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Reactivity of the cardiovascular system in the tetraplegic patient
Author(s) -
Sommers De Klerk
Publication year - 1979
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1002/cpt1979263344
Subject(s) - medicine , anesthesia , propranolol , supine position , blood pressure , spinal cord , sympatholytic , heart rate , guanethidine , cardiology , stimulation , psychiatry
The mechanism responsible for the gradual improvement in blood pressure control in tetraplegic subjects is not known. This study was undertaken to determine the presence of sympathetically induced inotropic effects on the heart in these patients. Eleven male patients with clinically complete traumatic cervical spinal cord lesions were studied. Measurement of the systolic time intervals was used to assess left ventricular function before and after the administration of the following sympatholytic drugs: propranolol, labetalol, phenoxybenzamine, and guanethidine. Propranolol was also administered after a blocking dose of atropine. An attempt was made to elicit sympathetic activity by performing 30° passive head‐up tilting and by the sublingual administration of 0.5 mg nitroglycerin. In the tetraplegic patient, propranolol increases the preejection periodlleft ventricular ejection time (PEP ILVET) ratio and PEP and total electromechanical systole (QS 2 ) indices, thus demonstrating more or less normal adrenergic tone on the heart in the supine position. The results after tilting and the administration of glyceryl trinitrate fail to support the existence of postural cardiovascular reflexes operating via the isolated spinal cord in tetraplegic patients. The improved cardiovascular responses that occur with time are, therefore, probably brought about by an increase in inherent myogenic activity which elevates the level of the basal vascular tone.