Hyperaemia following arterial occlusion or exercise in the warm and cold human forearm

Postocclusive Reactive Hyperemia During Vascular Reconstruction

The purpose of this basic investigation was to clarify the postocclusive reactive hyperemia during vascular reconstruction using laser Doppler flowmetry (LDF). For the fundamental experiment, thirty-nine limbs with arteriosclerosis obliterans (ASO) in Stage II according to Fontaine's classification and 33 limbs without arterial or venous disease were chosen. In the supine position, a thigh cuff was applied to the lower thigh of a subject. Systolic Doppler thigh pressure was obtained and thigh/arm pressure index (TPI) was calculated. A LDF probe was then fixed to the bottom of the first toe and cutaneous blood flow was measured continuously before, during, and after femoral artery occlusion by the thigh cuff. The occlusion time was 3 and 6 minutes. For the clinical study, thirty-three lower limbs with arterial occlusive disease were selected. During the vascular surgery, the LDF probe was attached to the bottom of the first toe and cutaneous blood flow was monitored continuously before, during, and after the vascular clamping. In the fundamental experiment, after the release of the occlusion, the maximum blood flow of the reactive hyperemia (peak flow) appeared. The period between the release of the occlusion and the peak flow was called the peak time. When the occlusion time was longer, the reactive hyperemia appeared later and was bigger. When TPI decreased, the peak time lengthened and the peak flow after a 6-minute occlusion decreased. In the clinical study, the more severe the degree of the preoperative limb ischemia was, the longer was the peak time. The longer the intraoperative clamping time, the longer the peak time. In conclusion, postocclusive reactive hyperemia during vascular surgery was influenced by the degree of the preoperative limb ischemia and the length of the vascular clamping time.

Microvascular function and rheologic changes in hyperdynamic sepsis

OBJECTIVE

To investigate the rheologic changes and circulatory abnormalities at the microvascular level during severe sepsis.

DESIGN

Prospective, controlled trial.

SETTING

Medical and surgical intensive care units of a university-affiliated hospital.

PATIENTS

Nine normal controls and eight adult patients with severe sepsis who met the study entrance criteria.

INTERVENTIONS

Forearm blood flow was measured at rest and during reactive hyperemia by air plethysmography. Simultaneous hemodynamic measurements and blood samples for rheologic measurements were taken.

MEASUREMENTS AND MAIN RESULTS

Red blood cell deformability index was determined using a simple filtration procedure. Leukocyte aggregation in whole human blood was detected by using a leukergy test. Expression of the neutrophil adhesion molecule CD11b/CD18 was measured using a monoclonal antibody and flow cytometry. All data were taken within 24 hrs of the patient meeting criteria for entrance into the study. Cardiac output, oxygen delivery, and oxygen consumption measurements were consistent with the hyperdynamic phase of severe sepsis. Forearm blood flow was significantly (p < .05) greater in septic patients (21 +/- 3 mL/min) than in controls (12 +/- 2 to 36 +/- 5 mL/min (p < .05), while in the septic patients, forearm blood flow during reactive hyperemia increased from 21 +/- 3 to 32 +/- 4 mL/min. The ratio of forearm blood flow during reactive hyperemia to forearm blood flow at rest was 3.2 +/- 0.1 in the controls and 1.6 +/- 0.1 in the septic patients (p < .01). The red blood cell deformability index in whole blood was significantly (p < .01) decreased in the septic patients compared with the control subjects (0.41 +/- 0.07 vs. 0.98 +/- 0.08 mL/min). This difference remained true when the hematocrit was adjusted to 45% (0.82 +/- 0.06 vs. 1.04 +/- 0.06 mL/min; p < .05). Increased expression of the neutrophil adhesion molecule CD11b/CD18 was observed in septic patients (349 +/- 46 logarithmic fluorescence units) as compared with control subjects (233 +/- 26 logarithmic fluorescence units; p < .05). Leukergy was also significantly (p < .05) increased in septic patients (17.7 +/- 3.8%) as compared with control subjects (8.9 +/- 1.6%). A significant correlation was observed between leukergy and the expression of the neutrophil adhesion molecule CD11b/CD18 in controls and septic patients (r2 = .62; p < .01). Leukergy was also inversely correlated with whole blood red blood cell deformability index (r2 = .28; p < .05).

CONCLUSIONS

Reactive hyperemia in the forearm is significantly diminished in patients with sepsis, suggesting impaired microvascular blood flow. Rheologic changes, including impaired red blood cell deformability, increased leukocyte aggregation, and endothelial adherence, may contribute to this abnormality by compromising effective capillary cross-sectional area.

Effects of habitual tobacco smoking on reactive hyperemia in the human hand

The purpose of this study was to test the hypothesis that habitual smoking of tobacco cigarettes reduces reactive hyperemia in peripheral areas of smokers who are at low risk of having atherosclerotic vascular disease. This was achieved by a cross-sectional comparison of post-occlusion hyperemia in the hand circulation of female cigarette smokers and nonsmokers in the 20- to 40-yr age range. Epidemiologic evidence indicates that sclerotic lesions are unlikely in the upper extremities of females in this age range. The right hand of a subject was maintained in a water bath at 32 degrees C while mean blood flow velocity (V) in the radial artery was measured before and after occlusion periods of 1 and 5 min. The 5-min period elicited maximal reactive hyperemia. Following both periods of occlusion the percent increase in V was less for smokers (P less than .02). Also, the absolute increase in V following 5 min of occlusion for the smokers was less than that of the nonsmokers (P less than or equal to .05). These results indicate that habitual cigarette smoking reduces peripheral vasodilatory reserve in young smokers. The fact that sclerotic lesions are unlikely in the present subjects points to a microcirculatory rather than a macrocirculatory effect.

The influence of temperature on the amplitude and frequency components of the EMG during brief and sustained isometric contractions

The influence of temperature on the amplitude and frequency components of the EMG power spectra of the surface EMG recorded over the forearm muscles was examined in five male and five female subjects during brief and fatiguing isometric contractions of their handgrip muscles. Brief (3 s) isometric contractions were exerted at tensions ranging between 10 and 100% of each subject's maximum strength while fatiguing contractions were exerted at tensions of 25, 40, and 70% of their maximum strength. The temperature of the muscles during those contractions was varied by placing the forearms of the subjects in a controlled temperature water bath at temperatures of 10, 20, 30, and 40 degrees C. The results of these experiments showed that the center frequency of the power spectra of the surface EMG was directly related to the temperature of the exercising muscles during brief isometric contractions. During fatiguing isometric contractions, the amplitude of the EMG increased while the center frequency of the EMG power spectra decreased for all tensions examined.

Measurement of forearm blood flow by venous occlusion plethysmography: influence of hand blood flow during sustained and intermittent isometric exercise

The requirement for using an arterial occlusion cuff at the wrist when measuring forearm blood flows by plethysmography was tested on a total of 8 subjects at rest and during and after sustained and intermittent isometric exercise. The contribution of the venous effluent from the hand to the forearm flow during exercise was challenged by immersing the arm in water at 20, 34, and 40 degrees C. Occlusion of the circulation to the hand reduced the blood flow through the resting forearm at all water temperatures. There was an inverse relationship between the temperature of the water and the proportion in the reduction of forearm blood flow upon inflation of the wrist-cuff, ranging from 45 to 19% at 20 degrees to 40 degrees C, respectively. However, during sustained isometric exercise at 10% of the subjects maximum voluntary contraction (MVC) there was no reduction in the measured forearm flow when an arterial occlusion cuff was inflated aroung the wrist. Similarly, there was no alteration in the blood flow measured 2 s after each of a series of intermittent isometric contractions exerted at 20% or 60% MVC for 2 s whether or not circulation to the hand was occluded nor of the post-exercise hyperemia following 1 min of sustained contraction at 40% MVC. These results indicate that a wrist-cuff is not required for accurate measurement of forearm blood flows during or after isometric exercise.

The lack of influence of reactive hyperemia on exhausting rhythmic or static exercise

Muller (1958) and Nukada (1955) claimed that the performance of exhausting exercise can be greatly prolonged if the exercise is begun at the start of reactive hyperemia. They reported that arrest of the circulation for 10 min immediately before beginning rhythmic exercise had increased the endurance time nearly 7-fold. We have repeated Muller's and Nukada's experiments. In one series we used rhythmic exercises on a bicycle ergometer, and in another sustained contractions on a hand-grip dynamometer. Our results failed to support those of the above authors. The endurance times for rhythmic and static exercise were unaltered by previous arrest of the circulation.