Anesthetic techniques and early extubation: does it matter?

Analgesic efficacy and risk of low-to-medium dose intrathecal morphine in patients undergoing cardiac surgery: An updated meta-analysis

Background

To evaluate the analgesic efficacy and risk of low-to-medium dose intrathecal morphine (ITM) (i.e., ≤0.5 mg) following cardiac surgery.

Methods

Medline, Cochrane Library, Google scholar and EMBASE databases were searched from inception to February 2022. The primary outcome was pain intensity at postoperative 24 h, while the secondary outcomes included intravenous morphine consumption (IMC), extubation time, hospital/intensive care unit (ICU) length of stay (LOS), and ITM-associated side effects (e.g., respiratory depression). Subgroup analysis was performed on ITM dosage (low: <0.3 mg vs. medium: 0.3–0.5 mg).

Results

Fifteen RCTs involving 683 patients published from 1988 to 2021 were included. Pooled results showed significantly lower postoperative 24-h pain scores [mean difference (MD) = −1.61, 95% confidence interval: −1.98 to −1.24, p < 0.00001; trial sequential analysis: sufficient evidence; certainty of evidence: moderate] in the ITM group compared to the controls. Similar positive findings were noted at 12 (MD = −2.1) and 48 h (MD = −1.88). Use of ITM was also associated with lower IMC at 24 and 48 h (MD: −13.69 and −14.57 mg, respectively; all p < 0.05) and early tracheal extubation (i.e., 48.08 min). No difference was noted in hospital/ICU LOS, and nausea/vomiting in both groups, but patients receiving ITM had higher risk of pruritus (relative risk = 2.88, p = 0.008). There was no subgroup difference in IMC except a lower pain score with 0.3–0.5 mg than <0.3 mg at postoperative 24 h. Respiratory depression events were not noted in the ITM group.

Conclusion

Our results validated the analgesic efficacy of low-to-medium dose ITM for patients receiving cardiac surgery without increasing the risk of respiratory depression.

Immediate extubation after heart transplantation in a child by remifentanil-based ultra-fast anesthesia: A case report

RATIONALE

Ventilator-associated complications comprise important fatal aetiologies during heart transplantation. Ultra-fast anesthesia might provide the most effective measure to prevent this type of complication. Immediate extubation after heart transplantation (IEAHT) has recently been reported in adult patients. However, IEAHT in children is much more challenging due to limitations in anesthesia protocols. Recently, we managed to perform an ultra-fast anesthesia protocol combined with IEAHT during a heart transplant operation in a child, who had an excellent postoperative outcome.

PATIENT CONCERNS

A 13-year-old girl had been diagnosed with dilated cardiomyopathy 5 years before this case, due to intractable dyspnoea and cough. She received multiple medical treatments after diagnosis, with minimal effects. Physical examination findings included a bulge in her left chest and pitting edema over both legs. Moist rales could be heard in the lung. Echocardiography revealed very large heart chambers, with an ejection fraction of 17%.

DIAGNOSIS

The patient was diagnosed with dilated cardiomyopathy and scheduled to undergo an emergent operation for heart transplantation.

INTERVENTIONS

The patient underwent an ultra-fast anesthesia protocol and ultra-fast reversal during heart transplantation. General anesthesia was induced with etomidate, fentanyl, and vecuronium; it was then maintained with remifentanil-based total intravenous anesthesia.

OUTCOMES

Immediately after the end of the operation, the patient was brought to consciousness with stable breathing and haemodynamics. The patient was successfully extubated on the operating table and transferred to the intensive care unit with spontaneous breathing, without postoperative mechanical ventilation. The recovery period was uneventful and the patient was discharged 1 month later without complications.

LESSONS

Our experience, in this case, revealed that IEAHT in children is achievable if the ultra-fast protocol is performed properly and carefully, in order to prevent ventilator-associated complications.

Lower Dose of Sufentanil Does Not Enhance Fast Track Significantly-A Randomized Study

OBJECTIVE

Adjustment in the doses of opioids has been a focus of interest for achieving better fast-track conditions in cardiac anesthesia, but relatively sparse information exists on the potential effect of psychologic and behavioral factors, such as stress, anxiety, and type of personality, on anesthesia requirements and patient turnover in the cardiac recovery unit (CRU); to the authors' knowledge, this particular focus has not been systematically investigated. In this randomized study, the authors tested the hypothesis that low-dose sufentanil, compared with a standard dose, can improve fast-track parameters and the overall quality of recovery. Opioid requirements related to personality type, pain sensitivity, and preoperative stress and anxiety also were assessed.

DESIGN

A randomized, prospective study.

PARTICIPANTS

The study comprised 60 patients scheduled for elective coronary artery bypass grafting with or without aortic valve replacement.

SETTING

A university hospital.

INTERVENTIONS

Patients were randomly assigned to receive either a standard dose (bolus 0.5 µg/kg) or low dose (bolus 0.25 µg/kg) of sufentanil combined with propofol.

MEASUREMENTS AND MAIN RESULTS

The primary outcome variables were ventilation time and eligible time to discharge from the CRU. The secondary objective was to evaluate the relationship between opioid requirements and personality type, pain sensitivity, and preoperative stress and anxiety. The groups were comparable in selected demographics and perioperative parameters. There was no difference between groups in ventilation time (low dose: 191 [163-257] v standard dose: 205 [139-279] min; p = 0.405); eligible CRU discharge time (10.3 ± 5.0 v 10.3 ± 4.2 h; p = 0.978); or administration of postoperative morphine (25 [11-34) v 27 [10-39] g; p = 0.790). There was no difference between groups in total sufentanil administration and various preoperative psychologic and behavioral test levels nor in the time to reach bispectral index <50 during induction, except that personality type A demonstrated a longer induction time of 10 (8-12) minutes versus 6 (4-8) minutes in low-score patients.

CONCLUSION

A lower dose of sufentanil, compared with a standard dose, does not enhance fast-track conditions significantly.

Ultra fast-track extubation in heart transplant surgery patients

Background:

Heart transplant surgeries using cardiopulmonary bypass (CPB) typically requires mechanical ventilation in intensive care units (ICU) in post-operation period. Ultra fast-track extubation (UFE) have been described in patients undergoing various cardiac surgeries.

Aim:

To determine the possibility of ultra-fast-track extubation instead of late extubation in post heart transplant patients.

Materials and Methods:

Patients randomly assigned into two groups; Ultra fast-track extubation (UFE) group was defined by extubation inside operating room right after surgery. Late extubation group was defined by patients who were not extubated in operating room and transferred to post operation cardiac care unit (CCU) to extubate.

Results:

The mean cardiopulmonary bypass time was 136.8 ± 25.7 minutes in ultra-fast extubation and 145.3 ± 29.8 minutes in late extubation patients (P > 0.05). Mechanical ventilation duration (days) was 0 days in ultra-fast and 2.31 ± 1.8 days in late extubation. Length of ICU stay was significantly higher in late extubation group (4.2 ± 1.2 days) than the UFE group (1.72 ± 1.5 days) (P = 0.02). In survival analysis there was no significant difference between ultra-fast and late extubation groups (Log-rank test, P = 0.9).

Conclusions:

Patients undergoing cardiac transplant could be managed with “ultra-fast-track extubation”, without increased morbidity and mortality.

Clinical practice of early extubation after liver transplantation

BACKGROUND

Anesthetic practices such as early tracheal extubation facilitate postoperative recovery. Early extubation after liver transplantation has been adopted by some centers in the recent two decades. No universal clinical guidelines are used and questions remain. This review aimed to address the current status of early extubation after liver transplantation.

DATA SOURCES

A literature search of MEDLINE and ISI Web of Knowledge databases was performed using terms such as liver transplantation, early extubation, immediate tracheal extubation, fast tracking or fast track anesthesia and postoperative tracheal extubation. Additional papers were identified by a manual search of the references in the key articles.

RESULTS

Review of the available literature provided an insight into the definition, evolution, advantages and risks of early extubation, and anesthetic techniques that prompt early extubation in liver transplant patients. Early extubation has proved to be feasible and safe in these patients, but the outcomes are still uncertain.

CONCLUSIONS

Early extubation after liver transplantation is feasible, safe and cost-effective in the majority of patients and has been increasingly accepted as an option for conventional postoperative ventilation. Comprehensive and individualized evaluation of the patient's condition before extubation by an experienced anesthesiologist is the cornerstone of success. Understanding of its effect on the outcome remains incomplete. In the future, additional trials are required to establish universal early extubation guidelines and to determine its benefits for patients and practitioners.

Prolonged ventilation post cardiac surgery--tips and pitfalls of the prediction game

Background

Few available models aim to identify patients at risk of prolonged ventilation after cardiac surgery. We compared prediction models developed in ICU in two adjacent periods of time, when significant changes were observed both in population characteristics and the perioperative management.

Methods

We performed a retrospective review of two cohorts of patients in our department in two subsequent time periods (July 2007 - December 2008, n = 2165; January 2009 - July 2010, n = 2192). The study was approved by the Institutional Ethics Committee and the individual patient consent was not required. Patients were divided with regard to ventilation time of more or less than 48 hours. Preoperative and procedure-related variables for prolonged ventilation were identified and multivariate logistic regression analysis was performed separately for each cohort.

Results

Most recent patients were older, with more co-morbidities, more frequently undergoing off-pump surgery. At the beginning of 2009 we also changed the technique of postoperative ventilation. Percentage of patients with prolonged ventilation decreased from 5.7% to 2.4% (p < 0.0001).Preoperative and procedure-related variables for prolonged ventilation were identified. Prediction models for prolonged ventilation were different for each cohort. Most recent significant predictors were: aortic aneurysm surgery (OR 12.9), emergency surgery (OR 5.3), combined procedures (OR 5.1), valve procedures (OR 3.2), preoperative renal dysfunction (OR 2.9) and preoperative stroke or TIA (OR 2.8).

Conclusions

Prediction models for postoperative ventilation should be regularly updated, particularly when major changes are noted in patients' demographics and surgical or anaesthetic technique.

Sevoflurane Provides Earlier Tracheal Extubation and Assessment of Cognitive Recovery Than Isoflurane in Patients Undergoing Off-Pump Coronary Artery Bypass Surgery

OBJECTIVE

To determine whether sevoflurane, because of its lower blood/gas partition coefficient, compared with isoflurane as the primary anesthetic agent, allows earlier tracheal extubation and assessment of cognitive function after off-pump coronary artery bypass (OPCAB) surgery.

DESIGN

Prospectively, patients were randomly assigned to receive sevoflurane or isoflurane as their primary anesthetic. Intraoperative opioids were limited to 5 microg/kg of fentanyl.

SETTING

Two university hospitals with active cardiac surgery programs.

PARTICIPANTS

One hundred one OPCAB surgery patients who met inclusionary and exclusionary criteria participated with institutional review board approval.

INTERVENTIONS

Mini-Mental Status Examination, Memory Recall Test, and Observer Assessment of Anxiety and Sedation scales were administered preoperatively, postextubation, at 90 minutes, and between 12 to 24 hours. Pain scores were obtained every 15 minutes after extubation for 90 minutes.

MEASUREMENTS AND MAIN RESULTS

Sevoflurane patients were extubated earlier than isoflurane patients (Sevo, 176 +/- 217 minutes and Iso, 257 +/- 279 min, p = 0.02). Although both agents produced similar postanesthetic cognitive profiles, cognitive testing occurred approximately 90 minutes earlier in the sevoflurane group. Verbal rating scale for pain scores >5 were more frequent for sevoflurane than isoflurane patients (p = 0.03).

CONCLUSIONS

Both sevoflurane and isoflurane may be safely used as maintenance agents in OPCAB. Sevoflurane has the advantage of allowing earlier extubation and evaluation of cognitive and neurologic function after OPCAB.

Myocardial protection with volatile anaesthetic agents during coronary artery bypass surgery: a meta-analysis

Previous studies have investigated the role of volatile anaesthetic agents in myocardial protection during coronary artery bypass graft (CABG) surgery, and some have identified beneficial effects. However, these studies have been too small to identify a significant effect on myocardial infarction (MI) or mortality. We undertook a systematic overview and meta-analysis of all randomized trials comparing volatile with non-volatile anaesthesia in CABG surgery. We identified 27 trials that included 2979 patients. There was no significant difference in myocardial ischaemia, MI, intensive care unit length of stay or hospital mortality between the groups (all P>0.05). Post-bypass, patients randomized to receive volatile anaesthetics had 20% higher cardiac indices (P=0.006), significantly lower troponin I serum concentrations (P=0.002) and lesser requirement for inotropic support (P=0.004) compared with those randomized to receive i.v. anaesthetics. Duration of mechanical ventilation was reduced by 2.7 h (P=0.04), and there was a 1 day decrease in hospital length of stay (P<0.001). Some of these outcomes were based on a smaller number of trials because of incomplete data, largely because the individual trials focused on one or more surrogate endpoints. We found some evidence that volatile anaesthetic agents provide myocardial protection in CABG surgery, but larger adequately powered trials with agreed, defined outcomes need to be done to fully assess a possible beneficial effect of volatile anaesthetic agents on the risk of MI and mortality.

Routine Immediate Extubation After Off-Pump Coronary Artery Bypass Surgery: 514 Consecutive Patients

OBJECTIVE

The purpose of this study was to evaluate the feasibility of routine immediate extubation in patients undergoing off-pump coronary artery bypass surgery.

DESIGN

Case series.

SETTING

Private hospital.

PARTICIPANTS

Five hundred forty-eight consecutive patients undergoing off-pump coronary bypass surgery, representing 5 years of a single anesthesiologist's practice, were evaluated for routine immediate extubation. Thirty-four patients were excluded because they were already intubated, in preoperative cardiogenic shock, or converted to on-pump during the procedure.

INTERVENTION

Patients received general anesthesia or general anesthesia plus thoracic epidural analgesia (25%) and underwent off-pump coronary bypass surgery.

MEASUREMENTS AND MAIN RESULTS

All 514 patients who were intended to be immediately extubated were expeditiously extubated in the operating room. The numbers of reintubations, morbidity, and mortality were low.

CONCLUSIONS

Routine immediate extubation of most off-pump coronary artery bypass patients appears feasible and most probably safe.

Time to tracheal extubation after coronary artery surgery with isoflurane, sevoflurane, or target-controlled propofol anesthesia: A prospective, randomized, controlled trial

OBJECTIVES

To determine if anesthesia with sevoflurane or target-controlled propofol reduced the time to tracheal extubation after coronary artery bypass graft surgery compared with isoflurane anesthesia.

DESIGN

A 3-arm (isoflurane, sevoflurane, or propofol), randomized, controlled trial with patients and intensive care staff blinded to the drug allocation.

SETTING

A single, tertiary referral hospital affiliated with the University of Melbourne.

PARTICIPANTS

Three hundred sixty elective coronary artery surgery patients.

INTERVENTIONS

Patients received either isoflurane (control group, 0.5%-2% end-tidal concentration), sevoflurane (1%-4% end-tidal concentration), or target-controlled infusion of propofol (1-8 microg/mL plasma target concentration) as part of a balanced, standardized anesthetic technique including 15 microg/kg of fentanyl.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was time to tracheal extubation. The median time to tracheal extubation for the propofol group was 10.25 hours (interquartile range [IQR] 8.08-12.75), the sevoflurane group 9.17 hours (IQR 6.25-11.25), and the isoflurane group 7.67 hours (IQR 6.25-9.42). Intraoperatively, the propofol group required less vasopressor (p = 0.002) and more vasodilator therapy (nitroglycerin p = 0.01, nitroprusside p = 0.002). There was no difference among the groups in time to intensive care unit discharge.

CONCLUSIONS

The median time to tracheal extubation was significantly longer for the target-controlled propofol group. A significantly greater number in this group required the use of a vasodilator to control intraoperative hypertension.

Factors determining the duration of tracheal intubation in cardiac surgery: a single-centre sequential patient audit

BACKGROUND AND OBJECTIVE

The study was designed to identify those factors associated with early tracheal extubation following cardiac surgery. Previous studies have tended to concentrate on surgery for coronary artery bypass or on other selected cohorts.

METHODS

Sequential cohort analysis of 296 unselected adult cardiac surgery patients was performed over 3 months.

RESULTS

In total, 39% of all patients were extubated within 6 h, 89% within 24 h and 95% within 48 h. Delayed extubation (>6 h after surgery) appeared unrelated to age, gender, body mass index, a previous pattern of angina or myocardial infarction, diabetes, preoperative atrial fibrillation, and preoperative cardiovascular assessment, as well as other factors. Delayed tracheal extubation was associated with poor left ventricular, renal and pulmonary function, a high Euroscore, as well as the type, duration and urgency of surgery. Early extubation (<6 h) was not associated with a reduced length of stay in either the intensive care unit or in hospital compared with patients who were extubated between 6 and 24 h. In these groups, it is presumed that organizational and not clinical factors appear to be responsible for a delay in discharge from intensive care. Patients who were extubated after 24 h had a longer duration of hospital stay and a greater incidence of postoperative complications. Postoperative complications were not adversely affected by early tracheal extubation.

CONCLUSIONS

In an unselected sequential cohort, both patient- and surgery-specific factors may be influential in determining the duration of postoperative ventilation of the lungs following cardiac surgery. In view of the changing nature of the surgical population, regular re-evaluation is useful in reassessing performance.

Injection pain of rocuronium and vecuronium is evoked by direct activation of nociceptive nerve endings

BACKGROUND AND OBJECTIVE

Rocuronium and, to a lesser extent, vecuronium can induce burning sensations associated with withdrawal reactions during administration. Dermal microdialysis in human and electrophysiological recordings of nociceptors in mouse skin were used to elucidate the underlying mechanisms of pain induction.

METHODS

Microdialysis catheters were inserted intradermally into the forearm of 10 volunteers and were perfused with two different concentrations of rocuronium and vecuronium (1 and 10 mg mL(-1)) or a control. Dialysis samples were taken every 15 min and analysed for protein, histamine, tryptase and bradykinin content. Pain intensity was rated on a numerical scale of 0-10. In a parallel design, activation of cutaneous nociceptors was assessed directly in a skin-nerve in vitro preparation of the mouse hind paw. The receptive fields of identified single C-nociceptors (n = 12) were superfused with rocuronium or vecuronium solutions (10 mg mL(-1)) at physiological pH.

RESULTS

In accordance with clinical observations, microdialysis of rocuronium (10 mg mL(-1)) induced sharp burning pain (NRS 4.1 +/- 1.8), whereas vecuronium given in the usual clinical concentration (1 mg mL(-1)) induced only minor pain sensations (NRS 0.6 +/- 1.3). At equimolar concentrations, pain sensation and concomitant mediator release evoked by both drugs were similar. No correlations were found between pain rating and mediator release. In the in vitro preparation, C-fibres showed a consistent excitatory response with rapid onset after stimulation with vecuronium as well as rocuronium (differences not significant).

CONCLUSIONS

The algogenic effect of aminosteroidal neuromuscular blocking drugs can be attributed to a direct activation of C-nociceptors.

Anaesthetic strategies to reduce perioperative blood loss in paediatric surgery

In adults, a number of measures to reduce perioperative blood loss have been established. These techniques serve to reduce patients' exposure to homologous blood. Most adults are concerned with this issue especially since many patients became infected with human immunodeficiency virus (HIV) during the 1980s through exposure to blood components. While blood-saving strategies are widely used in adults, they are mostly neglected in infants. However, it is these young patients with their whole life in front of them who, it could be argued, would benefit especially from any potentially avoidable infection (HIV, hepatitis, etc.) or immunological complications. In infants and small children, these blood-sparing techniques may not be as effective as in adults and technical limitations may prevent their application. However, some of these measures can be used and may serve to prevent or reduce exposure to homologous blood. In the following review, blood-saving techniques established in adults are described and their applicability for paediatric patients discussed.

Effects of propofol on the systolic and diastolic performance of the postischaemic, reperfused myocardium in rabbits

BACKGROUND AND OBJECTIVE

The effect of propofol on myocardial dysfunction during ischaemia and reperfusion is controversial yet important because of its frequent use in cardiac anaesthesia. Although animal studies suggest a free radical-scavenging potential, the cardioprotective properties of propofol have not been demonstrated consistently in vivo. Previous studies focused on systolic function while diastolic function may be a more sensitive marker of ischaemic injury. The main aim was to document the effect of propofol on diastolic function in isolated, blood perfused rabbit hearts subjected to moderate global ischaemia and reperfusion.

METHODS

Propofol 168 micromol L(-1), or the equivalent of its vehicle, Intralipid, was administered to 34 paced parabiotic Langendorff blood-perfused isolated rabbit hearts before and after 30 min of global normothermic ischaemia. Recovery of systolic function was quantified with the maximum rate of rise of left ventricular pressure. Diastolic performance was assessed using the time constant of the decline in left ventricular pressure (tau) and chamber stiffness (VdP/dV at 12 mmHg).

RESULTS

Recovery of systolic function during reperfusion was comparable in the two groups. There was no difference in left ventricular pressure between the two groups at any time during the experiments. Chamber stiffness increased significantly during ischaemia and reperfusion in the control group (from 34 +/- 9 to 54 +/- 8 mmHg during ischaemia, and 43 +/- 5 mmHg after 30 min reperfusion; mean +/-95% confidence interval) but not in the propofol-treated group (29 +/- 5, 36 +/- 8 and 30 +/- 8 at baseline, ischaemia and 30 min reperfusion, respectively).

CONCLUSIONS

Propofol has no protective effect on active relaxation or on systolic function in the present model, but it reduces ischaemic and postischaemic chamber stiffness.

Effects of bupivacaine used with sevoflurane on the rhythm and contractility in the isolated rat heart

BACKGROUND AND OBJECTIVE

The effects of sevoflurane on bupivacaine cardiotoxicity are mainly attributed to systemic effects. The purpose of this study was to investigate the direct myocardial effects of sevoflurane on bupivacaine toxicity.

METHODS

Hearts of 30 Wistar albino rats were isolated and mounted on a Langendorff apparatus perfused by modified Tyrode solution. Experimental groups were: a sevoflurane group (Group S, n = 10)--following baseline and 20 min (Stage 1) recordings, sevoflurane was added in doses of 1.4% (1 MAC) and 2.8% (2 MAC). In the two bupivacaine groups, bupivacaine 5 micromol (Group B5, n = 10) and bupivacaine 10 micromol (Group B10, n = 10) was added to the solution at Stage 1, and sevoflurane was added to the system as in Group S. Haemodynamic variables, i.e. heart rate, PR interval, QRS duration, left ventricular systolic pressure, contractility (+dp/dtmax), relaxation, time to reach peak systolic pressure, change in left ventricular diastolic pressure from baseline, and rate-pressure product were recorded.

RESULTS

In Group S, there was no change in cardiac rhythm. In bupivacaine groups, severe rhythm disturbances occurred and both the PR intervals and QRS complexes were prolonged significantly. All contractility variables deteriorated and the rate-pressure product decreased by 67-90% with the addition of bupivacaine. In all groups, 2 MAC sevoflurane lowered +dp/dtmax further.

CONCLUSIONS

Sevoflurane does not have any untoward effect on bupivacaine-induced cardiotoxicity in clinically relevant doses in the isolated rat heart.

Effect of the neuronal nitric oxide synthase inhibitor 7-nitroindazole on the righting reflex ED50 and minimum alveolar concentration during sevoflurane anaesthesia in rats

BACKGROUND AND OBJECTIVE

The aim was to determine the effect of acute and chronic administration of 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, on the righting reflex ED50 and the minimum alveolar concentration during sevoflurane anaesthesia in rats.

METHODS

7-Nitroindazole was acutely (0, 50 and 100 mg kg(-1)) and chronically (0 and 150 mg kg(-1) day(-1), 4 days) administered to rats. After the preparation, the minimum alveolar concentration and the righting reflex ED50 were measured. The concentration of cGMP in the brain, cerebellum and spinal cord was also measured.

RESULTS

Acute administration reduced the minimum alveolar concentration (50 mg kg(-1), 58.8% (95% CI: 50.3-67.3%) of the baseline value, P < 0.01; 100 mg kg(-1), 55.8 (46.9-64.7), P < 0.01) and the righting reflex ED50 (50 mg kg(-1), 27.2 (17.2-37.2), P < 0.01; 100 mg kg(-1), 14.3 (6.6-22.0), P < 0.01). Chronic administration did not reduce the minimum alveolar concentration; however, it reduced the righting reflex ED50 (65.3 (52.9-77.7), P < 0.01). Overall, the reduction in minimum alveolar concentration in the acute and chronic protocol did not correlate with that of the righting reflex ED50. 7-Nitroindazole (100 mg kg(-1), acute) reduced the cGMP concentration within the cerebellum by 55.4%; however, it did not decrease concentrations in the brain or spinal cord.

CONCLUSIONS

Different mechanisms are responsible for the observed alterations to the minimum alveolar concentration and the righting reflex ED50 following treatment with 7-nitroindazole. The nitric oxide-cGMP pathway might play a less important role in the determination of minimum alveolar concentration than the righting reflex ED50.

Suprascapular nerve block or a piroxicam patch for shoulder tip pain after day case laparoscopic surgery

BACKGROUND AND OBJECTIVE

The reported incidence of shoulder tip pain following laparoscopic surgery varies from 35 to 63%. This study evaluated the analgesic efficacy of either performing a prophylactic suprascapular nerve block with bupivacaine or applying a piroxicam patch to the skin over both shoulders for the relief of shoulder tip pain after laparoscopy.

METHODS

Sixty healthy informed female patients were randomly assigned to one of three groups: (a) a control group (n = 20), no treatment; (b) a suprascapular nerve block group (n = 20) in which a bilateral suprascapular nerve block was performed before induction of anaesthesia with 5 mL 0.5% bupivacaine with epinephrine; and (c) a piroxicam patch group (n = 20) in which a 48 mg piroxicam patch on the skin of each shoulder was applied before induction of anaesthesia. All patients received a total intravenous anaesthesia technique with propofol, fentanyl and vecuronium. Shoulder tip and wound pain were recorded on a visual analogue pain scale at five time intervals for 24 h after surgery.

RESULTS

A total of 80% of patients in the control group, 75% in the suprascapular nerve block group and 45% in the piroxicam patch group complained of shoulder tip pain during the recording period (P < 0.05). The scores for shoulder tip pain in the piroxicam patch group were significantly lower compared with the control group at 3, 6 and 12 h, and compared with the suprascapular nerve block group at 6 and 12 h. The need for analgesics was also significantly lower in the piroxicam patch group compared with the other two groups.

CONCLUSIONS

Prophylactic piroxicam patches are effective and safe for the relief of shoulder tip pain after laparoscopy. Bilateral suprascapular nerve block is not effective in this setting.

Treatment of hiccup during general anaesthesia or sedation: a qualitative systematic review

BACKGROUND AND OBJECTIVE

Acute hiccup is a minor complication that can occur during sedation or general anaesthesia. The disorder can disturb the surgical field, might interfere with lung ventilation or could hamper diagnostic procedures. The objective was to perform a systematic search for interventions aimed at treating hiccup occurring during anaesthesia or sedation.

METHODS

A systematic search for reports describing interventions to treat hiccup in conjunction with anaesthesia was carried out (MEDLINE, EMBASE, Cochrane-Library, manual screening of reference lists and review articles, up to December 2001). Search terms were 'hiccup', 'singultus' or 'hiccough'.

RESULTS

Twenty-six reports involving approximately 581 patients focused on hiccup remedies in the anaesthesia setting. Only one report was substantiated by a randomized controlled trial. This investigated methylphenidate 10 mg intravenously in 51 patients, which did not show a beneficial effect compared with placebo. Hiccup was a self-limiting phenomenon. Case series and case reports focused on various systemically applied drugs in 12 reports, stimulating techniques (e.g. pharyngeal stimulation) in seven, topical applied remedies (e.g. intranasal ice-cold water) in four, and ventilation techniques (e.g. continuous positive pressure ventilation) in two.

CONCLUSIONS

A large variety of interventions have been proposed for the treatment of hiccup during anaesthesia and sedation. However, perioperative treatment is still based on empirical findings and no treatment is 'evidence-based'. Thus, no valid recommendations for the treatment of hiccup can be derived. Uncontrolled observations are inadequate to establish treatment efficacy.

Pharmacokinetics and pharmacodynamics of the new propofol prodrug GPI 15715 in rats

BACKGROUND AND OBJECTIVE

We studied the pharmacokinetics and pharmacodynamics of GPI 15715 (Aquavan injection), a new water-soluble prodrug metabolized to propofol by hydrolysis.

METHODS

Nine adult male Sprague-Dawley rats (398 +/- 31 g) received a bolus dose of 40 mg GPI 15715. The plasma concentrations of GPI 15715 and propofol were determined from arterial blood samples, and the pharmacokinetics of both compounds were investigated using compartment models whereby the elimination from the central compartment of GPI 15715 was used as drug input for the central compartment of propofol. Pharmacodynamics were assessed using the median frequency of the EEG power spectrum.

RESULTS

A maximum propofol concentration of 7.1 +/- 1.7 microg mL(-1) was reached 3.7 +/- 0.2 min after bolus administration. Pharmacokinetics were best described by two-compartment models. GPI 15715 showed a short half-life (2.9 +/- 0.2 and 23.9 +/- 9.9 min), an elimination rate constant of 0.18 +/- 0.01 min(-1) and a central volume of distribution of 0.25 +/- 0.02 L kg(-1). For propofol, the half-life was 1.9 +/- 0.1 and 45 +/- 7 min, the elimination rate constant was 0.15 +/- 0.02 min(-1) and the central volume of distribution was 2.3 +/- 0.6 L kg(-1). The maximum effect on the electroencephalogram (EEG)--EEG suppression for >4 s--occurred 6.5 +/- 1.2 min after bolus administration and baseline values of the EEG median frequency were regained 30 min later. The EEG effect could be described by a sigmoid Emax model including an effect compartment (E0 = 16.9 +/- 7.9 Hz, EC50 = 2.6 +/- 0.8 microg mL(-1), ke0 = 0.35 +/- 0.04 min(-1)).

CONCLUSIONS

Compared with known propofol formulations, propofol from GPI 15715 showed a longer half-life, an increased volume of distribution, a delayed onset, a sustained duration of action and a greater potency with respect to concentration.

High-affinity block of voltage-operated rat IIA neuronal sodium channels by 2,6 di-tert-butylphenol, a propofol analogue

BACKGROUND AND OBJECTIVE

Propofol is a phenol derivative (2,6 di-isopropylphenol) with a unique effect profile including activating effects on GABA(A) and blocking effects on voltage-operated sodium channels. If the substituents in the 2- and the 6-positions are replaced by tert-butyl groups, the resulting phenol derivative, 2,6 di-tert-butylphenol, despite being a close structural propofol analogue, completely lacks GABA(A) receptor effects. The aim of this in vitro study was to investigate the effects of 2,6 di-tert-butylphenol on voltage-operated neuronal sodium channels in order to determine whether and, if so, how these structural changes alter the sodium channel-blocking effect seen with propofol.

METHODS

Whole-cell sodium inward currents through heterologously expressed rat type IIA sodium channels were recorded in the absence and presence of definite concentrations of 2,6 di-tert-butylphenol and propofol.

RESULTS

When applied at concentrations > or = 30 micromol, 2,6 di-tert-butylphenol completely and irreversibly blocked sodium inward currents. The blockade equilibrium time was about 2 min. A partial washout was possible only if the application was stopped before the equilibrium of the blockade was achieved.

CONCLUSIONS

2,6 Di-tert-butylphenol exerts a high-affinity block of neuronal sodium channels. Apparently, the slight structural differences of 2,6 di-tert-butylphenol in comparison with propofol--which account for the lack of GABA(A) receptor effects--enhance its voltage-operated sodium channel-blocking effects. As 2,6 di-tert-butylphenol is much more potent than most sodium channel blockers in clinical use, it might be of interest in the development of local anaesthetics.

Prospective randomised double-blind comparative study of rocuronium and pancuronium in adult patients scheduled for elective 'fast-track' cardiac surgery involving hypothermic cardiopulmonary bypass

The majority of cardiac anaesthetists in the UK use pancuronium for fast-track cardiac surgery. We compared the duration of action of pancuronium and rocuronium in patients undergoing fast-track hypothermic cardiopulmonary bypass and cardiac surgery. We determined whether patients would have had residual neuromuscular blockade at extubation. Twenty patients were randomly allocated to receive either pancuronium 0.1 mg x kg(-1) or rocuronium 1 mg x kg(-1). Neuromuscular function was assessed by acceleromyography; spontaneous recovery was evaluated by the train-of-four ratio measured at the adductor pollicis longus muscle. Median times to recover train-of-four ratio of 0.9 were 3 h 38 min for rocuronium and 7 h 52 min for pancuronium. The median difference in recovery times was 4 h 15 min (95% CI 2 h 30 min to 6 h 20 min; p = 0.0003 by Mann-Whitney test). None of the patients in the rocuronium group and seven of 10 patients in the pancuronium group had their extubations delayed because of residual neuromuscular blockade. Unless fast-track patients have neuromuscular function assessed before extubation, pancuronium should not be used.

Effects of rolipram, pimobendan and zaprinast on ischaemia-induced dysrhythmias and on ventricular cyclic nucleotide content in the anaesthetized rat

BACKGROUND AND OBJECTIVE

This study was designed to compare the haemodynamic, electrophysiological and pharmacodynamic effects of three selective inhibitors of the different isoenzyme forms of phosphodiesterase (PDE) on ischaemia-induced dysrhythmias in the anaesthetized rat. The drugs used were pimobendan, a selective PDE III inhibitor, rolipram, a selective PDE IV inhibitor, and zaprinast, a selective PDE V inhibitor.

METHODS

The coronary artery was occluded 15 min after commencing drug administration, and myocardial ischaemia was maintained for 30 min during which the heart rate and mean arterial pressure were recorded. cAMP and cGMP were determined by radioimmunoassay.

RESULTS

Pretreatment with rolipram decreased the duration of ventricular tachycardia without any change in the incidences of dysrhythmias or the mortality rate. This drug did not modify ventricular content of adenosine 3',5'-cyclic monophosphate (cAMP) or guanosine 3',5'-cyclic monophosphate (cGMP). Pimobendan (1 mg kg(-1) + 0.1 mg kg(-1) min) decreased the duration of ventricular tachycardia. This dose of pimobendan and zaprinast (1 mg kg(-1) + 0.1 mg kg(-1) min(-1)) increased the incidence rate of ventricular fibrillation following coronary artery ligation and the mortality rate. Moreover, both drugs increased cGMP in the ventricle.

CONCLUSIONS

The results demonstrated that pimobendan and zaprinast increased the incidence of dysrhythmias and the mortality rate, which was accompanied by an increase in the ventricular content of cGMP. Rolipram decreased the duration of ventricular tachycardia without a change in the cyclic nucleotide content or in the mortality rate.

Is very early extubation after lung transplantation feasible?

OBJECTIVE

To evaluate donor graft function, intraoperative blood consumption, and oxygenation and hemodynamic stability in patients undergoing lung transplantation.

DESIGN

Prospective pilot study.

SETTING

University hospital.

PARTICIPANTS

Forty-three patients undergoing lung transplantation from January 1999 to June 2001.

INTERVENTIONS

Hemodynamic monitoring, early extubation, and noninvasive ventilation criteria.

MEASUREMENTS AND MAIN RESULTS

The 31 nonearly extubated patients showed a lower PaO(2)/fraction of inspired oxygen (F(I)O(2)), a higher mean pulmonary arterial pressure, extravascular lung-water index (EVLWI) and vasoactive drug support (norepinephrine), and more blood products consumption than 12 early extubated patients at the end of surgery. Seven of 12 early extubated patients did not show any signs of respiratory failure after tracheal extubation; they were alert and able to perform deep breathing exercise and coughing. In the other 5 patients, hypoxemia, hypercapnia, and an increase of respiratory rate >30 breaths/min were observed. The intermittent application of noninvasive pressure ventilation by face mask avoided endotracheal intubation.

CONCLUSION

The use of a short-acting anesthetic drug, appropriate intraoperative extubation criteria, epidural analgesia, and postoperative noninvasive ventilation make early extubation of lung-transplanted patients possible and effective.

Do intraoperative variables have an effect on the timing of tracheal extubation after coronary artery bypass graft surgery?

OBJECTIVE

The purpose of this study was to investigate whether any intraoperative variable had a significant effect on extubation time after coronary artery bypass graft surgery.

DESIGN

Study design was a retrospective study.

SETTING

Study took place in 1 cardiac center in the United Kingdom that had 1000 cases per year.

SUBJECTS

Eighty-nine patients had coronary artery bypass graft surgery in the first 6 months of 1998 performed by one consultant cardiac surgeon.

OUTCOME MEASURES

Study measures included intraoperative variables (number of vessels grafted, time on cardiopulmonary bypass [CPB], length of the operation, use of internal mammary artery) and extubation time.

RESULTS

Mean extubation time was 4.97 hours. On analysis via linear regression no intraoperative variables were found to be statistically significant (P = .05) to extubation time.

CONCLUSION

This study identified that early extubation can be achieved safely. Although no variable was found to have a significant effect on extubation time, the relationship between CPB and extubation may have been attributed to the low mean CPB time within the study (49.1 minutes). The relationship between cardiac status, ischemia, and the timing of extubation does warrant additional exploration.