Charul Munshi

Multicenter study of general anesthesia. I. Design and patient demography.

A prospective randomized clinical trial of enflurane, fentanyl, halothane, and isoflurane is described. The 17,201 patients were stratified into two groups (preanesthetic medication and no preanesthetic medication) and were randomized to one of four study agents: enflurane, fentanyl, halothane, and isoflurane. Fifteen university-affiliated hospitals in the United States and Canada participated. All patients were first assessed preoperatively. Data were collected during anesthesia, in the immediate recovery period, and for up to 7 days after anesthesia/surgery. The mean age of the patients was 43 yr, the mean height 167 cm, and the mean weight 68 kg. Sixty-five percent of patients were female. In this study 90.7% of patients were classified as ASA Physical Status 1 or 2, and 34.7% of patients smoked. It is concluded that pooling of data across institutions was valid and does allow determination of the efficacy and relative safety of the four study agents.

Antagonism of mivacurium neuromuscular block: neostigmine versus edrophonium.

This study was designed to compare the effectiveness of antagonism of mivacurium blockade with either neostigmine, edrophonium, or spontaneous recovery.Thirty ASA physical status I or II patients provided informed consent and were randomized to one of the following groups: Group 1, placebo saline; Group 2, edrophonium (1 mg/kg); and Group 3, neostigmine (70 micro gram/kg) (n = 10/group). All studied patients had anesthesia induced with propofol and maintained with propofol/N2 O/fentanyl. Mivacurium bolus of 0.2 mg/kg was used for endotracheal intubation and an infusion titrated to maintain deep levels of block (T1 % = 1%-5%) (T1 % = first response/control response times 100). The antagonist was injected at a deep level of the block (T1 % = 1%-8%) and neuromuscular (NM) recovery was evaluated by train-of-four twitches (TOF). T1 % was used during maintenance, whereas both T1 % and TOF% (fourth response/first response times 100) were used during recovery. Investigators were blinded to the antagonist used. Plasma cholinesterase activity was measured prior to antagonist administration (0 min), as well as 15, 30, and 60 min after. Plasma cholinesterase activity was decreased to 29% of control at 15 min and remained at approximately 60% of the control after neostigmine administration. Edrophonium did not affect plasma cholinesterase activity. Clinically adequate spontaneous recovery (TOF% >or=to 70%) of the mivacurium block with placebo required 15-18 min. On average, clinically adequate antagonism of mivacurium by edrophonium was 50% faster than placebo and 30%-40% faster than with neostigmine. In summary, the speed of antagonism with edrophonium is faster than with neostigmine when antagonizing deep mivacurium NM block. Neostigmine-induced depression of plasma cholinesterase, slower onset of action, or combination of both may explain this observation. (Anesth Analg 1995;81:1005-9)

Capnography for detection of endobronchial migration of an endotracheal tube

A patient is described in whom migration of an endotracheal tube into the right main bronchus was suspected when end-tidal carbon dioxide suddenly decreased from 28 to 22 mm Hg. Acute changes with migration of the endotracheal tube into the main bronchus were also studied in an animal experimental model. End-tidal carbon dioxide decreased and tracheal (inflation) pressure increased, with no change in tidal volume. Arterial blood gases showed time-dependent decreases in pH and oxygen tension and an increase in carbon dioxide tension.

Postoperative unilateral facial oedema: a complication of acute flexion of the neck

A case report describing a complication following the use of the sitting position and an extreme flexed position of the neck is presented. The patient developed unilateral oedema of the face, tongue and soft tissues of the mouth. The trachea was reintubated and the oedema subsided without treatment. The cause of the oedema is believed to be obstruction of the venous drainage of the head and neck.RésuméOn rapporte une complication de la position assise avec flexion extreme du cou. Le patient a développé un oedème de la face, de la langue et des tissus mous de la bouche. On réintuba le patient et l’oedème régressa spontanément. On attribue cet oedème à une obstruction au drainage veineux de la tête et du cou.

The effect of midazolam on median nerve somatosensory evoked potentials.

Objective. To quantify the effect of an induction dose of midazolam on median nerve somatosensory evoked potentials.Methods. We studied 10 patients undergoing lumbar spine surgery. After an induction dose of intravenous midazolam was given, MNEPs were collected for ten minutes. After ten minutes the patients were intubated and their anesthetic was supplemented with 0.5% isoflurane, narcotic, and N2O.Results. We found a clinically significant decrease in amplitude and an insignificant delay in latency.Conclusion. When midazolam is used as an anesthetic induction agent, a decrease in amplitude can be expected.ResumeObjectif. Quantification des effets d’une doses d’induction de midazolam sur les potentiels evoques somatosensitifs du nerf médian (PESNM).Méthodes. Nous avons etudies 10 malades operes de l’épine dorsale lombaire. Aprés une induction intraveineuse au midazolam, les PESNM furent recueillis pour 10 minutes. Par apres, les malades regurent une intubation tracheale et leur anesthesic fut supplee à Paide de 0.5% d’isoflurane, de narcotiques et de protoxide d’azote.Resultats. Nous avons trouvé une diminution cliniquement significative de l’amplitude et une prolongation insignifiante de la latence des PESNM.Conclusion. Lors de l’emploi du midazolam comme agent d’induction, Ton peut s’attendre à une réduction de l’amplitude des PESNM.AbstraktZiel. Quantifizierung des Effektes einer Midazolam-Induktionsdosis auf die somatosensorisch evozierten Potentiale des N. medianus.Methoden. Wir untersuchten 10 Patienten, die sich einer Operation im lumbalen Wirbelsäulenbereich unterzogen. Nach einer Induktionsdosis Midazolam i.v. wurden SSEP vom N. medianus fur 10 min gesammelt. Nach 10 min wurden die Patienten intubiert, und die Narkose wurde supplementiert mit 0.5 Vol% Isoflurane, Narkotika und N20.Ergebnisse. Wir fanden eine klinisch signifikante Abnahme der Amplitude und eine nicht signifikante Verlängerung der Latenzzeit.Folgerung. Wenn Midazolam als Einleitungsanästhetikum benutzt wird, kann eine Abnahme der Amplitude erwartet werden.ResumenObjetivo. Cuantificar el efecto de una dosis de induccion de midazolam sobre los potenciales somatosensoriales evocados del nervio mediano (PENV).Metodos. Estudi amos 10 pacientes sometidos a cirugia sobre la columna lumbar. Una vez administrada una dosis de induccion de midazolam intravenoso, se coleccionaron PENV durante diez minutos. Transcurridos los diez minutos los pacientes fueron intubados y su anestesia fue suplementada con 0.5% de isofluorano, narcótico y N20.Resultados. Encontramos una disminucion significativa de la amplitud y un retardo no significativo de la latencia.Conclusión. Cuando se usa midazolam como agente de induccion, debe esperarse una disminución de la amplitud de PENV.

Hydropneumothorax after percutaneous nephrolithotomy.

Percu taneous nephrolithotomy is a relatively new technique that is gaining popularity because, when successful, it saves a patient a large flank incision and long hospitalization. The procedure is intended to remove upper urinary tract stones through a nephrostomy tube placed previously under fluoroscopic control. A nephroscope is then inserted through the nephrostomy, the stones visualized, and removed in toto or by fragmentation. Removing the fragments requires large volumes of irrigation fluid (10-15 L) to flush the renal pelvis. The solution is usually isotonic saline, although glycine has also been used (1). The amount of fluid used for irrigation is directly related to the length of the procedure and the degree of difficulty in removal of the stone. As with all new surgical techniques, the indications, contraindications, and complications are not completely defined. Complications reported in the literature include cardiac arrest (l), adult respiratory distress syndrome (2), extraperitoneal fluid extravasation (3), bleeding, and delayed rupture of a pseudoaneurysm (4). Two cases with other serious perioperative complications are described below.

Recognition of mixed anesthetic agents by mass spectrometer during anesthesia

Anesthetic agents are sometimes added to the wrong vaporizer on an anesthesia machine. As a result, the vaporizer may deliver a mixture of anesthetic agents at concentrations inappropriate for use on a patient. However, untoward clinical complications related to vaporizers can be prevented with a time-shared mass spectrometer. This device accurately and rapidly indicates the gases and gas concentrations present in a vaporizer.

Mass Spectrometer Failure: An Unusual Cause

A potentially serious problem is inherent in the current design of the mass spectrometer multiplex system. In spite of the filter on the sampling tube, foreign material can be aspirated into this tube, causing malfunction of the system. Prevention of this problem is discussed, and precautions are given.

Abstracts of scientific papers computers in anesthesia VII

S OF SCIENTIFIC PAPERS COMPUTERS IN ANESTHESIA VII October 21-24 Grand Canyon, Arizona Sponsored by Vanderbilt University School of Medicine Department of Anesthesiology Division of Continuing Medical Education and University of Iowa College of Medicine Department of Anesthesia