Effect of Pump Prime on Acidosis, Strong-ion-difference and Unmeasured Ions during Cardiopulmonary Bypass

Abstract

Changes in acid-base balance, particularly metabolic acidosis, are common in cardiac surgery with cardiopulmonary bypass (CPB) 1,2 . The mechanisms for such metabolic acidosis however, remain controversial. Those who use bicarbonate centred approaches to acid-base (patho)physiology conclude that dilution of bicarbonate is the underlying mechanism for acid-base changes following large volume infusion during CPB 3,4 . Using the Stewart approach to acid-base physiology 5 and fluid therapy 6 , our group 1,7 , and Himpe et al 8 and Morgan et al 9 , concluded that bypass associated metabolic acidosis may instead depend on the electrolytes and colloids in the CPB prime. One limitation of these studies was that CPB primes included constituents that are not measured in routine clinical chemistry; either colloids such as gelatin 1,8 or smaller organic molecules such as gluconate and acetate 7,9 . This limited the quantitative acid-base balance analysis possible with the Stewart approach 10 , because of the relatively large effects of unmeasured ions from the CPB prime solutions. Further, there is limited data on the changes in acid-base variables during the first 30 minutes of CPB 7-9 .The underlying mechanisms of acid-base changes associated with CPB might be easier to quantify using CPB primes that contain only electrolytes and anions routinely measured in clinical chemistry. We hypothesised that a CPB prime with lactate and chloride would be associated with less metabolic acidosis than a prime with only chloride, because of a difference in the measured strong-ion-difference. To test this hypothesis, we conducted a randomised, double-blinded trial of two different CPB primes: one containing 152 mmol/l of chloride and another SUMMARyWe tested the hypothesis that a cardiopulmonary bypass prime with lactate would be associated with less acidosis than a prime with only chloride anions because of differences in the measured strong-ion-difference. We randomised 20 patients to a 1500 ml bypass prime with either a chloride-only solution (Ringer's Injection; anions: chloride 152 mmol/l) or a lactated solution (Hartmann's solution; anions: chloride 109 mmol/l, lactate 29 mmol/l). Arterial blood was sampled before bypass and then two, five, 15 and 30 minutes after initiating bypass. We used repeated measures analysis of variance to compare groups. In both groups, the base-excess and measured strong-iondifference decreased markedly from baseline after two minutes of bypass. The chloride-only group had greater acidosis with lower base-excess and pH (P <0.05), greatest after five minutes of bypass (C5). Contrary to our hypothesis, however, the difference between the groups was not due to a difference in the measured strong-iondifference, P=0.88. At C5 when the difference in standard base-excess between the groups was greatest, 1.9 mmol/l (95% confidence interval: 0.1 to 3.6 mmol/l, P <0.05), the difference in the measured strong-ion-difference was only 0.2 mmol/l (95% confidence interval: -2.4 to 2.7 mmol/l, P >0.05). There was, how...

Plasma acetate, gluconate and interleukin-6 profiles during and after cardiopulmonary bypass: a comparison of Plasma-Lyte 148 with a bicarbonate-balanced solution

“…A potential complication [2] of CPB is metabolic acidosis, which is influenced by the CPB circuit priming fluid [3,4]. Attempts to prevent metabolic acidosis have entailed alterations to circuit prime fluids, including partial replacement of chloride by rapidly metabolised anions such as L-lactate [5,6], acetate and gluconate [3,7], or else by bicarbonate [8]. Plasma-Lyte 148 (Baxter, Toongabbie, NSW, Australia) is a crystalloid CPB prime fluid in common use in Australia and New Zealand (personal communication, Andrew McLaren, Baxter, Australia) in about 7% of surveyed units in the UK [9] and in some units in North America [10].…”

Complications in immediate postoperative recovery from elective cardiac surgery: a cross-sectional study based on Roy’s theory

“…Em relação aos casos equilíbrio de ácido-base identificados, defende-se que tais resultados tenham associação direta com a seleção de participantes desta pesquisa. Todos os participantes foram submetidos à circulação extracorpórea e a sua utilização é reconhecida pela literatura como percursora de distúrbios de alcalose respiratória e acidose metabólica (Liskaser et al, 2009). Assim, evidencia-se uma continuidade das es-tratégias de coping e da resposta ineficaz iniciada durante o período intraoperatório, gerada principalmente pela deficiência da oxigenação dos tecidos e pelo stresse sofrido pelo organismo durante o procedimento cirúrgico.…”

“…Assim, evidencia-se uma continuidade das es-tratégias de coping e da resposta ineficaz iniciada durante o período intraoperatório, gerada principalmente pela deficiência da oxigenação dos tecidos e pelo stresse sofrido pelo organismo durante o procedimento cirúrgico. A circulação extracorpórea provoca uma redução da oxigenação dos tecidos pela libertação de catecolaminas e compostos vasopressores procedentes do contacto das células sanguíneas com a superfície não-endotelial do circuito da CEC, provocando alterações de ácido-base como principais complicações do pós-operatório de cirurgia cardíaca com uso de CEC (Liskaser et al, 2009). A identificação do sangramento excessivo como a terceira maior complicação do pós-operatório imediato corrobora para a asserção de que o sangramento continua a ser uma das principais morbidades em cirurgia cardíaca, especialmente com a utilização de procedimentos mais complexos que favorecem o prolongamento de períodos de circulação extracorpórea (Liskaser et al, 2009).…”

“…A circulação extracorpórea provoca uma redução da oxigenação dos tecidos pela libertação de catecolaminas e compostos vasopressores procedentes do contacto das células sanguíneas com a superfície não-endotelial do circuito da CEC, provocando alterações de ácido-base como principais complicações do pós-operatório de cirurgia cardíaca com uso de CEC (Liskaser et al, 2009). A identificação do sangramento excessivo como a terceira maior complicação do pós-operatório imediato corrobora para a asserção de que o sangramento continua a ser uma das principais morbidades em cirurgia cardíaca, especialmente com a utilização de procedimentos mais complexos que favorecem o prolongamento de períodos de circulação extracorpórea (Liskaser et al, 2009). Este resultado aponta o sangramento no pós-operatório como uma das complicações mais comuns da cirurgia cardíaca, sendo de aproximadamente 20% os pacientes que apresentam sangramento de forma significativa após cirurgia e 5% precisam de reexploração cirúrgica devido ao sangramento excessivo (Fröjd & Jeppson, 2016).…”

The use of mannitol in cardiopulmonary bypass prime solution—Prospective randomized double‐blind clinical trial

“…Maintenance of the acid‐base homeostasis and normal electrolyte levels is of great importance during CPB . A CPB circuit prime influences several organ systems, such as the central nervous system and the renal system, as well as coagulation, osmolality, and electrolyte levels, all this can impact the outcome after cardiac surgery . However, the choice of CPB prime is usually based on personal preferences and historical beliefs .…”