Ole Henriksen

The Reflex Sympathetic Dystrophy Syndrome: An Experimental Study of Sympathetic Reflex Control of Subcutaneous Blood Flow in the Hand

Adrenergic sympathetic vasoconstrictor activity in subcutaneous tissue on the back of the hand was studied in 13 patients suffering from reflex sympathetic dystrophy syndrome. Subcutaneous blood flow was measured by the local 133Xe wash-out technique with simultaneous measurements on the healthy side as a control. The results indicated an increased subcutaneous blood flow in the affected hand compared with the control side. Proximal nervous blockade caused only a slight, 35% increase in subcutaneous blood flow on the affected side, whereas an increase of 122% was registered on the control side. Augmented sympathetic vasoconstrictor activity elicited by the local veno-arteriolar axon reflex mechanism or centrally elicited by head-up tilt caused an equal degree of arteriolar vasoconstriction in both hands. The results suggest that sympathetic vasomotor tone during resting conditions is reduced in the affected hand in patients with the reflex sympathetic dystrophy syndrome.

Experimental Osteoarthritis in the Rabbit: A Study of 133Xenon Washout Rates from the Synovial Cavity

Synovial perfusion in 6 rabbit knees, with experimentally induced osteoarthritis (joint instability), was studied by recording the initial 133Xe washout rates from the joint space. The unstable osteoarthritic knee was compared with the contralateral sham operated control knee at intervals of 6 to 96 weeks postoperatively. Within the first half year the ratio between the 133Xe washout rates in the osteoarthritic and control joints was significantly increased. These findings were supported by the increased blood flow to the joint region, visualized by scintigraphy of osteoarthritic rabbits given 99mTc-microspheres intracardially. However, methodological sources of error do not allow any conclusions regarding the much less increased 133Xe washout rates found in advanced osteoarthritis. The initially increased synovial blood flow coincided with the existence of joint effusion and the early development of osteophytes, all conditions supposed to be a consequence of posttraumatic synovitis. Attention is drawn to these pathogenic phenomena in studies dealing with the initial changes in experimental models of osteoarthritis and to a possible etiological significance.

Tracer Studies of Peripheral Circulation

Studying the blood flow of the various tissues by tracers (also called indicators) one assumes steady state conditions for the system. It means, that the relevant parameters of the system are taken to be constant, the flow, oxygen uptake, etc. Systemic steady state is elementary for deriving the basic equations. It must persist during the time needed for making the measurement. This does not mean, however, that some degree of variability of the systemic parameter in question cannot be allowed. Consider for example the determination of cardiac output by injection of below-body-temperature saline in the right side of the heart with downstream temperature measurement in the pulmonary artery (“heat” clearance). In this case the flow rate of the blood in the system measured oscillates enormously. Yet, because the duration of the period of oscillation is fairly short relative to the duration of the heat clearance curve itself, one can get a good estimate of the average blood flow. In contrast to the systemic parameters, the tracer parameters, as for example the blood concentration, often vary as a function of time, i.e. for the tracer the steady state condition does not (in many cases) pertain.