Physical counterpressure maneuvers
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
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. Crossing ones legs is often applied unintentionally also by healthy humans when standing for prolonged periods (cocktail party posture). Recent studies show that instruction to apply physical countermaneuvers is very helpful to otherwise healthy subjects with functional orthostatic disorders like the postural tachycardia syndrome (Fig. 3). The combination of legcrossing and tensing of leg and abdominal muscles can abort an impending vasovagal reaction (Fig. 4).
Squatting
Squatting increases arterial mean pressure and pulse pressure by two mechanisms.
- First, blood is squeezed from the veins of the legs and the splanchnic vascular bed, which increases cardiac filling pressures and cardiac output.
- Second, the mechanical impediment of the circulation to the legs increases systemic vascular resistance.
Squatting is an effective emergency mechanism to prevent a loss of consciousness when presyncopal symptoms develop rapidly both in patients with autonomic failure and in patients with vasovagal episodes. Bending over as if to tie ones shoes has similar effects and is simpler to perform by elderly patients. The beneficial effects of sitting in knee-chest position or placing one foot on a chair while standing (Fig. 1) are comparable to squatting. When arising again from the squatted position immediate leg muscle tensing should be advised in order to prevent hypotension.
External Support
Applying external pressure to the lower half of the body substantially reduces venous pooling when upright, and consequently arterial pressure and cerebral perfusion are better maintained. External support can be applied by bandages firmly wrapped around the legs, or a snugly fitted abdominal binder, but is best accomplished by a custom-fitted counterpressure support garment, made of elastic mesh, which forms a single unit extending from the metatarsals to the costal margin. External support garments are helpful in the treatment of a patient with incapacitating orthostatic hypotension, but have the disadvantage that the motivation of the patient must be strong, since they are uncomfortable to wear. In addition, counterpressure support garments prevent the formation of peripheral edema in the legs, which is considered to be an essential factor for effective therapy of orthostatic hypotension by acting as a perivascular water jacket that limits the vascular volume available for orthostatic pooling. We, therefore, only use an abdominal binder as a temporary external support expedient to achieve mobility in our most severely affected patients. Small lightweight portable fishing chair or a derby chair, which is a cane when folded but a seat when unfolded are useful mechanical aids for severely affected patients. They enable the patients to sit for brief periods when presyncopal symptoms develop during standing. The lower the chair the more pronounced is the effect on blood pressure (Fig. 2).