Can local vibration alter the contribution of persistent inward currents to human motoneuron firing?

The response of spinal motoneurons to synaptic input greatly depends on the activation of persistent inward currents (PICs), which in turn are enhanced by the neuromodulators serotonin and noradrenaline. Local vibration (LV) induces excitatory Ia input onto motoneurons and may alter neuromodulatory inputs. Therefore, we investigated whether LV influences the contribution of PICs to motoneuron firing. This was assessed in voluntary contractions with concurrent, ongoing LV, as well as after a bout of prolonged LV. High-density surface electromyograms (HD-EMG) of the tibialis anterior were recorded with a 64-electrode matrix. Twenty males performed isometric, triangular, dorsiflexion contractions to 20% and 50% of maximal torque at baseline, during LV of the tibialis anterior muscle, and after 30-min of LV. HD-EMG signals were decomposed, and motor units tracked across time points to estimate PICs through a paired motor unit analysis, which quantifies motor unit recruitment-derecruitment hysteresis (ΔF). During ongoing LV, ΔF was lower for both 20% and 50% ramps. Although significant changes in ΔF were not observed after prolonged LV, a differential effect across the motoneuron pool was observed. This study demonstrates that PICs can be non-pharmacologically modulated by LV. Given that LV leads to reflexive motor unit activation, it is postulated that lower PIC contribution to motoneuron firing during ongoing LV results from decreased neuromodulatory inputs associated with lower descending corticospinal drive. A differential effect in motoneurons of different recruitment thresholds after prolonged LV is provocative, challenging the interpretation of previous observations and motivating future investigations. KEY POINTS: Neuromodulatory inputs from the brainstem influence motoneuron intrinsic excitability through activation of persistent inward currents (PICs). PICs make motoneurons more responsive to excitatory input. We demonstrate that vibration applied on the muscle modulates the contribution of PICs to motoneuron firing, as observed through analysis of the firing of single motor units. The effects of PICs on motoneuron firing were lower when vibration was concurrently applied during voluntary ramp contractions, likely due to lower levels of neuromodulation. Additionally, prolonged exposure to vibration led to differential effects of lower- vs. higher-threshold motor units on PICs, with lower-threshold motor units tending to present an increased and higher-threshold motor units a decreased contribution of PICs to motoneuron firing. These results demonstrate that muscle vibration has the potential to influence the effects of neuromodulation on motoneuron firing. The potential of using vibration as a non-pharmacological neuromodulatory intervention should be further investigated.

[Caudal anesthesia in infants and children]. / Anesthésie caudale chez le nourrisson et le petit enfant.

Caudal analgesia may be used with general anaesthesia in painful surgery. Caudal anaesthesias were performed by the authors, as the single anesthetic technic for digestive or orthopedic surgery in nine children. The technic is sure, efficient and without any complications. Caudal anaesthesia seems to be interesting in the child with respiratory pathology or with morphologic facial abnormalities.

[Laryngeal paralysis after tracheal intubation for anesthesia]. / Paralysie laryngée après intubation trachéale en anesthésie.

A 17 year old man was anaesthetized for osteosynthesis of a fractured left femoral diaphysis. Endotracheal intubation was easy, anaesthesia and surgery were both uneventful. On recovery, some hoarseness was noticed. Two months later, an ENT examination showed signs of laryngeal paralysis. The presumed explanation was compression of the recurrent nerve by the high-positioned balloon of the tracheal tube. Recovery was complete four months later.

[A rare cause of postoperative acute respiratory insufficiency: diaphragmatic hernia]. / Une cause rare d'insuffisance respiratoire aiguë postopératoire: la hernie diaphragmatique.

A case of postoperative failure after total hip replacement is described. A gastric tube was passed and the stomach was seen to be within the right hemithorax on the chest X-ray. Aspiration of gastric gas and juice relieved the respiratory symptoms.

[Cholinesterases]. / Les cholinestérases.

OBJECTIVE: To review current data on butyrylcholinesterase. DATA SOURCES: Search through Medline data bases of articles in French or English. STUDY SELECTION: Original articles and case reports were selected. Letters to editor were excluded. DATA EXTRACTION: The articles were analyzed in order to obtain current data on biochemical structure, action, major pathological variations, especially with regard to the recent informations obtained by molecular biology concerning the identification of genetic variants. DATA SYNTHESIS: Butyrylcholinesterase must be differentiated from acetylcholinesterase, which cannot hydrolyse succinylcholine. The physiological action of butyrylcholinesterase remains unknown, although it can hydrolyse many drugs. Excluding genetical mutations, several physiopathological situations alter butyryl-cholinesterase activity. Butyrylcholinesterase activity assessment does not allow the diagnosis of genetic variants. Whatever the origin, only deficits of more than 50% modify significantly the metabolism of succinylcholine or mivacurium. The diagnosis of a prolonged neuromuscular blockade is obtained with systematic monitoring of the neuromuscular function in case of administration of mivacurium or succinylcholine. Mivacurium should only be re-injected when one response at train of four is obtained. In case of prolonged neuromuscular blockade, the anticholinesterasic agent should not be administered when no response at train of four is obtained. The biochemical methods using inhibitors (dibucaine, fluoride) of the butyrylcholinesterase and a familial study lead to the diagnosis in most cases because the atypical and fluoride variants are the most frequent. When results are doubtful, genetic molecular methods with the use of PCR and restriction enzymes allow a rapid diagnosis.

[Pneumomediastinum and subcutaneous emphysema after translaryngeal jet ventilation]. / Pneumomédiastin et emphysème sous-cutané au décours d'une ventilation translaryngée par oxygène pulsé.

The use of emergency transtracheal jet ventilation in a 62 year-old female with laryngeal papillomatosis and respiratory distress is reported. Adequate ventilation of the lungs with an intermittent jet of oxygen under high pressure (5 bar) allowed anaesthesia and surgery to be carried out. Pathogenesis of the mediastinal and subcutaneous emphysema discovered at the end of the procedure is discussed.

[Development of blood sugar and insulinemia in the first 12 postoperative hours. Effects of glucose and insulin intake]. / Evolution de la glycémie et de l'insulinémie au cours des douze premières heures post-opératoires. Influence des apports de glucose et d'insuline.

Serum levels of glucose and insulin are studied during 12 hours in the early post-operative period after intra-abdominal surgery. Five groups of non diabetic patients are perfused with incremental doses of glucose, G. I: no glucose, G. II: 8,33 g . h-1 of glucose during 6 hours, G. III: 16,66 g . h-1 of glucose during 6 hours, G. IV: 16,66 g . h-1 of glucose with 20 mu insulin; G. V: 16,66 g . h-1 of glucose with 40 mu insulin. In all groups a significant rise in serum levels of glucose is observed (10,5-15,6 mmol . l-1). At the same time serum level of insulin remains unchanged except when insulin is infused. However exogenous insulin is unable to prevent the serum level of glucose to rise post-operatively.

[Curarization of the myasthenia patient by atracurium]. / Curarisation du patient myasthénique par l'atracurium. Atracurium in the myasthenic patient.

The use of atracurium, a new intermediate duration of action non depolarizing muscle relaxant, is described in a myasthenic patient undergoing abdominal surgery. The effective dose to 95% twitch suppression is 0.15 mg.kg-1. Following the first dose, the time from maximum twitch depression to 25% recovery is 32 min, and 33 min following the second dose. The recovery index (25-75% recovery time) and the 5-90% recovery time are respectively 33 and 83 min. The train-of-four ratio is greater than 0.7 within 90 min after the reinjection. The significance of the behaviour of atracurium is discussed. In reduced dosage and with careful neuromuscular monitoring, atracurium appears to be a reasonable and safe choice of myasthenic patients to provide surgical relaxation.

[Comparison in healthy volunteers of the systemic beta adrenergic receptor blockade by beta blockader eye drops]. / Comparaison chez le volontaire sain du blocage bêta-adrénergique systémique par les collyres bêta-bloquants.

The isoproterenol dose-response curve was used to assess quantitatively the degree of systemic beta-adrenoceptor blockade induced by metipranolol (Bétanol) and betaxolol (Bétoptic) eye drops. The study was carried out in twelve healthy volunteers, aged 22 +/- 1.4 yr. In a randomized double-blind trial, each volunteer received, on separate occasions at least one week apart, one drop in each eye of either placebo (physiological saline) or either of the ophthalmic beta-blockers. The intraocular pressure (Pio), heart rate (fc), arterial systolic (Pasys) and diastolic (Padia) pressures were measured before instillation of the eye drops after 15 to 30 min rest, and 3 h afterwards. The isoproterenol dose-response curve was studied 3 h after instillation of the drops. The CD25 (the amount of isoproterenol needed to increase fc by 25 b.min-1) was obtained by extrapolation on the least square linear regression curve. Both beta-blockers gave a significant fall in Pio compared with placebo, metipranolol more than betaxolol (p less than 0.02). There was also a significantly greater fall in fc with both metipranolol and betaxolol than with placebo. There were no changes in Pasys and Padia. CD25 was significantly increased with both beta-blocker eye drops as compared with placebo (p less than 0.05 for betaxolol; p less than 0.01 for metipranolol), but there was no difference between the two. Systemic absorption after topical application of ocular beta-blockers was thus confirmed for both metipranolol and betaxolol. However, the degree of beta-adrenoceptor blockade was weaker than that observed with other older ocular beta-blockers (timolol and carteolol).(ABSTRACT TRUNCATED AT 250 WORDS)

[Lyell syndrome after amoxicillin administration in a 2 year old child]. / Syndrome de Lyell consécutif à l'administration d'amoxicilline chez un enfant de 2 ans.

The authors report a toxic epidermal necrolysis (TEN) due to ampicillin (Agram) in a 2-year-old child. During the acute phase a septic syndrome occurred. The severity of the clinical and biological symptoms led to the administration of antibiotics, their systematic use remaining controversial. Recovery was favourable in a paediatric burn centre. Sequelae were minor. TEN, the physiopathological mechanism of which remaining still unknown, may carry a vital risk.

[Electroencephalographic study of pediatric anesthesia with intramuscular methohexital]. / Etude électroencéphalographique de l'anesthésie pédiatrique au méthohexital intramusculaire.

Intramuscular methohexital was used in pediatric anesthesia to carry out special investigations. There seemed to be few side effects but twitches or seizures have been reported. An electroencephalographic study was performed in normal children. The electroencephalogram showed periods of increased amplitude. The authors discussed the problem of side effects following the intramuscular administration of methohexital in the normal child, and prescribed its use in the epileptic.

[Postoperative respiratory complications of myotonia dystrophica (Steinert's disease)]. / Complications respiratories postopératoires de la myotonie dystrophique (maladie de Steinert).

Respiratory difficulties have long been recognized to be a major risk in patients with myotonia dystrophica, but postoperative pulmonary complications have only rarely been considered. Two cases of postoperative pulmonary complications which led to the patients's death stressed the severity and difficulty of treatment of these complications. A third case of postoperative respiratory failure revealed the underlying disease. These cases showed all the more the importance of preventing pulmonary complications. Pre-, per- and postoperative measures, chosen with respect to the severity of the myotonia and the seat of the surgical procedure, are suggested.

[Viral hepatitis B. Risk for the anesthetist]. / Hépatite virale B. Risque pour l'anesthésiste.

The risk of hepatitis B, previously reported in other countries, has never been investigated in French anaesthetic medical staff. The prevalence of hepatitis B viral markers has been calculated among the medical staff of the Department of Anaesthesiology, the hospital health care personnel, patients before surgical procedure and renal transplantation patients. The frequency in anaesthesiologists (18.75%; 12 out of 64) was significantly greater (p less than 0.05) than in health care personnel (10.5%; 91 out of 863). Prevalence increased with the length of practice in anaesthesiology. Prevalence of markers is 8.7% (27 out of 196) in patients undergoing surgery and 82% (27 out of 33) in patients operated on for renal transplantation in 1981. Frequency of carriers of the hepatitis B surface antigen is 0% in medical staff, 0.2% in health care personnel and 0.5% in patients before surgery. Among the health care staff, anaesthesiologists belong to a high risk population for hepatitis B. Prevention by administration of hepatitis B vaccine is recommended to protect the anaesthesiologist, his relatives and his patients.

[An original intubation technic in a child with Pierre Robin syndrome]. / Technique originale d'intubation chez un enfant porteur d'un syndrome de Pierre Robin.

Infants with Pierre Robin syndrome often present the anaesthesiologist with the challenge of upper airway obstruction and difficult tracheal intubation. An unconventional method for solving this problem was used in a 2 week old 2.2 kg term male infant who presented with severe micrognathia, a widely cleft palate and extreme glossoptosis. Hyperextension of the head in the prone position distracted the epiglottis from the glottis. Blind nasotracheal intubation was then used. The curve of the nasotracheal tube made it pass behind the epiglottis into the larynx.

[Effects of Diprivan on cerebral blood flow, intracranial pressure and cerebral metabolism in head injured patients]. / Effets du Diprivan sur le débit sanguin cérébral, la pression intracrânienne et l'activité métabolique cérébrale chez le traumatisé crânien.

The effects of propofol on cerebral blood flow, intracranial pressure (ICP) and cerebral oxygen consumption (CMRO2) were assessed in ten severely head-injured patients undergoing surgery for limb fractures. The patients, aged between 15 and 40 years, were in deep coma, scored 6-7 on the Glasgow coma score. They were mechanically ventilated and sedated with 1 mg.h-1 phenoperidine. Anaesthesia was carried out with a 2 mg.kg-1 intravenous bolus of propofol, immediately followed by a 150 micrograms.kg-1.min-1 infusion, which lasted for a mean time of 41.4 +/- 7.3 min. Data were collected 5 min before any propofol was given, 15 min after the start of the infusion, and 15 min after its end. A radial artery cannula, a 7.5 Fr thermodilution flow-directed pulmonary arterial catheter, a cerebral intraventricular catheter and a catheter in the jugular venous bulb were used for this purpose. Carotid arterial injection of 133Xenon was used to determine regional cerebral blood flow (rCBF). Anaesthetic blood concentrations of propofol (3 to 5 micrograms.ml-1) were associated with a decrease in all the parameters studied: cerebral perfusion pressure, from 82 +/- 14 mmHg to 59 +/- 7 mmHg (p less than 0.001); rCBF, from 35 +/- 6 ml.100 g-1.min-1 to 26 +/- 5 ml.100 g-1.min-1 (p less than 0.01); ICP from 11.3 +/- 2.6 mmHg to 9.2 +/- 2.5 mmHg (p less than 0.001); CMRO2 from 1.63 +/- 0.38 mlO2 +/- 100 g-1.min-1 to 1.18 +/- 0.38 mlO2.100 g-1.min-1 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of intravenous clonidine on postoperative shivering]. / Effets de la clonidine intraveineuse sur le frisson postanesthésique.

A study was designed to assess the possible effects of intravenous clonidine on postoperative shivering. Fifty patients undergoing spinal fusion under isoflurane anaesthesia were randomly assigned to two groups (n = 25). Patients in one group were given intravenous clonidine (5 micrograms.kg-1 during the first hour, and 0.3 microgram.kg-1.h-1 thereafter) or placebo. Shivering intensity (rated from 0 to 2) and pulmonary artery blood temperature (theta) was recorded every ten minutes for two hours. Haemodynamic and metabolic data were obtained by way of a Swan-Ganz catheter prior to administering the test drug, and then after 1 and 2 hours. On arrival at the recovery room, theta was 36.2 +/- 0.3 degrees C in the clonidine group, and 36.5 +/- 0.2 degrees C in the placebo group. There were no significant differences in shivering between the two groups. Clonidine significantly decreased blood pressure, heart rate, cardiac output and whole body oxygen consumption. The patients in these series were free from any cardiac disease. Further studies are required to assess the possible beneficial effects of clonidine on postoperative oxygen consumption in patients suffering from heart failure.

[Effect of propofol on left ventricular function in the coronary patient. Combined isotopic and hemodynamic studies]. / Impact du propofol sur la fonction ventriculaire gauche du coronarien. Etudes isotopique et hémodynamique couplées.

The present study investigated the effects of propofol (P) as sole anaesthetic agent of left ventricular (LV) function using gated radionuclide ventriculography (RNV) in unpremedicated patients with chronic coronary arterial disease (CAD). After informed consent, seven ASA 111 patients (51-74 yr) undergoing major urologic surgery took part in this study. All patients suffered from documented angina pectoris secondary to CAD. None gave a history of congestive heart failure or valvular heart disease. No patients were premedicated, but all received their chronic medications (nifedipine and isosorbide) up to and including the morning of surgery. The study was performed in the Nuclear Medicine Laboratory just before surgery. Heart rate (HR) was obtained from standard limb lead II of the ECG. A 7.5 F thermodilution Swan-Ganz catheter and a radial artery cannula were inserted under local anaesthesia. All patients were studied by RNV using red blood cells (RBC) labelled in vivo with 99m-technetium (Tc). A first RBC-Tc preparation containing 2-3 mCi f Tc was counted 10 cm from a gamma-camera. A first-pass study was carried out in the left anterior oblique position following the bolus i.v. injection of the source, allowing the evaluation of the isotopic dilution cardiac output (COiso) and the attenuation factor (F). Then, a second RBC-Tc preparation containing 20-25 mCi of Tc was injected intravenously. At equilibrium, 16 ECG-synchronized frames were acquired by computer for processing. Mean end-diastolic (ED) and end-systolic (ES) counts, left ventricular-end diastolic and systolic areas and ejection fraction (EF) were calculated every 1.5 min.(ABSTRACT TRUNCATED AT 250 WORDS)

[Hemodynamic monitoring in microneurosurgical excision by sub- and retro-sinus approach in seated position in acoustic neurinoma]. / Surveillance hémodynamique au cours de l'exérèse micro-neurochirurgicale par voie sous- et rétrosinusienne en position assise du neurinome de l'acoustique.

Haemodynamic data (thermodilution Swan-Ganz catheter and radial artery cannula) were collected in 17 patients (52.4 +/- 8 yr) during retrosigmoid approach for removal of an acoustic tumour in the seated position. Measurements were made before stimulation of posterior fossa structures (period 1) and during tumour dissection along the brain stem (period 2). Significant increases in systolic, diastolic and mean blood pressures, in pulmonary capillary wedge pressure, in cardiac index and in stroke index were observed during period 2, whereas heart rate, right atrial pressure and systemic vascular resistances were unaffected. The greater the size of the tumour and the difficulties in dissection, the greater were these intraoperative haemodynamic changes. In addition, the pulmonary arterial blood temperature and the noradrenaline plasma concentrations (double isotope enzymatic assay) increased significantly during period 2. In conclusion, the prolonged microsurgical technique of acoustic tumour dissection through the retrosigmoid approach may modify left ventricular loading conditions and may lead to pulmonary oedema, even if intravascular volume expansion was minimal and ventricular function was near normal.

[Halogenated inhalation anesthesia with a semiclosed circle system]. / Anesthésie halogénée utilisant un respirateur muni d'un circuit-filtre.

Thirty-six patients were anaesthetized for a maxillofacial surgical procedure. Ventilation was controlled by a ventilator (Kontron ABT 4100) with a semi-closed circle system. The flow of fresh gases was 1,200 ml.min-1. The vaporizer for the halogenated anaesthetic agent was placed out of the circle before the ventilator. Halothane was used for maintenance of anaesthesia and isoflurane for induced hypotension in orthognathic surgery. The inspired concentration of the halogenated agent was monitored by an analyser. A linear correlation between the delivered and the inhaled concentration of halogenated agent was established, the latter never reaching the delivered concentration. Monitoring the inspired oxygen concentration was required, so as to maintain a constant value. Carbon dioxide absorption by soda lime was also studied. The known advantages were: substantial economies in nitrous oxide and halogenated agents, prevention of contamination of the operating theatre, humidification and warning of the inspired gases. The use of such a system with the vaporizer out of the circle was safe, all the more so as the concentration of inhaled halogenated agents could be predicted.

[Anesthesia protocol in the swine. Effects of bleeding on circulation and acid-base equilibrium]. / Protocole d'anesthésie du porc. Effets de la saignée sur la circulation et l'équilibre acido-basique.

Haemodynamic parameters and their variations after the loss of 250 and 500 ml of blood under anaesthesia were studied in nine, 11 to 12 week-old, domestic swine weighing 37.4 +/- 2.6 kg. Premedication consisted of 2 ml azaperone i.m. Anaesthesia was induced with thiopentone, followed by suxamethonium to allow the easy placement of a cuffed endotracheal tube. Anaesthesia was maintained with phenoperidine and pancuronium. The animals were mechanically ventilated with a 50/50 nitrous oxide-oxygen mixture. A catheter was inserted in each of the femoral artery, upper hepatic vein, vena cava and portal vein. Right atrial, pulmonary and wedge pressures were measured; stroke volume, systemic and pulmonary resistances were calculated (fC 90 c X min-1, Pa 82 mmHg, Pra 4.7 mmHg, Ppa 24 mmHg, Ppw 11.6 mmHg, Q 4.45 l X min-1 and Rsa 1460 dyn X s X cm-5). The swine were then bled. After a bleed of 250 ml (t1), the haemodynamic parameters were significantly modified. After another bleed of 250 ml (t2), the heart rate only was significantly higher than at t1; but the blood transfusing could not re-establish a normal haemodynamic state. Blood samples were obtained to measure pH and total CO2 in a systemic artery, and the upper hepatic veins, vena cava and portal vein: the results suggested that the liver took part in the removal of acid metabolites.