Showing papers in "Anesthesiology in 1965"

Hazards of nitrous oxide anesthesia in bowel obstruction and pneumothorax.

Abstract: An enclosed gas-filled space in the body will expand if gas within it is less soluble than the gas respired. Blood arriving at such a space can discharge a greater quantity of the soluble gas into the space than that blood can take up, assuming the tension gradient of each gas is equal. This results from the greater capacity of blood for the more soluble agent. When air was placed in the intestinal lumens of 3 dogs and nitrous oxide respired, intestinal gas volume increased 75 to 100 per cent in two hours and 100–200 per cent in four hours. Similarly, 300 ml. of air placed in the pleural space doubled in volume in 10 minutes, tripled in 45 minutes, and in one dog quadrupled in two hours. Nitrous oxide concentrations rose concomitantly in both the intestinal and pleural spaces. With cither gas in the intestine or in the pleural space, no volume changes were seen when the animal respired oxygen and halothane alone. These results suggest that nitrous oxide is relatively contraindicated in cases of intestinal obstruction or pneumothorax.

Equipotent alveolar concentrations of methoxyflurane, halothane, diethyl ether, fluroxene, cyclopropane, xenon and nitrous oxide in the dog.

Abstract: The minimum alveolar concentration of anesthetic (MAC) required to prevent response to a painful stimulus was determined in dogs for 7 agents. These equipotent concentrations (in volumes per cent at sea level) were: methoxyflurane 0.230, halothane 0.87, diethyl ether 3.04, fluroxene 6.0, cyclopropan

Cerebral Circulation During General Anesthesia and Hyperventilation in Man

Abstract: Studies of cerebral circulation and gaseous metabolism were performed in six healthy young volunteers during anesthesia induced with thiopental and maintained with nitrous oxide and d-tubocurarine. The blood thiopental level was very low when measurements were made, and intravenous d-tubocurarine has been shown not to affect cerebral flow or metabolism. Therefore 70 per cent nitrous oxide was probably the agent chiefly responsible for the changes observed. When Paco2 was normal, cerebral blood flow remained normal, but cerebral oxygen uptake decreased 23 per cent. About one third of this decrease was caused by a small decline in body temperature, with the remainder most likely owing to nitrous oxide. When mean arterial Pco2 was decreased to 18.3 mm. of mercury, cerebral blood flow was halved, and mean jugular venous Pco2 declined to 19.8 mm. of mercury, a level generally assumed to be associated with suboptimal cerebral oxygenation. However, cerebral metabolic rate for oxygen did not decrease further at this low Paco2.

Mechanism of Brachial Plexus Palsy Following Anesthesia

Abstract: The mechanism of injury to the brachial plexus which follows certain operative positions was studied in 15 cadavers by dissection and in five patients by radial artery pulse tracings. In particular the “hands up” and common supine positions were studied. Stretch was shown to be the most likely mecha

Change in Cerebrospinal Fluid Pressure During Pneumoencephalography Under Nitrous Oxide Anesthesia

Abstract: An increase in cerebrospinal fluid pressure incurs in dogs and humans anesthetized with nitrous oxide after air has been injected into the cerebral ventricles. The mechanism for the increase in pressure is felt to be due to the difference in blood solubility between nitrous oxide and nitrogen. Nitro

Cerebral carbohydrate metabolism during hypocarbia in man: studies during nitrous oxide anesthesia.

Abstract: Brain carbohydrate metabolism was studied in 11 healthy male volunteers during anesthesia induced with intravenous thiopental (5 mg./kg.) and maintained with 70 per cent N2O-30 per cent O2 and d-tubocurarine. When arterial PCO2 (PaCO2) was normal, oxygen and glucose consumption were reduced approximately 25 per cent from the normal value in conscious man; but no change in the pattern of glucose utilization was noted. A reduction in PaCO2 below 20 mm. of mercury was accompanied by a decreased aerobic and an increased anaerobic utilization of glucose. Mild, readily reversible changes in the EEG pattern also occurred when PaCO2 was less than 20 mm. of mercury. Clinical implications of these changes are discussed. The validity of several indices of cerebral carbohydrate metabolism is considered.

Differentiation of two types of pain by anesthetics.

Abstract: The pain thresholds, to a cutaneous thermal stimulus and to a tibial pressure stimulus were measured before, during, and after the administration of nitrous oxide (25–30 per cent in oxygen), halothanc (0.5 per cent) and sodium thiopcntal (100–150 mg. in 10 minutes). The thermal pain and the tibial pressure pain thresholds rose with nitrous oxide and halothane. The thermal pain threshold rose with sodium thiopcntal but simultaneously the tibial pressure pain threshold fell. It is deduced that the sensations produced by these two stimuli are neurologically different and that the known differences between the actions of barbiturates and inhalational anesthetic drugs on presynaptic inhibition in the spinal cord can account for this differentiation.

The mechanics of the respiratory system during anesthesia. the effects of atropine and carbon dioxide.

Abstract: The flow resistance, static compliance, kinetic compliance and pressure stress relaxation of the total respiratory system have been measured by the method of constant flow rate inflation of the lungs. The term kinetic compliance is introduced to distinguish a nonstatic compliance from the conventional dynamic compliance. Results for 20 supine apneic anesthetized patients prior to operation are presented. Atropine (0.012 mg./kg. intravenously) caused a 33 per cent fall in flow resistance and a 4 per cent rise in static compliance. The addition of carbon dioxide to the hypocapnic subject was associated with a 29 per cent decrease in flow resistance and no change in static compliance. A possible dual action of carbon dioxide on flow resistance is discussed. Pressure stress relaxation was decreased by 14 per cent with the addition of carbon dioxide.

Comparison of electrical and mechanical recording of spontaneous and evoked muscle activity. the clinical value of continuous recording as an aid to the rational use of muscle relaxants during anesthesia.

Abstract: The electrical and mechanical responses of peripheral skeletal muscle to nerve stimulation, and the integrated abdominal electromyogram were studied during anesthesia and operation to determine the feasibility of their routine use as a guide to the administration of neuromuscular blocking agents. The integrated electromyogram provided a good guide to the degree of relaxation produced by anesthetic agents, as well as the neuromuscular blockers. The electrical and mechanical responses of the muscle to nerve stimulation were not significantly modified by the anesthetics but were affected by the neuromuscular blockers. The mechanical response of the muscle to nerve stimulation was found to be the most accurate, convenient and useful guide to the administration of the neuromuscular blockers. Extensive experience with the routine use of a nerve stimulator during anesthesia and operation led to the conclusion that any time a neuromuscular blocking agent is given, the use of a nerve stimulator to monitor the effects should seriously be considered.

Interstitial fluid pressure

Abstract: Fluid movement through the capillary membrane has been measured in the lower legs of dogs by using implanted, perforated capsules as internal plethysmographs. Utilizing this procedure it was possible to compare the effects of changes in interstitial fluid pressure with the effects of changes in venous pressure and arterial pressure on movement of fluid through the capillary membrane. A decrease in interstitial fluid pressure of 1 mm Hg increased the filtration of fluid out of the capillaries 1.20 as much as did 1 mm Hg increase in venous pressure. The filtration coefficient for fluid movement through the capillary wall per unit change in interstitial fluid pressure was 0.058 μliter/min per mm Hg per g of tissue. This value is in the same range as filtration coefficients that others have determined following changes in capillary pressure.

Effects of diethyl ether and halothane on firefly luciferin bioluminescence.

Abstract: The intensity of bioluminescence from firefly lantern extracts elicited by the addition of ATP has been reported to be proportional to the amount of added ATP. The intensity of bioluminescence elicited by the addition of 2.0 X 107 mole ATP to a solubilized fraction of firefly lantern homogenate was decreased by administration of diethyl ether or halothane. Relative intensity of bioluminescence decreased linearly when plotted against the logarithmic scale of the concentrations of the anestheties. With 6 per cent diethyl ether the dose-response curve for ATP concentration and light intensity was shifted to the right parallel to the control.The inhibition of bioluminescence by anesthetics was reversed to control value by elimination of the anesthelic from the medium.

Pulmonary Compliance During Anesthesia

Abstract: Dynamic pulmonary compliance was measured in adult patients, first awake and then during halothane anesthesia under various conditions. Patients were free from respiratory obstruction and excessive inflation of the lungs during all measurements. Compliance decreased approximately one-third during deep anesthesia. During light anesthesia and emergence when tidal exchange approximated control values, there was less decrease in compliance. The occurrence of pulmonary atelectasis during deep anesthesia in spontaneously breathing patients is suggested. This may be the primary reason for decreased compliance during anesthesia. Compliance decreased in the conscious state in changing from the sitting to supine position. Men had higher measurements both awake and anesthetized than women, and greater decreases during anesthesia. A thiopental induction was associated with more of a decreased compliance than an inhalation induction. Thin patients encountered little change during anesthesia compared with normal and obese patients. During positive-pressure breathing compliance was lower than measurements during spontaneous respiration.

Evaluation of methods employed in the treatment of the chemical pneumonitis of aspiration.

Abstract: The object of the study was to examine the efficacy of methods used in handling the aspiration syndrome. Fifty animals, grouped in two series, were studied. The first series (26 cats) served to establish the amount of 0.1 N HCl producing inflammatory changes and the time of their occurrence, and to ascertain whether the liquids and drugs used for instillation into the tracheo-bronchial tree produce morphologic changes in the lungs. The second series (24 cats) served to determine the therapeutic efficacy of instilling the aforementioned solutions and drugs after instillation of hydrochloric acid. The results obtained and a review of the experiments of others suggest that the treatment of aspiration chemical pneumonitis should be carried out by immediate instillation of small quantities of highly concentrated hydrocortisone into the tracheobronchial tree with supporting intramuscular or intravenous injections of that drug in the postoperative period, and simultaneous administration of antibiotics.