The pharmacokinetics and UK usage of heparin in vascular intervention

Abstract

Intravascular heparin is used routinely during peripheral and visceral angioplasty, although usage and dose vary widely. The aims of this prospective study were to: (1) Determine the pattern of Heparin usage by Vascular/Interventional Radiologists in the UK. (2) Determine the optimum doses of Heparin for vascular intervention on the basis of its pharmacokinetic profile. A questionnaire was sent to Consultant Radiologists who were also members of the British Society of Interventional Radiology (BSIR), regarding their use of heparin during peripheral angioplasty. This included heparin doses in flushing solution, timing and amounts of heparin used as a bolus dose and monitoring of clotting times. Seventy-three percent returned completed forms. A wide variation in practice was shown. Apart from the variety of individual protocols in use, significant findings were that more than 75% of the respondents were giving heparin as a bolus only after the lesion had been crossed with a guide-wire. None of the respondents were monitoring clotting times, even in prolonged and complicated procedures. The pharmacokinetic profiles of two separate bolus doses of heparin in two groups of 30 and 25 patients each were then evaluated. Our results showed that a 3000 IU bolus of heparin maintained the plasma APTT in the therapeutic range (at least twice the normal value), for at least 30 min in the majority of patients. A 5000 IU bolus maintained the APTT in the therapeutic range for 45 min in the vast majority of patients. Apart from minor bruising at the compression site and slightly increased compression times in a small number of patients, no significant immediate complication was noted. We conclude that in the context of peripheral angioplasty, there is a wide variation in the use of heparin as an adjunct to the procedure. In the light of our own experience we recommend a 3000 IU intra-arterial bolus of unfractionated heparin to be given once arterial access has been achieved. This would cover short, uncomplicated procedures. The larger 5000 IU dose would be more appropriate for longer and more complicated procedures. We also recommend monitoring APTT values in prolonged procedures, with administration of further bolus doses of heparin if required.