Midazolam sedation following open heart surgery

A dose-ranging study of midazolam for postoperative sedation of patients: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To evaluate the dose range, efficacy, and safety of midazolam for induction of sedation of mechanically ventilated postoperative patients in the intensive care unit.

DESIGN

A randomized, double-blind, placebo-controlled study.

SETTING

Thirteen intensive care units in Japan.

PATIENTS

We included 98 patients undergoing general surgery who were ASA physical status I-III. The following inclusion criteria were applied to the patients after surgery: under mechanical ventilation, sedation level 2 or 3 on the Ramsay Sedation Scale, and any pain level but 4 on the Pybus and Torda Pain Scale.

MEASUREMENTS AND RESULTS

Of the 98 patients initially enrolled in the study, 95 patients received one of the study medications: placebo (n = 24), 0.015 mg/kg midazolam (n = 21), 0.03 mg/kg midazolam (n = 26), or 0.06 mg/kg midazolam (n = 24). Level of sedation was assessed by using the Ramsay Sedation Scale before and 10 mins after medication. The proportions of patients with sedation level 4 or deeper after medication were 4.3%, 14.3%, 52.0%, and 90.9% in the placebo and the midazolam 0.015 mg/kg, 0.03 mg/kg, and 0.06 mg/kg groups, respectively. Safety was assessed by routine monitoring of body functions and monitoring for adverse events. Although midazolam dose-dependently reduced mean systolic arterial pressure, the changes in this variable were small; only one or two patients in each treatment group had decreases in systolic arterial pressure of >20%. No clear dose dependency was found for changes in other body functions measured in the intensive care unit.

CONCLUSION

The proportion of patients who achieved a satisfactory level of sedation increased with an increasing dose of midazolam. Intravenous bolus injection of midazolam also dose-dependently reduced mean systolic arterial pressure. This study indicated that, balancing sedative efficacy and safety, from 0.03 to 0.06 mg/kg of midazolam provides relatively safe sedation in postoperative patients.

[Sedation induced by midazolam in intensive care: pharmacologic and pharmacokinetic aspects]

OBJECTIVE

Review on midazolam in order to optimize drug utilisation and therapeutic monitoring.

DATA SOURCES

Research of English or French articles published until August 2001, using Medline database. The key words were: midazolam, pharmacokinetics, pharmacodynamic, sedation, drug interaction.

STUDY SELECTION

Original articles, clinical cases and letters to the Editor were selected. Animal studies were excluded.

DATA EXTRACTION

The articles were analysed according to their interest in midazolam clinical practice.

DATA SYNTHESIS

Midazolam is a benzodiazepine widely used in intensive care unit, as a sedative, anxiety-relieving, and amnesic drug. Midazolam could be used in patients with cardiac, or respiratory failure, and in neurosurgery. A great interindividual variability on pharmacokinetic and pharmacodynamic response was observed. In intensive care patients, elimination half-life is known to be widely increased. Midazolam is metabolised by hepatic microsomes. The major metabolite is the 1-hydroxymidazolam, which is pharmacologically active. A prolonged sedation due to an accumulation of conjugated metabolite was observed in renal failure patients. Enzymatic inductors or inhibitors could influence pharmacokinetics and pharmacodynamic effects of midazolam.

CONCLUSION

According to midazolam pharmacokinetic and pharmacodynamic variability, an individual dosage adjustment is essential for long-term sedation. Target controlled sedation could be a mean to limit the variability and to reach quickly the pharmacodynamic effect.

Benzodiazepines in the intensive care unit

The effects of BZ drugs result from interaction at the GABAA receptor within the CNS, producing anxiolysis, hypnosis, and amnesia in a dose-dependent fashion. These sedative effects are best titrated to reproducible clinical endpoints, using scoring systems such as the Ramsay scale. All BZs exhibit similar pharmacologic effects, but the important differences in pharmacokinetics and pharmacodynamics should be recognized to use these drugs safely and effectively within the ICU. Diazepam is the classic anxiolytic, amnestic, and sedative agent, but the presence of long-acting active metabolites that depend on the kidneys for elimination limits its use in many ICU patients. Lorazepam is the most potent BZ used in the ICU; it has stable pharmacokinetics and relatively low cost. This drug is best reserved for situations in which rapid onset is not essential and long-term sedation is anticipated. Midazolam has the shortest t1/2 of the commonly used BZs, generates few active metabolites, and is water soluble at physiologic pH. Thus, it is well suited for continuous infusion in the ICU, and the recent introduction of generic formulations of midazolam has decreased the drug-acquisition cost for many hospitals. Optimal sedation for ICU patients often requires BZ and concomitant therapy with drugs such as haloperidol, dexmedetomidine, opioids, and so forth, to reduce untoward side effects and, perhaps, overall drug costs. Flumazenil, a specific BZ antagonist, can be used for diagnostic or therapeutic reversal of BZ agonists when appropriate. Most experienced intensivists recommend an individualized approach to sedation and titration of anxiolysis to maximize efficacy, minimize side effects, and optimize cost effectiveness in the ICU. New CNS monitors of the EEG, such as the BIS or entropy EEG monitors, may refine titration algorithms further in the near future.

Sedation in the intensive care unit

OBJECTIVE

To describe the goals of sedative use in the intensive care unit and review the pharmacology of commonly used sedative drugs as well as to review pertinent publications in the literature concerning the comparative pharmacology of these drugs, with emphasis on outcomes related to sedation and comparative pharmacoeconomics.

DATA SOURCES

Publications in the scientific literature.

DATA EXTRACTION

Computer search of the literature with selection of representative articles.

SYNTHESIS

Proper choice and use of sedative drugs is based on knowledge of the pharmacology of commonly used agents and is an essential component of caring for patients in the intensive care unit. The large variability in pharmacokinetics and pharmacodynamics in the critically ill make it difficult to directly compare agents. Midazolam provides rapid and reliable amnesia, even when administered for low levels of sedation. Propofol may be useful when deeper levels of sedation and more rapid awakening are required. Lorazepam can be used for long-term sedation in more stable patients if rapidity of effect is not required. Further investigation in assessment of depth of sedation in the critically ill is needed. Continued study of costs, side effects, and appropriate dosing strategies of all sedative agents is needed to answer questions not sufficiently addressed in the current literature.

CONCLUSION

An individualized approach to sedation based on knowledge of drug pharmacology is needed because of confounding variables including concurrent patient illness, depth of sedation, and concomitant use of analgesic agents. (Crit Care Med 2000; 28:854-866)

Adjuncts to analgesia. Sedation and neuromuscular blockade

This article provides an overview of some of the current issues involved in sedation and anxiolysis in the intensive care unit. The problems involved in trying to monitor sedation levels are discussed, as are some of the newer options available for physiologic monitoring of the central nervous system. The problem of abnormal mental states in the intensive care unit and the range of antidepressant therapy now available are also covered. The importance of sleep deprivation and the properties of the neuromuscular blockers are also discussed.

Efficacy and safety of a new protocol for continuous infusion of midazolam and fentanyl and its effects on patient distress during electrophysiological studies

Electrophysiological studies are often distressing for patients. We devised a regime of continuous infusion of midazolam and fentanyl during electrophysiological studies without the presence of a specialist anaesthetist. The effects on key hemodynamic and respiratory variables and level of sedation were evaluated in detail in the first 775 patients. The safety of this practice was evaluated in 1,344 consecutive patients. Doses were calculated according to patients' weight and age. A mean total dose of 26 mg of midazolam and 115 mcg of fentanyl were infused. Satisfactory sedation was achieved in 97% of patients. The mean duration of procedure was 188 +/- 90 minutes. Complete amnesia of the procedure was obtained in 87% of patients. Sedation caused clinically insignificant changes in respiratory rate, oxygen saturation, end-tidal CO2 and blood pressure. There were no major complications related to sedation. Upper airway obstruction, usually minor, occurred in 42% and some restlessness in 20% of sedated patients. The assistance of a specialist anesthetist was required in 0.3% of sedated patients for management of restlessness, hypoventilation, or obstructive sleep apnea. The amount of distress experienced by sedated patients (n = 775) was significantly less compared to a previous series of nonsedated patients (n = 775) undergoing electrophysiological studies (P < 0.001). The degree of distress experienced by patients during electrophysiological studies can be reduced significantly by sedation with intravenous midazolam and fentanyl. Continuous infusion is an efficient, safe, and effective way of administering midazolam and fentanyl.

Propofol or midazolam for sedation and early extubation following cardiac surgery

PURPOSE

The purpose of this randomized, double-blind study was to evaluate the efficacy of midazolam and propofol for postoperative sedation and early extubation following cardiac surgery.

METHODS

ASA physical status II-III patients scheduled to undergo elective first-time cardiac surgery with an ejection fraction > 45% were eligible. All patients received a standardized sufentanil/isoflurane anaesthesia. During cardiopulmonary bypass 100 micrograms.kg-1.min-1 propofol was substituted for isoflurane. Upon arrival in the Intensive Care Unit (ICU), patients were randomized to either 10 micrograms.kg-1.min-1 propofol (n = 21) or 0.25 microgram.kg-1.min-1 midazolam (n = 20). Infusion rates were adjusted to maintain sedation within a predetermined range (Ramsay 2-4). The infusion was terminated after four hours. Patients were weaned from mechanical ventilation and their tracheas extubated when Haemodynamic stability, haemostasis, normothermia and mental orientation were confirmed. Haemodynamic measurements, arterial blood gas tensions and pulmonary function tests were recorded at specified times.

RESULTS

There were no differences between the two groups for the time spent at each level of sedation, number of infusion rate adjustments, amount of analgesic and vasoactive drugs, times to awakening and extubation. The costs of propofol were higher than those of midazolam. There were no differences in haemodynamic values, arterial blood gas tensions and pulmonary function.

CONCLUSION

We conclude that midazolam and propofol are safe and effective sedative agents permitting early extubation in this selected cardiac patient population but propofol costs were higher.

Pharmacokinetics and pharmacodynamics of midazolam given via continuous intravenous infusion in intensive care units

Critically ill patients often benefit from sedation to optimize their care and their ventilatory support. Ideally, incremental doses of a drug are administered to produce the desired level of sedation without toxicity or overdose. Because metabolism and elimination of drugs are often altered in critically ill patients, knowledge of the pharmacokinetics of sedative hypnotics is essential to ensure their appropriate selection and administration. Furthermore, the administration of sedatives via continuous infusion minimizes fluctuations in drug concentrations and permits more consistent control of the patient's agitation and anxiety. Physician preference and the patient's individual requirements and underlying diseases are the primary determinants for the selection of a given sedative. Benzodiazepines are the most commonly used sedatives in critical care. Midazolam is readily distinguished from other benzodiazepines because of its rapid onset and short duration of action, low incidence of thrombophlebitis and pain on injection, and minimal cardiovascular and respiratory effects. The physiochemical properties of midazolam allow for enhanced water solubility, which limits physicochemical incompatibilities. These properties make midazolam a valuable sedative that can be given via continuous intravenous infusion in the intensive care unit.

An investigation of the potential morphine sparing effect of midazolam

The effect of a bolus and continuous infusion of midazolam on postoperative morphine consumption was assessed in a placebo-controlled, double-blind, randomly allocated trial of 50 patients undergoing elective abdominal hysterectomy. Patients in the trial group received a bolus dose of midazolam 5 mg.70 kg-1 at induction followed by an infusion at a rate of 1 mg.70 kg-1.h-1 over the next 48 h. Morphine consumption in the midazolam group was significantly lower in the first 12 h postoperatively (p < 0.02) but there was no significant difference between the two groups thereafter. Patients in the midazolam treated group had lower pain scores over the first 24 h. Also, a significantly greater number of patients in the midazolam group required no antiemetic medication over the 48 h study period (p < 0.05). Assessment of sedation revealed no significant difference between groups. We conclude that low dose midazolam has a significant, but short-lived, morphine sparing effect.

Comparison of propofol and midazolam for sedation in intensive care unit patients

OBJECTIVES

To evaluate the comparative safety and effectiveness of intravenous infusion of propofol or midazolam when used for 12 to 24 hrs of sedation and to evaluate the quality of sedation during stimulation.

DESIGN

An open, comparative, prospective, randomized study.

SETTING

Surgical intensive care unit (ICU) in a university hospital.

PATIENTS

Postoperative, intubated, general surgical, and orthopedic patients requiring mechanical ventilation (n = 60).

INTERVENTIONS

None.

MEASUREMENTS

Assessments were made at baseline (0 time), 5, 10, 15, 30, 45, and 60 mins; at 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 hrs; and at the end of sedation. The assessments included systolic, mean, and diastolic blood pressures, heart rate, two-lead electrocardiogram, pulse oximetry oxygen saturation, FIO2, end-tidal CO2, respiratory rate, ventilator rate, tidal volume, and sedation scale. Vital signs and the sedation scale were obtained at 30, 60, and 90 mins and at 2, 4, 12, and 24 hrs after the end of sedation. At approximately 8 hrs and 24 hrs (or at the end of sedation), the patient's CO2 production was calculated over a 5-min interval. Every 4 hrs, the nurse would summarize and rate patient response during stimulation as well as the overall rating of the sedation and patient ability to tolerate the ICU setting.

MAIN RESULTS

There were no significant differences in pulse oximetry, arterial blood gas values, or respiratory measurements during sedation with propofol or midazolam. The mean heart rate was slower in the propofol group throughout the sedation and postsedation periods. The rating of sedation and tolerance of the ICU environment were significantly better for the propofol-treated group. Postsedation, the propofol group woke up faster on discontinuation of the sedative.

CONCLUSIONS

Propofol was as safe and as efficacious as midazolam for continuous intravenous sedation. The quality of sedation was better in the propofol group.

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)

Anaesthesia for coronary artery surgery--a plea for a goal-directed approach

The purpose of the current literature review was to examine whether changes in current anaesthetic techniques are warranted for patients undergoing coronary artery surgery in light of recent information presented in the literature. The objectives of a cardiac anaesthetic technique are to maintain haemodynamic stability and myocardial oxygen balance, minimize the incidence and severity of ischaemic episodes, be aware of cardiopulmonary bypass-induced pharmacokinetic changes, and facilitate early tracheal extubation if appropriate. Many techniques have been utilized. Provided attention is paid to the details of managing myocardial oxygen supply and demand, none has emerged as superior in preventing intraoperative myocardial ischaemia. Silent myocardial ischaemia (i.e., ischaemia occurring in the absence of haemodynamic aberrations) is common throughout the perioperative period and may occur even in the presence of an appropriately used anaesthetic technique. The incidence and severity appear to be greatest in the postoperative period when the effects of anaesthesia are dissipating. The use of high-dose opioid anaesthesia may no longer be the most appropriate technique to facilitate the anaesthetic objectives. The role of pain management in altering the incidence of ischaemia requires further study. Increased waiting lists for cardiac surgery and ever-diminishing resources should prompt a re-evaluation of early extubation (i.e., within eight hours) as a method of improving utilization of scarce ICU resources. It is suggested that this should be possible with currently available agents to achieve the anaesthetic objectives. Future suggestions for research in this area are made.

The effects of midazolam on the EEG during sedation of critically ill patients

Patients who require mechanical ventilation are often sedated with midazolam. As clinical signs of sedation are often confusing or nonexistent, and there are few adverse side effects when large doses are infused over a period of days, substantial drug accumulation can result in these critically ill patients, despite the short half-life of midazolam. An objective monitor of sedation would help maintain sedation at a constant level despite changing pharmacokinetic values in patients. We undertook this study to describe the electroencephalographic changes which occur with intravenous midazolam in critically ill patients, and to determine if a relationship exists between these changes and the depth of sedation as measured using a clinical scoring method. A series of 31 critically ill patients who required intravenous midazolam during mechanical ventilation were studied. Four different levels of sedation were defined ranging from execution of verbal commands to no response to suctioning through the tracheal tube or sternal rub. Electroencephalographic recordings were obtained in patients on a daily basis and a concurrent sedation level was determined. High frequency electroencephalogram activity decreased as sedation level increased. This was reflected in decreases in the spectral edge (17.61 to 10.56 Hz (p = 0.0024)), the median frequency (4.27 to 2.56 Hz (p = 0.0278)), and the logarithm of the absolute power in the beta 1 (p = 0.0012), and beta 2 (p < 0.0001) bands. An incidental finding of asymmetry in power between right and left frontal electrodes was observed, with right-sided power being 9-18% greater (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of a cardiac surgical recovery area on the timing of extubation

The anesthetic and postoperative management of cardiac surgical patients was modified to achieve an early return to spontaneous ventilation. A total of 278 patients were studied to determine the effect of this change. Patients in group I (n = 198) were managed in a cardiac surgical recovery area according to the new policy. Group II (n = 80) was a comparable group of patients operated upon before this change. The median duration of postoperative ventilation was reduced from 5 hours in group II to 1 hour in group I, and the time to extubation was reduced from 7 hours to 2 hours, respectively. There were no major postoperative complications resulting from this change. The factors that influence the duration of postoperative ventilation are discussed.

Propofol vs midazolam in short-, medium-, and long-term sedation of critically ill patients. A cost-benefit analysis

The purpose of this study was to evaluate and compare the clinical effects, safety, and economic cost of propofol and midazolam in the sedation of patients undergoing mechanical ventilation in the ICU. Eighty-eight critically ill patients were studied and randomly allocated to receive short-term (less than 24 h), medium-term (24 h to 7 days), and prolonged (more than 7 days) continuous sedation with propofol (n = 46) or midazolam (n = 42). Mean doses required were 2.36 mg/kg/h for propofol and 0.17 mg/kg/h for midazolam. Patients in the group receiving propofol showed a percentage of hours of sedation at the desired level (grade 2, 3, 4, or 5 on the Ramsay scale) of 93 percent, compared with 82 percent (p < 0.05) in the group receiving midazolam. Both agents were considered safe with respect to the induction of adverse reactions during their use in prolonged sedation. Recovery after interrupting sedation was significantly faster in patients treated with propofol than in those sedated with midazolam (p < 0.05). Recovery of total consciousness was predictable according to sedation time in propofol-treated subgroups (r = 0.98, 0.88, and 0.92, respectively), while this correlation was not observed in the midazolam-treated group. In the subgroup with sedation of less than 24 h, propofol provided a cost savings of approximately 2,000 pesetas (pts) per patient, due to shorter stays in the ICU. We conclude that propofol is a sedative agent with the same safety, higher clinical effectiveness, and a better cost-benefit ratio than midazolam in the continuous sedation of critically ill patients.

The use of midazolam versus propofol for short-term sedation following coronary artery bypass grafting

Midazolam and propofol were compared in an open randomized study for postoperative sedation during 12 h of mechanical ventilation in 40 patients following coronary artery bypass grafting. After an intravenous loading dose of midazolam (50 micrograms.kg-1) or propofol (500 micrograms.kg-1), a titrated continuous infusion was administered of midazolam (mean dose 38.1 micrograms.kg-1.h-1 (SEM 2.6)) or propofol (mean dose 909 micrograms.kg-1.h-1 (SEM 100)) together with a narcotic analgesic infusion. During mechanical ventilation midazolam and propofol produced a similar quality of sedation, but recovery (midazolam 66 min (SEM 16); propofol 24 min (SEM 7)) and weaning from the ventilator (midazolam 243 min (SEM 44); propofol 154 min (SEM 33)) where faster with propofol. In the 2 groups administration of an intravenous loading dose caused a significant decrease in mean arterial pressure but hemodynamic tolerance during maintenance infusion was good.

Propofol sedation after open heart surgery. A clinical and pharmacokinetic study

One hundred adult patients who required mechanical ventilation after open heart surgery for coronary revascularisation were studied. All received a standard premedication and a high dose opioid anaesthetic. On arrival in the intensive care unit they were allocated randomly to receive either propofol or midazolam to maintain sedation within a predetermined range. Patients who received propofol underwent extubation of the trachea, using standard criteria, after a mean time (log-transformed) of 7.6 minutes after sedation for approximately 17 hours. The corresponding time was 125 minutes in those given midazolam. There were significantly higher morphine requirements during sedation, and higher arterial carbon dioxide tensions 30 minutes after extubation of the trachea, in patients who received midazolam. Pharmacokinetic analysis in 20 patients showed that the elimination half-life of propofol was prolonged (470 minutes) and clearance was reduced (1.14 litres/minute) compared with subjects who had not undergone cardiopulmonary bypass. The rapid clinical recovery was reflected in a rapid redistribution half-life (13.4 minutes), but this was also longer than the redistribution time of 2-4 minutes in other patients.

Double-blind study of the reversal of midazolam-induced sedation in the intensive care unit with flumazenil (Ro 15-1788): effect on weaning from ventilation

Midazolam (0.1-0.2 mg/kg/hr) and morphine (2 mg/hr) were given by carefully regulated continuous intravenous infusions to thirty patients who required sedation, analgesia and ventilation for between twelve and twenty-four hours in the Intensive Care Unit. The midazolam and morphine infusions were stopped at the end of the period of sedation required and the efficacy of placebo of flumazenil in reversing the sedative effects of midazolam was compared in this double-blind randomised parallel group study. Patients receiving flumazenil were less sedated (P less than 0.05), able to obey commands (P less than 0.05), weaned from ventilation (P less than 0.05) and extubated (P less than 0.05) significantly earlier than those receiving placebo.

Continuous infusion of midazolam during anaesthesia and postoperative sedation after maxillofacial surgery

The clinical effects and pharmacokinetics of 24 h infusion of midazolam (MDZ) during major maxillofacial surgery and postoperative observation in an Intensive Care Unit (ICU) were studied in 20 patients. During anaesthesia, infusion of MDZ at 5 mg/h combined with 67% nitrous oxide, 1.8 (s.d. = 0.8) mg of fentanyl, and 26.5 (s.d. = 11.4) mg of vecuronium, adequately suppressed clinical responses to surgical nociceptive stimuli. Postoperatively, infusion of MDZ was continued in the ICU at 5 mg/h until 9 a.m. of the first postoperative day for sedation of the intubated but spontaneously breathing patients. The depth of sedation in the ICU was scored from 1-5 (1 = "awake and tense", 5 = "unable to communicate"). During infusion the sedation score decreased from 3.8 after ICU arrival to 2.2 at 8 a.m. of the first postoperative day. Neither ventilatory nor circulatory depression were observed. After cessation of MDZ, recovery from sedation was fast. The degree of amnesia was low. During constant rate infusion no increase in plasma concentration of either MDZ or metabolites occurred. T1/2 beta of MDZ after cessation was 125 min (range 90-320) and its total body clearance was 10.5 ml/kg/min (s.d. = 3.1). The volume of distribution, clearance and T1/2 beta were significantly longer in women than in men. It was concluded that 24 h of MDZ infusion at 5 mg/h caused satisfactory ICU sedation with fast recovery, but that individual tailoring of the infusion rate may still improve the quality of sedation.