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

Enhanced recovery after surgery (ERAS) for vascular surgery: an evidence map and scoping review

BACKGROUND

Enhanced recovery after surgery (ERAS) interventions aim to improve patient outcomes. Vascular surgery patients have unique requirements and it is unclear which ERAS interventions are supported by an evidence base.

METHODS

We conducted a scoping review to identify ERAS randomized controlled trials (RCTs) published in the biomedical or nursing literature. We assessed interventions for applicability to vascular surgery and differentiated interventions given at preadmission, preoperative, intraoperative, and postoperative surgery stages. We documented the research in an evidence map.

RESULTS

We identified 76 relevant RCTs. Interventions were mostly administered in preoperative (23 RCTs; 30%) or intraoperative surgery stages (35 RCTs; 46%). The majority of studies reported mortality outcomes (44 RCTs; 58%), but hospital (27 RCTs; 35%) and intensive care unit (9 RCTs; 12%) length of stay outcomes were less consistently described.

CONCLUSION

The ERAS evidence base is growing but contains gaps. Research on preadmission interventions and more consistent reporting of key outcomes is needed.

Validation of a consciousness level scale for palliative care

The main objective of this study is to validate a Consciousness Scale for palliative care. The scale was named Consciousness Scale for palliative care (CSPC). The validation had two phases: 1) face validity--the scale was assessed by seven healthcare professionals, both doctors and nurses, experienced in palliative care; 2) reliability and construct validity--performed by four investigators, two nurses and two doctors. The construct validation was performed by comparing the CSPC with a Visual Analogue Scale (VAS) of 100 mm, anchored in the terms 'awake' and 'unarousable', and then with the Glasgow Coma Scale (GCS). In this study, all four observers completed 44 periods of observation relative to 38 patients resulting in a total of 176 observations. In the phase of face validation, there were no discrepancies in relation to the issue: the scale provides measures for measurement; the scale can be useful to clinical practice; the scale can improve communication among professionals and the scale is easy to use. As a measure of internal consistency, Cronbach's alpha was found to be very high (0.99). The inter-rater reliability was also very high with an intraclass correlation coefficient of 0.99 (P < 0.001). The correlation of the CSPC to the VAS was 0.94 (P < 0.001) and the CSPC to the GCS was -0.82 (P < 0.001). The CSPC can be a very useful tool for assessing consciousness in palliative care patients. It is very ease to use, not time consuming and can be used with minimal training. Communication between professionals can be improved in the clinical setting and in the research environment.

Kinetics and EEG Effects of Midazolam during and after 1-Minute, 1-Hour, and 3-Hour Intravenous Infusions

The objective of this study was to evaluate the kinetics and dynamics of midazolam when administered by three different infusion schemes, using electroencephalography to measure pharmacodynamic effects. In a three-way crossover study, 8 volunteers received midazolam (0.1 mg/kg) by constant-rate intravenous infusion. The durations of midazolam infusions for the three trials were 1 minute, 1 hour, and 3 hours. Plasma midazolam concentrations and electroencephalographic (EEG) activity in the 13- to 30-Hz range were monitored for 24 hours. Based on separate analysis of each subject-trial, mean values for volume of distribution and distribution or elimination half-life did not significantly vary. Central compartment volume and clearance differed among the three midazolam infusion trials; however, the magnitude of change was small. EEG activity in the 13- to 30-Hz range significantly increased for all three midazolam infusion trials. Plots of midazolam plasma concentration versus pharmacodynamic EEG effect for the 1-hour and 3-hour infusion trials did not reveal evidence of either counterclockwise or clockwise hysteresis. Plots from the 1-minute infusion trial demonstrated counterclockwise hysteresis, consistent with an equilibration effect-site delay. This was incorporated into a kinetic-dynamic model in which hypothetical effect-site concentration was related to pharmacodynamic EEG effect via the sigmoid E(max) model. Analysis of all three infusion trials together yielded the following mean estimates: maximum EEG effect, 16.3% over baseline; 50% maximum effective concentration, 31 ng/mL; and an apparent rate constant for drug disappearance from the effect compartment which approached infinity. Despite the delay in effect onset during the 1-minute midazolam infusion, midazolam infusions in duration of up to 3 hours produce CNS sedation without evidence of tolerance.

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 assessment in critically ill adults

OBJECTIVE

To review methods for assessing sedation in critically ill adults, discuss their impact on patient outcomes, and provide recommendations for implementing these methods into clinical practice in the intensive care unit (ICU).

DATA SOURCES

A computerized search of MEDLINE from 1980 through June 2000 and a manual search of abstracts presented at recent critical care meetings were performed.

STUDY SELECTION AND DATA EXTRACTION

Sedation assessment tools that have been used to titrate therapy in adult, critically ill patients were identified. Special emphasis was placed on sedation assessment instruments that have been prospectively validated. Objective methods that have been used to assess sedation therapy were also identified.

DATA SYNTHESIS

Twenty-three adult sedation assessment instruments were identified. Few scales have been prospectively evaluated for validity (n = 6) or reliability (n = 7). Other methods of sedation assessment were identified (e.g., bispectral index monitor); however, most of these methods have only been studied in small subsets of critically ill patients.

CONCLUSIONS

Incorporation of sedation assessment into ICU clinical practice may improve patient care. These sedation assessment instruments must be further evaluated to determine their impact on quality of care and ICU length of stay.

Anxiety, delirium, and pain in the intensive care unit

Anxiety, agitation, delirium, and pain are common findings in the ICU. These unhealthy states may lead to increased irritability, discomfort, hypertension, tachycardia, cardiac ischemia, harmful motor activity, and psychologic disquiet for the patient. The appropriate treatment of these conditions may lead to decreased morbidity and mortality in the critically ill patient. Unfortunately, the management of anxiety, agitation, delirium, and pain in the intensive care unit is not ideal. Many patients interviewed after an ICU stay rate their pain control as poor and their memories of their stay as unpleasant. Furthermore, many caregivers lack sufficient understanding of the appropriate or indicated uses of drugs to allay patients' fears and pain. The use of suitable protocols for the proper titration of sedation of mechanically ventilated patients and monitoring of the level of sedation in ventilated patients may decrease the amount of time that patients are ventilated and may alleviate some of the emotional stresses of recall of painful procedures or uncomfortable mechanical ventilation. Future research into protocols for the care of the critically ill patient can enhance the overall well-being of these patients.

Kinetics and dynamics of lorazepam during and after continuous intravenous infusion

OBJECTIVE

To evaluate the kinetics and dynamics of lorazepam during administration as a bolus plus an infusion, using electroencephalography as a pharmacodynamic end point.

METHODS

Nine volunteers received a 2-mg bolus loading dose of lorazepam, coincident with the start of a 2 microg/kg/hr zero-order infusion. The infusion was stopped after 4 hrs. Plasma lorazepam concentrations and electroencephalographic activity in the 13- to 30-Hz range were monitored for 24 hrs.

RESULTS

The bolus-plus-infusion scheme rapidly produced plasma lorazepam concentrations that were close to those predicted to be achieved at true steady state. Mean kinetic values for lorazepam were as follows: volume of distribution, 126 L; elimination half-life, 13.8 hrs; and clearance, 109 mL/min. Electroencephalographic effects were maximal 0.5 hr after the loading dose, were maintained essentially constant during infusion, and then declined in parallel with plasma concentrations after the infusion was terminated. There was no evidence of tolerance. Plots of pharmacodynamic electroencephalographic effect vs. plasma lorazepam concentration demonstrated counterclockwise hysteresis, consistent with an effect-site equilibration delay. This was incorporated into a kinetic-dynamic model in which hypothetical effect-site concentration was related to pharmacodynamic electroencephalographic effect via the sigmoid Emax model. The analysis yielded the following mean estimates: maximum electroencephalographic effect, 12.7% over baseline; 50% effective concentration, 13.1 ng/mL; and effect-site equilibration half-life, 8.8 mins.

CONCLUSION

Despite the delay in effect onset, continuous infusion of lorazepam, preceded by a bolus loading dose, produces a relatively constant sedative effect on the central nervous system, which can be utilized in the context of critical care medicine.

Use of midazolam for refractory status epilepticus in pediatric patients

Status epilepticus is more common among children than young adults. Children might be less likely to die and might be resistant to permanent neurologic damage due to status epilepticus, but significant sequelae also have been demonstrated. Aggressive intervention and rapid termination of seizures contribute significantly to better prognosis and reduced mortality from status epilepticus. Initial treatment of status epilepticus typically consists of either diazepam or lorazepam, immediately followed by phenytoin or phenobarbital. However, approximately 100% to 15% of status epilepticus episodes are refractory to these conventional therapies. Traditionally, refractory status epilepticus is treated with barbiturate coma or general anesthetics, both of which require invasive cardiorespiratory and hemodynamic monitoring and are associated with significant complications. Midazolam is a water-soluble benzodiazepine with a fast onset of action, a short half-life, and inactive metabolites that has been very effective in terminating seizures refractory to diazepam, lorazepam, phenytoin, and phenobarbital in pediatric patients. Midazolam is a valuable treatment option for refractory status epilepticus, especially in pediatric patients.

Complications of sedation with midazolam in the intensive care unit and a comparison with other sedative regimens

OBJECTIVE

To describe the various complications that have been reported with use of midazolam for sedation in the intensive care unit (ICU).

DATA SOURCES

Publications in scientific literature.

DATA EXTRACTION

Computer search of the literature.

SYNTHESIS

Sedation is required in the ICU in order for patients to tolerate noxious stimuli, particularly mechanical ventilation. Under- and oversedation can lead to complications. To sedate patients in the ICU, midazolam is commonly administered via titrated, continuous infusions. Cardiorespiratory effects tend to be minimal; however, hypotension can occur in hypovolemic patients. Prolonged sedation after cessation of the midazolam infusion may be caused by altered kinetics of the drug in critically ill patients or by accumulation of active metabolites. In addition, paradoxical and psychotic reactions have been rarely reported. Tolerance and tachyphylaxis may occur, particularly with longer-term infusions (> or = 3 days). Benzodiazepine withdrawal syndrome has also been associated with high dose/long-term midazolam infusions. Compared with propofol infusions, midazolam infusions have been associated with a decreased occurrence of hypotension but a more variable time course for recovery of function after the cessation of the infusion. Lorazepam is a more cost-effective choice for long-term (> 24 hrs) sedation.

CONCLUSION

Continuous infusion midazolam provides effective sedation in the ICU with few complications overall, especially when the dose is titrated.