Jean-Corentin Salengros

Different Anesthetic Techniques Associated with Different Incidences of Chronic Post-thoracotomy Pain: Low-Dose Remifentanil Plus Presurgical Epidural Analgesia is Preferable to High-Dose Remifentanil with Postsurgical Epidural Analgesia

OBJECTIVE To investigate the relationships between 2 anesthetic techniques, or the extent of allodynia around the surgical wound, and the occurrence of chronic post-thoracotomy pain. DESIGN Prospective, randomized study. SETTING A single-institution, university hospital. PARTICIPANTS Thirty-eight patients who underwent elective thoracotomy under general anesthesia. INTERVENTIONS High-dose remifentanil (average effect-site concentration 5.61 +/- 0.84 ng/mL) with epidural analgesia started and at the end of surgery or low-dose remifentanil (average effect site concentration 1.99 +/- 0.02 ng/mL) with epidural analgesia with 0.5% ropivacaine started at the beginning of anesthesia. MEASUREMENTS AND MAIN RESULTS Pain intensity and the extent of allodynia around the wound were measured during the hospital stay. The presence and intensity of residual pain were assessed 1, 3, and 6 months after surgery and at the end of the study (6-13 months, average 9 months). A DN4 neuropathic pain diagnostic questionnaire was conducted at the same times. In the high-dose group, the area with allodynia was three times larger than the area in the low-dose group. The increased allodynia was associated with a higher incidence of chronic pain (RR: 2.7-4.2) 3 and 6 months after surgery and at the end of the study (median follow-up: 9.5 months). CONCLUSIONS High-dose remifentanil (0.14-0.26 microg/kg/min) without epidural analgesia during surgery is associated with a large area of allodynia around the wound. These patients develop a much higher incidence of chronic pain than those receiving low-dose remifentanil with epidural analgesia during surgery.

Ketamine has no effect on bispectral index during stable propofol–remifentanil anaesthesia

BACKGROUND Ketamine 0.15-1 mg kg(-1) decreases postoperative morphine consumption, but 0.5 mg kg(-1) is associated with an increase in the bispectral index (BIS) values that can lead to an overdose of hypnotic agents. The purpose of our investigation was to study the effect of ketamine 0.2 mg kg(-1) administered over a 5 min period on the BIS during stable target-controlled infusion (TCI) propofol-remifentanil general anaesthesia. METHODS Thirty ASA I or II patients undergoing abdominal laparoscopic surgery were included in this double-blind, randomized study. Anaesthesia was induced and maintained with a TCI of propofol and remifentanil. After 5 min of steady-state anaesthesia (BIS at 40) without surgical stimulation, patients received either an infusion of ketamine 0.2 mg kg(-1) or normal saline. The test drug was infused over 5 min. Standard parameters and BIS values were recorded every minute until 15 min post-infusion. RESULTS The baseline mean (sd) value for the BIS was 37 (6.5) for the ketamine group and 39 (8.2) for the placebo group. The highest mean BIS value during the recording period was 41.5 (8.7) for the ketamine group and 40.1 (8.9) for the placebo group. BIS values were not statistically different between the groups (P=0.62); there was no significant change over time (P=0.65) with no group-time interaction (P=0.55). CONCLUSIONS Under stable propofol and remifentanil TCI anaesthesia, a slow bolus infusion of ketamine 0.2 mg kg(-1) administered over a 5 min period did not increase the BIS value over the next 15 min.

The anterior combined approach via a single skin injection site allows lower limb anesthesia in supine patients

PurposeLower limb anesthesia (LLA) requires the combination of, at least, three-in-one and sciatic nerve (SCN) blocks. Anterior approaches are easier to perform with minimal discomfort in supine patients, specially for traumatology. Feasibility of a single needle entry combined approach is reported.Clinical featuresThe combined landmark was applied in 119 ASA I and II patients (32–68 yr) scheduled for surgery below the knee. Needle (nerve stimulation applied through a single 150-mm long b-bevelled insulated needle) was inserted at the midpoint between the two classical approaches. Thirty and 15 mL of 0.5% ropivacaine were injected close to the femoral and the SCN, respectively. During the following 45 min, the extent of sensory block and knee and ankle motor block were assessed. Landmarks were determined within 1.7 min (0.7–2.2 min). The entire procedure was performed within 4.2 min (2.9–7.1 min) from the determination of the landmark to the SCN infiltration. The three-in-one technique was successful in 89.9% while SCN was successful in 94.9%. Femoral and tibial nerves were always blocked. Blockade of the posterior cutaneous femoral nerve was observed in 78% of patients. The extent and the quality of the sensory block always allowed surgery. Additional iv sedation was needed in 32.6% of patients. Motor block (adapted Bromage’s scale > 2) was observed in the femoral (98.3%), the obturator (84.8%), the tibial (97.4%) and the common peroneal (85.7%) nerve distributions. No important adverse effects were recorded.ConclusionThe anterior combined approach via a single needle entry represents a technically easy and reliable technique to perform LLA in the supine patient.RésuméObjectifL’anesthésie des membres inférieurs (AMI) exige la combinaison, au moins, d’un bloc trois-en-un et d’un bloc du nerf sciatique (NSC). L’abord antérieur est plus facile et n’entraîne qu’un inconfort minimal chez des patients en décubitus dorsal, surtout en traumatologie. Nous présentons l’application d’une technique combinée comportant un seul site d’injection.Éléments cliniquesLes repères combinés ont été utilisés chez 119 patients d’état physique ASA I et II, de 32 à 68 ans, devant subir une opération sous le genou. L’aiguille (stimulation nerveuse appliquée avec une aiguille isolée, biseautée, de 150 mm) a été insérée au centre des deux points d’abord habituels. Des doses de 30 et 15 mL de ropivacaïne à 0,5 % ont été respectivement injectées près du nerf fémoral et du NSC. Pendant les 45 min suivantes, l’étendue du bloc sensitifet du bloc moteur au genou et à la cheville a été évaluée. Les repères ont été déterminés en 1,7 min (0,7–2,2 min). L’application de la technique a demandé 4,2 min (2,9–7,1 min) à partir de l’identification du repère jusqu’à l’infiltration du NSC. La technique du troisen-un a été réussie dans 89,9 % des cas et celle du NSC dans 94 %. Les nerfs fémoral et tibial ont été aussi anesthésiés. Le bloc du nerf cutané fémoral postérieur a été observé chez 78 % des patients. L’étendue et la qualité du bloc sensitif ont permis l’opération dans tous les cas. Une sédation iv complémentaire a été nécessaire chez 32,6 % des patients. Le bloc moteur (échelle de Bromage > 2) a été observé pour les territoires des nerfs suivants : fémoral (98,3 %), obturateur (84,8 %), tibial (97,4 %) et sciatique poplité externe (85,7 %). Aucun effet indésirable important n’a été enregistré.ConclusionLa méthode antérieure combinée comportant un seul site d’injection est une technique facile et fiable pour réaliser une AMI chez le patient en décubitus dorsal.

Intraoperative somatosensory evoked potentials to facilitate peripheral nerve release

PurposeThe significance of intraoperative somatosensory evoked potentials (SSEP) monitoring is well known during spinal surgery. This technology could be beneficial during peripheral nerve surgery as well. In order to illustrate potential applications, two cases of successful peripheral nerve release demonstrated by on-line, intraoperative, SSEP are reported.Clinical and technical featuresThe first case presents a complex brachial plexus lesion involving two mixed sensorymotor nerves: median and ulnar. The second case involved an entrapment neuropathy of the lateral femoral cutaneous nerve, a pure sensory nerve (meralgia paresthetica). For each patient we elicited specific peripheral nerve SSEP (recorded using bipolar cephalic montage) by stimulating each nerve independently. In each case, during difficult nerve dissection and after having excluded other possible factors of intraoperative SSEP variations, an increase of the SSEP amplitude was observed, and later correlated with favourable patient clinical outcome.ConclusionsTw o cases demonstrate that intraoperative SSEP monitoring may provide an effective tool to guide surgical dissection during peripheral nerve release. This technique has potentially beneficial clinical applications and warrants further investigation.RésuméObjectifLa valeur du monitorage par les potentiels évoqués somesthésiques (PES) pendant une opération de la colonne vertébrale est bien connue. Il peut offrir des avantages pendant la chirurgie des nerfs périphériques. Pour illustrer ses applications possibles, nous présentons deux cas de libération réussie de nerfs périphériques démontrée par les PES peropératoires en ligne.Caractéristiques cliniques et techniquesLe premier cas concerne une lésion complexe du plexus brachial touchant deux nerfs mixtes sensori-moteurs: médian et cubital. Le second cas porte sur une neuropathie de compression du nerf cutané fémoral latéral, un nerf sensitif (méralgie paresthésique). Pour chaque patient, nous avons suscité les PES du nerf périphérique concerné (enregistrés selon un montage céphalique bipolaire) en stimulant chaque nerf séparément. Dans chaque cas, pendant la dissection difficile du nerf et aprs avoir exclu tout autre facteur possible de variation des PES peropératoires, une hausse de ľamplitude des PES a été observée et corrélée ensuite avec ľévolution clinique favorable du patient.ConclusionLes cas présentés montrent que le monitorage peropératoire par les PES peut guider efficacement la dissection chirurgicale pendant la libération ďun nerf périphérique. Il a des applications cliniques potentiellement bénéfiques et devrait être étudié plus avant.

Combined Ultrasound and Nerve Stimulation-Guided Thoracic Epidural Catheter Placement for Analgesia Following Anterior Spine Fusion in Scoliosis

Anterior spine fusion by thoracotomy is indicated for the treatment of idiopathic scoliosis. Although epidural (EP) analgesia represents the most effective way to provide adequate analgesia after thoracotomy, scoliosis patients have substantial anatomic variations that make EP catheter placement more difficult and often contraindicated. This case report describes a safe, effective technique for placing a thoracic EP catheter in a young patient undergoing anterior spine fusion surgery by thoracotomy. The procedure was guided by both ultrasound (US) and electrical stimulation of the Tuohy needle and catheter. The combination of US and nerve stimulation in this setting may be associated with easier, potentially safer, and more accurate insertion.

Myoglobinemia and propofol infusion.

Sir, We read with great interest the report by Betrosian et al. (1) regarding myoglobinemia during propofol infusion. We were nevertheless surprised by some facts related in the report. The authors describe a case of myoglobinemia attributed as a last resort to prolonged (> 48 h), high-dose (> 5 mg/kg/h) propofol infusion. Two things appear bizarre: first, we were amazed by the fact that a patient admitted to hospital after near drowning and long duration continuous cardiopulmonary resuscitation had creatinine phosphokinase serum levels within normal range. Second, we were also surprised by the fact that the essential witnessed sign of possible propofol toxicity was linked only to peripheral muscle necrosis (raised serum creatinine phosphokinase levels, myoglobinuria, raised serum myoglobin levels), with no acidosis and no increase in troponin levels. The exact mechanism involved in propofol infusion syndrome remains controversial. Nevertheless, some pathophysiological findings related to propofol infusion in the critically ill patient are known but probably only to some extend (2). The role of propofol in cardiac and peripheral muscle injury is probably twofold: first, propofol demonstrated direct mitochondrial inhibitory effects by impairing oxygen utilization and inhibiting electron flow along the mitochondrial electron transport chain. Second, propofol is also indirectly responsible for impaired fatty acid oxidation at the level of the mitochondria. Indeed, in critical conditions, free fatty acids derived from lipolysis of adipose tissues are the most important fuel for cardiac or peripheral muscle cells. Some metabolic findings derived from a paediatric case reported previously (3) tend to indicate that propofol causes an inhibition of the carnitine palmitoyl transferase 1 therefore blocking the entry of long-chain free fatty acids into the mitochondria, but is also responsible for b-spiral oxidation and respiratory chain uncoupling at complex II causing in fine an imbalance between energy demand and supply in the cell leading to widespread (peripheral and cardiac) muscle necrosis. What’s more, in the literature, there seem to exist a trend toward metabolic lactic acidosis as a possible early sign of muscle suffering (4, 5). This lactic acidosis could sign off energy imbalance in cardiac and peripheral muscle due to propofol toxicity. This is why we have trouble in understanding how the patient described in the report did not show signs of cardiac myotoxicity (raised troponin levels), nor did he show signs of acidosis (no report of serum pH but serum lactates within normal range). How can we imagine that peripheral muscle cells mitochondria could be so deprived in energy as to lead to their lysis without causing significant acidosis from lactic acid production? Furthermore, why would only peripheral muscle cells, and not myocardial cells, also suffer from propofol mitochondrial toxicity. Propofol infusion syndrome remains a little-known entity, maybe the case described was a variant from the classic syndrome, affecting only peripheral muscle, or maybe it was not propofol infusion syndrome at all. There remains much to learn about this particular ‘disease’.

Somatosensory evoked potentials as an objective assessment of the sensory median nerve blockade after infraclavicular block

PurposeMedian nerve somatosensory evoked responses (MnSSER) alterations were compared to clinical tests (cold and pinprick) variations, in 20 ASA I adult patients following infraclavicular block obtained with 40 mL ropivacaine 0.5% to assess first, the difference of time course of the respective electrophysiological and clinical signs, and second, the objectivity and the reproducibility of MnSSER changes.Clinical featuresFour MnSSER derivations (Erb’s point; cutaneous projection of peripheral end of brachial plexus; posterior neck at C6 level, frontal and controlateral parietal scalp) were monitored and recorded for retrospective analysis. Continuous data acquisition were started before ropivacaine injection (baseline) and maintained for 30 min thereafter. Every three minutes after ropivacaine injection, cold and pinprick tests were performed in the hand median nerve cutaneous supply zone and were assessed using a sensory visual score (varying from 0–10). Data were compared using analysis of variance. Although MnSSER values were stable during baseline period, after ropivacaine administration, severe progressive amplitude depressions of selected MnSSER were detected in every patient. While clinical cold and pinprick tests became positive (score > 8) only 15.8 ± 1.2 min and 20.1 ± 1.8 min respectively after ropivacaine administration, the mean time to observe the earliest MnSSER 20% amplitude decrease at Erb’s point derivation was reduced to 5.6 ± 1.1 min (P < 0.01).ConclusionSelected MnSSER amplitude reduction indicates objectively the onset of median nerve anesthesia following infraclavicular brachial plexus block before the appearance of clinical signs.RésuméObjectifLes modifications des potentiels évoqués somesthésiques du nerf médian (PESNM) induit par un block infraclaviculaire (40 mL de ropivacaine 0,5 %) on été comparés avec les tests cliniques usuels (tests au froid et à la piqûre) chez 20 patients adultes ASA I afin ďévaluer la différence ďévolution et de survenue des signes électrophysiologiques et cliniques, ľobjectivité et la reproductibilité des modifications des PESNM et finalement le possible intérêt en pratique clinique.Eléments cliniquesLes PESMN étaient enregistrés en continu au point ďErb (projection cutanée de ľextrémité latérale du plexus brachial) et successivement au niveau cervical en regard de la sixime vertèbre), frontal et pariétal controlatéral pour une comparaison secondaire. Ľenregistrement a commencé avant ľinjection de ropivacaine et jusqu’à 30 min après. Toutes les trois minutes après la réalisation du bloc, les tests cliniques étaient réalisés au niveau de la main ďinnervation du nerf médian en utilisant une échelle visuelle analogique (0–10). Une analyse de variance a été utilisée pour comparer les résultats. Si les PESNM étaient remarquablement stables avant la réalisation du bloc, après leur amplitude diminue précocement et de fa÷on importante, chez tous les sujets. Alors que les tests au froid et à la piqûre peuvent être considérés comme positifs (> 8 sur ľéchelle) seulement après 15,8 ± 1,2 min et 20,1 ± 1,8 min respectivement après ľinjection de ropivacaêne, la diminution la plus précocement détectable de ľamplitude du potentiel (20 %) au point ďErb, survenait en moyenne en 5,6 ± 1,1 min (P < 0,01).ConclusionLa diminution de ľamplitude des PESNM indique objectivement la survenue du bloc du nerf médian après la réalisation ďun bloc infraclaviculaire avant toute modification clinique.