Page 38 - ANZCP Gazette November 2021

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Perfusion 35(8)
use of coated circuits.9 The other reason for routine addition of albumin is to maintain plasma oncotic pres- sure. The literature seems divided on the benefits of albumin in perfusion primes to maintain oncotic pres- sure. Some references extol the virtues of albumin to maintain oncotic pressure1,3,10 and reduce third spacing, while others conclude that albumin, in the dosages listed, does not provide any benefit.11 It would be inter- esting to formally study the effects of adding albumin, with various dosing regimens, on plasma oncotic pres- sure, inflammatory response and resultant patient out- comes, in this contemporary era of coated bypass circuits and minimised prime volumes.
In total, 28 units (44%) perfusing 8,965 cases per year elect to add sodium bicarbonate, primarily to buffer their balanced physiological solutions. Traditionally, NaHCO3 was added to crystalloid primes to prevent the inevitable metabolic acidosis caused on CPB.1,3,12 This was in the era of large prime volumes resulting in mas- sive acute hemodilution and synthetic colloid additives. As noted, metabolic acidosis has not been shown at the end of bypass with either Plasma-Lyte or Hartmann’s solution in the modern context.8
Mannitol is reported to be beneficial for maintain- ing osmotic pressure, renal function and fluid bal- ance.1,6 A total of 19 (30%) units add mannitol with the intent to achieve this benefit and more. Published evi- dence remains unable to support these notions.13–16 Furthermore, what is the impact of mannitol in our era of low primes and restricted prebypass fluid manage- ment? Hyllen17 are studying the effects of mannitol in HLM prime on patient electrolyte levels and osmolal- ity. This study is due for completion later this year and may provide guidance on the effects of mannitol in modern perfusion primes.
There is no remarkable difference in either priming solutions or prime additives and dosing regimens between Australia’s private and public open-heart units.
Complete participation from all 63 Australian adult open-heart centres was the strength of this survey. Our results accurately reflect contemporary priming con- stituents in Australia. The main factors leading to com- plete participation were that it was easy to complete and there were only 15 questions mostly multiple choice that took only 10minutes to complete. There was genuine interest in priming constituents from the Australian perfusion community, as evident from respondents’ comments at the end of the survey. This interest arises from the literature giving little guidance on priming constituents and dosages. Units were keen to see if their practice was within the range of common practice. Confidentiality was also a strength of this study and this encouraged units to answer honestly.
Another strength of this survey was that the perfu- sionists were the personnel completing the survey rather
than other members of the surgical team or manage- ment staff.
The limitations of this survey were that these results reflected the priming constituents for that snapshot in time. Three units noted that they were considering or in the process of moving from a Hartmann’s to a Plasma-Lyte prime. This survey also had the limita- tion of one response per unit; while this feature made the survey easy for full participation it was not able to capture the variation of practice of the 13 units that did not have an institutional priming procedure, and rather each perfusionist used their preferred priming recipe. These respondents were asked to answer on the most commonly used priming technique.
The results of this survey will be informative to Australian perfusionists to know where their practice lies in the scope of the entire Australian practice of priming. Australian perfusionists were well versed in the rationale for each component of their prime solution even though they admitted some of these practices were historical. This survey may fuel investigation to validate the reasons why or perhaps why not to add particular ingredients. This renewed investigation is timely in this era of minimised prime volumes, balanced physiologi- cal solutions and coated circuits. Further investigation will ensure that our priming practices are not a remnant of the past, based on literature from our perfusion pio- neers, but complement our contemporary perfusion strategies and patient-focused approach.
Conclusion
Priming solutions are an essential part of the complex procedure of open-heart surgery. They are used to prime the bypass circuit and mix rapidly with patient’s systemic blood volume at the initiation of CPB. Consequently, the selection of the best priming solution and its ingredients is an important decision.
This survey highlighted that adult Australian prim- ing solutions have many aspects of conformity. They use balanced physiological solutions, not synthetic colloids, and most centres then add various combinations of albumin, sodium bicarbonate and mannitol to these base solutions. However, up to 30% of cases have hepa- rin as the only addition to the base solution. The ration- ale provided for the addition of each constituent provides evidence of the historical or routine nature of many units’ priming solutions, while some units provide a more patient-centred perfusion prime, adding con- stituents when indicted by patient or surgical factors.
Insufficient literature on the constituents of priming solutions has been published to guide perfusionists on their choice of priming recipes in this contemporary era of minimised prime volumes, widespread use of bal-
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