Alan D. Sessler

The Function of Each Lung of Anesthetized and Paralyzed Man during Mechanical Ventilation

Intrapulmonary gas distribution of individual lungs was studied in five healthy anesthetized, paralyzed, and mechanically ventilated adult volunteers in the supine and both lateral decubitus positions. Comparison of the results with previous findings in conscious and spontaneously-breathing man indicated that the distribution of inspired gas during mechanical ventilation in anesthetized subjects is different. Inspired gas was more uniformly distributed within the individual lungs of mechanically ventilated anesthetized subjects in the supine position. There was a preferential distribution of tidal volume to the nondependent lung, in contrast to the preferential ventilation of the dependent lung in conscious, spontaneously-breathing man in the lateral position. Although relative end-expiratory lung volumes (that is, functional residual capacity) of individual lungs in persons ventilated mechanically in both positions were similar to those reported for the conscious, spontaneously-breathing subject, preferential ventilation of the nondependent lung and lesser ventilation of the dependent lung resulted in similar nitrogen clearances from the two lungs when the subjects were in the lateral position. This finding is in contrast to the significant differences between nitrogen clearances of the two lungs in spontaneously-breathing man in the lateral position.

Effects of Isoflurane Anesthesia and Muscle Paralysis on Respiratory Mechanics in Normal Man

In five healthy adult male volunteers in the supine position, respiratory mechanics and functional residual capacity (FRC) were studied in the awake state (control) and with muscle paralysis and mechanical ventilation during isoflurane anesthesia (inspired concentrations, 1 and 2 per cent). In eight of nine instances, FRC was less during isoflurane anesthesia compared with control. Static compliance of the total respiratory system (Crs) decreased consistently during anesthesia and that of the lung (Ct) decreased in eight of nine instances; static compliance of the chest wall (Cπ) did not change. Average pulmonary resistance (Rl) was significantly higher during anesthesia. The decrease in FRC and increase in Rl appear to be somewhat less than those reported for other anesthetics. Increasing the inspired isoflurane concentration to 2 per cent had no further significant effect on FRC, Crs C19 Cl and Rl Arterial blood pressure was decreased significantly and heart rate remained unchanged during anesthesia with I per cent isoflurane; with 2 per cent isoflurane, blood pressure was further significantly decreased and heart rate did not change significantly.

Function of each lung during mechanical ventilation with ZEEP and with PEEP in man anesthetized with thiopental-meperidine.

Differential lung function was studied in seven healthy adult volunteers who were anesthetized, paralysed, and mechanically ventilated. After initial measurements during ventilation with positive end-expiratory pressure (PEEP), studies were repeated during ventilation with zero (ambient) end-expirat

The circulation in anaesthesia

SummaryThe integrity of the circulation depends on the summation of the effects of the cardiac output, the peripheral vascular resistance, and the blood volume. Agents producmg general anaesthesia affect the circulation by decreasing cardiac output and peripheral resistance, this effect is in proportion to the concentration of agents in the blood. Other factors which may alter the circulation in anaesthesia are the status of ventilation, the degree of hypoxia, the administration of relaxants, and the occurrence of metabolic acidosis. Along with the usual clinical means of evaluating the circulation, venous pressure values are helpful data. These values permit differentiation between a problem in which myocardial function needs improvement and one in which blood volume can be safely increased to treat an inadequate circulation.RésuméĽintégrité de la circulation dépend de la somme des effets du débit cardiaque, de la résistance périphérique et du volume sanguin. Les substances qui produisent ľanesthésie générale affectent la circulation en dimmuant le débit cardiaque et la résistance périphérique, ces effets sont directement proportionnels à la concentration de ces substances dans le sang. Les autres facteurs qui peuvent modifier la circulation, au cours de ľanesthésie, sont le volume de la ventilation, le degré ďhypoxie, ľadministration de myorésolutifs et ľapparition ďacidose métabolique. En plus des signes cliniques usuels sur lesquels nous nous basons pour évaluer la circulation, la pression veineuse peut fournir de précieux renseignements. Ses données permettent de fane le diagnostic entre une situation où le myocarde a besom de support et une situation où le volume sanguin peut être augmenté en toute sécurité pour corriger une circulation inadéquate.

The Effects of Thiopental-Meperidine Anesthesia with Succinylcholine Paralysis on Functional Residual Capacity and Dynamic Lung Compliance in Normal Sitting Man

Functional residual capacity (FRC) and dynamic lung compliance [C4ya(2)] were measured in ten normal sitting subjects while conscious and again during thiopental-meperidine anesthesia with succinylcholine paralysis and mechanical ventilation. At similar tidal volumes and respiratory frequencies, no significant changes in FRC and Cdya(1) were observed. Mean FRCs were 3.26 ± 0.26 (SE) liters and 3.29 ± 0.24 (SE) liters and mean values for C(1) were 182 ml/cm IL-O (SE ± 25) and 153 ml/cm H-O (SE ± 34) in conscious and anesthetized paralyzed subjects, respectively. The results suggest that the reductions in FRC and C(1) previously observed in supine anesthetized subjects are not the result of a direct pharmacologie effect of thiopental-me-peridine anesthesia on the lung.

Effects of mechanical ventilation, muscle paralysis, and posture on ventilation-perfusion relationships in anesthetized man.

Ventilation-perfusion relationships of the fast ventilated and slowly ventilated compartments of the lung were estimated from analysis of nitrogen clearance curves and rate of increase of arterial oxygen tension during nitrogen clearance. Six subjects were studied first awake, breathing spontaneously, and then again during anesthesia, muscle paralysis, and mechanical ventilation in the supine position. Five other subjects were studied in the lateral position, first awake and then during anesthesia. Induction of general anesthesia, muscle paralysis, and mechanical ventilation did not significantly alter the mean ΔPetN2/ΔPao2 ratio in supine subjects; this suggests no increased difference between the ventilation-perfusion ratios in the fast ventilated and slowly ventilated compartments. This conclusion is supported by data that showed no significant increase in arterial-alveolar CO2 tension difference, alveolar deadspace, or shunt. Unlike the ratios for awake subjects in the lateral position, the ΔPetN2/ΔPao2 ratios decreased consistently after induction of anesthesia. In the awake lateral subjects, mean ΔPetN2/ΔPao2 was 0.08 above unity, whereas in the anesthetized lateral subjects, the mean value was 0.25 below unity; this suggests a larger difference between the ventilation–perfusion ratios in the two compartments. Also, arterial–alveolar CO2 tension difference and alveolar deadspace increased significantly after induction of general anesthesia in the lateral subjects.

Effects of Halothane Anesthesia on Rate of Canine Oxygen Consumption

In dogs anesthetized with halothane, increase in halothane concentration from 0.8 to 2.5 per cent (mean expired) was accompained by a 17 per cent reduction in O2 consumption (Vo2) and a halving of cardiac output (Q) and arterial pressure. Repayment of an O2 debt was not observed with return to 0.8 per cent halothane were reduced by measures that reduced Q and arterial pressure (vagal and paired pulse stimulation). Conversely, Vo2 at 1.7 per cent halothane was increased by maneuvers that increased Q and arterial pressure (digitalis and blood or dextran administration). Change in myocardial Vo2 alone is believed to be insufficient to account for the observed changes in whole-body Vo2. Accordingly, the reductions in Vo2 observed with increased halothane concentration may represent indirect effects mediated by halothane-induced changes in the circulation although direct metabolic depressant effects of halothane per se were not ruled out.

Normothermia versus hypothermia for whole-body perfusion: effects on myocardial and body metabolism.

RIOR TO the advent of the pump-oxyP genator for whole-body perfusion, hypothermia by surface cooling was one of the few techniques available for accomplishing intracardiac operations.1-4 In the initial era of whole-body perfusion, in children the body temperature invariably decreased in spite of efforts to maintain the temperature of blood in the extracorporeal circuit.5 When the heat exchanger was introduced into the extracorporeal circuit, by Brown and co-workers6 in 1958, control of the temperature of perfusate and patient became possible. Some groups use the heat exchanger to effect hypothermia so that the rate of perfusion can be decreased.7 We originally used it simply to maintain normothermia during perfusion,* but now we combine hypothermia with full perfusion flow. Some groups do not use a heat exchanger at all.

The effect of dead-space rebreathing on postoperative atelectasis.

YPOXEMIA is a common finding after H general anesthesia.’ Shunting resulting from miliary atelectasis may exist in the absence of detectable physical signs or positive roentgenographic chest findings.’.3 After operation, patients often breathe without sighing, and a constant tidal volume has been associated with the development of atelectasis.384 To prevent or reverse the process, periodic hyperinflation of the lungs, accomplished either mechanically or as a response to an increased inspired C02 tension, has been recommended. The addition of an artificial dead space has been the means most often used to increase the inspired concentration of C02 and to produce an increase in tidal volume and minute ventilation. Hyperventilation then, theoretically, should open collapsed alveoli and prevent ate1ectasis.s Nevertheless, reports on the effectiveness of this measure have been inconc l~s ive .3~~~~ In an effort to evaluate the therapeutic usefulness of rebreathing in postoperative patients, we studied the effect of added dead space on tidal volume, minute ventilation, blood gases, and shunting.

The legacy of Albert Faulconer Jr.

Monitoring the patient’s physiological status and the correct performance of anesthetic equipment are essential adjuncts to the clinical skill and vigilance of the anesthesiologist. Through the 1940s and 1950s, such monitoring mainly comprised clinical observations. This period also marks the origins of modern anesthesiology with its emphasis on innovation through scientific inquiry (1). A largely forgotten pioneer in this era was Albert Faulconer Jr whose research was primarily directed at improving patient care during general anesthesia. Among his accomplishments, he was the first to continuously measure anesthetic gas and vapor concentrations during surgery and to explore using the electroencephalogram (EEG) as an index of anesthetic depth. This review examines Dr Faulconer’s scientific work and his other contributions to the specialty and explores their relevance to modern anesthesiology.