Masters Degrees (Anaesthesiology and Critical Care)

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Browsing Masters Degrees (Anaesthesiology and Critical Care) by Subject "Cardiac surgery"

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    The effect of high dose morphine compared to fentanyl infusion on serum levels of mast cell tryptase during cardiac surgery
    (Stellenbosch : Stellenbosch University, 2016-12) Barbieri, Mia; Levin, Andrew I.; Stellenbosch University. Faculty of Health Sciences. Dept. of Anaesthesiology and Critical Care.
    Background: Morphine directly activates cutaneous mast cells in a seemingly dose-dependent manner, resulting in the release of both histamine and tryptase into the bloodstream. Tryptase is almost exclusively stored in mast cells. Elevated serum tryptase concentrations serve as an indicator of mast cell activation and have become the most frequently used laboratory investigation in anaphylaxis. Following a clinical diagnostic dilemma our study was aimed at answering whether mast cell tryptase concentration remains useful in supporting the diagnosis of anaphylaxis even after administration of high dose morphine. Methods:We conducted a non-blinded, randomized controlled trial comparing the effects of fentanyl and high dose morphine, on serum mast cell tryptase concentrations. A power analysis was performed. Twenty adults undergoing cardiac surgery were randomly assigned to one of two opioid regimens. Both groups received a fentanyl bolus of 3 to 8 mcg/kg at induction. In the fentanyl group this was followed by a fentanyl infusion of 5 to 10 mcg/kg/hr until completion of surgery. Patients in the morphine group received morphine 1 mg/kg infused over thirty minutes. Baseline serum mast cell tryptase concentrations were determined directly prior to induction of anaesthesia and again 90 minutes after the start of the opioid infusion. The primary endpoint was statistical differences in tryptase concentrations between the morphine and fentanyl groups at the two time periods. Results: Ten patients of similar demographics were enrolled in each group. In the fentanyl group the second, 90-minute mast cell tryptase concentration was statistically significantly (10.1%) lower (p = 0.006) than baseline. Despite the 95% confidence interval of the difference between the means (-1.06 to -0.34 mcg/L) not including zero , this was not a clinically important difference. In the morphine group serum mast cell tryptase concentrations in the second (90 minute) sample were not statistically different from baseline values, the 95% confidence interval including zero. No between-group differences in tryptase concentration were detected. One patient in the morphine group exhibited a clinically significant 50,4% increase in tryptase concentrations, albeit from a high baseline of 11.9 mcg/L, which in this small study constitutes a prevalence of 10% (95% CI 1.8% to 40.4.) Conclusion: In this small pilot study, serum mast cell tryptase concentrations were unaffected by whether fentanyl or high dose morphine was administered. The null hypothesis, that there is no significant increase in serum mast cell concentrations after high dose morphine compared to fentanyl during cardiac anaesthesia and surgery, was therefore accepted. Larger studies are however needed to ensure a robust result, especially in the morphine group
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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.