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Biomedical subjects

M J Ray

Publications and source records attributed to M J Ray.

At least 37 records · Page 2Linked to original sources
PubMed1994

The effect of oral anticoagulant therapy on APTT results from a bedside coagulation monitor.

OBJECTIVE: The Ciba Corning 512 coagulation monitor (CC512) can be used to monitor heparin therapy by performing an activated partial thromboplastin time (APTT) at the patient's bedside. This study was designed to compare the CC512 results to results using the laboratory system. The relative sensitivities of both systems to the effect of oral anticoagulant therapy also was investigated. METHODS: Activated partial thromboplastin times were performed with both the CC512 and laboratory system on 74 specimens from patients receiving i.v. heparin therapy, and on 14 specimens from patients on warfarin only. Heparin assays were performed on 43 of the specimens from the heparinized patients. RESULTS: When a patient was receiving heparin only, the APTT results of the CC512 proved to be similar to existing laboratory methods. The CC512 APTT results of patients on warfarin only were markedly prolonged, whereas the laboratory APTTs were only slightly affected. CONCLUSION: The CC512 results were comparable to the laboratory system. However, the CC512 APTT was more sensitive to the effect of warfarin than the laboratory APTT system used in this study. CC512 APTT results on a patient receiving both oral and intravenous anticoagulation could be misleading.

Administration, Oral↗
PubMed1994

Relationship of platelet aggregation to bleeding after cardiopulmonary bypass.

Excessive bleeding after cardiopulmonary bypass operations is a persistent problem. This study assessed the influence of platelet function on blood loss for 134 patients undergoing cardiopulmonary bypass. Platelet function was measured by platelet aggregation in platelet-rich plasma and whole blood using collagen as the agonist. Adenosine triphosphate release was assessed concurrently. Measurements were made 1 day before operation and 1 hour after the cessation of cardiopulmonary bypass. Three important findings were made. First, statistically significant correlations were shown between preoperative and postoperative platelet aggregation and blood drainage for the first 3 hours postoperatively. Second, correlations were greatest when preoperative measurement was performed on whole blood and postoperative measurement was performed on platelet-rich plasma. Third, patients with reduced postoperative platelet aggregation in platelet-rich plasma had significantly greater transfusion requirements in the first 24 hours postoperatively. In defining the 16 patients who bled excessively among the 134 patients studied, the preoperative aggregation in whole blood had a sensitivity of 62%, specificity of 75%, positive predictive value of 26%, and negative predictive value of 94%. The postoperative aggregation in platelet-rich plasma had a sensitivity of 86%, specificity of 69%, positive predictive value of 28%, and negative predictive value of 97%. These results indicate that preoperative and postoperative measurement of platelet aggregation may provide a rationale for the prophylaxis or treatment of patients to reduce blood loss after cardiopulmonary bypass.

Adenosine Triphosphate↗
PubMed1994

Relationship of fibrinolysis and platelet function to bleeding after cardiopulmonary bypass.

In order to study the effects of cardiopulmonary bypass (CPB) on fibrinolysis and platelet function and the possible relationship of these effects on post-operative blood loss, 127 patients undergoing CPB were examined. There was a significant reduction in the median levels of fibrinogen, plasminogen, alpha 2-antiplasmin, fibrinolytic potential and platelet aggregation during CPB (P < or = 0.001). Median levels of soluble fibrin, fibrinogen degradation products, D-dimer and PAI-1 were increased, while the level of t-PA activity remained constant. Post-CPB levels of fibrinogen and plasminogen correlated negatively with blood loss (P = 0.003 and P < 0.001, respectively) and interestingly, lower levels of alpha 2-antiplasmin and higher levels of t-PA activity before CPB were associated with greater blood loss after CPB (P < 0.001 and P = 0.004, respectively). Better pre-CPB platelet function correlated with lower levels of D-dimer before and after CPB. As expected, haemodilution had a significant effect on fibrinolytic and coagulation parameters post-CPB; the greater the haemodilution, the more the concentration of fibrinogen, plasminogen and alpha 2-antiplasmin fell post-CPB and the greater the blood loss. The increase in PAI-1 levels intra-CPB appeared to result in mean t-PA activity remaining unchanged 1 h post-CPB. Post-CPB increases in soluble fibrin were paralleled by increases in fibrinogen degradation products and D-dimer, suggesting that intra-operative contact activation is related to activation of the fibrinolytic system. The present findings indicate the greater the fibrinolytic activation, the greater the post-CPB blood loss.

Adolescent↗
PubMed1993

A low volume specimen container suitable for monitoring the aPTT of heparinized patients.

Differences in the activated partial thromboplastin time (aPTT) were shown when blood taken from patients receiving intravenous heparin therapy was collected into 5 ml and 1 ml citrate containers. Mean aPTTs were 27% shorter with the plasma from the 1 ml citrate containers (n = 23). These results were paralleled by a 37% reduction in the mean heparin concentration (n = 11) and a 77% increase in the mean platelet factor 4 (PF4) concentration (n = 7). This phenomenon is due to increased platelet activation and subsequent increased heparin neutralization in the 1 ml citrate container. In an attempt to overcome this, the citrate was removed from a 1 ml container and replaced with a buffered tri-sodium citrate solution containing theophylline, adenosine and dipyridamole anticoagulant (CTAD). Blood from heparinized patients taken into both 5 ml citrate and 1 ml CTAD showed a correction of the shortening artefact in the low volume container. The mean aPTT of plasmas from the 1 ml CTAD container showed an increase of 10% compared with the 5 ml citrate. There was no significant difference in the mean heparin or PF4 concentrations of blood taken into either container. The 1 ml CTAD tube described is a suitable collection container for monitoring heparin in neonates or patients who are difficult to venepuncture and overcomes the neutralization of heparin in part filled low volume containers.

Blood Specimen Collection↗
PubMed1991

The suitability of the Australasian reference thromboplastin for use on an automated centrifugal analyser.

The Australasian Reference Thromboplastin (ART) is now produced in a low turbidity form (ART-LT) for use in photo-electrical coagulometers. This study was designed to assess the suitability of ART and ART-LT for use on a fully automated centrifugal analyser, the ACL300 Research (ACL). These reagents were compared to Thromborel S (TRL), the reagent currently in successful use in our laboratory. It was found that regular ART was an unsuitable reagent for the ACL due to poor daily quality control testing (QC) precision at an INR of 4.5. The ACL also had the effect of significantly altering the ISI of ART from its recommended value as determined for manual testing. ART-LT was found to be an acceptable reagent on the ACL even though its QC precision was lower than that of TRL. The reagent was stable throughout its 8 wk shelf-life. The ACL significantly altered the ISI (International Sensitivity Index) of ART-LT. This may no longer be a disadvantage, as ART-LT is now provided with an ISI specifically for its use on the ACL.

Blood Coagulation Tests↗
PubMed1990

A 70-kDa apolipoprotein designated ApoJ is a marker for subclasses of human plasma high density lipoproteins.

A new apolipoprotein, termed apolipoprotein J (apoJ), was purified from human plasma by immunoaffinity chromatography. ApoJ is a glycoprotein consisting of disulfide-linked subunits of 34-36 and 36-39 kDa. Each subunit is glycosylated and has a pI range of 4.9-5.4. ApoJ exists in the plasma associated with high density lipoproteins (HDL) and specifically with subclasses of HDL which also contain apoAI and cholesteryl ester transfer protein activity. Immunoaffinity purified apoJ-HDL subclasses have apparent molecular masses of 80, 160, 240, 340, and 520 kDa, as determined by gradient gel electrophoresis. By negative staining electron microscopy, apoJ-HDL range in diameter from 5 to 16 nm. Fractionation of plasma by vertical gradient density centrifugation revealed apoJ-HDL in HDL2 (d 1.063-1.125 g/ml) with the majority overlapping HDL3 (d 1.125-1.21 g/ml) and very high density lipoprotein (d 1.21-1.25 g/ml). The bimodal density distribution of apoJ-HDL suggests that these subclasses have a unique metabolic relationship and may play a role in the transport of cholesterol from peripheral tissues to the liver.

Antibodies, Monoclonal↗
PubMed1990

The dependence of the International Sensitivity Index on the coagulometer used to perform the prothrombin time.

This study was designed to detect any effect that different types of coagulation instrument may have on the International Sensitivity Index (ISI) of a thromboplastin. Manufacturers of commercial thromboplastins now calibrate their reagents against the World Health Organization international reference preparation to assign them an ISI. This enables the prothrombin time (PT) estimated with that reagent to be expressed as an International Normalised Ratio (INR). One batch of Thromborel S was calibrated against the Australasian Reference Thromboplastin (ART). The Thromborel S was used on three photo-optical instruments, the Automated Coagulation Laboratory (ACL) (Instrumentation Laboratory), the Cobas Fibro (Roche), and the Coag-a-Pet (General Diagnostics). PTs using ART were performed manually using the reference method. The ISIs calibrated in our laboratory when the ACL and Cobas Fibro were used were not significantly different at the 95% level, being 1.102 +/- 0.018 and 1.134 +/- 0.022 respectively. The ISI with the Coag-a-Pet of 1.223 +/- 0.023 was significantly different to that of the ACL and the Cobas Fibro at the 95% level. The flowcharts for a computer program to perform the necessary calculations are provided. The program allows for the entry and editing of data from the calibration procedure, and provides a mean normal PT and normal range, the ISI and 95% confidence limits of the calibration, and a chart for the conversion of the test PTs to INRs. The authors have made available an IBM compatible program for the calibration of thromboplastins.

Blood Coagulation Tests↗
PubMed1989

Intraoperative glucose infusion and blood lactate: endocrine and metabolic relationships during abdominal aortic surgery.

The hypothesis that increased intraoperative blood lactate depends both on intraoperative glucose supply and inadequate tissue oxygenation occurring during surgery was tested in anesthetized patients undergoing infrarenal abdominal aortic surgery. Twenty surgical patients received either Ringer's solution or 5% glucose solution for intraoperative volume loading. Arterial blood lactate, arterial glucose, hemodynamic variables, insulin, glucagon, cortisol, epinephrine, and norepinephrine were determined preoperatively and intraoperatively. There were no significant changes in hemodynamic values, glucagon, norepinephrine, and epinephrine compared with control values in both groups. Oxygen consumption decreased only during aortic clamping. Cortisol and lactate increased significantly 10 min after aortic clamping until the end in both groups. Glucose 5% solution infusion resulted in significantly greater blood lactate accumulation and significantly greater blood glucose and insulin levels, whereas there were no changes in the patients receiving Ringer's solution. From control until aortic clamping, lactate and glucose were significantly correlated with each other in both groups; after aortic clamping until the end of the procedure, the correlation remained constant in patients in the Ringer's group, whereas no relationship could be demonstrated in those in the glucose group. The authors conclude that intraoperative glucose administration increases intraoperative blood lactate and that blood lactate accumulation depends both on glucose supply and tissue oxygen deficit. Furthermore, none of the hemodynamic metabolic and endocrine factors were reliable for assessing tissue perfusion and metabolic demands during surgery.

Anesthesia, General↗
PubMed1989

A comparison of two APTT reagents which use silica activators.

The Ortho activated partial thromboplastin time (APTT) reagent, Thrombosil 1 (TS), was compared to the General Diagnostics automated APTT reagent (GD). TS produced more precise results over a 38-day period of testing a normal control plasma, indicating that the upper limit of the normal range could be more precisely set with TS. This normal range was better represented if the normal values with both reagents were logarithmically transformed before calculating the mean +/- 2 SD. TS was more sensitive to plasma which had been heparinized in vitro. This was also demonstrated in vivo by the testing of 100 plasmas from heparinized patients. On testing of in-vitro dilutions of normal plasma with factor-deficient plasmas, TS was more sensitive to decreasing levels of factors VIII, IX and XI but less sensitive to decreasing factor XII. This was demonstrable in vivo in 71% of cases with plasmas from factor-deficient patients. GD was more sensitive to the lupus anticoagulant in most cases.

Blood Coagulation Factors↗
PubMed1988

Charcoal bezoar. Small-bowel obstruction secondary to amitriptyline overdose therapy.

Nasogastric administration of activated charcoal is effective in decreasing the half-life of amitriptyline. A case is reported in which this therapy for amitriptyline overdose led to charcoal bezoar formation and small-bowel obstruction. Amitriptyline's atropinic side effects on the gut make this a possible complication in such patients.

Adult↗
PubMed1987

Hepatolithiasis complicated by cholangiocarcinoma.

A case of hepatolithiasis complicated by intrahepatic cholangiocarcinoma is reported. Awareness of this association is important for the radiologist, who may detect clinically occult malignancy in patients with intrahepatic biliary calculi.

Adenoma, Bile Duct↗