Limb suction evoked during arterial occlusion causes systemic sympathetic activity in humans

Abstract

-Venous saline infusions in an arterially occluded forearm evokes reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP). We hypothesized that the application of suction to the human limbs would activate this venous distension reflex and raise sympathetic outflow. We placed airtight pressure tanks and applied 100 mmHg negative pressure to an arterially occluded limb (occlusion and suction, O&S) to induce tissue deformation without fluid translocation. BP, heart rate (HR), and MSNA were assessed in 19 healthy subjects during 2 min of arm or leg O&S. Occlusion without suction served as a control. During a separate visit, saline (5% forearm volume) was infused into veins of the arterially occluded arm (n ϭ 13). The O&S increased limb circumference, MSNA burst rate (arm: ⌬6.7 Ϯ 0.7; leg: ⌬6.8 Ϯ 0.7 bursts/min), and total activity (arm: ⌬199 Ϯ 14; leg: ⌬172 Ϯ 22 units/min) and BP (arm: ⌬4.3 Ϯ 0.3; leg: ⌬9.4 Ϯ 1.4 mmHg) from the baseline. The MSNA and BP responses during arm O&S correlated with those during leg O&S. Occlusion alone had no effect on MSNA and BP. MSNA (r ϭ 0.607) responses during arm O&S correlated with those evoked by the saline infusion into the arm. These correlations suggest that sympathetic activation during limb O&S is likely, at least partially, to be evoked via the venous distension reflex. These data suggest that suction of an occluded limb evokes sympathetic activation and that the limb venous distension reflex exists in arms and legs of normal humans.autonomic; blood pressure regulation; vessel PRIOR STUDIES HAVE SHOWN THAT the distension of abdominal veins increases sympathetic efferent activity in rabbits (2) and dogs (12). Limb venous ligation evokes vasoconstriction in both the occluded and contralateral extremities in dogs (5). Evidence in animals suggests that afferent nerve endings in peripheral veins may sense regional blood volume changes and, in turn, contribute to the blood pressure (BP) regulation via a reflex response in cats (11, 21), rabbits (2), and dogs (12). Venous distension increases the discharge of group III and IV afferent nerves in cat hindlimbs (18).Our recent reports (7-10) have shown that volume infusion (saline or albumin solution, 5% forearm volume, ϳ50 ml) into the veins of an occluded forearm evokes reflex increases in muscle sympathetic nerve activity (MSNA) and BP in human subjects. The magnitude of the MSNA and BP responses depends on the volume and the rate of the infusate during arm vein distension (8). When lidocaine is added to the forearm infusate, the MSNA and BP responses to venous distension are abolished (9). These observations clearly suggest that limb venous distension evokes a sympathoexcitatory reflex (termed venous distension reflex) and, thus, increases BP in humans. Of note, a recent report by Yamauchi et al. (33) has shown this reflex is also present in rats. Additionally, we have shown that venous infusion of albumin evokes a larger and more sustained increase in MSNA and BP than those with infusion of equal vo...

Peripheral venous distension elicits a blood pressure raising reflex in young and middle-aged adults

“…Furthermore, infusion of albumin to raise venous osmotic pressure causes a greater and more sustained response, indicating that intravascular venous distension, and not an increase in interstitial fluid volume, is the stimulus for the response (6). Additionally, the venous distension response is related to the responses of arm and leg suction during circulatory occlusion (2). This suggests that similar venous distension mechanisms exist in the upper and lower extremities.…”

“…While the data in humans are limited to only a few studies (2)(3)(4)(5)(6), there is evidence that peripheral venous distension elicits sympathoexcitation and increases blood pressure. For example, Cui et al (5) found that saline infusion into an antecubital vein of an occluded limb resulted in a nearly twofold increase in muscle sympathetic burst frequency.…”

Muscle sympathetic nerve activity and hemodynamic responses to venous distension: does sex play a role?

“…Collectively, these findings suggest that the venous distension reflex in the legs may be involved in orthostatic intolerance in women. Because of the smaller volume of the forearm, it was easier to study the venous distension reflex in the forearm, but given the evidence of correlated responses between arms and legs (7), it is likely that the same outcomes would be found had we performed venous distension in the legs.…”

Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans

“…Recent studies by Sinoway and colleagues (10,32) showed that distension of veins in the limbs can induce reflex vasoconstriction and systemic pressor responses. If this response occurred during application of negative pressure in the present study, it could offset the decrease in systemic pressor responses during exercise elicited by increases in LBF.…”

“…However, those studies also suggest that substantial venous congestion, distension of the veins, and/or tissue deformation within the leg is needed to induce systemic pressor responses. For example, Cui et al (10) showed that application of Ϫ100 mmHg to an arterially occluded leg increases muscle sympathetic nerve activity and induces a ϳ9 mmHg rise in MAP. In addition, Lott et al (32) demonstrated that application of Ϫ25 mmHg or Ϫ50 mmHg to one leg without occlusion has no influence on MAP, while application of Ϫ75 mmHg or Ϫ100 mmHg to the leg without occlusion evokes small increases in MAP (ϳ2 mmHg with application of Ϫ75 mmHg and ϳ3 mmHg with application of Ϫ100 mmHg).…”