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.

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.

Effect of fasting on substrate specificity of rat liver UDP-glucuronosyltransferase.

The effect of a 3-day period of complete starvation on the hepatic UDPglucuronosyltransferase activity was studied in the rat. The substrate specificity of the enzyme was assayed with bilirubin as a carboxylic acceptor, and phenolphthalein and p-nitrophenol as phenolic acceptors. Starvation increased the bilirubin UDPglucuronosyltransferase specific activity by 33%, whereas no increase in specific activities appeared when the phenolic substrates were used. However, on a total liver weight basis, all three activities were significantly lower than those of the controls. Kinetic studies of activated microsomal bilirubin UDPglucuronosyltransferase showed that apparent Km values were similar; fasting acted only by increasing V. The results suggest that the changes in bilirubin glucoronosyltransferase activity provoked by starvation may reflect actual enzyme induction; they favour the multiplicity of the UDPglucuronosyltransferase system.

Enflurane anesthesia and antipyrine metabolism.

To evaluate the influence of enflurane anesthesia on the hepatic drug-metabolizing capacity, antipyrine half-life was measured in 18 surgical patients before surgery and on days 4 and 8 after anesthesia. The effect of repeated administration of antipyrine on the rate of antipyrine metabolism was also evaluated in nine control subjects. Simultaneous measurement of plasma fluoride concentration allowed enflurane metabolism to be quantitated. Regardless of duration, enflurane anesthesia did not increase the rate of antipyrine metabolism as indicated by the absence of significant change in antipyrine half-life and clearance. Repeated doses of antipyrine to nine normal subjects did not influence the rate of antipyrine metabolism. Preanesthesia elimination rate of antipyrine did not indicate individual capacity to metabolize enflurane. Mean peak fluorides level (10.7 +/- 4.8 mM) was reached 3 hr after anethesia and did not appear to correlate with duration of exposure to enflurane.

Pancuronium blood level monitoring in patients with tetanus.

Overdosage of muscle relaxant has been given as a possible explanation for the hypotensive episodes occurring during the management of tetanus. The aim of the present work was to study the pharmacokinetics of pancuronium during long term infusion. Pancuronium was administered to eight patients with severe tetanus for a period varying from 8 to 24 days. The concentration of pancuronium was measured daily in plasma and urine using a fluorimetric method. The plasma concentration varied from 0.27 to 0.48 microgram/ml. No tendency to accumulation was observed. The plasma concentration fell rapidly below the level associated with muscle relaxation when pancuronium was discontinued. This absence of accumulation can be explained by a rapid elimination of pancuronium through the kidney according to a process of ultrafiltration.

Test of 20 similar intensive care ventilators in daily use conditions--evaluation of accuracy and performances.

Infrequent control, aging of components, may compromise the accuracy of ICU ventilators. In order to assess the reliability of ventilators during their clinical use, we bench tested a group of 20 CPU1 ventilators (Ohmeda) sampled at random in several ICU units. We found major leaks in 5 ventilators, attributable to the disposable tubings used in these systems. Mean error in expired tidal volume and corresponding standard deviation (precision) were greater than 100 ml in two. Positive end expiratory pressure measurement comprised a mean error higher than 2 cm H2O in 40% of the ventilators tested. The valve opening pressure threshold was correlated to the inspiratory flow (r = 0.81) contrary to the valve opening delay (average 138 +/- 40 ms). These two parameters did not correlate with the age of the ventilator. Our study addresses the need for periodic control of ventilator performance in order to minimize the risks of errors and malfunctions.

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%.

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.

[Current data on curarization]. / Données actuelles de la curarisation.

The knowledge of the mechanism of action of neuromuscular blocking agents has improved together with the better understanding of the physiology of the neuromuscular junction at the molecular and cellular levels. The main action of competitive neuromuscular relaxants is the blockade of the acetylcholine binding site of the acetylcholine receptor when the latter is its inactive-closed conformation. Owing to the high margin of safety of the neuromuscular transmission, the blockade of an important fraction (75-90%) of acetylcholine receptors is necessary to cause a decrease in muscle strength. An other mechanism of action of competitive agents is the blockade of presynaptic secretion of acetylcholine during repetitive stimulations which may explain the phenomenon of train of four fade or of tetanic fade.

[Pharmacokinetic evaluation of a computerized target-controlled infusion system: application to propofol in orthopedic surgery]. / Evaluation pharmacocinétique d'un système informatisé de perfusion à objectif de concentration: application au propofol en chirurgie orthopédique.

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.

[Diprivan and epilepsy]. / Diprivan et épilepsie.

Propofol can be used safely in patients with a history of epilepsy. In the known epileptic patient, propofol is not contra-indicated, provided that the anaesthetist ensures that the anti-epileptic treatment is correctly maintained.

[Respiratory effects of propofol]. / Effets respiratoires du propofol.

Like other general anaesthetics, propofol exerts a respiratory depressant effect. Apnoea is especially frequent during induction of anaesthesia by propofol; it differs from that caused by barbiturates by its longer duration. During continuous administration, propofol exerts the same effect on respiratory function as other general anaesthetics, with an increased respiratory rate, diminished tidal volume and hypercapnia.

[Effectiveness of low mivacurium if its injection is postponed by a non-invasive pressure determination on the homolateral arm]. / L'efficacité du mivacurium baisse si son injection est retardée par une prise de pression non-invasive sur le bras homolatéral.

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.

[Sensitivity to atracurium in the lateral abdominal muscles] . / Sensibilité à l'atracurium des muscles abdominaux latéraux.

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.

[Muscle relaxant effect of atracurium in patients with chronic renal failure]. / Effet myorelaxant de l'atracurium chez les patients insuffisants rénaux chroniques.

The muscle relaxant effect of atracurium was monitored by measuring the strength of the adductor pollicis muscle (TH) elicited by supramaximal stimulation of the ulnar nerve at the wrist. In order to facilitate tracheal intubation, a dose of 0.6 mg X kg-1 was administered in 10 patients with complete renal failure. The results were compared with those obtained from 20 normal patients. The dose of 0.6 mg X kg-1 produced adequate conditions for tracheal intubation. A 95% or more depression of TH was obtained in both groups after 3 min. The duration of effect was similar in both groups. The delay between injection and 75% recovery of TH was of 62 min in controls and 52 min in patients with renal failure. Only the recovery index (the time elapsed between 25% and 75% recovery) was shorter in patients with renal failure (p less than 0.01): 8 min instead of 14 min in the controls.

[Use of halothane in a semi-closed circuit]. / Utilisation de l'halothane en circuit semi-fermé.

Halothane was administered to 10 ASA or 11 patients undergoing elective peripheral surgery. The vaporizer was included in the delivery gas line of the semiclosed system. Löwe's square root of time model of uptake was used to calculate the required doses of halothane. In order to reach an alveolar concentration corresponding to 1.3 MAC, 0.5 vol % of halothane (1.3 MAC) combined with 60 vol % of nitrous oxide (0.6 MAC) were administered at a fresh of 20 ml.kg-1. The ventilation controlled in order to maintain end-tidal CO2 partial pressure at a 5 vol %. Inspiratory halothane concentration was measured during the inspiratory plateau. The alveolar fraction was defined as being the mean end expiratory concentration. The latter was well above the theoretical values during the first 9 min of anaesthesia (0.85% at the 4 th min). This concentration then decreased progressively, becoming less than the expected value after 15 min (0.4% at the 30 th min). Löwe's model would therefore seem to lead to a gross overestimation of the amount of anaesthetic vapour to be delivered to a patient at the beginning of anaesthesia, and an underestimation thereafter.

[Anesthesia for thalamic stimulations: value of flumazenil]. / Anesthésie pour stimulations thalamiques: intérêt du flumazénil.

Five cases are reported of peroperative awakening in order to obtain patient cooperation during stereotaxic procedures. General anaesthesia was induced with 0.25 mg.kg-1 midazolam, 1.5 to 2 micrograms.kg-1 fentanyl, and 0.1 mg.kg-1 vecuronium. Maintenance was obtained with isoflurane, nitrous oxide, and small doses of fentanyl. Isoflurane inhalation was discontinued 30 to 40 min before the time of awakening required by surgery. Once expiratory isoflurane concentration reached a level less than or equal to 0.1%, nitrous oxide administration was stopped, and 0.5 mg flumazenil administered. After surgical checking, on the fully awake patient of the efficiency of thalamic stimulation and the lack of any motor deficit, anaesthesia was deepened again, with either isoflurane or a non benzodiazepine intravenous agent. All five patients recovered rapidly and calmly.

[Spontaneous development of paralysis induced by equipotent doses of vecuronium, atracurium, fazadinium, pancuronium, gallamine and d-tubocurarine]. / Evolution spontanée de la paralysie obtenue par des doses équipotentes de vécuronium, atracurium, fazadinium, pancuronium, gallamine et d-tubocurarine.

Thirty-six patients undergoing elective surgery were studied after obtaining their informed consent. They were randomly assigned to six series of six patients each. One hour before anaesthesia, all patients received 0.2 mg.kg-1 diazepam orally. After induction of anaesthesia with 1-1.5 mg.kg-1 methohexitone and 5 micrograms.kg-1 fentanyl, the patients were paralysed and ventilation was controlled manually (semi-open circuit; 50% N2O/50% O2). Each patient received a single dose of either 70 micrograms.kg-1 fazadinium, 70 micrograms.kg-1 pancuronium, 2,500 micrograms.kg-1 gallamine or 450 micrograms.kg-1 d-tubocurarine. Neuromuscular function was monitored by measuring the isometric contraction of the adductor pollicis muscle in response to supramaximal stimulations of the ulnar nerve at the wrist (square wave pulse of 0.2 ms duration at supramaximal intensity delivery at 0.1 Hz). Three parameters were measured: the time between the injection of the relaxant drug and recovery of the twitch height at 50% of its baseline (RT0-50); the time between the injection of the relaxant drug and recovery of the twitch height at 90% of its baseline (RT0-90); the time between the injection of the relaxant drug and recovery of the twitch height from 25 to 75% of its baseline (RT25-75). The values of the observed parameters were expressed in minutes (means +/- SEM).(ABSTRACT TRUNCATED AT 250 WORDS)

[Refractory cancer pain. Subarachnoid or epidural administration of morphine]. / Douleurs cancéreuses rebelles. Administration de morphine par voie sous-arachnoïdienne ou péridurale.

Spinal analgesia, a new method for relieving refractory cancer pain, was tested in 19 patients. A catheter was installed in the subarachnoid (17 cases) or peridural (2 cases) space and connected to a subcutaneous site of injection. The success rate at 10 days was 68%. In 11 patients pain was relieved throughout the course of the malignant disease, with doses that did not exceed 6 mg in 7 patients and 10 mg in the remaining 4 patients. The most severe complications were leakage of the cerebrospinal fluid in 1 case, meningitis after 18 months of injection in 1 case and displacement of the catheter in 3 cases.