Page 37 - ANZCP Gazette APRIL 2022

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Healthcare Rights3 and the New Zealand Code of Health and Disability Services Consumers’ Rights.4 The latter is very specific, and Right 7 details the right to informed consent, to refuse treatment and to use an advance direc- tive under common law. Treating without consent has ramifications under criminal and tort law, disciplinary liability by registered professional bodies and liability under the Code of Rights.
There is a single meta-analysis of 6 studies compar- ing outcomes of 564 JWs with 903 matched controls5 with the majority of reports of cardiac surgery in JW patients refusing blood transfusions being single-centre studies with relatively small patient numbers.6–12 In part, this is a reflection of the very small proportion of JWs in the population (USA: 0.6%, Canada and Australia/New Zealand: 0.3%, Britain: 0.2%).13 These studies reveal no accurate detail of the modifiable factors of the conduct of cardiopulmonary bypass (CPB), including blood flow and pressure, nadir haemoglobin (Hb), oxygen delivery (DO2) and blood conservation measures, that are known to influence patient outcome.
The Australian and New Zealand Collaborative Perfusion Registry (ANZCPR) established in 2007 is unique in that it acquires data electronically in 20-30 sec- ond epochs throughout CPB together with preoperative variables and postoperative outcomes and now contains more than 35,000 procedures from 9 contributing cen- tres.14 The ANZCPR has been used for benchmark and quality improvement initiatives including red cell reduc- tion in CPB and more recently to demonstrate how modifying CPB oxygen delivery is associated with a reduction in acute kidney injury (AKI).15,16 These initia- tives provide a unique opportunity for an evaluation of both the modifiable factors of CBP management and outcomes of patients refusing transfusion.
Given the challenges managing patients refusing blood products in cardiac surgery, it is plausible that modifiable factors of CPB could influence the incidence of AKI. The aim of this study was to compare the intra- operative management of the modifiable factors of CPB and the incidence of AKI in patients refusing blood transfusion compared with a matched cohort of patients accepting blood transfusion from a multicentre perfu- sion registry.
Methods
Nine cardiac surgical centres in Australia and New Zealand prospectively collected data using the ANZCPR as previously described.14 Institutional Ethics Review Board approval was obtained at each participating cen- tre, and this study was approved by the ANZCPR Steering Committee. The ANZCPR meets the Australian Commission on Safety and Quality in Health Care National Operating Principles for Australian Clinical
Quality Registries (https://www.safetyandquality.gov.au/ publications-and-resources/resource-library/frame- work-australian-clinical-quality-registries). Clinical data definitions were based on the Australian and New Zealand Society of Cardiothoracic Surgeons (ANZSCTS) registry.17 Complete ANZCPR variable definitions are available at www.anzcpr.org.
Cardiac centres in the ANZCPR collected data on 34,884 adult patients undergoing CPB between 1 January 2007 and 31 December 2018. Patients were excluded if they were missing data on the refusal of blood product transfusion (not collected at 1 site, n = 3,942), yielding an initial data source of 30,942 patients. Of the 140 patients recorded preoperatively as refusing transfusion, 15 accepted transfusion postoper- atively and 7 were missing preoperative Hb or transfu- sion data. The remaining 118 patients refusing transfusion were included in the study (Figure 1). A propensity-matched group of patients accepting trans- fusion was identified to compare differences in CPB interventions and outcomes (see the ‘Statistical analysis’ section). Preoperative Hb was included as a matching variable a priori.
The primary endpoint was AKI defined according to the serum creatinine criteria of the modified RIFLE (renal Risk, Injury, Failure, Loss of renal function and End-stage renal disease) classification. Specifically, AKI is reported as any AKI (creatinine greater than 150% baseline), AKI-Risk (creatinine between 150% and 200% baseline) or AKI-Injury or greater (creatinine greater than 200% baseline). Change in creatinine was measured from preoperative value to maximum postoperative value. Secondary endpoints included 4-hour postopera- tive blood loss, mechanical ventilation time, length of postoperative stay, use of intra-aortic balloon pump, return to the operating theatre, myocardial infarction, stroke, a new requirement for dialysis, new renal insuf- ficiency, combined morbidity and in-hospital mortality. Combined morbidity was defined as the incidence of postoperative ventilation > 48 hours, new renal insuffi- ciency, stroke or return to theatre. New renal insuffi- ciency was characterised according to the ANZSCTS registry definition as one of the following: increased serum creatinine to >0.2 mmol/L (>200 μmol/L) and a doubling or greater increase in creatinine over the base- line preoperative value and the patient did not require preoperative dialysis/haemofiltration or a new postop- erative requirement for dialysis/haemofiltration (when the patient did not require this preoperatively).
Preoperative demographics and intraoperative data
CPB interventions and postoperative outcomes were compared between the two patient groups. To control
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