Evaluation of the Hemochron 8000 Rx/Dx system for heparin management.

The Hemochron Rx/Dx uses an ACT and a heparin response tube to calculate the heparin dose to identify heparin sensitive/resistant patients. We evaluated the Rx/Dx system in 37 patients to determine if the ACT after the predicted heparin loading dose was adequate to initiate CPB. The mean heparin dose calculated by the Rx/Dx was 31,700 IU +/- 8,700 IU (370 IU/kg) with a mean post ACT of 463 +/- 124 sec. Our standard heparin dose (400 IU/kg) would have given an additional 2,800 IU over the Rx/Dx. Four patients (6.5%) were predicted to be heparin sensitive and all four achieved an ACT over 450 sec. Twenty-one patients (56.8%) were predicted to be resistant and yet failed to raise the ACT over 450 sec in 17 (81.0%). Twelve patients (32.4%) were predicted to have a normal heparin response, and four (33.3%) did not achieve an ACT over 450 sec. In all, 21 patients (56.8%) did not achieve an ACT greater than 450 sec. Each institution should evaluate their heparin loading dose and the resultant ACT. In this study, we found the number of times the Rx/Dx system did not raise the ACT over 450 sec too great to justify the additional expense.

Abomasal luminal pressure in cattle with abomasal volvulus or left displaced abomasum.

The abomasal luminal pressure was determined during surgery in 54 dairy cows with abomasal volvulus (AV) and another 50 dairy cows with left displaced abomasum. The luminal pressure was high in all cattle with AV and 49 (98%) cattle with left displaced abomasum. Luminal pressure was significantly higher in cattle with AV (median, 11.7 mm of Hg; range, 4.1 to 32.4 mm of Hg) than cattle with left displaced abomasum (median, 8.7 mm of Hg; range, 3.5 to 20.7 mm of Hg). Among cattle with AV, abomasal luminal pressure was significantly higher in cattle that died or were sold for slaughter following surgery (median, 20.6 mm of Hg; n = 8) than in cattle that were retained in the herd (median, 11.0 mm of Hg; n = 46). The luminal pressure was weakly correlated with the preoperative serum alkaline phosphatase activity but not correlated with duration of inappetence before surgery. Calculation of likelihood ratios and construction of a response operating characteristic curve for cattle with AV indicated that a cut-off value of 16 mm of Hg for luminal pressure optimized the distribution of cattle into productive and nonproductive groups. The sensitivity, specificity, positive predictive value, and negative predictive value of a luminal pressure < 16 mm of Hg in predicting a productive outcome were 0.83, 0.75, 0.95, and 0.43, respectively.