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Biomedical subjects

G Wetherley-Mein

Publications and source records attributed to G Wetherley-Mein.

At least 37 records · Page 2Linked to original sources
PubMed1980

Cerebral blood flow, haematocrit and viscosity in subjects with a high oxygen affinity haemoglobin variant.

The cerebral blood flow is low in primary polycythaemia, and it has been suggested that this is due to the increase in viscosity which accompanies the elevated haematocrit. In the present study cerebral blood flow has been measured by a non-invasive 133Xenon technique in six subjects with an elevated haematocrit secondary to a haemoglobin variant with increased oxygen affinity. Flow was significantly higher than normal and 81% higher than in 11 subjects of comparable age, matched for haematocrit and viscosity, but without the haemoglobin variant. In patients with this unusual type of polycythaemia, cerebral blood flow is high despite the elevated blood viscosity and the implications of these results are discussed.

Adult↗
PubMed1979

Cerebral blood-flow and viscosity in relative polycythaemia.

Cerebral blood flow (CBF), red-cell mass, and plasma volume were measured in 39 patients with venous haematocrit values in the range 0.47--0.58. Patients with true polycythaemia were thus excluded. The 39 patients studied fell into two groups--those with a measured red-cell mass in the high-normal range and those with normal red-cell-mass values but reduced plasma-volume values (the relative-polycythaemia, low-plasma-volume group). The mean CBF was low in both the high-normal red-cell-mass (HNRCM) group (45.8 ml/100 g/min) and low-plasma-volume (LPV) group (48.8 ml/100 g/min). The haematocrit in the HNRCM group was 0.504 and in the LPV group 0.513. In a control group of subjects with a mean haematocrit of 0.421 CBF was 68.6 ml/100 g/min. Venesection was associated with a significant rise in CBF in both groups of patients--to 59.7 ml/100 g/min in the HNRCM group and 65.0 ml/100 g/min in the LPV group. Whole-blood viscosity fell significantly in both groups. Both groups demonstrated significant inverse relationships between CBF and haematocrit and between CBF and blood viscosity.

Adult↗
PubMed1979

The course and complications of idiopathic erythrocytosis.

The presenting features, haematological and clinical course of 30 patients with unexplained high venous haematocrit have been analysed. At presentation these patients had definite polycythaemia, but lacked other features which would permit their classification as primary proliferative polycythaemia (PPP). In the follow-up period, twelve patients (40%) developed features within 6 years of diagnosis which allowed them to be reclassified as PPP. It is suggested that, because of this transition, the term idiopathic erythrocytosis is a more suitable initial description of this group than, for example, benign erythrocytosis. The high incidence of vascular complications at presentation, and the fact that a cerebrovascular accident was responsible for the death of five out of the seven patients who have so far died, is discussed and compared with similar events in PPP. The existence of a pure line red cell proliferation cannot be confirmed or excluded by the observations in the present group of patients. The findings do indicate that follow-up and observation of such patients may establish causes for polycythaemia not in evidence or considered at presentation.

Adult↗
PubMed1978

Vascular occlusive episodes and venous haematocrit in primary proliferative polycythaemia.

The relations between the incidence of vascular occlusive episodes and packed-cell volume (P.C.V) and platelet-count in patients with primary proliferative polycythaemia were determined retrospectively in patients treated by venesection with or without chemotherapy. The incidence of occlusive episodes correlated positively with P.C.V. level. The risk of vascular occlusive episodes was increased at moderately increased P.C.V. levels and the optimum P.C.V. level was rather lower than is often assumed. There was no statistically significant association between platelet-count, either alone or in combination with raised P.C.V., and incidence of vascular occlusion, though, episodes of occlusion were 1.5 times more common with platelet-counts above 400 x 10(9)/l. The results of this study indicate that P.C.V. should be maintained at less than 0.45 and the platelet-count at less than 400 x 10(9)/l in primary proliferative polycythaemia.

Adult↗
PubMed1978

Cell studies in prolymphocytic leukaemia.

A case of prolymphocytic leukaemia, showing several features not yet reported in this disease, is reported. The majority of lymphocytes in the peripheral blood and bone marrow had markers of both B- and T-lymphocytes. The simultaneous presence of receptors for sheep RBC and surface immunoglobulins on individual cells was demonstrated and the endogenous origin of these markers was established. The lymphocytes had some of the functional characteristics seen in chronic lymphocytic leukaemia (CCL). In vitro cell death in the presence of colchicine (colchicine ultrasensitivity) and polystyrene bead column retention were of the same order as seen in CLL. In contrast with the findings in CLL, these cells were markedly radioresistant in vitro. The dominant clinical features--anaemia and constitutional symptoms--appeared to be related to hypersplenism associated with massive splenomegaly. The relevance of these findings is discussed.

Aged↗
PubMed1978

Interpretation of measured red cell mass in the diagnosis of polycythaemia.

Expression of predicted and measured red cell mass (RCM) in terms of ml/kg body wt. lacks precision. The use of formulae for prediction of normal mean red cell mass derived from the blood volume prediction (BV) of Nadler et al (1962) has been examined. It is proposed that a more accurate determination of mean normal predicted red cell mass (MNRCM) is obtained by using: 0.47 X 0.91 X BV = MNRCM for males; 0.43 X 0.91 X BV = MNRCM for females. The MNRCMs given by these formulae agree with those given by predictions based on lean body mass and surface area. Examination of the '95% confidence limits' of the 'Nadler' prediction indicates that males with measured RCMs greater than 25% and females with measured RCMs greater than 30% above their MNRCM may be regarded as having polycythaemia.

Body Height↗
PubMed1977

Effect of haematocrit on cerebral blood-flow in man.

Cerebral blood-flow (C.B.F.) was measured in 38 patients with haematocrit values (Hct) in the range 0-47--0-53 and was found to be significantly lower than in 43 patients with Hct in a lower range (0-36--0-46). After reduction of Hct in the higher Hct group by venesection, flow increased by a mean of 50%. This improvement in flow was largely due to a reduction in viscosity. Hct around the generally accepted upper limit of normal may be an important factor in the causation of occlusive vascular disease.

Adult↗
PubMed1977

Cerebral blood-flow in polycythaemia.

Cerebral blood-flow (C.B.F.) has been measured in 16 patients with polycythaemia of differing severity. The mean C.B.F. was 37-9 ml/100 g/min, which is significantly below the normal level of 69-1 (S.D. 9-3) ml/100 g/min (P less than 0-001). C.B.F. measurement was repeated after venesection in 15 of the patients. Lowering the haematocrit from a mean of 0-536 to a mean of 0-455 was associated with a 73% increase in mean C.B.F. (P less than 0-001) and a 30% reduction in whole-blood viscosity. Low C.B.F. was found at haematocrit levels between 0-46 and 0-52. Haematocrit levels that are currently acceptable in the management of polycythaemia may therefore be too high.

Aged↗
PubMed1976

Viscosity and retinal vein thrombosis.

Whole-blood and plasma viscosity with haematological and biochemical investigations were measured in 44 patients with retinal vein occlusion. The patients were subdivided on the basis of fluorescein angiographic findings into: 1. Those with large areas of capillary non-perfusion. 2. Those with small areas of capillary non-perfusion. 3. Those with an intact capillary pattern. Capillary non-perfusion in retinal vein occlusion is associated with a higher morbidity owing to the complications of retinal neovascularization. Significantly higher values of whole-blood viscosity, packed cell volume, and yield stress have been found in patients with capillary non-perfusion than in those without. These differences may be of critical importance during the episode of retinal vein occlusion and suggest an aetiological factor in the development of capillary non-perfusion. Higher whole-blood and plasma viscosity values and plasma fibrinogen levels have also been shown in the whole retinal vein occlusion group compared with a control group of 30 individuals. These differences may be a factor in the development of retinal vein occlusion but their precise role is difficult to evaluate. Further biochemical investigations in the vein occlusion group supported the strong association with arterial disease and suggested a higher incidence of biochemical abnormalities in those patients with capillary non-perfusion.

Adult↗