R. C. Kester

ALLOGENEIC VERSUS AUTOLOGOUS BLOOD DURING ABDOMINAL AORTIC ANEURYSM SURGERY

OBJECTIVES To determine if cell-salvaged autologous blood can serve as an alternative to homologous blood, and to examine the incidence of infected complications and length of postoperative stay. DESIGN A prospective randomised study comprising autologous and homologous blood transfusions in patients undergoing elective infrarenal abdominal aortic surgery. METHODS Fifty patients undergoing AAA surgery were prospectively randomised to homologous blood (n = 27), or autologous blood transfusion (n = 23), using a cell salvage autotransfusion device. RESULTS The haemoglobin at the time of hospital discharge was similar for both groups (11.0 vs. 10.8 g/dl) with no difference in perioperative mortality. The length of stay was reduced in those patients who received autologous blood (9 days vs. 12 days, p < 0.05 Mann-Whitney U test). There were four infected cases in the autologous group and 12 in the homologous group (p = n.s., Fishers exact probability test). However, patients who received 3-4 units of homologous blood had an increased risk of infection compared to those who received a similar amount of autologous blood (50% vs. 0%). CONCLUSIONS Cell salvage autologous blood can safely replace, or at least decrease, exposure to homologous blood transfusion, with a reduction in the mean hospital stay.

The Influence of Platelet Inhibition on the Patency of Femoro-Popliteal Dacron Bypass Grafts

Neointimal hyperplasia and thrombosis initiated by platelet activity may contribute to the failure of femoropopliteal Dacron bypass grafts. We have therefore undertaken a randomised prospective double blind trial comparing the efficacy of a combination of acetyl salicylic acid (ASA) 330 mg and dipyrida mole (DPM) 75 mg three times daily, with placebo in maintaining the patency of femoropopliteal Dacron bypass grafts implanted to relieve disabling claudica tion. Patients received either ASA/DPM or placebo commencing pre-opera tively and continuing for 12 months. Seventy-three double velour (Microvel) grafts in 65 patients were studied, 38 grafts in the placebo group and 35 grafts in the active group. The following were measured pre-operatively and at 3, 6, 9 and 12 months postoperatively: maximum walking distance (MWD); ankle/bra chial systolic pressure index (ABSPI); graft patency; platelet adhesion and ag gregation; template bleeding time; ASA and DPM levels. After 1 year, 10 patients had been withdrawn (9 ASA/DPM: 1 placebo) and 4 out of 26 grafts in the active group and 15 out of 37 in the placebo group had occluded ( P < 0.05 Chi square test). We conclude that inhibition of platelet function by the use of a combination of ASA and DPM improved the patency rate of femoropopliteal Dacron bypass grafts.

The histological measurement of laser-induced thermal damage in vascular tissue using the stain picrosirius red F3BA

A histological technique for the measurement of laser-induced thermal tissue damage is described using the stain picrosirius red F3BA. This stain enhances the birefringence of normal collagen when viewed in polarized light. Areas of (thermally) denatured collagen, however, have no optical activity and can be measured directly by optical micrometry. The technique has been applied to experimental studies on both laser angioplasty and laser vascular anastomosis.The tissue ablation characteristics of various 2.2 mm diameter rounded sapphire laser angioplasty probes were compared by lasing (at 1064 nm) segments of porcine aorta under blood in vitro. A marked difference was observed between probes from different manufacturers, the Surgical Laser Technologies probe producing significantly greater forward tissue ablation with less associated lateral thermal damage.The relative degree of thermal damage caused by argon (488/514 nm) and Nd-YAG lasers during in vitro arteriotomy repair was also investigated. No difference was seen between the two wavelengths. However, the use of absorption-enhancing chromophore dyes as an aid to laser welding significantly reduced damage, particularly for the argon laser.In conclusion, we suggest that this histological technique is of considerable value in the investigation of the thermal effects of continuous-wave lasers.

Effect of preclotting on the porosity and thrombogenicity of knitted Dacron® grafts

The effects of single- and four-stage preclotting methods on graft porosity and thrombogenicity were compared in two types of Dacron prosthesis. The single-stage method significantly reduced leakage of blood (P less than 0.001), but did not seal the grafts. The four-stage method rendered the grafts impermeable at the second step. Thrombogenicity was compared by perfusing preclotted grafts with fresh heparinized blood (containing 111In-labelled platelets) in an artificial circulation. Platelet deposition and consumption were significantly less in the four-stage method whilst platelet function remained unchanged during perfusion. We conclude that the four-stage technique is superior to standard preclotting methods by rendering knitted Dacron grafts impermeable and hypothrombogenic.

The regulation of neutrophil activation and adhesion during femorodistal bypass surgery

OBJECTIVE To determine the effect that revascularising chronic critically ischaemic legs has no neutrophil activation and adhesion. DESIGN Prospective clinical study. SETTING University Hospital. MATERIALS Twenty-five patients, 16 men and nine women undergoing femorodistal surgery. CHIEF OUTCOME MEASURES Venous blood assays for neutrophils expression of CD11b, neutrophil adhesion, and the plasma concentration of the shed endothelial adhesion receptor, soluble intracellular adhesion molecule 1 (sICAM-1). Urinary microalbuminaemia was measured and expressed as an albumin/creatinine ratio (ACR), as a marker of vascular permeability and plasma neutrophil elastase as evidence of neutrophil activation. Venous blood was taken preoperatively, during surgery and for the first 7 days postoperatively. MAIN RESULTS Neutrophil CD11b expression fell following reperfusion of the limb (21.4 mcf to 9.7 mcf, p < 0.02 Mann Whitney U-test) as did neutrophil adhesion (preop. 75% adhesion, postop. 28% p < 0.01). However, the plasma elastase levels rose from 95 micrograms/l to 345 micrograms/l at 4 h and the ACR increased from 5.3 mg/ml to 304.2 mg/ml. The concentration of sICAM-1 fell following reperfusion (p < 0.04). CONCLUSION The change in CD11b, sICAM-1 and adhesion may represent a normal immunological response to ischaemia/reperfusion.

Treatment of digital ischaemia associated with chemotherapy using the prostacyclin analogue iloprost.

Digital ischaemia is a recognised complication of both malignant disease and chemotherapy. Its onset may prevent further treatment and lead to tissue loss. We report a case of severe digital ischaemia in a patient with advanced breast carcinoma undergoing cytotoxic chemotherapy. This was successfully treated with Iloprost, a prostacyclin analogue.

Laser welding for coronary artery anastomosis: techniques, temperature profiles and the role of chromophores.

Laser vascular anastomosis is a developing technique which aims to employ the thermal effect of laser energy to achieve tissue fusion with minimal thermal damage. The tissue temperature necessary to achieve effective bonding is debated and must be related to the mechanism of fusion. Enhanced energy absorption at the anastomosis using chromophore (CR) dyes may improve technical success. Over 300 arteriotomies in porcine coronary arteries were welded in vitro using Argon (488/5 14 nm) and Nd:YAG (1060 nm) lasers with or without chromophore. Bursting pressures under saline infusion were measured and tissue temperatures during welding recorded using infrared thermal imaging. Results were as follows. Argon - CR (mmHg) [mean (s.e.)]: 249 (28). Argon + CR: 280 (22). Nd:YAG - CR: 1 5 1 (23). Nd:YAG + CR: 27 1 (30). The use of chromophore therefore increased the weld bursting strength for both lasers but this effect was statistically significant only for the Nd:YAG (p< 0.05, oneway ANOVA). Argon welds were stronger than Nd:YAG welds (p<0.O5) but this difference lost significance when chromophore was used. All welds required temperatures of around 100 degC to be effective and was inconsistent below 80 degC. In conclusion, vascular anastomoses produced by laser can withstand suprasystolic pressures. The effect of chromophore is to improve weld strength and consistency and furthermore, to visibly reduce thermal damage and facilitate beam aiming. These are considerable technical advantages.

Percutaneous laser recanalisation of femoropopliteal occlusions using continuous wave Nd-YAG laser and sapphire contact probe delivery system

A conventional continuous wave Nd-YAG medical laser system delivered by transparent sapphire tipped optical fibres was used for percutaneous recanalisation of 32 chronic femoropopliteal occlusions in 27 patients (19 men, eight women; median age 68 years, range 46-83 years). Twenty-four patients had severe intermittent claudication and three had critical ischaemia. The median occlusion length was 8 cm (range 3-35 cm) and lesions were not negotiable by guidewire. Laser energy was delivered at powers of 10-15 Watts using intermittent 1 second emissions (mean total energy 315 Joules, range 30-1015]). The sapphire tips used were 1.8 to 3.0 mm diameter. After laser recanalisation adjunctive balloon dilatation was necessary to widen the resulting lumen. All patients received anti-platelet therapy. Initial clinical success was achieved in 22 limbs (69%) with symptomatic relief and increase in mean (+/- S.D.) ankle-brachial pressure ratio from 0.52 (+/- 0.25) to 0.80 (+/- 0.21) [Mann-Whitney U, p < 0.001]. Recanalisation was unsuccessful in all calcified lesions (four cases). There was a high incidence of vessel perforation (28%) and wall dissection (25%). Emergency surgery was not required after failed procedures. The median follow-up was 12 months (range 6-20 months). By 6 months, 15 of 22 successfully recanalised lesions (68%) had reoccluded. The cumulative primary patency at 1 year was only 12%. These disappointing results do not support routine use of this system. Clearly, modifications of the laser/delivery system or the technique, or both, are required. The aim should be to achieve sole laser recanalisation without concomitant balloon dilatation.

Laser vascular anastomosis―preliminary evaluation of a new anastomotic technique

Laser vascular anastomosis (laser welding) is a developing technique that em ploys the thermal effect of laser energy to achieve fusion of apposed vessel edges. The authors have attempted to establish a definitive technique by an investiga tion of the physical properties of laser welds. Porcine coronary arteriotomies were repaired in vitro by two different laser wavelengths (Argon [488/514 nm] and Nd:YAG [1064 nm]) and by use of chromophore dyes to enhance energy absorption at the anastomosis. Anastomatic bursting strength was measured directly by means of saline infusion and vessel constriction (caused by diffusion of heat from the weld) assessed by a constant-pressure flow rate model. Histo logic techniques were also employed to estimate the degree of thermal damage to the vessel. In all these respects optimal results were obtained by the Argon laser and use of the chromophore Basic Fuchsin. These repairs all burst at greater than 200 mmHg and were minimally constricted. Thermal tissue damage was accurately confined to the anastomotic site. This technique will, therefore, be employed in future studies.

Isotope limb blood flow measurement in patients undergoing peripheral laser angioplasty

A technique of isotope limb blood flow (ILBF) measurement employing Technetium-labelled human albumin and a gamma camera, was used to assess limb perfusion in 19 patients undergoing percutaneous laser angioplasty, both before and one month after treatment. Twenty-three limbs with femoro-popliteal occlusions ranging in length from 3-35 cm (median 8 cm) were recanalized using an Nd-YAG laser and sapphire tipped optical fibre. Primary angiographic success was achieved in 19 lesions of which 6 re-occluded within the first month, and 13 remained patent with relief of symptoms. Clinically successful procedures were associated with a large increase in ILBF. However, normal blood flow was restored in only 54% of limbs. There was a slight decrease in limb perfusion after failed laser angioplasty but this was not statistically significant in this small series. Furthermore, there was no clinically apparent circulatory compromise, or need for urgent surgical bypass in failed cases. We conclude that ILBF is a useful means of assessing patients undergoing laser angioplasty, particularly for detecting small flow changes in patients who are unable to complete a standard exercise test. Its use can be recommended for assessing blood flow changes following other forms of limb revascularization.