Blood pressure (BP) is an index of some of the most fundamental physiological processes in the body, and an understanding of arterial blood pressure and its measurement is essential for the accurate determination of physiological processes and disturbances. Neurogenic shock occurs when the sympathetic nervous system supply to the cardiovascular system is blocked, causing a low cardiac output, reduced peripheral resistance and venous blood pooling. Post-operative observations are critical to the patient's full recovery, and BP checks are paramount among these. Low or a falling blood pressure after surgery may indicate blood loss is occurring, either internally or externally, and should be reported and acted on quickly. The question concerning accuracy of blood pressure arises because of the possible variability that must occur within the same individual at different times and circumstances. Abnormalities of systemic blood pressure means either the pressure is too high (hypertension) or too low (hypotension).