Jean-Pierre Tétrault

Axillary plexus block using a peripheral nerve stimulator: single or multiple injections

This prospective, randomized, double-blind study was undertaken to evaluate the success rates of axillary brachial plexus block performed with the help of a peripheral nerve stimulator when either one, two or four of the major nerves of the brachial plexus were located. Seventy-five patients undergoing upper limb surgery were randomly allocated to one of the following five groups according to the nerve and number of nerves to be located; G-1: musculo-cutaneous, radial, median and ulnar nerves; G-2: musculo-cutaneous plus one of the other three nerves; G-3: radial nerve; G-4: median nerve; G-5: ulnar nerve. The sensory block was evaluated before surgery and cutaneous anaesthesia was considered to be present when the needles of a Wartenberg Pinwheel were no longer felt in all the dermatomes of the nerves implicated in the surgical site. Otherwise, the block was considered to need completion before surgery. Only one out of the 15 patients in G-1 and G-2 needed completion of their block before surgery whereas seven out of 15 for G-3 and eight out of 15 for G-4 and G-5 needed completion of their block (P < 0.01). We conclude that when performing an axillary block with the help of a peripheral nerve stimulator, stimulation of the musculo-cutaneous nerve and one other nerve or stimulation of all four major nerves of the brachial plexus gives a higher success rate than stimulation of only one nerve, whether the stimulated nerve is the median, radial or ulnar.RésuméLa présente étude en est une prospective, avec distribution au hasard, et à double insu. Elle avait pour but d’évaluer l’influence du nombre et de la nature des nerfs stimulés lorsque le bloc du plexus brachial est réalisé par approche axillaire à l’aide d’une technique de neurostimulation. Soixante et quinze patients soumis à une chirurgie du membre supérieur ont été distribués de façon aléatoire dans l’un des cinq groupes suivants selon le nerf et le nombre de nerfs localisés par neurostimulation; G-1: nerfs musculo-cutané, radial, médian et cubital; G-2: nerfs musculo-cutané, et l’un des trois autres nerfs majeurs du plexus brachial (médian, radial ou cubital); G-3: nerf radial; G-4: nerf median; G-5: nerf cubital. Le bloc sensitif a été évalué avant la chirurgie et une anesthésie cutanée était considérée présente quand les aiguilles d’une roulette de Wartenburg n ’étaient plus perçues dans tous les territoires cutanés des nerfs impliqués dans le site chirurgical. Sinon, le bloc a été considéré comme devant être complété. Un seul patient sur 15 dans les G-1 et 2 a necessite un complément de son bloc avant la chirurgie, alors que sept patients sur 15 dans le G-3 et huit sur 15 dans les G-4 et 5 ont necessite un tel complement avant la chirurgie (P < 0.01). Nous concluons que lorsque nous réalisons un bloc axillaire avec l’aide d’un stimulateur nerveux périphérique, la stimulation du nerf musculo-cutané et de l’un des trois autres nerfs majeurs du plexus brachial, ou la stimulation des quatre principaux nerfs du plexus brachial conduisent à un taux de réussite plus élevé que la stimulation d’un seul nerf que ce soit le médian, le radial ou le cubital.

Epidural morphine for postoperative pain relief: a dose-response curve.

Different doses of epidural morphine were studied in order to determine their effectiveness in providing postoperative pain relief after surgery of the lower extremities and their relationship to the incidence of untoward reactions. The study was carried out in a double-blind fashion using five dosages of epidural morphine (0.5, 1.0, 2.0, 4.0, and 8.0 mg) and included 60 patients. The higher doses of morphine (2.0, 4.0, and 8.0 mg) were equally effective and more effective than the lowe: doses (0.5 and 1.0 mg) in providing postoperative analgesia. Nausea and vomiting were encountered more frequently with the highest dose (8.0 mg) and this finding was statistically significant (P < 0.03). No statistically significant difference was found between the doses studied with regard to itching, urinary retention, and respiratory depression; the latter was evaluated in a subgroup of 20 patients. These data suggest that effective postoperative pain relief after surgery of the lower extremities can be achieved with relatively low doses of morphine sulfate and with minimal side effects. For the type of surgery studied, 2 mg morphine sulfate appeared to be the optimum dose.

Sleep quality in mechanically ventilated patients: comparison between NAVA and PSV modes

BackgroundMechanical ventilation seems to occupy a major source in alteration in the quality and quantity of sleep among patients in intensive care. Quality of sleep is negatively affected with frequent patient-ventilator asynchronies and more specifically with modes of ventilation. The quality of sleep among ventilated patients seems to be related in part to the alteration between the capacities of the ventilator to meet patient demand. The objective of this study was to compare the impact of two modes of ventilation and patient-ventilator interaction on sleep architecture.MethodsProspective, comparative crossover study in 14 conscious, nonsedated, mechanically ventilated adults, during weaning in a university hospital medical intensive care unit. Patients were successively ventilated in a random ordered cross-over sequence with neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV). Sleep polysomnography was performed during four 4-hour periods, two with each mode in random order.ResultsThe tracings of the flow, airway pressure, and electrical activity of the diaphragm were used to diagnose central apneas and ineffective efforts. The main abnormalities were a low percentage of rapid eye movement (REM) sleep, for a median (25th-75th percentiles) of 11.5% (range, 8-20%) of total sleep, and a highly fragmented sleep with 25 arousals and awakenings per hour of sleep. Proportions of REM sleep duration were different in the two ventilatory modes (4.5% (range, 3-11%) in PSV and 16.5% (range, 13-29%) during NAVA (p = 0.001)), as well as the fragmentation index, with 40 ± 20 arousals and awakenings per hour in PSV and 16 ± 9 during NAVA (p = 0.001). There were large differences in ineffective efforts (24 ± 23 per hour of sleep in PSV, and 0 during NAVA) and episodes of central apnea (10.5 ± 11 in PSV vs. 0 during NAVA). Minute ventilation was similar in both modes.ConclusionsNAVA improves the quality of sleep over PSV in terms of REM sleep, fragmentation index, and ineffective efforts in a nonsedated adult population.

Duration of decubitus position after epidural blood patch

Thirty patients presenting with post-dural puncture headache (PDPH) were prospectively studied to determine the influence of the duration of the decubitus position after epidural blood patch on the efficacy of treatment. All patients received 12 ml of autologous blood. They were randomly distributed into three groups of ten patients. Patients in Group 1 were maintained in a decubitus position for 30 min after the epidural injection of autologous blood in the epidural space. Patients in Group 2 were maintained for 60 min in decubitus and patients in Group 3 for 120 min. Post-dural puncture headache was evaluated using a visual analogue scale before the epidural blood patch, at the time of initially adopting a standing position after the blood patch, and 24 hr later. The severity of PDPH in the three groups was reduced at the time of initially adopting a standing position and after 24 hr, in comparison with pre-blood patch VAS (P < 0.001). Patients in Group 3 presented less severe PDPH than patients in Group 1 at the time of initially standing up and 24 hr later (P < 0.05). We conclude that epidural blood patch was effective in treating PDPH but that the maintenance of a decubitus position for at least one hour and preferably for two hours after the blood patch was more effective than maintenance for 30 min.RésuméTrente patients qui présentaient des céphalées après une perforation de la dure-mère ont été étudiés de façon prospective. L’influence de la durée du decubitus après l’injection de sang autologue dans l’espace épidural sur l’efficacité du traitement a été évaluée. Tous les patients ont reçu 12 ml de sang autologue dans l’espace epidural. Ils ont été répartis au hasard en trois groupes de dix patients chacun. Les patients du groupe 1 ont maintenu une position décubitus pendant 30 min après le traitement. Les patients du groupe 2 ont maintenu cette position pendant 60 min et ceux du groupe 3, 120 min. L’intensité de la céphalée était évaluée au moyen d’une échelle visuelle analogue avant le traitement, au moment du lever, et 24 heures après le traitement. Les patients des trois groupes ont vu leurs céphalées diminuer de façon significative au moment du lever ainsi que 24 heures après l’injection de sang autologue dans l’espace épidural (P < 0.001). Les patients du groupe 3 présentaient cependant des céphalées moins importantes que les patients du groupe 1 au lever (P < 0.05) et 24 heures plus tard (P < 0.05). Nous concluons que le maintien d’une position de décubitus pendant au moins une heure et préférablement deux heures après l’injection de sang autologue dans l’espace épidural donne de meilleurs résultats que le maintien de cette position pendant seulement 30 minutes.

A Prospective Comparative Study of Two Indirect Methods for Confirming the Localization of an Epidural Catheter for Postoperative Analgesia

We prospectively evaluated, in randomized order, 2 indirect methods of confirming the localization of an epidural catheter for postoperative analgesia in 218 surgical patients: epidural stimulation test (EST) and epidural pressure waveform analysis (EPWA). The epidural space was localized by using a loss of resistance technique. All catheters were inserted 5 cm into the epidural space and primed with 5 mL of 0.9% normal saline. There were no differences between the methods: the positive predictive value and specificity were high (100% in both groups), but the sensitivity was moderate (80% for EST and 81% for EPWA) and the negative predictive value was low (16% for EST and 17% for EPWA). Combining both methods yielded better sensitivity (97%) and negative predictive value (57%) (P < 0.001). The sensitivity of EST was increased to 87% (P < 0.05) if sensory response was included as well as motor response for stimulation less than 10 mA. We suggest the inclusion of sensory response in the appropriate dermatome at a current <10 mA as a criterion for adequate epidural catheter localization for EST testing. EPWA sensitivity was significantly better with older patients: 94% for patients older than 80 yr compared with 63% for patients younger than 40, 73% for patients 40 to 60, and 85% for patients aged 60 to 80 yr (P = 0.03). We conclude that the two tests are comparable for confirming catheter placement.

Clinical, electrical and mechanical correlations during recovery from neuromuscular blockade with vecuronium

In order to détérmine correlations between electromyographic (EMG), mecanomyographic (MMG) and clinical criteria of adequate recovery from neuromuscular blockade with vecuronium, seven young healthy conscious volunteers were given subparalysing doses of vecuronium. During recovery from neuromuscular blockade, vital capacity, negative inspiratory pressure, peak expiratory flow rate and five-second head lift were assessed. Neuromuscular monitoring included the evoked EMG response of the adductor digiti minimi and the simultaneous evoked MMG response of the adductor pollicis on the same side. We found that all subjects maintained head lift for five seconds at EMG T4T1 of 0.70, and they achieved normal respiratory tests at EMG T4/T1 of 0.90. The MMG T4/T1 needed for the subjects to perform normal respiratory tests was found to be 0.50, at which time six of the seven subjects were able to perform adequately the head lift test.RésuméLa correlation entre l’électromyographie (EMG), la mécano-myographie (MMG) et des critères cliniques de récuperation adéquate suite à l’administration de doses sous-paralytisantes de vécuronium a été étudiée chez sept jeunes volontaires sains. Pendant la phase de récupération du bloc neuromusculaire, la capacité vitale, la force inspiratoire, le débit expiratoire de pointe et la capacité de maintien de la tête soulevée pour cinq secondes ont été évalués. Le monitorage neuromusculaire comprenait au niveau d’un même membre supérieur un EMG de l’adductor digiti minimi et un MMG de l’adductor pollicis. En ce qui a trait à l’EMG, tous les sujets ont réussi l’épreuve du maintien de la tête soulevée pour cinq secondes lorsque le rapport T4/T1 était de 0,70 et les tests de fonction respiratoire se sont avérés dans les limites normales lorsque le rapport T4/T1 était revenu à 0,90. Quant au MMG, six des sept sujets ont réussi le test du maintien de la tête soulevée pour cinq secondes lorsque le rapport T4/T1 etait de 0,50, alors que tous les tests de fonction respiratoire étaient revenus à la normale à ce momentlà.

Onset of spinal block is more rapid with isobaric than hyperbaric bupivacaine.

PurposeTo compare isobaric with hyperbaric 9.75 mg bupivacaine injected intrathecally, and to evaluate the effects of subsequent injection of lidocaine 2% into the epidural space.MethodsPatients in group 1 (n = 30) received isobaric 9.75 mg bupivacaine and in group 2 (n = 30) hyperbaric 9.75 mg bupivacaine injected into the subarachnoid space in a combined spinal-epidural technique. They were undergoing urological, gynecological, orthopedic, gastro-intestinal or vascular surgery. Using a double blind technique, the followings parameters were measured: cutaneous analgesia to pinprick, motor blockade, time for two segment regression, time for complete regression of the motor block, quality of anesthesia. In 12 patients the effect of epidural injections of 3 ml lidocaine 2% was observed.ResultsMotor and sensory block developed more rapidly (five minutes) in the isobaric group (P < 0.05). Maximum upper level (T7 ± 2 ), two-segment regression (52 min in both groups), motor recovery (160vs 157 min), and quality of anesthesia did not differ between the two groups. Thirty nine epidural injections of 3 ml lidocaine 2% were given in 12 patients 10 min after spinal injection, 28 were in the hyperbaric group (P < 0.05). Twenty six of the epidural injections produced an increase in sensory block of 0 or 1 dermatome, and 13, of 2 or more.ConclusionThe block developed more rapidly in the isobaric group, but both isobaric and hyperbaric 9.75 mg bupivacaine produced adequate upper levels of analgesia for surgery. The effect of epidural injections of 3 ml lidocaine 2% was usually minimal.RésuméObjectifComparer 9,75 mg de bupivacaine isobare et hyperbare injectés en sous-arachnoïdien, et évaluer l’effet, quand nécessaire, de la lidocaïne 2 % injectée subséquemment dans l’espace épidural.MéthodeLes patients du groupe 1 (n = 30) ont reçu 9,75 mg de bupivacaïne isobare et ceux du groupe 2 (n = 30) 9,75 mg de bupivacaïne hyperbare en injection sous-arachnoïdienne selon une technique combinée rachi-épidurale. Des interventions chirurgicales urologiques, gynécologiques, orthopédiques, gastro-intestinales et vasculaires ont été faites. En utilisant une technique de double insu, on a mesuré les paramètres suivants : analgésie cutanée à la piqûre, bloc moteur, temps de régression de 2 niveaux, temps de régression complète du bloc moteur, qualité d’anesthésie. Chez 12 patients qui ont eu besoin d’injections épidurales de 3 ml de lidocaïne 2 %, l’effet de l’injection a été observé.RésultatsLes blocs moteur et sensitif se sont développés plus rapidement (5 min) dans le groupe isobare (P < 0,05). Les niveaux supérieurs d’analgésie (D7 ± 2), les temps de régression de 2 segments (52 min), la récupération motrice ( 160vs 157 min), et la qualité de l’anesthésie ont été similaires. Trente-neuf injections épidurales de 3 ml de lidocaïne 2 % ont été faites chez 12 patients, 10 min après l’injection sous-arachnoïdienne. Vingthuit des réinjections l’ont été dans le groupe hyperbare (P < 0,05); vingt-six ont produit une augmentation de 0 ou 1 dermatome, et 13 de 2 ou plus.ConclusionLe bloc s’est développé plus rapidement, de 5 min, dans le groupe bupivacaïne isobare, mais 9,75 mg de bupivacaïne isobare ou hyperbare ont produit des niveaux d’analgésie supérieurs adéquats pour l’opération. L’effet d’injections épidurales de 3 ml de lidocaïne 2% est le plus souvent minime.

The SiBI connector: a new medical device to facilitate preoxygenation and reduce waste anesthetic gases during inhaled induction with sevoflurane.

Implications The SiBI™ connector is a new medical device used for vital capacity inhaled induction with sevoflurane. It allows efficient preoxygenation of patients and reduces waste anesthetic gases in the operation room during induction.

Effect of Ventilatory Variability on Occurrence of Central Apneas

OBJECTIVE: To compare the influence of 2 ventilation strategies on the occurrence of central apneas. METHODS: This was a prospective, comparative, crossover study with 14 unsedated subjects undergoing weaning from mechanical ventilation in the medical ICU of Hôpital du Sacré-Cœur, Montréal, Québec, Canada. The subjects were ventilated alternately in neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV) modes. Inspiratory flow/time and pressure/time waveforms and diaphragmatic electrical activity were used to detect central apneas. Ventilatory variability and breathing pattern were evaluated in both modes. Breathing patterns just before central apneas, and associations between apneas and sleep patterns (electroencephalogram) were studied. RESULTS: Switching from PSV to NAVA did not change mean minute ventilation, tidal volume, or breathing frequency. However, tidal volume variability, defined as the coefficient of variability (standard error/mean), was significantly greater with NAVA than with PSV (17.2 ± 8 vs 10.3 ± 4, P = .045). NAVA induced a greater decrease in central apneas, compared to PSV (to 0 with NAVA vs 10.5 ± 11 with PSV, P = .005). Central apneas during PSV were detected only during non-rapid-eye-movement sleep. CONCLUSIONS: NAVA was associated with increased ventilatory variability, compared to constant-level PSV. With NAVA the absence of over-assistance during sleep coincided with absence of central apneas, suggesting that load capacity and/or neuromechanical coupling were improved by NAVA and that this improvement decreased or abolished central apneas.

Neuromuscular monitoring: does it make a difference?

PurposeThe objective of the present prospective study was to evaluate the influence of neuromuscular monitoring. on the level of neuromuscular blockade from induction of anaesthesia until extubdtion of the trachea.MethodsForty-two patients aged between 18 and 73 yr undergoing a range of surgical procedures under general anaesthesia were randomly distributed into two groups of 21 patients each. In both groups a Datex NMT Monitor® was used and electromyographic responses of the the ulnar muscles to supramaximal stimulation of the ulnar nerve were recorded. In Group 1, the anaesthetist could see the movements of the stimulated hand, but not the monitor. In Group 2, the anaesthetist could see neither the stimulated hand nor the monitor. The same anaesthetist administered the neuromuscular relaxants which were succinylcholine 1.5 mg · kg−1 for trachéal intubation and vecuronium 0.1 mg· kg−1 for neuromuscular relaxation during surgery, followed by 1 to 2 mg maintenance injections. Possible residual curarization was evaluated in the recovery room by head lift tests and pulse oximetry.ResultsPatients in Group 1 had deeper neuromuscular block throughout surgery, despite the use of a comparable dose of vecuronium (10.1 mg for G1 vs 11.2 mg for G2). The EMG values of T1 and train-of-four values were not different at trachéal intubation or at extubation. No patients presented signs of residual curarization in the recovery room.ConclusionThe study demonstrates that with the same amount of vecuronium the neuromuscular relaxation was deeper with the use of a simple neuromuscular monitoring (visual evaluation of the thumb movements). Despite the deeper neuromuscular block in the monitored group, there was no residual curarization in the recovery room.RésuméObjectifLe but de la présente étude était d’évaluer l’influence de l’utilisation d’un monitorage de curarisation sur le niveau de curarisation et ce, de l’induction de l’anesthésie jusqu ’à l’extubation de la trachée.MéthodeQuarante-deux patients âgés de 18 à 73 ans prévus pour différentes chirurgies sous anesthésie générale ont été répartis au hasard en deux groupes de 21 patients. Dans les deux groupes un moniteur Datex NMT® a été utilisé et les réponses électromyographiques des muscles de l’éminence thénar suite à une stimulation supramaximale de nerf cubital ont été enregistrées. Dans le groupe I, l’anesthésiste pouvait voir la main stimulée mais non le moniteur. Dans le groupe 2, l’anesthésiste ne pouvait voir ni la main ni le moniteur. Le même anesthésiste a donné les curares qui étaient de la succinylcholine à 1.5 mg· kg−1 pour l’intubation endotrachéale et du vécuronium à 0.1 mg· kg−1 pour la relaxation neuromusculaire pendant la chirurgie, dose qui était suivie de réinjections de maintien de 1 à 2 mg. Une curarisation résiduelle possible a été évaluée en salle de réveil par les valeurs de saturation et des tests de soutien de la tête.RésultatsLes patients du groupe 1 ont montré des niveaux de curarisation plus profonds tout au long de la chirurgie, et ceci malgré l’utilisation de doses comparables de vécuronium (10.1 mg pour le G1 et 11.2 mg pour le G2). Les valeurs du T1 de l’EMG et du train-de-quatre n’étaient pas différentes lors de l’intubation endotrachéale et de l’extubation. Aucun patient n’a présenté de signes de curarisation résiduelle en salle de réveil.ConclusionCette étude montre qu’avec une même quantité de vécuronium la relaxation neuromusculaire est plus importante lorsqu’il y a utilisation d’un monitorage neuromusculaire simple (évaluation visuelle des mouvements du pouce). Également, en dépit d’un bloc neuromusculaire plus profond dans le groupe avec moniteur, il n’y a pas eu de curarisation résiduelle dans ce groupe en salle de réveil.