Response of the Limb Vascular Bed in Man to Intrabrachial Arterial Infusions of Hypertonic Dextrose or Hypertonic Sodium Chloride Solutions

Abstract

Infusions of hypertonic dextrose or NaCl solutions reduce resistance in several vascular beds of experimental animals. To study the response in man, 60 intrabrachial arterial jet infusions of hypertonic dextrose solution or hypertonic NaCl solution, each at 3 dose levels (1, 2, and 4 milliosmols/min), were made in 19 male student volunteers aged 21 to 29 years. Limb blood flow was measured by continuous infusion indicator-dilution, and vascular resistance calculated as mm Hg/ml flow/100 cm 3 limb vol/min. Measured increases in ipsilateral cephalic venous plasma osmolarity and serum dextrose and sodium concentrations during hypertonic infusions ranged from 7 to 30 milliosmols/liter, 153 to 481 mg/100 ml and 4 to 19 mEq/liter, respectively. Measured limb venous blood hematocrit during hypertonic infusions was similar to that during control isotonic infusions. All 60 hypertonic infusions evoked an increase in limb blood flow and decrease in limb vascular resistance as compared to "resting" values during paired control isotonic NaCl infusions. There was a significant (P<.01) positive linear correlation between level of initial vascular resistance and magnitude of response to all hypertonic infusions. At each dose level, neither regression coefficient nor regression adjusted mean response to dextrose was significantly different from that to hypertonic NaCl (P>.05). The results of these studies indicate that the local vascular response to hypertonicity in the limb of man is a decrease in resistance, the magnitude of which is a function of the level of plasma osmolarity and the level of initial limb resistance. The steady-state responses to hypertonic dextrose are quantitatively similar to those to hypertonic NaCl.