Comparison of propofol and midazolam for sedation in critically ill patients

Propofol exerts protective effects on the acute lung injury induced by endotoxin in rats

Acute lung injury (ALI) is a major culprit of mortality in endotoxemia. Propofol has been commonly used in critical ill patients for sedation. This experiment attempted to elucidate the effects and possible mechanisms of propofol on the ALI induced by endotoxin. Experimentations were carried out using anesthetized, ventilated rats and isolated perfused rat lungs. Endotoxemia was induced by intravenous lipopolysaccharide (LPS, 10 mg kg(-1)). Various groups of rats received infusion of physiological saline solution (PSS) and LPS. Five min after LPS, propofol at low dose (5 mg kg(-1)h(-1)) or high dose (10 mg kg(-1)h(-1)) was infused for 6h. In isolated perfused rat lungs, PSS, LPS, and propofol (30 or 60 mg kg(-1)) were added into the perfusion circuit. During or after 6h observation, we determined the lung weight (LW)/body weight ratio, LW gain, exhaled nitric oxide (NO) and protein concentration in broncheoalveolar lavage. Lung pathology was evaluated to quantify the lung injury score. Plasma nitrate/nitrite, methyl guanidine (MG), tumor necrosis factor(alpha), and interleukin-1(beta) were examined. Blood leukocytes were counted. Capillary filtration coefficient (K(fc)) was obtained in isolated perfused lungs. Posttreatment of propofol at low or high dose attenuated or prevented the extent of ALI. It also reduced the plasma nitrate/nitrite, MG, and pro-inflammatory cytokines including tumor necrosis factor(alpha) (TNF(alpha)) and interleukin-1(beta) (IL-1(beta)). In the isolated perfused rat lungs, propofol significantly reduced the LPS-induced increase in K(fc). This agent did not affect the leukocytopenia caused by LPS. Accordingly, the effects of propofol on the ALI were not related to leukocyte activation or sequestration. Our results suggest that propofol exerts protective effect on the endotoxin-induced ALI. The mechanisms of actions may be mediated through inhibition on the release of pro-inflammatory cytokines, free radicals and NO. In addition, propofol abrogates the microvascular leakage of water and protein in the lungs. The results imply that the use of propofol in critically ill is not only for sedation, but also useful for the prevention of inflammatory progression and lung damage.

Propofol improves endothelial dysfunction and attenuates vascular superoxide production in septic rats

OBJECTIVE

To determine the effects of propofol on vascular functions, plasma and endothelium-derived nitric oxide (EDNO), vascular NO, and cyclic guanosine monophosphate (cGMP), as well as vascular production of superoxide anion (O2*-), in septic animals.

DESIGN

Prospective, multiexperimental, randomized, controlled studies.

SETTING

University research laboratory.

SUBJECTS

Male adult Sprague-Dawley rats weighing 350-400 g.

INTERVENTIONS

Cecal ligation and puncture (CLP), with and without propofol (25 mg/kg/hr) infusion, after sham or CLP (24 hrs postsurgery).

MEASUREMENTS AND MAIN RESULTS

Plasma NOx, basal aortic NOx, and cGMP concentrations all increased, whereas acetylcholine-induced endothelium-dependent relaxation (EDR), contractile response, and EDNO all decreased in CLP vs. sham rats (p < .001). Acetylcholine stimulated aortic NOx and cGMP significantly in sham and CLP-propofol (p < .01) but not CLP rats. Thus, propofol ameliorated the CLP-induced increases in plasma NOx, basal aortic NOx, and cGMP. It restored the CLP-induced impairment of EDR, EDNO, and acetylcholine-stimulated aortic NOx and cGMP levels. More O2*- production (measured by lucigenin-enhanced chemiluminescence) was noted in carotid arteries from CLP vs. sham rats (p < .001). Nicotinamide adenine dinucleotide (NADH; 1 mM) stimulated O2*- production in all rings, with significantly more increase in CLP vs. sham (p < .001). Propofol attenuated the excessive increase in O2*- production of CLP rings.

CONCLUSIONS

Propofol treatment attenuated the overproduction of NO and O2*-, thus restoring the acetylcholine-responsive NO-cGMP pathway in CLP-induced sepsis. It also significantly improved the CLP-impaired EDR and EDNO in a parallel manner. These beneficial effects of propofol could be accounted for by improvement of the disturbed NO/O2*- balance in sepsis.

Acute secondary adrenal insufficiency after traumatic brain injury: a prospective study

OBJECTIVE

To determine the prevalence, time course, clinical characteristics, and effect of adrenal insufficiency (AI) after traumatic brain injury (TBI).

DESIGN

Prospective intensive care unit-based cohort study.

SETTING

Three level 1 trauma centers.

PATIENTS

A total of 80 patients with moderate or severe TBI (Glasgow Coma Scale score, 3-13) and 41 trauma patients without TBI (Injury Severity Score, >15) enrolled between June 2002 and November 2003.

MEASUREMENTS

Serum cortisol and adrenocorticotropic hormone levels were drawn twice daily for up to 9 days postinjury; AI was defined as two consecutive cortisols of < or =15 microg/dL (25th percentile for extracranial trauma patients) or one cortisol of < 5 microg/dL. Principal outcome measures included: injury characteristics, hemodynamic data, usage of vasopressors, metabolic suppressive agents (high-dose pentobarbital and propofol), etomidate, and AI status.

MAIN RESULTS

AI occurred in 42 TBI patients (53%). Adrenocorticotropic hormone levels were lower at the time of AI (median, 18.9 vs. 36.1 pg/mL; p = .0001). Compared with patients without AI, those with AI were younger (p = .01), had higher injury severity (p = .02), had a higher frequency of early ischemic insults (hypotension, hypoxia, severe anemia) (p = .02), and were more likely to have received etomidate (p = .049). Over the acute postinjury period, patients with AI had lower trough mean arterial pressure (p = .001) and greater vasopressor use (p = .047). Mean arterial pressure was lower in the 8 hrs preceding a low (< or =15 microg/dL) cortisol level (p = .003). There was an inverse relationship between cortisol levels and vasopressor use (p = .0005) and between cortisol levels within 24 hrs of injury and etomidate use (p = .002). Use of high-dose propofol and pentobarbital was strongly associated with lower cortisol levels (p < .0001).

CONCLUSIONS

Approximately 50% of patients with moderate or severe TBI have at least transient AI. Younger age, greater injury severity, early ischemic insults, and the use of etomidate and metabolic suppressive agents are associated with AI. Because lower cortisol levels were associated with lower blood pressure and higher vasopressor use, consideration should be given to monitoring cortisol levels in intubated TBI patients, particularly those receiving high-dose pentobarbital or propofol. A randomized trial of stress-dose hydrocortisone in TBI patients with AI is underway.

Procedural Distress in Children With Cancer

OBJECTIVES

To examine the relationship among different indicators of pain and distress, including self-report, behavioral observations, and physiological parameters, in children with cancer undergoing invasive procedures.

METHODS

Forty-eight children between the ages of 3.1 and 17.7 years were evaluated while undergoing lumbar punctures. Self-report measures assessed anxiety, pain, self-efficacy, expectations of coping strategies, and coping self-efficacy. Parents reported on their own and their child's levels of anxiety, and physicians estimated their own level of stress and technical difficulty in completing the procedure. Behavioral observations were made prior to, during, and after the procedure. Physiological parameters included heart rate, cardiac vagal tone, and salivary cortisol. At the discretion of attending physicians, 32 children received deep sedation, 9 received light sedation, and 7 received cognitive-behavioral strategies with topical anesthetic as interventions to manage procedural distress.

RESULTS

There was a high degree of consistency within self-report, behavioral, and physiological parameters, but correlations between measures in different modalities were low. There were floor effects for most behavioral and self-report measures of distress. Cortisol showed marked changes preprocedure to postprocedure, demonstrating high levels of physiological response despite lack of apparent or perceived discomfort. Heart rate was significantly lower in the group using cognitive-behavioral techniques, especially at the point of needle insertion.

DISCUSSION

Self-report measures, behavioral indicators, and physiological changes are not interchangeable outcomes. Treatment strategies were effective for minimizing subjective and behavioral distress, but not necessarily for physiological reactions. Future research should focus on individual differences in these responses, and treatment outcome studies aimed at reducing distress must be clear about the specific goals of intervention.

Pharmacoeconomic Modeling of Lorazepam, Midazolam, and Propofol for Continuous Sedation in Critically Ill Patients

STUDY OBJECTIVE

To compare the expected costs of short-, intermediate-, and long-term sedation (< 24, 24-72, and > 72 hrs, respectively) with propofol, lorazepam, and midazolam in an intensive care unit.

METHODS

Decision-analysis models were constructed for each sedative and each duration by using institutional costs associated with drug administration and adverse events (including personnel time). Costs were expressed in 2002 U.S. dollars. Adverse events were agitation, hypertriglyceridemia and/or pancreatitis, hypotension, nutritional changes, ventilator-associated pneumonia, and prolonged awakening and/or extubation. MEDLINE and EMBASE databases were searched to obtain durations of sedation, the incidence of outcomes, and cost estimates of outcomes. The ability to maintain specific levels of sedation was assumed equivalent among the sedatives. Univariate sensitivity analyses were conducted to determine the cost-driving variables, and probabilistic sensitivity analyses were conducted by using second-order Monte Carlo simulations.

RESULTS

Weighted mean durations of sedation from 50 studies were 13.46 (short term), 45.27 (intermediate term), and 119.78 (long term) hours. Expected costs for sedation with lorazepam, midazolam, and propofol, respectively, were 497 dollars, 294 dollars, and 272 dollars short term; 932 dollars, 587 dollars, and 674 dollars intermediate term; and 1604 dollars, 1737 dollars, and 2033 dollars long term. Propofol was least costly in 86% of the short-term simulations, midazolam was least costly in 97.5% of the intermediate-term simulations, and lorazepam was least costly in 84% of the long-term simulations. The most important cost-driver for all sedatives was drug cost. Prolonged extubation after sedation was an important cost-driver for lorazepam and midazolam, especially as sedation was lengthened.

CONCLUSION

Propofol, midazolam, and lorazepam had the lowest expected costs for short-, intermediate-, and long-term sedation, respectively. Many factors aside from drug costs influenced the cost of sedation.

Metabolic and endocrine effects of sedative agents

PURPOSE OF REVIEW

To bring to the attention of the clinician the metabolic effects of most common sedatives and analgesics used in critically ill patients.

RECENT FINDINGS

Most patients admitted to the intensive care unit require sedation and analgesia to reduce anxiety, agitation, and delirium and provide pain relief. Inappropriate sedation and analgesia techniques can cause harm to the already compromised patient if they do not take into account the metabolic effect they produce.

SUMMARY

Metabolically critical illness can be divided in two phases, and acute and a prolonged one. Whereas the acute or hypermetabolic phase is characterized by elevated circulating concentration of catabolic hormones and substrate utilization to provide energy to vital organs, the prolonged or catabolic phase of critical illness is marked by reduced endocrine stimulation and severe loss of body cell mass. The most common analgesic and sedative agents used in the intensive care unit, if used in small or moderate doses, do not interfere significantly with the metabolic milieu; however, prolonged infusions, and in high doses, without adequate monitoring of level of sedation and quality of analgesia, can precipitate morbid events. Further research is needed in the metabolic aspects of analgesia and sedation in the intensive care unit, particularly if a multimodal pharmacologic strategy is used whereby multiple interventions aim at minimizing the risk of overdosing and contributing to attenuation of the stress response associated with critical illness.

Effects of post-treatment with low-dose propofol on inflammatory responses to lipopolysaccharide-induced shock in conscious rats

1. In the present study, we used a low dose of propofol (5 mg/kg per h) to investigate its effects on the pro-inflammatory cytokines (tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-10) and changes in nitric oxide (NO) following lipopolysaccharide (LPS) for a period of 12 h in conscious rats. 2. Experiments were designed to induce endotoxin shock by intravenous injection of Klebsiella pneumoniae LPS (10 mg/kg) in conscious rats. Arterial pressure (AP) and heart rate (HR) were monitored continuously for 12 h after LPS administration. Tumour necrosis factor-alpha, IL-1beta, IL-10 and plasma nitrates/nitrites were determined before and 0.5, 1, 3, 6, 9 and 12 h after LPS administration. A low dose of intravenous propofol (5 mg/kg per h) was administered to investigate the effects on cytokine responses and changes in NO in endotoxin shock. 3. Lipopolysaccharide significantly increased TNF-alpha, IL-1beta, IL-10, nitrites/nitrates and HR, whereas mean AP was decreased. Post-treatment with propofol suppressed the release of TNF-alpha, IL-1beta, IL-10 and NO production after endotoxin shock. 4. Lipopolysaccharide also caused a decrease in the white blood cell count and haematocrit. 5. Post-treatment with propofol slightly, but not significantly, affected the LPS-induced systemic hypotension, tachycardia, leukocytopenia and anaemia. 6. These findings suggest that low-dose propofol may be beneficial to the inflammatory change in sepsis.

Withdrawal following sufentanil/propofol and sufentanil/midazolam

PURPOSE

Patients in the ICU after long-term administration of an opioid/hypnotic often develop delirium. To assess the nature of this phenomenon, patients in a surgical ICU following ventilatory support and sedation with an opioid/hypnotic/sedative were studied.

METHODOLOGY

Following sufentanil/midazolam (group 1; n =14) or sufentanil/propofol (group 2; n =15) sedation, patients were evaluated for changes in mean arterial blood pressure and heart rate, the activity of the central nervous system (sensory evoked potentials, spectral edge frequency of EEG), and the endogenous opioids plasma concentrations (beta-endorphin, met-enkephalin). Data obtained were correlated with the individual intensities of withdrawal symptoms 6-, 12-, and 24 h following sedation.

RESULTS

Following a mean duration of ventilation of 7.7 days (+/-3.6 SD) in groups 1 and 3.5 (+/-1.7 SD) in group 2, withdrawal intensities peaked within the 6th hour after cessation. Plasma beta-endorphin and met-enkephalin levels were low during sedation, and only the sufentanil/midazolam group demonstrated a postinhibitory overshoot. Withdrawal symptom intensities demonstrated an inverse correlation with beta-endorphin and met-enkephalin levels, a direct linear correlation with amplitude height of the evoked potential, and blood pressure and heart rate changes. Withdrawal intensities did not correlate with EEG power spectral edge frequency.

CONCLUSION

The endorphinergic system is suppressed when a potent exogenous opioid like sufentanil is given over a long period of time. Following sedation, abstinence symptoms seem to be related to postinhibitory increased endorphin synthesis. This is mostly seen in the combination of sufentanil/midazolam. In addition, an increase in the amplitude of the sensory-evoked potential suggests a postinhibitory excitatory state within the nociceptive system.

Propofol sedation using Diprifusor target-controlled infusion in adult intensive care unit patients

This multicentre, non-comparative study investigated the range of target blood propofol concentrations required to sedate 122 adult intensive care patients when propofol was administered using Diprifusor target-controlled infusion systems together with opioid analgesia. Depth of sedation was assessed with a modified Ramsay score and the target blood propofol setting was adjusted to achieve the sedation desired for each patient. A desired level of sedation was achieved for 84% of the sedation period. In postcardiac surgery patients the median time-weighted average propofol target setting was 1.34 microg.ml(-1) (10th - 90th percentiles: 0.79-1.93 microg.ml(-1)). Values in brain injured and general ICU patients were 0.98 (10th - 90th percentiles: 0.60-2.55) microg.ml(-1) and 0.42 (10th - 90th percentiles: 0.16-1.19) microg.ml(-1), respectively. Measured propofol concentrations were generally close to values predicted by the Diprifusor system. Target settings in the range of 0.2-2.0 microg.ml(-1) are proposed for propofol sedation in this setting with titration as required in individual patients.

A case of propofol toxicity: further evidence for a causal mechanism

A 5-month-old boy required sedation after a cleft lip repair. He was sedated with propofol and intermittent fentanyl, requiring escalating doses over the subsequent 48 h. On the second post-operative day he developed a metabolic acidosis followed by multiple cardiac dysrhythmias, hepatic and renal failure. Propofol was stopped. His multisystem organ failure gradually resolved after initiation of charcoal haemoperfusion. Further investigation demonstrated an abnormality in acylcarnitine metabolism, similar to that found in one previous case report.

Short-term propofol infusion as an adjunct to extubation in burned children

Children who require intubation as a component of their burn management generally need heavy sedation, usually with a combination of opiate and benzodiazepine infusions with a target sensorium of light sleep. When extubation approaches, the need for sedation to prevent uncontrolled extubation can conflict with the desire to lighten sedation enough to ensure that airway protective reflexes are strong. The several hours' half-life of these medications can make this period of weaning challenging. Therefore, the hours preceding extubation are among the most difficult in which to ensure safe adequate sedation. The pharmacokinetics of propofol allow for the rapid emergence of a patient from deep sedation. We have had success with an extubation strategy using short-term propofol infusions in critically ill children. In this work, children were maintained on morphine and midazolam infusions per our unit protocol, escalating doses as required to maintain comfort. Approximately 8 hours before planned extubation, these infusions were decreased by approximately half and propofol infusion added to maintain a state of light sleep. Extubation was planned approximately 8 hours later to allow ample time for the chronically infused opiates and benzodiazepines to be metabolized down to the new steady-state level. Thirty minutes before planned extubation, propofol was stopped while morphine and midazolam infusions were maintained at the reduced level. When the children awakened from the propofol-induced state of light sleep, they were extubated while the reduced infusions of morphine and midazolam were maintained. These were subsequently weaned slowly, depending on the child's need for ongoing pain and anxiety medication, per our unit protocol to minimize the incidence of withdrawal symptoms. Data are shown in the text as mean +/- standard deviation. These 11 children (eight boys and three girls) had an average age of 6.6 +/- 5.6 years (range, 1.2-13 years), average weight of 36.9 +/- 28.7 kg (range, 9.3-95 kg), and burn size of 43 +/- 21.4% (range, 10-85%). Three children had sustained scald burns and eight had flame injuries with associated inhalation injury. They had been intubated for an average of 12.7 +/- 10.9 (range, 2-33 days). Morphine infusions immediately before the initiation of propofol averaged 0.26 +/- 0.31 mg/kg/hour (range, 0.04-1.29 mg/kg/hr) and midazolam averaged 0.15 +/- 0.16 mg/kg/hr (range, 0.06-0.65 mg/kg/hr). Morphine infusions after beginning propofol and at extubation averaged 0.16 +/- 0.16 (range, 0.04-0.65 mg/kg/hr) and midazolam averaged 0.09 +/- 0.08 mg/kg/hr (range, 0.02-0.32 mg/kg/hr). Propofol doses after initial titration during the first hour of infusion averaged 3.6 +/- 2.9 mg/kg/hr (range, 0.4-8.1 mg/kg/hr). Nine of the 11 children (82%) were successfully extubated on the first attempt. Two required reintubation for postextubation stridor 2 to 6 hours after extubation but were successfully extubated the next day after a short course of steroids, again using the same propofol technique. All were awake at extubation and went on to survive. Morphine and midazolam infusions were gradually weaned, and there were no withdrawal symptoms noted. Although prolonged (days) infusions of propofol have been associated with adverse cardiovascular complications in critically ill young children and should probably be avoided, short-term (in hours) use of the drug can facilitate smooth extubation.

ICU sedation after coronary artery bypass graft surgery: dexmedetomidine-based versus propofol-based sedation regimens

OBJECTIVE

To compare dexmedetomidine-based to propofol-based sedation after coronary artery bypass graft (CABG) surgery in the intensive care unit (ICU).

DESIGN

Randomized, open label.

SETTING

Twenty-five centers in the United States and Canada.

PARTICIPANTS

Two hundred ninety-five adults undergoing CABG surgery.

INTERVENTIONS

At sternal closure, patients in group A received 1.0 microg/kg of dexmedetomidine over 20 minutes and then 0.2 to 0.7 microg/kg/h to maintain a Ramsay sedation score > or =3 during assisted ventilation and > or =2 after extubation. Patients could be given propofol for additional sedation if necessary; group B patients received propofol-based care according to each investigator's standard practice.

MEASUREMENTS AND MAIN RESULTS

Mean sedation levels were within target ranges in both groups. Mean times to weaning and extubation were similar, although fewer dexmedetomidine patients remained on the ventilator beyond 8 hours. Morphine use was significantly reduced in the dexmedetomidine group. Only 28% of the dexmedetomidine patients required morphine for pain relief while ventilated versus 69% of propofol-based patients (p < 0.001). Propofol patients required 4 times the mean dose of morphine while in the ICU. Mean blood pressure increased initially in both groups, then decreased to 3 mmHg below baseline in dexmedetomidine patients; mean arterial pressure remained at 9 mmHg above baseline in propofol patients. No ventricular tachycardia occurred in the dexmedetomidine-sedated patients compared with 5% of the propofol patients (p = 0.007). Respiratory rates and blood gases were similar. Fewer dexmedetomidine patients received beta-blockers (p = 0.014), antiemetics (p = 0.015), nonsteroidal anti-inflammatory drugs (p < 0.001), epinephrine (p = 0.030), or high-dose diuretics (p < 0.001).

CONCLUSION

Dexmedetomidine provided safe and effective sedation for post-CABG surgical patients and significantly reduced the use of analgesics, beta-blockers, antiemetics, epinephrine, and diuretics.

The pathophysiology of propofol infusion syndrome: a simple name for a complex syndrome

Propofol infusion syndrome (PRIS) is a rare and often fatal syndrome described in critically ill children undergoing long-term propofol infusion at high doses. Recently several cases have been reported in adults, too. The main features of the syndrome consist of cardiac failure, rhabdomyolysis, severe metabolic acidosis and renal failure. To date 21 paediatric cases and 14 adult cases have been described. These latter were mostly patients with acute neurological illnesses or acute inflammatory diseases complicated by severe infections or even sepsis, and receiving catecholamines and/or steroids in addition to propofol. Central nervous system activation with production of catecholamines and glucocorticoids, and systemic inflammation with cytokine production are priming factors for cardiac and peripheral muscle dysfunction. High-dose propofol, but also supportive treatments with catecholamines and corticosteroids, act as triggering factors. At the subcellular level, propofol impairs free fatty acid utilisation and mitochondrial activity. Imbalance between energy demand and utilisation is a key pathogenetic mechanism, which may lead to cardiac and peripheral muscle necrosis. Propofol infusion syndrome is multifactorial, and propofol, particularly when combined with catecholamines and/or steroids, acts as a triggering factor. The syndrome can be lethal and we suggest caution when using prolonged (>48 h) propofol sedation at doses higher than 5 mg/kg per h, particularly in patients with acute neurological or inflammatory illnesses. In these cases, alternative sedative agents should be considered. If unsuitable, strict monitoring of signs of myocytolysis is advisable.

Propofol does not induce pulmonary dysfunction in stressed endotoxic pigs receiving Intralipid

OBJECTIVE

To assess the effect of diisopropyl phenol (propofol), with and without Intralipid, on the cardiopulmonary system and on thromboxane production in endotoxic pigs.

DESIGN

Prospective, randomized animal study.

SETTING

Animal research laboratory at a major teaching hospital.

SUBJECTS

Twenty-four pigs, divided into three groups (n = 8).

INTERVENTIONS

Pulmonary arterial catheters and arterial cannulas were inserted into all pigs. Each pig received a 30 ng/kg bolus of endotoxin at 1 hr, followed by a continuous infusion of endotoxin at 24 ng x kg-1 x hr-1. Diisopropyl phenol at 25, 75, and 200 microg x kg-1 x min-1 was administered to all pigs, beginning at 1, 2, and 3 hrs, respectively. The pigs were divided into three groups to receive 0.25 g x kg-1 x hr-1, 0.08 g x kg-1 x hr-1, or no Intralipid, starting at time t = 0. Heart rate and mean arterial, central venous, and pulmonary arterial pressures were recorded continuously. Core temperature, arterial blood gases, mixed venous oxygen saturation, pulmonary arterial occlusion pressure, and cardiac output were measured intermittently. Thromboxane B(2) concentrations were measured at baseline and at 60, 75, 120, 135, 180, 195, and 240 mins. Data are expressed as mean +/- sd. Groups were compared by using repeated analysis of variance, with p <.05 used for statistical significance.

MEASUREMENTS AND MAIN RESULTS

All pigs completed the 4-hr study. Marked variabilities were noted for individual pigs. Following the infusion of endotoxin, compared with baseline, there was a significant increase in pulmonary vascular resistance and a decrease in Pao(2) (p <.001 and p <.008, respectively). This response was not affected by the increasing dose of diisopropyl phenol, nor were there differences between the Intralipid and control groups. Pao(2) remained significantly lower in all groups, compared with the baseline measurements (p <.001) over the 4 hrs of the experiment. Thromboxane B(2) concentrations remained elevated compared with baseline and were significantly higher (p <.05) in the high-dose Intralipid group, compared with the low-dose and the control groups, during the last hour of the experiment.

CONCLUSIONS

Small doses of endotoxin, when given to pigs, induce major perturbations of cardiopulmonary function. Neither Intralipid, high vs. low dose, nor diisopropyl phenol, at sedating vs. anesthetizing doses, worsened the physiologic derangement associated with the stress of low-dose endotoxemia.

Use of propofol infusion in Australian and New Zealand paediatric intensive care units

Despite the risk of propofol infusion syndrome, a rare but often fatal complication of propofol infusion in ventilated children and possibly adults, propofol infusion remains in use in paediatric intensive care units (PICU). This questionnaire study surveys the current pattern of use of this sedative infusion in Australian and New Zealand PICUs. Thirty-three of the 45 paediatric intensive care physicians surveyed (73%), from 12 of the 13 intensive care units, returned completed questionnaires. The majority of practitioners (82%) use propofol infusion in children in PICU, the main indication being for short-term sedation in children requiring procedures. 39% of respondents consider propofol infusion useful in ventilated children requiring longer-term sedation. 67% of paediatric intensivists use maximum infusion doses that may be considered dangerously high (> or = 10 mg/kg/h). Nineteen per cent use propofol infusion for prolonged periods (> 72 hours). A smaller proportion (15%) of respondents indicate that they may use both higher doses and prolonged periods of infusion, a practice likely to lead to a greater chance of serious adverse events. Knowledge of local protocols for the use of propofol infusion is associated with a significantly greater level of monitoring for possible adverse events. We suggest that national guidelines for the use of propofol infusion in children should be developed. These should include clear indications and contraindications to its use, a maximum dose rate and maximum period of infusion, with a ceiling placed on the cumulative dose given and clearly stated minimum monitoring requirements.

Sedation during mechanical ventilation: a systematic review

OBJECTIVE

A systematic review was performed to determine the most effective agent with which to sedate adult patients who have respiratory failure that requires mechanical ventilation in the medical intensive care unit.

DATA SOURCES

A computerized literature search of MEDLINE, a U.S. National Library of Medicine online database, from 1966 to August 1998 was conducted. All selected articles were reviewed to identify other relevant articles.

STUDY SELECTION

Inclusion criteria were as follows: a) population-adults with respiratory failure who received mechanical ventilation in a medical intensive care unit; b) design-prospective, randomized controlled trial; c) intervention-sedation; and d) primary outcome-successful sedation.

DATA EXTRACTION

Of 71 potentially relevant articles, only 15 randomized trials fulfilled all four selection criteria.

DATA SYNTHESIS

Clinical heterogeneity among studies precluded statistical pooling of results.

CONCLUSIONS

More research is needed to determine the most effective agent with which to sedate adult patients who have respiratory failure that requires mechanical ventilation in the medical intensive care unit.

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.

Bispectral index-guided sedation with dexmedetomidine in intensive care: a prospective, randomized, double blind, placebo-controlled phase II study

OBJECTIVE

To compare dexmedetomidine vs. placebo with respect to the amount of additional propofol and morphine used for bispectral index-guided sedation and analgesia in mechanically ventilated, intensive care patients after surgery.

DESIGN

Prospective, randomized, double blind, placebo-controlled, phase II clinical trial.

SETTING

General surgical and cardiac surgical intensive care units.

PATIENTS

Thirty patients scheduled for major surgery requiring mechanical ventilation for a minimum of 6 hrs were included in the study.

INTERVENTIONS

Patients were assigned randomly to receive either dexmedetomidine (loading infusion, 6.0 microg x kg(-1) x hr(-1) for 10 mins; maintenance infusion, 0.1-0.7 microg x kg(-1) x hr(-1)) or placebo after intensive care unit admission.

MEASUREMENTS AND MAIN RESULTS

Sedation was guided by using the electroencephalographic parameter bispectral index, a new noninvasive method to estimate the level of sedation. We aimed at maintaining bispectral index ranges between 60 and 70 during mechanical ventilation before starting weaning, 65 and 95 during weaning, and 85 to 95 postextubation. Additional sedative and analgesic medication was given (propofol and morphine) as clinically indicated and within the previously mentioned bispectral index ranges. Patients receiving dexmedetomidine required significantly less propofol during mechanical ventilation (0.87 +/- 0.21 vs. 1.52 +/- 0.30 mg x kg(-1) x hr(-1); p <.01) and weaning (0.17 +/- 0.06 vs. 0.62 +/- 0.21 mg x kg(-1) x hr(-1); p <.001) to maintain the target bispectral index range. During study drug administration, morphine requirements for dexmedetomidine-treated patients were reduced by 58% (p =.05). Hemodynamic stability during weaning and after extubation was better maintained in patients receiving dexmedetomidine.

CONCLUSIONS

Dexmedetomidine reduced propofol requirements and improved hemodynamic stability during bispectral index-guided intensive care unit sedation.

Metabolic acidosis, rhabdomyolysis, and cardiovascular collapse after prolonged propofol infusion

The authors present the hospital course of a 13-year-old girl with a closed head injury who received a prolonged infusion of propofol for sedation and, subsequently, died as a result of severe metabolic acidosis, rhabdomyolysis, and cardiovascular collapse. The patient had been treated for 4 days at a referring hospital for a severe closed head injury sustained in a fall from a bicycle. During treatment for elevations of intracranial pressure, she received a continuous propofol infusion (100 microg/kg/min). The patient began to exhibit severe high anion gap/low lactate metabolic acidosis, and was transferred to the pediatric intensive care unit at the authors' institution. On arrival there, the patient's Glasgow Coma Scale score was 3 and this remained unchanged during her brief stay. The severe metabolic acidosis was unresponsive to maximum therapy. Acute renal failure ensued as a result of rhabdomyolysis, and myocardial dysfunction with bizarre, wide QRS complexes developed without hyperkalemia. The patient died of myocardial collapse with severe metabolic acidosis and multisystem organ failure (involving renal, hepatic, and cardiac systems) approximately 15 hours after admission to the authors' institution. This patient represents another case of severe metabolic acidosis, rhabdomyolysis, and cardiovascular collapse observed after a prolonged propofol infusion in a pediatric patient. The authors suggest selection of other pharmacological agents for long-term sedation in pediatric patients.

Comparison between dexmedetomidine and propofol for sedation in the intensive care unit: patient and clinician perceptions

The alpha2 agonist dexmedetomidine is a new sedative and analgesic agent which is licensed in the USA for post-operative intensive care sedation. We compared dexmedetomidine with propofol in patients requiring sedation in intensive care. Twenty adult patients expected to require a minimum of 8 h artificial ventilation after surgery were randomized to receive sedation with either dexmedetomidine or propofol infusions. Additional analgesia, if required, was provided by an alfentanil infusion. Depth of sedation was monitored using both the Ramsay sedation score (RSS) and the bispectral index (BIS). Cardiovascular, respiratory, biochemical and haematological data were obtained. Patients' perceptions of their intensive care stay were assessed using the Hewitt questionnaire. Sedation was equivalent in the two groups [median (interquartile range): RSS, propofol group 5 (4-5), dexmedetomidine group 5 (4-6) (P=0.68); BIS, propofol group 53 (41-64), dexmedetomidine group 46 (36-58); P=0.32], but the propofol group received three times more alfentanil compared with patients sedated with dexmedetomidine [2.5 (2.2-2.9) mg h(-1) versus 0.8 (0.65-1.2) mg h(-1) (P=0.004)]. No differences were found in arterial pressures between the groups, but heart rate was significantly lower in the dexmedetomidine group [mean (SD) 75 (6) vs 90 (4) beats min(-1)]. Extubation times were similar and rapid with the use of both sedative agents [median (range) 28 (20-50) and 29 (15-50) min (P=0.63) respectively for the propofol and dexmedetomidine groups]. No adverse events related to the sedative infusions occurred in either group. Despite ventilation and intubation, patients sedated with dexmedetomidine could be easily roused to cooperate with procedures (e.g. physiotherapy, radiology) without showing irritation. From the clinician's and patient's perspectives, dexmedetomidine is a safe and acceptable sedative agent for those requiring intensive care. The rate pressure product is reduced in patients receiving dexmedetomidine, which may protect against myocardial ischaemia. Dexmedetomidine reduces the requirement for opioid analgesia.

Propofol or midazolam--which is best for the sedation of adult ventilated patients in intensive care units? A systematic review

Intensive care patients are commonly sedated to maintain comfort and to facilitate life saving therapy. Although sedation is ordered by medical staff, nurses are usually responsible for its administration and titration and thus the question of which drug regime should be chosen is an important practice issue for nurses (1,2). This paper is a report on a systematic review that was conducted to compare the effectiveness of two of the most common drugs used for the sedation of adult ventilated patients in Australian intensive care units (ICUs)--propofol and midazolam (3). All randomised controlled trials (RCTs) which compared propofol with midazolam for the sedation of adult ventilated patients in ICUs were included in the study. The outcome measures evaluated were the quality of sedation achieved, the length of time from cessation of sedation till extubation, recovery time, duration of admission to the ICU and the incidence of haemodynamic complications. Meta-analysis was used to compare results of studies where subjects had the same characteristics and the outcome criteria were measured in the same manner. The review found that infusions of both midazolam and propofol appear to provide similar quality sedation, that extubation time and recovery time is shorter in patients sedated with propofol and that haemodynamic complications related to either drug regime are not usually clinically significant.

Effects of dexmedetomidine on adrenocortical function, and the cardiovascular, endocrine and inflammatory responses in post-operative patients needing sedation in the intensive care unit

We have compared the effects of dexmedetomidine and propofol on endocrine, metabolic, inflammatory and cardiovascular responses in patients in the intensive care unit (ICU) after major surgery. Twenty patients who were expected to require 8 h of post-operative sedation and ventilation were allocated randomly to receive either an infusion of dexmedetomidine 0.2-2.5 microg kg(-1) h(-1) or propofol 1-3 mg kg(-1) h(-1). Arterial pressure, heart rate and sequential concentrations of circulating cortisol, adrenocorticotrophic hormone (ACTH), growth hormone, prolactin, insulin, glucose and interleukin 6 were measured. An ACTH stimulation test was performed in all patients who received dexmedetomidine. Heart rate was significantly lower in the dexmedetomidine patients. There were no differences in arterial pressure, cortisol, ACTH, prolactin and glucose concentrations between the two groups. A positive response to the ACTH stimulation test varied depending on the diagnostic criteria used. The insulin concentration was significantly lower in the dexmedetomidine group at 2 h (P=0.021), although this did not affect blood glucose concentrations. Growth hormone concentrations were significantly higher in dexmedetomidine-treated patients overall (P=0.036), but circulating concentrations remained in the physiological range. Interleukin 6 decreased in the dexmedetomidine group. We conclude that dexmedetomidine infusion does not inhibit adrenal steroidogenesis when used for short-term sedation after surgery.

A lack of evidence of superiority of propofol versus midazolam for sedation in mechanically ventilated critically ill patients: a qualitative and quantitative systematic review

Propofol and midazolam are often used for sedation in the intensive care unit. The aim of this systematic review was to estimate the efficacy and harm of propofol versus midazolam in mechanically ventilated patients. A systematic search (Medline, Cochrane Library, Embase, bibliographies), any language, up to June 1999 was performed for reports of randomized comparisons of propofol with midazolam. Data from 27 trials (1624 adults) were analyzed. The average duration of sedation varied between 4 and 339 h. In 10 trials, the duration of adequate sedation was longer with propofol (weighted mean difference 2.9 h; 95% confidence interval [CI], 0.2-5.6 h). In 13 trials (mostly postoperative), sedation lasted 4 to 35 h; in 9 of those, average weaning time from mechanical ventilation with propofol was 0.8-4.3 h; with midazolam it was 1.5-7.2 h (weighted mean difference 2.2 h [95% CI, 0.8 to 3.7 h]). In 8 trials, sedation lasted 54 to 339 h; there was a lack of evidence for difference in weaning times. Arterial hypotension (relative risk 2.5 [95% CI, 1.3 to 4.5]; number-needed-to-treat, 12), and hypertriglyceridemia (relative risk 12.1 [95%CI, 2.9 to 49.7]; number-needed-to-treat, 6) occurred more often with propofol. The duration of adequate sedation time is longer with propofol compared with midazolam. In postoperative patients with sedation <36 h, weaning is faster with propofol.

IMPLICATIONS

The duration of adequate sedation time is longer with propofol compared with midazolam. In postoperative patients with sedation < 36 h, weaning is faster with propofol.

Measuring quality of sedation in adult mechanically ventilated critically ill patients. the Vancouver Interaction and Calmness Scale. Sedation Focus Group

There are no reliable, valid, and responsive scales to measure the quality of sedation in adult critically ill patients. Our objective was to develop a summated rating scale with these properties and to define the minimal clinically important difference (MCID). We developed and tested the scale in an 18-bed medical-surgical intensive care unit (ICU) (12-bed acute and 6-bed subacute unit). Following identification of relevant domains and item derivation, 116 observations were made on 38 patients; psychometric properties and interrater reliability were assessed to allow item reduction. The final scale consisted of two five-item subscales quantifying calmness and interaction along a continuum from 5 to 30 points. Interrater reliability was 0.89 and 0.90; internal consistency was 0. 95 for both subscales. To test construct validity, MCID, and responsiveness 302 observations were made on 54 patients. Construct validity: calmness score vs. need for further intervention to make the patient calm (R = -0.82, P < 0.001); interaction score discriminated between acute vs. subacute units, mean scores 15.28 +/- 8.26 vs. 23.54 +/- 7.42, mean difference 8.27 (95% CI - 10.32 to -6.22); MCID - 2.2 and 2.5 for the calmness and interaction subscales; Guyatt's responsiveness statistics - 1.4 and 2.3. The Vancouver Interaction and Calmness Scale (VICS) is reliable, valid, and responsive.

A prospective evaluation of empiric versus protocol-based sedation and analgesia

STUDY OBJECTIVE

To compare empiric and protocol-based therapies of sedation and analgesia in terms of pharmacologic cost, effects on mechanical ventilation and intensive care unit (ICU) stay, and quality of sedation and analgesia.

DESIGN

Prospective study.

SETTING

A 24-bed medical-surgical-neurologic ICU.

PATIENTS

Seventy-two patients evaluated during empiric therapy and 86 during protocol-based therapy.

INTERVENTION

Assessment of data collected for 4 months before and 5 months after an evidence-based sedation and analgesia protocol was implemented.

MEASUREMENTS AND MAIN RESULTS

Protocol adherence rate was 83.7%. The hourly cost (Canadian dollars) of sedation was less with protocol-based therapy ($5.68 +/- 4.27 vs $7.69 +/- 5.29, p<0.01) likely due to increased lorazepam use. Pharmacologic cost savings may be negated since sedation duration tended to be longer (122.7 +/- 142.8 vs 88.0 +/- 94.8 hrs, p<0.1) and extubation may have been delayed (61.6 +/- 97.4 vs 39.1 +/- 54.7 hrs, p=0.13) with protocol use. Duration of ICU stay after sedation was discontinued was not significantly different before and after protocol implementation. With the protocol, however, the percentage of modified Ramsay sedation scores representing discomfort decreased from 22.4 to 11% (p<0.001) and the percentage at a score of 4 increased from 17.2% to 29.6% (p<0.01). The percentage of modified visual analog measurements representing pain decreased from 9.6 to 5.9% (p<0.05) with the protocol. When data were stratified according to duration of sedation, the benefits and delayed extubation associated with protocol-based therapy were limited to patients requiring long-term sedation.

CONCLUSION

Compliance with this protocol reduced drug costs and enhanced the quality of sedation and analgesia for patients requiring long-term sedation. Protocol-based therapy with lorazepam may have delayed extubation but did not delay ICU discharge.

Refractory delirium tremens treated with propofol: a case series

Delirium tremens, the most serious manifestation of alcohol withdrawal, occurs in approximately 5% of hospitalized alcoholics and has a mortality rate approaching 15%. Patients with delirium tremens are usually treated in an intensive care unit in which benzodiazepines form the cornerstone of therapy. In this report, we describe four patients who proved refractory to high doses of benzodiazepines and were successfully treated with a propofol infusion.

The effect of sedation on weaning following coronary artery bypass grafting: propofol versus oxycodone-thiopental

BACKGROUND

Propofol has been advocated for sedation in intensive care because of superior recovery characteristics. We hypothesised that the use of two totally different sedation methods after coronary artery bypass grafting should result in differences not only in extubation time, but also in breathing pattern and gas exchange during weaning and after extubation.

METHODS

Thirty patients participated in this randomised and controlled study. We used propofol infusion and oxycodone-thiopental bolus dosage, titrated to sedation level 4 or 5 according to Ramsey. Weaning was performed using protocol-based pressure support trials.

RESULTS

Total (SD) fentanyl dose during operation was 33 (6) microg x kg(-1) for propofol and 34 (6) microg x kg(-1) for oxycodone-thiopental (ns). The target sedation was achieved equally with both methods. The time from admission to intensive care unit to extubation was 494 (100) min for propofol and 521 (98) min for oxycodone-thiopental (ns). Weaning times were 63 (24) min and 112 (63) min in the propofol and oxycodone-thiopental groups, respectively (P<0.05). Breathing frequency increased and tidal volume decreased from weaning to 2 h postextubation.

CONCLUSION

Propofol infusion and oxycodone-thiopental bolus dosages, titrated to the same sedation end point, resulted in similar time from admission to extubation, although the weaning period was shorter in the propofol group. In terms of breathing pattern, gas exchange, blood gases and haemodynamics, the methods were similar. Propofol, despite its attractive pharmacological profile, may offer no clinical benefit in short-term sedation after a moderate dose fentanyl anaesthesia in cardiac surgery.

Life-threatening brain failure and agitation in the intensive care unit

The modern intensive care unit (ICU) has evolved into an area where mortality and morbidity can be reduced by identification of unexpected hemodynamic and ventilatory decompensations before long-term problems result. Because intensive care physicians are caring for an increasingly heterogeneous population of patients, the indications for aggressive monitoring and close titration of care have expanded. Agitated patients are proving difficult to deal with in nonmonitored environments because of the unpredictable consequences of the agitated state on organ systems. The severe agitation state that is associated with ethanol withdrawal and delirium tremens (DT) is examined as a model for evaluating the efficacy of the ICU environment to ensure consistent stabilization of potentially life-threatening agitation and delirium.

Propofol anesthesia for outpatient oral and maxillofacial surgery

Propofol is a sedative-hypnotic intravenous anesthetic agent that has gained wide use in outpatient oral and maxillofacial surgery since its clinical introduction in 1985. Propofol has several therapeutic advantages that make it an excellent choice for use in all phases of general anesthesia and conscious sedation. It is associated with minimal side effects, a controllable anesthetic state, and rapid recovery. This review of propofol discusses its pharmacologic character, administration, and side effects and presents anesthetic drug interaction information and comparisons.

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.

Infusion of propofol, sufentanil, or midazolam for sedation after aortic surgery: comparison of oxygen consumption and hemodynamic stability

We conducted a prospective, randomized study to compare quality of sedation, hemodynamic stability, and oxygen consumption of three different drugs for continuous i.v. sedation in the immediate postoperative period in patients scheduled for aortic surgery (propofol [n = 12], sufentanil [n = 12], or midazolam [n = 12]). After arrival in the recovery room, patients were randomized into one of the following groups: Group P (continuous infusion of propofol 2 mg x kg(-1) x h(-1)), Group S (continuous infusion of sufentanil 0.25 microg x kg(-1) x h(-1), with bolus doses of midazolam 2 mg to maintain sedation at 3-4 on the Ramsay scale), and Group M (continuous infusion of midazolam 0.07-0.15 microg x kg(-1) x h(-1) to maintain sedation at 3-4 on the Ramsay scale). The three drugs were associated with similar hemodynamic stability, incidence of myocardial ischemia, and comparable kinetics and mean values for VO2, but a significant higher number of peaks for VO2 in Group S during the period of rewarming. To obtain an appropriate Ramsay score, we needed to increase the rate of administration of the drug in Group P, and to decrease this rate in Group M. After the drugs were discontinued, Group P required mechanical ventilation for less time. In conclusion, propofol is as effective as sufentanil or midazolam in controlling increased VO2 postoperatively. The initial dose of 2 mg x kg(-1) x h(-1) had to be increased for most patients. In addition, propofol sedation is associated with a quicker recovery compared with midazolam and sufentanil.

IMPLICATIONS

A prospective, randomized comparison of propofol, sufentanil and midazolam infusions revealed similar effects on hemodynamics, oxygen consumption, and rate of myocardial ischemia after aortic surgery, although propofol was associated with a quicker recovery compared with midazolam and sufentanil.

The use of continuous i.v. sedation is associated with prolongation of mechanical ventilation

STUDY OBJECTIVE

To determine whether the use of continuous i.v. sedation is associated with prolongation of the duration of mechanical ventilation.

DESIGN

Prospective observational cohort study.

SETTING

The medical ICU of Barnes-Jewish Hospital, a university-affiliated urban teaching hospital.

PATIENTS

Two hundred forty-two consecutive ICU patients requiring mechanical ventilation.

INTERVENTIONS

Patient surveillance and data collection.

MEASUREMENTS AND RESULTS

The primary outcome measure was the duration of mechanical ventilation. Secondary outcome measures included ICU and hospital lengths of stay, hospital mortality, and acquired organ system derangements. A total of 93 (38.4%) mechanically ventilated patients received continuous i.v. sedation while 149 (61.6%) patients received either bolus administration of i.v. sedation (n=64) or no i.v. sedation (n=85) following intubation. The duration of mechanical ventilation was significantly longer for patients receiving continuous i.v. sedation compared with patients not receiving continuous i.v. sedation (185+/-190 h vs 55.6+/-75.6 h; p<0.001). Similarly, the lengths of intensive care (13.5+/-33.7 days vs 4.8+/-4.1 days; p<0.001) and hospitalization (21.0+/-25.1 days vs 12.8+/-14.1 days; p<0.001) were statistically longer among patients receiving continuous i.v. sedation. Multiple linear regression analysis, adjusting for age, gender, severity of illness, mortality, indication for mechanical ventilation, use of chemical paralysis, presence of a tracheostomy, and the number of acquired organ system derangements, found the adjusted duration of mechanical ventilation to be significantly longer for patients receiving continuous i.v. sedation compared with patients who did not receive continuous i.v. sedation (148 h [95% confidence interval: 121, 175 h] vs 78.7 h [95% confidence interval: 68.9, 88.6 h]; p<0.001).

CONCLUSION

We conclude from these preliminary observational data that the use of continuous i.v. sedation may be associated with the prolongation of mechanical ventilation. This study suggests that strategies targeted at reducing the use of continuous i.v. sedation could shorten the duration of mechanical ventilation for some patients. Prospective randomized clinical trials, using well-designed sedation guidelines and protocols, are required to determine whether patient-specific outcomes (eg, duration of mechanical ventilation, patient comfort) can be improved compared with conventional sedation practices.

Propofol versus midazolam: safety and efficacy for sedating the severe trauma patient

Previous studies have compared sedation profiles with midazolam (Mz) and propofol (Pf), particularly in heterogeneous populations of patients. Decreases in blood pressure and heart rate have been reported after the administration of propofol. These side effects are potentially deleterious in severe trauma patients, particularly in patients with head trauma. To assess the safety and efficacy of Mz and Pf, alone or in combination, in the prolonged sedation of severe trauma patients, we designed a prospective, controlled, randomized, study. One hundred consecutively admitted trauma patients requiring mechanical ventilation and sedation for more than 48 h were studied. Patients were sedated according to three different protocols based on the continuous i.v. administration of Mz alone, Pf alone, and Mz in combination with Pf. All patients received morphine chloride. Safety and efficacy were assessed during the sedation and wake-up periods according to clinical and laboratory variables. Cerebral hemodynamics were also studied in patients with head trauma. Patients were sedated for 6.3 +/- 4.0 days (mean +/- SD). All three sedation regimens were equally efficacious in achieving the desired sedation goal. The incidence of adverse events during the sedation period was also similar. In head trauma patients with intracranial pressure (ICP) monitoring, we did not find differences in ICP, cerebral perfusion pressure, or jugular venous oxygen saturation among the three groups. The serum triglyceride concentration was significantly higher in the Pf group. Wake-up time was significantly shorter in the Pf group. We conclude that both Mz and Pf are safe and efficacious in the sedation of severe trauma patients. The use of Pf in these patients is associated with a high incidence of hypertriglyceridemia and a shorter wake-up time.

IMPLICATIONS

In a prospective, controlled, randomized study, we confirmed the safety and efficacy of midazolam and propofol, alone or in combination, in the prolonged sedation of a homogeneous group of severe trauma patients, particularly in patients with head trauma. The propofol group had shorter wake-up times and higher triglyceride levels.

Synergistic sedation with propofol and midazolam in intensive care patients after coronary artery bypass grafting

OBJECTIVES

To evaluate and compare the clinical efficacy, impact on hemodynamics, safety profiles, and cost of combined administration of propofol and midazolam (synergistic sedation) vs. midazolam and propofol administered as sole agents, for sedation of mechanically ventilated patients after coronary artery bypass grafting.

DESIGN

Prospective, controlled, randomized, double-blind clinical trial.

SETTING

Intensive care unit of SCIAS-Hospital de Barcelona.

PATIENTS

Seventy-five mechanically ventilated patients who underwent coronary artery bypass graft surgery under low-dose opioid anesthesia.

INTERVENTIONS

According to the double-blind method, patients were randomly assigned to receive propofol (n = 25), midazolam (n = 25), or propofol combined with midazolam (n = 25). Infusion rates were adjusted to stay between 8 and 11 points on Glasgow Coma Score modified by Cook and Palma.

MEASUREMENTS AND MAIN RESULTS

Mean +/- SD duration of sedation was 14.4 +/- 1.5 hrs, 14.1 +/- 1.1 hrs, and 14.7 +/- 1.9 hrs for the propofol, midazolam, and synergistic groups, respectively. The induction dose was 0.55 +/- 0.05 mg/kg for propofol as sole agent, 0.05 +/- 0.01 mg/kg for midazolam as sole agent, and 0.22 +/- 0.03 mg/kg for propofol administered in combination with 0.02 +/- 0.00 mg/kg of midazolam (p = .001). The maintenance dose was 1.20 +/- 0.03 mg/kg/hr for propofol as sole agent, 0.08 +/- 0.01 mg/kg/hr for midazolam as sole agent, and 0.50 +/- 0.09 mg/kg/hr for propofol administered in combination with 0.03 +/- 0.01 mg/kg/hr of midazolam (p < .001). All sedative regimens achieved similar efficacy in percentage of hours of adequate sedation (93% for propofol, 88% for midazolam, and 90% for the synergistic group, respectively). After induction, both propofol and midazolam groups had significant decreases in systolic blood pressure, diastolic blood pressure, left atrial pressure, and heart rate. Patients in the synergistic group had significant bradycardia throughout the study, without impairment in other hemodynamic parameters. Patients sedated with propofol or synergistic regimen awoke sooner and could be extubated before those patients sedated with midazolam (0.9 +/- 0.3 hrs and 1.2 +/- 0.6 hrs vs. 2.3 +/- 0.8 hrs, respectively, p = .01). Synergistic sedation produced cost savings of 28% with respect to midazolam and 68% with respect to propofol.

CONCLUSIONS

In the study conditions, the new synergistic treatment with propofol and midazolam administered together is an effective and safe alternative for sedation, with some advantages over the conventional regimen with propofol or midazolam administered as sole agents, such as absence of hemodynamic impairment, >68% reduction in maintenance dose, and lower pharmaceutical cost.

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.

Pharmacokinetics of drugs used in critically ill adults

Critically ill patients exhibit a range of organ dysfunctions and often require treatment with a variety of drugs including sedatives, analgesics, neuromuscular blockers, antimicrobials, inotropes and gastric acid suppressants. Understanding how organ dysfunction can alter the pharmacokinetics of drugs is a vital aspect of therapy in this patient group. Many drugs will need to be given intravenously because of gastrointestinal failure. For those occasions on which the oral route is possible, bioavailability may be altered by hypomotility, changes in gastrointestinal pH and enteral feeding. Hepatic and renal dysfunction are the primary determinants of drug clearance, and hence of steady-state drug concentrations, and of efficacy and toxicity in the individual patient. Oxidative metabolism is the main clearance mechanism for many drugs and there is increasing recognition of the importance of decreased activity of the hepatic cytochrome P450 system in critically ill patients. Renal failure is equally important with both filtration and secretion clearance mechanisms being required for the removal of parent drugs and their active metabolites. Changes in the steady-state volume of distribution are often secondary to renal failure and may lower the effective drug concentrations in the body. Failure of the central nervous system, muscle, the endothelial system and endocrine system may also affect the pharmacokinetics of specific drugs. Time-dependency of alterations in pharmacokinetic parameters is well documented for some drugs. Understanding the underlying pathophysiology in the critically ill and applying pharmacokinetic principles in selection of drug and dose regimen is, therefore, crucial to optimising the pharmacodynamic response and outcome.

Propofol 2% in critically ill patients: effect on lipids

OBJECTIVE

To investigate the concentrations of triglyceride, cholesterol, and high-density lipoprotein during a 50-hr infusion of 2% propofol, starting within 24 hrs of admission to the intensive care unit (ICU).

DESIGN

Prospective, clinical study.

SETTING

ICU, university hospital.

PATIENTS

Thirty adult patients, who were ventilated and expected to be sedated for >2 days, were studied for 50 hrs, beginning at 1800 hrs on the first day of ICU admission.

MEASUREMENTS AND MAIN RESULTS

Triglyceride, cholesterol, and high-density lipoprotein were measured at 2000, 0400, and 0800 hrs. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and C-reactive protein were measured at 2000 hrs. Median cholesterol and high-density lipoprotein concentrations were at the low end of the normal range. In seven patients, peak triglyceride concentrations were >3 mmol/L up to a maximum of 4.83 mmol/L. Although there was no statistical difference in lipid concentrations between days 1 and 2, there was an apparent pattern of increasing triglyceride concentrations. There was a correlation between peak triglyceride concentration and total propofol consumption, but there was no correlation between lipids and age, gender, or Acute Physiology and Chronic Health Evaluation II scores. There was a direct correlation between triglyceride and C-reactive protein concentrations, and an inverse correlation between cholesterol and C-reactive protein. Twenty-two patients had evidence of TNF and 11 patients had an IL-6 of >1000 pg/mL, but there was no relationship between concentrations of cytokines and triglycerides in plasma.

CONCLUSIONS

Infusion of 2% propofol to critically ill patients over a 50-hr period does not result in a significant increase in triglyceride concentrations. Mean cholesterol and high-density lipoprotein concentrations were low throughout the study period. There was a significant direct correlation between triglyceride and C-reactive protein and an inverse correlation between cholesterol and C-reactive protein, suggesting that the changes in lipids in critically ill patients may be partly attributable to the acute-phase response.

Midazolam versus propofol for long-term sedation in the ICU: a randomized prospective comparison

OBJECTIVE

To compare the efficacy, safety, and cost of midazolam and propofol in prolonged sedation of critically ill patients.

DESIGN

Randomized, prospective study.

SETTING

General intensive care unit (ICU) in a 1100-bed teaching hospital.

PATIENTS

67 critically ill, mechanically ventilated patients.

INTERVENTIONS

Patients were invasively monitored and mechanically ventilated. A loading dose [midazolam 0.11 +/- 0.02 (SEM) mg.kg-1, propofol 1.3 +/- 0.2 mg.kg-1] was administered, followed by continuous infusion, titrated to achieve a predetermined sedation score. Sedation was continued as long as clinically indicated.

MEASUREMENTS AND RESULTS

Mean duration of sedation was 141 and 99 h (NS) for midazolam and propofol, respectively, at mean hourly doses of 0.070 +/- 0.003 mg.kg-1 midazolam and 1.80 +/- 0.08 mg.kg-1 propofol. Overall, 68% of propofol patients versus 31% of midazolam (p < 0.001) patients had a > 20% decrease in systolic blood pressure after the loading dose, and 26 versus 45% (p < 0.01) showed a 25% decrease in spontaneous minute volume. Propofol required more daily dose adjustments (2.1 +/- 0.1 vs 1.4 +/- 0.1, p < 0.001). Nurse-rated quality of sedation with midazolam was higher (8.2 +/- 0.1 vs 7.3 +/- 0.1 on a 10-cm visual analog scale, p < 0.001). Resumption of spontaneous respiration was equally rapid. Recovery was faster after propofol (p < 0.02), albeit with a higher degree of agitation. Amnesia was evident in all midazolam patients but in only a third of propofol patients. The cost of propofol was 4-5 times higher.

CONCLUSIONS

Both drugs afforded reliable, safe, and controllable long-term sedation in ICU patients and rapid weaning from mechanical ventilation. Midazolam depressed respiration, allowed better maintenance of sedation, and yielded complete amnesia at a lower cost, while propofol caused more cardiovascular depression during induction.