A comparative study of prostacyclin infusion given before and during cardiopulmonary bypass to assess the first pass effect of the circuit on platelet number and function.

Platelet damage during cardiopulmonary bypass (CPB), although proportional to the duration of bypass, may result in significant dysfunction after the initial contact with an extracorporeal circuit, the so-called 'first pass' phenomenon. The platelet sparing effect of prostacyclin (PGI2) infusion was studied in a double-blind randomized trial on male patients undergoing coronary artery bypass grafts to assess the effect of the 'first pass' through the CPB circuit. Prostacyclin infusion was begun before the onset of CPB or during CPB in two groups which were compared to a placebo control group. A standardized anaesthetic, surgical and perfusion technique were used. Preoperatively and during surgery at pre-set intervals, whole blood platelet aggregation was studied using ADP and collagen agonists. Platelet numbers and function measured by ADP aggregation were conserved in the two PGI2 groups. There was no significant difference between the treated groups. We conclude, therefore, that the initial contact of platelets with the CPB circuit, in the absence of PGI2 did not irreversibly affect platelet function. In addition, the hypotensive action of PGI2 was easier to control once on bypass. It may therefore be preferable to delay PGI2 infusion until CPB has been established.

Clostridium difficile in haematological malignancy.

Twenty patients with haematological malignancies who developed Clostridium difficile bowel infection or colonisation are described. All isolates of C difficile were toxigenic in vitro and faecal cytotoxin (toxin B) was detected in 20/26 episodes. Ten of 20 episodes with detectable faecal cytotoxin were associated with typical antibiotic associated diarrhoea. In the other 10 episodes (nine patients), there was a severe unusual illness which was associated with detection of C difficile. The unusual features of the illness were pronounced jaundice (total bilirubin greater than or equal to 44 mumol/l), abdominal pain and distension, and initial constipation followed either by diarrhoea or by large bowel stasis. Four of these patients died within seven days. Bacteraemia was often a presenting feature in neutropenic patients subsequently shown to have C difficile. This was not the case in non-neutropenic patients. Bacteraemia was commonly polymicrobial and in two cases C difficile was isolated from blood culture. The clinical implications of recognition of this atypical C difficile associated syndrome are discussed.