Consequences of misfilling contemporary vaporizers with desflurane

Desflurane is a volatile anaesthetic that combines low blood gas solubility (blood/gas partition coefficient =0.42 at 37° C), moderate potency (MAC = 6–7%), and high volatility (vapour pressure =681 mmHg at 20° C, boiling point = 23.5° C). The volatility and potency of desflurane prevent its safe use in vaporizers of traditional design. We present a mathematical model which demonstrates the potential for desflurane overdose if contemporary vaporizers are misfilled with desflurane. The most hazardous filling error occurs if an enflurane vaporizer is misfilled with desflurane. The calculated desflurane output of a misfilled enflurane vaporizer at a dial setting of 1% and a temperature of 22° C is 57.8%, or 9.6 MAC. For misfilled enflurane, isoflurane, and halothane vaporizers at dial settings equivalent to one MAC at 22° C, the calculated desflurane output is 14.0, 10.2, and 7.8 MAC, respectively. We conclude that the safe delivery of desflurane will require engineering safeguards, additional monitoring, and education of the anesthesia community.     

Three-dimensional structure of a membrane-containing virus.

The structure of Sindbis virus was determined by electron cryomicroscopy. The virion contains two icosahedral shells of viral-encoded proteins separated by a membrane bilayer of cellular origin. The three-dimensional structure of the ice-embedded intact Sindbis virus, reconstructed from electron images, unambiguously shows that proteins in both shells are arranged with the same icosahedral lattice of triangulation number T = 4. These studies also provide structural evidence of contact between the glycoprotein and the nucleocapsid protein across the membrane bilayer. The structural organization of Sindbis virus has profound implications for the morphogenesis of the alphaviruses. The observed interactions confirm stoichiometric and specific protein associations that may be crucial for virion stability and predict a mechanism for assembly.     

Parental 'expressed emotion' as a predictor of schizophrenic relapse

Fifty-seven schizophrenic patients were initially assessed after admission to hospital, at which time their parents completed a Camberwell Family Interview, generating "expressed emotion" (EE) scores. Relapse over the next nine months was not predicted by household EE status or by individual EE scales. Multivariate analyses suggested that a poor course after hospitalization was best predicted by a poor course before admission and by living in a one-parent household. High household EE status was a predictor only in one multivariate analysis after course of illness and one-parent household status had been entered, suggesting an interaction effect. We query the causal proposition linking high EE and relapse and suggest instead that a poor illness course may elicit high EE in relatives, particularly in one-parent households, and, thus, may make the principal contribution to the proposed link.     

T lymphocytes and activated eosinophils in airway mucosa in fatal asthma and cystic fibrosis.

With the use of monoclonal antibodies (mAb) and immunohistology, the numbers of phenotypically distinct cells infiltrating lung tissue from 15 postmortem (PM) cases of fatal asthma were quantified and compared with 6 cases of cystic fibrosis (CF) (three postmortem, three transplant) and 10 nonasthmatic cases of sudden death matched for age and sex. Tissue eosinophilia was significantly greater (p less than 0.001) in the fatal asthma group than in the CF or sudden death controls. In asthma, approximately 40% of the eosinophilic infiltrate was EG2 positive (an indication of eosinophil activation and secretion of eosinophil cationic protein). The numbers of eosinophils and EG2 positive cells were significantly elevated in the subjects with acute severe asthma who had had a duration of terminal illness exceeding, as compared with less than, 24 h (p less than 0.05). When compared with the sudden death controls, there were increases in the numbers of Dako L C positive cells (i.e., CD45 positive "total leukocytes") in both fatal asthma and CF (p less than 0.01 and 0.05, respectively). The mean number of MT-1 positive (T) cells in the asthma and CF groups was approximately twice that of the control (p less than 0.05 and 0.01, respectively). The mean number of MB2 positive (B) cells was similar for both the asthma and sudden death control groups but was significantly increased in CF (p less than 0.05). The average T:B cell ratios were 6:1, 1:1, and 2:1 in the fatal asthma, CF, and control groups, respectively. The results support a role for the T lymphocyte in the pathogenesis of fatal asthma and CF.(ABSTRACT TRUNCATED AT 250 WORDS)     

Normal perfusion pressure breakthrough complicating surgery for the vein of Galen malformation: report of three cases

Three cases are described of infants who developed malignant brain swelling (and in one case hemorrhage) after surgery for vein of Galen malformations. The cause for the brain swelling was felt to be due to hyperperfusion, or the "normal perfusion pressure breakthrough" syndrome. Although well-described for cerebral parenchymal arteriovenous malformations, cases of this complication occurring in vein of Galen malformations have not previously been reported. It is concluded from these cases that infants with large arteriovenous shunts, as attested by cardiac failure and cerebral atrophy, have an increased risk of developing this complication.     

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.     

Prenatal detection of Turner''s syndrome in conjunction with trisomy 20 mosaicism (45,X/46, X, +0).

A case of Turner's syndrome, detected antenatally and complicated by the finding of trisomy 20 mosaicism in 50% of cells from each of two amniotic fluid cultures, is described. Cultures from seven fetal tissues in the subsequent abortus showed a predominance of 45,X cells, but nevertheless suggested the existence of a very low level of trisomy 20 mosaicism in three fetal tissues. The diagnostic dilemma in interpreting trisomy 20 mosaicism is discussed.     

Development of methods to analyse transcranial Doppler ultrasound signals recorded in microgravity

During space flights, several clinical syndromes may be the result of changes in cerebral circulation. The purpose of the paper is to describe the development and initial evaluation of a system for recording, processing and displaying transcranial Doppler ultrasound (TCD) waveforms from the middle cerebral artery (MCA) in microgravity. Volunteers were repeatedly subjected to 15–20 s intervals of microgravity (‘near zero gravity’) during flights on the KC-135 military aircraft. Continuous TCD recordings from the MCA were stored on magnetic tape. The paper describes the system that was developed to digitise the Doppler ultrasound data and markers that corresponded to the various levels of microgravity, obtain the maximum and mean Doppler waveforms, identify the waveforms and quantify them. The results demonstrate the feasibility of making TCD recordings in a microgravity environment and illustrate excellent performance of the system and its ease of operation. Quantitative waveform analysis of the recordings from the first subject studied in the supine position showed statistically significant changes in MCA velocity waveforms during microgravity.     

Evaluation of the MS-2 automated antimicrobial susceptibility testing system: Report of a European collaborative study

The MS-2 is an instrument for rapid automated testing of antimicrobial susceptibility. Its performance was evaluated by comparison with disc diffusion and MIC tests in a collaborative study in four European laboratories. Tests on independently isolated organisms showed the MS-2 to be in essential agreement with conventional methods in 94.8% of tests. A further series of 170 welldefined pathogens for which a reference antibiogram was available were tested by MS-2 and the manual methods in all of the participating laboratories. MS-2 results were in full accord in 90 % of tests and in essential agreement in 94 %. MS-2 results compared at least as well with the reference values as did either of the manual methods. Initial problems of false susceptibility results with erythromycin and penicillin were resolved by (1) the addition of small amounts of erythromycin which acted as an inducer and (2) by the use of a low content penicillin disc. MS-2 was found to be reliable and needed no attention following loading of the test cuvette cartridges. A print-out of the results was available 2–5 h after inception of the test.