Mass volume measurement in severe head injury: accuracy and feasibility of two pragmatic methods.

OBJECTIVE: To assess the clinical feasibility and the accuracy of two pragmatic methods in comparison with a conventional computer based method of measurement of masses from CT. METHODS: Nineteen CT scans of 11 patients with severe head injury, showing 34 traumatic lesions, were examined. The volume of every lesion was digitally measured, then a panel of three examiners independently repeated the measurement using the ellipsoid and the Cavalieri method in random order. RESULTS: All the lesions were identified by all the readers and the mean volume measured by each examiner differed by less than 1.5 ml. The average reading time for each scan was 4 minutes for the ellipsoid and 7 minutes for the Cavalieri method. The average volume of the lesions was 34.2 (SD 35) ml with the digital system, and 38.4 (SD 41) ml and 34.8 (SD 36) ml for the ellipsoid and the Cavalieri readings respectively. The average difference between the applied technique and the digital system was 0.57 (SD 9.99) ml for the Cavalieri direct estimator and 0.20 (SD 15.48) ml for the ellipsoid method. The 95% confidence interval for this difference fell between -2.75 and 3.89 ml for the Cavalieri, and between -4.94 and 5.35 ml for the ellipsoid method. There were 19 lesions >25 ml; the ellipsoid method identified 16 of them, whereas 17 were classified with the Cavalieri method. When considering individual lesions rather than the average volume, discrepancies were detected with both methods. The ellipsoid method was less precise, especially when extracerebral lesions were measured. CONCLUSIONS: Both pragmatic methods are inferior to computer based reading, which is the choice when accurate volume estimation is necessary. However, if a digital volumetric determination of the lesions using a CT computer is not possible, the two pragmatic methods offer an alternative.

Effect of clot-detection methods and reagents on activated partial thromboplastin time (APTT). Implications in heparin monitoring by APTT.

Two automatic coagulometers, ACL 810 (Instrumentation Laboratory), a laser-nephelometric centrifugal analyzer, and KoaguLab 40 A (Ortho Diagnostics), an optical automatic coagulometer, were compared with the manual tilt-tube method for the performance of activated partial thromboplastin time (APTT). Seven commercial APTT reagents were used for duplicate determinations in 30 normal controls, 26 patients with liver disease, and 33 patients on full-dose heparin treatment. Clotting times were longer with the manual method than with ACL 810 and, to a lesser extent, with KoaguLab 40 A. Average imprecision of duplicate determinations (coefficient of variation [CV]) was less with ACL 810 (less than 1.5%) than with KoaguLab 40 A (2.9%) and the manual method (2.4%). Differences in slope of the regression curves of clotting times obtained with the coagulometers over the tilt-tube method were observed with all the reagents tested (P less than 0.01). Transformation of clotting times of controls, patients with liver disease, and patients on heparin therapy to APTT ratios did not eliminate the bias resulting from the different reagents (P less than 0.001) and clot-detection methods (P less than 0.001); in controls, significant (P less than 0.001) reagent-method interaction was also observed. The in vitro heparin sensitivity differed with the APTT reagents evaluated and was influenced by the clot-detection method used. Transformation of APTT ratios of anticoagulated patients to apparent plasma heparin levels--as derived from in vitro dose-response curves--effectively eliminated the bias resulting from the different clot-detection methods but had no effect on the bias resulting from the different APTT reagents. In vitro heparin activity curves thus have little, if any, relevance for the ex vivo monitoring of heparin treatment.

Evaluation of coagulometric assays in the assessment of protein C anticoagulant activity; variable sensitivity of commercial APTT reagents to the cofactor effect of protein S.

In vivo expression of protein C activity is dependent on the availability of the activated protein C (APC) cofactor protein S. In the clinical laboratory, measurement of protein C anticoagulant activity is mostly performed in modified APTT assays. We have evaluated 13 commercial APTT reagents for their sensitivity to the cofactor effect of protein S by comparing APC-dependent clotting time prolongations in normal plasma and in protein S depleted plasma. In normal plasma, the sensitivities of the APTT reagents to the anticoagulant effect of APC were markedly different and correlated with the sensitivity of reagents to factor V and VIII. Reagents containing soy phosphatides appeared more sensitive than reagents containing phospholipid of animal origin. Analysis of dose-response curves obtained in normal plasma distinguished one group of reagents showing clotting time prolongations linearly related to the APC concentrations, a second group showing a log-linear relationship and a third group showing a log-log relationship. In protein S depleted plasma, sensitivity of APTT reagents to APC was in general proportional to that observed in normal plasma. However, for some reagents dose-response curves were qualitatively different in normal and in protein S depleted plasma. With all the APTT reagents, APC-dependent clotting time prolongations corresponding to 30-80% of APC anticoagulant activity observed in normal plasma, were observed in protein S depleted plasma. At variance, in a modified Xa one-stage clotting assay, negligible clotting time prolongations were observed in protein S depleted plasma, indicating that over 90% of the APC anticoagulant activity was protein S dependent in this assay system. Dilution of a relative insensitive APTT reagent effectively increased its sensitivity to the cofactor effect of protein S, suggesting that different phospholipid content and/or composition might be responsible for the different sensitivity of APTT reagents to protein S. These results question the validity of APTT based assays for the identification of qualitative protein C abnormalities with defective interaction with protein S.

Comparison of two automated coagulometers and the manual tilt-tube method for the determination of prothrombin time.

Two automatic coagulometers--ACL 810 (Instrumentation Laboratory), a laser-nephelometric centrifugal analyzer, and KoaguLab 40 A (Ortho Diagnostics), an optical automatic coagulometer--were compared with the manual tilt-tube method for the performance of prothrombin time (PT). Seven ISI- (International Sensitivity Index) calibrated commercial thromboplastin reagents were used for duplicate determinations in 30 normal subjects, 30 patients with liver disease, and 30 patients receiving stabilized oral anticoagulation. Clotting times were longer with the manual method than with ACL 810 and, to a lesser extent, with KoaguLab 40 A. Average imprecision of duplicate determinations (CV) was less than 1% with ACL 810; KoaguLab 40 A and the manual method had similarly higher imprecisions (2.8% and 2.7%). Differences in origin and slope of the regression curves of clotting times obtained with the coagulometers over the tilt-tube method were observed with all the reagents tested. Transformation of clotting times to PT ratios did not eliminate the bias resulting from the different clot-detection methods. A higher percentage of patients with liver disease had abnormal PT ratios when their plasma was tested with the coagulometers than with the manual method. Transformation of PT ratios to International Normalized Ratios effectively eliminated the bias resulting from the different thromboplastin reagents but had no effect on the bias resulting from the different clot-detection methods. A significant proportion of patients appeared excessively anticoagulated (INR greater than 4.5) with the coagulometers but not with the manual method. These results highlight the need for standardization of both instrumentations and reagents to improve monitoring of oral anticoagulant treatment.

Asa yeyunal antiperistaltica de Rienhoff. A proposito de una observacion. / Rienhoff's antiperistaltic interposition. Apropos of an observation

Se presenta una observacion luego de reseccion esofago-gastrica por cancer, donde se utilizo yeyuno antiperistaltico en la reconstruccion. Se demostro en la evolucion el caracter antifisiologico del procedimiento de Rienhoff. La experimentacion es concluyente al afirmar que la interposicion de segmentos de intestino delgado en antiperistaltismo, se consituyen en obstaculo al transito digestivo. Pese a la posicion favorable de Goni Moreno, y a los casos exitosos ocasionales; la revision de Pories, el estudio de Orsoni y nuestra observacion hacen notar el caracter peligroso del procedimiento