Remifentanil

Remifentanil vs. dexmedetomidine for cardiac surgery patients with noninvasive ventilation intolerance: a multicenter randomized controlled trial

BACKGROUND

The optimal sedative regime for noninvasive ventilation (NIV) intolerance remains uncertain. The present study aimed to assess the efficacy and safety of remifentanil (REM) compared to dexmedetomidine (DEX) in cardiac surgery patients with moderate-to-severe intolerance to NIV.

METHODS

In this multicenter, prospective, single-blind, randomized controlled study, adult cardiac surgery patients with moderate-to-severe intolerance to NIV were enrolled and randomly assigned to be treated with either REM or DEX for sedation. The status of NIV intolerance was evaluated using a four-point NIV intolerance score at different timepoints within a 72-h period. The primary outcome was the mitigation rate of NIV intolerance following sedation.

RESULTS

A total of 179 patients were enrolled, with 89 assigned to the REM group and 90 to the DEX group. Baseline characteristics were comparable between the two groups, including NIV intolerance score [3, interquartile range (IQR) 3-3 vs. 3, IQR 3-4, p = 0.180]. The chi-squared test showed that mitigation rate, defined as the proportion of patients who were relieved from their initial intolerance status, was not significant at most timepoints, except for the 15-min timepoint (42% vs. 20%, p = 0.002). However, after considering the time factor, generalized estimating equations showed that the difference was statistically significant, and REM outperformed DEX (odds ratio = 3.31, 95% confidence interval: 1.35-8.12, p = 0.009). Adverse effects, which were not reported in the REM group, were encountered by nine patients in the DEX group, with three instances of bradycardia and six cases of severe hypotension. Secondary outcomes, including NIV failure (5.6% vs. 7.8%, p = 0.564), tracheostomy (1.12% vs. 0%, p = 0.313), ICU LOS (7.7 days, IQR 5.8-12 days vs. 7.0 days, IQR 5-10.6 days, p = 0.219), and in-hospital mortality (1.12% vs. 2.22%, p = 0.567), demonstrated comparability between the two groups.

CONCLUSIONS

In summary, our study demonstrated no significant difference between REM and DEX in the percentage of patients who achieved mitigation among cardiac surgery patients with moderate-to-severe NIV intolerance. However, after considering the time factor, REM was significantly superior to DEX. Trial registration ClinicalTrials.gov (NCT04734418), registered on January 22, 2021. URL of the trial registry record: https://register.

CLINICALTRIALS

gov/prs/app/action/SelectProtocol?sid=S000AM4S&selectaction=Edit&uid=U00038YX&ts=3&cx=eqn1z0 .

Monitoring and modulation of respiratory drive in patients with acute hypoxemic respiratory failure in spontaneous breathing

Non-invasive respiratory support, namely, non-invasive ventilation, continuous positive airway pressure, and high-flow nasal cannula, has been increasingly used worldwide to treat acute hypoxemic respiratory failure, giving the benefits of keeping spontaneous breathing preserved. In this scenario, monitoring and controlling respiratory drive could be helpful to avoid patient self-inflicted lung injury and promptly identify those patients that require an upgrade to invasive mechanical ventilation. In this review, we first describe the physiological components affecting respiratory drive to outline the risks associated with its hyperactivation. Further, we analyze and compare the leading strategies implemented for respiratory drive monitoring and discuss the sedative drugs and the non-pharmacological approaches used to modulate respiratory drive during non-invasive respiratory support. Refining the available techniques and rethinking our therapeutic and monitoring targets can help critical care physicians develop a personalized and minimally invasive approach.

Omission of perioperative morphine reduces postoperative pain in proctological interventions: a single-center analysis

There is an increase in outpatient procedures and this trend will continue in the future. For hemorrhoidectomy, it is the standard of treatment in many health care systems. Perioperative management including adequate pain control is of paramount importance to ensure successful ambulatory surgery. This study investigates the role and effect of morphine compared to short-acting opiates applied before, during, or after proctological interventions and with focus on hemorrhoidectomy. A retrospective analysis of a prospective database was conducted comparing two populations. The control cohort received morphine (Yes-Mô) intra- and postoperatively, while the intervention group did not receive morphine (No-Mô) between January 2018 and January 2020. Both cohorts were balanced by propensity score matching. The outcomes were postoperative pain measured by numeric ratings scale (NRS) one hour postoperatively, pain 24 h postoperatively, success rate of outpatient management, and complication rate including postoperative nausea and vomiting as well as urinary retention. The intervention population comprised 54 patients and the control group contained 79 patients. One hour after surgery, patients in No-Mô reported lower NRS (1.44 ± 1.41) compared to Yes-Mô (2.48 ± 2.30) (p = 0.029). However, there was no difference in NRS 24 h postoperatively (No-Mô: 1.61 ± 1.41 vs Yes-Mô: 1.63 ± 1.72; p = 0.738). 100% of No-Mô was managed as outpatients while only 50% of Yes-Mô was dismissed on the day of the operation (p = < 0.001). There was no difference in postoperative complications (including postoperative nausea and vomiting (PONV) and urinary retention) between the two groups (PONV No-Mô 7.4% vs Yes-Mô 5.6%, p = 1.0 and urinary retention No-Mô 3.7% vs Yes-Mô 7.4%, p = 0.679). No-Mô received an oral morphine equivalent of 227.25 ± 140.35 mg intraoperatively and 11.02 ± 18.02 mg postoperatively. Yes-Mô received 263.17 ± 153.60 mg intraoperatively and 15.97 ± 14.17 mg postoperatively. The difference in received morphine equivalent between the groups was not significant after matching for the intraoperative (p = 0.212) and postoperative (p = 0.119) received equivalent. Omission of perioperative morphine is a viable but yet not understood method for reducing postoperative pain. Omission of morphine leads to a lower use of total morphine equivalent to attain satisfactory analgesia. The reduction of the overall opiate load and using opiates with a very short half-life potentially leads to a reduction of side effects like sedation. This in turn promotes discharge of the patient on the day of surgery. Omission of morphine is safe and does not increase postoperative complications.

Efficacy of Remifentanil in Patients Undergoing Cardiac Surgery: A Systematic Review and Network Meta-Analysis

Remifentanil, characterized by its ultra-short action duration and nonorgan-dependent metabolism, is applied in postcardiac surgery settings worldwide. While previous studies have compared its efficacy with that of other opioids, it has never been compared to a single specific opioid. Here, we evaluated whether remifentanil shortens mechanical ventilation (MV) times in patients after cardiac surgery. We identified randomized controlled trials that compared various opioids in adults (≥18 years) admitted to the intensive care unit after cardiac surgery. The primary outcome was the duration of MV, expressed as the mean difference (MD) in minutes, with a 95% confidence interval (CI). A 60-min reduction was considered significant based on prior research. Data were sourced from MEDLINE, the Cochrane Central Register of Controlled Trials, EMBASE, the World Health Organization International Clinical Trials Platforms Search Portal, and ClinicalTrials.gov, and a frequentist network meta-analysis was conducted. The eight identified studies indicate no differences in the duration of MV between remifentanil and fentanyl (MD 0.09 min; 95%CI -36.89-37.08), morphine (MD -19 min; 95%CI -55.86-16.21), or sufentanil (MD -2.44 min; 95%CI -67.52-62.55). Our study revealed that remifentanil did not reduce MV times in patients after cardiac surgery. The study protocol was registered with the Open Science Forum (https://osf.io/) (DOI 10.17605/OSF.IO/YAHW2).

Efficacy, safety, and pharmacokinetics of MR13A11A, a generic of remifentanil, for pain management of Japanese patients in the intensive care unit: a double-blinded, fentanyl-controlled, randomized, non-inferiority phase 3 study

BACKGROUND

The aims of this study were to evaluate the efficacy, safety, and pharmacokinetics (PK) of continuous intravenous administration of remifentanil in mechanically ventilated patients in the intensive care unit (ICU).

METHODS

This was a multicenter, randomized, double-blinded, fentanyl-controlled, non-inferiority phase 3 study. Patients aged ≥ 20 years requiring 6 h to 10 days mechanical ventilation in an ICU and requiring pain relief were randomly assigned in a 1:1 ratio to receive either remifentanil (n = 98) or fentanyl (n = 98). Dose was titrated from an infusion rate of 1 mL/h (remifentanil: 0.025 µg/kg/min, fentanyl: 0.1 µg/kg/h) until the target level of analgesia (behavioral pain scale [BPS] ≤ 5 or numerical rating score [NRS] ≤ 3) was achieved by escalating the dose in 1 mL/h increasing. Administration was then adjusted to maintain the target level of analgesia until weaning from the ventilator. The primary endpoint was the proportion of patients who did not require rescue fentanyl. Safety was assessed according to standard procedures. PK of remifentanil in the arterial blood was assessed in 24 patients.

RESULTS

The proportion of patients achieving the primary endpoint in the remifentanil and fentanyl groups was 100% (92/92) and 97.8% (88/90), respectively. The difference between the groups was 2.2% (95% confidence interval, - 0.8-5.3) and non-inferiority of remifentanil to fentanyl was verified (p < 0.0001). The incidences of any adverse events in the remifentanil and fentanyl groups was 34 of 92 patients (37.0%) and 34 of 90 patients (37.8%), respectively. Adverse drug reactions was 12 in 92 patients (13.0%) and 15 in 90 patients (16.7%), respectively. In the PK analysis, blood remifentanil concentration decreased within 10 min to almost 50% of the end of administration, suggesting rapid offset of action following discontinuation of remifentanil.

CONCLUSIONS

Remifentanil can be used safely for pain management in mechanically ventilated Japanese patients in the ICU.

TRIAL REGISTRATION

Japan Registry of Clinical Trials, jRCT2080224954. Registered 20 November 2019, https://jrct.niph.go.jp/latest-detail/jRCT2080224954 .

A pharmacologically pre-contracted smooth muscle bowel model for the study of highly-potent opioid receptor agonists and antagonists

Isolated organ models are a versatile tool for pharmacological and toxicological research. Small bowel has been used to assess the inhibition of smooth muscle contraction by opioids. In the present study, we set out to establish a pharmacologically stimulated rat bowel model. The effects of carfentanil, remifentanil and the new synthetic opioid U-48800 and their respective antagonists naloxone, nalmefene and naltrexone were studied in a small bowel model in rats. The IC₅₀ values of the tested opioids were as follows: carfentanil (IC₅₀ = 0.02 µmol/L, CI 0.02-0.03 µmol/L) ≫ remifentanil (IC₅₀ = 0.51 µmol/L, CI 0.40-0.66 µmol/L) ≫ U-48800 (IC₅₀ = 1.36 µmol/L, CI 1.20-1.54 µmol/L). The administration of the opioid receptor antagonists naloxone, naltrexone and nalmefene led to progressive, parallel rightward shifts of the dose-response curves. Naltrexone was most potent in antagonizing the effects of U-48800, whereas naltrexone and nalmefene were most effective in antagonizing the effects of carfentanil. In summary, the current model seems to be a robust tool to study opioid effects in a small bowel model without the necessity of using electrical stimulation.

Comparison of dexmedetomidine and remifentanil on reducing coughing during emergence from anesthesia with tracheal intubation: A meta-analysis

Background: Dexmedetomidine and remifentanil are well known to suppress airway reflex during emergence from anesthesia, but which one is more effective is unclear. We conducted a meta-analysis to compare the effect of dexmedetomidine and remifentanil on reducing the occurrence of coughing.

Methods: We systematically searched PubMed, Embase, and Cochrane Library for randomized controlled trials (published between 1 January 1950, and 30 December 2021; no language restrictions) comparing dexmedetomidine infusion with remifentanil infusion. The primary endpoint was the incidence of moderate to severe coughing during the recovery period. The secondary endpoints were the time of recovery and extubation, and residual sedation. We assessed pooled data by using a random-effects model.

Results: Eight studies with 502 participants were included. The meta-analysis showed no statistically difference between dexmedetomidine and remifentanil in the occurrence of moderate to severe coughing during emergence from anesthesia (OR 1.45,95%CI 0.62–3.38), the extubation time (MD 0.93 min, 95%CI -0.28–2.14), and the residual sedation (OR 2.52, 95%CI 0.92–6.91). Compared with dexmedetomidine, the average recovery time of remifentanil was shorter (MD 3.88 min, 95%CI 1.01–6.75).

Conclusion: Dexmedetomidine and remifentanil infusion had no difference in the occurrence of moderate to severe coughing during emergence from anesthesia.

Clinical Trial Registration:https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42021239710

Ultrasound-guided paravertebral blockade reduced perioperative opioids requirement in pancreatic resection: A randomized controlled trial

Background

Perioperative opioid use for pain control has been found to be associated with side effects and adverse prognosis. In this study, we hypothesized that paravertebral block could reduce the consumption of opioids during pancreatic resection surgery.

Methods

We conducted a prospective, randomized trial. Patients with resectable pancreatic cancer were randomly assigned to one of the two groups: those who received bilateral paravertebral block combined with general anesthesia [bilateral paravertebral blockade (PTB) group] or those who received only general anesthesia (Control group). The primary endpoint was the perioperative consumption of opioids (sufentanil and remifentanil). The main secondary endpoints were pain scores, complications, and serum cytokine levels.

Results

A total of 153 patients were enrolled in the study and 119 cases were analyzed. Compared to the control group, patients in PTB patients had significantly lower perioperative (30.81 vs. 56.17 µg), and intraoperative (9.58 vs. 33.67 µg) doses of sufentanil (both p &lt; 0.001). Numerical rating scale scores of pain were comparable between the two groups. No statistical differences in complications were detected.

Conclusion

Bilateral paravertebral block combined with general anesthesia reduced the perioperative consumption of opioids by 45%.

Registration number

ChiCTR1800020291 (available on http://www.chictr.org.cn/).

Comparison between remifentanil and other opioids in adult critically ill patients: A systematic review and meta-analysis

BACKGROUND AND AIMS

To identify the efficacy and safety of remifentanil when compared with other opioids in adult critically ill patients.

METHODS

We searched for studies in the Cochrane Library, MEDLINE, and EMBASE that had been published up to May 31st, 2019. Randomized clinical trials using remifentanil comparing with other opioids for analgesia were included. Two reviewers independently applied eligibility criteria, assessed quality, and extracted data. Duration of mechanical ventilation was the primary outcome, and secondary outcomes included weaning time, intensive care unit (ICU), length of stay (LOS), hospital LOS, mortality, side effects, and costs.

RESULTS

Fifteen studies with 1233 patients were included. Remifentanil was associated with a significant reduction in the duration of mechanical ventilation in the adult ICU patients when compared with other opioids (P = .01). Remifentanil also reduced the weaning time (P = .02) and the ICU LOS when compared with other opioids (P = .01). There was no difference in the hospital LOS (P = .15), side effects (P = .39), and mortality (P = .79) between remifentanil and other opioids, what's more, remifentanil increased the costs of anesthesia (P < .001) but did not increase cost of hospitalization (P = .30) when comparing with other opioids.

CONCLUSIONS

Remifentanil reduced the duration of mechanical ventilation, weaning time, and ICU LOS when compared with other opioids in adult critically ill patients. Higher quality RCTs are necessary to prove our findings.

PROSPERO REGISTRATION NUMBER

CRD42016041438.

Remifentanil provides an increased proportion of time under light sedation than fentanyl when combined with dexmedetomidine for mechanical ventilation

Objective

To compare the effects of remifentanil versus fentanyl during light sedation with dexmedetomidine in adults receiving mechanical ventilation (MV) in the intensive care unit.

Methods

In this retrospective cohort study, we compared the use of remifentanil versus fentanyl in adults receiving MV with dexmedetomidine sedation. The primary outcome was the proportion of time under light sedation (Richmond Agitation–Sedation Scale score between −1 and 0) during MV.

Results

We included 94 patients and classified 58 into the remifentanil group and 36 into the fentanyl group. The mean proportion of time under light sedation during MV was 66.6% ± 18.5% in the remifentanil group and 39.9% ± 27.3% in the fentanyl group. In the multivariate analysis with control for confounding factors, patients in the remifentanil group showed a significantly higher proportion of time under light sedation than patients in the fentanyl group (mean difference: 24.3 percentage points; 95% confidence interval: 12.9–35.8).

Conclusions

Remifentanil use might increase the proportion of time under light sedation in patients receiving MV compared with fentanyl administration.

Clinical efficacy of intravenous anesthesia on breast segmental surgery and its effects on oxidative stress response and hemodynamics of patients

This study was designed to investigate the clinical efficacy of intravenous anesthesia on breast segmental surgery and the effects on hemodynamics of patients. A total of 267 patients were collected as research subjects. These patients underwent breast segmental surgery in Chun'an First People's Hospital from March 2015 to September 2018. Among them, 137 patients undergoing intravenous anesthesia were the research group, and 130 patients undergoing inhalation anesthesia were the control group. The following parameters were recorded: Clinical efficacy, postoperative adverse conditions, hemodynamic indicators including systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). Visual analogue scale (VAS) was used to observe the analgesic effect of the two groups, the mental state of patients in the two groups was observed by mini-mental state examination (MMSE) scoring method, and systemic evaluation was made by oxidative stress (OS) reaction indicators. The MMSE scores of the two groups decreased one day after surgery, but the score in the research group was higher than that in the control group (P<0.05). The levels of SBP and DBP at T1 and T2 in the control group were significantly higher than those in the research group (P<0.05). HR of research group at T1 and T2 was lower than that at T0 and that at corresponding time of control group (P<0.05). The incidence rate of postoperative adverse reactions in the research group was significantly lower than that in the control group (P<0.05). In conclusion, intravenous anesthesia for breast segmental surgery can reduce the occurrence of adverse reactions after surgery, with complete sedation and analgesia. Patients were able to wake up quickly and stably after surgery, and their cognitive function and OS recovered rapidly. However, due to the great impact on hemodynamics during surgery, attention should be paid to maintain hemodynamic stability during surgery to avoid hypotension and bradycardia.

Ketamine Infusion in Post-Surgical Pain Management after Head and Neck Surgery: A Retrospective Observational Study

Background:

Head and neck cancer affects approximately 382,000 new patients per year worldwide with a significant portion undergoing surgical treatment. During postoperative period key elements in the Intensive Care Unit (ICU) are airway management and pain control.

Objective:

We evaluated the average change of inpatient pain control using a Numerical Rating Score (NRS). We also evaluated the time of extubation after ICU admission recording the incidence of desaturation and the necessity of re-intubation. Secondary outcomes were the incidence of postoperative complications, included those narcotics-related, and the use of rescue analgesics.

Methods:

In this retrospective observational study, we analyzed data of registry before and after we have changed our postoperative analgesic protocol from remifentanil infusion to ketamine infusion.

Results:

Medical records of 20 patients were examined. 10 patients received 0.5 mg/kg ketamine bolus at the end of surgery, followed by a continuous infusion of 0.25 mg/kg/h. All patients presented a significant decrease in pain intensity from the 4th to 48th postoperative hour (p < 0.05), but statically not a significant difference in NRS score was recorded between the two groups. Time to extubation was shorter in ketamine group compared to the remifentanil group (112.30 min ± 16.78 vs. 78 min ± 14.17; p < 0.05). Desaturation rate was 10% in the remifentanil group, while no case was recorded in the ketamine group.

Conclusion:

The level of analgesia provided by ketamine and remifentanil was comparable. Ketamine was superior in ventilatory management of the patient with more rapid extubation and with no case of desaturation.

A national survey on routines regarding sedation in Swedish intensive care units

Background: Previous studies concerning sedation in Swedish intensive care units (ICU) have shown variability in drug choices and strategies. Currently, there are no national guidelines on this topic. As an update to a Nordic survey from 2004, and as a follow-up to a recently introduced quality indicator from the Swedish Intensive Care Registry, we performed a national survey. Methods: A digital survey was sent to the ICUs in Sweden, asking for sedation routines regarding hypnosedatives, analgosedatives, protocols, sedation scales, etc. Results: Fifty out of 80 ICUs responded to the survey. All units used sedation scales, and 88% used the RASS scale; 80% used written guidelines for sedation. Propofol and dexmedetomidine were the preferred short-term hypnosedatives. Propofol, dexmedetomidine, and midazolam were preferred for long-term hypnosedation. Remifentanil, morphine, and fentanyl were the most frequently used agents for analgosedation. Conclusions: All ICUs used a sedation scale, an increase compared with previous studies. Concerning the choice of hypno- and analgosedatives, the use of dexmedetomidine, clonidine, and remifentanil has increased, and the use of benzodiazepines has decreased since the Nordic survey in 2004.

Remifentanil–ketamine vs. propofol–ketamine for sedation in pediatric patients undergoing colonoscopy: A randomized clinical trial

Background and objectives

Pediatric patients frequently require deep sedation or general anesthesia for colonoscopy. This study was designed to compare the sedative efficacy of remifentanil–ketamine combination with propofol–ketamine combination in children undergoing colonoscopy.

Methods

Seventy patients, between 2 and 16 years of age, scheduled for diagnostic colonoscopy were randomly allocated into two groups. Remifentanil–ketamine group received intravenous ketamine 2 mg.kg⁻¹ and remifentanil 0.25 μg.kg⁻¹ combination, followed by 0.1 μg.kg⁻¹.min⁻¹ remifentanil infusion. Propofol–ketamine group received intravenous propofol 1 and 2 mg.kg⁻¹ ketamine combination, followed by 1 mg.kg⁻¹.h⁻¹ propofol infusion. In the case of children discomfort (cry, movement, and cough), remifentanil 0.1 μg.kg⁻¹ in the remifentanil–ketamine group or propofol 0.5 mg.kg⁻¹ in the propofol–ketamine group were administered to improve children discomfort. Despite the therapy given above, if children still experience discomfort, 1 mg.kg⁻¹ of ketamine was administered as a rescue drug, regardless of the group. Ramsay sedation score, hemodynamic variables, drug requirements, gastroenterologists’ satisfaction, colonoscopy duration, recovery time, and side effects were recorded throughout the procedure and the recovery period.

Results

The percentage of patients with a Ramsay sedation score of 4 or higher during the procedure was 73.5 and 37.1% in remifentanil–ketamine and propofol–ketamine groups, respectively (p = 0.02). Systolic and diastolic blood pressure variables were significantly higher only after induction in the remifentanil–ketamine group than in the propofol–ketamine group (p = 0.015).

Conclusion

Coadministration of ketamine with either remifentanil or propofol effectively and safely provides sedation and analgesia in children undergoing colonoscopy. Sedation scores were significantly better in remifentanil–ketamine group than in propofol–ketamine group.

[Remifentanil-ketamine vs. propofol-ketamine for sedation in pediatric patients undergoing colonoscopy: A randomized clinical trial]

BACKGROUND AND OBJECTIVES

Pediatric patients frequently require deep sedation or general anesthesia for colonoscopy. This study was designed to compare the sedative efficacy of remifentanil-ketamine combination with propofol-ketamine combination in children undergoing colonoscopy.

METHODS

Seventy patients, between 2 and 16 years of age, scheduled for diagnostic colonoscopy were randomly allocated into two groups. Remifentanil-ketamine group received intravenous ketamine 2mg.kg^-1 and remifentanil 0.25μg.kg^-1 combination, followed by 0.1μg.kg^-1.min^-1 remifentanil infusion. Propofol-ketamine group received intravenous propofol 1 and 2mg.kg^-1 ketamine combination, followed by 1mg.kg^-1.h^-1 propofol infusion. In the case of children discomfort (cry, movement, and cough), remifentanil 0.1μg.kg^-1 in the remifentanil-ketamine group or propofol 0.5mg.kg^-1 in the propofol-ketamine group were administered to improve children discomfort. Despite the therapy given above, if children still experience discomfort, 1mg.kg^-1 of ketamine was administered as a rescue drug, regardless of the group. Ramsay sedation score, hemodynamic variables, drug requirements, gastroenterologists' satisfaction, colonoscopy duration, recovery time, and side effects were recorded throughout the procedure and the recovery period.

RESULTS

The percentage of patients with a Ramsay sedation score of 4 or higher during the procedure was 73.5 and 37.1% in remifentanil-ketamine and propofol-ketamine groups, respectively (p=0.02). Systolic and diastolic blood pressure variables were significantly higher only after induction in the remifentanil-ketamine group than in the propofol-ketamine group (p=0.015).

CONCLUSION

Coadministration of ketamine with either remifentanil or propofol effectively and safely provides sedation and analgesia in children undergoing colonoscopy. Sedation scores were significantly better in remifentanil-ketamine group than in propofol-ketamine group.

The Effects of Remifentanil on Expression of High Mobility Group Box 1 in Septic Rats

High mobility group box 1 (HMGB1) is a pivotal mediator of sepsis progression. Remifentanil, an opioid agonist, has demonstrated anti-inflammatory effects in septic mice. However, it is not yet known whether remifentanil affects the expression of HMGB1. We investigated the effects of remifentanil on HMGB1 expression and the underlying mechanism in septic rats. Forty-eight male Sprague-Dawley rats were randomly divided into 3 groups; a sham group, a cecal ligation and puncture (CLP) group, and a CLP with remifentanil treatment (Remi) group. The rat model of CLP was used to examine plasma concentrations of proinflammatory cytokines, tissue HMGB1 mRNA and the activity of nuclear factor (NF)-κB in the liver, lungs, kidneys, and ileum. Pathologic changes and immunohistochemical staining of NF-κB in the liver, lungs, and kidneys tissue were observed. We found that remifentanil treatment suppressed the level of serum interleukin (IL)-6 and tumor necrosis factor (TNF)-α 6 hours after CLP, and serum HMGB1 24 hours after CLP. HMGB1 mRNA levels and the activity of NF-κB in multiple organs decreased by remifentanil treatment 24 hours after CLP. Remifentanil treatment also attenuated nuclear expression of NF-κB in immunohistochemical staining and mitigated pathologic changes in multiple organs. Altogether, these results suggested that remifentanil inhibited expression of HMGB1 in vital organs and release of HMGB1 into plasma. The mechanism was related to the inhibitory effect of remifentanil on the release of proinflammatory cytokines and activation of NF-κB.

Remifentanil, ketamine, and fospropofol: a review of alterative continuous infusion agents for sedation in the critically ill

Sedation and analgesia are integral aspects in the care of critically ill patients admitted to the intensive care unit. In recent years, many of the commonly used sedative agents in the United States have experienced manufacturing and sterility issues leading to decreased availability. In addition, current practice has shifted to providing lighter levels of sedation as clinicians have gained a better understanding of the consequences of prolonged deep sedation. Benzodiazepines have fallen out of favor due to findings including increased delirium and duration of mechanical ventilation. Alterations in end-organ function in critically ill patients may also lead to varied responses to commonly used sedatives. With numerous factors impacting choice of sedation in the intensive care unit, fospropofol, ketamine, and remifentanil have been considered potential alternatives to standard therapy. The purpose of this review was to discuss strategies for the safe and effective use of fospropofol, ketamine, and remifentanil for continuous intravenous sedation in critically ill patients.

Propofol-ketamine or propofol-remifentanil for deep sedation and analgesia in pediatric patients undergoing burn dressing changes: a randomized clinical trial

OBJECTIVE

In this study, we compared the propofol-ketamine and propofol-remifentanil combinations for deep sedation and analgesia during pediatric burn wound dressing changes.

METHODS

Fifty pediatric patients aged 12-36 months, undergoing burn wound dressing changes, were randomly assigned to receive propofol-remifentanil (group PR) or propofol-ketamine (group PK) for deep sedation and analgesia. Patients in the group PR received 2 mg·kg(-1) propofol and 0.1 μg·kg(-1) remifentanil, and 0.05 μg·kg(-1) ·min(-1) remifentanil was infused continuously until the end of the procedure. Patients in the group PK received 2 mg·kg(-1) propofol and 1 mg·kg(-1) ketamine, and the same volume of isotonic saline was infused continuously until the end of the procedure. Additional propofol with remifentanil or ketamine was administered when required. Hemodynamic variables, drug requirements, occurrence of patient movement, surgeon's satisfaction score, recovery time, and the incidence of adverse events were recorded throughout the procedure and recovery.

RESULTS

Recovery time was significantly shorter in the group PR compared to that in the group PK (10.3 [9.1-11.5] min vs 22.5 [20.3-25.6] min, median [interquartile range], respectively; P < 0.001). No significant hypotension or bradycardia occurred throughout the procedure. No significant differences were observed in terms of drug requirements, occurrence of patient movement, surgeon's satisfaction, incidence of respiratory depression, hypoxia, or nausea and vomiting

CONCLUSIONS

The combinations of propofol-ketamine and propofol-remifentanil were effective for sedation and analgesia in pediatric patients undergoing burn dressing changes, but the propofol-remifentanil combination provided faster recovery compared to the propofol-ketamine combination.

Efficacy and safety of analgosedation with fentanyl compared with traditional sedation with propofol

OBJECTIVES

To compare the efficacy and safety of analgosedation with fentanyl versus traditional sedation with propofol in critically ill patients receiving mechanical ventilation.

METHODS

Retrospective, observational study evaluating adult critically ill patients on mechanical ventilation at a community teaching hospital who received continuous infusion fentanyl (n=50) or propofol (n=50) from September 2011-March 2013.

RESULTS

Median duration of mechanical ventilation was similar between patients receiving propofol and fentanyl infusions (46.7 hr vs 46.0 hr, p=0.19). No difference was noted in median intensive care unit length of stay between groups (p=0.42). A larger percentage of patients receiving propofol required rescue opioids compared with patients receiving fentanyl (56% vs 34%, p=0.04). Furthermore, patients receiving propofol required significantly more rescue opioid therapy during the course of mechanical ventilation as calculated by fentanyl equivalents (150 μg vs 100 μg, p=0.03). No difference in the rate of intensive care unit delirium was noted between groups (fentanyl 23% vs propofol 27%, p=0.80).

CONCLUSION

Analgosedation with fentanyl appears to be a safe and effective strategy to facilitate mechanical ventilation. This regimen does not appear to affect duration of mechanical ventilation when compared with propofol, but may allow for more optimal pain management in critically ill patients.

Direct effects of morphine but not of fentanyl-type opioids on human 5-HT3A receptors in outside-out patch-clamp studies

BACKGROUND

The alkaloid morphine is historically the oldest opiate, yet still today it has clinically important uses in analgesic therapies. The main analgesic effect of opioids, including synthetic opioids belonging to the family of 4-anilidopiperidines, is mediated via activation of opioid receptors spread throughout the peripheral and central nervous system. However, morphine acting as a 'dirty' drug also exhibits effects on other receptor systems, e.g., the serotonergic system and its 5-HT3 receptor. Therefore, this study focuses on the interaction of morphine and fentanyl-type opioids (alfentanil, remifentanil and sufentanil) with 5-HT3A receptors.

METHODS

Excised outside-out patches from human embryonic kidney-293 cells, stably transfected with the human 5-HT3A receptor cDNA, were used to determine the opioid effects using the patch-clamp technique.

RESULTS

Within clinical concentrations, the effects of morphine are concentration-dependent. Morphine reduced current amplitudes, as well as activation and decay time constants. These effects were not competitive. Contrary to these results, all fentanyl-type opioids only exerted effects far above their clinical concentration ranges. These effects were not homogenous but varying.

CONCLUSIONS

Morphine is an opioid compound exhibiting special antagonistic interaction with 5-HT3A receptors. This interaction is not shared by the newer synthetic derivatives of the fentanyl-type opioids in the clinical relevant concentration range.

Fentanyl-related compounds and derivatives: current status and future prospects for pharmaceutical applications

Fentanyl and its analogs have been mainstays for the treatment of severe to moderate pain for many years. In this review, we outline the structural and corresponding synthetic strategies that have been used to understand the structure-biological activity relationship in fentanyl-related compounds and derivatives and their biological activity profiles. We discuss how changes in the scaffold structure can change biological and pharmacological activities. Finally, recent efforts to design and synthesize novel multivalent ligands that act as mu and delta opioid receptors and NK-1 receptors are discussed.

Effects of remifentanil on processing of auditory stimuli: a combined MEG/EEG study

Remifentanil (Ultiva(®)) is a potent ultra-short acting mu-opioid receptor agonist used for perioperative pain treatment and anaesthesia. So far, it is not known how sensitive the cognitive processing of auditory perception elicited by the mismatch negativity (MMN) paradigm is to opioids. The present exploratory study investigated how the opioid remifentanil modulates different stages of auditory processing as reflected in the MMN(m) and P3a(m). We recorded electroencephalography (EEG) and magnetoencephalography (MEG) during auditory stimulation under remifentanil or placebo infusion in 20 healthy participants. For the MMN, a gender effect was found for tones deviating in frequency (± 10%) from the standard tone. Remifentanil increased the amplitude of the frequency MMN at F3 in females but not in males. No effect of treatment was found for the MMN(m) or the novel P3a(m). These results suggest that while the bottom-up stimulus change detection system for auditory stimuli appears to be relatively insensitive to opioids, the automatic attention switch caused by the change detection seems to be modulated by the opioid system in females. The multiple deviant paradigm including novel sounds is a promising tool for investigating pharmacological manipulation of different stages of auditory processing. Furthermore, combining the two techniques will yield more specific information about the drug effects on MMN(m).

Opiates do not violate the viability and proliferative activity of human articular chondrocytes

Articular cartilage injuries present a challenge for the clinician. Autologous chondrocyte implantation embedded in scaffolds are used to treat cartilage defects with favorable outcomes. Autologous serum is often used as a medium for chondrocyte cell culture during the proliferation phase of the process of such products. A previous report showed that opiate analgesics (fentanyl, alfentanil and diamorphine) in the sera have a significant inhibitory effect on chondrocyte proliferation. In order to determine if opiates in serum inhibit chondrocyte proliferation, twenty two patients who underwent knee arthroscopy and were anesthetized with either fentanyl or remifentanil were studied. Blood was drawn before and during opiate administration and up to 2 h after its discontinuation. The sera were used as medium for in vitro proliferation of both cryopreserved and freshly isolated chondrocytes, and the number and viability of cells were measured. There was no difference in the yield or cell viability between the serum samples of patients anesthetized with fentanyl when either fresh or cryopreserved human articular chondrocytes (hACs) were used. Some non-significant reduction in the yield of cells was observed in the serum samples of patients anesthetized with remifentanil when fresh hAC were used. We conclude that Fentanyl in human autologous serum does not inhibit in vitro hAC proliferation. Remifentanil may show minimal inhibitory effect on in vitro fresh hAC proliferation.

Sedation in neurological intensive care unit

Analgesia and sedation has been widely used in intensive care units where iatrogenic discomfort often complicates patient management. In neurological patients maximal comfort without diminishing patient responsiveness is desirable. In these patients successful management of sedation and analgesia incorporates a patient based approach that includes detection and management of predisposing and causative factors, including delirium, monitoring using sedation scales, proper medication selection, emphasis on analgesia based drugs and incorporation of protocols or algorithms. So, to optimize care clinician should be familiar with the pharmacokinetic and pharmacodynamic variables that can affect the safety and efficacy of analgesics and sedatives.

Remifentanil use in pediatric scoliosis surgery-an effective alternative to morphine (a retrospective study)

PURPOSE

The unique properties of remifentanil make it ideal for pediatric use despite a lack of wide randomized clinical trials and fear of adverse events due to its high potency. We aimed to consolidate preliminary conclusions regarding the efficacy of remifentanil use in pediatric scoliosis surgery.

MATERIALS AND METHODS

The medical charts of children with idiopathic scoliosis who underwent primary spinal fusion between 1998 and 2007 at a large tertiary university-affiliated hospital were retrospectively reviewed and divided into two groups according to anesthetic regime (remifentanil vs. morphine). Demographic, surgery-related details and immediate postoperative course were recorded and compared.

RESULTS

All 36 remifentanil children were extubated shortly after termination of surgery, compared to 2 of the 84 patients in the morphine group. The remaining patients in the morphine group were extubated hours after surgery [5.4 hours; standard deviation (SD) 1.7 hours]. Six remifentanil children were spared routine intensive care hospitalization (vs. 2 morphine children-significant difference). Shorter surgeries [5.6 hours (SD 1.82 hours) vs. 7.14 hours (SD 2.15 hours); p=0.0004] were logged for the remifentanil group. To achieve controlled hypotension during surgery, vasodilator agents were used in the morphine group only. A comparison of early postoperative major or minor complication rates (including neurological and pulmonary complications) between the two groups yielded no significant differences.

CONCLUSION

Remifentanil use can shorten operating time and facilitate earlier spontaneous ventilation and extubation, with less of a need for intensive care hospitalization and no increase in significant complications.

Adjunctive remifentanil infusion in deeply sedated and paralyzed ICU patients during fiberoptic bronchoscopy procedure: a prospective, randomized, controlled study

Background

Even with an adequate pain assessment, critically ill patients under sedation experience pain during procedures in the intensive care unit (ICU). We evaluated the effects of adjunctive administration of Remifentanil, a short-acting drug, in deeply sedated patient on variation of Bispectral Index (BIS) during a fiberoptic bronchoscopy.

Methods

A prospective, randomized, blinded, placebo-controlled study was conducted in 18-bed ICU. Patients needing a tracheal fibroscopy under deep sedation (midazolam (0.1 mg/kg per hour) fentanyl (4 μg/kg per hour)) and neuromuscular blocking (atracurium 0.5 mg/kg) were included in the study. A continuous monitoring of BIS, arterial pressure, and heart rate were realized before, during, and after the fiberoptic exam. An adjunctive continuous placebo or Remifentanil infusion was started just before the fiberoptic exam with a target effect-site concentration of 4 ng/ml using a Base Primea pump.

Results

Mean arterial pressure and heart rates were comparable between the placebo and Remifentanil groups at all times of the procedure. We did not observe differences in the variation of BIS values between the two groups during procedure. We described no change in BIS values relative to the placebo group in this population.

Conclusions

In deeply sedated and paralyzed patients, receiving analgesic support based on a scale score an additional administration of short-acting analgesic drug, such as Remifentanil, seems not to be necessary for acute pain control.

Trial registration

NCT00162591.

Cost-consequence analysis of remifentanil-based analgo-sedation vs. conventional analgesia and sedation for patients on mechanical ventilation in the Netherlands

INTRODUCTION

Hospitals are increasingly forced to consider the economics of technology use. We estimated the incremental cost-consequences of remifentanil-based analgo-sedation (RS) vs. conventional analgesia and sedation (CS) in patients requiring mechanical ventilation (MV) in the intensive care unit (ICU), using a modelling approach.

METHODS

A Markov model was developed to describe patient flow in the ICU. The hourly probabilities to move from one state to another were derived from UltiSAFE, a Dutch clinical study involving ICU patients with an expected MV-time of two to three days requiring analgesia and sedation. Study medication was either: CS (morphine or fentanyl combined with propofol, midazolam or lorazepam) or: RS (remifentanil, combined with propofol when required). Study drug costs were derived from the trial, whereas all other ICU costs were estimated separately in a Dutch micro-costing study. All costs were measured from the hospital perspective (price level of 2006). Patients were followed in the model for 28 days. We also studied the sub-population where weaning had started within 72 hours.

RESULTS

The average total 28-day costs were €15,626 with RS versus €17,100 with CS, meaning a difference in costs of €1474 (95% CI -2163, 5110). The average length-of-stay (LOS) in the ICU was 7.6 days in the RS group versus 8.5 days in the CS group (difference 1.0, 95% CI -0.7, 2.6), while the average MV time was 5.0 days for RS versus 6.0 days for CS. Similar differences were found in the subgroup analysis.

CONCLUSIONS

Compared to CS, RS significantly decreases the overall costs in the ICU.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00158873.

[Sedation and analgesia in intensive care: physiology and application]

Many therapeutic and diagnostic procedures in intensive care medicine are perceived as painful by most patients. As a consequence analgesia and sedation represent two of the main pillars in the treatment of the critically ill. Adaptation to the individual needs of the patients poses one of the biggest challenges that we are confronted with. Both morbidity and mortality can be positively influenced by adequate treatment. In the first part of this review we will discuss the physiology of sleep patterns and pain. Furthermore modes of action and side effects of the most common anesthetics and analgetics will be presented. Finally, the last part of the manuscript deals with the practical application of these therapeutics and their monitoring in intensive care medicine.

Attenuation of propofol tolerance conferred by remifentanil co-administration does not reduce propofol toxicity in rabbits under prolonged mechanical ventilation

BACKGROUND

Prolonged sedation with propofol at high doses may lead to fatal multi-organ dysfunction, know as propofol infusion syndrome. We tested the hypothesis that propofol plus remifentanil co-administration attenuates propofol tolerance to its sedative effect and assessed if such an effect has an impact on propofol toxicity in rabbits under prolonged mechanical ventilation.

MATERIALS AND METHODS

Eighteen healthy male rabbits were mechanically ventilated and received propofol (group P, n = 6), propofol plus remifentanil (group PR, n = 6), or remifentanil plus sevoflurane (group RS, n = 6) in order to be kept under sedation (group P) or sedation/analgesia (groups PR and RS) for up to 48 h. Initial propofol and remifentanil infusion rates (IRs) were adjusted, if needed, to maintain the desired level of sedation and analgesia, respectively (groups P and PR). In group RS, remifentanil was infused at IRs equivalent to those of group PR. Propofol IRs were recorded, propofol concentrations were measured in the arterial plasma, and blood biochemical parameters and organ histopathology were assessed.

RESULTS

Animals survived for 29-36 h in group P and 22-38 h in group PR (100% mortality rate). Tolerance was developed to propofol's sedative effect. The onset of tolerance was delayed and its magnitude was decreased in group PR compared with group P. Propofol was accumulated in the systemic circulation. Propofol clearance rate was gradually decreased. Arterial lactate, and serum aspartate aminotransferase (AST), lactate dehydrogenase (LDH), bilirubin, cholesterol, triglycerides, and creatine kinase (CK) levels were increased. The heart, lungs, liver, gallbladder, kidneys, urinary bladder, and skeletal muscles were seriously injured in groups P and PR. In group RS, mortality was 0%, while there was only mild injury of the lungs, liver, gallbladder, kidneys, and urinary bladder.

CONCLUSIONS

Although propofol tolerance is attenuated in propofol plus remifentanil receiving rabbits under prolonged mechanical ventilation, fatal multi-organ injury occurs resembling human propofol infusion syndrome.

Clinical survey of sedation and analgesia procedures in intensive care units

BACKGROUND

The proper use of sedation and analgesia in the intensive care unit (ICU) minimizes its physical and psychological impact. Otherwise, patients can suffer from recall, nightmares, and depression after discharge. We investigated the sedatives, analgesics, and muscle relaxants used in the ICU.

METHODS

We visited 79 ICUs in 52 training hospitals and noted the use of sedatives, analgesics, and muscle relaxants from July, 2007, to December, 2007, using a 5-item questionnaire with 57 sub-questions. The survey evaluated the ICU system administration of analgesics and muscle relaxants.

RESULTS

Most ICU management is done by the anesthesiology department (55%). Most have resident doctors (63.3%) and an ICU committee (60.8%) in charge of the ICU, as well as a special ICU chart (88.6%) and scoring system (65.8%). Most hospitals have a consulting system (94.9%). The standard ICU analgesics are fentanyl (65.8%), NSAIDs (53.2%), and morphine (48.1%).

CONCLUSIONS

Adequate sedation is difficult to achieve in the ICU, but is important for patient comfort and to reduce ICU stay duration. Awareness of patient status and appropriate drug/protocol use are therefore important.

Analgo-sedation of patients with burns outside the operating room

Following the initial resuscitation of burn patients, the pain experienced may be divided into a 'background' pain and a 'breakthrough' pain associated with painful procedures. While background pain may be treated with intravenous opioids via continuous infusion or patient-controlled analgesia (PCA) and/or less potent oral opioids, breakthrough pain may be treated with a variety of interventions. The aim is to reduce patient anxiety, improve analgesia and ensure immobilization when required. Untreated pain and improper sedation may result in psychological distress such as post-traumatic stress disorder, major depression or delirium. This review summarizes recent developments and current techniques in sedation and analgesia in non-intubated adult burn patients during painful procedures performed outside the operating room (e.g. staple removal, wound-dressing, bathing). Current techniques of sedation and analgesia include different approaches, from a slight increase in background pain therapy (e.g. morphine PCA) to PCA with rapid-onset opioids, to multimodal drug combinations, nitrous oxide, regional blocks, or non-pharmacological approaches such as hypnosis and virtual reality. The most reliable way to administer drugs is intravenously. Fast-acting opioids can be combined with ketamine, propofol or benzodiazepines. Adjuvant drugs such as clonidine or NSAIDs and paracetamol (acetaminophen) have also been used. Patients receiving ketamine will usually maintain spontaneous breathing. This is an important feature in patients who are continuously turned during wound dressing procedures and where analgo-sedation is often performed by practitioners who are not specialists in anaesthesiology. Drugs are given in small boluses or by patient-controlled sedation, which is titrated to effect, according to sedation and pain scales. Patient-controlled infusion with propofol has also been used. However, we must bear in mind that burn patients often show an altered pharmacokinetic and pharmacodynamic response to drugs as a result of altered haemodynamics, protein binding and/or increased extracellular fluid volume, and possible changes in glomerular filtration. Because sedation and analgesia can range from minimal sedation (anxiolysis) to general anaesthesia, sedative and analgesic agents should always be administered by designated trained practitioners and not by the person performing the procedure. At least one individual who is capable of establishing a patent airway and positive pressure ventilation, as well as someone who can call for additional assistance, should always be present whenever analgo-sedation is administered. Oxygen should be routinely delivered during sedation. Blood pressure and continuous ECG monitoring should be carried out whenever possible, even if a patient is undergoing bathing or other procedures that may limit monitoring of vital pulse-oximetry parameters.

Role of active metabolites in the use of opioids

The opioid class of drugs, a large group, is mainly used for the treatment of acute and chronic persistent pain. All are eliminated from the body via metabolism involving principally CYP3A4 and the highly polymorphic CYP2D6, which markedly affects the drug's function, and by conjugation reactions mainly by UGT2B7. In many cases, the resultant metabolites have the same pharmacological activity as the parent opioid; however in many cases, plasma metabolite concentrations are too low to make a meaningful contribution to the overall clinical effects of the parent drug. These metabolites are invariably more water soluble and require renal clearance as an important overall elimination pathway. Such metabolites have the potential to accumulate in the elderly and in those with declining renal function with resultant accumulation to a much greater extent than the parent opioid. The best known example is the accumulation of morphine-6-glucuronide from morphine. Some opioids have active metabolites but at different target sites. These are norpethidine, a neurotoxic agent, and nordextropropoxyphene, a cardiotoxic agent. Clinicians need to be aware that many opioids have active metabolites that will become therapeutically important, for example in cases of altered pathology, drug interactions and genetic polymorphisms of drug-metabolizing enzymes. Thus, dose individualisation and the avoidance of adverse effects of opioids due to the accumulation of active metabolites or lack of formation of active metabolites are important considerations when opioids are used.

[Sedation and analgesia for the brain-injured patient]

Sedation-analgesia occupies an essential place in the specific therapeutic arsenal of the brain-injured patients. The maintenance of the perfusion of the brain, its relaxation and its protection are the fundamental objectives whose finality is to avoid the extension of the lesions and to preserve the neuronal capital. Sedation is instituted when patients are severely agitated or present a deterioration of their state of consciousness (GCS< or =8). Under cover of mechanical ventilation, sedation is the first line treatment of intracranial hypertension, a common pathway of various acute brain diseases of traumatic, vascular or other origin. The use of the combination of hypnotic and opioids is the rule. The combined action of these two classes reinforces and improves their sedative effects. Midazolam is the 2 benzodiazepine of reference. Propofol is more and more frequently added to the combination of hypnotic and opioids. The "propofol infusion syndrome" is a severe limitation to its long term administration in particular among patients presenting a severe septic or inflammatory state. Propofol will be imperatively stopped in the event of metabolic acidosis, rhabdomyolysis, acute renal insufficiency, hyperkaliemia or increase in the blood triglyceride levels. The use of thiopental is restricted to the most severe cases. Its use as a monotherapy at high doses is abandoned to the profit of a co-administration with midazolam or even with the combination of midazolam and propofol. Thiopental overdose is very frequent in the event of associated hypothermia. Etomidate does not have its place apart from induction in fast sequence. The neuro-protective effects of ketamine require to be demonstrated in man before being recommended routinely. Withdrawal of sedation can be responsible for a state of agitation which can be controlled by neuroleptics.

[Agents for sedation and analgesia in the intensive care unit]

Sedation-analgesia for critically ill patients is usually performed with the combination of a sedative agent and an opioid. Midazolam and propofol are the agents most commonly used for sedation in ICU. The quality of the sedation is quite comparable with both agents, but pharmacokinetic properties of propofol allow a more rapid weaning process from mechanical ventilation. However, implementation of algorithms to adjust drug dosages reduces ventilator days and limits the kinetic differences between propofol and midazolam. Among the adverse events associated with propofol, propofol infusion syndrome is a rare but lethal aspect of propofol therapy. Opioids are the mainstay of analgesic therapy. They interact synergistically with hypnotics. Sufentanil, fentanyl and morphine are the most frequently used opioids. Remifentanil is an ultrashort acting opiate that does not appear to accumulate with prolonged use. The advent of remifentanil has allowed the use of analgesia-based sedation.

Remifentanil for tracheal tube tolerance: a case control study

We assessed the minimal remifentanil dosage required for tracheal tube tolerance in awake and spontaneously breathing patients after major abdominal surgery. Forty postoperative patients received remifentanil 0.1 microg.kg(-1).min(-1), which was reduced in steps of 0.025 microg.kg(-1).min(-1) every 30 min. Respiratory response subscore of comfort scale (CSRR), Ramsay sedation scale (RSS), visual analogue scale (VAS), respiratory rate, and minute ventilation were recorded. Spontaneous respiration with no or little response to ventilation (CSRR 2) in co-operative, oriented and tranquil patients (RSS 2) was defined as the main outcome and study endpoint. Thirty-one patients (77.5%) reached a CSRR 2 and RSS 2 with remifentanil 0.025 microg.kg(-1).min(-1) and nine patients (22.5%) required remifentanil 0.05 microg.kg(-1).min(-1). Analgesia was sufficient in all patients (VAS = 30). Remifentanil 0.025-0.05 microg.kg(-1).min(-1) achieves satisfactory tracheal tube tolerance in awake and spontaneously breathing patients.