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Supplemental material, 924919_online_appendix for Acute kidney injury, stroke and death after cardiopulmonary bypass surgery: the role of perfusion flow and pressure by Laura Turner, Ashutosh Hardikar, Matthew D Jose, Keshav Bhattarai, Carmel Fenton, Rajiv Sharma, Geoff Kirkland, Lisa Jeffs, Monique Breslin, Bruna Silva Ragaini and Richard F Newland in Perfusion

Low indexed oxygen delivery (DO2i) during cardiopulmonary bypass (CPB) has been associated with an increase in the likelihood of acute kidney injury (AKI), with critical thresholds for oxygen delivery reported to be 260–270 mL/min/m2. This study aims to explore whether a relationship exists for oxygen delivery during CPB, in which the integral of amount and time below a critical threshold, is associated with the incidence of postoperative AKI. The area under the curve (AUC) with DO2i during CPB above or below 270 mL/min/m2 was calculated as a metric of oxygen delivery in 210 patients undergoing CPB. To determine the influence of low oxygen delivery on AKI, a multivariate logistic regression model was developed including AUC < 0, Euroscore II to provide preoperative risk factor adjustment, and incidence of red blood cell transfusion to adjust for the influence of transfusion. Having an AUC < 0 for an oxygen delivery threshold of 270 mL/min/m2 during CPB was an independent predictor of AKI, after adjustment for Euroscore II and transfusion [OR 2.74, CI {1.01–7.41}, p = .047]. These results support that a relationship exists for oxygen delivery during CPB, in which the integral of amount and time below a critical threshold is associated with the incidence of postoperative AKI.

Air bubble detectors (ABDs) are utilized during cardiopulmonary bypass (CPB) to protect against massive air embolism. Stockert (Munich, Germany) ABD quantify microbubbles >300 μm; however, their reliability has not been reported. The aim of this study was to assess the reliability of the microbubble data from the ABD with the SIII and S5 heart–lung machines. Microbubble counts from the ABD with the SIII (SIII ABD) and S5 (S5 ABD) were measured simultaneously with the emboli detection and classification (EDAC) quantifier in 12 CPB procedures using two EDAC detectors and two ABDs in series in the arterial line. Reliability was assessed by the Spearman correlation co-efficient (r) between measurements for each detector type, and between each ABD and EDAC detector for counts >300 μm. No correlation was found between the SIII ABD (r = .008, p = .793). A weak negative correlation was found with the S5 ABD (r = −.16, p < .001). A strong correlation was found between the EDAC detectors (SIII; r = .958, p < .001), (S5; r = .908, p < .001). With counts >300 μm, the SIII ABDs showed a correlation of small–medium effect size between EDAC detectors and ABD1 (r = .286, p < .001 [EDAC1], r = .347, p < .001 [EDAC2]). There was no correlation found between ABD2 and either EDAC detector (r = .003, p = .925 (EDAC1), r = .003, p = .929 [EDAC2]). A correlation between EDAC and the S5 ABD, was not able to be determined due to the low bubble count detected by the EDAC >300 μm. Both SIII ABD and S5 ABD were found to be unreliable for quantification of microbubble activity during CPB in comparison with the EDAC. These results highlight the importance of ensuring that data included in the CPB report is accurate and clinically relevant, and suggests that microbubble counts from devices such as the SIII ABD and S5 ABD should not be reported.

The delivery of gaseous microemboli (GME) by the cardiopulmonary bypass circuit should be minimized whenever possible. Innovations in components, such as the integration of arterial line filter (ALF) and ALFs with reduced priming volumes, have provided clinicians with circuit design options. However, before adopting these components clinically, their GME handling ability should be assessed. This study aims to compare the GME handling ability of different oxygenator/ALF combinations with our currently utilized combination. Five commercially available oxygenator/ALF combinations were evaluated in vitro: Terumo Capiox SX25RX and Dideco D734 (SX/ D734),Terumo Capiox RX25R and AF125 (RX/AF125),Terumo FX25R (FX), Sorin Synthesis with 102 μm reservoir filter (SYN102), and Sorin Synthesis with 40 μm reservoir filter (SYN40). GME handling was studied by introducing air into the venous return at 100 mL/min for 60 seconds under two flow/ pressure combinations : 3.5 L/min, 150 mmHg and 5 L/min, 200 mmHg. Emboli were measured at three positions in the circuit using the Emboli Detection and Classification (EDAC®) Quantifier and analyzed with the General Linear Model. All circuits significantly reduced GME. The SX/D734 and SYN40 circuits were most efficient in GME removal whilst the SYN102 handled embolic load (count and volume) least efficiently (p < .001). A greater number of emboli

The use of surface modified, biocompatible tubing in cardiopulmonary bypass has been reported to decrease the inflammatory responses caused by blood contact with the non endothelial surface of poly vinyl chloride (PVC) tubing. The combination of advances in biocompatible tubing and increased affordability resulted in a change to our cardiopulmonary bypass circuit, with the Terumo Capiox® SX25 oxygenator and Cobe PVC tubing being replaced with a Terumo Capiox® SX25RX (with X coating) and Cobe SMARxT® tubing. Prior to the introduction of the coated oxygenator, no connection problems had been evident. One unrelated disconnection involving coated tubing was reported in June 2005 to the Australian and New Zealand College of Perfusionists Perfusion Incident Reporting System. At this time we revised all of our set up protocols and the recommended actions from manufacturers. We further report three separate incidents of pump boot disconnection from the venous reservoir outlet of the oxygenator during bypass (that occurred within a 13-month period), and an outline of immediate and prospective evaluation of the probable cause. We propose that SMARxT® 3/8″ × 3/32″ tubing should not be used on the venous outlet connector of Terumo Capiox® SX25RX oxygenators. It appears as though the design of the outlet combined with the properties of SMARxT® tubing may contribute to the disconnection.

Oxygenator arterial outlet blood temperature is routinely measured in the cardiopulmonary bypass (CPB) circuit as a surrogate for the temperature of the arterial blood delivered to sensitive organs such as the brain. The aim of this study was to evaluate the accuracy of the temperature thermistors used in the Terumo Capiox SX25 oxygenator and to compare the temperature measured at the outlet of the oxygenator using the Capiox CX*TL Luer Thermistor with temperatures measured at distal sites. Five experimental stages were performed in vitro to achieve this aim. Under our experimental conditions, the luer thermistors accurately measured the temperature as referenced by a precision thermometer. In the CPB circuit, the difference between arterial outlet and reference thermometer temperature varied with outlet temperature over-reading at low temperatures and under reading at high temperatures. There was negligible heat loss (-0.4+/-0.1degrees C) measured at 4.5 m from the arterial outlet. The Terumo Capiox CX*TL Luer Thermistor is an accurate and reliable instrument for measuring temperature when incorporated into the Capiox Oxygenator. The accuracy in the measurement of temperature using these thermistors is affected by the thermistor immersion depth. Under reading of the arterial blood temperature by approximately 0.5 degrees C should be considered at normothermic temperatures, to avoid exceeding the maximum arterial blood temperature as described by institutional protocols. The accuracy of blood temperature measurements should be considered for all oxygenator arterial outlet temperature probes.

The delivery of gaseous microemboli (GME) by the cardiopulmonary bypass circuit should be minimized whenever possible. Innovations in components, such as the integration of arterial line filter (ALF) and ALFs with reduced priming volumes, have provided clinicians with circuit design options. However, before adopting these components clinically, their GME handling ability should be assessed. This study aims to compare the GME handling ability of different oxygenator/ALF combinations with our currently utilized combination. Five commercially available oxygenator/ALF combinations were evaluated in vitro: Terumo Capiox SX25RX and Dideco D734 (SX/ D734), Terumo Capiox RX25R and AF125 (RX/AF125), Terumo FX25R (FX), Sorin Synthesis with 102 μm reservoir filter (SYN102), and Sorin Synthesis with 40 μm reservoir filter (SYN40). GME handling was studied by introducing air into the venous return at 100 mL/min for 60 seconds under two flow/ pressure combinations: 3.5 L/min, 150 mmHg and 5 L/min, 200 mmHg. Emboli were measured at three positions in the circuit using the Emboli Detection and Classification (EDAC ®) Quantifier and analyzed with the General Linear Model. All circuits significantly reduced GME. The SX/D734 and SYN40 circuits were most efficient in GME removal whilst the SYN102 handled embolic load (count and volume) least efficiently (p