Page 20 - ANZCP Gazette-August-Booklet

STRATEGIES OF RISK MITIGATION USED TO
PREVENT POTENTIAL ERRORS IN CARDIOPLEGIA
DELIVERY—A SINGLE UNIT EXPERIENCE
Hannah Lea CCP, FANZCP, Children’s Hospital at Westmead
Killian O’Shaughnessy CCP, FANZCP, Director of Perfusion, Children’s Hospital at Westmead
Historically, del Nido cardioplegia has been successfully used in paediatric surgery since its introduction in 1994. In the last few years, it has become an increasingly popular choice for use in the adult population, particularly for valvular and aortic procedures. Del Nido is an appealing option for these types of procedures as it is a long acting, single dose solution providing a bloodless field and myocardial quiescence for up to 90 minutes. However, as evident by the increasing number of submissions to the ANZCP Perfusion Incident Reporting System relating to cardioplegia delivery, this incorporation has not been without incident.
In early 2019, our Department began to introduce del Nido cardioplegia as an alternate method of myocardial protection. In the initial phase of del Nido implementation, not all of our surgeons were convinced of its benefits, and so we were required to offer two different cardioplegic strategies, dependent upon surgical preference. With the use of two different solutions requiring different cardioplegia module settings, calculated dosages, flow rates, temperatures and dosage intervals, comes the potential for human error. In an effort to mitigate these potential errors, our team decided to develop a series of measures to prevent errors from occurring within our department.
Our previous method of myocardial protection was based upon a blood mix cardioplegia. The induction dose was delivered at a set temperature of 32 °C at a rate of 110 mL/m2/min and with a ratio of 3:1 (blood: crystalloid). When electrical silence was achieved, the Heater-Cooler Unit (HCU) (LivaNova 3T, Munich, Germany) cardioplegia tank water temperature was reduced to 25 °C and the ratio of blood to crystalloid was reduced based on ECG activity and the systemic potassium (K+) concentration. Maintenance doses were administered every 20 minutes, at the same temperature and flow rate for two minutes. The ratio of blood to crystalloid was delivered at 4:1 and again reduced dependent upon the systemic K+ concentration or the presence of any breakthrough electrical activity.
Alternatively, del Nido cardioplegia is delivered at an inverse ratio of four parts crystalloid cardioplegia solution to one part blood. The cardioplegia HCU tank is set at 2 °C, in order to achieve a cardioplegia perfusate temperature of less than 10 °C. A dose of 20 mL/kg is delivered at a rate of 7–10 mL/ kg/min, with the timing and volume of subsequent doses determined by the anticipated ischaemic time remaining.
Our current heart-lung machine configuration (LivaNova S5, Munich, Germany) has the cardioplegia blood pump mounted adjacent to the arterial outlet of the oxygenator in an effort to reduce the circuit prime volume. The cardioplegia crystalloid
pump is positioned remotely from the blood pump, as it has no influence on the amount of haemodilution. This presented a challenge when converting to del Nido cardioplegia, as it is not possible to invert the ratio of blood to crystalloid via settings in the cardioplegia control module, and we were unable to simply swap the blood and crystalloid pump boots as is possible if using a dual-roller pump. This required us to enter the cardioplegia control module settings for each case and change which pump was the master, and which was the follower in order to be able to set and achieve a blood to crystalloid ratio of 4:1 for the blood mix cardioplegia or 1:4 when using del Nido. For the blood mix cardioplegia, the blood pump would be the master pump (2a in our configuration) and the crystalloid pump (2b) would be the follower. For del Nido cardioplegia, the crystalloid pump (2b) would be the master and the blood pump (2a) would be the follower.
Consequently, having to adjust the assignment of the cardioplegia pumps in the cardioplegia control module on a case by case basis, depending upon the type of solution being used, introduces the potential for human error – and this risk would be amplified in the event of emergent bypass initiation. The incorrect assignment of the cardioplegia pumps for the type of cardioplegia solution being used could result in the del Nido cardioplegia solution being mixed at the wrong ratio and volume of blood resulting in cardioplegia being delivered to the patient that is too weak and unable to induce cardiac arrest. Conversely, if the pump setting is configured for del Nido and the traditional cardioplegia solution with a potassium concentration of 80 mmol/L was used, this would result in a profoundly hyperkalaemic solution being administered to the coronary arteries.
In an effort to mitigate the risks associated with the two different cardioplegia strategies, we implemented a two- person checklist procedure to be completed before the initiation of cardiopulmonary bypass. This is comprised of two discrete checklists in our electronic charting system – one for the blood mix cardioplegia and the other for del Nido – that is completed depending upon which strategy was being used for the particular operation. This comprehensive checklist serves to ensure that the pump and control module settings are correct for the type cardioplegia being used. As seen in Figure 1, this checklist includes the type of cardioplegia solution, dose volume, temperature, set ratio as well as confirming the correct calibration of the pump for the pump boot size.
17 SEPTEMBER 2020 | www.anzcp.org