Malignant hyperthermia--the acute crisis.
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Acid-Base Equilibrium↗
Biomedical subjects
D J Steward
Publications and source records attributed to D J Steward.
Posterior laryngeal cleft - anaesthetic experiences.
Two cases of congenital posterior laryngeal cleft are reported which typify the anaesthetic techniques used for operation on this defect at The Hospital for Sick Children, Toronto. Although this anomaly of the airway is rare, it is potentially curable by surgery and should be included in the differential diagnosis of neonatal respiratory distress aggravated by feeding. The anaesthetic technique used for microlaryngeal surgery consisted of topical lidocaine, insufflation of oxygen and halothane with supplementary methoxyflurane and spontaneous ventilation. A nasotracheal tube is left in situ postoperatively until laryngeal oedema has subsided. The literature is reviewed and the relevant anaesthetic experience over a ten-year period at The Hospital for Sick Children, Toronto, is summarized.
Anesthesia↗
Rectal methohexitone for induction of anaesthesia in children.
Rectal induction of anaesthesia using ten per cent methohexitone is a safe and effective method for young children. It is particularly applicable to the child three months to four years of age. Twenty-five mg.kg-1 of methohexitone should be given and the child should be observed continuously by the anaesthetist until he falls asleep. Equipment to establish an artificial airway and to ventilate the lungs should be immediately at hand. The use of rectal methohexitone does not significantly delay immediate or late recovery after short (30-minute) surgical procedures.
Age Factors↗
Studies on the ultrastructural morphology of Bacteroides nodosus.
The morphology of Bacteroides nodosus was examined with the electron microscope. B nodosus stained with solium phosphotungstate and uranyl acetate possessed fimbriae and in addition organisms negatively stained with sodium phosphotungstate often possessed rings on their surface. Phage-like particles were also observed in negatively stained preparations. In thin sections, B nodosus had a multilayered cell envelope and the type of cell division characteristic of Gram-negative bacteria. The cytoplasmic region contained a diffuse nucleoid area, ribosomes and, sometimes, concentrically arranged membranous lamellae. Fimbriae and capsular material were also seen in sections of B nodosus fixed with glutaraldehyde-osmium. Their visualisation appeared to be enhanced when ruthenium red was incorporated n the glutaraldehyde-osmium fixative but only when sections were stained with heavy metal salts, indicating that the fimbriae and capsule were not predominantly polysaccharide in nature.
Bacteroides↗
Intramyocardial pH as an index of myocardial metabolism during cardiac surgery.
At present, a practical method for continuous monitoring of the state of tissue metabolism in the individual patient's heart during cardiac operations is not available. We have explored the use of miniature electrode measurements of myocardial interstitial pH to provide this monitoring capability, making comparisons with intracellular pH in left ventricular biopsy specimens and with tissue PCO2 measured by mass spectrometry. The electrode system consisted of a hydrogen ion-sensitive glass miniature electrode, housed in the beveled end of a 21 gauge (0.8 mm diameter) hypodermic needle, and a 2 mm diameter reference electrode, with an internal silver-silver chloride electrode coupled to tissue through a saline bridge (150 mM/L sodium chloride) saturated with silver chloride. Accuracy in blood at 37 degrees C was compared with conventional instrumentation (Radiometer BMS-3 MK-2 Blood Micro System) over a pH range of 7.4 to 6.4 with linear regression analysis (n = 26) revealing a high correlation (r = 0.997) and a mean difference in paired observations of only 0.01 +/- 0.004 (mean +/- SEM) pH units. In two groups of dogs on cardiopulmonary bypass, the pH needle and reference electrodes were inserted into the anterior wall of the left ventricle. Ischemic arrest of the heart at 37 degrees C was used to vary myocardial pH. In Group 1 (n = 8), intracellular pH was estimated from left ventricular biopsy specimens (400 mg each) taken over a microelectrode pH range of 7.37 to 6.37, snap frozen, and homogenized. In Group II (n = 6), tissue PCO2 in the anterior wall of the left ventricle was determined by mass spectrometry (sampling catheter 1.3 mm diameter). Miniaturized electrode (interstitial) pH exceeded biopsy (intracellular) pH under control conditions by 0.28 +/- 0.025 pH units (p less than 0.001), but below an electrode pH of 6.8 the results of the two techniques did not differ significantly. The tissue PCO2 rose from 69 +/- 2 mm Hg to a final plateau of 419 +/- 25 mm Hg, which was similar to the predicted value of 427 +/- 28 mm Hg calculated from the pH change (7.37 +/- 0.01 to 6.01 +/- 0.07), providing a further independent check on the pH electrode technique. These data indicate that our intramyocardial pH measurements do reflect intracellular metabolism during elective arrest of the heart and may have potential for clinical use.
Animals↗
The uptake and excretion of nitrous oxide in the newborn.
In the newborn, the uptake of nitrous oxide into the alveolus is very rapid, as is the fall in alveolar levels following withdrawal of the agent. During recovery relatively large volumes of nitrous oxide are excreted in the first minute, after which the excretion rate rapidly declines, most of the gas having been eliminated.
Humans↗
Stabilometry: a new tool for the measurement of recovery following general anaesthesia for out-patients.
A stabilometer has been used to measure changes in the activity of postural muscles during the later stages of recovery from anaesthesia. It is concluded that stabilometry might be a useful tool with which to measure and record the extent of recovery andthat this might be especially useful for use after out-patient sugery.
Ambulatory Care↗
Psychomotor development of infants and children after profound hypothermia during surgery for congenital heart disease.
We assessed neurological status and cognitive, verbal, social and motor skills of 17 children who had undergone cardiac surgery under profound hypothermia, and of seven siblings (controls). None of the subjects had significant neurological impairment. The mean development quotient (DQ) for the patients was 92.5 (in the low-average range) and for the controls was 103 (average). The DQ of one patient (71) was below the normal range. Development of the patients was comparable with that reported by other authors for children with cyanotic congenital heart-disease who have not undergone cardiac surgery. It correlated with the type of congenital heart-disease but not with the duration of hypoxic arrest. It is concluded that profound hypothermia can be used safely during the correction of cardiac defects in infants, without fear of retarding psychomotor development.
Cardiac Surgical Procedures↗
Unexpected excessive bleeding during operation: role of acetyl salycilic acid.
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Adolescent↗
A trial of enflurane for paediatric out-patient anaesthesia.
Enflurane was compared with halothane for anaesthesia for short surgical procedures in paediatric out-patients. Induction of anaesthesia was more prolonged with enflurane and recovery times were similar with both agents. Coughing and laryngospasm during induction occurred more frequently with enflurane. The incidence of post-operative complications was essentially similar in both groups, but there was no evidence that the use of enflurane was followed by rapid recovery at home. Enflurane has no advantages over halothane in anaesthesia for short procedures for paediatric out-patients.
Ambulatory Care↗
The early history of anaesthesia in Canada: the introduction of ether to upper Canada, 1847.
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Anesthesia↗
Sodium nitroprusside: factors which attenuate its action. Studies with the isolated gracilis muscle of the dog.
In a laboratory preparation of the isolated, acutely denervated, and separately perfused canine gracilis muscle we have made the following observations: 1. At physiological pH, sodium nitroprusside significantly decreases the vascular resistance; 2. At physiological pH, cyanide significantly attenuates the effect of sodium nitroprusside; 3. In an acidaemic milieu, our data suggest that the effect of sodium nitroprusside may be attenuated. We speculate that patients who manifest resistance to the hypotensive effect of sodium nitroprusside may not normally eliminate the cyanide that is released from the biodegradation of sodium nitroprusside. They accumulate free cyanide which interferes with the action of sodium nitroprusside at the receptor level, leading to administration of more nitroprusside and setting in motion a positive feedback vicious cycle. When one is faced with the problem of an abnormal response to sodium nitroprusside in a fit patient, although many factors may be involved, we suggest that the possibility of rising blood cyanide levels and acidosis be given high priority.
Animals↗
A disposable condenser humidifier for use during anaesthesia.
A disposable heat and moisture exchanger ("Artificial Nose") which is designed for use during endotracheal anaesthesia is described together with an evaluation of its performance. It has a low dead space, minimal resistance to gas flow, and is potentially capable of conserving 50 per cent of the respiratory water loss in the intubated patient.
Adolescent↗
A technique for measuring regional myocardial blood flow and its application in determining the effects of hyperventilation and halothane.
A method for measuring regional myocardial blood flow with a polarographic hydrogen-clearance technique, and its experimental application in dogs, are described. Under pentobarbitone anaesthesia, flow to the superficial (3 mm) and deep (8 mm) layers of the left ventricle was not significantly different. Neither hypocapnia (PaCO2 = 24 mm Hg) nor halothane significantly altered differential distribution of blood flow to the superficial and deep layers of the myocardium. Hypocapnia was followed by a fall in myocardial blood flow (MBF) associated with increased myocardial vascular resistance (MVR). Administration of halothane 0.5 per cent at normal levels of PaCO2 led to a fall in MBF of approximately 20 per cent with no significant changes in MVR.
Alkalosis, Respiratory↗
The effect of splenectomy on circulatory adjustments to hypoxaemia in the anaesthetized dog.
Six intact and seven splenectomized dogs were subjected to a similar degree of hypoxaemia while under light anaesthesia and artificial ventilation. In the intact animals, heart rate, cardiac output, myocardial contractility and oxygen consumption were increased as a result of hypoxaemia; oxygen transport was not affected. In the splenectomized animals the changes in cardiac output and myocardial contractility were small, and oxygen availability was decreased.
Anesthetics↗
Incidence of respiratory allergy not increased after anesthesia in infancy.
A 12-year follow-up study of children who had had operations with general anesthesia in infancy and of nonhospitalized children of the same age showed almost identical incidences of respiratory allergy in the test and control groups. General anesthesia in infacy does not predispose to respiratory allergies in childhood.
Adolescent↗
Letter: Identification of syringe contents.
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Drug Labeling↗
A simplified scoring system for the post-operative recovery room.
A new and very simple scoring system for recording post-anaesthetic recovery is described. When numerical values are assigned to factors indicating recovery progress or lack of it is obvious. The records may have medico-legal value. It can be incorporated into the Recovery Room Record.
Anesthesia, General↗