Physical counterpressure maneuvers: Difference between revisions

Specific treatment of the underlying disease in patients with autonomic failure is usually not possible and consequently the goal in management is to obtain symptomatic improvement by other means. Physical maneuvers that are both easy to apply and effective in combatting orthostatic lightheadedness in daily life are, therefore, of obvious importance. Patients with autonomic failure have discovered several such maneuvers themselves. The beneficial effects of leg-crossing, squatting, abdominal compression, bending forward, and placing one foot on a chair have been described.  A great advantage of these maneuvers is that they can be applied immediately at the start of hypotensive symptoms. Physical countermaneuvers need to be related specifically to the individual patient. They may be difficult to perform in patients with multiple system atrophy, who may have motor disabilities and compromised balance.

Leg-crossing is the simplest maneuver to increase the standing time in a patient with autonomic failure. It has the advantage that it can be performed without much effort and without bringing much attention to the patient's problem. The maneuver is performed by crossing one leg in direct contact with the other while actively standing on both legs (Fig. 1). The increase in mean arterial pressure and pulse pressure induced by leg-crossing can be attributed to compression of the muscles in the upper legs and abdomen with mechanical squeezing of venous vessels resulting in an increase in central blood volume and thereby in cardiac filling pressures and cardiac output. Tensing of leg and abdominal muscles can increase this effect considerably (Fig. 2),  most likely by the combination of a further increase in venous return and the mechanical effects of skeletal muscle tensing on the arterial circulation to the legs increasing systemic vascular resistance. Legcrossing  can also be used for the prevention of orthostatic lightheadedness in the sitting position (Fig. 1).

Although the increase in upright blood pressure induced by leg-crossing alone is relatively small with an average increase in mean arterial pressure of 10-15 mm Hg (Figs. 1 and 2), one should realize that medical treatment with fludrocortisone, erythropoietin, and midodrine results in similarly small blood pressure increases. Despite these small increases the standing time improves markedly by all four methods, because they shift mean arterial pressure from just below to just above the critical Ievel of perfusion of the brain. A driving pressure of about 40 mm Hg is needed to maintain cerebral blood flow in young adult subjects in supine posture. Normal humans in the upright position need a mean arterial pressure of about 70 mm Hg measured at heart level in order to compensate for the effects of gravity on the circulation. Patients with orthostatic hypotension tolerate a much lower standing mean pressure occasionally as low as 50 mm Hg, probably by adaption of autoregulatory mechanisms of the blood vessels in the brain.