title: Macroaggregation of platelets in plasma, as distinct from microaggregation in whole blood (and plasma), as determined using optical aggregometry and platelet counting respectively, is specifically impaired following cardiopulmonary bypass in man.
abstract: We determined changes in platelet aggregability following cardiopulmonary bypass, using optical aggregometry to assess macroaggregation in platelet-rich plasma (PRP), and platelet counting to assess microaggregation both in whole blood and PRP. Hirudin was used as the anticoagulant to maintain normocalcaemia. Microaggregation (%, median and interquartile range) in blood stirred with collagen (0.6 micrograms/ml) was only marginally impaired following bypass (91 [88, 93] at 10 min postbypass v 95 (92, 96] prebypass; n = 22), whereas macroaggregation (amplitude of response; cm) in PRP stirred with collagen (1.0 micrograms/ml) was markedly impaired (9.5 [8.0, 10.8], n = 41 v 13.4 [12.7, 14.3], n = 10; p < 0.0001). However, in PRP, despite impairment of macroaggregation (9.1 [8.5, 10.1], n = 12), microaggregation was near-maximal (93 [91, 94]), as in whole blood stirred with collagen. In contrast, in aspirin-treated patients (n = 14), both collagen-induced microaggregation in whole blood (49 [47, 52]) and macroaggregation in PRP (5.1 [3.8, 6.6]) were more markedly impaired, compared with control (both p < 0.001). Similarly, in PRP, macroaggregation with ristocetin (1.5 mg/ml) was also impaired following bypass (9.4 [7.2, 10.7], n = 38 v 12.4 [10.0, 13.4]; p < 0.0002, n = 20), but as found with collagen, despite impairment of macroaggregation (7.2 [3.5, 10.9], n = 12), microaggregation was again near-maximal (96 [93, 97]). The response to ristocetin was more markedly impared after bypass in succinylated gelatin (Gelofusine) treated patients (5.6 [2.8, 8.6], n = 17; p < 0.005 v control), whereas the response to collagen was little different (9.3 v 9.5).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biological Sciences, Manchester Metropolitan University, UK.
authors.forename: V C
authors.initials: VC
authors.lastname: Menys
authors.forename: P R
authors.initials: PR
authors.lastname: Belcher
authors.forename: M I
authors.initials: MI
authors.lastname: Noble
authors.forename: R D
authors.initials: RD
authors.lastname: Evans
authors.forename: G E
authors.initials: GE
authors.lastname: Drossos
authors.forename: R
authors.initials: R
authors.lastname: Pillai
authors.forename: S
authors.initials: S
authors.lastname: Westaby
mesh_terms: D007611:Aprotinin / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology / Q000627:therapeutic use; D001769:Blood; D016063:Blood Loss, Surgical / Q000503:physiopathology; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D003094:Collagen / Q000494:pharmacology; D006629:Hirudins / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D009391:Nephelometry and Turbidimetry; D010949:Plasma; D015539:Platelet Activation; D010974:Platelet Aggregation / Q000187:drug effects; D010976:Platelet Count; D010979:Platelet Function Tests; D011994:Recombinant Proteins / Q000494:pharmacology; D012310:Ristocetin / Q000494:pharmacology
chemical_list: D006629:Hirudins; D011994:Recombinant Proteins; D012310:Ristocetin; D003094:Collagen; D007611:Aprotinin; D001241:Aspirin; C060225:desirudin