An armoured endotracheal tube obstruction in a child

The case of a child whose tracheal tube became obstructed intraoperatively 30 minutes after intubation is reported. It appears that this obstruction was related to the development of bubbles within the walls which expanded upon exposure to nitrous oxide and diffusion of that gas into the bubbles. The authors want to point out the risk of gas diffusion into the walls of the tube and the possibility that repeated sterilization may enhance the development of bubbles. Les auteurs rapportent l’observation d’un enfant de sept mois dont la sonde tracheale s’est obstruée 30 minutes après l’intubation. Cette obstruction était due à l’expansion de bulles incluses dans la paroi du tube après exposition au N₂O et diffusion de celui-ci à l’interieur des bulles. Ils accusent également la stérilisation répétée de la sonde armée (contre l’avis du constructeur) d’avoir favorisé le développement de ces inclusions bulleuses.     

Atracurium and vecuronium interaction with gentamicin and tobramycin

Drug interactions between the aminoglycosides (tobramycin and gentamicin) and atracurium and vecuronium were studied prospectively in 44 patients. Twenty-two patients had therapeutic serum levels of tobramycin or gentamicin and 22 served as controls. Onset time, clinical duration, and time to spontaneous recovery of T4/T1 ratio of 0.70 after atracurium or vecuronium injection were measured. No statistically significant differences were found in onset time, but clinical duration and time to recovery were significantly longer in patients receiving tobramycin or gentamicin and paralyzed with vecuronium than for controls (P less than 0.01 for clinical duration and P less than 0.0005 for recovery). The neuromuscular block produced by atracurium was not significantly influenced by the presence of therapeutic serum levels of tobramycin or gentamicin. We conclude that for patients treated with these antibiotics, atracurium may present some advantages over vecuronium when a prolonged block is not desired.     

Surgery in Jehovah’s Witnesses

This is a retrospective study of the outcome of surgical procedures in patients who were Jehovah's Witnesses. Over a 75-month period, 58 Jehovah's Witness patients had 78 surgical procedures at the Vancouver General Hospital. Three patients had preexisting anaemia of less than 100 g.L-1 haemoglobin. Postoperative haemoglobin concentration decreased below 50 g.L-1 in three patients. One patient had a postoperative haemoglobin of 34 g.L-1 (haematocrit 10.1 per cent) and survived. One patient died from uncontrollable postoperative haemorrhage. Perioperative morbidity was not uncommon, including significant hypotension (eight cases), cardiac arrhythmias (six), myocardial ischaemia (three), excessive bleeding (four), postoperative nausea or syncope (four), and wound or urinary tract infection (four).     

Computerized axial tomo-epidurographic and radiographic documentation of unilateral epidural analgesia

A 23-year-old primigravid patient who received epidural analgesia for pain of labour presented with persistent, apparently irremediable, unilateral analgesia. Computerized axial tomo-epidurography demonstrated absence of circumferential spread due to lateral placement of the catheter. Transforaminal escape of contrast medium into the paravertebral area had occurred and anterior and posterior midline partitioning of the epidural space was obvious. All the usual measures to promote contralateral analgesia, except re-insertion of the catheter, had been tried without success.     

Consequences of fluid absorption during transurethral resection of the prostate using distilled water or glycine 1.5 per cent

This prospective and randomized study compared the consequences of two irrigating fluids, distilled water and glycine for transurethral prostatectomy. Forty-nine consecutive unselected patients undergoing transurethral resection of the prostate with spinal anaesthesia were investigated. The irrigating fluid was either distilled water (group A, 24 patients) or glycine 1.5 per cent (group B, 25 patients). The absorption of irrigating fluid was measured, all surgical events and any clinical signs of TURP syndrome during and after surgery were recorded. Early signs of TURP syndrome were observed in one patient in group A and in four in group B without further consequence. From all the biological variables, only plasma protein concentration, haematocrit, free plasma haemoglobin and free bilirubin concentrations were found to have changed. Plasma protein concentration and haematocrit decreased significantly during and after surgery in the two groups. Free plasma haemoglobin increased significantly with time: a significantly higher concentration was observed in group A than group B. Free bilirubin concentration increased with time in the two groups and was statistically greater in group A. With the two irrigating fluids, we observed a significant amount of haemolysis and haemodilution without clinical consequences. A low irrigating fluid pressure, a short resection time, and the use of spinal anaesthesia seems to us to be essential. Close observation of patients following transurethral prostatectomy is needed but the choice of the irrigating fluid does not seem to be important. Cette étude prospective et randomisée a comparé les conséquences de deux liquides d’irrigation, l’eau distillée et le glycocolle au cours de la chirurgie prostatique par voie basse. Quarante-neuf patients consécutifs, non sélectionnés, bénéficiant d’une résection transuréthrale de prostate sous rachianesthésie, sont étudiés. Le liquide d’irrigation est soil l’eau distillée (groupe A, 24 patients), soit le glycocolle à 1.5 pour cent (groupe B, 25 patients). L’absorption des liquides d’irrigation, les incidents chirurgicaux et les signes cliniques du syndrome de réabsorption sont systématiquement notés. Des signes caractéristiques du syndrome de réabsorption sont observés dans un cas dans le groupe A et dans quatre cos dans le groupe B sans conséquence ultérieure. Seuls la protidémie, l’hématocrite, l’hémoglobine plasmatique libre et la bilirubine libre changent significativement. L’hémoglobine plasmatique libre augmente significativement dans les deux groupes, avec un taux plasmatique significativement plus élevé dans le groupe A. Avec les deux liquides d’irrigation, on observe une hémolyse et une hémodilution sans conséquence clinique. Un temps de résection court, un faible niveau de pression d’irrigation, l’utilisation de l’anesthésie rachidienne nous semblent trés importants. Une surveillance clinique et biologique attentive pendant et après la résection transuréthrale de prostate sont nécessaires; en revanche, le choix du liquide d’irrigation ne semble pas l’élément essentiel.     

Haemodynamic effects of atropine during halothane or isoflurane anaesthesia in infants and small children

In this study, two-dimensional and pulsed Doppler echocardiography were used to measure cardiovascular changes before and after IV atropine in 31 infants and small children during halothane (n = 15) or isoflurane (n = 16) anaesthesia. Prior to induction of anaesthesia heart rate (HR), mean blood pressure (MBP), and two0dimensional echocardiographic dimensions of the left ventricle and pulmonary artery bloodflow velocity were measured by pulsed Doppler echocardiography. Cardiovascular measurements were repeated while anaesthesia was maintained at 1.5 MAC halothane (n = 15) or isoflurane (n = 16). Atropine 0.02 mg·kg⁻¹ IV was then administered and two minutes later, a third set of cardiovascular data was obtained. Heart rate decreased during halothane anaesthesia but did not change significantly during isoflurane anaesthesia. Mean blood pressure, cardiac output (CO) and stroke volume (SV) decreased similarly during 1.5 MAC halothane or isoflurane anaesthesia. Ejection fraction (EF) decreased and left ventricular end-diastolic volume (LVEDV) increased significantly in bothgroups, but decreases in EF (32 ± 5 percentvs18 ± 5 per cent) and increases in LVEDV (18 ± 7 per cent vs7 ± 5 per cent) were significantly greater during halothane than during isoflurane anaesthesia. Following atropine, HR increased more in the patients maintained with halothane (31 ± 6 per cent), than during isoflurane anaesthesia (18 ± 5 per cent). Atropine increased CO in both groups of patients, but SV and EF remained unchanged. When compared with awake values, HR increased similarly and significantly (18 ± 4 per cent) following atropine in both groups, and CO returned to control levels. Halothane decreased EF and increased LVEDV more than isoflurane at 1.5 MAC end— expired anaesthetic levels. Atropine did not diminish the myocardial depression produced by halothane or isoflurane. The increase in CO following atropine during halothane and isoflurane anaesthesia in infants and small children is the result of increases in HR alone. Nous avons utilisé un appareil à échocardiographie bi-dimensionnelle couplé à un Doppler pulsé chez des bébés et de jeunes enfants pour évaluer l’impact hémodynamique de l’halothane (n = 15) et de l’isoflurane (n = 16) et la modification possible de ces effets par l’atropine. Nous avons mesure la frequence cardiaque (FC), la pression artérielle moyenne (PAM), la dimension de la cavité ventriculaire gauche (par écho bi-dimensionnelle) et la vélocité du flot sanguin pulmonaire (par Doppler) et ce, en trois occasions soit avant l’induction, après l’instauration de 1.5 MAC d’halothane ou d’isoflurane et finalement, deux minutes après l’injection IV de 0.02 mg·kg⁻¹ d’atropine. On ne nota une baisse de la frequence cardiaque qu’avec l’halothane tandis que la PAM, le débit cardiaque (DC) et le volume d’éjection (VE) diminuaient autant avec l’un ou l’autre anesthésique. La diminution de la fraction d’éjection (FE) et l’augmentation du volume télédiastolique du ventricule gauche (VTDVG) significatives pour les deux groupes, étaienl plus marqué avec l’halothane qu’avec l’isoflurane: FE 32 ± 5 pour cent vs18 ±5 pour cent; VTDVG 18 ± 7 pour cent vs 7 ± 5 pour cent. Avec l’atropine, la FC monta plus dans le groupe halothane (31 ± 6 pour cent) que dans le groupe isoflurane (18 ± 5 pour cent), le DC augmentant dans les deux groupes, alors que le VE et la FE demeuraient inchangés. Comparée aux mesures pré-induction, l’atropine amenait une hausse significative de la FC, semblable dans les deux groupes (18 ± 4 pour cent) et restaurait le DC. Donc, chez les bebes et les jeunes enfants, a 1.5 MAC, l’halothane diminue la FE et augmente le VTDVG plus que ne le fait l’isoflurane. L’atropine ne modifie pas la depression myocardique et elle ne restaure le DC que par une hausse de la FC.

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Supported by PHS Grant No. 8507300 from the College of Medicine, University of Iowa Hospital, Iowa City, IA.     

Reactivity and toxicity of atracurium and its metabolitesin vitro

Cytotoxicity of atracurium and of its metabolites was tested in vitro.Exposure of isolated rat hepatocytes to atracurium produced cellular damage evidenced by extrusion of an intracellular enzyme, lactate dehydrogenase (LDH), into the incubation medium. Leakage of LDH was directly related to the concentration of atracurium in the medium (250 to 800 μM). If the spontaneous degradation of atracurium (presumably via Hofmann elimination) was first carried out in vitroand the degradation products subsequently added to the isolated hepatocytes, the leakage of LDH was also dose-dependent but larger than that observed after the addition of the parent drug. When l-cysteine was admixed to the products of the spontaneous degradation of atracurium prior to their addition to the liver cells, no leakage of LDH was observed. The results are compatible with the working hypothesis that atracurium itself and, even more so, acrylates formed in Hofmann elimination of atracurium, are reactive toward nucleophiles and damage the cells by alkylating nucleophiles present in cellular membranes. Antecedent covalent binding of acrylates to the nucleophile cysteine, i.e., the formation of acrylatecysteine adducts, saturated the reactive capacity of acrylates for nucleophiles and thus prevented the reactive metabolites from alkylating the endogenous nucleophiles. Possible clinical consequences resulting from in vivogeneration of reactive metabolites are not clear at the present time but are projected to be related to (a) the dose of atracurium administered, (b) the amount of acrylates generated, (c) the functional importance of the endogenous nucleophiles alkylated, and (d) the pathway and the speed of detoxification of atracurium and its metabolites.     

Effects of halothane on arrhythmias induced by myocardial ischaemia

The effect of halothane on arrhythmias induced by ischaemia was investigated in rats, isolated perfused rat hearts, and pigs. Responses to the occlusion of the left anterior descending coronary artery were determined in groups (n = 9) of chronically prepared rats treated with no halothane, 0.5, or 1.0 per cent halothane immediately after occlusion; in isolated rat hearts (n = 10) treated with no halothane, 0.5, 1.0, 2.0, or 4.0 per cent halothane for 15 min before and after occlusion; and 20–25 kg pigs (n = 11) anaesthetised with halothane or pentobarbital. The ECG, arrhythmias, blood pressure (BP), heart rate (HR) and extent of infarction were determined in each model. In pigs, left ventricular pressure, dp/dt_max and cardiac output were also measured. In chronically prepared rats, halothane anaesthesia started after occlusion was antiarrhythmic and decreased the incidence of ventricular fibrillation and resulting mortality. In isolated rat hearts, 0.5 or 1.0 per cent halothane had little effect on occlusion-induced arrhythmias. The highest concentration of halothane increased the incidence of ventricular fibrillation both before and after occlusion. Halothane decreased developed ventricular pressure in a dose-dependent manner. In acutely prepared pigs, halothane pre-treatment had no appreciable effect upon occlusion-induced arrhythmias when compared with pentobarbital anaesthesia. Thus, halothane is antiarrhythmic when treatment is initiated after occlusion in the rat but this action is not seen in isolated hearts or intact pigs. The antiarrhythmic action of halothane is, therefore, species and model dependent.     

Anaesthetic experience with paediatric interventional cardiology

Anaesthetic and sedation techniques, complications and outcomes were reviewed in 176 children undergoing 184 interventional cardiologic procedures. Techniques included sedation only, and ketamine, inhalational or narcotic anaesthesia. Ketamine infusion was the technique most frequently used. Ketamine was associated with a higher incidence of respiratory complications (P < 0.05) than the other techniques. The higher incidence of hypercarbia (15.6 per cent), which did not affect outcome, may be attributable to the use of supplemental sedatives. The incidence of upper airway obstruction (7.8 per cent) was similar to that of previous studies. Vascular compromise resulted from the procedure in 33 patients, necessitating surgical correction in 16. Cardiac perforation occurred in four cases, causing one death. Pulmonary valve stenosis was most amenable to balloon dilatation and aortic valve stenosis least amenable. Ketamine was the anaesthetic agent preferred by cardiologists for use in the catheterisation suite when general anaesthesia was required. Vigilant monitoring by anaesthetic staff is necessary during the procedure, and avoidance of concomitant narcotics is recommended if a ketamine technique with spontaneous ventilation is used. Les techniques anesthésiques et de sédation ainsi que les complications et les issues ont été revues chez 176 enfants subissant 184 procedures cardiaques. Les techniques ont inctu soil la sédation seulement, soit l’anesthésie à la kétamine, aux agents d’inhalation ou aux narcotiques. La perfusion de kétamine était la technique la plus fréquemment utilisée. La ketamine était associée à une plus grande incidence de complication respiratoire (P < 0.05) comparativement aux autres techniques. La plus grande incidence d’hypercarbie (15.6 pour cent), n’ayant pas affecté l’issue, pourrait être attribuée à l’utilisation additionnelle de sédatifs. L’incidence d’obstruction des voies aériennes supérieures (7.8 pour cent) était similaire aux études préalables. Un problème vasculaire suite à la procédure fut observé chez 33 patients dont 16 ont requis une correction chirurgicale. Une perforation cardiaque est survenue dans quatre cas provoquant le décès d’un seul patient. La sténose de la valve pulmonaire était la procédure la plus susceptible d’être dilatée et la sténose de la valve aortique la moins susceptible. La kétamine était l’agent anesthésique préféré par les cardiologistes lors des cathétérisations quand une anesthésie générate était requise. Une surveillance vigilante par une équipe anesthésique fut nécessaire durant la procedure. Il faut aussi éviter l’administration de narcotiques si la kétamine est administrée en respiration spontanée.

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Presented in part at the Canadian Anaesthetists’ Society annual meeting in Halifax, June 1988.     

Use of an in Vitro Model for the Assessment of Muscle Damage from Intramuscular Injections: in Vitro-in Vivo Correlation and Predictability with Mixed Solvent Systems

The potential of binary mixtures of propylene glycol–water, ethanol–water, and polyethylene glycol 400–water to cause skeletal muscle damage (myotoxicity) following intramuscular injection was examined with an in vitro model using the isolated rat muscle. At moderate concentrations (20–40%, v/v) of the organic cosolvent, the order of myotoxicity was propylene glycol > ethanol polyethylene glycol 400. The in vitro results were then compared with in vivo toxicity in rabbits after injection of normal saline, 40% (v/v) polyethylene glycol 400, 40% (v/v) propylene glycol, indocyanine green in normal saline, and indocyanine green in 40% (v/v) propylene glycol. Employing the area under the creatine kinase activity curve from 0 to 72 hr as the index of skeletal muscle damage, an excellent in vitro–in vivo correlation was observed. The basic myotoxicity relationships obtained from the binary cosolvent systems were then used to examine the myotoxicity of ternary organic cosolvent mixtures. Several mixed solvent systems with the same theoretical molar solubilization power for a model compound, diazepam, were selected to determine (1) if myotoxicity can be reduced by changing the composition of the ternary mixtures and (2) if myotoxicity of the individual components is additive. For the solvent systems containing propylene glycol, ethanol, and water, the total myotoxicity equaled the sum of the individual myotoxicity of each component. In contrast, for the solvent systems containing polyethylene glycol 400, the total myotoxicity was only half of the sum of individual toxicities. These results suggest that polyethylene glycol 400 in mixed cosolvent systems might have a protective effect on the myotoxicity generated by intramuscular injections.