Dermot J. Kelly

Neuroleptic malignant syndrome and mivacurium: a safe alternative to succinylcholine?

Neuroleptic malignant syndrome (NMS) and malignant hyperthermia (MH) may have a common pathogenic mechanism; therefore, it has been suggested that known triggering agents for MH (such as succinylcholine) should be avoided in patients with NMS. Electroconvulsive therapy (ECT) continues to play a major therapeutic role in contemporary psychiatry, and succinylcholine has been the muscle relaxant of choice in attenuating violent muscle contractions induced by ECT. Mivacurium is a nondepolarizing muscle relaxant with a relatively rapid onset and a short duration of action, and to date it has been proved safe in MH- susceptible patients. In this case report, following succinylcholine use during ECT, a patient with NMS developed an increase in temperature and serum creatine kinase (CK) level, possibly due to an MH reaction. Since the patient’s mental status necessitated further ECT, mivacurium was administered during subsequent treatments and resulted in effective attenuation of muscle contractions without elevation of patient temperature or CK levels. In addition, there was no marked prolongation of the anaesthetic. Mivacurium is a suitable agent for patients with NMS undergoing ECT, as it has not been associated with precipitation of an MH response.RésuméLe syndrome malin des neuroleptiques (SMN) et l’hyperthermie maligne (HM) semblent avoir une mécanisme pathogène commun; c’est pourquoi on a suggéré d’éviter dans le SMN les agents qui déclenchent l’HM (ex., la succinylcholine). L’électroconvulsivothérapie (ECT) continue de jouer un rôle majeur en pyschiatrie et la succinylcholine est présentement le myorelaxant de choix pour atténuer les violentes contractions musculaires induites par l’ECT. Le mivacurium est un myorelaxant non dépolarisant dont le début d’action est relativement rapide et la durée d’action courte, et jusqu’ à maintenant, on a jugé qu’il ne présentait aucun danger pour les patients susceptibles à l’HM. Dans le cas présent, à la suite de l’administration de succinylcholine pour un ECT, un patient porteur du SMN a présenté une élévation de température et de la concentration de la créatine kinase sérique (CK), peutêtre par réaction d’HM. Comme son état nécessitait des traitements additionels d’ECT, le mivacurium a été administré au cours des traitements ultérieurs et a atténué les contractions musculaires sans élévation de température ou des concentrations de CK. Il n’a pas eu non plus de prolongation appréciable de l’anesthésie. Le mivacurium est un agent approprié pour le SMN et il n’est pas associé au déclenchement de l’HM.

Dilutional hyponatremia during endoscopic curettage : the female TURP syndrome ?

In 1910, Jacobaeus described the application of endoscopy to inspect the peritoneum, pleura, and pericardium (1). Since that time, gynecologists have developed the instrumentation, operative principles, and techniques of laparoscopic surgery. Recently, reports of laparoscopic techniques have been described not only for cholecystectomy and gynecologic surgery, but also for appendectomy (21, inguinal hernia repair (31, nephrectomy (4), splenectomy (5), and hemicolectomy (6). In 1967, Steptoe (7) published the technique of laparoscopic surgery in gynecologic practice. The technique (using a urologic resectoscope) has been adopted widely by practitioners and has been modified to suit several different surgical procedures. Two of the most frequent surgical complications associated with gynecologic laparoscopic surgery are bleeding and viscus perforation. Although hyponatremia is a well recognized complication of transurethral prostatectomy (TURP), we report the occurrence of this complication in a female patient undergoing endoscopic uterine surgery. Since the frequency of laparoscopic surgery continues to increase, and relatively few cases of dilutional hyponatremia during endoscopic surgery have been published (8–10), we present this case to emphasize the potential for this complication and the paucity of currently available monitoring techniques.

Airway obstruction due to a sengstaken-blakemore tube

B leeding from ruptured esophageal varices is a serious complication of portal hypertension, which is itself one of the sequelae of hepatic cirrhosis. Bleeding from varices occurs in approximately 30% of cirrhotic patients over a 21-mo period, with a bleeding related mortality of 50% (1). Treatment options for acute variceal hemorrhage include conservative management, vasoactive drugs, local endoscopic therapy, a definitive surgical procedure, or balloon tamponade. Anesthetic management may be complicated by the presence of circulatory shock, liver failure, or coagulopathy. In addition, balloon tamponade may make endotracheal intubation difficult and/or impair ventilation. We report a case in which an incorrectly positioned Sengstaken-Blakemore tube (SBT) compromised ventilation by causing extrinsic compression of the trachea.

The effects of midazolam on pure tone audiometry, speech audiometry, and audiological reaction times in human volunteers

UNLABELLED Auditory evoked potentials are effected by benzodiazepines, as is cortical processing of auditory stimuli. The effect of benzodiazepines on auditory sensitivity has not, however, been studied. We designed the present study to investigate the effect of sedative doses of midazolam on pure tone and speech audiometry and on audiological reaction times in healthy volunteers. Thirty volunteers underwent baseline audiological assessment for pure tones and speech and had their audiological reaction times measured at 10 and 50 dB above their threshold hearing level at a frequency of 1 kHz. Subjects were then randomly assigned to one of two groups. Group A (n = 15) received midazolam (0.04 mg/kg) IV, and Group B (n = 15) received a similar volume of placebo IV. The audiological tests were repeated 5 min later, and performance was compared with baseline data. Scheffé post hoc tests were used to assess the significance of changes in each group. There was no pre- to posttest change in audiological performance in either the placebo group (P = 0.194) or the midazolam group (P = 0.957). Speech audiometry performance was likewise unaffected by midazolam (P = 0.154). Reaction time at the 10-dB and 50-dB sensation levels were both significantly prolonged after midazolam administration (P = 0.023 and P = 0.012, respectively). In this study, we demonstrate that sedation with midazolam (0.04 mg/kg) does not alter pure tone or speech audiometric thresholds, but it does significantly delay the reaction time to auditory stimuli. Medical practitioners should advise midazolam-sedated patients of their impaired reaction to auditory warning signals (e.g., traffic and car horns) as part of the day-ward discharge recommendations. IMPLICATIONS In this study, we demonstrate that sedation of healthy volunteers with the benzodiazepine midazolam, in the common clinical dosage, does not affect their hearing capability as measured by pure tone and speech audiometry. However, ones ability to react to auditory signals is impaired after midazolam, which may have implications for patients after day-case procedures.

Early neuromuscular recovery characteristics following administration of mivacurium plus vecuronium

PurposeThis study was designed to describe the early recovery characteristics, as well as the speed of onset of neuromuscular block, after a combination of mivacurium and vecuronium.MethodsIn this controlled, randomized study, 30 consenting ASA I–III patients were assigned to three treatment groups. The “2M2V” group received twice the dose necessary to cause 95% depression of the evoked twitch response (2 × ED95) of mivacurium (0.15 mg · kg−1) plus 2 × ED95 of vecuronium (0.1 mg · kg−1); the “2V” group received 2 × ED95 of vecuronium; and the “4V” group received 4 × ED95 of vecuronium. Evoked neuromuscular responses of the adductor pollicis were assessed with an adductor pollicis force transducer. The time until maximum block and times to 10% and 25% recovery (T10 and T25) in each group were expressed as mean ± standard deviation and compared using ANOVA.ResultsOnset of block in the 2M2V group was 27% faster than in the 2V group (2.0 ± 0.6 vs. 2.7 ± 0.8 min respectively, P < 0.05) and was similar to the 4V group (1.95 ± 0.3 min, P = NS). The times until 10% recovery were similar in the 2M2V and 4V groups (59.9 ± 12 vs 68.2 ± 25 min, P = NS) and were slower than in the 2V group (37.2 ± 9 min, P < 0.05). Between T10 and T25, recovery after 2M2V resembled that after 2V (6.7 ± 3 vs 5.7 ± 1 min, P = NS) and was faster than after 4V (10.9 ± 7 min, P<0.05).ConclusionsWhen 2 × ED95 of mivacurium is added to 2 × ED95 of an intermediate or long-acting relaxant, recovery after T10 will proceed as if one had administered the longeracting agent alone.RésuméObjectifDécrire les caractéristiques de la curarisation initiale et de la décurarisation après l’administration du mivacurium associé au vécuronium.MéthodesAu cours de cette étude contrôlée aléatoire, 30 adultes consentants ASA I–III ont été répartis en trois groupes. Le groupe 2M2V a reçu deux fois la dose (2 × ED95) de mivacurium (0,15 mg · kg−1) nécessaire pour causer une dépression de 95% de la réponse au twitch plus 2 × ED95 de vécuronium (0,1 mg · kg−1), le groupe 2V a reçu 2 × ED95 de vécuronium, et le groupe 4V, 4 × ED95 de vécuronium. Les réponses évoquées au niveau de l’adducteur du pouce ont été évaluées à l’aide d’un transducteur. Les temps nécessaires à une curarisation maximale et à 10% et 25% de décurarisation (T10 et T25) dans chaque groupe ont été exprimés en moyenne ± écart-type et comparés avec ANOVA.RésultatsLe début de la curarisation dans le groupe 2M2V a été de 27% plus rapide que dans le groupe 2V (respectivement 2,0 ± 0,6 vs 2,7 ± 0,8 min, P < 0,05) et identique au groupe 4V (1,95 ± 0,3 min, P = NS). Le temps nécessaire à 10% de décurarisation a été identique dans les groupes 2M2V et 4V (59 ± 0,3 vs 68 ± 25 min, P = NS) et était plus prolongé que dans le groupe 2V (37,2 ± 0 min, P < 0,05). La décurarisation entre T10 et T25 était identique après 2M2V et 2V (6,7 vs 5,7 ± 1 min, P = NS) et était plus rapide après 4V (10,9 ± 7 min, P < 0,05).ConclusionQuand le mivacurium 2 × ED95 est ajouté à ≥ 2 × ED95 d’un relaxant intermédiaire ou de longue durée, la décurarisation après T10 a les mêmes caractéristiques qu’un agent de longue durée administré seul.

Laparoscopic pelvic lymphadenectomy during epidural anesthesia

This report describes the perioperative management of a 70-year-old man undergoing bilateral pelvic lymphadenectomy. Because of concerns regarding this patients high risk for myocardial ischemia, the four-hour surgical procedure, which included the formation of pneumoperitoneum, was performed during epidural anesthesia with minimal sedation. The anesthetic implications of pneumoperitoneum during regional anesthesia are discussed.

Eyelid movement during complete neuromuscular block.

Nondepolarizing muscle relaxants are competitive antagonists of the acetylcholine nicotinic receptors found on the skeletal muscle end plate. In contrast, smooth muscle is innervated by sympathetic and / or parasympathetic fibers via neurotransmitters (including acetylcholine), which bind to IX-, p- or muscarinic receptors. Smooth muscle activity is therefore not affected by blockade of the nicotinic receptors. Consequently, contraction of smooth muscle can occur even in the presence of complete paralysis of skeletal muscle.

The effect of solubility and hyperlipidemia on perioperative arterial blood gas tensions

A case is presented to illustrate the need for technical care when handling blood gas samples. The physics of solubility are used to show hour samples changed their oxygen tension (pO2) during handling, while investigating a clinical case to show the effect of hyperlipidemia on blood gases. It appeared that inadvertent access to air allowed atmospheric oxygen to equilibrate with the sample. The physical laws predicting the effect of partial pressure and temperature on gas solubility in a liquid are illustrated by the pO2 levels measured in this case. Effects due to hyperlipidemia were not observed. The calculations are described in detail. Brief suggestions for sample handling to avoid misleading results from such cases are discussed.