Multicenter study of target-controlled infusion of propofol-sufentanil or sufentanil-midazolam for coronary artery bypass graft surgery. Multicenter Study of Perioperative Ischemia (McSPI) Research Group

Influence of Cardiac Output on the Pharmacokinetics of Sufentanil in Anesthetized Pigs

BACKGROUND

Sufentanil is used for general anesthesia and analgesia. The study aim was to determine the effect of pharmacologically induced changes in cardiac output on the pharmacokinetics of sufentanil in anesthetized pigs.

METHODS

Twenty-four pigs were randomly assigned to low, high, and control cardiac output groups. Cardiac output was decreased or increased from baseline by at least 40%, or maintained within ± 10% of baseline, respectively. Sufentanil was administered as a bolus followed by a continuous infusion for 120 min. Timed arterial samples were drawn for sufentanil concentration measurements.

RESULTS

Data from 20 animals were analyzed. The cardiac outputs (means ± SD) were 2.9 ± 0.7, 5.4 ± 0.7, and 9.6 ± 1.6 l/min in the low, control, and high cardiac output groups, respectively. The parameters of the two-compartment pharmacokinetic model for these cardiac outputs were: CL1: 0.9, 1.2, and 1.7 l/min; CL2: 0.9, 3.1, and 6.9 l/min; V1: 1.6, 2.9, and 5.2 l; and V2: 27.5, 47.0, and 79.8 l, respectively. Simulated sufentanil doses to maintain a target plasma concentration of 0.5 ng/ml for 3 h were 99.5, 128.6, and 157.6 μg for cardiac outputs of 3, 5, and 7 l/min, respectively. The context-sensitive half-times for these cardiac outputs increased from 3.1 to 19.9 and 25.9 min, respectively.

CONCLUSIONS

Cardiac output influences the pharmacokinetics of sufentanil. Simulations suggest that in the case of increased cardiac output, the dose should be increased to avoid inadequate drug effect at the expense of prolonged recovery, whereas for low cardiac output the dose should be reduced, and a faster recovery may be expected.

Perioperative hypertension: new strategies for management

Perioperative hypertension is a very frequent occurrence and requires the anaesthetist to make clinical decisions regarding antihypertensive therapy, evaluation of risk, cancellation of surgery and treatment of high and low blood pressure. Perioperative management of hypertensive patients must take into account the possible consequences of left ventricular diastolic dysfunction and reduced coronary reserve.

Propofol decreases reperfusion-induced arrhythmias in a model of "border zone" between normal and ischemic-reperfused guinea pig myocardium

We examined the effect of propofol on the main mechanisms involved in ischemia/reperfusion-induced arrhythmias (i.e., spontaneous arrhythmias, conduction blocks, and dispersion of repolarization) in vitro. In a double-chamber bath, guinea pig right ventricular muscle strips were subjected to 30 min of simulated ischemia followed by 30 min of reperfusion (altered zone; AZ) and to standard conditions (normal zone; NZ). Action potential (AP) parameters were recorded in the NZ and AZ. We studied the effects of Intralipid(R) and of propofol at 10(-6), 10(-5), and 2 x 10(-5) M on the occurrence of spontaneous sustained arrhythmias, conduction blocks, and the dispersion of repolarization. In NZ, Intralipid and propofol did not significantly modify the AP parameters. Propofol, but not Intralipid, lessened the ischemia-induced decrease in AP duration (APD) at 90% of repolarization (APD(90)) and attenuated the APD dispersion around the "border zone." Propofol did not modify the occurrence of ischemia-induced arrhythmias. Propofol 10(-6) M, but not Intralipid or propofol at 10(-5) and 2 x 10(-5) M, decreased the occurrence of ischemia-induced conduction blocks. Propofol decreased the occurrence of reperfusion-induced spontaneous sustained arrhythmias. We conclude that, in vitro, propofol attenuated the ischemia-induced APD(90) dispersion around the "border zone" and decreased the occurrence of spontaneous arrhythmias related to myocardial reperfusion injury.

IMPLICATIONS

In isolated guinea pig ventricular myocardium propofol, but not Intralipid(R), attenuated the ischemia-induced shortening of action potential and, thus, the dispersion of repolarization and decreased the occurrence of spontaneous ventricular arrhythmia related to reperfusion injury. This result may be important for propofol-based anesthesia in patients at high risk for intraoperative ischemia.

Target-controlled infusion of propofol and remifentanil in cardiac anaesthesia: influence of age on predicted effect-site concentrations

BACKGROUND

Propofol-anaesthesia administrated via target-controlled infusion (TCI) has been proposed for cardiac surgery. Age-related changes in pharmacology explain why propofol dose requirement is reduced in elderly patients. However, the Marsh pharmacokinetic model incorporated in the Diprifusor propofol device does not take age into account as a covariable. In the absence of depth of anaesthesia monitoring, this limitation could cause adverse cardiovascular effects resulting from propofol overdose in older patients. We assessed the influence of age on effect-site propofol concentrations predicted by the Diprifusor and titrated to the bispectral index score (BIS) during cardiac anaesthesia.

METHODS

Forty-five patients received propofol by Diprifusor and remifentanil by software including Minto model. Propofol and remifentanil effect-site concentrations were adapted to BIS (40-60) and haemodynamic profile, respectively. The influence of age on effect-site concentrations was assessed by dividing patients into two groups: young (<65 yr) and elderly (> or =65 yr).

RESULTS

For a similar depth of anaesthesia, effect-site propofol concentrations were significantly lower in elderly patients at the different stages of cardiac surgery. The mean dose of propofol required to perform tracheal intubation was significantly lower in elderly patients. However, the overall doses of propofol were comparable in both groups. Neither effect-site remifentanil concentrations nor overall doses of remifentanil were significantly different between the two groups.

CONCLUSIONS

In cardiac anaesthesia, target concentrations of propofol must be reduced in elderly patients. Although this probably contributes to improving intraoperative haemodynamic stability, the absence of decrease in overall dose requirement of propofol suggests that this adjustment is relatively moderate.

Evaluation and optimisation of a target-controlled infusion system for administering propofol to dogs as part of a total intravenous anaesthetic technique during dental surgery

The performance of a modified target-controlled infusion system was investigated in 16 dogs undergoing routine dental work, by comparing the predicted concentrations of propofol in venous blood samples with direct measurements; the optimum targets for the induction and maintenance of anaesthesia were also identified. The performance of a target-controlled infusion system is considered clinically acceptable when the median prediction error, a measure of bias, is not greater than +/-10 to 20 per cent, and the median absolute performance error, a measure of the accuracy, is not greater than 20 to 30 per cent. The results fell within these limits indicating that the system performed adequately. The optimal induction target was 3 microg/ml, and anaesthesia of adequate depth and satisfactory quality was achieved with maintenance targets of between 2.5 and 4.7 microg/ml propofol. The system was easy to use and the quality of anaesthesia was adequate for dental work.

Total intravenous anesthesia with a propofol-ketamine combination during coronary artery surgery

OBJECTIVE

To evaluate the cardiovascular effects of a propofol-ketamine combination in patients undergoing coronary artery surgery.

DESIGN

Prospective, randomized study.

SETTING

Tertiary care teaching hospital, single center.

PARTICIPANTS

Seventy-eight adult patients.

INTERVENTIONS

Patients were randomly allocated to receive propofol-ketamine for induction and maintenance of anesthesia (n = 36) or fentanyl-enflurane (controls, n = 42).

MEASUREMENTS AND MAIN RESULTS

Hemodynamics and other variables were recorded during and after surgery and for 24 hours in the intensive care unit. Before cardiopulmonary bypass (CPB), there was similar incidence of treatment for hypotension (42% of patients in both groups), tachycardia (propofol-ketamine, 6%; controls, 5%), and myocardial ischemia (propofol-ketamine, 3%; controls, 12%). In the propofol-ketamine group, there was a decreased requirement for inotropic agents after CPB (22% of patients) compared with controls (49% of patients; p = 0.02). There was a reduced incidence of myocardial infarctions (creatine kinase myocardial band >133 U/L) in the propofol-ketamine group compared with the control group (0% v 14%; p = 0.02; Fisher's exact test). Patients in the propofol-ketamine group were more likely to have their tracheas extubated within 8 hours of arrival in the intensive care unit compared with controls (33% v 7%; p = 0.01; Cochran-Mantel-Haenzel test).

CONCLUSIONS

The propofol-ketamine combination was associated with a similar incidence of pre-CPB hypotension and ischemia, a decreased need for inotropes after CPB, an earlier time to tracheal extubation, and a reduced incidence of myocardial infarctions compared with controls.

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.

Midazolam-sufentanil vs sufentanil-enflurane for induction of anaesthesia for CABG surgery

PURPOSE

To compare the effects of midazolam-sufentanil (Group I) and sufentanil-enflurane (Group II) anaesthesia on myocardial oxygenation and metabolism in patients with preserved ventricular function undergoing CABG surgery.

METHODS

Patients randomized to Group I (n = 16) received midazolam 0.3 mg.kg-1 at induction of anaesthesia, 0.15 mg.kg-1 after tracheal intubation, followed by an infusion of 2.5-10.0 micrograms.kg-1.min-1. Supplemental sufentanil (cumulative maximum of 5 micrograms.kg-1) was given for adverse haemodynamic responses. Group II (n = 16) received 5 micrograms.kg-1 sufentanil at induction. Additional sufentanil (maximum 5 micrograms.kg-1), and enflurane (0-3% inspired concentration) were administered for adverse haemodynamic responses. Haemodynamics, myocardial oxygen consumption (MVO2), and lactate extraction were determined at the following times: I) awake (AWA), 2) after induction (IND), and 3) after tracheal intubation (ETT).

RESULTS

Systemic haemodynamics and myocardial metabolism were similar at AWA. Heart rate response was attenuated and MVO2 reduced in Group I at IND (P < 0.05). Following AWA, myocardial lactate production (MLP) occurred more frequently in Group II vs Group I patients (9/16 vs 2/16) and at more individual measurement points (Group II: 10/64 vs Group I: 3/64). Myocardial lactate flux demonstrated a deleterious trend in Group II at ETT.

CONCLUSIONS

Compared with sufentanil-enflurane, midazolam-sufentanil anaesthesia resulted in comparable and acceptable haemodynamics and myocardial oxygenation in CABG patients.

Advances in anesthesia for cardiac surgery: an overview for the 1990s

Anesthetic care for patients undergoing cardiac surgery has changed dramatically in the past 10 years. Examples of such change include same-day admissions, "fast-track" protocols, selective use of pulmonary artery catheters, transesophageal echocardiography, and the introduction of new drugs such as phosphodiesterase inhibitors and antifibrinolytic agents. Under pressure from our peers and those funding health care, we are making major efforts to reduce costs and the length of hospitalization while maintaining high quality of care.