Vagal Blockade Research Articles

Effects of Diethyl Ether on Ventilation with or without Vagal, Somatic and Sympathetic Blockade in Dogs

Effects of Diethyl Ether on Ventilation with or without Vagal, Somatic and Sympathetic Blockade in Dogs

HEART RATE DURING CONDITIONING IN HUMANS: EFFECTS OF UCS INTENSITY, VAGAL BLOCKADE, AND ADRENERGIC BLOCK OF VASOMOTOR ACTIVITY.

HEART RATE DURING CONDITIONING IN HUMANS: EFFECTS OF UCS INTENSITY, VAGAL BLOCKADE, AND ADRENERGIC BLOCK OF VASOMOTOR ACTIVITY.

COMPARISON OF SALIVARY SUPPRESSION BY INTRAVENOUS AND SUBCUTANEOUS ATROPINE BEFORE E.C.T.

Clements (1962) has shown that atropine given intravenously has a vagal blockage effect superior to that achieved by subcutaneous injection. Electroconvulsive therapy is such a frequent reason for inducing general anaesthesia that a knowledge of the best premedication technique to use seemed to us important. Clearly the cardiovascular protective effect of the atropine is more important than the suppression of salivation. Maclay (1953) reported that in 62 deaths after E.C.T., 19 (30.6 per cent.) were attributable to the respiratory system. Clement's findings (1962) suggest that vagal blockade is adequate in protecting against cardiovascular disturbance 75 seconds after the injection of 1 mg. of atropine intravenously, but he mentions that the antisialogogic action is reputed to take longer to develop, and his paper did not include an assessment of this action.

Influence of vagal blockade on respiratory and circulatory functions in hypothermic dogs

Anatomical and physiological dead spaces were enlarged as a result of reduction in body temperature to 28 C in spontaneously respiring anesthetized dogs. Respiratory dead space at 32 C was not significantly different from that at normal body temperature. Vagal blockade resulted in an increase in tidal volume and decrease in respiratory frequency and increased anatomic and physiologic dead space at normal and reduced temperatures. Alveolar ventilation and cardiac output declined equally (percentagewise) with reduction in body temperature to 32 C; at 28 C alveolar ventilation fell more precipitously so that alveolar ventilation-cardiac output ratio (ventilation-perfusion) at 28 C was approximately one-half that at 37 and 32 C. Arterial-alveolar carbon dioxide pressure differences were independent of temperature and vagal blockade. The results indicate no impairment of gas transport or gas exchange at 32 or 28 C in spontaneously respiring anesthetized dogs. Submitted on January 11, 1962

Some factors affecting the fetal heart rate

A phonocardiograph was used to investigate factors influencing fetal heart rate in utero. The use of this instrumentation is described. All data recorded were obtained by crude measurements of paper tapes or semiautomatically from magnetic tapes and a more sophisticated method of data reduction is presently being developed. Normal mothers were submitted to various stimuli to test their effect on maternal and fetal heart rate. The responses to inhalation of 100% and 12% oxygen were inconstant. There was no fetal response to administration of epinephrine or of norepinephrine. Atropine produced vagal blockade and tachycardia in both the mother and the fetus. There was a significant time dalay between the maternal and fetal response (e.g. Case 1 130 seconds for mother and 1290 seconds for fetus). This was of such duration as to allow time for the drug to cross the placenta and blockade the fetal vagus. Cigarette smoking produced fetal and maternal tachycardia. This response had a short time delay similar to that produced by fright. It may be caused by a reduction in uterine blood flow. It may be that accurate measurements of the parameters of such responses in normal and abnormal gravidas can serve as a test for fetal well-being and the adequacy of placental transfer.

Vasodepression to intravenous acetylcholine with attendant vagal blockade ? a study of atropine resistance

N,N-di-isopropyl-N′-isoamyl-N′-diethylaminoethylurea (P-286) and congeners abolished the vasodepressor response to vagal stimulation with little effect on that to intravenous acetylcholine. This effect, although suggestive of parasympathetic ganglionic blockade, was found to be consistent with weak atropine-like activity.

Influence of vagal blockade on respiratory work in the hypoxic and hypercapneic anesthetized dog.

The mechanical work of breathing was determined in anesthetized dogs by measurements of intrathoracic pressures and tidal volumes, during inhalation of various gas mixtures while vagi reflexes were functional (warm) and blocked (cool). Pressure-volume loops obtained when vagi reflexes were blocked showed that both elastic and viscous work per breath increased during inhalation of 3.8% and 5.2% CO2. However, the total work per minute increased during inhalation of 3.8% CO2, but remained constant during inhalation of 5.2% CO2. During inhalation of 10.1% O2 in nitrogen, viscous and elastic work per breath increased when vagi were blocked, with no significant changes in total work per minute. When 6.39% O2 in nitrogen was inhaled, elastic and viscous work per breath increased with blocked vagi, but a significant decrease in total work per minute occurred. Vagal reflexes do not have as prominent a role in influencing the work of breathing during severe hypoxia and hypercapnia as they do during normal and obstructive breathing. Submitted on November 20, 1958