomized study.

SETTING

Intensive care unit in a trauma center.

PATIENTS

Thirty patients with severe traumatic brain injury.

INTERVENTIONS

Patients were assigned to receive sedation consisting of sufentanil-midazolam or ketamine-midazolam using target-controlled infusion. Twenty-four hours after the onset of sedation, the target concentrations of sufentanil or ketamine were doubled for 15 mins. Blood samples were collected to determine the actual plasma concentration of sufentanil and ketamine, before and 15 mins after concentration change.

MEASUREMENTS AND MAIN RESULTS

The baseline values of intracranial pressure and cerebral perfusion pressure were similar in both groups. The two-fold increase in drug concentrations did not involve a significant change for intracranial pressure, cerebral perfusion pressure, and mean velocity of middle cerebral artery in both the ketamine and the sufentanil groups. The measured plasma concentrations of sufentanil and ketamine were 0.4 +/- 0.2 ng/mL and 2.6 +/- 2.2 mug/mL, respectively, before the increase in concentrations and 0.7 +/- 0.4 ng/mL and 5.5 +/- 3.8 mug/mL after.

CONCLUSIONS

The present study shows that the increase in sufentanil or ketamine plasma concentrations using a target-controlled infusion is not associated with adverse effects on cerebral hemodynamics in patients with severe brain injury. The use of target-controlled infusion could be of interest in the management of severely brain-injured patients. However, there is a need for specific pharmacokinetic models designed for intensive care unit patients.

Influence of peroperative opioid on postoperative pain after major abdominal surgery: sufentanil TCI versus remifentanil TCI. A randomized, controlled study

BACKGROUND

Sufentanil and remifentanil are characterized by two different pharmacokinetic profiles. The aim of this study was to compare the effects of sufentanil and remifentanil administered using target-controlled infusion (TCI) on recovery and postoperative analgesia after major abdominal surgery.

METHODS

Thirty adult patients scheduled for open colorectal surgery were included in a prospective, randomized study. Sufentanil TCI (sufentanil group) or remifentanil TCI (remifentanil group) was administered during surgery. In the remifentanil group, 30 min before the anticipated end of surgery, morphine 0.15 mg x kg(-1) was administered i.v. In the sufentanil group, an effect-site concentration of 0.25 ng x ml(-1) was targeted at extubation. In both groups, postoperative pain was controlled by titration of i.v. morphine and then patient-controlled analgesia with morphine.

RESULTS

The extubation time was similar in the two groups (mean (SD) 13 (6) and 14 (6) min in the sufentanil and remifentanil groups respectively). Visual analogue scale scores were significantly greater during the first 2 h after tracheal extubation in the remifentanil group than in the sufentanil group. The time to first analgesic request in the postanaesthesia care unit was significantly longer in the sufentanil group than in the remifentanil group (55 (64) (range 2-240) vs 11 (7) (1-29) min; P<0.001). The cumulative morphine dose for titration was significantly greater in the remifentanil group (P<0.01). The cumulative morphine dose used during titration and patient-controlled analgesia was significantly greater in the remifentanil group 4, 12 and 24 h after extubation (P<0.05).

CONCLUSION

TCI sufentanil (0.25 ng ml(-1) effect-site concentration at extubation) is more effective than the intraoperative combination of remifentanil TCI infusion with morphine bolus (0.15 mg x kg(-1)) for postoperative pain relief after major abdominal surgery and does not compromise extubation and recovery.

Pharmacokinetics of long-term sufentanil infusion for sedation in ICU patients

OBJECTIVE

To determine the pharmacokinetics of long-term infusion of sufentanil in ICU patients.

DESIGN AND SETTING

Open-label study in a surgical intensive care unit.

PATIENTS

Ten consecutive patients without renal or hepatic failure requiring mechanical ventilation for at least 6 days.

INTERVENTIONS

Patients received sufentanil (initial bolus 0.5 micro g/kg and continuous infusion rate of 0.5 micro g/kg per hour) and midazolam (initial bolus 0.08 mg/kg and continuous infusion 0.05 mg/kg per hour). Sedation was adjusted according to the Ramsay scale (score >3). Blood samples were taken during and up to 72 h after the infusion, and plasma concentrations were measured using a sensitive radioimmunoassay method.

MEASUREMENTS AND RESULTS

Plasma concentration-time profiles of sufentanil and pharmacokinetic parameters such as initial postinfusion half-life (t(1/2alpha)), elimination half-life (t(1/2beta)), total clearance (Cl), volume of distribution (Vdbeta), and time required to obtain a 50% decrease in plasma concentration (tcp(0/2)). The mean duration of sedation was 12+/-7 days. The initial half-life t(1/2alpha) was 1.33+/-1.15 h. The observed prolonged elimination half-life (t(1/2beta)=25.5+/-9.4 h) was related to the large volume of distribution (Vdbeta=22.6+/-9.4 l/kg). The mean total clearance was 13.4+/-7.0 ml/kg per minute. The mean time required to obtain a 50% decrease in plasma concentration was short (tcp(0/2=)4.7+/-3.7 h).

CONCLUSIONS

The pharmacokinetic analysis of sufentanil for ICU sedation revealed increased volume of distribution and elimination half-life. Nevertheless the rapid distribution and elimination processes suggest that the rapid reversibility of sedation with sufentanil is maintained after long duration of infusion. Further studies should be carried out to evaluate the clinical relevance of these results.

Pharmacokinetics of sufentanil in patients undergoing coronary artery bypass graft surgery

OBJECTIVE

To determine the pharmacokinetics of sufentanil in patients undergoing coronary artery bypass graft surgery.

DESIGN

Prospective, multigroup study.

SETTING

University-affiliated hospital.

PARTICIPANTS

Patients with good left ventricular function undergoing elective surgery (n = 103).

INTERVENTIONS

Sufentanil was administered by target-controlled infusion, with target effect-site concentrations ranging from 0.4 to 4.5 ng/mL. Isoflurane was administered as required to maintain stable hemodynamics. Sufentanil pharmacokinetics were determined by population modeling. The potential effects of gender, weight, different premedications (lorazepam, morphine-scopolamine, or clonidine), and coinduction with propofol on sufentanil pharmacokinetics were explored.

MEASUREMENTS AND MAIN RESULTS

The first model determined was a simple 3-compartment model, without any covariates, which had these parameters: V(1) = 5.7 L, V(2) = 18.1 L, V(3) = 225 L, Cl(1) = 0.69 L/min, Cl(2) = 3.1 L/min, and Cl(3) = 1.4 L/min. The overall predictive ability during the entire pre-cardiopulmonary bypass period of this model was excellent, with virtually no bias (median prediction error, -0.4%) and good precision (median absolute prediction error, 18.4%). More complex models with the various premedications used or coinduction with propofol as covariates did not improve the predictive accuracy or precision compared with the simple 3-compartment model. Similarly, including either gender or weight as a covariate did not improve predictive ability.

CONCLUSION

The authors have determined a pharmacokinetic model for sufentanil that can be used to maintain desired target concentrations of sufentanil before cardiopulmonary bypass, with a high degree of accuracy and acceptable variability. Concomitantly administered medications (lorazepam, morphine-scopolamine, clonidine, or propofol) do not appear to have any clinically important effects on distribution-phase sufentanil pharmacokinetics.

Effects of fentanyl, alfentanil, remifentanil and sufentanil on loss of consciousness and bispectral index during propofol induction of anaesthesia

The bispectral index (BIS) and a sedation score were used to determine and compare the effect of propofol in the presence of fentanyl, alfentanil, remifentanil and sufentanil. Seventy-five non-premedicated patients were assigned randomly into five groups (15 in each) to receive fentanyl, alfentanil, remifentanil, sufentanil or placebo. Opioids were administered using a target-con-trolled infusion device, to obtain the following predicted effect-site concentrations: fentanyl, 1.5 ng ml(-1); alfentanil, 100 ng ml(-1); remifentanil, 6 ng ml(-1); and sufentanil, 0.2 ng ml(-1). After this, a target-controlled infusion of propofol (Diprifusor) was started to increase concentration gradually, to achieve predicted effect-site concentrations of 1, 2, and 4 microg ml(-1). At baseline and at each successive target effect-site concentration of propofol, the BIS, sedation score and haemodynamic variables were recorded. At the moment of loss of consciousness (LOC), the BIS and the effect-site concentration of propofol were noted. The relationship between propofol effect-site concentration and BIS was preserved with or without opioids. In the presence of an opioid, LOC occurred at a lower effect-site concentration of propofol and at a higher BIS50 (i.e. the BIS value associated with 50% probability of LOC), compared with placebo. Although clinically the hypnotic effect of propofol is enhanced by analgesic concentrations of mu-agonist opioids, the BIS does not show this increased hypnotic effect.

Pharmacokinetic model-driven infusion of sufentanil and midazolam during cardiac surgery: assessment of the prospective predictive accuracy and the quality of anesthesia

OBJECTIVE

To evaluate the prospective predictive accuracy and the quality of anesthesia of pharmacokinetic model-driven infusion of sufentanil and midazolam designed to establish and maintain a plasma level of drug during cardiac surgery.

DESIGN

Prospective analysis.

SETTING

Operating room at a university hospital.

PARTICIPANTS

Twenty adult patients younger than 75 years old scheduled for valvular or coronary artery bypass graft surgery.

INTERVENTIONS

Patients were anesthetized using a variable predicted concentration of sufentanil (1 to 10 ng/mL) combined with a stable predicted concentration of midazolam (100 ng/mL).

MEASUREMENTS AND MAIN RESULTS

For each patient, arterial samples were taken before (6 samples), during (2 samples), and after (2 samples) cardiopulmonary bypass (CPB). Plasma sufentanil and midazolam concentrations were measured by specific radioimmunoassay and high-performance liquid chromatography techniques. Predicted sufentanil and midazolam concentrations were derived using the data sets of Gepts et al and Maitre et al. The predictive performance, the percentage prediction error (PE), and the absolute percentage error were calculated for each sample. The bias, inaccuracy, and dispersion were assessed by determining the median of the individual medians of the prediction errors (MDPE), the median of the individual median of the absolute prediction errors (MDAPE), and the 10th and 90th percentiles of PE. For midazolam, the inaccuracy was low (MDAPE < 21%), but CPB was associated with a dilution of the measured concentration associated with a negative bias. For sufentanil, the inaccuracy was also low before CPB (MDAPE = 18%) but increased during and after CPB (MDAPE > 40%). During the whole procedure, the hemodynamic control necessitated only a few interventions.

CONCLUSIONS

Pharmacokinetic model-driven infusion of sufentanil and midazolam using the pharmacokinetic sets of Gepts et al and Maitre et al is a safe and accurate anesthetic technique before CPB in adult patients undergoing cardiac surgery when high sufentanil (1 to 10 ng/mL) and low midazolam (100 ng/mL) predicted plasma concentrations are targeted.

Interaction modeling of propofol and sufentanil on loss of consciousness

STUDY OBJECTIVES

To examine the possible pharmacodynamic interaction of propofol and sufentanil with respect to the induction of loss of consciousness.

DESIGN

Prospective, randomized, double-blinded study.

SETTING

University hospital.

PATIENTS

30 female, ASA physical status I and II patients undergoing elective gynecologic surgery.

INTERVENTIONS

Patients were allocated randomly to receive an individual combination of propofol (1, 2, 3, 4, 5, or 6 micrograms/ml) and sufentanil (0.1, 0.2, 0.3, 0.5, or 1.0 ng/ml) target blood concentrations using target-controlled infusions.

MEASUREMENTS AND MAIN RESULTS

Study endpoint was loss of consciousness, which was tested by response to verbal commands and classified as responder or nonresponder, as assessed by the anesthetist, who was blinded to the drugs' target blood concentrations. Nonlinear association (interaction) of both drugs was accomplished with logistic regression analysis using the maximum likelihood method, based principally on the hypothesis of interaction: In [p/(1-p)] = beta 0 + beta 1 x Cprop + beta 2 x Csuf + beta 3 x Cprop x Csuf with a p-value < 0.05 for coefficient estimates considered significant. In the logistic regression model, sufentanil and propofol showed no supra-additive interaction regarding loss of consciousness (p = 0.5916).

CONCLUSIONS

Our results give no evidence of additional hypnotic properties of sufentanil compared to the other fentanyl congeners, although logistic regression may be of limited value in modeling interaction of hypnotic-analgesic combinations.

Does sufentanil concentration influence isoflurane requirements during coronary artery bypass grafting?

OBJECTIVE

To search for concentration-related suppression of hemodynamic responsiveness by sufentanil.

DESIGN

Prospective, randomized, double-blind study.

SETTING

University hospital.

PARTICIPANTS

Patients undergoing elective coronary artery bypass grafting (CABG).

INTERVENTION

Patients were assigned to target effect-site sufentanil concentrations of 1.5 ng/mL (group L; n = 14), 3.0 ng/mL (group M; n = 13), or 4.5 ng/mL (group H; n = 12). Sufentanil was administered by computer-assisted continuous infusion. Isoflurane was used to maintain intraoperative hemodynamics near preoperative values.

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, the electroencephalographic spectral edge (SE95), and end-tidal isoflurane concentration (ET-ISO) were measured every 10 to 30 seconds during the prebypass period. Serum sufentanil concentration was measured at intervals. Prebypass serum sufentanil concentrations were stable, averaging 3.0 +/- 0.7, 5.1 +/- 1.1, and 7.1 +/- 1.3 ng/mL in groups L, M, and H, respectively. The groups did not differ with respect to the speed of induction, intraoperative hemodynamics, incidence of isoflurane use, or isoflurane concentrations required. ET-ISO and serum sufentanil levels were not correlated. Among seven group L patients who did not require isoflurane, the average prebypass serum sufentanil concentration ranged from 1.7 to 3.3 ng/mL.

CONCLUSION

Sufentanil does not induce concentration-related suppression of hemodynamic responsiveness over the range studied. A stable serum sufentanil concentration of 3.0 +/- 0.7 ng/mL induces the maximal opioid effect and need not be exceeded in patients undergoing CABG. A sufentanil concentration of 1.7 ng/mL provides clinically adequate anesthesia without supplementation in some premedicated patients undergoing CABG.

A comparison of clonidine with conventional preanesthetic medication in patients undergoing coronary artery bypass grafting

In this controlled study, we compared clonidine with conventional premedication in 35 patients undergoing coronary artery bypass grafting (CABG). After premedication with clonidine 5 microg/kg p.o. (Group C, n = 11), lorazepam 60 microg/kg p.o. (Group L, n = 13), or morphine 0.1 mg/kg plus scopolamine 6 microg/kg i.m. (Group M, n = 11), sedation, anxiety, and quality of premedication were graded. After the administration of sufentanil 2.0 microg/kg over 12.5 min, a computer-assisted infusion device targeted a sufentanil effect-site concentration of 0.75 ng/mL. Hemodynamic variables, end-tidal isoflurane concentration (ET-ISO), the electroencephalographic spectral edge, and the serum sufentanil concentration (SUF) were measured. There were no intergroup differences in anxiety, sedation, quality of premedication, the dose of sufentanil causing unconsciousness, or the electroencephalographic (EEG) response to induction. Intraoperative SUF was stable, with no intergroup difference. The average prebypass ET-ISO was lower in Group C than in Group M. The ET-ISO and peak ET-ISO after intense surgical stimulation were lower in Group C versus Groups L and M. Mean arterial blood pressure was lower in Group C versus Groups L and M. There were no intergroup differences in pharmacologic intervention, time to extubation, or intensive care unit stay. Clonidine produces sedation, anxiolysis, and quality of premedication comparable to conventional premedication. Compared with other drugs, clonidine does not alter the dose of sufentanil inducing unconsciousness or EEG slowing, but it uniquely reduces isoflurane requirements.

IMPLICATIONS

In patients undergoing coronary artery bypass grafting, clonidine produces sedation and relieves anxiety as effectively as conventional premedication. Clonidine does not uniquely alter the dose of sufentanil inducing unconsciousness or electroencephalographic slowing, but it significantly reduces isoflurane requirements.

Clinical utility of EEG parameters to predict loss of consciousness and response to skin incision during total intravenous anaesthesia

We studied 30 female patients undergoing elective surgery, to assess the reliability of electroencephalogram spectral edge frequency and median frequency to predict loss of consciousness and movement in response to skin incision during total intravenous anaesthesia. Each patient received a different combination of propofol (1, 2, 3, 4, 5 or 6 micrograms.ml-1) and sufentanil (0.1, 0.2, 0.3, 0.5 or 1.0 ng.ml-1) target concentrations for induction of anaesthesia using target controlled infusions, assigned randomly. In a logistic regression model, spectral edge frequency was a significant determinant of both loss of consciousness (p = 0.0006) and movement to skin incision (p = 0.0044), whereas for median frequency no significant prediction model could be established. The probabilities of 50% and 95% no response for spectral edge frequency were 13.4 Hz and 6.8 Hz, respectively. The variability of the data limited the predictive value, so that spectral edge frequency was a poor predictor and median frequency was no predictor of response in the individual patient during total intravenous propofol/sufentanil anaesthesia.

Recovery from opioid anesthesia: the clinical implication of context-sensitive half-times

The context-sensitive half-time, the time required for a 50% decrease in drug concentration, has been proposed to predict the speed of recovery after infusions of i.v. anesthetics. We studied 40 patients to compare the clinical recovery characteristics of alfentanil and sufentanil. Patients were randomly allocated to receive either sufentanil/propofol (Group 1) or alfentanil/propofol (Group 2) total i.v. anesthesia by target-controlled infusions (TCI), assuming an equipotency ratio of 500:1. After discontinuation, times to tracheal extubation and to discharge from the postanesthesia care unit were measured, as were drug concentrations up to 24 h. The TCI bias was -17.1% for sufentanil and -16.9% for alfentanil. We found no difference in mean extubation times between the groups (48.7 min in Group 1 versus 46.4 min in Group 2), whereas discharge criteria were fulfilled significantly (P = 0.039) earlier after alfentanil (99.5 min) compared with sufentanil (131.3 min). The relative decrement values to tracheal extubation were 62.1% for sufentanil and 48.0% for alfentanil, compared with 75.7% and 65.0% for discharge, respectively. Based on a difference in propofol requirements, we suggest an actual sufentanil to alfentanil equipotency ratio of 1:300. We conclude that the decay in pharmacodynamic effect is not only the result of pharmacokinetics.

IMPLICATIONS

Computer simulations may help to anticipate the clinical behavior of anesthetic drugs. In a clinical setting, we tested whether the recovery characteristics after i.v. anesthesia could be explained by a pharmaco-kinetic value, which describes the decline of drug concentrations in the body. This was not fully achieved.

Hepatic disposition of alfentanil and sufentanil in patients undergoing orthotopic liver transplantation

Alfentanil and sufentanil are used in the anesthetic management of patients undergoing orthotopic liver transplantation (OLT) and are extensively metabolized by the liver. We examined the influence of OLT on the removal of these opioids. 14 patients undergoing OLT were given either alfentanil (40 micrograms/kg intravenous [IV] bolus) or sufentanil (5 micrograms/kg IV bolus) during the induction of anesthesia, followed by infusion during surgery (1 microgram.kg-1.min-1 alfentanil or 0.01 microgram.kg-1.min-1 sufentanil) and the postoperative period (0.5 microgram.kg-1.min-1 or 0.005 microgram.kg-1.min-1). A catheter was inserted into the hepatic vein to determine the drugs' hepatic extraction coefficient and hepatic clearance. The hepatic extraction coefficient was 0.14 for alfentanil and 0.35 for sufentanil. The total and hepatic clearance of alfentanil were similar, while the hepatic clearance of sufentanil was 50% of the total clearance (P < 0.05). The total clearance of alfentanil was significantly linked to its hepatic clearance (r2 = 0.81, P < 0.001). We conclude that the total clearance of sufentanil is greater than its hepatic clearance. This difference suggests that there is extrahepatic metabolism of sufentanil in patients undergoing OLT.

Clinical pharmacokinetics of alfentanil, fentanyl and sufentanil. An update

Alfentanil, fentanyl and sufentanil are synthetic opioid analgesics acting at specific opioid receptors. These opioids are widely used as analgesics to supplement general anaesthesia for various surgical procedures or as primary anaesthetic agents in very high doses during cardiac surgery. Fentanyl and sufentanil especially are administered via infusion for long term analgesia and sedation in intensive care patients. Opioid analgesics are mainly administered using the intravenous route. However, other techniques of administration, including epidural, intrathecal, transdermal and intranasal applications, have been demonstrated. Important pharmacokinetic differences between alfentanil, fentanyl and sufentanil have been shown in many reports. Alfentanil has the most rapid analgesic onset and time to peak effect as well as the shortest distribution and elimination half-lives. The volume of distribution and total body clearance of this agent are smaller when compared with those of fentanyl and sufentanil. The pharmacokinetics of the opioid analgesics can be affected by several factors including patient age, plasma protein content, acid-base status and cardiopulmonary bypass, but not significantly by renal insufficiency or compensated hepatic dysfunction. In addition, pharmacokinetic properties can be influenced by changes in hepatic blood flow and administration of drug combinations which compete for the same plasma protein carrier or metabolising pathway. Although comparing specific pharmacokinetic parameters such as half-lives is deeply entrenched in the literature and clinical practice, simply comparing half-lives is not a rational way to select an opioid for specific requirements. Using pharmacokinetic-pharmacodynamic models, computer simulations based on changes in the effect site opioid concentration or context-sensitive half-times seem to be extremely useful for selecting an opioid on a more rational basis.

Is sufentanil a useful opioid for laryngomicroscopy?

BACKGROUND

Alfentanil is commonly used as opioid analgesic for short surgical procedures. Little is known about the usefulness of sufentanil for this purpose. We investigated the effects of alfentanil and sufentanil on haemodynamic characteristics, catecholamine levels, and adrenocorticotropic hormone (ACTH) and cortisol contents during elective laryngomicroscopy and short laryngeal surgery (LM).

METHODS

100 patients (ASA class I or II) were randomly allocated into one of four groups to receive either 10 micrograms/kg alfentanil (group I, ALF 10), 20 micrograms/kg alfentanil (group II, ALF 20), 0.25 micrograms/kg sufentanil (group III, SUF 0.25), or 0.5 micrograms/kg sufentanil (group IV, SUF 0.5) given intravenously before induction of anaesthesia. After administration of the opioid analgesic all patients received 2.0 mg/kg propofol, 15 micrograms/kg vecuronium, and 1 mg/kg succinylcholine. Anaesthesia was maintained as total intravenous anaesthesia with propofol (8 mg/ kg/h) and oxygen (33%) in air. Heart rate (HR), mean arterial pressure (MAP), adrenaline (ADR), noradrenaline (NADR), ACTH, and cortisol were measured before (baseline) and after induction of anaesthesia, at the beginning and cessation of LM, and 2 h after LM.

RESULTS

In group I (ALF 10) a significant increase in all variables was observed at the beginning and at the end of LM when compared with baseline. Two hours after LM all parameters were found to be at baseline levels. In groups II and III (ALF 20 and SUF 0.25) a significant increase in HR, MAP and catecholamine levels was observed at the end of LM compared to baseline. ACTH and cortisol contents were unchanged throughout. In group IV (SUF 0.5) HR was significantly reduced after induction, at the beginning and cessation of LM, and 2 hours following operation, whereas MAP was only decreased after induction (P < 0.05 vs. baseline). ADR, NADR, ACTH, and cortisol were similar throughout. If the duration of surgery was shorter than 12 min (20%) in group III (SUF 0.25) and 20 min (44%) in group IV (SUF 0.5), the patients had to be treated with naloxone 10 min after cessation of LM in order to antagonize respiratory depression. This side effect was not observed in group I (ALF 10) and in only one patient (4%) of group II (ALF 20) for whom surgery lasted 5 min.

CONCLUSION

Clinical recovery is achieved most rapidly with alfentanil in ultra short surgical procedures. However, if surgery is expected to be longer than about 12 min also sufentanil at a dose of 0.25 micrograms/kg seems to be useful for this kind of surgery.

The pharmacokinetics of continuous epidural sufentanil and bupivacaine infusion after thoracotomy

In a double-blind, randomized study in patients undergoing thoracic surgery the plasma and cerebrospinal fluid (CSF) pharmacokinetics of the epidural sufentanil were studied by using radioimmunoassay analysis. Sufentanil was given as an infusion (1 microgram/mL) at the lumbar (Ls; n = 11), or thoracic (Ts; n = 12) level, or epidural sufentanil combined with bupivacaine (1 mg/ mL) at the thoracic level (Tsb; n = 14). Postoperatively, the infusion was adjusted to optimize analgesia. During the infusion, the sufentanil plasma concentrations were related to the rate of epidural infusion and unrelated both to the epidural infusion regimen and to the postoperative pain scores. The elimination half-life in plasma (mean +/- SEM) was 9.9 +/- 1.7 h (Ls), 8.6 +/- 0.7 h (Ts), and 11.7 +/- 2.2 h (Tsb). The distribution volume was 15.2 +/- 3.5 l/kg (Ls), 14.8 +/- 2.4 L/kg (Ts), and 12.9 +/- 1.2 L/kg (Tsb). Total sufentanil clearance was 17.8 +/- 1.4 and 16.9 +/- 2.0 mL.kg-1.min-1 (Ls), 22.9 +/- 3.5 and 20.0 +/- 2.6 mL.kg-1.min-1 (Ts), and 22.4 +/- 3.0 and 14.5 +/- 1.3 mL.kg-1.min-1 (Tsb). The terminal elimination half-life of sufentanil in CSF was 7.2 +/- 0.6 h. During steady state the CSF concentrations were not homogeneously distributed and they were higher than those in plasma. These pharmacokinetic findings support the concept that epidural sufentanil analgesia is optimal when administered segmentally and tailored to the surgical incision.

Sufentanil plasma concentrations following lower extremity tourniquet release

STUDY OBJECTIVE

To investigate whether release of a tourniquet on the lower extremity affects plasma concentrations of sufentanil, as previously demonstrated with fentanyl and midazolam.

DESIGN

Prospective.

SETTING

University tertiary-care institution with residency program.

PATIENTS

20 ASA status I, II, and III patients undergoing total knee arthroplasty under a tourniquet using a sufentanil, nitrous oxide, relaxant regimen.

INTERVENTIONS

Each patient received sufentanil 1 to 2 micrograms/kg at induction of anesthesia and in 12.5 to 25 microgram increments as needed thereafter, until 15 minutes prior to tourniquet release.

MEASUREMENTS AND MAIN RESULTS

Plasma sufentanil concentrations were determined before tourniquet inflation, immediately before tourniquet deflation, and 1, 2, 5, 10, 20, 30, and 40 minutes following deflation. A 15% elevation of plasma sufentanil concentration above that predicted by elimination pharmacokinetics defined a secondary peak. Although the aggregate data did not indicate an overall statistically significant rise in plasma concentrations after deflation, 9 (45%) patients exhibited a secondary peak in sufentanil plasma concentration following tourniquet deflation (range of secondary peaks, 16% to 89% above predicted values). No patient experienced clinically significant respiratory depression.

CONCLUSION

Release of a tourniquet on the lower extremity may yield a detectable rise in plasma sufentanil concentration.

[Anesthetics: total intravenous anesthesia or inhalation anesthesia in neurosurgery]

In this review article the pro's and contra's of the use of either inhalational or intravenous anaesthetics for neurosurgical procedures are discussed. The objective is to stimulate thoughts concerning controversial subjects, rather than to resolve issues. It is much less complicated to approach the practice of neuroanaesthesia with a few straight forward "rules" based on laboratory measurements (such as intravenous drugs are good because they reduce CBF and ICP, whereas inhalational agents are bad because they increase CBF and ICP). It should also be noted that whereas statements about potential detrimental or beneficial effects of different anaesthetic agents are relatively common, there is a dearth of well-designed prospective studies of sufficient power to substantiate the outcome advantages or disadvantages. The choice of an anaesthetic should include more than just a consideration of the potential intracranial effects of a drug: it should also include experience with a drug and, more important a consideration of the patient as a whole.

Investigation of the pharmacokinetics and analgesic effects of an intramuscular injection of sustained-release sufentanil for postoperative pain: an open study

STUDY OBJECTIVES

To investigate the pharmacokinetics after an intramuscular (IM) injection of sufentanil in thin vegetable oil in postsurgical patients and to determine whether sustained-release IM sufentanil can provide safe and sufficient analgesia of long duration in these patients.

DESIGN

Open study.

SETTING

University hospital.

PATIENTS

10 ASA physical status I and II patients aged 18 to 65 years who were scheduled for elective surgery.

INTERVENTIONS

All patients were premedicated with lorazepam and anesthetized with a general anesthetic technique containing nitrous oxide, fentanyl, and isoflurane. As soon as significant pain [visual analog scale score of 5 or greater (range, 0 = no pain to 10 = worst pain imaginable)] occurred during the early postoperative period, the patient received an IM injection of sustained-release sufentanil.

MEASUREMENTS AND MAIN RESULTS

During the first 48 hours following surgery, blood samples were taken for determination of plasma sufentanil concentrations. Blood pressure, heart rate, respiratory rate, pain scores, and sedation scores were documented at the same time. The IM administration of sufentanil in thin vegetable oil provided sufficient pain relief, although the onset of analgesia was rather slow (+/- 1 hour). The analgesic effect was still apparent 48 hours later. Plasma concentration of sufentanil at the different time points varied from 0.021 to 0.142 ng/ml, with a mean maximal peak concentration of 0.103 ng/ml. The plasma concentration 48 hours after injection varied from 0.026 to 0.074 ng/ml.

CONCLUSIONS

Although an IM injection of sufentanil in thin vegetable oil is effective for postoperative pain relief, it is associated with wide interindividual variability in plasma concentration of sufentanil and long duration of action.

Pharmacokinetics and effects on intracranial pressure of sufentanil in head trauma patients

Ten patients with head trauma received an intravenous bolus of sufentanil (2 micrograms kg-1) followed at 30 min by infusion of sufentanil (median 150 micrograms h-1) and midazolam (median 9.0 mg h-1) over 48 h. Median (range) values of pharmacokinetic parameters for sufentanil were: t1/2,z = 16 (7-49) h; CL = 1215 (519-2550) ml min-1; CLR = 7 (2-38) ml min-1; Vss = 10.0 (6.8-24.2) 1 kg-1. Decreases in intracranial pressure (ICP) (from 16.1 +/- 1.7 to 10.8 +/- 1.3 mm Hg; P < 0.05) and mean arterial blood pressure (MAP) (from 85.5 +/- 3.9 to 80.2 +/- 4.9 mm Hg; P < 0.05) were observed within 15 min of the bolus injection of sufentanil and remained unchanged thereafter. Thus, cerebral perfusion pressure (CPP = MAP-ICP) was stable.

Optimizing sedation following major vascular surgery: a double-blind study of midazolam administered by continuous infusion

A randomized, double-blind study was undertaken to determine the dose requirements, recovery characteristics, and pharmacokinetic variables of midazolam given by continuous infusion for sedation in patients following abdominal aortic surgery. Thirty subjects, 50-75 yr, scheduled to undergo aortic reconstructive surgery, entered the study. Following a nitrous oxide-isoflurane-opioid anaesthetic technique, patients were randomly allocated to receive one of three loading doses (0.03, 0.06 or 0.1 mg.kg-1) and initial infusion rates (0.5, 1.0 or 1.5 micrograms.kg-1.min-1) of midazolam, corresponding to groups low (L), moderate (M) and high (H). The infusion of midazolam was adjusted to maintain sedation levels of "3, 4 or 5," which permitted eye opening in response to either verbal command or a light shoulder tap, using a seven-point scale ranging from "0" (awake, agitated) to "6" (asleep, non-responsive). Additionally morphine was given in increments of 2.0 mg iv prn for analgesia. On the morning after surgery, midazolam was discontinued, and the tracheas were extubated when patients were awake. Blood samples were taken during, and at increasing intervals for 48 hr following discontinuation of the infusion, and analyzed by gas chromatography. The desired level of sedation was maintained during more than 94% of the infusion period in all three groups, with a maximum of three dose adjustments per patient, for treatment which lasted 16.3 +/- 0.6 hr. There was, however, an increase in both the infusion rates and mean plasma concentrations from Group L to Group H (P < 0.05), which corresponded to an inverse relationship of morphine requirements during the period of sedation (P < 0.05, Group H vs Group L). Optimal midazolam infusion rates and resulting plasma concentrations at the times the infusions were discontinued (in parentheses) were as follows-Group L: 0.60 +/- 0.18 microgram.kg-1.min-1 (76 +/- 32 ng.mL-1), Group M: 0.90 +/- 0.52 microgram.kg-1.min-1 (133 +/- 71 ng.mL-1), and Group H: 1.34 +/- 0.69 microgram.kg-1.min-1 (206 +/- 106 ng.mL-1). Times to awakening were longer in Group H: 3.1 +/- 3.4 hr, than in Group L: 1.1 +/- 0.8 h, P < 0.05. Pharmacokinetic variables were found to be dose-independent over the range of infusion rates. Mean values were t1/2 beta = 4.4 +/- 1.5 hr, CL = 5.94 +/- 1.69 mL.min-1.kg-1, Vd = 3.13 +/- 1.07 L.kg-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Hepatic disposition of sufentanil in patients undergoing coronary bypass surgery

In order to clarify the relative contribution of the liver to the short-term disposition of sufentanil, hepatic blood flow was measured during induction of anaesthesia with a 10 micrograms/kg i.v. bolus dose of sufentanil followed by a continuous infusion of 0.3 microgram/kg/min of sufentanil. The hepatic clearance of the drug was 0.57 l/min after induction and 0.55 l/min at sternotomy, its hepatic extraction 92% and 91%, respectively. As a consequence of the high hepatic extraction, the hepatic clearance of sufentanil was closely dependent on hepatic plasma flow. Comparing the hepatic clearance of sufentanil with data from the literature for total body clearance of sufentanil, there is a significant difference of more than 0.3 l/min. It is concluded that there is evidence for a relevant extrahepatic disposition of sufentanil.

Pharmacokinetics of sufentanil in general surgical patients under different conditions of anaesthesia

The pharmacokinetics of sufentanil were studied in 56 surgical patients after an intravenous bolus of 2 micrograms kg-1, in association with neurolept analgesia or volatile anaesthetics (halothane, enflurane and isoflurane). Plasma concentrations of sufentanil were measured by radioimmunoassay. The kinetics of sufentanil were comparable under neurolept analgesia and under anaesthesia with halothane, enflurane or isoflurane. The overall mean elimination half-life was 182 min, Vdss 169 l and the plasma clearance 910 ml min-1. Except for the isoflurane subgroup, there was no significant correlation between half-life, the volume of distribution or clearance with age (24-77 years) or body weight (45-95 kg).

[Peroperative perfusion of fentanyl or sufentanil: plasma concentrations and postoperative respiratory changes]

This study was designed to assess postoperatively the time course of respiratory depression due to fentanyl (F) or sufentanil (S), as well as the plasma concentrations. Seventy patients scheduled for orthopaedic surgery lasting more than 3 hours were randomly assigned to two groups, F (n = 8) or S (n = 9). Anaesthesia was induced with etomidate (0.3 mg.kg-1), droperidol (0.15 mg.kg-1), vercuronium (0.1 mg.kg-1), a loading dose of either F (10 micrograms.kg-1) or S (1 microgram.kg-1), and maintained with 60% nitrous oxide in oxygen, and an infusion of F (6 micrograms.kg-1.h-1) or S (0.6 microgram.kg-1.h-1). Mechanical ventilation was maintained postoperatively in the recovery room until the patient could be extubated. PetCO2, SpO2, fR and F and S plasma concentrations were assessed at the end of the opioid infusion, at extubation, every hour for the first 6 hours, and thereafter every 2 h for a further 10 and 18 h. Time to extubation was the same in both groups (301 +/- 141 and 307 +/- 148 min). At the time, plasma concentrations of F and S were 1.35 +/- 0.9 ng.ml-1 and 0.14 +/- 0.07 ng.ml-1 respectively. Secondary peaks in plasma concentration (78% mean increase in comparison to the previous figure) were observed in 6 patients in group F. No similar peaks occurred in group S. Mean elimination half-life was shorter with sufentanil (457 +/- 130 min) than with fentanyl (325 +/- 132 min) (not significant). The results of this study suggest that sufentanil results less frequently in postoperative secondary peaks than fentanyl.

Comparative absorption and distribution pharmacokinetics of intravenous and epidural sufentanil for major abdominal surgery

The pharmacokinetics of absorption and distribution of a single bolus dose of sufentanil 150 micrograms for major abdominal surgery were compared in 20 patients after random intravenous or epidural administration. Samples of plasma and cerebrospinal fluid were taken at regular intervals from time zero to 180 min after injection and at the time of tracheal extubation (3.43 to 12.66h). Sufentanil was analysed by radioimmunoassay. The area under the concentration-time curve (AUC) from zero to 1h, 2h, 3h, tracheal extubation and infinity, the absorption and distribution half-lives, maximum plasma and CSF concentrations, time to the peak concentration of sufentanil, and the fraction of sufentanil that reached the central circulation after epidural administration were assessed. Except in the first sample, plasma concentrations of sufentanil were comparable between the 2 groups. The initial transfer of sufentanil from the epidural space to the systemic circulation appeared to be very rapid. Explanations for this phenomenon are given. In only 3 patients could an uptake of sufentanil from the systemic circulation into the CSF be demonstrated. The transfer of sufentanil from the epidural space into the CSF is slower than the transfer into the plasma and it varied interindividually.

Clinical use of sufentanil as an anesthetic

This review considers a few of the controversies and most recent data pertaining to the clinical intraoperative use of the potent opioid sufentanil. Although sufentanil is used extensively as the opioid component of "balanced" anesthesia, opioids themselves are not total anesthetics. Sufentanil is effective in reducing the so-called stress responses that can occur with balanced anesthesia. Although no conclusive data have shown that such reduction in stress response improves anesthetic outcome, many clinicians continue to choose sufentanil for both convenience and improved hemodynamic control. Recent pharmacokinetic modeling suggests that sufentanil would be a good choice for balanced anesthesia. Additionally, initial postoperative analgesia appears to work better when sufentanil rather than fentanyl is used intraoperatively. Although cost considerations remain important, cost analysis would suggest that, on a per-patient basis, choice of intraoperative opioid has very little effect on total hospital costs.

Postoperative patient-controlled analgesia with sufentanil: analgesic efficacy and minimum effective concentrations

Sufentanil has so far seldom been used for intravenous postoperative patient-controlled analgesia (PCA), and the resulting serum concentrations have not yet been determined. Forty ASA I-III patients recovering from major gynecological operations were investigated to evaluate analgesic efficacy, side effects, patient acceptance and threshold concentrations of sufentanil in serum during the early postoperative period, using the On-Demand Analgesia Computer (ODAC). Following an individualized intravenous loading dose of 19.1 +/- 35.7 micrograms (mean +/- 1 s.d.), sufentanil demand doses were 6 micrograms with a concurrent infusion of 1.15 micrograms/h and a maximum hourly dose of 40 micrograms/h; the lockout time was set to 1 min. The duration of PCA was 17.3 +/- 2.1 h. During this time 16 +/- 11 demands per patient were recorded, resulting in an average sufentanil consumption of 131.1 +/- 69.4 micrograms or 7.5 +/- 3.7 micrograms/h (including loading dose). analgesia was mostly judged good. Side effects were only of minor intensity. Sufentanil proved to be about 2.2 to 3.8 times as potent an analgesic as fentanyl when both analgesic effect and duration were considered. Minimum effective sufentanil serum concentration (MEC) as determined by radioimmunoassay varied greatly and could be best described by a log-normal distribution (range less than 0.01-0.56 ng/ml, median 0.024 ng/ml). Intraindividual MEC variability was slightly lower than intersubject variability (76.0 vs. 84.8%). It is concluded that sufentanil is suitable for postoperative PCA. To get into the therapeutic window for analgesia, a serum sufentanil concentration of more than 0.03 ng/ml seems to be necessary.

Alfentanil pharmacokinetics in patients undergoing abdominal aortic surgery

The pharmacokinetics of alfentanil, 300 micrograms.kg-1 IV, were determined in patients undergoing elective abdominal aortic reconstruction. The mean age (+/- SD) of the patients was 64.3 +/- 7.4 yr; their mean weight was 74.7 +/- 13.8 kg. Five patients underwent aneurysm repair and six had aortobifemoral grafting. Serum alfentanil concentrations were measured by gas-liquid chromatography in samples drawn at increasing intervals over a 24-hr period. A three-compartment model was fitted to the concentration versus time data. The volume of the central compartment and the volume of distribution at steady state (Vdss) were 0.44 +/- 0.022 and 0.63 +/- 0.32 L.kg-1, respectively. Total drug clearance was 6.4 = 1.9 ml.min-1.kg-1. The elimination half-time was 3.7 +/- 2.6 hr. Patient age was positively correlated with both Vdss and elimination half-time. There were no significant correlations between the pharmacokinetic variables and the duration of aortic cross-clamping, the duration of surgery, or the rate or total volume of IV fluids infused intraoperatively. In general surgical patients, the elimination half-time of alfentanil has been reported to be 1.2-2.0 hr. Although the elimination half-time of alfentanil was longer in patients undergoing abdominal aortic surgery, alfentanil was eliminated much faster than either fentanyl or sufentanil in this patient population.

Cardiovascular response of a continuous variable rate alfentanil infusion for abdominal aortic surgery

A prospective study was undertaken to determine the cardiovascular response of a continuous alfentanil infusion during abdominal aortic surgery (AAS). Each subject (n = 20) received a beta-blocking drug preoperatively, and was premedicated with oral lorazepam. Anaesthesia was induced with alfentanil 50 micrograms.kg-1 and thiopentone 3 mg.kg-1, and was maintained with a variable rate infusion of alfentanil and 66 per cent nitrous oxide in oxygen. During the infusion, boluses of alfentanil, 7.5 micrograms.kg-1, were administered to maintain heart rate and blood pressure within 20 per cent of awake baseline values. Haemodynamic stability during surgery was achieved with infusion rates varying between 0.5 and 2.5 micrograms.kg-1, which resulted in mean alfentanil serum concentrations ranging from 186 +/- 53 to 315 +/- 98 ng.ml-1. The mean cumulative alfentanil dose was 15.4 +/- 6.2 mg.patient-1 for surgery which lasted an average of 141 +/- 41 min. Throughout surgery, no patient required inhalational anaesthetic agents or vasoactive drugs. Fifteen of the 20 patients had perioperative Holter monitoring. No myocardial ischaemia was detected during the intraoperative period. However, there was a 33 per cent incidence of myocardial ischaemia on the first postoperative day. There were no myocardial infarcts and no deaths. We conclude that in beta-blocked patients undergoing aortic reconstructive surgery, a variable rate alfentanil infusion administered with 66 per cent nitrous oxide provides anaesthesia characterized by good haemodynamic control without the need for supplemental agents or vasoactive drugs.

Apnoea and unconsciousness after apparent recovery from alfentanil-supplemented anaesthesia

Several cases of recurrent respiratory depression progressing to apnoea and unconsciousness after apparent recovery from sufentanil have been reported recently. Alfentanil has the shortest elimination half-time of the narcotics used in anaesthesia, suggesting that it should be the least likely to cause postoperative respiratory depression. A case of recurrent unconsciousness and respiratory arrest after apparent recovery from alfentanil-isoflurane-nitrous oxide anaesthesia is reported. A total dose of 137 micrograms.kg-1 alfentanil was given over a 3.25-hr period to a 45-year-old female undergoing partial gastrectomy. Naloxone, 0.16 mg IV, rapidly restored spontaneous ventilation and consciousness. This case demonstrates that apnoea and unconsciousness can also recur after apparent recovery from alfentanil. Recovery room personnel should be aware of this phenomenon. Earlier detection may permit treatment before apnoea occurs. Patients given narcotic-supplemented anaesthesia should be monitored by capnography and/or pulse oximetry in the early postoperative period.