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Year : 2022  |  Volume : 11  |  Issue : 2  |  Page : 49-53

Comparative study to assess the effect of priming solutions (Plasmalyte-A and Ringer Lactate) on Acid–base balance during cardiopulmonary bypass for adult cardiac surgery

1 Department of CTVS, AIIMS, Rishikesh, Uttarakhand, India
2 Department of Cardiac Anaesthesia, AIIMS, Rishikesh, Uttarakhand, India

Date of Submission14-Dec-2021
Date of Decision19-Jan-2022
Date of Acceptance08-Mar-2022
Date of Web Publication27-Jul-2022

Correspondence Address:
Dr. Anshuman Darbari
Department of CTVS, AIIMS, Rishikesh - 249 203, Uttarakhand
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/rcm.rcm_65_21

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Background: Priming solution used in cardiopulmonary bypass has different impact on body, primarily on the metabolic acidosis and electrolytes. This observational comparative study was done to find the metabolic effects of Ringer lactate and Plasmalyte-A as priming solutions for various metabolic parameters during adult cardiac surgery. Materials and Methods: In the present study, 52 subjects were included who received different priming solutions. Subjects were categorized into two groups. Group P received Plasmalyte-A as prime and Group R received Ringer lactate. From all these cases, samples were collected at predefined time durations, and results were compared between both groups. Observation and Results: A total of 52 patients were evaluated for the metabolic changes concerning different priming solutions. Group P included the subject who received Plasmalyte-A as pump prime (n = 26), and Ringer lactate was used as pump prime in Group R (n = 26). We compared various parameters such as pH: In Group R, a decrease in pH was statistically significant with P < 0.05 at 40 min of bypass (T40) and P < 0.05 at 6 h of postbypass (T6). Base Excess: The mean value in Group P was − 1.72 ± 2.18 and − 3.16 ± 2.48 and in Group R at 30 min of bypass (T30). A statistically significance was found between the two groups for this parameter (P < 0.05). Lactate and Strong Ions Difference: A statistically significant data were found between the two groups for this parameter throughout the bypass as well as postoperative hours with the P < 0.05. Conclusion: Plasmalyte-A is more favorable crystalloid solution as a pump prime fluid as it helped to maintain satisfactory metabolic parameters with less metabolic acidosis during adult cardiac surgeries.

Keywords: Cardiac surgery, cardiopulmonary bypass, heart–lung machine, metabolic acidosis, priming solution

How to cite this article:
Vashisth A, Saleem Y, Darbari A, Gupta A, Lahiri R, Kumar A. Comparative study to assess the effect of priming solutions (Plasmalyte-A and Ringer Lactate) on Acid–base balance during cardiopulmonary bypass for adult cardiac surgery. Res Cardiovasc Med 2022;11:49-53

How to cite this URL:
Vashisth A, Saleem Y, Darbari A, Gupta A, Lahiri R, Kumar A. Comparative study to assess the effect of priming solutions (Plasmalyte-A and Ringer Lactate) on Acid–base balance during cardiopulmonary bypass for adult cardiac surgery. Res Cardiovasc Med [serial online] 2022 [cited 2022 Dec 9];11:49-53. Available from: https://www.rcvmonline.com/text.asp?2022/11/2/49/352499

  Introduction Top

Cardiopulmonary bypass (CPB) procedure for cardiac surgery is defined as the extracorporeal circulation technique in which the function of the heart and lungs is temporarily taken over by a heart–lung machine and membrane oxygenator. The main purpose of the CPB is to provide adequate perfusion and nutrition to the vital organs of the body.[1] The CPB circuit must be primed with a fluid solution so that adequate flow rates can be rapidly achieved on initiation of CPB without risk of air embolism to the patient. The heart–lung machine circuit is primed with widely used crystalloids solutions and necessary drugs as per need, i.e., anticoagulants such as heparin, bicarbonate, albumin, and mannitol.[2],[3]

Metabolic acidosis is a common problem after cardiac surgery, the cause of which is multifactorial. The CPB prime solution has been described as one among the reasons.[4],[5] Ringer lactate is a commonly used priming solution, and studies have been done regarding it's possible role in metabolic acidosis. Another intravenous fluid Plasmalyte-A, having chemical composition and properties resembling to plasma fluid, has also been used as a safe priming solution to avoid any postoperative complication.[6] The electrolyte composition of these two solutions is compiled in [Table 1].
Table 1: The electrolyte composition of two solutions[7]

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It is well established that the contractility of cardiac muscle and excitation-contraction coupling pathway is adversely affected by acidosis. Various effects of acidosis on calcium ion (Ca2+) delivery are such as (1) Ca2 + current inhibition, (2) Ca2 + release from the sarcoplasmic reticulum decrease, and (3) shortening of the action potential.[8],[9]

  Materials and Methods Top

Before starting, the concept was presented to the institutional scientific board for this study approval and registration was done. After approval from the Research Ethics Committee approval (AIIMS, Rishikesh) (IEC approval no.-AIIMS/IEC/21/220, dated-09.04.2021), this study was started. All patients were properly explained and gave the written informed consent before inclusion in this study. A prospective, double-blind, randomized trial study was conducted on 52 adult patients (18–70 years).

In this study, inclusion criteria included adult patients undergoing elective cardiac surgeries both valvular and coronary bypass, and exclusion criteria included emergency surgery, redo surgery, diabetes mellitus, renal failure (serum creatinine >1.5 mg%), liver dysfunction (total bilirubin >2.5 mg %), left ventricular dysfunction (ejection fraction <35%), and cyanotic heart disease.

A prospective, double-blind, randomized trial in 52 adult patients undergoing elective cardiac surgery with CPB was conducted to study the acid–base effect of these two different priming fluids. Taking the mean and standard deviation from this reference, the required sample size for each group was calculated to be 26. Thus, the total sample size was brought to be 52 and was divided into two groups. Group P offered Plasmalyte-A as a pump prime and Group R participant offered Ringer lactate as a pump prime.[7]

A priming volume of 1100–1500 ml. as per standard requirement was used for de-airing the pump circuit with additives such as heparin, mannitol, and bicarbonate as per protocol. Intravenous fluid, pump prime, and cardioplegia, all the solutions were used as per study protocol in both groups. During CPB, alpha-state strategy was used to correct acid–base balance, and sodium bicarbonate was added as per body weight and base excess.

Aim and objective

This study is planned to see if, changing the prime composition between Ringer lactate and Plasmalyte-A can make any difference in certain parameters and possible postoperative outcomes after adult cardiac surgery.

Blood sample time points and measurements of variables

The arterial blood samples were taken at different time intervals that were before initiation of bypass (TPB), during bypass at 10 min (T 10), 20 min (T 20), 30 min (T 30), 40 min (T 40), and 60 min (T 60), and in postbypass at 6 h (T 6) and 12 h (T 12). An arterial sample of 0.5 ml was taken from the CPB circuit and sent to the ABL800 analyzer for arterial blood gases and electrolytes. Serum sodium, potassium, lactate, chloride, bicarbonate, and base excess were measured at all time points. Arterial blood gases were also measured (pH, partial pressure of carbon dioxide, oxygen, and oxygen saturation). A whole blood sample (approximately 03 ml) was taken from the patient at prebypass (TPB) and postbypass at 6 h (T 6) and 12 h (T 12) for blood urea and serum creatinine. Strong ions difference (SID) was calculated in mEq/L with the formula:[10] (Na+ + K+) − (Cl− + lactate).

Statistical analysis

The collected data were transformed into variables, coded, and entered into Microsoft Excel. Data were analyzed and statistically evaluated using the statistical package for the social sciences (SPSS) software developed by IBM, USA, Version- 25. All variables studied were quantitative, and ANOVA was used to compare the variable values at different time intervals between two groups. P < 0.05 will be considered statistically significant.

  Results Top

This study involved two groups comparing priming solutions used for adult cardiac surgery on CPB. Demographic and relevant data about these 52 patients were studied. The two groups were no different in terms of age, body surface area, flow, bypass time, and cross-clamp time. There was no mortality, significant morbidity, and postoperative use of inotropes was minimal in both groups.

Effects of pump prime

Our main finding was that, after priming with a Ringer lactate, pH fell more during the whole bypass compared with Plasmalyte-A during various perioperative and postoperative time points. In the Group R, patients showed more severe metabolic acidosis and significant difference at 40 min after initiating CPB (P = 0.03 at T4) and T6 h postbypass (P = 0.02). In this group, pH was decreased from 7.42 ± 0.05 at prebypass to 7.39 ± 0.05 at T40 during bypass and 7.35 ± 0.05 at T6 h (postbypass). Data are shown in [Figure 1]. In the Group P, the mean pH was almost similar to baseline value during bypass, with the postbypass pH nonsignificant fall.
Figure 1: Comparison of mean pH between both groups

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Significant pH fall in the Group R may be due to base excess, decreased bicarbonate, and increased lactate level. The mean bicarbonates decreased in this group during the whole CPB but at T40 fell more from 21.75 ± 2.54 mEq/L at prebypass to 20.68 ± 5.25, mEq/L. This is shown in [Figure 2].
Figure 2: Comparison of mean bicarbonate between both groups

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The mean base excess values decreased from 2.33 ± 2.93 mEq/L at prebypass to − 2.98 ± 1.19 mEq/L at T40 and − 3.16 ± 2.48 mEq/L at T60, in the Group R with the P = 0.23 and 0.03, respectively, as compared to Group P. The mean bicarbonate (HCo3) and base excess in the Group P were almost similar to baseline. This is shown in [Figure 3].
Figure 3: Comparison of mean base excess between both groups

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Both groups had marked mean lactate levels rise from baseline during bypass and postbypass. In the Group R, the mean lactate level rose from 0.80 ± 0.21 at prebypass to 3.04 ± 0.82 at T10, 3.06 ± 1.07 at T20, and 3.21 ± 0.90 at T30 with P < 0.05 as compared with Group P. This is shown in [Figure 4]. While in Group P, increase in mean blood lactate level was observed 0.92 ± 0.36 mmol/L at prebypass to on bypass at T10, T20, T30, T40, and T60 and postoperative (T6, T12) 2.06 ± 0.63 mmol/L, 2.32 ± 0.79 mmol/L, 2.48 ± 1.02 mmol/L, and 2.55 ± 1.00 mmol/L, 2.77 ± 0.85 mmol/L, 2.32 ± 0.85 mmol/L, 1.98 ± 0.74 mmol/respectively.
Figure 4: Comparison of mean lactate between both groups

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The mean SID decreased during the CPB and postoperative periods in the Group R from 31.96 ± 2.88 at prebypass to 30.10 ± 2.47 mEq/L, 30.09 ± 3.99 mEq/L, and 30.33 ± 3.80 mEq/L (P < 0.05) at T10, T20, and T30, respectively, implying metabolic acidosis as depicted in [Figure 5]. In the Group R, the SID was decreased due to hyperchloremia and hyperlactatemia, so SID becomes one of the possible reasons for the decrease in pH compared to the Group R compared to where Plasmalyte-A is used priming solution.
Figure 5: Comparison of mean strong ions difference between both groups

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We have also evaluated the effect of these priming solutions on renal function at 6 and 12 h of postbypass. In the Group P, the mean serum creatinine level was reduced from 0.75 ± 0.18 at prebypass to 0.54 ± 0.27 at 6 h after postbypass with P < 0.01 compared with Group R. However, in both groups, effect on blood urea at postbypass interval was nonsignificant (P > 0.05) [Table 2].
Table 2: Comparison of mean serum creatinine and blood urea between both groups

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  Discussion Top

The issue of choosing the right priming solution for adult's CPB patients has been studied and argued for at least three decades.[10],[11] Two priming solutions were compared on the acid–base effects and other parameters during the perioperative and postoperative period for adult cardiac surgery.[12] This study suggested that Plasmalyte-A as more favorable priming solution with less metabolic acidosis than Ringer's lactate solution for the CPB in elective adult cardiac surgeries.

From the previous study done by Liskaser et al. on 22 patients undergoing coronary artery bypass surgery (CABG) operation on CPB. They used two different priming solutions such as Ringer lactate and Plasmalyte-A and concluded that metabolic acidosis induced by CPB appears to be affected by the fluid used in pump prime. Liskaser et al. studied changes in metabolic acidosis between two groups based on pump prime. One group of 11 individuals receive Ringer lactate and the other group of 11 individuals receives Plasmalyte-A as priming solution. The mean value of base excess increased from 0.95 mEq/l (prebypass) to −3.65 mEq/l (after 2-min initiation of bypass) with the P < 0.001 for Ringer lactate and for Plasmalyte-A group, mean value was 1.17 mEq/l to −3.20 mEq/l. The mechanism of metabolic acidosis was different in both groups. They concluded that acidosis was due to hyperchloremia in the Ringer lactate prime, and the acidosis in Plasmalyte-A prime was induced by increasing unmeasured anions such as acetate and gluconate. Our study is in correlation with this study. In our study, patient numbers are more and participants were divided into Group P for Plasmalyte-A (n = 26) and Group R (n = 26) for Ringer lactate.[13],[14]

Weinberg et al. conducted a study on 50 adult patients undergoing cardiac surgeries comparing Plasmalyte-148 and Hartmann solution as a pump prime. One group of 25 participants receive Plasmalyte-148, and the other group of 25 participants receives Hartmann solution. There was significant hyperchloremia and hyperlactatemia across all the surgery with Hartmann solution compared with Plasmalyte. Plasmalyte group did not showed hyperlactatemia, the mechanism with Plasmalyte was the production of unmeasured anions such as acetate and gluconate. Our study also collaborate, wherein the sample was collected at different timings, and participants were divided into Group P for Plasmalyte-A (n = 26) and Group R (n = 26). According to our study, there was significant hyperchloremia and hyperlactatemia across all the surgery with Ringer lactate compared with Plasmalyte. However, in the Plasmalyte group, there was no hyperchloremia and hyperlactatemia.[15]

Surabhi and Kumar done near similar study of total 80 adult patients undergone only valvular heart surgeries on CPB. Their patients were randomized into two groups, Group I (Ringer lactate) and Group II (Plasmalyte-A). In the Ringer lactate group, during CPB, there was a decrease in pH from 7.428 ± 0.029 at prebypass to 7.335 ± 0.06 at 30 min after bypass with a P < 0.05. In our current study, PH in the Ringer lactate group was decreased with a mean from 7.41 ± 0.05 at prebypass to 7.39 ± 0.05 at 40 min of the bypass with P < 0.05. On comparing the results of both studies, the Ringer lactate group had significant fall in bicarbonate, base excess, with increase in lactate levels during the bypass. The mean SID decreased during the CPB in the Ringer lactate group from 41.102 at prebypass to 35.66 at 30 min of bypass. The chloride levels were similar throughout CPB in both groups. Comparing the results with the current study, the mean SID decreased during the CPB in the Ringer lactate group from 31.96 ± 2.88 at prebypass to 30.33 ± 3.80 at 30 min bypass due to the hyperchloremia and hyperlactatemia.[16]

The findings of our study correlate well with the previous other studies regarding the effects of pump prime on acid–base balance induced by CPB. Moreover, the findings suggest that the Plasmalyte-A is a better priming solution than Ringer lactate. In the Plasmalyte-A group, the fluctuations of pH, bicarbonate, SID, and other parameters are almost similar to the baseline values compared to Ringer lactate as priming fluid.[17]

  Conclusion Top

An ideal priming solution should have the same electrolyte content as that of plasma. The use of two priming solutions has different impacts on the metabolic parameters for the patients undergoing cardiac surgical procedures. Patients who received Plasmalyte-A for CPB prime developed lesser metabolic acidosis compared to another group. The use of Plasmalyte-A as a prime fluid helped maintain adequate levels of lactate and bicarbonate. Plasmalyte-A is more balanced crystalloid solution having electrolyte constitutions near similar to plasma henceforth, as a priming solution, it is better for priming of CPB circuit. These findings establish that the balanced priming solution may improve the outcome of the patients undergoing elective adult cardiac surgeries on CPB.

Limitations of the study

Sample size is of only 52 adult subjects. We have only four cases of CABG in both groups (total eight CABG cases only). Majority of cases (total 44/52) were valvular diseases patient. Cases were included with age limitations from 18 to 70 years. We have not taken pediatric age group and congenital heart disease patients so these results cannot be generalized. The study design was observational; however, the data analyzed were prospectively collected and entered a database as part of routine patient management.


We are thankful to Dr. Bhavana Gupta, Assistant Professor of Anaesthesia department, AIIMS Rishikesh-249203 for her support in data analysis and statistical assessment.

Ethical clearance

Proper Ethical clearance for this study has taken from Institute ethical committee.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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Liskaser FJ, Bellomo R, Hayhoe M, Story D, Poustie S, Smith B, et al. Role of pump prime in the etiology and pathogenesis of cardiopulmonary bypass-associated acidosis. Anesthesiology 2000;93:1170-3.  Back to cited text no. 13
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1], [Table 2]


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