Metabolic alkalosis after pediatric cardiac surgery

Metabolic alkalosis following mitral valvuloplasty in a dog with preoperative acute kidney injury

CASE DESCRIPTION

An 11-year-old sexually intact male Shih Tzu diagnosed with acute kidney injury and left-sided congestive heart failure that had nonelective mitral valve surgery.

CLINICAL FINDINGS

Metabolic alkalosis developed postoperatively, and plasma bicarbonate concentration peaked 2 days after surgery (40.2 mmol/L; pH, 7.550).

TREATMENT AND OUTCOME

Acetazolamide administration increased the urinary excretion of bicarbonate and contributed to the improvement of the dog's acid-base status and oxygenation capacity. Metabolic alkalosis persisted for 4 days after surgery, and no treatment was required after resolution. Plasma urea nitrogen and creatinine concentrations normalized 2 days after surgery.

CLINICAL RELEVANCE

Severe metabolic alkalosis can occur as a complication following mitral valve surgery. Acetazolamide may be suitable for the treatment of severe metabolic alkalosis.

Metabolic Alkalosis in the Pediatric Patient: Treatment Options in the Pediatric ICU or Pediatric Cardiothoracic ICU Setting

Metabolic alkalosis is characterized by the primary elevation of the serum bicarbonate concentration with a normal or elevated partial pressure of carbon dioxide. Although there may be several potential etiologies in the critically ill patient in the pediatric or cardiothoracic intensive care unit, metabolic alkalosis most commonly results from diuretic therapy with chloride loss. In most cases, the etiology can be determined by a review of the patient's history and medication record. Although generally innocuous with limited impact on physiologic function, metabolic alkalosis may impair central control of ventilation, especially when weaning from mechanical ventilation. The following manuscript presents the normal homeostatic mechanisms that control pH, reviews the etiology of metabolic alkalosis, and outlines the differential diagnosis. Options and alternatives for treatment including pharmacologic interventions are presented with a focus on these conditions as they pertain to the patient in the pediatric or cardiac intensive care unit.

Optimal Sweep Gas to Blood Flow Ratio (V/Q) for Initiation of Cardiopulmonary Bypass in a Pediatric Patient Population: A Retrospective Analysis

The optimal setting to achieve a suitable PaCO₂ value of 35-45 mmHg upon initiating cardiopulmonary bypass (CPB) in the pediatric population is undefined in the literature. Sweep gas is set upon initiating and modified throughout CPB to reduce potential complications related to compensatory metabolic acidosis or metabolic alkalosis and associated cerebral blood flow fluctuations. This study retrospectively examined 1,077 CPB cases for which PaCO₂ values were no less than 30 mmHg and no greater than 50 mmHg on the pre-CPB blood gas result. Through an observation of the results, we attempted to determine the optimal sweep gas setting upon initiating CPB to obtain a physiologic PaCO₂ value of 35-45 mmHg. The probability of achieving an optimal PaCO₂ value was modeled as a function of the average sweep gas to blood flow ratio during the period before the first blood gas on CPB. The median sweep gas to blood flow ratio (V/Q) was .64 (.51; .76), with a median first PaCO₂ value on CPB of 42 mmHg (38.8; 45). A .6 V/Q had an odds ratio (OR) of 1.57 of obtaining a PaCO₂ value between 35 and 45 mmHg on the first CPB blood gas when compared with a .4 V/Q (Figure 1Figure 1.Bivariate associations between PaCO₂ and the V/Q ratio. (A) Spike histogram with loess curve showing the proportion of patients with a first PaCO₂ value on CPB between 35 and 45 mmHg according to the V/Q ratio. (B) Scatterplot and loess curve (gray line) for PaCO₂ on CPB according to the V/Q ratio. Dashed lines indicate the target range of 35-45 mmHg. (C) Model-based estimate of the predicted probability and 95% CI for PaCO₂ on CPB between 35 and 45 mmHg according to the V/Q ratio obtained from logistic regression. (D) Model-based estimate of the predicted PaCO₂ on CPB according to the V/Q ratio obtained from ordinal regression. Prop, proportion.). A .9 V/Q had a 1.76 OR when compared with a .4 and a 1.12 OR when compared with .6. Using a .6 V/Q ratio achieved a PaCO₂ value within normal physiologic limits with no significant advantage to a higher V/Q ratio overall. However, younger or smaller patients required a higher V/Q to achieve similar probabilities of being within limits and similar PaCO₂ values when compared with the older or larger patients.

Acetazolamide Therapy for Metabolic Alkalosis in Pediatric Intensive Care Patients

OBJECTIVE

Patients in PICUs frequently present hypochloremic metabolic alkalosis secondary to loop diuretic treatment, especially those undergoing cardiac surgery. This study evaluates the effectiveness of acetazolamide therapy for metabolic alkalosis in PICU patients.

DESIGN

Retrospective, observational study.

SETTING

A tertiary care children's hospital PICU.

PATIENTS

Children receiving at least a 2-day course of enteral acetazolamide.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic variables, diuretic treatment and doses of acetazolamide, urine output, serum electrolytes, urea and creatinine, acid-base excess, pH, and use of mechanical ventilation during treatment were collected. Patients were studied according to their pathology (postoperative cardiac surgery, decompensated heart failure, or respiratory disease). A total of 78 episodes in 58 patients were identified: 48 were carried out in cardiac postoperative patients, 22 in decompensated heart failure, and eight in respiratory patients. All patients received loop diuretics. A decrease in pH and PCO2 in the first 72 hours, a decrease in serum HCO3 (mean, 4.65 ± 4.83; p < 0.001), and an increase in anion gap values were observed. Urine output increased in cardiac postoperative patients (4.5 ± 2.2 vs 5.1 ± 2.0; p = 0.020), whereas diuretic treatment was reduced in cardiac patients. There was no significant difference in serum electrolytes, blood urea, creatinine, nor chloride after the administration of acetazolamide from baseline. Acetazolamide treatment was well tolerated in all patients.

CONCLUSIONS

Acetazolamide decreases serum HCO3 and PCO2 in PICU cardiac patients with metabolic alkalosis secondary to diuretic therapy. Cardiac postoperative patients present a significant increase in urine output after acetazolamide treatment.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Fluid Management

OBJECTIVE

In this Consensus Statement, we review the etiology and pathophysiology of fluid disturbances in critically ill children with cardiac disease. Clinical tools used to recognize pathologic fluid states are summarized, as are the mechanisms of action of many drugs aimed at optimal fluid management.

DATA SOURCES

The expertise of the authors and a review of the medical literature were used as data sources.

DATA SYNTHESIS

The authors synthesized the data in the literature in order to present clinical tools used to recognize pathologic fluid states. For each drug, the physiologic rationale, mechanism of action, and pharmacokinetics are synthesized, and the evidence in the literature to support the therapy is discussed.

CONCLUSIONS

Fluid management is challenging in critically ill pediatric cardiac patients. A myriad of causes may be contributory, including intrinsic myocardial dysfunction with its associated neuroendocrine response, renal dysfunction with oliguria, and systemic inflammation with resulting endothelial dysfunction. The development of fluid overload has been associated with adverse outcomes, including acute kidney injury, prolonged mechanical ventilation, increased vasoactive support, prolonged hospital length of stay, and mortality. An in-depth understanding of the many factors that influence volume status is necessary to guide optimal management.

Citrate metabolism and its complications in non-massive blood transfusions: association with decompensated metabolic alkalosis+respiratory acidosis and serum electrolyte levels

BACKGROUND AND OBJECTIVES

Metabolic alkalosis, which is a non-massive blood transfusion complication, is not reported in the literature although metabolic alkalosis dependent on citrate metabolism is reported to be a massive blood transfusion complication. The aim of this study was to investigate the effect of elevated carbon dioxide production due to citrate metabolism and serum electrolyte imbalance in patients who received frequent non-massive blood transfusions.

MATERIALS AND METHODS

Fifteen inpatients who were diagnosed with different conditions and who received frequent blood transfusions (10-30 ml/kg/day) were prospectively evaluated. Patients who had initial metabolic alkalosis (bicarbonate>26 mmol/l), who needed at least one intensive blood transfusion in one-to-three days for a period of at least 15 days, and whose total transfusion amount did not fit the massive blood transfusion definition (<80 ml/kg) were included in the study.

RESULTS

The estimated mean total citrate administered via blood and blood products was calculated as 43.2 ± 34.19 mg/kg/day (a total of 647.70 mg/kg in 15 days). Decompensated metabolic alkalosis+respiratory acidosis developed as a result of citrate metabolism. There was a positive correlation between cumulative amount of citrate and the use of fresh frozen plasma, venous blood pH, ionized calcium, serum-blood gas sodium and mortality, whereas there was a negative correlation between cumulative amount of citrate and serum calcium levels, serum phosphorus levels and amount of urine chloride.

CONCLUSION

In non-massive, but frequent blood transfusions, elevated carbon dioxide production due to citrate metabolism causes intracellular acidosis. As a result of intracellular acidosis compensation, decompensated metabolic alkalosis+respiratory acidosis and electrolyte imbalance may develop. This situation may contribute to the increase in mortality. In conclusion, it should be noted that non-massive, but frequent blood transfusions may result in certain complications.

Acetazolamide in Critically Ill Neonates and Children With Metabolic Alkalosis

Background: Acetazolamide is an option for hypochloremic metabolic alkalosis, but there are limited reports in children. Objective: To describe the acetazolamide regimen and outcomes in critically ill children with metabolic alkalosis. Methods: This was a descriptive, retrospective study of patients <18 years of age who received ≥3 doses of acetazolamide for metabolic alkalosis (ie, pH > 7.45 and bicarbonate [HCO3] > 26 mEq/L). Patients receiving other treatments for metabolic alkalosis within 24 hours of acetazolamide were excluded. The primary objective was to identify the mean dose and duration of acetazolamide. Secondary objectives were to determine the number of patients with treatment success (ie, serum HCO3 22-26 mEq/L) and occurrence of adverse events. Results: Thirty-four patients were included for analysis, the median age was 0.25 years (range = 0.05-12 years). The acetazolamide regimen included a mean dose of 4.98 ± 1.14 mg/kg for a mean number of 6.1 ± 5.3 (range = 3-24) doses. The majority (70.6%) received acetazolamide every 8 hours. Treatment success was achieved in 10 (29.4%) patients. Statistically significant differences were noted between the pre-acetazolamide and post-acetazolamide pH and HCO3, 7.51 ± 0.05 versus 7.37 ± 0.05 ( P < .001) and 39.4 ± 6.1 mEq/L versus 31.4 ± 7.5 mEq/L ( P < .001), respectively. Conclusions: This is the first study to evaluate acetazolamide dosing for metabolic alkalosis in children with and without cardiac disease. Acetazolamide treatment resulted in improved HCO3, but the majority of patients did not achieve our definition of treatment success. Future studies should elucidate the optimal acetazolamide regimen.

Acetazolamide Therapy for Hypochloremic Metabolic Alkalosis in Pediatric Patients With Heart Disease

BACKGROUND

Pediatric patients with heart disease are often treated with high doses of diuretics, which can lead to hypochloremic metabolic alkalosis. There are no data in children regarding the efficacy and safety of acetazolamide to treat hypochloremic metabolic alkalosis.

METHODS

Patients from January 2004 to June 2005 who received acetazolamide were identified. Inclusion criteria were: age less than 18 years, being a cardiology patient, diuretics use, and had received a 3-day course of acetazolamide. Demographic information was collected along with serum electrolytes, serum creatinine/blood urea nitrogen, urine output, pH, acid-base excess, concurrent medications, cardiac lesion/surgery, and incidence of adverse effects. Efficacy of acetazolamide was determined by comparing variables before and after the 3-day course. Statistical comparisons were made using Student's t-test.

RESULTS

A total of 28 patients were identified, 7 of whom received oral acetazolamide, 21 intravenous acetazolamide. Patients were a median of 2.5 (range, 0.3-20) months of age, and 57% (17/28) were female. Seventy-one percent of the cohort received acetazolamide after cardiac surgery. There was no significant difference in any electrolyte, blood urea nitrogen, or serum creatinine from baseline, except for serum bicarbonate, which decreased (36.2 +/- 4.6 vs. 30.9 +/- 4.5 mmol/L, P < 0.001), and chloride, which increased (91.1 +/- 6.8 vs. 95.4 +/- 6.2, P < 0.03). Acid-base excess values and pH decreased during therapy in patients who had the laboratory values drawn (n = 22). No change in urine output at 8 hours (5.2 +/- 2.3 vs. 4.9 +/- 2.3 mL/kg/hr, P = 0.6) or 24 hours (4.7 +/- 1.5 vs. 4.3 +/- 1.4 mL/kg/hr, P = 0.18) occurred after administration of acetazolamide.

CONCLUSION

Acetazolamide was safely used in pediatric patients with heart disease to lower serum bicarbonate and acid-base excess values and raise chloride values in hypochloremic metabolic alkalosis.