Clinical and experimental studies of intraoperative autotransfusion using a new filtration device.

The Haemocell S-350 device has recently been introduced for intraoperative autotransfusion. The system uses a novel membrane filter to process shed blood. In the first part of this study a 0.2-micron pore size filter was used in a randomized trial comparing the use of autotransfusion (n = 8) with bank blood controls (n = 9) during aortic reconstruction. This part of the trial was abandoned because of unexpected non-surgical bleeding. Bank blood requirements fell from a median of 3.0 (range 0.0-9.0) units to 1.5 (range 0.0-7.0) units when autotransfusion was used, but these patients had a greater perioperative blood loss (1791 (range 932-3104) versus 1140 (range 440-3840) ml). There was evidence of postoperative heparin excess with an activated partial thromboplastin time ratio of 1.3 (range 0.9-3.0) versus 1.0 (range 1.0-1.2) in controls and an activated clotting time of 206 (range 143-280) versus 137 (range 107-142) s. This was confirmed by raised plasma heparin levels and a prolonged thrombin time normalized by protamine. To improve performance a 0.6-micron pore size filter was studied in ten patients. Filtration efficiency doubled from 19 to 38 per cent. Electron micrographs demonstrated better filter clearance, but 44 per cent of the original concentration of heparin remained in the reinfusate. The S-350 device may be an attractive alternative to centrifugation for intraoperative autotransfusion but, until efficiency is improved, it should only be used for cardiovascular surgery when excess heparin can be reversed with protamine.

A multicenter study of popliteal aneurysms. Joint Vascular Research Group.

PURPOSE: The purpose of this study was to determine current practice in the treatment of all categories of popliteal aneurysms (PA) in light of the efficacy of intraarterial thrombolysis in PA presenting as acute ischemia. METHODS: Prospective data collected from 19 vascular surgeons from 200 PA in 137 patients during a 4-year period from 1989. RESULTS: The most common presentation (125 PA) was leg ischemia, with the most severe symptom being claudication in 58, acute limb-threatening ischemia in 56, and digital atheroembolism in 11 limbs. The nonischemic group (75 PA) included 43 symptom-free cases and 32 cases with local symptoms arising from the popliteal fossa. Of 62 patients requiring emergency treatment, bypasses were done in 56, 10 of whom had early occlusion. Thrombolysis was used alone or in combination with bypass on 23 occasions, with 16 successful outcomes. Of 138 PA presenting electively, 80 underwent bypass, with one early occlusion, and 58 were observed. In the observed group, 18 later underwent bypass during a median follow-up of 22 months. The indications for late bypass were expansion of a small (< 2 cm) asymptomatic PA and the development of distal ischemia. There were 18 deaths in the observed group because of medical unfitness; limb ischemia did not develop during follow-up. CONCLUSIONS: Intraarterial thrombolysis is of value in restoring the distal run off before bypass in PA presenting as acute limb-threatening ischemia. However, the results do not justify an expectant policy for asymptomatic aneurysms.

Haematocrit measurements during cardiopulmonary bypass surgery: comparison of three stat methods with a blood cell counter.

Monitoring packed cell volume (PCV) is essential to safeguard oxygen delivery to the tissues during cardiopulmonary bypass (CPB). We compared the results obtained using a PCV monitor, a blood gas analyser and a microcentrifuge with those from a laboratory-based automated blood cell counter. PCV was measured in 221 samples of 40 patients undergoing open-heart surgery. The limits of agreement (mean difference +/- 2 SD) was unacceptably wide when the results obtained with the PCV monitor and the blood gas analyser were compared with those of the automated blood cell counter. This was most pronounced when PCV was measured in low concentration samples. The microcentrifuge showed good limits of agreement regardless of sample concentration. The data suggests that measurement of PCV by either continuous monitoring or by a blood gas analyser is not an accurate alternative to an established laboratory method. The microcentrifuge is the most accurate method of the ones investigated to measure haematocrit during CPB.