Dose-response effect of serum butyrylcholinesterase activity after clinical doses of pancuronium

INTRODUCTION

Low-dose pancuronium is known to affect serum cholinesterase activity (BChE); however, the dose-response effect of clinical doses of pancuronium on BChE has not been investigated.

METHODS

Thirteen ASA I-II patients scheduled for elective surgery requiring muscle relaxation were enrolled in this study. All patients had normal BChE before surgery. Incremental doses of pancuronium (10, 20, 50, and 100 microg/kg) were injected in accordance with surgical needs every 45 min. BChE was measured 3 min after injection by an automatic colorimetric method.

RESULTS

BChE decreased significantly in all except one patient in comparison to the baseline (P < 0.05). However all values remained within normal clinical range. A dose of 100 microg/kg yielded significant decrease in comparison to 10 microg/kg but not to other dosages. Linear regression was not significant for the dose-response relationship (P = 0.05).

CONCLUSION

After clinical incremental doses of pancuronium, BChE remained within clinical range.

Comparison of two induction regimens using or not using muscle relaxant: impact on postoperative upper airway discomfort

BACKGROUND

Muscle relaxants facilitate tracheal intubation, but they are often not used for short peripheral surgical procedures. The consequences of this practice on the upper airway are still a matter of controversy. We therefore compared the incidence of post-intubation symptoms in a randomized study comparing patients intubated with or without the use of a muscle relaxant.

METHODS

A total of 300 adult patients requiring tracheal intubation for scheduled peripheral surgery were randomly assigned in a double-blind study to an anaesthetic protocol that either included or did not include a muscle relaxant (rocuronium). The primary end-point was the rate of post-intubation symptoms 2 and 24 h after extubation. The secondary end-points were the intubation conditions score (Copenhagen Consensus Conference), the rate of difficult intubations (Intubation Difficulty Scale), and the incidence of adverse haemodynamic events.

RESULTS

Post-intubation symptoms were more frequent in patients intubated without the use of a muscle relaxant, whether 2 h (57% vs 43% of patients; P < 0.05) or 24 h (38% vs 26% of patients; P < 0.05) after extubation. Intubation conditions were better when the muscle relaxant was used. In patients intubated without a muscle relaxant, difficult intubation was more common (12% vs 1%; P < 0.05), as were arterial hypotension or bradycardia requiring treatment (12% vs 3% of patients; P < 0.05).

CONCLUSIONS

The use of a muscle relaxant for tracheal intubation diminishes the incidence of adverse postoperative upper airway symptoms, results in better tracheal intubation conditions, and reduces the rate of adverse haemodynamic events.

Participation of French general practitioners in end-of-life decisions for their hospitalised patients

BACKGROUND AND OBJECTIVE

Assuming the hypothesis that the general practitioner (GP) can and should be a key player in making end-of-life decisions for hospitalised patients, perceptions of GPs' role assigned to them by hospital doctors in making withdrawal decisions for such patients were surveyed.

DESIGN

Questionnaire survey.

SETTING

Urban (districts located near Paris) and rural (southern France) areas.

PARTICIPANTS

GPs.

RESULTS

The response rate was 32.2% (161/500), and it was observed that 70.8% of respondents believed that their participation in withdrawal decisions for their hospitalised patients was essential, whereas 42.1% believed that the hospital doctors were sufficiently skilled to make withdrawal decisions without input from the GPs. Most respondents were found to believe that they had the necessary skills (91.9%) and enough time (87.6%) to participate in withdrawal decisions. The last case of treatment withdrawal in hospital for one of their patients was described by 40% (65/161) of respondents, of whom only 40.0% (26/65) believed that they had participated actively in the decision process. The major factors in the multivariate analysis were the GP's strong belief that his or her participation was essential (p = 0.01), information on admission of the patient given to the GP by the hospital department (p = 0.007), rural practice (p = 0.03), visit to the patient dying in hospital (p = 0.02) and a request by the family to be kept informed about the patient (p = 0.003).

CONCLUSION

Strong interest was evinced among GPs regarding end-of-life issues, as well as considerable experience of patients dying at home. As GPs are more closely corrected to patients' families, they may be a good choice for third-party intervention in making end-of-life decisions for hospitalised patients.

The effect of fentanyl and remifentanil, with or without ketoprofen, on pain after thyroid surgery

BACKGROUND AND OBJECTIVES

This study was designed to quantify the additional postoperative analgesic efficacy of a single dose of ketoprofen in patients undergoing thyroid surgery using two different intraoperative analgesic regimens.

METHODS

One hundred and twenty patients were randomly assigned to one of four groups: intraoperative fentanyl or remifentanil with or without ketoprofen (n = 30 for each group). Intravenous ketoprofen (1.5 mg kg-1) or saline was administered 45 min before the end of surgery. Pain scores, opioid demand and length of stay in the postanaesthesia care unit were assessed in a blinded manner.

RESULTS

Patients receiving intraoperative fentanyl with saline had significantly lower visual analogue scale pain scores in the postanaesthesia care unit compared with those receiving intraoperative remifentanil with saline (55 +/- 10 mm vs. 80 +/- 18 mm, P < 0.05) and they stayed shorter in the postanaesthesia care unit (86 +/- 24 min vs. 126 +/- 37 min). In conjunction with intraoperative fentanyl, ketoprofen significantly decreased postoperative pain scores (40 +/- 10 mm, P < 0.05 compared with fentanyl alone) and opioid demand (4 of 30 patients vs. 14 of 30 patients compared with fentanyl alone, P < 0.05). Patients receiving intraoperative remifentanil had no additional analgesic benefit with ketoprofen.

CONCLUSION

After thyroid surgery, patients receiving intraoperative fentanyl had lower pain scores and needed less rescue analgesia compared with patients receiving intraoperative remifentanil. The adjunction of ketoprofen further improved analgesia in patients who received intraoperative fentanyl only.

Postoperative pain scores and analgesic requirements after thyroid surgery: comparison of three intraoperative opioid regimens

PURPOSE

This study was designed to compare the effect on postoperative pain, opioid consumption and the length of stay in postoperative care unit (PACU) after three different intraoperative analgesic regimens in thyroid surgery.

METHODS

Seventy five patients were enrolled into the study and assigned to one of three groups, fentanyl, sufentanil or remifentanil (n=25 for each group). Before the end of surgery, paracetamol 1 gr and nefopam 20 mg was also administered in all patients. Pain scores, opioid demand and the length of stay in PACU were assessed in a blind manner.

RESULTS

Post operative pain scores were significantly lower in the fentanyl and sufentanil groups compared to remifentanil group (55 +/- 15, and 60 +/- 10 versus 78+/- 12, P < 0.05). Patients in the remifentanil group stayed longer in the PACU 108+/- 37 min versus 78+/-31 and 73 +/- 25 min, (P< 0.05).

CONCLUSION

After remifentanil based analgesia, anticipation of postoperative pain with opioid analgesic appears mandatory even for surgery rated as being moderately painful, otherwise longer opioid titration due to higher pain scores might delay discharge time.

Does repetition of post-tetanic count every 3 min during profound relaxation affect accelerographic recovery of atracurium blockade?

BACKGROUND

Post-tetanic count is a valuable method to assess profound neuromuscular blockade. However, subsequent responses to repetitive stimulation might be altered due to post tetanic facilitation (PTF). To avoid PTF, it has been advocated to limit the interval of stimulation from 6 to 10 min. The impact of PTF on 90% recovery of the TOF ratio has not been evaluated. Therefore, we assessed the effect of repetitive PTC stimulation on atracurium blockade with the primary outcome being the time to reach 90% TOF recovery in comparison to classical TOF stimulation.

METHODS

After informed consent 20 patients ASA I-II, scheduled for peripheral surgery under general anaesthesia and requiring tracheal intubation were enrolled into the study. Anaesthesia was induced with fentanyl, propofol, and atracurium, 0.5 mg kg(-1). Neuromuscular characteristics were assessed at the adductor pollicis by a TOF Watch((R)) accelerometer (Organon, Teknika, Holland) on each arm. After onset of maximum neuromuscular blockade, repetitive PTC every 3 min on one arm and repetitive TOF stimulation every 15 s on the opposite arm was performed. The following parameters were recorded: onset of maximum blockade, mean time of PTC stimulation, the maximum number of responses to PTC, time of the first and second TOF responses, and recovery profile until 90% TOF ratio.

RESULTS

Time to reach 90% TOF recovery was similar on both arms (48 +/- 9 min), with a difference of 16 +/- 38 s between the arms (P = 0.64). The first and second responses of the TOF on the PTC-stimulated arm appeared at 29 +/- 8 min and 33 +/- 7 min, respectively. On the other arm the responses appeared at 30 +/- 8 min and 35 +/- 8 min, respectively (P < 0.05).

CONCLUSION

Repetitive PTC stimulation every 3 min hastened the first and second responses of the TOF stimulation but we could not detect a significant difference in the 90% recovery of TOF ratio during atracurium blockade.

Interaction between mivacurium and pancuronium: impact of the order of administration

INTRODUCTION

Potentiation of mivacurium by low-dose pancuronium is mostly due to an inhibition of plasma butyryl cholinesterase (BchE) resulting in a decreased rate of hydrolysis of mivacurium. Nevertheless, an interaction at the receptor site could not be ruled out. By changing the order of the muscle relaxant injections, we may lessen the pharmacokinetic interaction and assess the impact at the acetylcholine receptor level.

METHODS

Twenty patients scheduled for general anesthesia with propofol and fentanyl, and isoflurane were randomized into two groups receiving, mivacurium 100 microg kg-1 followed by pancuronium 15 microg kg-1 (group 1) or pancuronium 15 microg kg-1 followed by mivacurium 100 microg kg-1 (group 2). BchE before and after injection of each relaxant was measured. Neuromuscular block was assessed with a force transducer at the adductor pollicis measuring the elicited twitch to ulnar nerve stimulation.

RESULTS

The neuromuscular block was greater when pancuronium was administered before mivacurium (100% versus 96+/-3%; P<0.05). Times to recovery of the elicited twitch response to 25% and 75% of control value were increased by 100% (P<0.05). After pancuronium, decreases in BchE of 11% and 14% in groups 1 and 2 were observed, respectively.

CONCLUSION

Interaction between mivacurium and low dose pancuronium is significant only when mivacurium is injected after pancuronium.

Decreased VEGF concentration in lung tissue and vascular injury during ARDS

Endothelial injury is an important prognostic factor in acute respiratory distress syndrome (ARDS). Decreased production of vascular endothelial growth factor (VEGF) in ARDS may favour vascular lesions, since VEGF promotes endothelial survival by inhibiting apoptosis. This study sought to document low VEGF levels in lung tissue from ARDS patients, to determine whether the cause was injury to alveolar type II cells (the main pulmonary source of VEGF) and to evaluate the vascular consequences. Lung specimens were obtained by open biopsy or autopsy from 29 patients with severe ARDS (two survivors) and five controls. As compared with controls, homogenates of lung tissue from ARDS patients contained less VEGF (median (interquartile range) ARDS 8.2 (4.7-12.2) versus controls 28.4 (9.9-47.1) ng x g(-1) protein). Increased immunostaining with surfactant protein B was seen in ARDS lungs. Extensive cellular apoptosis (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelling staining), including endothelial and alveolar type II cells, was demonstrated, and vascular bed density (CD31 immunostaining) decreased in ARDS lungs as compared with controls. VEGF levels were negatively correlated to apoptotic endothelial cell counts. In conclusion, decreased vascular endothelial growth factor levels in lung tissue may participate in the decrease in lung perfusion in acute respiratory distress syndrome.

Thrombocytosis after trauma: incidence, aetiology, and clinical significance

BACKGROUND

Our aim was to assess the occurrence, aetiology, and clinical significance of a platelet count greater than 600 x 10(3)/mm(3) in trauma patients.

METHODS

All trauma patients admitted to the intensive care unit (ICU) during a 13-month period were prospectively studied. Platelet counts were performed daily. We recorded the patient's age, sex, nature of trauma, severity of illness scores, episodes of infections in the ICU, acute lung injury, bleeding, and thromboembolic events. Patients with thrombocytosis were also followed during their hospital stay and 1 month after hospital discharge.

RESULTS

A total of 176 patients were included. Thrombocytosis developed in 36 patients (20.4%) at a mean (sd) time of 14.0 (4.0) days and the platelet count normalized 35.0 (13.0) days after admission to the ICU. All patients with thrombocytosis had one or more possible predisposing conditions before the occurrence of thrombocytosis: nosocomial infection occurred in 30 patients (83%), acute lung injury in 17 (47%), bleeding in 27 (75%), and administration of cathecholamines in 24 (67%). Three venous thromboembolic complications occurred in the ICU (1.7%) and one during follow-up. Only one patient presented thrombocytosis at the time of diagnosis. Despite the fact that patients with thrombocytosis had a greater severity of illness, the ICU mortality was comparable among patients with and without thrombocytosis (8 vs 14%, P=0.34).

CONCLUSIONS

Reactive thrombocytosis is a common finding after severe trauma and was found to be associated with a better survival than predicted by severity of illness score. Unless additional risk factors are present, reactive thrombocytosis is not associated with an increased risk of thromboembolic events.

Effect of excessive environmental heat on core temperature in critically ill patients. An observational study during the 2003 European heat wave

BACKGROUND

The primary goal of this study was to investigate the relation between the core temperature of critically ill patients and hot ambient temperatures during a heat wave. The second goal was to evaluate the impact of such a heat wave on the number of microbiological tests ordered.

METHODS

During a heat wave, from August 3 to 22, 2003, we conducted an observational study in the surgical intensive care unit (ICU) of a French hospital that had no air-conditioning at the time. The core temperature of 18 critically ill patients and 36 health-care workers was measured with a non-contact, infrared tympanic membrane thermometer. The association between the core body temperature in infected and non-infected critically ill patients and the staff members, and the ambient temperature in the ICU was analysed using linear regression. The number of microbiological tests ordered was also recorded and compared with the same period in the previous year.

RESULTS

The equation of the regression line for infected critically ill patients was: core temperature=33.5+0.16 x ambient temperature (R(2)=0.53; P<0.0001). The regression line was steeper than that for the non-infected patients (0.077; P<0.0001). The slopes of the regression lines for non-infected and control patients were similar (P=0.20). More blood cultures were carried out during the heat wave than at the same period during the year 2002 (4.80 blood cultures per 1000 patient-days vs 2.47 per 1000 patient-days; P=0.0006).

CONCLUSION

During a sustained high ambient temperature, hyperthermia can occur in critically ill infected patients and to a lesser extent in non-infected patients and health-care workers. The number of blood cultures requested rises substantially, leading to increased costs. Installation of air-conditioning is therefore recommended.

Comparison of the neuromuscular blocking effect of cisatracurium and atracurium on the larynx and the adductor pollicis

BACKGROUND

Cisatracurium unlike atracurium is devoid of histamine-induced cardiovascular effects and this alone would be the greatest advantage in replacing atracurium for the facilitation of tracheal intubation. On the other hand, 2 ED(95) doses of cisatracurium (100 micro g/kg) do not yield satisfactory intubating conditions such as those seen with equipotent doses of atracurium and therefore the recommended intubating dose of cisatracurium is 3 ED(95). To understand this discrepancy better, we evaluated the potency and onset of atracurium and cisatracurium directly at the larynx adductors in humans.

METHODS

The study was conducted in 54 patients (ASA class I or II) undergoing peripheral surgery requiring general anesthesia. Cisatracurium 25-150 micro g/kg or atracurium 120-500 micro g/kg intravenous (i.v.) boluses doses were administered during anesthesia with propofol, nitrous oxide, oxygen and fentanyl. Neuromuscular block was measured by electromyography (single twitch stimulation every 10 s) at the larynx and the adductor pollicis. The dose-response effect measured at both muscles included maximum neuromuscular blockade achieved (Emax), the time to maximum depression of twitch height (onset) and time to spontaneous recovery of the twitch height to 25%, 75% and 90% (T25, T75, T90) of control value.

RESULT

The onset at the larynx was of 196 +/- 28 s after the 100 micro g/kg cisatracurium dose compared with 140 +/- 14 s after the 500 micro g/kg atracurium dose (P < 0.05). Emax at the larynx was 92 +/- 1% and 98 +/- 1% after 100 micro g/kg cisatracurium and 500 micro g/kg atracurium, respectively (P < 0.05). The time to onset of maximum suppression Emax = 100 +/- 0% after a 150 micro g/kg cisatracurium dose was 148 +/- 29 s. At the larynx, the ED(50) was 25 micro g/kg for cisatracurium and 180 micro g/kg for atracurium and the ED(95) was 87 micro g/kg for cisatracurium compared with 400 micro g/kg for atracurium.

CONCLUSION

The slow onset time at the laryngeal muscles after cisatracurium can be explained by the higher potency as compared with atracurium.

Increased carbon dioxide absorption during retroperitoneal laparoscopy

BACKGROUND

Retroperitoneoscopy for renal surgery is now a common procedure. We compared carbon dioxide absorption in patients undergoing retroperitoneoscopy for adrenal or renal surgery with that of patients undergoing laparoscopic cholecystectomy.

METHODS

We measured carbon dioxide elimination with a metabolic monitor in 30 anaesthetized patients with controlled ventilation, undergoing retroperitoneoscopy (n=10), laparoscopy (n=10) or orthopaedic surgery (n=10).

RESULTS

Carbon dioxide production increased by 38, 46 and 63% at 30, 60 and 90 min after insufflation (P<0.01) in patients having retroperitoneoscopy. Carbon dioxide production (mean (SD)) increased from 92 (21) to 150 (43) ml x min(-1) m(-2) 60-90 min after insufflation and remained increased after the end of insufflation. During laparoscopy, V(.)(CO(2)) increased less (by 15%) (P<0.05 compared with retroperitoneoscopy) and remained steady throughout the procedure.

CONCLUSION

Retroperitoneal carbon dioxide insufflation causes more carbon dioxide absorption than intraperitoneal insufflation, and controlled ventilation should be increased if hypercapnia should be avoided.

Comparison between the Datex-Ohmeda M-NMT module and a force-displacement transducer for monitoring neuromuscular blockade

BACKGROUND AND OBJECTIVE

The Datex-Ohmeda neuromuscular transmission module (M-NMT) is a new monitor that is part of the AS/3 anaesthesia monitor. It incorporates a mechanosensor, which is a piezoelectric polymer attached to the hand. The module was compared with a force transducer in 30 patients requiring neuromuscular blockade.

METHODS

Anaesthesia was induced with fentanyl and propofol, and tracheal intubation was performed without muscle relaxants. Neuromuscular blockade was assessed by the test module on one arm and the force transducer on the other arm. When the response to train-of-four stimulation had been stable in both arms for 3 min, rocuronium 0.2 mg kg(-1) was injected intravenously. During recovery from blockade, the train-of-four ratio was measured in 15 patients, and the ratio of response to double-burst stimulation in the other 15 patients. Data analysis was by difference plots.

RESULTS

Both devices had acceptable coefficients of repeatability. The M-NMT module was biased by + 1.3% (upper limit of agreement 14.2%, lower limit -12.9%) for the recovery of the train-of-four ratio, and by + 1.09% (17%, -16%) for the recovery of double-burst stimulation ratio.

CONCLUSIONS

The Datex-Ohmeda M-NMT gives measurements that are repeatable and gives good enough correspondence with a force transducer that it can be used clinically to assess recovery of neuromuscular blockade, but the limits of agreement rule out research applications.

Effect of metoclopramide on mivacurium-induced neuromuscular block

In order to investigate the effect of metoclopramide on the duration of action of mivacurium, 45 patients were randomized into three groups. Group M10 (n = 15) and M20 (n = 15) received 10 and 20 mg of metoclopramide i.v., respectively, and group S (n = 15) received saline 2 min before induction of anesthesia with fentanyl, thiopental and mivacurium. Plasma cholinesterase activity (pCHE) was measured before induction of anesthesia and 2 min after injection of metoclopramide and saline. Neuromuscular block was monitored by a force transducer using train of four nerve stimulation. Anesthesia was maintained with isoflurane and N2O. Time to recovery of a twitch height of 90% was significantly prolonged in group M10 and M20 (44 +/- 15 and 57 +/- 10 min) as compared to group S, 32 +/- 9 min, P < 0.05). A slight but significant decrease in pCHE was observed in group M20. Because of the risk of prolonged duration of action of mivacurium, neuromuscular blockade should always be monitored whenever metoclopramide is given before injection of mivacurium.

Intracuff pressure and tracheal morbidity: influence of filling with saline during nitrous oxide anesthesia

BACKGROUND

Diffusion of nitrous oxide into the cuff of the endotracheal tube results in an increase in cuff pressure. Excessive endotracheal tube cuff pressure may impair tracheal mucosal perfusion and cause tracheal damage and sore throat. Filling the cuff of the endotracheal tube with saline instead of air prevents the increase in cuff pressure due to nitrous oxide diffusion. This method was used to test whether tracheal morbidity is related to excess in tracheal cuff pressure during balanced anesthesia.

METHODS

Fifty patients with American Society of Anesthesiologists physical status I or II were randomly allocated to two groups with endotracheal tube cuffs initially inflated to 20-30 cm H(2)O with either air (group A) or saline (group S). Anesthesia was maintained with isoflurane and nitrous oxide. At the time of extubation, a fiberoptic examination of the trachea was performed by an independent observer, and abnormalities of tracheal mucosa at the level of the cuff contact area were scored. Patients assessed their symptoms (sore throat, dysphagia, and hoarseness) at the time of discharge from the postanesthesia care unit and 24 h after extubation on a 101-point numerical rating scale.

RESULTS

Cuff pressure increased gradually during anesthesia in group A but remained stable in group S. The incidence of sore throat was greater in group A than in group S in the postanesthesia care unit (76 vs. 20%) and 24 h after extubation (42 vs. 12%; P < 0.05). Tracheal lesions at time of extubation were seen in all patients of group A and in eight patients (32%) of group S (P < 0.05).

CONCLUSION

Excess in endotracheal tube cuff pressure during balanced anesthesia due to nitrous oxide diffusion into this closed gas space causes sore throat that is related to tracheal mucosal erosion.

[Extracorporeal circulation with danaparoid sodium for valve replacement in thrombocytopenia induced by type II heparin]

A type II heparin-induced thrombocytopenia (HIT) was diagnosed in a 64-year-old woman at day 20 of intravenous unfractionated heparin (UFH) therapy, given after myocardial infarction treated by angioplasty and intracoronary stent. The infarction was complicated by a mitral insufficiency that led to a mitral valve replacement. Cardiopulmonary bypass was successfully performed with sodium danaparoid (Orgaran), as an alternative to UFH, without thrombotic or haemorrhagic complications and the follow-up was uneventful.

Accuracy of pulse oximetry in the intensive care unit

OBJECTIVE

Pulse oximetry (SpO2) is a standard monitoring device in intensive care units (ICUs), currently used to guide therapeutic interventions. Few studies have evaluated the accuracy of SpO2 in critically ill patients. Our objective was to compare pulse oximetry with arterial oxygen saturation (SaO2) in such patients, and to examine the effect of several factors on this relationship.

DESIGN

Observational prospective study.

SETTING

A 26-bed medical ICU in a university hospital.

PATIENTS

One hundred two consecutive patients admitted to the ICU in whom one or serial arterial blood gas analyses (ABGs) were performed and a reliable pulse oximeter signal was present.

INTERVENTIONS

For each ABG, we collected SaO2, SpO2, the type of pulse oximeter, the mode of ventilation and requirement for vasoactive drugs.

MEASUREMENTS AND RESULTS

Three hundred twenty-three data points were collected. The mean difference between SpO2 and SaO2 was -0.02% and standard deviation of the differences was 2.1%. From one sample to another, the fluctuations in SpO2 to arterial saturation difference indicated that SaO2 could not be reliably predicted from SpO2 after a single ABG. Subgroup analysis showed that the accuracy of SpO2 appeared to be influenced by the type of oximeter, the presence of hypoxemia and the requirement for vasoactive drugs. Finally, high SpO2 thresholds were necessary to detect significant hypoxemia with good sensitivity.

CONCLUSION

Large SpO2 to SaO2 differences may occur in critically ill patients with poor reproducibility of SpO2. A SpO2 above 94% appears necessary to ensure a SaO2 of 90%.

Effects of portal triad clamping on haemodynamic conditions during laparoscopic liver resection

To evaluate the haemodynamic effects of portal triad clamping (PTC) during laparoscopic liver resection, 10 patients without cardiac disease were studied by invasive monitoring including a pulmonary artery catheter and were compared with a control group of 10 patients undergoing liver resection by laparotomy. During laparoscopic surgery, intra-abdominal pressure was kept below 14 mm Hg and minute ventilation was adjusted to prevent hypercapnia. Measurements were made before PTC (T1), 5 min after PTC (T2) and 5 min after clamp release (T3). During clamping with pneumoperitoneum, mean arterial pressure (MAP) remained stable (+2%; not significant), systemic vascular resistance (SVR) increased by 37% (P<0.01, T2 vs T1) and cardiac index (CI) decreased by 19% (P<0.01, T2 vs T1). During laparotomy and clamping, MAP increased by 18% (P<0.01, T2 vs T1), SVR increased by 36% (P<0.01, T2 vs T1) and CI decreased by 9% (not significant). We were unable to demonstrate a difference in haemodynamic changes during clamping with pneumoperitoneum vs the open surgical technique, but in a small number of patients this lack of difference could have been a result of inadequate statistical power. The haemodynamic changes that we found were well tolerated in these patients, who had normal cardiac function.

Pulmonary scintigraphy for diagnosis of aspiration during intravenous propofol anaesthesia for colonoscopy

A specific technique for detection of pulmonary aspiration during the perioperative period is lacking. In this study, we developed a scintigraphic method for its diagnosis. Technetium 99m sulphur colloid was given orally 2 h before an i.v. infusion of propofol in patients undergoing elective colonoscopy. During the procedure, patients were spontaneously breathing 100% oxygen via a face mask. After recovery from anaesthesia, patients had a chest scinti-scan. As a control group, 10 healthy men were studied. The lung scan was considered positive if any tracer activity greater than background level was detected in the lung field. Among 96 patients studied, three patients had a positive chest scinti-scan. One of the three patients developed pneumonia while the other two remained asymptomatic. In none of the control asymptomatic group was tracer detected in the chest. We suggest that this technique is specific and can be used as a tool to assess the risk of pulmonary aspiration during different anaesthetic procedures.

The pharmacokinetics of cisatracurium in patients with acute respiratory distress syndrome

Continuous neuromuscular blockade is often necessary in patients being treated for acute respiratory distress syndrome (ARDS) to optimize oxygenation. In this study, neuromuscular blockade (no response to two responses at the train-of-four stimulation at the orbicularis oculi muscle) was achieved in six patients with ARDS by a continuous infusion of cisatracurium. The plasma concentration of cisatracurium during the infusion averaged 1.00 (0.25-1.45) microg/mL, expressed as median (range). The clearance and half-life were 6.5 (3.3-7.6) mL. min(-1). kg(-1) and 25 (16-48) min, respectively. The laudanosine plasma concentrations were 0.70 (0.12-1.20) microg/mL. The pharmacokinetic variables of cisatracurium are similar to those of patients without organ failure undergoing elective surgery. Plasma laudanosine levels always remained well less that those associated with seizure activity in animal models. Long-term infusion of cisatracurium was not associated with any side effects. Cisatracurium is a suitable muscle relaxant when deep and continuous levels of muscle relaxation are required in patients treated for ARDS.

IMPLICATIONS

We studied the pharmacokinetics of cisatracurium in six patients treated for respiratory distress syndrome by continuous muscle relaxation. A deep degree of neuromuscular blockade corresponding to abolition of two responses at the orbicularis oculi to train-of-four stimulation was obtained in all patients. The pharmacokinetic variables observed in these severely ill patients were similar to those of anesthetized patients. No accumulation of laudanosine was seen. Cisatracurium appears to be suitable when continuous muscle relaxation is required in critically ill patients.

Effects of propofol on H-reflex in humans

BACKGROUND

Depression of spinal cord motoneuron excitability has been proposed to contribute to surgical immobility. The H-reflex, which measures alpha-motoneuron excitability, is depressed by volatile anesthetics, whereas the action of propofol is unknown. The objective of this study was to determine the effects of propofol anesthesia on the H-reflex.

METHODS

In 13 patients (group 1), H-reflex was measured before (T0), 3 min after (T1), and 10 min after (T2) a 2-mg/kg bolus dose of propofol, followed by an infusion of 10 mg x kg(-1) x h(-1). Ten patients (group 2) were studied when propofol was given via a programmable pump set to a propofol blood concentration of 6 microg/ml, and 10 patients (group 3) were studied with the pump set to 9 microg/ml. Latencies and amplitudes of H-reflexes (H0, H1, H2) and M-responses (M0, M1, M2) of the soleus muscle were recorded, and H/M ratios (H0/M0, H1/M1, H2/M2) were calculated.

RESULTS

In group 1, H-reflex amplitudes and the H/M ratio were diminished after induction with propofol (H0 vs. H1, P = 0.033; H0/M0 vs. H1/M1, P = 0.042). After 10 min of propofol infusion, the H2/M2 ratio was still decreased versus H0/M0 (P = 0.031). In group 2, no difference was detected. In group 3, propofol depressed H-reflex amplitudes at T2 (H0 vs. H2, P < 0.01), and amplitudes were also lower at T2 than at T1 (H1 vs. H2, P < 0.01). In this group, the H/M ratio decreased from T0 to T2 (H0/M0 vs. H2/M2, P < 0.002).

CONCLUSIONS

During steady state conditions using propofol as the sole agent, a depression of the H-reflex is observed only at a high blood concentration of 9 microg/ml. The authors suggest that immobility during propofol anesthesia is not caused by a depression of spinal motoneuron circuit excitability.

[Sensitivity to atracurium in the lateral abdominal muscles]

OBJECTIVE

To study the effect of atracurium on the electromyographic activity of the lateral abdominal muscles and adductor pollicis in anaesthetized subjects.

STUDY DESIGN

Prospective, comparative, open study.

PATIENTS AND METHODS

Sixteen patients, ASA physical status 1 or 2, undergoing elective orthopaedic surgery under general anaesthesia were studied. Anaesthesia was induced with propofol/fentanyl and orotracheal intubation performed after glottic local anaesthesia without using muscle relaxant. Anaesthesia was maintained with isoflurane/nitrous oxide/oxygen and fentanyl reinjections. Supramaximal percutaneous stimulations in a simple twitch mode (0.1 Hz) were applied at the 9th-10th intercostal nerve on the posterior axillary line and at the ulnar nerve at the wrist. The electromyographic responses were registered using skin surface electrodes, placed on the D9-D10 dermatome in regard of the lateral abdominal muscles and of the thenar muscles. After a single bolus dose of atracurium 0.5 mg.kg-1, the following parameters were studied: the maximum effect (Emax), the time for obtaining Emax (Delay) and the recovery time of 5, 10, 25, 50, 75 and 100% of the control neuromuscular response (T5, T10, T25, T50, T75, T100).

RESULTS

The dose of 0.5 mg.kg-1 of atracurium induced 100% block in both lateral abdominal muscles and adductor pollicis. Lateral abdominal muscles blockade had faster onset (136 +/- 4 s versus 205 +/- 29 s) and shorter recovery, T5, T10, T25, T50, T75 and T100 were significantly (p < 0.05) shorter than at the adductor pollicis.

CONCLUSION

Lateral abdominal muscles blockade have faster onset and recovery than adductor pollicis.

[Effectiveness of low mivacurium if its injection is postponed by a non-invasive pressure determination on the homolateral arm]

OBJECTIVE

We assessed the neuromuscular characteristics of 0.2 mg.kg-1 of mivacurium while its injection was concomitant to a non invasive blood pressure measurement in the ipsilateral arm.

PATIENTS

Thirty-one patients ASA I-II were randomized into two groups. Group cuff (n = 15) and Group control (n = 16).

METHODS

General anaesthesia was induced with fentanyl, thiopentone and mivacurium in all patients, however in the cuff group, measurement of non invasive blood pressure was performed immediately after the injection of mivacurium. Comparison was made on neuromuscular blockade of the adductor pollicis (AP) by mechanomyography, and intubating conditions which were guided by the visual estimation of the orbicularis oculi's (OO) response.

RESULTS

In the cuff group, six out of 15 patients did not have complete blockade at the OO against one out of 16 in the control group, (Fisher exact test p < 0.05). Intubation time was significantly delayed in the cuff group, 201 +/- 66 s versus 123 +/- 32 s in the control group, (t test p < 0.001). The maximum neuromuscular blocking effect at the AP was significantly greater in the control group 99 +/- 2% against 89 +/- 7% in the cuff group, (t test p < 0.01). The onset of maximum blockade at the AP was longer in the cuff group 294 +/- 40 s versus 179 +/- 92 s, (t test p < 0.001] in the control group. Time to 25% recovery was shorter in the cuff group 16 +/- 3 min versus 20 +/- 5 min, in the control group (t test p < 0.05).

CONCLUSION

This study suggests that non invasive blood pressure measurement of the ipsilateral arm, concomitant to the injection of mivacurium decreases the potency of mivacurium. This finding is mostly explained by the early hydrolysis of mivacurium in the plasma of the excluded arm.

The mechanism of pancuronium potentiation of mivacurium block: use of the isolated-arm technique

The neuromuscular blocking effects of mivacurium are greatly enhanced when mivacurium is preceded by a subparalyzing dose of pancuronium. The mechanism of this potentiation has not been elucidated. This study investigated the effects of the anticholinesterase activity of a small dose of pancuronium on the neuromuscular blocking effects of mivacurium. Forty patients were enrolled in the study. The neuromuscular effects of 7.5 and 15 microg/kg pancuronium, followed by 50 and 100 microg/kg mivacurium, were assessed in Groups PM1 and PM2 (n = 20), respectively. The neuromuscular effects of 65 and 130 microg/kg mivacurium were assessed in Groups M1 and M2 (n = 20), respectively. One arm was excluded from circulation with a tourniquet, which was inflated before the injection of pancuronium and deflated 3 min after the injection of mivacurium. The plasma cholinesterase activity was measured before induction for all patients and 3 min after the injection of pancuronium for Groups PM1 and PM2. The plasma cholinesterase activity was decreased by 16% and 33% after pancuronium administration in Groups PM1 and PM2, respectively. In the nonexcluded arm, pancuronium significantly potentiated the effects of mivacurium. In the excluded arm, no significant block was detected for Groups M1 and M2, whereas the maximal degree of neuromuscular block was 79% and 100% for Groups PM1 and PM2, respectively. Using the isolated-arm technique, we suggest that pancuronium potentiation of the neuromuscular blocking effects of mivacurium is more likely attributable to an increase in the effective plasma concentration of mivacurium than to occupancy of postsynaptic acetylcholine receptors.

IMPLICATIONS

Using the isolated-arm technique, we suggest that pancuronium potentiation of the neuromuscular blocking effects of mivacurium is more likely attributable to an increase in the effective plasma concentration of mivacurium than to occupancy of postsynaptic acetylcholine receptors.

Core and thenar skin temperature variation during prolonged abdominal surgery: comparison of two sites of active forced air warming

BACKGROUND

This study was designed to compare the efficacy of two different sites of active forced air warming, upper body or lower body, to maintain normothermia; and their respective effect on thenar skin temperature in relation to the accelerographic monitoring of neuromuscular blockade during long-lasting abdominal surgery.

METHODS

Twenty-six patients were randomised into two groups: upper body, (n=13) and lower body, (n=13), for intraoperative forced air warming. General anaesthesia was induced with thiopentone, sufentanil, and maintained with a mixture of N2O/O2/isoflurane. Pancuronium, 0.1 mg x kg(-1) was used to facilitate tracheal intubation. Reinjection doses of 0.01 mg x kg(-1) were administered once 25% recovery of first twitch height of train-of-four stimulation had occurred, or if surgical relaxation was estimated as inadequate by the surgeon. Thenar skin temperature and core temperature were monitored continuously.

RESULTS

A similar trend for core temperature profile was observed in both groups. After an initial mild hypothermia, normothermia was reached progressively. Normothermia was obtained faster with lower body forced air warming than with upper body (2 h versus 3 h), P<0.05. Thenar skin temperature significantly increased during the first 90 min of surgery. This rise was significantly higher in the upper body group at 40 min and 60 min, P=0.03 and P=0.01, respectively. Stabilisation of thenar skin temperature occurred after 2 h without any further significant difference between groups. Muscle relaxant requirements were not significantly different between the groups.

CONCLUSION

This study suggests that during long-lasting abdominal surgery, normothermia is maintained after 2-3 h by either upper or lower body active forced air warming. After an initial post-induction mild hypothermia, normothermia was achieved faster with lower body surface warming. Thenar skin temperature trend showed that it remained above 32 degrees C during most of the procedure in both groups.

Preemptive intravenous morphine-6-glucuronide is ineffective for postoperative pain relief

BACKGROUND

Morphine-6-glucuronide (M-6-G), a major metabolite of morphine, is reported to be more potent than morphine when administered intrathecally; however, its efficiency remains under debate when administered intravenously. This study was designed to assess the analgesic efficiency of intravenous M-6-G for the treatment of acute postoperative pain.

METHODS

After informed consent was obtained, 37 adults (American Society of Anesthesiologists physical status I-II) who were scheduled for elective open knee surgery were enrolled in the study. General anesthesia was induced with thiopental, alfentanil, and vecuronium and was maintained with a mixture of nitrous oxide/isoflurane and bolus doses of alfentanil. At skin closure, patients were randomized into three groups: (1) morphine group (n = 13), which received morphine 0.15 mg/kg; (2) M-6-G group (n = 12), which received M-6-G 0.1 mg/kg; and (3) placebo group (n = 12), which received saline. At the time of extubation, plasma concentration of morphine and M-6-G was measured. Postoperative analgesic efficiency was assessed by the cumulative dose of morphine delivered by patient-controlled analgesia. Opioid-related side effects were also evaluated.

RESULTS

No difference was noted in patient characteristics and opioid-related side effects. Morphine requirements (mean +/- SD) during the first 24 h in the M-6-G group (41+/-9 mg) and the placebo group (49+/-8 mg) were significantly greater (P<0.05) compared with the morphine group (29+/-8 mg).

CONCLUSION

A single intravenous bolus dose of M-6-G was found to be ineffective in the treatment of acute postoperative pain. This might be related to the low permeability of the blood-brain barrier for M-6-G.

The effects of residual pain on oxygenation and breathing pattern during morphine analgesia

To determine the influence of pain on opioid-induced respiratory depression, we studied oxygenation and breathing patterns in 40 patients scheduled for knee surgery during postoperative patient-controlled analgesia (PCA). After 1 h of morphine PCA, patients were randomized to receive either 20 mL of placebo or bupivacaine 0.25% through a crural nerve catheter and allowed to use PCA for one more hour. Abnormal breathing events were identified and characterized by using the Edentrace II device (Nellcor, Jouy-en-Josas, France). The Spo2 below which the patient spent 25% and 50% of a studied period was calculated (Spo2(25), Spo2(50)). Pain relief with regional analgesia increased the incidence of abnormal respiratory events associated with oxygen desaturation: during the second period, the pain score was lower in the bupivacaine group (0.7+/-1 vs 4.1+/-1.2), morphine consumption was larger in the placebo group (4.2+/-1.3 vs 0.7+/-1.4 mg), and there were more abnormal obstructive breathing events in the bupivacaine group (11+/-16 vs 3.7+/-4.3). Spo2(25) and Spo2(50) were lower in the bupivacaine than in placebo group (91.5%+/-2.8% vs 93.1%+/-2.1%, 92.9%+/-2.4% vs 94.2%+/-1.8%).

IMPLICATIONS

Pain relief with regional analgesia in patients previously treated with opioids increases the incidence of abnormal respiratory events associated with oxygen desaturation.

A comparison of two techniques for cervical plexus blockade: evaluation of efficacy and systemic toxicity

We compared two techniques of cervical plexus blockade (CPB) for carotid endarterectomy. Cervical plexus nerve block was performed with a combination of bupivacaine and lidocaine, with injections at the C2-C3, C3-C4, and C4-C5 transverse processes in 11 patients (classical CPB) or with a single injection after localization of the cervical plexus with a nerve stimulator in 12 patients (interscalene CPB). Pain scores were obtained during block placement and at predetermined phases of the operation. Arterial blood was sampled before and 3, 5, 8, 10, 15, 25, 40, and 60 min after CPB for measurement of bupivacaine and lidocaine concentrations. Interscalene CPB was less painful than classical CPB. The techniques appeared equally effective. Patients in both groups required equivalent supplementation with IV fentanyl and additional local infiltration with lidocaine during the most painful stages of surgery. The maximal concentration of bupivacaine was lower in interscalene CPB compared with classical CPB (1.0 microg/mL versus 1.5 microg/mL, P < 0.01). The time required to reach the maximal concentration of bupivacaine was 15 (10-40) min in interscalene CPB and 10 (5-17) min in classical CPB (P < 0.05). Lidocaine maximal concentration was similar in both groups, however the time required to reach the maximal concentration was longer (P < 0.05) in interscalene CPB (15 [10-60] min) than in classical CPB (10 [8-20] min). We conclude that the interscalene CPB is as effective as the classical CPB as a regional technique for carotid endarterectomy and may be associated with a lower systemic absorption of bupivacaine.

IMPLICATIONS

Cervical plexus blockade for carotid endarterectomy can be effectively performed with a single injection after localization of the cervical plexus with a nerve stimulator. This technique is simple and was associated with less systemic absorption of local anesthetic than the multiple-injection technique.

Pharmacokinetics and pharmacodynamics of rapacuronium in patients with cirrhosis

BACKGROUND

Delayed elimination kinetics of steroidal neuromuscular blocking agents have been observed in patients with cirrhosis. Like other steroidal muscle relaxants, rapacuronium may, in part, be eliminated by the liver. To determine the influence of liver disease on its neuromuscular blocking effect, we studied the pharmacokinetics and pharmacodynamics of rapacuronium in patients with cirrhosis.

METHODS

Sixteen patients undergoing elective surgery or endoscopy with general anesthesia, eight with cirrhosis and eight with normal liver function, were studied. Anesthesia was induced with fentanyl 2 microg/kg and thiopental 5-7 mg/kg and maintained with 60% nitrous oxide and 0.6-0.8% isoflurane in oxygen and repeated doses of fentanyl 1 microg/kg. Rapacuronium 1.5 mg/kg was administered intravenously before tracheal intubation. Thumb adduction force evoked by supramaximal ulnar nerve stimulation was recorded in 16 patients. Venous blood was sampled at frequent intervals for 8 h. Rapacuronium and its breakdown product Org 9488 were measured in plasma by high-pressure liquid chromatography. Values are reported as median (range).

RESULTS

The central volume of distribution was increased to 131 (104-141) ml/kg in patients with cirrhosis (P < 0.01), compared with 75 (47-146) ml/kg in controls. The total apparent volume of distribution was also increased (P < 0.05) to 331 (284-488) ml/kg in patients with cirrhosis, compared with 221 (124-285) ml/kg in controls. The elimination half-life was 88 (77-102) min in controls and 90 (76-117) min in patients with cirrhosis. Plasma clearance was increased (P < 0.05) to 6.9 (6.1-8.9) ml x min(-1) x kg(-1) in patients with cirrhosis, compared with 5.3 (4.2-8.4) ml x min(-1) x kg(-1) in controls. Rapacuronium neuromuscular blocking effect was similar between the two groups. Onset time was 65 (40-110) s in controls and of 60 (52-240) s in patients with cirrhosis. Time to return to 90% of thumb adduction force control value was of 49 (28-80) min in controls and 47 (28-71) min in patients with cirrhosis.

CONCLUSION

The neuromuscular blocking effect of a single bolus dose of rapacuronium in patients with cirrhosis is not different from that of patients with normal hepatic function. No decrease in plasma clearance of rapacuronium was observed in patients with cirrhosis.

Ondansetron is more effective than metoclopramide for the treatment of opioid-induced emesis in post-surgical adult patients. Ondansetron OIE Post-Surgical Study Group

Nausea and vomiting are common side effects of opioids administered for pain control. This double-blind, randomized, parallel-group study evaluated the anti-emetic efficacy and tolerability of single intravenous (i.v.) doses of ondansetron 8 mg, ondansetron 16 mg and metoclopramide 10 mg in the treatment of opioid-induced emesis. Adult patients undergoing low emetogenic surgical procedures, using a standardized anaesthesia regimen were assessed for 24 h following administration of study anti-emetic to treat established post-surgical opioid-induced emesis. A total of 4511 patients were enrolled of whom 1366 experienced opioid-induced emesis and received randomized study medication. Ondansetron 8 mg and 16 mg were significantly better than metoclopramide 10 mg (P < 0.05) for both complete control of emesis, complete control of nausea and other efficacy measures. There were no significant differences between the two ondansetron groups. All three treatments were well tolerated. In conclusion, this large, multicentre study demonstrates that ondansetron is more effective than metoclopramide in the treatment of opioid-induced emesis following administration of post-surgical opioids to control pain.

Postoperative obstructive apnea

We studied electromyography (EMG) of the geniohyoid muscle (Gh) and diaphragm (Di) in 12 postoperative, premedicated (flunitrazepam 2 mg PO), asymptomatic patients who snored after recovering from general anesthesia, the induction of which was partly achieved by i.v. midazolam. After extubation of the trachea, integrated EMG activity of Gh (E-Gh(MTA)) and Di (E-Di(MTA)) were measured. For Gh, tonic and phasic activity were distinguished. Patients were studied during obstructive apnea, at the end of apnea, while breathing through an artificial Guedel airway, and during quiet breathing 5 min after flumazemil. All patients experienced episodes of postoperative upper airway obstruction and nine became apneic. Flumazenil restored consciousness and predominant tonic E-GhMTA associated with upper airway patency in all patients. Reduced tonic E-GhMTA characterized postoperative obstructive apnea. Resolution of apnea required a burst of both tonic and phasic E-GhMTA associated with intense E-Di(MTA). Breathing through the Guedal airway resulted in patent airway in 8 of 10 patients and was associated with low tonic and phasic E-GhMTA and reduced E-Di(MTA). In this study, we demonstrated that the tonic pharyngeal muscular support modulates airway patency in the postoperative period. Because it is reversed by flumazemil, benzodiazepines are certainly the main cause of airway obstruction in these patients.

IMPLICATIONS

Upper airway obstruction during recovery from general anesthesia induced by i.v. midazolam is associated with low tonic pharyngeal muscular support, which modulates upper airway patency in the postoperative period.

Nitrous oxide increases endotracheal cuff pressure and the incidence of tracheal lesions in anesthetized patients

The pressure in air-filled endotracheal cuffs increases steadily throughout general anesthesia with nitrous oxide (N2O). High cuff pressures can be responsible for local ischemia, which may induce tracheal mucosal injury. In this study, cuff pressure was monitored in anesthetized patients, and postanesthesia endotracheal lesions were assessed by endoscopy. Sixty-five patients undergoing general anesthesia with tracheal intubation >1 h in duration were randomized into two groups. The endotracheal tube cuff was inflated to 30-40 cm H2O with air in Group 1 (n = 33) and with a gas mixture (N2O 50% in oxygen) in Group 2 (n = 32). At the time of tracheal extubation, a fiberoptic examination via the endotracheal tube was performed by an independent observer. Aspects of trachea at the level of cuff contact area were scored as 0 = normal, 1 = mucosal erythema or edema, 2 = mucosal erosion or hemorrhage, 3 = mucosal erosion or hemorrhage on both anterior and posterior tracheal walls. Cuff pressure increased throughout the procedure (P<0.01) in Group 1 and remained stable in Group 2. In Group 1, tracheal lesions in the area of the cuff were more frequent than they were in Group 2 (79% vs. 37%; P<0.001). Tracheal injury was correlated to cuff pressure (r = 0.62, P<0.001). No postoperative respiratory complication was observed in any patient. In patients anesthetized with N2O, the inflation of the tracheal tube cuff with a gas mixture of the same composition as the inhaled mixture can prevent excessive cuff pressure and reduce the incidence of tracheal injury.

IMPLICATIONS

In patients anesthetized with nitrous oxide, the inflation of the tracheal tube cuff with a gas mixture of the same composition as the inhaled mixture can prevent excessive cuff pressure and reduce the incidence of tracheal injury.

Opposite changes in dopamine metabolites and met-enkephalin levels in the ventricular CSF of patients subjected to thalamic electrical stimulation

High-frequency electrical stimulations of thalamic nuclei are currently used for the suppression of parkinsonian or essential tremor and for the relief of some types of intractable pain in man. However, the mechanisms by which such stimulations exert their therapeutic effects are essentially unknown. Attempts were made to provide some insight into these mechanisms by measuring the levels of the dopamine metabolites homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC), the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) and met-enkephalin-like immunoreactivity in ventricular cerebrospinal fluid (CSF) of patients with Parkinson's disease (PD) or multiple sclerosis (MS) after a 30-minute therapeutic electrical stimulation of the ventralis intermedius nucleus of the thalamus. In nonstimulated control patients, the levels of these compounds did not significantly differ in two CSF samples taken 30 minutes apart. In stimulated patients, a decrease in dopamine metabolite levels associated with a relative increase in met-enkephalin-like immunoreactivity were observed in the CSF sample taken after the 30-minute stimulation as compared to the sample taken immediately before the stimulation. In contrast, the levels of 5-HIAA remained unaffected by the stimulation. These data confirmed the existence of negative interactions between dopaminergic and enkephalinergic systems in man similar to those previously demonstrated in rats. In addition, they suggest that alterations in dopaminergic or enkephalinergic neurotransmission might be involved in the therapeutic action of thalamic electrical stimulation in patients with parkinsonian symptoms and other patients.

Effects of an intubating dose of succinylcholine and rocuronium on the larynx and diaphragm: an electromyographic study in humans

BACKGROUND

Paralysis of the vocal cords is one objective of using relaxants to facilitate tracheal intubation. This study compares the neuromuscular blocking effect of succinylcholine and rocuronium on the larynx, the diaphragm, and the adductor pollicis muscle.

METHODS

Electromyographic response was used to compare the neuromuscular blocking effect of succinylcholine and rocuronium on the laryngeal adductor muscles, the diaphragm, and the adductor pollicis muscle. Sixteen patients undergoing elective surgery were anesthetized with propofol and fentanyl, and their tracheas were intubated without neuromuscular blocking agents. The recurrent laryngeal and phrenic nerves were stimulated at the neck. The electromyographic response was recorded from electrodes placed on the endotracheal tube and intercostally before and after administration of 1 mg/kg succinylcholine or 0.6 mg/kg rocuronium.

RESULTS

The maximum effect was greater at the adductor pollicis (100 and 99%) than at the larynx (96 and 97%) and the diaphragm (94 and 96%) after administration of succinylcholine and rocuronium, respectively (P < or = 0.05). Onset time was not different between the larynx (58+/-10 s), the diaphragm (57+/-8 s), and the adductor pollicis (54+/-13 s), after succinylcholine (all mean +/- SD). After rocuronium, onset time was 124+/-39 s at the larynx, 130+/-44 s at the diaphragm, and 115+/-21 s at the adductor pollicis. After succinylcholine administration, time to 90% recovery was 8.3+/-3.2, 7.2+/-3.5, and 9.1+/-3.0 min at the larynx, the diaphragm, and the adductor pollicis, respectively. Time to 90% recovery after rocuronium administration was 34.9+/-7.6, 30.4+/-4.2, and 49.1+/-11.4 min at the larynx, the diaphragm, and the adductor pollicis, respectively.

CONCLUSION

Neuromuscular blocking effect of muscle relaxants on the larynx can be measured noninvasively by electromyography. Although the larynx appears to be resistant to muscle relaxants, we could not demonstrate that its onset time differed from that of peripheral muscles.

[Pharmacokinetic evaluation of a computerized target-controlled infusion system: application to propofol in orthopedic surgery]

PaMo 2.0, a type of software, includes a pharmacokinetic model for propofol in the adult. It allows both administration and monitoring of propofol target-controlled infusions. In order to evaluate PaMo 2.0, a prospective clinical trial compared, at defined infusion times, predicted and measured plasma propofol concentrations, in 28 patients programmed for hip-replacement surgery. A propofol plasma determination technique had first been validated, including high performance liquid chromatography with fluorescence detection. A statistical analysis based on correlation (r = 0.73), inaccuracy = 29.18 per cent, bias = 11.67 per cent, wobble = 19.15 per cent, and divergence = -0.06 per cent/min calculation, related to this system, has been carried out. PaMo 2.0 under-estimated plasma propofol concentrations. The convergence between predicted and measured propofol concentrations was good and not modified in respect of infusion time. This infusion system is suitable for propofol administration, but the integration of Bayesian pharmacokinetic models would greatly improve propofol plasma concentration estimation and regimen adaptation to each patient.

Is the recovery profile of mivacurium independent of the rate of decay of its plasma concentration in patients with normal plasma cholinesterase activity?

BACKGROUND

The duration of action of muscle relaxants is poorly correlated to the rate of decay of their plasma concentration. The plasma concentration of mivacurium may rapidly decrease below its active concentration because of the extensive hydrolysis of mivacurium. By inflating a tourniquet on one upper limb for 3 min after the administration of atracurium, mivacurium or vecuronium, we studied the influence of the initial decline of their plasma concentration on their effect.

METHODS

In 50 patients anaesthetised with thiopental, isoflurane and fentanyl, the effect of bolus doses of 0.15 or 0.25 mg.kg-1 mivacurium (MIV 15, MIV 25), 0.3 or 0.5 mg.kg-1 atracurium (ATR 30, ATR 50) and 0.06 or 0.1 mg.kg-1 vecuronium (VEC 06, VEC 10) were measured on both arms (evoked response of the adductor pollicis to train-of-four stimulation every 12 s), a tourniquet being applied on one arm just before and during 3 min after the muscle relaxant bolus.

RESULTS

Tourniquet inflation of 3 min almost abolished the neuromuscular effect of mivacurium. In the vecuronium groups and in the ATR 50 group, tourniquet inflation did not modify the maximum degree of depression of the twitch response. Also, the duration of action of vecuronium was unaffected by the tourniquet. In the ATR 30 group, times to return of the twitch response to 25% (duration 25%) and 75% (duration 75%) of control response were significantly shorter in the cuffed arm, 23 min vs 27 min, and 41 min vs 45 min, respectively. In the ATR 50 group, only duration 25% was significantly shorter in the cuffed arm (41 min vs 45 min).

CONCLUSION

The results suggest that the rate of decline of the plasma concentration of mivacurium is so rapid, that a very low and almost clinically ineffective concentration is present as soon as 3 min after its administration. The results also indicate that the recovery from a mivacurium-induced neuromuscular blockade is not influenced by the rate of decay of its plasma concentration in patients with genotypically normal plasma cholinesterase.

[Tracheal intubation in prehospital resuscitation: importance of rapid-sequence induction anesthesia]

OBJECTIVE

To investigate complications of emergency endotracheal intubation (EEI), possibly facilitated by rapid-sequence induction, in the prehospital critical care setting: 1) the difficulty of intubation; 2) the cardiorespiratory consequences of intubation; 3) the relationship between the occurrence of complications and prognosis.

STUDY DESIGN

Prospective non randomized, open study.

PATIENTS

All patients treated over a 5-month period by a physician-manned ambulance service and requiring EEI.

METHODS

Patients were allocated either in with cardiac arrest (CA) group or a group with maintained spontaneous circulation (SC). Difficulty of intubation was assessed by the number of attempts.

RESULTS

Two hundred and twenty-four consecutive EEI were carried out by physicians (46%) and residents (38%) not trained in anaesthesia, anaesthetists (8%), or nurse anaesthetists (7%). Trachea was intubated after a maximum of three attempts in all patients. Success rate at the first attempt was 91%. It was 92% in CA patients (n = 76) and 90% in SC patients (P = 0.59). Anaesthetic induction, with (n = 112) or without (n = 12) succinylcholine, was used to facilitate 84% of intubations in SC patients. Complications occurred in 30 patients (20%). There was no relationship between the latter and hospital mortality, duration of ventilatory support, duration of stay in the intensive care unit.

CONCLUSION

In this study, EEI in SC patients was frequently facilitated by rapid sequence induction and was associated with a high success rate at the first attempt, as in CA patients. Morbidity was low. All physicians involved in emergency airway management should be skilled in this technique.