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Biomedical subjects

Ian Mackie

Publications and source records attributed to Ian Mackie.

8 recordsLinked to original sources
PubMed2006

Transfusion triggers in orthotopic liver transplantation: a comparison of the thromboelastometry analyzer, the thromboelastogram, and conventional coagulation tests.

OBJECTIVES: The Thromboelastogram (TEG; Haemoscope Corporation, Niles, IL) and the ROTEM thromboelastometry analyzer (Pentapharm GmbH, Munich, Germany) are coagulation monitors that measure the viscoelastic changes accompanying whole-blood coagulation generation and lysis. It is not clear whether TEG and ROTEM transfusion algorithms suggest similar blood component intervention. This study aims to report the extent to which administration of platelets, fresh frozen plasma, and cryoprecipitate would be indicated using protocol-dictated interventions by the Rotem, TEG, and conventional coagulation screens during orthotopic liver transplantation (OLT). DESIGN: Prospective observational study. SETTING: University hospital. PARTICIPANTS: Twenty patients undergoing orthotopic liver transplantation. INTERVENTIONS: Coagulation was managed with native TEG protocols. Additional samples for kaolin TEG, kaolin heparinase TEG, Rotem in-TEM, Rotem hep-TEM, Rotem fib-TEM, full blood count, prothrombin time, and Clauss fibrinogen assays were taken at 5 fixed operative stages. MEASUREMENTS AND MAIN RESULTS: Results were reviewed and protocol-indicated interventions recorded. There was moderate agreement between Clauss fibrinogen and Rotem fib-TEM assays about fulfilling fibrinogen transfusion criteria (kappa = 0.42, p < or = 0.05). Agreement between TEG and Rotem to transfuse platelets was fair (Rotem in-TEM/native heparinase TEG, kappa = 0.33, Rotem in-TEM/kaolin heparinase TEG, kappa = 0.28). There was moderate agreement between Rotem in-TEM and prothrombin time (kappa = 0.42), and poor agreement between other tests about the point to administer fresh frozen plasma. CONCLUSIONS: Transfusion practice is likely to differ according to the method of coagulation monitoring used. A prospective case-matched study using the viscoelastic tests used in this study would be beneficial in determining the optimal therapy. Rotem fib-TEM monitoring may improve hemostasis management.

Blood Coagulation Tests↗
PubMed2006

Successful management of pregnancy in women with a history of thrombotic thrombocytopaenic purpura.

Pregnancy is an initiating event for acute thrombotic thrombocytopaenic purpura (TTP). There is a high risk of relapse during pregnancy and of foetal morbidity. We describe five cases with successful maternal and foetal outcomes in patients with a history of TTP. Cases 1 and 2 presented with TTP in their first pregnancy and had second-trimester foetal losses. Case 3 had four TTP relapses and soon after achievement of clinical remission became pregnant. Case 4 presented with TTP and left-sided stroke in pregnancy. ADAMTS-13 activity was less than 5% at presentation in four patients and prior to therapy during pregnancy in cases 1-4. Case 5, who had a single acute episode of TTP and became pregnant 6 years later, had normal ADAMTS-13 activity throughout pregnancy. Only case 3 had evidence of an inhibitor on mixing studies. All five patients underwent close haematological and obstetric monitoring and continued low-dose aspirin throughout pregnancy. Patients 1-4 had regular plasma exchange and received low molecular weight heparin during pregnancy. Patient 4 also received rituximab during the third trimester with no observed maternal or neonatal toxicity. Live healthy infants were delivered in all five cases in the third trimester. These findings suggest that successful pregnancy outcome is achievable in patients with a history of TTP and that patients with severely reduced ADAMTS-13 activity at the onset of pregnancy, necessitates regular plasma exchange during pregnancy.

ADAM Proteins↗
PubMed2005

Platelet hyper-function in acute coronary syndromes.

Previous studies have demonstrated shortened bleeding times in patients with acute coronary syndromes, especially in myocardial infarction (MI). In this study we have investigated platelet hyper-function using the PFA-100 with collagen/adenosine diphosphate and collagen/epinephrine cartridges in 78 patients presenting with acute chest pain. Patients were classified into MI, unstable angina (UA) and non-specific chest pain. All patients received 300 mg aspirin (ASA) more than 2 h before blood samples were collected. Twenty healthy normal subjects were also tested before and 2 h after 300 mg ASA (n = 10). The collagen/adenosine diphosphate closure time was significantly shorter in MI patients (median, 71 s; P = 0.0237) but not in UA patients (median, 81 s; P > 0.05) compared with normal subjects (median, 92.5 s). The collagen/epinephrine closure times were significantly longer in UA patients (median, 233 s) than in untreated controls (median, 125 s; P < 0.0001), as expected, but there was no difference in MI patients (median, 149.24 s; P > 0.05), suggesting that the MI patients were not all responding to ASA. Analysis of a subset of the apparent ASA non-responders (n = 5) by platelet aggregation demonstrated that this was not related to failure of ASA to block cyclo-oxygenase activity. Von Willebrand factor levels were significantly elevated in both UA and MI patients compared with normal subjects (mean, 175.5 and 248.9 versus 89.1 s; P < 0.0001 and P < 0.0001, respectively) and were also significantly higher in the MI group compared with the UA group (P < 0.05). There is evidence for platelet hyper-function and elevated von Willebrand factor levels in the MI group that could explain their decreased responsiveness to ASA on the collagen/epinephrine cartridge.

Administration, Oral↗
PubMed2004

Prosthetic joint infection with Pasturella multocida following cat scratch: a report of 2 cases.

Infection is a known cause of failure in a total joint arthroplasty. Secondary or delayed infections are caused by a wider variety of pathogens, including Gram-negative organisms. Pasturella multocida is a Gram-negative bacillus that forms part of the normal nasopharyngeal and gastrointestinal flora of cats and many other animals. Nontrauma-associated infections also have been reported, but these are more often confined to animal handlers. We report 2 patients who had cat scratch and who developed infection of their total hip arthroplasties with P multocida. Both patients were immunocompromised and required revision of their hip arthroplasty. One patient had 1-stage revision, because infective cause was not obvious at the time of surgery. These patients were followed for 18 months to 2 years after surgery, with good results.

Aged↗
PubMed2002

The expression of prion protein by endothelial cells: a source of the plasma form of prion protein?

The neuronal prion protein (PrPC) is also expressed within peripheral tissues including human blood. The majority of blood PrPC is found within the plasma fraction. We hypothesized that the vascular endothelium could be a source of this PrPC. Reverse transcription polymerase chain reaction demonstrated that both human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (HMEC-1) expressed PrPC mRNA. Flow cytometry confirmed PrPC expression on HMEC-1s and HUVECs (120900 +/- 15058 and 58327 +/- 4577 molecules PrPC/cell respectively), with no upregulation following cellular activation. Confocal immunofluorescence microscopy confirmed that HMEC-1s and HUVECs were positive for PrPC on the plasma membrane. Time-resolved dissociation-enhanced fluoroimmunoassay (DELFIA) analysis of cell culture medium demonstrated a slow constitutive release of soluble PrPC not associated with activation. In contrast to von Willebrand factor antigen, PrPC plasma levels in vivo decrease following desmopressin therapy in patients with von Willebrand disease. Measurement of PrPC plasma levels in patients with varying blood counts demonstrated no association between cell count and PrPC concentration. However, there was a higher level of PrPC in plasma from patients with end-stage renal failure. In conclusion, endothelial cells of both macrovascular and microvascular origin expressed high levels of PrPC which can be constitutively released into the cell culture medium.

Blood Cell Count↗