Effects of airway occlusion on breathing muscle electromyogram signals, during isoflurane anaesthesia, with and without the effects of fentanyl and hypercapnia.

BACKGROUND: Expiratory muscle action is prominent during anaesthesia and can impair lung function. This activity is exaggerated by the use of opioids. Airway pressure during occlusion of expiration would be a valuable measure in the study of expiratory muscle activation. However, this would only be valid if the imposed occlusion did not itself alter muscle activation. This possibility can be checked by directly assessing muscle activity by electromyography; varying arterial carbon dioxide tensions and opioid action should be considered. METHODS: We studied seven spontaneously breathing patients, anaesthetized with nitrous oxide and isoflurane, in four conditions: during an infusion of fentanyl and after naloxone, breathing normally and with breathing stimulated with CO(2). We compared diaphragm and external oblique abdominal electromyogram (EMG) signals during normal and occluded breaths. We also measured chest wall volume and compared airway occlusion pressure, during inspiration and expiration, with the EMG results. RESULTS: Inspiratory occlusion increased the duration of inspiration during hypercapnia by 20%, but not the rate of electrical activation of the diaphragm, indicating that occlusion does not cause a reflex increase in diaphragm contraction. In contrast, expiratory occlusion did not affect either the duration of expiration or the electrical activity of the external oblique muscles. CONCLUSIONS: In these conditions, except for a change in inspiratory duration, respiratory muscle activity is unaffected by airway occlusion. Airway occlusion will permit valid measures of muscle activity in inspiration and expiration and provide simple measurements of respiratory muscle function during anaesthesia.

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.

[French survey of neuromuscular relaxant use in anaesthetic practice in adults]. / Enquête de pratique sur l'utilisation en France des curares chez l'adulte en anesthésie.

Guidelines about the use of neuromuscular blocking agents based on a national consensus conference have been published in 2000. A survey was carried out to assess adherence to these guidelines. An online questionnaire was designed from the different guidelines concerning the use of muscle relaxant for tracheal intubation and surgery, monitoring and antagonism of neuromuscular blockade. In addition, question about the knowledge of the pharmacodynamics of neuromuscular blocking agents were asked. Analysis concerned 1230 answers from senior anaesthetists. Tracheal intubation is facilitated by the use of a competitive agent or by succinylcholine by 58 and 8% of responders respectively. Atracurium and cisatracurium were most frequently used (49 and 44%, respectively). The duration of effect of an intubating dose of atracurium, vecuronium or rocuronium was estimated equal or below 60 min by more than half of responders, whereas that of cisatracurium was longer. Fifty-two or 74% of responders used neuromuscular monitoring, whether a single or repeated dose of muscle relaxant was administered. Antagonism of neuromuscular blockade was systematic, frequent, and episodic or excluded by 6, 26, 55 and 13% of responders, respectively. Monitoring and antagonism of neuromuscular blockade are underused despite the guidelines. Underestimation of the risk of postoperative residual curarization is linked to the underestimation of the duration of competitive neuromuscular blocking agents.

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.

[Thrombosis of a cardiopulmonary bypass circuit despite recommended hypocoagulation with danaparoid during the acute phase of type II heparin-induced thrombocytopenia]. / Thrombose d'un circuit de circulation extracorporelle sous danaparoïde sodique à la phase aiguë d'une thrombopénie induite par l'héparine de type II en dépit d'une hypocoagulation recommandée.

A 36-year-old patient was admitted to our hospital with ischaemic stroke. The initial assessment allowed the diagnosis of an antiphospholipid syndrome (APS) and an intracardiac mass suggestive of a heart tumour. The patient was treated with unfractionated heparin. Type II heparin-induced thrombopenia (HIT) was diagnosed on the 18th day of therapy. Given the risk of stroke recurrence it was decided to remove the cardiac tumour surgically. Cardiopulmonary bypass (CPB) was performed using danaparoid in a state of deep hypothermia, in accordance with the well-established protocol in use in our department. As the CPB and surgical procedure came to an end a massive thrombus began forming in the circuit, requiring immediate displacement of the CPB cannulae. The anti-Xa activity level obtained had been considered effective at an estimated 1.20 IU/ml, although, the level recommended by Magnani is between 1.50 and 2.0 IU/ml. There was no clinical consequence and postoperative recovery was uneventful. The discrepancy between the satisfactory level of anti-Xa activity and the thrombus formation in the CPB circuit raises the issue of the diversity of published anticoagulation protocols, the difficulty to extrapolate within a surgical team, the need for intensive laboratory monitoring within a narrow therapeutic range, as well as the patient profiles variability with concurrent disorders complicating their clinical management.

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: a randomized-controlled trial.

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.

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.

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.

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.