Effect of pump prime on acidosis, strong-ion-difference and unmeasured ions during cardiopulmonary bypass

Balanced forced-diuresis as a renal protective approach in cardiac surgery: Secondary outcomes of electrolyte changes

Objectives

Forced‐diuresis during cardiopulmonary bypass (CPB) can be associated with significant electrolyte shifts. This study reports on the serum electrolyte changes during balanced forced‐diuresis with the RenalGuard® system (RG) during CPB.

Methods

Patients at risk of acute kidney injury (AKI)—(history of diabetes &/or anaemia, e‐GFR 20–60 ml/min/1.73 m², anticipated CPB time >120 min, Log EuroScore >5)—were randomized to either RG (study group) or managed as per current practice (control group).

Results

The use of RG reduced AKI rate (10% for RG and 20.9% in control, p = .03). Mean urine output was significantly higher in the RG group during surgery (2366 ± 877 ml vs. 765 ± 549 ml, p < .001). The serum potassium levels were maintained between 3.96 and 4.97 mmol/L for the RG group and 4.02 and 5.23 mmol/L for the controls. Median potassium supplemental dose was 60 (0–220) mmol (RG group) as compared to 30 (0–190) mmol for control group over first 24 h (p < .001). On Day 1 post‐op, there were no significant differences in the serum sodium, potassium, calcium, magnesium, phosphate, and chloride levels between the two groups. Otherwise, postoperative clinical recovery was also similar.

Conclusions

Balanced forced‐diuresis with the RG reduced AKI rates after on‐pump cardiac surgery compared to controls. Although the RG group required higher doses of IV potassium replacement in the postoperative period, normal serum levels of potassium were maintained by appropriate intravenous potassium supplementation and the clinical outcomes between groups were similar.

Comparison of ringer's lactate and plasmalyt-a as cardiopulmonary bypass prime for bypass associated acidosis in valve replacement surgeries

Introduction:

A wide range of acid base fluctuations are seen during Cardiopulmonary bypass (CPB) and the development of metabolic acidosis is well recognized. We conducted a study tocompare the metabolic effects of Ringer lactate and Plasmalyte-A as CPB prime in causing bypass associated acidosis in valve replacement surgeries.

Methods:

We performed a prospective, randomized controlled study on a total of 80 adult patients undergoing CPB for valvular heart surgeries. The patients were randomized into two groups: Group I (Ringer Lactate) and Group II (Plasmalyte-A). Arterial blood samples were taken before initiating CPB, 30 minutes after starting CPB, then every half hourly till termination of CPB and after half an hour stay in the ICU post operatively to analyze primarily H+ ions, bicarbonates, lactate and strong ion difference.

Results and Discussion:

The results were analyzed in a quantitative manner. In Ringer Lactate group, during CPB, there was reduction in pH from 7.428 ± 0.029 at T1 to 7.335 ± 0.06 (P < 0.01) and 7.358 ± 0.06 (P < 0.01) at T2 and T3 respectively. Mean bicarbonates decreased in Ringer Lactate group during CPB from 24.28 ± 1.65 mEq/L at T1 to 20.98 ± 2.97 mEq/L at T2 (P < 0.01). In Plasmalyte-A group, mean pH, bicarbonate, strong ion difference (SID) were comparable at all time intervals (P > 0.05). In Ringer Lactate group, maximum surge in mean blood lactate levels was seen from 0.85 ± 0.35 mmol/l at T1 to 4.29 ± 1.78 mmol/L (P < 0.01) and 4.17 ± 1.28 mmol/L (P < 0.01) at T2 and T3, respectively. Such surge was not seen in Plasmalyte-A group. The mean SID decreased during the CPB in Ringer Lactate group from 41.102 mEq/L at T1 to 35.66 mEq/L (P = 0.033) at T2 implying metabolic acidosis. Numbered patients having hypotension and arrhythmias were also higher in Ringer Lactate group again indicating higher acidosis.

Conclusion:

The different composition of Plasmalyte-A and Ringer Lactate have different metabolic implications for patients undergoing cardiac surgery. Patients who received Plasmalyte-A as cardiopulmonary bypass prime developed less metabolic acidosis. Hence we conclude that Plasmalyte-A is the preferred cardiopulmonary bypass prime in adult patients undergoing valve replacement surgeries.

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

BACKGROUND

The optimal prime solution for the cardiopulmonary bypass (CPB) circuit in adult cardiac surgery has not yet been defined. Mannitol is widely used in the priming solution for CPB despite the fact that there is no clear consensus on the role of mannitol in cardiac surgery. The aim of this study was to investigate the effect of mannitol in the CPB prime solution.

METHODS

This prospective, randomized, double-blind study included 40 patients with normal cardiac and renal functions, who underwent coronary artery bypass grafting. One group received a prime based on Ringer's acetate (n = 20), and the other a prime consisting of Ringer's acetate with 200 mL mannitol (n = 20). Changes in osmolality, acid-base status, electrolytes, and renal-related parameters were monitored.

RESULTS

No significant differences were found in osmolality between the Ringer's acetate group and the mannitol group at any time. The mannitol group showed a pronounced decrease in sodium, from 138.7 ± 2.8 mmol/L at anaesthesia onset, to 133.9 ± 2.6 mmol/L after the start of CPB (P < .001). No differences were seen in the renal parameters between the groups, apart from a short-term effect of mannitol on peroperative urine production (P = .003).

CONCLUSION

We observed no effects on osmolality of a prime solution containing mannitol compared to Ringer's acetate-based prime in patients with normal cardiac and renal function. The use of mannitol in the prime resulted in a short-term, significant decrease in sodium level.

Metabolic acidosis and the role of unmeasured anions in critical illness and injury

Acid-base disorders are frequently present in critically ill patients. Metabolic acidosis is associated with increased mortality, but it is unclear whether as a marker of the severity of the disease process or as a direct effector. The understanding of the metabolic component of acid-base derangements has evolved over time, and several theories and models for precise quantification and interpretation have been postulated during the last century. Unmeasured anions are the footprints of dissociated fixed acids and may be responsible for a significant component of metabolic acidosis. Their nature, origin, and prognostic value are incompletely understood. This review provides a historical overview of how the understanding of the metabolic component of acid-base disorders has evolved over time and describes the theoretical models and their corresponding tools applicable to clinical practice, with an emphasis on the role of unmeasured anions in general and several specific settings.

Plasma-Lyte 148 vs. Hartmann's solution for cardiopulmonary bypass pump prime: a prospective double-blind randomized trial

BACKGROUND

The mechanisms of acid-base changes during cardiopulmonary bypass (CPB) remain unclear. We tested the hypothesis that, when used as CPB pump prime solutions, Plasma-Lyte 148 (PL) and Hartmann's solution (HS) have differential mechanisms of action in their contribution to acid-base changes.

METHODS

We performed a prospective, double-blind, randomized trial in adult patients undergoing elective cardiac surgery with CPB. Participants received a CPB prime solution of 2000 mL, with either PL or HS. The primary endpoint was the standard base excess (SBE) value measured at 60 minutes after full CPB flows (SBE60min). Secondary outcomes included changes in SBE, pH, chloride, sodium, lactate, gluconate, acetate, strong ion difference and strong ion gap at two (T2min), five (T5min), ten (T10min), thirty (T30min) and sixty (T60min) minutes on CPB. The primary outcome was measured using a two-tailed Welch's t-test. Repeated measures ANOVA was used to test for differences between time points.

RESULTS

Twenty-five participants were randomized to PL and 25 to HS. Baseline characteristics, EURO and APACHE scores, biochemistry, hematology and volumes of cardioplegia were similar. Mean (SD) SBE at T60min was -1.3 (1.4) in the PL group and -0.1 (2.7) in the HS group; p=0.55. No significant differences in SBE between the groups was observed during the first 60 minutes (p=0.48). During CPB, there was hyperacetatemia and hypergluconatemia in the PL group and hyperlactatemia and hyperchloremia in the HS group. No significant difference between the groups in plasma bicarbonate levels and total weak acid levels were found. Complications and intensive care unit and hospital length of stays were similar.

CONCLUSIONS

During CPB, PL and HS did not cause a significant metabolic acidosis. There was hyperacetatemia and hypergluconatemia with PL and hyperchloremia and hyperlactatemia with HS. These physiochemical effects appear clinically innocuous.

Lactate Elevation During and After Major Cardiac Surgery in Adults: A Review of Etiology, Prognostic Value, and Management

Elevated lactate is a common occurrence after cardiac surgery. This review summarizes the literature on the complex etiology of lactate elevation during and after cardiac surgery, including considerations of oxygen delivery, oxygen utilization, increased metabolism, lactate clearance, medications and fluids, and postoperative complications. Second, the association between lactate and a variety of outcomes are described, and the prognostic role of lactate is critically assessed. Despite the fact that elevated lactate is strongly associated with many important outcomes, including postoperative complications, length of stay, and mortality, little is known about the optimal management of postoperative patients with lactate elevations. This review ends with an assessment of the limited literature on this subject.

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

INTRODUCTION

As even small concentrations of acetate in the plasma result in pro-inflammatory and cardiotoxic effects, it has been removed from renal replacement fluids. However, Plasma-Lyte 148 (Plasma-Lyte), an electrolyte replacement solution containing acetate plus gluconate is a common circuit prime for cardio-pulmonary bypass (CPB). No published data exist on the peak plasma acetate and gluconate concentrations resulting from the use of Plasma-Lyte 148 during CPB.

METHODS

Thirty adult patients were systematically allocated 1:1 to CPB prime with either bicarbonate-balanced fluid (24 mmol/L bicarbonate) or Plasma-Lyte 148. Arterial blood acetate, gluconate and interleukin-6 (IL-6) levels were measured immediately before CPB (T1), three minutes after CPB commencement (T2), immediately before CPB separation (T3), and four hours post separation (T4).

RESULTS

Acetate concentrations (normal 0.04 to 0.07 mmol/L) became markedly elevated at T2, where the Plasma-Lyte group (median 3.69, range (2.46 to 8.55)) exceeded the bicarbonate group (0.16 (0.02 to 3.49), P < 0.0005). At T3, levels had declined but the differential pattern remained apparent (Plasma-Lyte 0.35 (0.00 to 1.84) versus bicarbonate 0.17 (0.00 to 0.81)). Normal circulating acetate concentrations were not restored until T4. Similar gluconate concentration profiles and inter-group differences were seen, with a slower T3 decay. IL-6 increased across CPB, peaking at T4, with no clear difference between groups.

CONCLUSIONS

Use of acetate containing prime solutions result in supraphysiological plasma concentrations of acetate. The use of acetate-free prime fluid in CPB significantly reduced but did not eliminate large acetate surges in cardiac surgical patients. Complete elimination of acetate surges would require the use of acetate free bolus fluids and cardioplegia solutions.

TRIAL REGISTRATION

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12610000267055.