1222 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



Procolnt Block ©t PotHnor Tlt-lol N*rvt 



Sub>JM,35 WM 



FIG. iC 



Normally, venous filling starts within 30 sec. For this 

 maneuver to be valid as a test for arterial sufficiency, 

 the veins must be relatively normal with competent 

 valves. Venous valvular insufficiency is evidenced by 

 abrupt venous filling. 



Tests of vascular dilatability may be useful in the 

 evaluation of the cutaneous circulation. Reactive 

 hyperemia may be employed as such a test. The 

 techniques and mechanisms for this reaction are 

 discussed in detail elsewhere in this volume, but brief 

 comments may be in order. As originally recom- 

 mended (49, 77), the part to be tested is placed in 

 water at 35 C to 40 C for 10 min then removed and 

 raised above body level until pale. The purposes of 

 this procedure are to ensure that vessels in spasm are 

 relaxed and to empty the minute vessels of blood. A 

 sphygmomanometer cuff is then placed about the 

 part to be investigated and inflated to a pressure 

 above systolic blood pressure. The limb is then 

 returned to the water bath and maintained there for 

 5, 10, or even 15 min with the circulation arrested, if 

 tolerated by the patient. The limb is then lifted out 

 of the bath, dried, and its circulation released. In 

 normal limbs, the reactive hyperemic flush reaches 



the tips of the digits within 2 to 5 sec, becomes 

 maximal in 1 5 sec, then quickly fades. When organic 

 arterial occlusion is present, the flush spreads slowly, 

 is patchv in distribution, and may be delayed up to 

 a minute or so in reaching the tips of the fingers or 

 toes. When disease is present and the onset is delayed, 

 the flush lasts for much longer periods of time. More 

 quantitative methods such as plethysmography or 

 thermometry may be used to measure the reaction. 



Vascular dilatability may be tested by methods 

 which decrease lympathetic tone. For example, local 

 nerve block (figs. 1, 2A, B, and C) or paraverte- 

 bral and stellate sympathetic ganglionic nerve block 

 mav be employed with the responses of the circula- 

 tion being measured graphically by temperature 

 recordings, plethysmographic recordings, or other 

 means. Vasospastic states due to sympathetic nervous 

 activitv become evident from the recordings. In 

 normal subjects or in patients with functional vaso- 

 spasm, interruption of sympathetic activity results in 

 a rise in digital cutaneous temperature to approxi- 

 mately 32 to 35 C when the subject is at rest in a 

 comfortable environment. For obvious reasons, the 

 total rise above control levels is much greater in 



