Benjamin E. Etsten

Characterization and clinical application of the "significance band" for acute respiratory alkalosis.

Abstract The acid-base composition of plasma during hypocapneic anesthesia in man has been used to construct a 95 per cent significance band defining the acute steady-state response to reduced carb...

The Role of the Venous System in Cardiocirculatory Dynamics during Spinal and Epidural Anesthesia in Man

Effects of spinal and epidural anesthesia uncomplicated by premedication or surgery were studied in 20 normal subjects. Venous blood flow, vascular resistance and venous distensibility of forearm and calf vessels were measured simultaneously before and after induction of spinal or epidural anesthesia. In anesthetized calf vessels, blood flow and vascular distensibility increased and vascular resistance decreased. Changes in cardiac output, whether decreased, increased or unchanged, did not affect the ratio of calf blood flow to cardiac output, which in all instances increased following spinal and epidural anesthesia. Changes in arterial blood pressure did not correlate with changes in cardiac output alone or changes in total peripheral resistance alone. However, changes in arterial blood pressure correlated with the interaction of changes in cardiac output and changes in total peripheral resistance. Evidence presented indicates that arterial hypotension induced by either spinal or epidural anesthesia may be due primarily to increased vascular distensibility of capacitance vessels and secondarily to decreased resistivity in pre- and postcapillary resistance vessels in the anesthetized area.

The Effect of Ēthrane on Cardiac Muscle Mechanics

The inotropic effect of Ēthrane on the intrinsic contractile stale of the cat papillary heart muscle was studied in terms of mechanics of contraction. Negative inotropic responses to Ēthrane were compared with those of methoxyflurane and halothane. Ēthrane caused dose-dependent decreases in maximal velocity (Vmax), peak force (Fm), power, and work during isotonic contraction, and was less depressant than halothane and methoxyflurane. A greater concentration of Ēthranc (11 mg/100 ml) was required to produce the same degree of depression (50 per cent) in myocardial power as either methoxyflurane (4 mg/100 ml) or halothane (3 mg/100 ml). Similarly, a 50 per cent reduction in Vmax required a higher concentration of Ēthrane (233 per cent more than halothane and 18 per cent more than methoxyflurane). Therefore, Ēthrane was less depressant to myocardial contractility than methoxyflurane or halothane. Probable mechanisms and significance of the change in the active state resulting from anesthetics are discussed.

Mechanics of respiration in apneic anesthetized infants.

The mechanics of respiration were studied during nitrous-oxide halothane anesthesia in 15 apneic infants (weight range, 2.2-5 kg.) ventilated by a time-cycled constant flow ventilator. The dynamic lung-thorax compliance was 2.8 ± 0.3 ml./cm. of water. The dynamic lung compliance was 3.3 ± 0.3 ml./cm. of water and the dynamic chest wall compliance was 22.3 ± 3.5 ml./cm. of water. The inspiratory airway resistance (including tissue viscous resistance) was 63.9 ±3.7 cm. of water/liter/second. The calculated inspiratory work was 6,499 ± 567 g. cm./minute. The elastic inspiratory work was 4,697 ± 427 g. cm./minute. Seventy-two per cent of the total inspiratory work was done against elastic forces. The static total, lung and chest wall compliances were determined in the same infants and did not differ significantly from the corresponding dynamic values. Substituting the determined values for compliance and resistance in a simplified equation of motion for the lung thorax, it was found that the pressures required for inflation of the lung in anesthetized infants are in the same range as in adults.

Effects of anesthesia upon the heart.

Abstract The direct and indirect effects of anesthetic agents and technics upon the heart are evaluated herein. There is very little evidence that cardiac function is depressed during light and moderate levels of anesthesia in the normal human subject. However, myocardial depression may occur during the deeper levels of anesthesia or when associated with other stresses such as anoxia, hypercarbia, hypotension and impaired adrenal function, or after the administration of other circulatory depressant drugs such as reserpine. The ability of a cardiac patient to withstand anesthesia is directly related to his cardiac reserve and other disease conditions. Generalizations contraindicating the use of any one anesthetic drug are unwarranted. The choice of anesthetic agent is entirely dependent upon evaluation of the individual patient and the ability of the anesthesiologist to maintain blood gases (oxygen saturation, pH and pCO 2 ) within physiologic levels during light anesthesia.

Decreased Adrenal Venous Catecholamine Concentrations during Methoxyflurane Anesthesia

Plasma catecholamine concentrations were determined in adrenal venous and arterial blood samples withdrawn simultaneously from dogs before, during and after methoxyflurane anesthesia. During light anesthesia and at deeper levels, the adrenal venous concentrations of both epinephrine and norepinephrine were reduced significantly. Decreases were directly proportional to depths of anesthesia. Adrenal venous catecholamine concentrations increased during the recovery period, with wide variance from dog to dog. The findings indicate that methoxyflurane has a depressive effect on the sympathoadrenal system.There was no significant change in arterial catecholamine concentration, nor a significant correlation between adrenal arterial and venous catecholamine concentrations before, during or after anesthesia. It is evident that the arterial concentration of catecholamines is not a valid indicator of the neurohormonal effects of anesthesia.

Hemodynamics of mephentermine in man.

THE clinical use of mephentermine¶ to elevate the arterial-blood pressure in man is presumably based upon the rationale that its pressor action is primarily due to an increase in myocardial contrac...

Effect of Halothane on Force-Velocity Relations and Dynamic Stiffness of Isolated Heart Muscle

The effect of halothane on isometric and isotonic contraction of isolated cat papillary muscle was studied employing the Hill model of muscular contraction. Maximal velocity of shortening and maximal force both were depressed by increasing halothane concentrations, resulting in successive downward shifts of force-velocity curves. Net shortening, power and work of isotonic contraction also exhibited a dose-dependent depression. Dynamic stiffness of the series elastic element of the myocardium was unaltered by halothane. The findings indicate that the negative inotropism induced by halothane is the result of a dose-dependent depression of the intensity of energy conversion by the contractile element of heart muscle.

The effect of methoxyflurane on the inotropic state of myocardial muscle.

The direct effect of methoxyflurane upon the inotropic state of the myocardium was studied in an isolated cat papillary heart muscle preparation. Methoxyflurane decreased muscle ability to develop force and shorten and the velocity of shortening for a given load (power). The decrease in the inotropic state of muscle was dose-dependent, as evidenced by progressive decreases in maximum velocity of myocardial muscle shortening (Vmax) power, and work. Methoxyflurane also caused changes in the active state of the myocardium (force-generating processes), as shown by decreases in maximum rate of force development (dF/dt) and time-to-peak isometric force (TTFm). The results suggest that methoxyflurane exerts a negative inotropic effect on the intrinsic contractile state of cardiac muscle owing to alteration in the mechanical energy derived from chemical reactions within the contractile system.

The Inotropic Effect of Cyclopropane Anesthesia upon the Intact Dog Heart

The effect of cyclopropane anesthesia on the intrinsic state of the myocardium of the intact heart was determined by means of force-velocity relations in 14 dogs. The maximal intrinsic velocity (Vmax), an index of myocardial contractility, was obtained before and during anesthesia by extrapolating either the force-velocity curve using stress calculation or the isovolemic force-velocity curve using the simplified formula of (dP/dt)/kp as the contractile element velocity. Cyclopropane (arterial blood concentration ranging from 9 to 46 mg/100 ml) did not cause any significant change in either shape or position of the force-velocity curves. The average change in Vmax was −6 per cent (P > 0.2). These findings indicate that cyclopropane anesthesia does not alter myocardial contractility.