L. T. Cotton

Haemorrheological response to plasma exchange in Raynaud's syndrome.

Eight patients with Raynauds syndrome were treated by weekly plasma exchange for four weeks using a Haemonetics Model 30 Blood Processor. The mean whole-blood viscosity at a shear rate of 0.77/s was significantly lower after treatment, and the mean index of red-cell deformability was significantly improved. In four patients studied serially the mean percentage fall in whole-blood viscosity after a single plasma exchange was 49% at 0.77/s but only 14% at 91/s. All patients noticed symptomatic improvement including healing of ischaemic digital ulcers. In six patients the number of digital arterial segments containing detectable blood flow was measured by directional Doppler; in all six the number increased. It is concluded that plasma exchange is an effective means of haemorrheological treatment and may be beneficial in patients with digital ischaemia.

Prevention of Early Postoperative Deep Vein Thrombosis by Intermittent Compression of the Leg during Surgery

A clinical trial is described in which the effect of intermittent compression of the lower limb during surgery on the incidence of early postoperative deep vein thrombosis was assessed. Deep vein thromboses were diagnosed by the 125I-fibrinogen uptake test. Peroperative intermittent compression was achieved by means of an inflatable plastic splint coupled to a pneumatic controller. By compressing only one leg of each patient, each patient acted as his own control. With a sequential statistical analysis, 39 patients were required to pass the 5% level of significance. Eleven thrombi were detected in the control (uncompressed) legs and two occurred in the compressed legs; one of the latter was bilateral. The investigation shows that increasing the pulsatility of the venous flow in the leg is a potent prophylactic against postoperative deep vein thrombosis.

SEXUAL FUNCTION FOLLOWING AORTOILIAC RECONSTRUCTION

Impotence due to atherosclerotic disease of the aorta and iliac arteries presents as failure to achieve erection. Sterility after aortoiliac reconstructive surgery is more common and presents as inability to ejaculate. If the superior hypogastric sympathetic plexus (presacral nerve) is preserved, sexual function can be maintained in 90% of cases.

Prevention of Early Postoperative Deep Vein Thrombosis by Passive Exercise of Leg during Surgery

A clinical trial assessed the effect of passive exercise of the lower limb during surgery on the incidence of early postoperative deep vein thrombosis. Thrombosis was diagnosed by means of the 125I-fibrinogen uptake test. Passive exercise of the lower limb during the operation was achieved by using a motorized foot mover designed for use on supine subjects, and by pedalling only one leg each patient acted as his own control. In a sequential statistical analysis, 47 patients were required to reach the 5% level of significance. Thrombosis was detected in 11 control (unpedalled) legs alone, and in only one pedalled leg alone. Two patients developed thrombosis bilaterally. The investigation shows that the incidence of early thrombosis in legs which were exercised during surgery was reduced by 77%.

Effects of Externally Applied Pressure on the Haemodynamics of the Lower Limb

The effects of externally applied pressure of 5-150 mm Hg on the haemodynamics of the leg of dog and man were investigated. The criteria used for the assessments included femoral arterial and venous blood flow as well as vascular hydraulic conductance. The results indicated that external pressure of 5 mm Hg results in a very small non-significant increase in the femoral arterial and venous flow. Higher external pressure of 15 mm Hg or more significantly reduces the femoral arterial and venous flows as well as the vascular conductance. It therefore seems that compression produced by bandaging in horizontal supine subjects has little or no haemodynamic value and may prove to be harmful unless carefully controlled.

Raynaud's phenomenon and thermal entrainment: an objective test.

A new objective test for diagnosing Raynauds phenomenon was assessed in practice. The test is based on entrainment of the thermal vasomotor control system and entails non-invasive measurement of blood-flow responses in one hand while alternating thermal stimuli are applied to the contralateral hand. A significant (p less than 0.001) abnormality of vasomotor control was found in patients with Raynauds phenomenon compared with normal subjects. When applied clinically this test is diagnostic and indicates the severity of the disease and the effect of treatment.

The effect of adjuvant oxygen therapy on transcutaneus p02 and healing in the below-knee amputee

The effects on tissue oxygenation of postoperative adjuvant oxygen have been studied in a group of 20 patients undergoing below-knee (BK) amputation for vascular disease. Ten patients received no therapy, the remainder receiving 28% oxygen for 48 hours following surgery. The results showed that the trancutaneous p02 in the amputation flaps fell significantly by some 20 mmHg (p<0.01) following surgery and that this fall was prevented by the use of adjuvant oxygen. The fall was not observed in the non-amputated limbs. Tcp02 took almost two weeks to reach its pre-operative levels in the amputated limbs. The effect on stump healing of adjuvant oxygen therapy was investigated in a randomized controlled trial in a series of 39 patients undergoing BK amputation. There were 22 patients in the control (untreated) group and 17 in the treated group (adjuvant oxygen for 48 hours). In the treated group 14 patients healed primarily and three amputations failed. In the untreated group 14 limbs healed primarily, one secondarily and there were 7 failures. The pre-operative transcutaneous values in the stumps which failed (26 mmHg±14) was significantly lower (p<0.005) than in those which healed (40 mmHg±9). The mean pre-operative Tcp02 in the patients in whom healing occurred in the treated group (35 mmHg±10) was significantly lower (p<0.001) than the mean pressure observed in the untreated group (44 mmHg±9).

Per-operative haemodynamic assessment of lower limb arterial surgery Part 1: Hydraulic impedance measurement

Hydraulic impedance measurements have been made during surgery on 32 patients undergoing reconstructive arterial surgery. The reconstructive procedures included aorto-iliac, femoro-popliteal and axillo-femoral bypass, and extended deep femoral angioplasty. It was found that in aorto-iliac reconstruction the phase curves provide the means of assessing success, but that in other cases the impedance measurements though showing a similar trend are unable unequivocally to differentiate between success or failure.

Validity of the transfer function model of the human arterial system of the lower limb in man

A transfer function model of the human arterial system has been examined and tested on a group of 21 patients undergoing reconstructive arterial surgery in the leg. It was found that use of the model to estimate parameters relating to proximal (above femoral artery) arterial wall stiffness and radius is not reliable, the model being affected by the peripheral resistance. The value of the model parameters relating to the peripheral arterial radius is more consistent with the theory although there are still contradictions. It is concluded that the application of transfer function modelling to the diagnosis of arterial disease should be approached with caution.

Thermal entrainment methods for studying Raynaud's phenomenon.

Entrainment occurs when an externally applied periodic temperature stimulus forces the peripheral bloodflow component of thermoregulation to oscillate at the same frequency. This phenomenon can be demonstrated using frequency transforms to analyse the spectral content of the bloodflow, and can be used as a diagnostic test for Raynauds phenomenon. Correlations were performed between the clinical diagnosis and the objective tests. The average inter-clinical correlation coefficient was r = 0.66. When the average clinical diagnosis was compared with a combination of thermal entrainment and digital patency testing the correlation coefficient rose to r = 0.68. These results highlight the difficulties encountered when assessing patients with Raynauds phenomenon and the necessity of applying both physiological and clinical techniques.