Arterial graft maturation: The duration of thrombotic activity in Dacron aortobifemoral grafts measured by platelet and fibrinogen kinetics

Dacron is thrombogenic, hence small arterial grafts of this material frequently thrombose in the period prior to graft maturation. Anti-thrombotic therapy may therefore be indicated to preserve patency during this risk period. To evaluate the thrombogenicity of immature Dacron grafts, platelet and fibrinogen kinetics using 51Cr and 125I respectively were measured before operation and at 3, 6 and 9 months in 10 patients following aortobifemoral bypass and in 6 age-matched volunteers.

Platelet survival was reduced from 8.8±0.2 d before surgery to 7.4±0.24 d at 3 months. This was accompanied by an increase in platelet turnover from 39±2.4 × 109 l−1 d−1 to 46.9±2.9 × 109 l−1 d−1. Fibrinogen t1/2 fell from 3.72±0.13 d preoperatively to 3.36±0.11 d at 3 months, while fibrinogen fractional catabolic rate rose from 0.27±0.014 to 0.34±0.014. These changes were all significant (P < 0.01). Fibrinogen consumption had returned to normal by 6 months following surgery but platelet kinetics only equated to pre-operative levels at 9 months. We suggest that Dacron grafts are thrombogenically active for about 9 months. When anti-thrombotic therapy is indicated it should be continued throughout this period.

Alteration in platelet function in patients with early breast cancer

The aim of this study was to examine our hypothesis that platelets of patients with breast cancer were functionally altered compared to healthy controls. The results have shown that the platelets from women with early breast cancer released significantly more vascular endothelial growth factor (VEGF) when stimulated with thrombin, tissue factor, clotting, or over a period of time. Similarly, release of thrombospondin (TSP) with thrombin and tissue factor was higher, but failed to reach a significant level. Thus, the observed differences in platelet response support our hypothesis, but warrant further work to determine the reason underlying the observed difference and potential clinical relevance of our findings.

Effect of Superficial Venous Surgery on Venous Function in Chronic Venous Insufficiency

Patients with chronic venous insufficiency often have combined superficial and deep venous incompetence. The aims of this study were to determine the effects of superficial venous surgery (SVS) on deep venous haemodynamics and on ambulatory venous pressure (AVP) and to determine if the AVP tourniquet test can predict the effect of SVS. Of 119 legs, 42 legs (32 subjects) with chronic venous insufficiency, healed ulceration, or active ulceration and with combined superficial and deep incompetence underwent preoperative duplex imaging and AVP measurement followed by appropriate SVS. Four months later, all underwent postoperative duplex imaging and AVP measurement. The pressure relief index (PRI) was calculated from the AVP measurement as an overall assessment of venous function. Seventeen of 119 (14%) showed no tourniquet improvement in PRI and were therefore excluded from SVS. Of those suitable for SVS, median (range) age was 56 (32-78) years. Twenty-two limbs underwent long saphenous surgery, four limbs short saphenous surgery, and 16 limbs both, based on duplex findings. Segmental deep incompetence resolved in 11/21 (52%) limbs after surgery compared to 6/21 (29%) with multisegment incompetence. Median (range) PRI improved from 319 (4-1,600) preoperatively to 1,300 (360-2,670) postoperatively (p < 0.001, Wilcoxon). PRI with thigh tourniquet correlated with postoperative PRI (r = +0.828, p = 0.01, Spearman), as did calf tourniquet (r = +0.996, p = 0.004) and both tourniquets (r = 0.535, p = 0.046). The majority of patients with combined superficial and deep incompetence can be selected for SVS on the basis of AVP measurement with tourniquets. SVS can improve segmental deep incompetence and PRI in those properly selected.

Spatial distribution of mast cells in chronic venous leg ulcers

Chronic venous leg ulcers (CVUs) show chronic inflammation but different pathological changes occur in different parts of the ulcer. There is a lack of re-epithelialisation and defective matrix deposition in the ulcer base but epidermal hyperproliferation and increased matrix deposition in the surrounding skin. The role of mast cells in wound healing, inflammation, fibrosis and epidermal hyperproliferation has been extensively studied but less is known about their role in CVUs. In the present study, we investigated the distribution of mast cells in CVUs with specific consideration of the differences between the ulcer base and the skin surrounding the ulcer. Both histochemical and immunohistological methods were used to detect the mast cell marker tryptase in frozen sections of CVU biopsies. Mast cells were counted in the dermis of normal skin, in the ulcer base and in the skin surrounding the ulcer. Double immunofluorescence staining was used to study the location of mast cells in relation to blood vessels. In normal skin few mast cells were seen in the dermis but none in the epidermis. However in CVUs there was a significant increase in intact and degranulated mast cells in the surrounding skin and ulcer edge (184 per field, p<0.003) of CVUs and a significant reduction in the ulcer base (20.5 per field p<0.05) in comparison to normal skin (61 per field). In CVUs mast cells showed a characteristic location near the epithelial basement membrane whilst mast cell granules and phantom cells (mast cells devoid of granules) were predominantly seen in the epidermis. In the dermis, mast cells were seen associated with blood vessels. The marked increase in mast cells in the surrounding skin of CVUs and depletion of mast cells in the ulcer base could implicate mast cell mediators in the pathological changes in CVUs particularly in the epidermal and vascular changes occurring in the surrounding skin.

Does washing swabs increase the efficiency of red cell recovery by cell salvage in aortic surgery?

BACKGROUND AND OBJECTIVES

We investigated the contribution of swab washing to the efficiency of red cell recovery by intraoperative cell salvage (ICS) in 10 patients undergoing elective aortic aneurysm repair.

MATERIALS AND METHODS

Volumes and haemoglobin (Hb) concentrations were recorded in the blood recovered by direct suction and from washed swabs, both before and after processing with a Haemonetics Cell Saver 5.

RESULTS

The mean +/- standard deviation (SD) estimated blood loss was 991 +/- 403 ml, resulting in a mean +/- SD salvaged RBC volume of 380 +/- 124 ml. The median [interquartile (IQR) range] Hb collected from suction was 84.9 (61.8-131.4) g, of which 50.1 (45-71.5) g was returned to the patient after processing, a median yield of 68 (49-77)%. The swab wash produced a median (IQR) Hb of 39.4 (28.4-64.9) g, of which 26.2 (16.8-31) g was reinfused, a 67 (33-98)% yield. Swab wash thus contributed with a median (IQR) of 31 (24-39)% of the total RBC recovery.

CONCLUSIONS

Washing swabs improves the efficiency of red cell recovery by ICS.

Mild and moderate varicose vein reflux does not deteriorate over time

Objective: To prioritize varicose vein (VV) waiting lists, superficial venous reflux was timed in patients with primary VVs using hand-held Doppler (HHD) and classified as 'severe' (≤4s), 'moderate' (>4; ≤6s) or 'mild' (>6s). Only patients with severe reflux were offered surgery. The progression of reflux in those not offered surgery was investigated over two years.

Methods: Patients seen in the VV clinic between November 1999 and October 2000 with reflux ≥4s were re-assessed two years later. Reflux was timed at the saphenofemoral (SFJ) and saphenopopliteal (SPJ) junctions using HHD. Patients completed a basic symptom questionnaire. The severity of VVs and skin changes of venous insufficiency were graded.

Results: In all, 38/54 patients attended for review at two years. There were 44 limbs with 48 sites of reflux, 38 at the SFJ and 10 at the SPJ. Reflux improved at 27 sites, remained the same at five and deteriorated at 16. Reflux became 'severe' in eight limbs, but only four patients requested surgery. Median (interquartile range) reflux time was 6.0 (5–6)s in 1999–2000 and 7.0 (4–10)s in 2002 ( P = 0.13). Median symptom scores for aching and the severity of VV remained unchanged. The cosmetic appearance of VV and skin signs of venous insufficiency significantly improved ( P < 0.01).

Conclusions: Mild and moderate reflux did not deteriorate in most VV patients. HHD may be a useful adjunct to grade venous reflux and prioritize patients for VV surgery.

Regional haemoglobin oxygen saturation during surgical haemorrhage

AIM

Experimental research and early clinical studies have shown that regional haemoglobin desaturation, measured by near infrared spectroscopy (NIRS), follows blood loss. To further assess NIRS as a blood loss monitor, we evaluated it on patients undergoing major surgery.

METHODS

Regional haemoglobin oxygen saturation from the cerebral cortex (CsO(2)) and the left gastrocnemius muscle (PsO(2)) was continuously monitored with an INVOS 4100 NIRS oximeter in 10 patients during surgery. Haemoglobin, mean arterial pressure, arterial and central venous oxygen saturation and tension, temperature, pH and lactate concentration were also measured.

RESULTS

The median (IQR) blood loss was 650 (400-1 800) ml, equivalent to 16% (11-35) of the patients' blood volume. During surgery, CsO(2) fell by a mean (95% CI) of 8.4% (2-14.8) (p=0.016) and PsO(2) fell by a mean (95% CI) of 3.3% (-1.5-8.1) (p=0.16). CsO(2), but not PsO(2), correlated with the volume of blood lost (R=0.44; p=0.004), central venous oxygen saturation (R=0.52; p=0.001), and venous oxygen tension (R=0.58; p<0.001). These correlations remained significant after calculations were adjusted for changes in arterial pressure, temperature and pH.

CONCLUSION

Cerebral, but not peripheral, haemoglobin oxygen saturation decreases proportionally to blood loss and correlates with measurements of systemic oxygen extraction. With further research, NIRS measurements of CsO(2) may be developed into a useful tool to monitor blood loss.

Early Carotid Surgery in Acute Stroke: A Multicentre Randomised Pilot Study

BACKGROUND

Standard practice has been to delay carotid endarterectomy (CEA) for 2 months following acute stroke to avoid a perceived risk of cerebral haemorrhage. We investigated whether early CEA reduces early recurrent stroke and improves outcome in partial anterior circulation infarction (PACI).

METHODS

Patients with PACI and a Barthel score of >18 before stroke underwent carotid duplex and CT imaging within 7 days of stroke. Forty consenting patients fit for surgery with greater than 70% ipsilateral carotid stenosis were randomised, 19 to 'early' (within 24 h) and 21 to 'delayed' surgery (at 8 weeks). Modified Rankin and Barthel scores were recorded at 1 week, 2 months, 6 and 12 months.

RESULTS

Rankin scores improved more rapidly following 'early' surgery to a score of 1 (0-4) at 2 and 6 months compared with 2.5 and 2 (1-4), respectively, for delayed surgery (p < 0.05). Barthel scores were also significantly improved following 'early' CEA at 7 days but both groups reached a median score of 20 by 2 months. Four 'delayed' and 3 'early' patients suffered extension or recurrence of neurological deficits with 1 death in each group.

CONCLUSIONS

Early CEA within 7 days of ischaemic stroke improved functional outcome with earlier hospital discharge. A large multicentre study is needed to exclude the possibility that 'early' CEA increases the risk of cerebral haemorrhage or death.

Carotid endarterectomy improves cognitive function in patients with exhausted cerebrovascular reserve

OBJECTIVE

To investigate changes in cognitive function following carotid endarterectomy (CEA).

DESIGN

Prospective study with controls.

METHODS

CEA patients (n=159) were compared to a urology surgery control group (n=20). In CEA patients cerebrovascular reserve (CVR) was measured preoperatively. During surgery emboli and blood flow velocity in the middle cerebral artery were measured by transcranial Doppler (TCD) and cerebral oxygen saturation (CsO2) by near infrared spectroscopy. Cognitive function was measured preoperatively and at 5 days and 8 weeks postoperatively using a standardised computer battery of tests.

RESULTS

Only 8% of patients had normal CVR bilaterally. The median number of emboli during CEA was 12 (range 0-181). On carotid clamping, TCD velocity fell a median of 41% and cerebral oxygen saturation by 5%. Attention deteriorated compared to controls 5 days following CEA (p=0.003) and this deterioration was related to the rise in TCD velocity on declamping (r=-0.3, p=0.002). Median attention reaction times improved significantly by 8 weeks (p=0.001) especially in patients' with severely impaired CVR before surgery (p=0.02).

CONCLUSIONS

Attention improved at 2 months following CEA in patients with impaired CVR. CEA may offer more than reduced stroke risk to patients with impaired CVR.

Pharmacological prevention of cardiac risk in claudicants with ischaemic heart disease

BACKGROUND

Claudicants rarely progress to critical limb ischaemia but have a threefold increase in mortality, mainly due to cardiac disease. Antithrombotic therapy, beta blockers, ACE inhibitors and statins have been shown to reduce mortality and cardiovascular morbidity in patients with ischaemic heart disease.

AIM

To investigate secondary pharmacological prevention of ischaemic heart disease in claudicants.

MATERIALS AND METHODS

We prospectively recorded comorbidity and drug treatment in 89 patients (67 men and 22 women) with a history of ischaemic heart disease recruited in a supervised exercise and lifestyle modification programme to improve claudication distance and prognosis.

RESULTS

Of the 89 cases, 40 had a history of angina only and 49 of myocardial infarction. Sixteen (18%) had diabetes, 47 (53%) had hypercholesterolaemia and 52 (58%) were hypertensive. Antithrombotic therapy was prescribed to 61 patients (68.5%), 64 (72%) with a history of myocardial infarction and 27 (67.5%) with angina only (p = 1). Beta-blockers were prescribed to 12 (13.5%) patients only, seven (15%) with a history of myocardial infarction and five (12.5%) with angina only (p = 1). Of the 47 patients with hypercholesterolaemia, 29 (62%) were on a statin.

CONCLUSION

Secondary pharmacological prevention of ischaemic heart disease in claudicants remains suboptimal, with only two thirds of patients receiving antithrombotic therapy and a small minority receiving beta blockers. Pharmacological prevention in claudicants should improve to reduce cardiac morbidity and mortality.

Soluble adhesion molecules in clinical ischaemic injury

BACKGROUND

Neutrophil adhesion is a prerequisite for ischaemic injury. In vitro research has shown that soluble adhesion molecules have an inhibitory effect on neutrophil binding

AIMS

To determine whether the circulating forms of adhesion molecules are consumed during skeletal muscle ischaemic injury in man.

METHODS

The response of the circulating forms of adhesion molecules ICAM-1 (intercellular adhesion molecule-1) and L-selectin to ischaemia and reperfusion was investigated in 23 patients during surgery involving aortic cross-clamping and in 20 volunteers with tourniquet-induced forearm ischaemia.

RESULTS

In the aortic model the levels of circulating ICAM-1 fell from an initial value of 250 +/- 20 to 210 +/- 13 ng/ml (p < 0.05) and soluble L-selectin fell from 642 +/- 62 to 487 +/- 49 ng/ml during ischaemia (p < 0.05). There was a similar pattern of reduced levels of circulating adhesion molecules in the model of forearm ischaemia. However the recovery of these molecules during the reperfusion period differed between the two models.

CONCLUSIONS

Soluble L-selectin and soluble ICAM-1 appear to be utilised during clinical models of ischaemia. This supports previous in vitro studies suggesting a role in competitive inhibition and these circulating molecules may be clinically important inhibitors of leukocyte adhesion.

Venous disease is associated with an impaired range of ankle movement

OBJECTIVES

to investigate the relationship between clinical severity of venous disease, calf muscle pump dysfunction and range of ankle movement (ROAM).

MATERIALS AND METHODS

ROAM was assessed by goniometry in the supine, nonweightbearing position. Calf muscle pump function was assessed by ambulatory venous pressure (AVP), calculating the pressure relief index (PRI). Venous disease was classified according to the CEAP classification (International Consensus Committee reporting standards on venous disease). Forty seven limbs in 38 adults were recruited and matched for age: 11 normal controls CEAP(0), 12 varicose veins CEAP(2), 12 chronic venous insufficiency CEAP(4,5) and 12 active ulceration CEAP(6).

RESULTS

mean (S.E.M.) age was 60.7 (1.3) years. Mean (S.E.M.) PRI was 1959.6 (313.7) in CEAP(0), 905.3 (139.3) in CEAP(2), 596.5 (148.5) in CEAP(4,5) and 170.6 (69.0) in CEAP(6) (p < 0.001, ANOVA). Mean (S.E.M.) ROAM was 61.3 (2.0) degrees in CEAP(0), but significantly reduced to 49.7 (2.0) in CEAP(2), 42.1 (2.6) in CEAP(4,5) and 40.9 (2.7) in CEAP(6) (p < 0.004, ANOVA post hoc Tukey). PRI correlated with ROAM (p < 0.001, Pearson correlation coefficientr = 0.52).

CONCLUSIONS

limbs with venous hypertension have a reduced range of ankle movement related to the clinical severity of venous disease.

Surgery for venous insufficiency: are venous function tests necessary?

Background

The role of duplex imaging and measurement of ambulatory venous pressure (AVP) in the preoperative assessment of patients with venous insufficiency (VI) and primary varicose veins (VV) was investigated.

Methods

Venous incompetence was confirmed by duplex imaging in 58 legs: 38 had VI, demonstrated by eczema, oedema or pigmentation, and 20 had VV and normal skin. AVP was measured from a cannulated dorsal foot vein before and after ten tip-toe exercises. This was repeated following occlusion of the superficial veins by narrow tourniquets. Pressure relief index (PRI) was calculated as the fall in AVP in calf exercise × 90 per cent refilling time in seconds. The criterion for superficial vein surgery was doubling of PRI on superficial vein occlusion.

Results

Superficial venous incompetence (SVI) was confirmed in all legs with duplex imaging. Deep vein incompetence (DVI) was found in 17 legs (45 per cent) with VI and in two (10 per cent) of the VV legs (P = 0·012, χ2 test). Venous function was normal (PRI greater than 1000) in six. Median PRI in patients with VI and VV was 177 and 289, rising to 717 and 1026 respectively after superficial vein occlusion. Initial PRI was significantly lower in patients with DVI (P &lt; 0·001). PRI improved by 135 per cent in SVI and by 318 per cent in legs with DVI (P = 0·01). PRI did not double following superficial venous occlusion in 20 legs (35 per cent) with SVI and in three (16 per cent) with deep incompetence (P = 0·01).

Conclusion

Clinical examination and duplex imaging alone cannot predict who will benefit most from superficial venous surgery. AVP measurement rationalizes decision-making and may avoid unnecessary operations.

Autologous or homologous transfusion in aortic surgery: randomized trial

Background

Aortic surgery often requires blood transfusion, which may cause complications and postoperative infection. Autologous transfusion was evaluated in a multicentre clinical trial.

Methods

Some 145 patients undergoing elective aortic surgery in eight hospitals were randomized to either ‘homologous’ or ‘autologous’ transfusion, a combination of acute normovolaemic haemodilution (ANH) and intraoperative cell salvage. Homologous blood was administered when the haemoglobin concentration fell below 8 g dl−1.

Results

Median (interquartile range (i.q.r.)) blood loss was 668 (400–862) ml or 17 (10–24) per cent of blood volume in aortobifemoral bypass, and 1120 (765–1700) ml or 24 (17–36) per cent in aneurysm repair (P &lt; 0·001). Autologous transfusion reduced homologous blood requirements from a median (i.q.r.) of 2 (0–4) units to 0 (0–2) units (P = 0·008). Independent predictors of blood transfusion were homologous transfusion strategy (odds ratio (OR) 2·3 (95 per cent confidence interval 1·1–5·0); P = 0·03), low preoperative haemoglobin concentration (OR 3·7 (1·7–8·2); P &lt; 0·001), prolonged surgery (OR 2·1 (1·0–4·8); P = 0·05) and blood loss (OR 3·0 (1·4–6·5); P = 0·007). Patients with a preoperative haemoglobin concentration greater than 13·5 g dl−1 and who lost less than 20 per cent of their blood volume rarely required transfusion. There was no significant difference between the groups in terms of morbidity, mortality and postoperative hospital stay.

Conclusion

Autologous transfusion reduced the need for homologous blood in aortic surgery, but was useful only in patients with low haemoglobin levels or when blood loss exceeded 20 per cent of the blood volume. ANH alone is indicated for patients undergoing aortobifemoral bypass and in those with a higher haemoglobin level and blood volume.

Prognosis following venous thromboembolism in women taking combined oral contraceptives

Background

It is widely believed that ‘post-thrombotic limb’ always follows deep vein thrombosis (DVT). Prognosis following both DVT and pulmonary embolism (PE) was investigated.

Methods

Some 155 women (mean age 25·5 (range 16–49) years) who developed venous thromboembolism while taking third-generation oral contraceptives were studied. The venous system was assessed by duplex imaging a mean of 4·8 years after DVT.

Results

Fourteen (15 per cent) of 96 women suffering PE died. Of the 82 surviving patients, 12 (15 per cent) had chest pain and/or dyspnoea at rest or on exertion. Of the 103 women with confirmed DVT, 59 (57 per cent) had had only calf thrombosis and 44 (43 per cent) had had iliofemoral vein thrombosis. At follow-up, 13 (22 per cent) and 21 (48 per cent) women with calf and iliofemoral thrombosis respectively had leg symptoms, including swelling, pain and lipodermatosclerosis (P = 0·011). Duplex imaging was normal in 60 patients (58 per cent). There was no significant difference in leg symptoms (31 versus 34 per cent) or incompetence on duplex imaging (41 versus 42 per cent) between those who were anticoagulated for 3 months (n = 39) or 6 months (n = 64) respectively. Leg symptoms were more frequent in the 41 women with DVT discharged without elastic stockings, affecting 19 (46 per cent) compared with only 15 (24 per cent) of 62 discharged with stockings (P = 0·034).

Conclusion

The majority of women regained venous patency and became asymptomatic, despite extensive DVT. Elastic stockings were often omitted despite the evidence of long-term benefit.

Prosthetic femoropopliteal bypass: randomized comparison of polytetrafluoroethylene and heparin-bonded Dacron

Background

Dacron was largely abandoned for femoropopliteal bypass 30 years ago as saphenous vein achieved better patencies. As patency in prosthetic above-knee (AK) femoropopliteal bypass in patients on aspirin is equivalent to that with saphenous vein, heparin-bonded Dacron (HBD) and polytetrafluoroethylene (PTFE) have been compared in a randomized trial involving ten hospitals which also included below-knee (BK) popliteal or tibioperoneal trunk bypass where the long saphenous vein was absent or inadequate.

Methods

Over a 28-month recruitment period, 209 patients undergoing femoropopliteal bypass (180 AK, 29 BK) were randomized by the method of minimization to HBD (n = 106) or PTFE (n = 103). Aspirin 300 mg day−1 was started before surgery and continued unless the patient was intolerant.

Results

Mean follow-up was 34 (range 19–48) months. Fifteen patients (7 per cent) died with patent grafts and three (1 per cent) infected grafts were removed. Patency (measured by Kaplan–Meier survival analysis) was 70, 63 and 55 per cent at 1, 2 and 3 years for HBD, compared with 56, 46 and 42 per cent respectively for PTFE (P = 0·0444). Patency at 3 years for AK bypass was significantly better than that for BK bypass. A total of 70 interventions were performed on 47 patients, achieving long-term patency in only three. Amputations were performed in 23 patients, six with HBD and 17 with PTFE grafts (P = 0·015, Fisher's exact test).

Conclusion

In femoropopliteal bypass, primary patency was better with HBD than PTFE, and HBD was associated with a lower amputation rate.

Carotid sinus nerve blockade during carotid surgery: a randomised controlled trial

OBJECTIVES

we investigated whether carotid sinus nerve infiltration with lignocaine reduced blood pressure lability during the first 24h following carotid endarterectomy (CEA).

DESIGN

prospective randomised double-blind controlled trial.

MATERIALS

eighty patients undergoing CEA for significant symptomatic stenosis of the internal carotid artery.

METHODS

after initial dissection, 5 ml of 1% lignocaine or normal saline placebo according to randomisation was infiltrated around the carotid sinus nerve. Blood pressure was measured by intra-arterial cannula during surgery and for four hours afterwards every 15 min, then manually, hourly for 18 h.

RESULTS

patients having excision of the carotid sinus nerve were grouped separately for analysis: 29 patients had lignocaine, 33 placebo and 17 excision (one early death with incomplete data was excluded). Mean systolic, diastolic and pulse pressures did not differ significantly between the three groups before carotid sinus nerve infiltration. After infiltration, those patients who had carotid sinus nerve excision, had significantly higher systolic [mean (SD)=155 (16)mmHg] and diastolic [75 (9)mmHg] pressures than those receiving LA [systolic=136 (15)mmHg, diastolic=65 (10)mmHg] or placebo [systolic=136 (19)mmHg, diastolic=65 (9)mmHg], (p<0.005 ANOVA). Nerve excision also resulted in wider variability of blood pressure as defined by the mean of individual standard deviations (systolic=25 mmHg, diastolic=13 mmHg) compared to LA (systolic=19 mmHg, diastolic=12 mmHg) or placebo (systolic=18 mmHg, diastolic=10 mmHg) (p<0.05 ANOVA). Normotensive patients had significantly lower mean diastolic pressures (p<0.001 ANOVA) and variability (p<0.05) if they received lignocaine although this did not influence pulse pressure.

CONCLUSIONS

lignocaine injection of the carotid sinus nerve has no benefit in those patients with existing treated hypertension and only marginal effects in normotensives. It is more important to preserve the carotid sinus nerve if possible.

Cerebral and peripheral near-infrared spectroscopy: an alternative transfusion trigger?

BACKGROUND AND OBJECTIVES

To develop a transfusion trigger based on tissue oxygenation, near-infrared spectroscopy (NIRS) was evaluated in a model of compensated haemorrhage.

PATIENTS AND METHODS

Regional haemoglobin oxygen saturation from the cerebral cortex (CsO2) and the gastrocnemius muscle (PsO2) was monitored (using an INVOS 4100 near-infrared oximeter) in 30 patients during acute normovolaemic haemodilution to a target haemoglobin of 11 g/dl. Arterial oxygen saturation, end-tidal carbon dioxide tension, mean arterial pressure and haemoglobin concentration were also measured.

RESULTS

During blood collection, CsO2 and PsO2 fell by a mean (95% CI) of 8 (5.3-10.7)% (P < 0.001) and 5.5 (3.2-7.8)% (P < 0.001), respectively. Arterial pressure and oxygen saturation did not change, whilst the end-tidal carbon dioxide tension fell by 2.3 (0.8-3.8) mmHg (P = 0.004). Haemoglobin concentration correlated with CsO2 (R = 0.76, P < 0.001) and PsO2 (R = 0.63, P < 0.001), as did the volume of blood removed.

CONCLUSIONS

CsO2 and PsO2 fell predictably during compensated blood loss. With further research, NIRS may be developed into a transfusion trigger.

Relationship between plasma markers of endothelial cell integrity and the Framingham cardiovascular disease risk-factor scores in apparently healthy individuals

Separate reports have identified differences in plasma levels of the endothelial markers soluble E-selectin, von Willebrand factor (vWf) and soluble thrombomodulin in each of the major modifiable risk factors for atherosclerosis (smoking, hypertension and hypercholesterolaemia), and abnormal levels of some plasma markers predict various adverse cardiovascular events. However, it is unclear whether there is an increasing effect on the endothelium with a worsening risk-factor profile. We measured the three endothelial cell markers by enzyme-linked immunosorbent assay in the plasma of 200 subjects (mean age, 54 years; 58% men) free of the symptoms and clinical signs of atherosclerosis. Levels of the markers were then correlated with the Framingham coronary heart disease (CHD) and cerebrovascular disease (CVD) scores to help determine which (if any) may be useful as good laboratory predictors of future cardiovascular events in prospective epidemiological studies. vWf correlated with CHD (r(s) = 0.269, < 0.001) and CVD risk (r(s) = 0.331, P < 0.001), but soluble E-selectin correlated only with CHD risk (r(s) = 0.163, P = 0.021). We conclude that, of the three specific endothelial markers, vWf correlates most closely with the Framingham risk-factor prediction scores and therefore may be the better plasma endothelial marker of the future development of an atherothrombotic event.