Increase in leg blood-flow by normovolaemic haemodilution in intermittent claudication

Incidence and Predictors of Surgical Site Infection Complications in Diabetic Patients Undergoing Lower Limb Amputation

BACKGROUND

Surgical site infections (SSIs) following lower extremity amputations (LEAs) are a major cause of patient morbidity and mortality. The objectives of this study are to investigate the annual incidence of SSI and risk factors associated with SSI after LEA in diabetic patients.

METHODS

LEAs performed on diabetic patients between 2005 and 2017 were retrospectively analyzed from the American College of Surgeons National Surgical Quality Improvement Program database. Incidence rates were calculated and analyzed for temporal change. Multivariable logistic regression was conducted to identify the independent predictors of SSIs in LEA.

RESULTS

In 21,449 diabetic patients, the incidence of SSIs was 6.8% after LEA, with an overall decreasing annual trend (P = 0.013). Amputation location (below-knee in reference to above-knee) [OR (95% CI): 1.35 (1.20 - 1.53), P <0.001], smoking [OR (95% CI): 1.25 (1.11 - 1.41), P <0.001)], female sex [OR (95% CI): 1.16 (1.03 - 1.30)], preoperative sepsis [OR (95% CI): 1.24 (1.10 - 1.40), P <0.001], P = 0.013], emergency status [OR (95% CI): 1.38 (1.17 - 1.63), P <0.001], and obesity [OR (95% CI): 1.59 (1.12 - 2.27), P = 0.009] emerged as independent predictors of SSIs, while moderate/severe anemia emerged as a risk-adjusted protective factor [OR (95% CI): 0.75 (0.62 - 0.91), P = 0.003]. Sensitivity analysis found that moderate/severe anemia, not body mass index (BMI) class, remained a significant risk factor in the development of SSIs in below-the-knee amputations; in contrast, higher BMI, not preoperative hematocrit, was significantly associated with an increased risk for SSI in above-the-knee amputations.

CONCLUSIONS

The incidence of SSIs after LEA in diabetic patients is decreasing. Overall, below-knee amputation, smoking, emergency status, and preoperative sepsis appeared to be associated with SSIs. Obesity increased SSIs in above-the-knee amputations, while moderate/severe preoperative anemia appears to protect against below-the-knee SSIs. Surgeons should take predictors of SSI into consideration while optimizing care for their patients, and future studies should investigate the role of preoperative hematocrit correction and how it may influence outcomes positively or negatively.

Haemoglobin, Smoking and Peripheral Vascular Disease

One hundred and four patients with peripheral vascular disease requiring operation were reviewed retrospectively with respect to age, sex, preoperative haemoglobin, smoking habits and diabetic status. The preoperative haemoglobin levels and smoking status in 63 non-diabetic male patients with peripheral vascular disease were compared with a matched group of individuals treated for inguinal hernia. For all patients there was a significant correlation between smoking habits, preoperative haemoglobin level and the presence of peripheral vascular disease. The mechanisms by which smoking may damage the vascular tree are reviewed.

Improvement in Blood Supply After "Heparin-Dextran" Therapy in Patients of Buerger's Disease with Critical Limb Ischemia

Alleviating the agonizing pain of critical limb ischemia (CLI) in patients of Buerger's disease (BD) has been challenging, due to lack of definitive treatment; "Heparin-Dextran" infusion has been tried in this study. Assessment of clinical improvement and vascular changes following therapy. Patients with CLI admitted to emergency surgical ward were studied prospectively. BD was diagnosed by Shionoya's criteria, and confirmed by digital subtraction angiography (DSA). Heparin and Dextran intravenous infusion was administered for 10 days. Severity of rest pain, ischemic changes in the feet, claudication distance and ankle brachial index (ABI) were estimated prior to therapy, at completion and 3 weeks after therapy. Vascular changes were assessed by CT angiography (CTA) performed prior to and 3 weeks after therapy. Twenty consecutive patients were studied. Successful hemodilution reflected by decreased hematocrit (37.4 % to 32.6 %, p < 0.05) and increased mean ABI (0.46 to 0.83, p < 0.01), improved rest pain in 75 % patients (p < 0.001), increased claudication distance in 94 % (p < 0.05) and ulcers healing in 70 % patients. CTA revealed recanalised vessels (decreased length of occluded segments) in 10 (50 %, p = 0.005), increased collaterals in 12 (60 %, p < 0.01) and improved distal run-off in 13 (65 %, p < 0.01) patients. "Heparin-Dextran" therapy in patients of CLI from BD improves tissue perfusion by increasing collaterals and recanalisation of vessels, resulting in significant relief from rest pain and clinical improvements. CTA is as efficacious as DSA for evaluation of BD.

Measured outcomes with hypnosis as an experimental tool in a cardiovascular physiology laboratory

The authors detail their multidisciplinary collaboration of cardiologists, physiologists, neurologists, psychologists, engineers, and statisticians in researching the effects of hypnosis on the cardiovascular system and their additions to that incomplete literature. The article details their results and provides guidelines for researchers interested in replicating their research on hypnosis' effect on the cardiovascular system.

Effects of polycythemia on systemic endothelial function in chronic hypoxic lung disease

Chronic obstructive pulmonary disease (COPD) is a major risk factor for cardiovascular disease. Polycythemia, a common complication of hypoxic COPD, may affect systemic vascular function by altering blood viscosity, vessel wall shear stress (WSS), and endothelium-derived nitric oxide (NO) release. Here, we evaluated the effects of hypoxia-related polycythemia on systemic endothelial function in patients with COPD. We investigated blood viscosity, WSS, and endothelial function in 15 polycythemic and 13 normocythemic patients with COPD of equal severity, by recording brachial artery diameter variations in response to hyperemia and by using venous occlusion plethysmography (VOP) to measure forearm blood flow (FBF) responses to a brachial artery infusion of acetylcholine (ACh), bradykinin (BK), sodium nitroprusside (SNP), substance P (SP), isoptin, and N-monomethyl-l-arginine (l-NMMA). At baseline, polycythemic patients had higher blood viscosity and larger brachial artery diameter than normocythemic patients but similar calculated WSS. Flow-mediated brachial artery vasodilation was increased in the polycythemic patients, in proportion to the hemoglobin levels. ACh-induced vasodilation was markedly impaired in the polycythemic patients and negatively correlated with hemoglobin levels. FBF responses to endothelium- (BK, SP) and non-endothelium-dependent (SNP, isoptin) vasodilators were not significantly different between the two groups. l-NMMA infusion induced a similar vasoconstrictor response in both groups, in accordance with their similar baseline WSS. In conclusion, systemic arteries in polycythemic patients adjust appropriately to chronic or acute WSS elevations by appropriate basal and stimulated NO release. Overall, our results suggest that moderate polycythemia has no adverse effect on vascular function in COPD.

Is hemoglobin concentration a predictor for the outcome of distal gangrenous lesions in diabetics?

The predictive value of some routine laboratory tests given on admission was evaluated in a retrospective study to determine whether any given value could predict the outcome of distal gangrenous lesions and amputations in diabetic and nondiabetic patients. There was no difference in preoperative hemoglobin concentration between successful and unsuccessful amputations in 45 diabetic and 59 nondiabetic patients. In another group of 191 diabetic patients with distal gangrenous lesions, the lesions healed after nonsurgical treatment in 112 patients, 54 patients were submitted to amputation and 25 patients died before the lesions healed. Patients submitted to amputation had lower hemoglobin levels and higher erythrocyte sedimentation rates and white blood counts than patients in whom the lesions healed, whilst there were no differences between these two groups concerning blood glucose concentration or body temperature.

Fibrinogen Apheresis in the Treatment of Peripheral Arterial Disease

BACKGROUND

Fibrinogen is mainly responsible for determining the viscosity of whole blood. In peripheral arterial disease (PAD) the fibrinogen concentration seems to affect the microcirculation flow.

AIM

To study the effects of an abrupt reduction of fibrinogen on the hemodynamics of the lower extremities and the clinical picture of patients with PAD.

METHODS

Ten patients affected by various stages of PAD underwent 1 session of fibrinogen apheresis (TheraSorb, Miltenyi Biotec, Germany). Laboratory parameters of endothelial activation were assessed before and after the session, as well as walking distance (WD), the ankle-brachial index and laser Doppler flowmetry.

RESULTS

A significant reduction in the laboratory parameters was observed: fibrinogen (50%), total cholesterol (18%), LDL cholesterol (24%), sE-selectin (23%), sICAM-1 (19%) and sVCAM-1 (10%). The procoagulant factors, factor VIII and von Willebrand factor, did not vary significantly. Both pain-free and total WD were significantly improved (p < 0.003 and p <0.006, respectively), the ankle-brachial index remained unchanged, and laser Doppler flowmetry showed a modest but not significant increase.

CONCLUSIONS

Fibrinogen apheresis allowed us to study the effects of an acute modification of fibrinogen in PAD, on both some aspects of the endothelial function and on the hemodynamics, demonstrating an improvement of WD and a minimal increase in the skin microcirculation.

Polycythemia impairs vasodilator response to acetylcholine in patients with chronic hypoxemic lung disease

To investigate whether polycythemia associated with chronic hypoxemic lung disease (CHLD) increases vascular resistance by altering endothelium-derived nitric oxide (NO), we examined the responses to acetylcholine (ACh) infusions (5, 10, and 15 mg/min) on hemodynamics and gas exchange in 21 patients with CHLD of varying severity. Patients were classified into two groups based on whether their hemoglobin (Hb) level was less or greater than 15.5 g/dl. In the normocythemic patients (Hb = 13.6 +/- 0.3 g/100 ml, n = 10), ACh decreased pulmonary artery pressure (Ppa) from 30 +/- 2 mm Hg 26 +/- 2 mm Hg (p < 0.01); pulmonary vascular resistance (PVR), from 5.1 +/- 0.4 U/m2 to 3.4 +/- 0.3 U/m2 (p < 0.001); systemic arterial pressure (Psa), from 111 +/- 4 mm Hg to 108 +/- 4 mm Hg (p < 0.05); and systemic vascular resistance (SVR), from 27 +/- 2 U/m2 to 22 +/- 2 U/m2 (p < 0.01); and also increased the cardiac index (CI), from 3.8 +/- 0.2 to 4.7 +/- 0.3 L/min/m2 (p < 0.001). PaO2 fell from 59 +/- 3 mm Hg to 48 +/- 3 mm Hg (p < 0.001) whereas venous admixture (Qs/Qt) rose from 32 +/- 4% to 44 +/- 4% (p < 0.01). In contrast, in patients with polycythemia (17.7 +/- 0.5 g/100 ml, n = 11) ACh failed to produce any changes in PaO2 (49 +/- 2 mm Hg versus 51 +/- 2 mm Hg, p = NS), Ppa (34 +/- 1 mm Hg versus 33 +/- 1 mm Hg, p = NS), PVR (6.7 +/- 0.9 U/m2 versus 6.9 +/- 0.8 U/m2, p = NS) or Psa, but slightly increased the CI, from 3.6 +/- 0.3 L/min/m2 to 3.9 +/- 0.3 L/min/m2 (p < 0.01), and Qs/Qt, from 40 +/- 4% to 45 +/- 3% (p < 0.05). In the 21 patients, negative correlations with Hb concentrations were found for ACh-induced changes in PVR (r = -0.57, p < 0.01), Ppa (r = -0.46, p < 0.01), CI (r = -0.5, p < 0.05), PaO2 (r = -0.79, p < 0.01), and Qs/Qt (r = -0.79, p < 0.01). In the six polycythemic patients who received isovolemic hemodilution, with a decrease in Hb concentration from 18.6 +/- 0.9 g/dl to 15.3 +/- 0.3 g/dl as a result, infusion of ACh, which was without effect before hemodilution, caused decreases in Ppa from 28 +/- 1 mm Hg to 23 +/- 1 mm Hg (p < 0.05) and in PVR from 5.7 +/- 0.8 U/m2 to 3.6 +/- 0.5 U/m2 (p < 0.02), as well as an increase in CI from 3.4 +/- 0.4 L/min/ m2 to 4.1 +/- 0.4 L/min/m2 (p < 0.05). In contrast to ACh, inhaled NO (40 ppm) induced pulmonary vasodilation in both the normocythemic and polycythemic groups. Our results show that high hematocrit (Hct) levels inhibit endothelium-dependent vasodilation in response to ACh in patients with CHLD, possibly through inactivation of endothelial-derived NO by Hb.

Clinical and hemodynamic effects of stepwise lowering of hemoglobin concentration in patients with intermittent claudication

This study evaluates the effect of stepwise lowering of the hemoglobin (Hb) concentration on maximal walking distance (MWD) and hemodynamics in patients with intermittent claudication. The results in a study group (n = 6) were compared with those of a control group (n = 6) whose members were not subjected to venesections. An average decrease of Hb concentration from 151 +/- 4 to 121 +/- 3 g/L did not significantly influence MWD, the result being 282 +/- 62 meters before venesections and 255 +/- 54 meters after three to five (mean four) repeated venesections. Transcutaneous oxygen pressure was measured at the dorsum of the foot before and after exercise and did not change with a gradual decrease of the Hb concentration. Maximal heart rate, painfree walking distance, ankle pressure, and blood lactate concentration were also unchanged. An average venesection volume of about 1.4 liters whole blood within fourteen days, without isovolemic replacement, did not change the blood volume, which was 5.1 +/- 0.4 liters before and 5.0 +/- 0.5 liters after venesections. In conclusion, hemodilution accomplished by venesections did not have a clinically or physiologically beneficial effect in patients with severe intermittent claudication. However, hemodynamics and clinical symptoms were not affected by a considerable decrease in the arterial oxygen content within the normal Hb concentration range.

Risk factors for failed healing in amputation for vascular disease. A prospective, consecutive study of 177 cases

We examined factors which may lower the mean amputation age and factors which may serve as predictors of success or failure of amputations in the lower extremities for vascular disease in 177 consecutive amputees. Smoking lowered the mean amputation age by 9 years and diabetes by 3 years. Preoperative absence of gangrene in the ischemic limb predicted a higher risk of failure compared to patients with gangrene. Also preoperative hemoglobin > 120 g/L gave a higher risk of failure. Failure to heal was not correlated with age, sex, diabetes, level of amputation, previous vascular surgery, smoking, preoperative blood pressure, serum creatinine, erythrocyte sedimentation rate, blood glucose or temperature.

Regular physical exercise and low-fat diet. Effects on progression of coronary artery disease

BACKGROUND

Significant regression of coronary and femoral atherosclerotic lesions has been documented by angiographic studies using aggressive lipid-lowering treatment. This study tested the applicability and effects of intensive physical exercise and low-fat diet on coronary morphology and myocardial perfusion in nonselected patients with stable angina pectoris.

METHODS AND RESULTS

Patients were recruited after routine coronary angiography for stable angina pectoris; they were randomized to an intervention group (n = 56) and a control group on "usual care" (n = 57). Treatment comprised intensive physical exercise in group training sessions (minimum, 2 hr/wk), daily home exercise periods (20 min/d), and low-fat, low-cholesterol diet (American Heart Association recommendation, phase 3). No lipid-lowering agents were prescribed. After 12 months of participation, repeat coronary angiography was performed; relative and minimal diameter reductions of coronary lesions were measured by digital image processing. Change in myocardial perfusion was assessed by 201Tl scintigraphy. In patients participating in the intervention group, body weight decreased by 5% (p less than 0.001), total cholesterol by 10% (p less than 0.001), and triglycerides by 24% (p less than 0.001); high density lipoproteins increased by 3% (p = NS). Physical work capacity improved by 23% (p less than 0.0001), and myocardial oxygen consumption, as estimated from maximal rate-pressure product, by 10% (p less than 0.05). Stress-induced myocardial ischemia decreased concurrently, indicating improvement of myocardial perfusion. Based on minimal lesion diameter, progression of coronary lesions was noted in nine patients (23%), no change in 18 patients (45%), and regression in 13 patients (32%). In the control group, metabolic and hemodynamic variables remained essentially unchanged, whereas progression of coronary lesions was noted in 25 patients (48%), no change in 18 patients (35%), and regression in nine patients (17%). These changes were significantly different from the intervention group (p less than 0.05).

CONCLUSIONS

In patients participating in regular physical exercise and low-fat diet, coronary artery disease progresses at a slower pace compared with a control group on usual care.

Alterations in erythrocyte rheology in patients with severe peripheral vascular disease: 1. Cell volume dependence of erythrocyte rigidity

The erythrocyte rigidity of patients suffering from severe peripheral vascular disease (PVD) was measured by a filtration method using 3 microns pore size filters. Filtration pressures for both PVD patients and normal subjects showed a cell volume dependency, and patient filtration pressures were normalized to cell volume to evaluate intrinsic, ie, nonvolume dependent, abnormalities in erythrocyte deformability. A significant (p less than 0.001) increase in cell rigidity was found in 44 of 54 PVD patients in comparison with volume-matched normal controls. No significant difference was found between patient mean corpusculer hemoglobin (MCH) and normal MCH at any given mean corpuscular volume (MCV), indicating that observed increases in erythrocyte rigidity are not attributable to changes in patient MCH. Therefore, the mechanism of increase in erythrocyte rigidity for PVD patients still needs further investigation into such parameters as levels of adenosine triphosphate,2,3-DPG, and membrane fluidity (calcium- and/or protein-binding membrane, cholesterol and phospholipid content of membrane, etc), as well as other aspects of erythrocyte physiology.

Current therapy of peripheral obstructive arterial disease. The non-surgical approach

In recent years double-blind trials have proved the effectiveness of nonsurgical therapy in the treatment of peripheral obstructive arterial disease (POAD). Among the non-pharmacologic measures taken, walking distance was increased by 40% in subjects who stopped smoking and by more than 100% in those who undertook physical exercise. Drug treatment reduces the atherosclerotic process and brings about an improvement in the symptoms of the disease. In subjects given hypolipidemic treatment the progression of the disease was reduced by two thirds. Two separate studies suggest that antiplatelet drugs, taken over a period of two to four years, significantly slow the progression of atherosclerosis in lower extremity arteries. In the treatment of claudication, two vasodilating drugs, naftidrofuryl and buflomedil, have shown a significant improvement in painfree walking distance and/or total walking distance, compared with treatment with placebo. Another effective approach is in the treatment of blood rheology through drugs such as pentoxifylline or by hemodilution. Double-blind trials with pentoxifylline demonstrated an average increase of 66% in maximum walking distance as compared with 22% with placebo. The effectiveness of hemodilution was demonstrated by two controlled trials, during which the reduction of the hematocrit to values of 40-42 for periods of four to six weeks increased both walking distance and resting blood flow. When introduced intraarterially in low doses in the vicinity of the occluding thrombus, thrombolytic agents have been found to be helpful in the treatment of acute and chronic POAD. This therapy should, however, be regarded as a substitute for surgical treatment only in high-risk patients. Further, after having produced the lysis of thrombi, the treatment permits the underlying parietal lesions to be accurately identified; at this point the appropriate therapy can be decided upon, either an operative procedure or a balloon dilation. In conclusion the many controlled clinical trials carried out over the past few years have clearly demonstrated that conservative treatment can alleviate clinical signs and symptoms in patients with claudication and pain at rest.

Tissue oxygen tension in random pattern skin flaps during normovolemic hemodilution

We investigated the effect of progressive normovolemic hemodilution with Dextran 70 on subcutaneous tissue oxygen tension (PscO2) in canine random pattern flaps and in adjacent intact skin. PscO2 was measured polarographically in implanted oxygen-permeable Silastic catheters. The mean PscO2 of 5.7 kPa in intact subcutis at hematocrit (HCT) 40 was maintained or insignificantly improved during hemodilution to a HCT of 14. The mean flap PscO2 of 3.1 kPa at HCT 40 was maintained down to HCT 20. Most flap measuring sites exhibited a PscO2 improvement in an individual HCT range at some point during hemodilution. The increment in PscO2 tended to be relatively greater and to occur at lower Hct values in locations with more severe ischemia initially. Central hemodynamics were characterized by a lowered total peripheral resistance and an increased cardiac output, whereas systemic and pulmonary arterial blood pressures and central venous pressure remained essentially unchanged.

Improved haemorheology associated with a reduction in plasma fibrinogen and LDL in patients being treated by heparin-induced extracorporeal LDL precipitation (HELP)

Heparin-induced Extracorporeal LDL-Precipitation (HELP) is an effective procedure for the elimination of both plasma LDL and fibrinogen. In 10 adult patients with severe type II hyperlipoproteinemia, a single HELP treatment of 3 1 plasma led to an acute decrease in the average plasma viscosity (PV) from 1.30 to 1.1 mPas. At the same time, an even more marked decrease in the mean erythrocyte aggregation rate from a pathological value of 7.9% to a value of 3.7% (normal range less than 5%) was observed. Long-term studies on five patients demonstrated a lasting improvement in these two haemorheological variables. The acute rheological changes were also accompanied by an improvement in polarographically determined muscle oxygen tension. Mean oxygen tension values measured in both the m.biceps brachii and the m.tibialis anterior in five patients before and after a single HELP treatment increased from 30 +/- 4 to 37 +/- 7 mmHg and from 27 +/- 2 to 31 +/- 3 mmHg respectively. These results may provide an explanation for the rapid improvement in patients' clinical symptoms such as angina pectoris and in stress electrocardiogram which have been observed during HELP therapy.

Long-term effects of ticlopidine on fibrinogen and haemorheology in patients with peripheral arterial disease

The effects of ticlopidine treatment (250 mg b.i.d. for 21 months) on fibrinogen and other rheological variables, as compared to placebo, were studied in 44 patients with intermittent claudication due to peripheral arterial occlusive disease. Blood samples were collected every 3 months during this double-blind, randomised placebo-controlled trial which lasted 21 months. Consistently lower values of fibrinogen, haematocrit and whole blood viscosity at high and low shear rate levels were found in the ticlopidine group; the intergroup differences were statistically significant at most but not all follow-up examinations. A significant time-related variance was observed in the ticlopidine group for the measured variables, also after correction for the variability found in the placebo group. Thus, the observed changes in the ticlopidine group are mainly treatment related. These effects on fibrinogen and haemorheology may contribute, besides the known antiplatelet activity of the drug, to the clinical improvement reported in a larger group of claudicants to which the present subset of patients belong.

Effects of venesection on leg blood flow in claudicants with high-normal haematocrit

Patients with intermittent claudication frequently have high-normal levels of haematocrit and hence blood viscosity, which may contribute to decreased calf blood flow on exercise, and hence to the symptom of claudication. Reduction in haematocrit and viscosity by serial venesection in eight patients with stable claudication and high-normal haematocrit (mean 0.50) was performed, and the effects on claudication, calf blood flow, and calf oxygen delivery were studied. Following reduction in haematocrit to low-normal levels (mean 0.44), resting calf blood flow was unchanged; peak flow after ischaemic exercise increased slightly (+17%), but peak oxygen delivery (peak flow X haemoglobin concentration) was unchanged. Hence any increase in calf blood flow in the symptomatic leg is balanced by a decrease in oxygen-carrying capacity after venesection. No increase in claudication time would therefore be expected, and none was observed in the present study.

Streptokinase and reduced plasma viscosity: a second benefit

The purpose of this pilot study on a small cohort of patients (n = 13) with acute myocardial infarction receiving systemic streptokinase (STK) thrombolytic therapy was to measure the decrease in plasma viscosity concomitant with fibrinogen depletion. The treatment group was compared with a similar control group not given thrombolytic therapy. Serial relevant blood studies were undertaken in both groups for a period of 6 d. In the treatment group, a maximum reduction in plasma viscosity of 17 +/- 9% (mean +/- S.D.) was achieved during the first 24 h. Plasma viscosity remained below baseline for the 6-d duration of the study. Conversely, in the control group, the plasma viscosity rose to a maximum of 19 +/- 14% (mean +/- S.D.) over the period of study, paralleling the rise in plasma fibrinogen as an acute-phase reactant. Correlation studies between viscosity and plasma fibrinogen were strongly positive with mean values of r of 0.74 and 0.66 in the STK-treated group and controls, respectively. We conclude that the benefit of systemic STK treatment may in part be due to reduced myocardial workload and oxygen consumption at a critical time, and improved microvascular circulation, consequent on reduced plasma viscosity.

Effect of hemodilution on brain tissue during global ischemia

This study evaluates the effect of blood volume and hematocrit changes on brain tissue during temporary global ischemia. Normal saline was administered intravenously to 55 gerbils to achieve hypo-, normo-, and hypervolemic hemodilution and uniform 30% hematocrit reduction. Each group had unilateral carotid artery ligation and temporary (20 minute) contralateral carotid occlusion. After ten days or death, brains were harvested, preserved in formalin, sectioned in a manner which provided adequate samples of both cortex and hippocampus, and stained with H&E and luxol fast blue. They were then examined and staged microscopically for white and gray matter infarction, edema, and neuronal injury and loss. Histologic studies were performed in a randomized and blinded manner and were classified by one of four categories: normal, minimal, moderate, and severe changes. Three of ten (30%) controls survived ten days but had severe neuronal loss, minimal cerebral edema and a minimal to moderate number of white matter strokes. Survival was best in animals treated with hypovolemic hemodilution (43%). Other rates were: normovolemic (33%), controls (30%), and hypervolemic (8.3%). The degree of brain tissue damage was markedly less in the normovolemic group. In this model, normovolemic hemodilution followed by hypovolemic hemodilution offered the best overall cerebral protection during global ischemia.

Hemoglobin and hematocrit as risk factors in below-the-knee amputation for incipient gangrene

The relationship between complication rate and preoperative levels of hemoglobin and hematocrit was investigated in 186 consecutive below-the-knee amputations for incipient gangrene. Arteriosclerotic amputations had successively higher rates of wound complications and reamputation with increasing hemoglobin and hematocrit. No such association was found among diabetics. Thus, hemoglobin greater than or equal to 7.0 mmol/l and hematocrit greater than or equal to 40 were significant preoperative risk factors in below-the-knee amputation for arteriosclerotic incipient gangrene.

Intermittent claudication, exercise, and blood rheology

Forty-two stable patients with claudication were assigned to two groups. Group I (n = 22) was submitted to regular, standardized treadmill exercise for 2 months. During this time the maximal and pain-free walking distances increased significantly (more than 100%). Group II (n = 20) patients did not exercise over the same period of time, and their walking distances remained essentially unchanged. No drugs or other forms of treatment were given in either group. The rheology of blood, as quantified by blood and plasma viscosity, hematocrit, blood filterability, and red cell aggregation, was initially abnormal in patients as compared with matched controls. Blood and plasma viscosity, blood cell filterability, and red cell aggregation normalized significantly in group I, but remained pathologic in group II. The hemorrheologic values of patients after 2 months of exercise did no longer differ significantly from those of healthy controls. The "fluidification" of blood induced by regular exercise was qualitatively and quantitatively similar to that obtainable by hemorrheologically active medications. The results confirm that physical training is clinically effective in patients suffering from claudication. They furthermore suggest that training may be looked on as a form of "hemorrheologic therapy" suitable for increasing the fluidity of blood in patients with ischemic diseases. Part of the benefits of regular exercise in stage II occlusive peripheral arterial disease may result from changes in hemorrheology; further studies are needed to define the mechanism.

Blood rheology in general medicine and surgery

Traditionally, blood rheology tests have been used in diagnosis and monitoring of infection, rheumatic diseases and malignancy, and are still of clinical value in these conditions. In the last twenty years, clinical and epidemiological studies have shown that the haematological determinants of blood flow resistance (haematocrit, fibrinogen, white cell count and altered red and white cell rigidity) are also associated with nutritional, metabolic, endocrine and vascular disorders. Decreased red cell deformability may contribute to reduced red cell survival and anaemia in burns, malaria, liver disease and kidney failure. In trauma and inflammatory disease, overt hyperviscosity is usually prevented by vasodilatation and reduction in the haematocrit. However, low-flow states may arise systemically from haemoconcentration (contracted plasma volume, Chapter 3) in severe burns, inappropriate red cell transfusion, or dehydration due to illness; systemically in circulatory shock; and locally in venous thrombosis or arterial disease. In such circumstances, the intrinsic flow resistance of blood may perpetuate flow disturbance, ischaemia and thrombosis. Conversely, optimal levels of haematocrit, fibrinogen and white cell count may be lower than normal in low-flow states. Haemodilution by colloid infusion is beneficial in burns, shock, major surgery, prevention of postoperative venous thrombosis, chronic stable claudication and possibly in acute stroke and retinal vein thrombosis. Plasma exchange may be beneficial in severe Raynaud's phenomenon. Defibrination with ancrod is effective in prevention and treatment of venous thrombosis but its role in arterial disease is unproven. The benefits of streptokinase therapy in venous thrombo-embolism and acute myocardial infarction may be partly rheological, due to fibrinogen depletion. Drugs with rheological effects may be beneficial in intermittent claudication.

Placebo-controlled, double-blind study of haemodilution in peripheral arterial disease

Twenty-four men who had stable claudication with long, collateralized femoropopliteal obstructions were treated by isovolaemic haemodilution and sham dilutions in a double-blind, placebo-controlled, crossover study. 3 weeks of haemodilution lowered haematocrit and blood viscosity and increased resting blood flow and pain-free walking distance. Sham treatment produced no such favourable changes. It is concluded that haemodilution therapy can be clinically effective in patients with arterial obstructions in the legs. It seems particularly promising when the vascular obstructions are such that low average shear stresses act on the blood in multiple, long collaterals.

Thallium 201 muscle scintigraphy: application to the management of patients with arterial occlusive disease

Skull (S), thigh (T), and calf (C) scintigraphies were performed by using 2 mCi thallium 201 IV in 30 patients suffering from stages II, III, and IV arterial occlusive disease (Fontaine's classification). Two indexes were calculated: P = T/C-C/S (T/C and C/S were the absolute values of radioactivity ratios measured before medical treatment) and R = delta(C/S)-delta(T/C) (where delta expressed the relative variation of the ratios measured after treatment and compared with initial values). Angiography was performed on all patients prior to treatment, and the results were quantified as 1 in the case of obliteration and 0.5 in case of stenosis of major arterial axes. Clinical improvement was demonstrated by a 100% increase in walking distance for stage II disease, abolition of pain at rest for stage III disease, and reepithelialization of trophic lesions for stage IV disease. Paraclinical effectiveness was evaluated by measuring ankle systolic pressure (SP) and index (SI) before and after treatment. The correlation observed between the values of P and angiography results was p less than 0.025 (Student t-test). The mean of P (measured before treatment) was 1.75 for the improved patients and 0.56 for the others (p less than 0.005). After treatment, R was +58% for improved patients versus -13% in those in whom the treatment was inefficient (p less than 0.025). P expresses the microcirculatory effects of arterial lesions detected by angiography. It is a prognostic index: satisfactory proximal perfusion (high T/C), associated with lesions that are essentially peripheral (low C/S), predicting a positive effect of medical treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of fibrinogen, globulin, albumin and hematocrit on the kinetics of erythrocyte aggregation in man

The effects of fibrinogen, globulin, albumin, and packed blood cell volume (hematocrit) on the kinetics of erythrocyte aggregation (RBC-A) after stasis were quantitatively evaluated by recording the changes of light transmission through the blood in transparent tubing with an apparatus consisting of a light-emitting diode and a silicon photodiode. The measurements were done on samples of heparinized whole blood, suspensions of erythrocytes containing various concentrations of fibrinogen (0.5 to 25 g/L) or gamma globulin (25 to 150 g/L), and blood of various hematocrit values prepared from three samples of whole blood having different concentrations of fibrinogen. The half-time of the increase of light transmission after the flow-stop was used as an index of the kinetics of RBC-A (T1/2). This simple and rapid method for estimating erythrocyte aggregation had excellent reproducibility (N = 51, r = 0.99). The values of T1/2 showed significant negative correlations with the concentrations of fibrinogen and globulin but a positive correlation with that of albumin. The T1/2 value decreased markedly and then remained almost constant with increase in the value of hematocrit, but the influence of hematocrit on T1/2 was markedly dependent on the concentration of fibrinogen.

Haemoglobin concentration and linear cardiac output, peripheral resistance, and oxygen transport

Increasing the haemoglobin concentration results in increased oxygen transport at the cost of increased blood viscosity. This suggested the concept of an optimum packed cell volume for maximising oxygen transport and a study was therefore conducted seeking supportive evidence. Linear cardiac output was measured as minute distance by Doppler ultrasound in 40 patients with haemopoietic disorders who had stable haemoglobin concentrations ranging from 30 to 200 g/l. The correlation between haemoglobin concentration and minute distance (r = -0.45; p less than 0.01) was negative, and correlations between haemoglobin concentration and mean blood pressure (r = 0.66; p less than 0.001) and haemoglobin concentration and peripheral resistance (r = 0.64; p less than 0.001) were positive. Calculated oxygen transport increased across the whole range of haemoglobin values. These results suggest that adjustment of peripheral resistance in response to oxygen availability overrides the influence of blood viscosity on cardiac output and that the optimum packed cell volume for oxygen transport is the highest that can be achieved.

The effect of normovolaemic haemodilution on the early patency rate of small calibre vascular prostheses studied in a new animal model

A new animal model has been developed to study early thrombosis in small calibre vascular prostheses. It consists of an ePTFE graft 2 cm long and of 3mm internal diameter inserted into a rabbit abdominal aorta in which the distal run-off is reduced by narrowing both common iliac arteries using clips with a standard gap. Scanning electron microscopy and in vivo gamma imaging of the graft using labelled autologous platelets showed that, as in the human, platelets played a primary role in the model graft thrombosis. This model was used to study the effect of haemodilution on early graft patency. Moderate normovolaemic haemodilution dramatically improved the early patency rate.

[Intentional normovolemic hemodilution in the medical treatment of lower limb arteritis]

Thirty patients suffering from arterial occlusive disease (stages II, III or IV of Fontaine's classification) were treated by isovolaemic haemodilution (IDH). Most of these patients received conventional medical treatment without success (negative selection). Angiography was performed on all patients prior to treatment. 500 ml of whole blood was withdrawn from each patient. 250 ml of dextran 40 mixed with 250 ml of 5% albumin solution was injected intravenously to avoid hypovolaemia. This procedure, carried out three or four times, was repeated until a haematocrit of 0.30 was reached. This haematocrit level of 0.30-0.35 was maintained for 60 days. The measurement of ankle systolic pressure, systolic index at rest, treadmill performance and lower limb thallium-201 muscular scintigraphy were used to assess laboratory efficiency. On the sixtieth day, 14 patients (46%) showed clinical improvement, nine were stable and arterial occlusive disease worsened in seven patients. Clinical improvement persisted for several months (15 months in one case). Clinically, it seemed that patients treated by IHD showed improvement of their arterial occlusive disease. However, the prediction of the chances of success of IHD, as well as the quantification of results by common laboratory examination, were difficult. Muscular scintigraphy with thallium-201 gave a good assessment as well as a quantifiable analysis of results.

Improved reactive hyperemia test after plasma exchange in familial hypercholesterolemia

By using a non-invasive methodology of vascular diagnosis, ECG-triggered strain-gauge plethysmography, 5 patients with familial hypercholesterolemia (FH) (3 homozygous, 2 heterozygous) were evaluated before and during the 1st and 2nd week after plasma exchange (PE). In order to obtain data on the responsiveness to vasodilating stimuli in FH patients undergoing PE, reactive hyperemia test and peak flow determination were also performed. Resting arterial flow over the calf was found to be significantly enhanced after PE. Reactive hyperemia test demonstrated persistent improvement of peak flow following exchange. This study demonstrates useful hemodynamic effects of PE in patients with FH.

Effect of nitroglycerin on blood rheology in healthy subjects

Transdermal nitroglycerin (Nitroderm TTS 5) and a placebo were applied to 10 healthy male volunteers for 10 days. Before the first application and 6, 24, 48, 96, and 240 h thereafter, the viscosity of plasma and whole blood was measured and the packed-cell volume determined. During nitroglycerin application, the viscosity of plasma and whole blood was significantly diminished, and after 10 days it averaged 5% below the initial value. The greater the initial viscosity, the more marked was the drug-induced reduction: in 5 subjects with plasma and whole-blood viscosities near the lower limit of the normal range, there was only a temporary decrease and the values reverted to their initial levels after 4 days; in the other 5 subjects, whose whole-blood viscosities were near the upper limit of the normal range, a 10% reduction was still demonstrable after 10 days. In those subjects all values measured throughout the 10-day observation period were significantly below the initial values. The haematocrit readings followed the same pattern as the alterations in viscosity. It can be assumed, therefore, that the decrease in viscosity induced by nitroglycerin results from "internal haemodilution". The clinical relevance of the changes observed is discussed. The improvement in the rheological properties of the blood may contribute to the anti-anginal effect of Nitroderm TTS.

Haemodilution for major vascular surgery--using 3.5% polygeline (Haemaccel)

Intra-operative haemodilution and autotransfusion was carried out in 32 patients having major vascular surgery. The intra-operative blood loss and peri-operative blood replacement was compared with that in 25 patients having similar surgery in whom haemodilution was considered to be contraindicated. Both groups of patients had similar mean intra-operative blood loss measured but homologous blood transfusion requirements were significantly different; 2.6 units (SD 1.9) in the haemodiluted patients compared with 6.0 units (SD 3.5) in the non-diluted patients. There was no mortality in the haemodiluted patients nor was any morbidity attributed to the procedure. Polygeline (haemaccel) was used as the diluent and proved satisfactory for this purpose.

Effect of venesection on calf blood flow in polycythaemia

Calf blood flow at rest and during postocclusive reactive hyperaemia was measured using an electrocardiogram-triggered plethysmograph in 14 patients with polycythaemia (nine with primary disease and five with polycythaemia secondary to cyanotic heart disease) before and after a course of venesection. The mean packed cell volume was reduced from 0.57 to 0.47, and whole-blood viscosity fell by 50% at low shear rates. Venesection did not affect rest flow, but peak flow was increased by 18%. The increase in peak flow failed to compensate for the reduced haemoglobin content of the blood, calculated haemoglobin delivery being reduced by 23% at rest and 10% during reactive hyperaemia. These results indicate that while venesection improves blood viscosity, this does not necessarily lead to improved delivery of oxygen to the tissues.

Cerebral blood flow and blood viscosity in patients with polycythaemia secondary to hypoxic lung disease

Blood viscosity, cerebral blood flow (CBF) and cerebral oxygen carriage (CBF X arterial oxygen content) were measured in 12 patients with polycythaemia secondary to hypoxic lung disease. CBF and cerebral oxygen carriage were both significantly higher than in a comparative group of 20 patients with raised packed cell volumes and normal lung function. The patients with secondary polycythaemia then underwent venesection and their mean packed cell volume fell from 0.613 to 0.495. This led to a consistent reduction in blood viscosity, which fell by 44% at a low shear rate (0.67/s) and 33% at a high shear rate (0.91/s). CBF rose by 21% (p less than 0.01), but cerebral oxygen carriage did not significantly increase in the group as a whole. Four of the patients with secondary polycythaemia had complained of episodes of confusion before venesection, which improved considerably once the packed cell volume had been lowered. Headache was relieved in a further two patients and none of the subjects was adversely affected by venesection. It was not possible, however, to show a correlation between symptomatic improvement and an increase in cerebral oxygen carriage.

Use of isovolemic hemodilution in the management of arterial ischemia in patients with polycythemia

The management of patients with both polycythemia and limb-threatening ischemia presents many difficulties because in this population, vascular surgical procedures carry a particularly high incidence of hemorrhagic and thromboembolic complications. We evaluated the use of acute isovolemic hemodilution in 12 polycythemic patients who required urgent surgery due to severe ischemia and threatened limb loss. Within 48 hours, blood was withdrawn in units of 500 ml and simultaneously replaced with 1,500 ml of lactated Ringer's solution until a hematocrit of 35 to 40 percent was achieved. After hemodilution, two patients had such a marked improvement that no further therapeutic measures were required immediately. Four patients showed definite improvement in pulmonary vascular resistance tracings and segmental Doppler pressures, but ischemia was not fully ameliorated. These patients together with the remaining six patients underwent vascular surgery within 1 to 14 days after hemodilution. A hematocrit of 32 to 40 percent was maintained during the perioperative period. All arterial reconstructions were successfully completed and there were no perioperative failures. No pulmonary emboli, myocardial infarctions, or deaths occurred in this period. These results indicate that in polycythemic patients, urgent vascular surgery can be performed more safely with the concomitant use of acute isovolemic hemodilution.

Clinical relevance of blood viscosity and red cell deformability including newer therapeutic aspects

Peripheral ischemia is mostly due to narrowing of the vessels, although blood supply is also influenced by the hemorheologic properties of the blood. Recent research has revealed that abnormally high blood viscosity can be a contributing cause in ischemia. Therapeutically decreasing the blood viscosity improves the ischemia by increasing flow through the narrowed vessels and may as such offer a valuable alternative to surgery. Different possible therapeutic approaches for decreasing blood viscosity and the related clinical evidence are discussed.

Untoward effects of blood transfusion: common problems and simple safeguards

Potential transfusion reactions include hemolysis, disease transmission (particularly hepatitis), allergic and febrile reactions, and symptoms of circulatory overload. Limiting the number of transfusions given to patients for whom the procedure will achieve some clearly defined clinical goal is one way of reducing the number of adverse reactions. When transfusion is to be carried out, great care should be taken in correctly identifying both patient and blood to avoid ABO mix-ups, and thorough pretransfusion laboratory testing should be done. During and after transfusion the patient should be closely observed for complications.

Blood rheology

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