Masters Degrees (Anaesthesiology and Critical Care)

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Browsing Masters Degrees (Anaesthesiology and Critical Care) by browse.metadata.advisor "Buys, Willem Frederik"

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    Residual heparin concentrations in salvaged blood from the Sorin Xtra® autotransfusion system during cardiac surgery
    (Stellenbosch : Stellenbosch University, 2016-12) Buys, Mathilde; Levin, Andre Ian; Buys, Willem Frederik; Stellenbosch University. Faculty of Health Sciences. Dept. of Anaesthesiology and Critical Care.
    Introduction: Cell salvaging is a fundamental component of blood conservation during cardiac surgery. It entails intra-operative scavenging, washing and collection of a patient’s blood for retransfusion at completion of surgery. During surgery vast amounts of heparin is administered to avoid fatal thrombosis in both the bypass and autotransfusion circuits. Adequate heparin removal during the cell salvaging process is thus crucial to avoid retransfusion of heparin to these high risk patients. We wanted to measure heparin levels in the collected reinfusate prior to retransfusion, in order to quantify heparin removal in our current autotransfusion system, the Sorin Xtra®. Method This study was subjected to ethical committee approval prior to initiation (S14/03/050). 31 adult patients undergoing on pump cardiac surgery in Tygerberg Academic Hospital were recruited after taking informed consent. A standard cell salvaging process was used for setup using the Sorin Xtra® autotransfusion system. After completion of the cell salvaging process, a blood sample was aspirated from the collected reinfusate and stored in a standard citrated blood sampling tube. Sample processing and heparin measurement were performed in the haematology laboratory of Tygerberg Hospital. A modified anti-Xa heparin assay was employed to measure reinfusate heparin levels, since the absence of coagulation factors necessitates the addition of a set amount of normal pooled plasma prior to performing the assay. Results The mean heparin levels measured in the Sorin Xtra® reinfusate were 0.52 (IQR 0.16 – 0.74; 95% CI 0.30 – 0.66) IU/ml. The 95% confidence intervals did not encroach on the alternative hypothesis, but did span the value representing the null hypothesis. The data thus failed to reject the null hypothesis, indicating clinically significant reinfusate heparin levels. Sixteen of 31 reinfusates (56%; 95% confidence interval 35 to 68%) exhibited heparin concentrations exceeding 0.5 IU/ml. There was no clinically significant relationship (r2 0.02, p = 0.46) between heparin dosage administered to the patient and the concentration measured in the reinfusate. Conclusion Clinically significant heparin levels in cell saving reinfusate can potentially worsen postoperative bleeding in cardiac surgery. The mean heparin level measured in our study was more than the AABB’s recommended value of 0.5IU/ml, and 16 samples had absolute values more than this. Although the absolute heparin dose retransfused remain debatably low, the possibility of heparin induced coagulopathy should be entertained in cardiac patients that received reinfusate from the Sorin Xtra® ATS with ongoing postoperative bleeding in our institution. A practical suggestion in these cases would be to quantify heparin activity either with a point of care device (TEG/ROTEM) or direct measurement of heparin concentration using an Anti-Xa assay and titrating heparin reversal accordingly.