Studies on Autonomic Blockade. I. Comparison Between the Effects of Tetraethylammonium Chloride (Teac) and High Selective Spinal Anesthesia on Blood Pressure of Normal and Toxemic Pregnancy 1

Abstract

Previous studies have indicated that autonomic blockade with tetraethylammonium chloride produces different effects in normal term pregnancy and in toxemia of pregnancy (1-4). In the former, a fall in the blood pressure to very low levels occurs, while in the latter the blood pressure fall is negligible. This led to the belief that in normal pregnancy the blood pressure is maintained mainly by neurogenic impulses, while in toxemic pregnancy the blood pressure is supported principally by humoral mechanisms. It was also suggested that a certain degree of venous pooling might be a contributing factor in the blood pressure fall following autonomic blockade with TEAC.Since recent reports (5)(6)(7)(8) extensive blockade achieved with higher concentrations of anesthetic solutions. MATERIALThe material consisted of 12 normal term pregnancies; 15 toxemic pregnancies (two cases with convulsive eclampsia, 11 with severe pre-eclampsia and two cases with pre-eclampsia superimposed on pre-existing essential hypertension); and five healthy, young normotensive non-pregnant females (medical students and paid volunteers). A total of 32 patients submitted to 66 high spinal and 73 TEAC tests (some of the patients had more than one test with both spinal and TEAC). The age of the patients ranged from 15 to 40 years, an average of 24.5 years. The diagnosis of pre-eclampsia and eclampsia was based on the same criteria as outlined by Brust, Assali, and Ferris (1). Of the 12 normal pregnant females, 10 patients were studied in the prepartum and postpartum periods; two refused the postpartum test. Among the toxemic group, 12 were studied in the prepartum and postpartum periods; three refused the postpartum test.In all normal pregnant patients the prepartum tests were performed between 33 and 40 weeks' gestation. The postpartum assays were done 36 to 48 hours after delivery. Toxemic patients were studied prepartum at the height of toxemic symptoms; in the postpartum period the study was performed when all signs of toxemia had subsided (only one patient had her postpartum test while she was still toxic). METHODAll of the patients were on the ward, without any medication, for at least 24 hours prior to the test. None was in labor. Both TEAC and spinal anesthesia studies were conducted with the patient lying in the supine position on an operating table which was maintained always in the horizontal position. Tilting of the table to obtain changes in the anesthetic level was not done because the anesthetic solution used was practically isobaric and its simple diffusion and dispersion in the spinal fluids were sufficient to obtain the desired level. The blood pressure was recorded by a mercury sphygmomanometer attached to one arm and maintained at heart level. Pulse rate was recorded at either radial or carotid artery.1354

The Effect of High Spinal Anesthesia on the Renal Hemodynamics and the Excretion of Electrolytes During Osmotic Diuresis in the Hydropenic Normal Pregnant Woman 1

“…The response of the blood pressure and pulse rate to the spinal blockade followed the same pattern described in other papers (1,2). It will be seen that the blood pressure dropped markedly during the first few periods following spinal anesthesia and began to return to control levels at the onset of the last period.…”

“…The pulse rate showed similar variation. The side effects of the procedure were the same as listed in other papers (1,2) Figure 1 it will be seen that these cases fit well on the flow-load curve as described previously (3) Renal plasma flow (RPF) . 5 The effect of spinal blockade on renal plasma flow is consistent for all five subjects.…”

“…Thus the immediate response to spinal anesthesia could be followed and observations continued until the blood pressure had almost returned to levels preceding the injection of the spinal anesthetic. Previous studies (3)(4)(5) employing osmotic diuresis with hypertonic mannitol solution in hydropenia, had shown that this technique was applicable to a short 1 This investigation was supported (in part) by research grants from the National Heart Institute of the National Institutes of Health, Public Health Service, and from Parke, Davis and Company, Detroit, Mich. 2Aided by grant from Eli Lilly and Company. 3 Fellow in Research, Department of Obstetrics, Cin.…”

“…(Submitted for publication May 21, 1951; accepted June 18, 1951) In previous papers (1,2) it was demonstrated that the normal pregnant woman subjected to autonomic blockade with high spinal anesthesia develops a marked fall in blood pressure leading to a shock-like state.…”

“…The water-conserving capacity of the kidney of the hydropenic individual could be studied both prior to induction of diuresis and following loading, using the standards of comparison which are defined by the flow-load relationship (3,5). Three patients received high selective spinal anesthesia to levels of C' with 0.2%o procaine solution according to the method described elsewhere (1). In the remaining two cases the anesthesia was achieved with 1% procaine solution and a complete motor paralysis to levels of T' was obtained.…”