Abstract
Background
Open cardiac surgery with cardiopulmonary bypass (CPB) contributes to postoperative electrolyte imbalances, which increases the risk of complications like arrhythmias. These imbalances stem from fluid shifts, hemodilution, acid-base disturbances, and factors such as cardioplegic solutions, hypothermia, elevated catecholamine levels, and antidiuretic hormone release, as well as non-pulsatile blood flow. Early monitoring and targeted prevention are crucial to managing these risks and improving postoperative outcomes.
Objective
This study aimed to investigate the prevalence of electrolyte imbalances in pediatric patients undergoing cardiac surgery while considering potential influencing factors such as age, gender, body mass index (BMI), type of cardiac surgery, and cardiopulmonary bypass (CPB) duration.
Materials and methods
A retrospective cross-sectional study was conducted at the French Medical Institute for Mothers and Children in Kabul, Afghanistan, from January 1, 2021, to September 30, 2023. A total of 393 pediatric patients aged 0–18 years undergoing open cardiac surgery were included, excluding those with closed cardiac surgery, incomplete data, chronic renal disease, or gastrointestinal disorders. Data collected included patient demographics, surgery type (cyanotic vs. acyanotic), primary diagnoses (e.g., ASD, VSD, TOF), RBC transfusion amounts, CPB duration, and electrolyte levels measured before surgery, immediately after surgery, and on the first and second postoperative days. Data were analyzed using SPSS version 22, employing descriptive statistics and various statistical tests (Kolmogorov-Smirnov, Wilcoxon signed rank, Kruskal-Wallis, binomial regression, Spearman correlation), with significance set at p < 0.05.
Results
Participants ranged from 0 to 18 years, with a mean age of 5.8 years (SD = 4.10), and 55.5 % (n = 218) were male. Most patients (93.4 %, n = 367) were classified as underweight, with a mean body mass index (BMI) of 15.8 kg/m 2 (SD = 2.31). VSD closure was performed in 41.3 % (n = 162) of cases, and 76 % (n = 299) had a bypass duration exceeding 60 min. Electrolyte imbalances were common among the patients: hyponatremia occurred in 18.6 % (n = 72) preoperatively, rising to 60.3 % (n = 199) by the second postoperative day. Hypokalemia increased from 6.9 % (n = 27) preoperatively to 64 % (n = 251) post-surgery, while hypocalcemia was noted in 31 % (n = 122) on the first postoperative day. Sodium levels rose significantly after packed cell transfusions (p < 0.001), and magnesium levels increased in toddlers and adolescents (p < 0.001). Notably, postoperative potassium levels were 0.6 times lower in females compared to males (p = 0.026), and patients undergoing surgery for over 2 h had 2.6 times higher odds of sodium imbalances (p < 0.001).
Conclusion
Pediatric patients undergoing cardiac surgery are at high risk for electrolyte disorders, particularly hypokalemia and hyponatremia, which can lead to serious complications. Key predictors include the type of surgical procedure, cardiac lesions, and factors such as age, gender, body mass index (BMI), and cardiopulmonary bypass (CPB) duration. While fluid management and diuretics are important considerations, careful monitoring and prompt correction of electrolyte levels are essential to prevent postoperative complications and improve outcomes.
Highlights
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64% hypokalemia and 31% hypocalcemia observed in 393 pediatric cardiac surgery patients
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Sodium levels increased significantly after RBC transfusions (p < 0.0001).
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Magnesium levels rose in toddlers and adolescents; calcium increased only in adolescents.
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Females exhibited higher post-surgery magnesium and potassium levels
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Study emphasizes the need for targeted monitoring to improve pediatric cardiac care.
1
Introduction
Pediatric cardiac surgery is a critical area of healthcare, addressing congenital and acquired heart conditions in children [ , ]. The complexity of these surgeries often leads to various postoperative complications, one of which is the occurrence of electrolyte imbalances [ , ]. These imbalances can significantly impact a patient’s recovery and overall health, leading to postoperative arrhythmias and low cardiac index [ ]. Electrolyte imbalances are prevalent in pediatric patients undergoing cardiac surgery, especially following cardiopulmonary bypass (CPB) [ , ].
Factors contributing to these imbalances include hemodilution from CPB, CPB duration, diuretic use, and blood transfusions [ ]. The circuit prime volume during CPB can cause hemodilution, often necessitating multiple blood transfusions [ ]. While essential for managing blood loss, transfusions can lead to electrolyte imbalances, especially in younger patients receiving near-total blood volume [ , , ]. Common abnormalities include hyperkalemia and hypocalcemia, influenced by factors beyond transfusions, such as blood product storage duration and the type of cardioplegia used [ , ].
Cardioplegic solutions and induced hypothermia alter potassium metabolism and pH. During CPB, dilution from pump perfusate and crystalloid resuscitation disrupts fluid and electrolyte homeostasis, causing sodium fluctuations that can lead to hyponatremia and postoperative seizures [ , ].
Excessive hydration from intravenous fluids during CPB exacerbates hydroelectrolytic imbalances, affecting sodium and potassium levels and influenced by water migration between body compartments and potential metabolic acidosis [ ]. Additionally, diuretics like frusemide, frequently used in pediatric cardiology, can cause significant electrolyte disturbances, including potassium wasting and low sodium and magnesium levels, resulting in serious complications such as cardiac arrhythmias [ ].
Electrolytes maintain electrical neutrality in cells and generate action potentials in nerves and muscles [ ]. Imbalances can disrupt bodily functions and lead to severe complications, particularly in children with underlying health issues [ ]. Critically ill patients often experience disturbances like ICU-acquired hyponatremia and hypernatremia after cardiac surgery, causing neurological symptoms such as seizures and confusion [ ]. Additionally, hyperkalemia poses a serious risk of life-threatening cardiac arrhythmias, especially in critically ill adults and pediatric trauma patients’ post-transfusion [ ]. Hypokalemia can cause muscle weakness and paralysis, while hypocalcemia may lead to muscle spasms and arrhythmias [ ]. Furthermore, hypomagnesemia is also common in cardiac surgery patients and is linked to increased cardiac arrhythmias and adverse events [ ].
Despite the recognized importance of monitoring and managing electrolyte levels, there is a lack of research specifically addressing this issue in pediatric surgery in Afghanistan. These imbalances may present differently due to unique factors such as healthcare infrastructure, resource availability, and variations in clinical practice. Limited access to advanced monitoring technologies and electrolyte replacement therapies can exacerbate these imbalances. Additionally, cultural factors, nutritional differences, and variations in surgical procedures contribute to distinct patterns of disturbances in this population compared to other regions. Existing studies often focus on adults or fail to address the specific challenges faced by pediatric patients in the Afghan healthcare context.
This study aims to investigate the prevalence of electrolyte imbalances in pediatric patients undergoing cardiac surgery in Afghanistan, considering various factors such as age, gender, body mass index (BMI), and duration of cardiopulmonary bypass (CBP), as well as type and amount of blood transfusion. By focusing on this critical issue, the research seeks to provide insights that can improve clinical practices and enhance patient outcomes. Understanding the factors that contribute to these imbalances will not only benefit individual patients but also inform broader healthcare strategies in the region, ultimately leading to better management of pediatric cardiac care.
2
Materials and methods
2.1
Study design
A hospital-based retrospective cross-sectional design, analyzing existing data, was performed at the French Medical Institute for Mothers and Children (FMIC), Kabul, Afghanistan. The study period spanned from January 1, 2021, to September 30, 2023, with data collection occurring from May to September 2023. Ethical approval was obtained from the research committee of FMIC.
*Gastrointestinal disorders (GI).
2.2
Participants
Initially, 811 patients were identified from the Pediatric Intensive Care Unit (PICU) database. After excluding 222 patients who had undergone closed-heart surgery, 589 eligible patients who underwent open-heart surgery were selected. Of these, 537 were pediatric patients. Following the exclusion of 26 patients due to incomplete data, 511 patients remained. From this population, 393 patients were randomly selected for the study based on sample size calculations and specific inclusion criteria.
The inclusion criteria focused on children aged 0 to 18 years who had undergone cardiac surgery for congenital heart disease and were directly admitted to the PICU from the operating theater. In cases where a child was admitted to the PICU multiple times following cardiac surgery during the study period, only the admission following the most recent surgical procedure was considered for inclusion.
2.3
Sample size calculation
The sample size for this study was calculated using the formula n = ( Ez · σ )2, where z represents the Z-value for a 95 % confidence level, σ is the standard deviation of the outcome variable, and E is the margin of error. Using a Z-value of 1.96, a standard deviation of 0.5, and a margin of error of 0.05, the minimum required sample size was determined to be 385 patients. From the eligible population of 511 patients, 393 were randomly selected based on this sample size calculation.
2.4
Data collection
Patient demographics, diagnosis, type and amount of RBC transfusion, cardiopulmonary bypass (CBP) time, and electrolyte levels before surgery, immediately after surgery, as well as on the first- and second-day post-operation, were recorded. The data collection process took place between May and September 2023, focusing on patients who underwent surgery for congenital heart disease from January 1, 2021, to September 30, 2023. The flowchart in Fig. 1 illustrates the study population, detailing the actual participant numbers at each stage of data collection.
This retrospective study utilized existing patient data from the French Medical Institute for Mothers and Children (FMIC), Kabul, Afghanistan. Institutional Review Board (IRB)/Ethics Committee approval was obtained from the research committee of the Kabul University of Medical Sciences (KUMS), Kabul, Afghanistan. The approval was granted on December 28, 2022 (protocol number 54). Ethical approval for the use of the secondary data was also obtained from the FMIC research committee (approval number 044-FMIC-ER-23). As this was a retrospective study using de-identified patient records, informed consent was not required.
2.5
Laboratory measurements
Laboratory tests were performed to measure serum sodium, potassium, calcium, and magnesium levels. These measurements were obtained from laboratory result sheets at four different stages: before surgery, early after surgery, and the first and second days after the operation. Normal ranges for serum sodium were considered to be between 136 and 145 mmol/dl; for serum potassium, between 3.5 and 5.5 mmol/dl; for serum calcium, between 8.7 and 10.7 mg/dl; and for serum magnesium, between 2.3 and 2.5 mg/dl, based on Gregory s Pediatric Anesthesia – 2020 [ ].
2.6
Treatment of abnormal electrolyte levels
In the present institute, comprehensive details pertaining to the management of electrolyte imbalances for different electrolytes are outlined. Symptomatic hyponatremia was corrected by administering a solution of 4–6 ml/kg of 3 % sodium chloride if the serum sodium level fell below 136 mmol/dl. Hypokalemia was corrected by administering intravenous potassium chloride at a rate of 0.5 mmol/kg over 1 to 2 h. Low calcium levels were treated by giving a solution with calcium gluconate at a rate of 1 ml/kg every 6 to 8 h if the calcium level dropped below normal. Hypomagnesemia was corrected immediately after detection of serum magnesium levels below 1.5 mg/dl by administering intravenous magnesium sulfate at a rate of 50–100 mg/kg over a period of 30 min.
In managing postoperative hyponatremia in cardiac patients, fluid restriction and controlled diuretics are prioritized, with hypertonic saline avoided to prevent exacerbating heart failure. Cardioplegia involves a combination of Histidine-Tryptophan-Ketoglutarate (HTK) and blood cardioplegia, administered at specified volumes and pressures. Maintenance fluids were isotonic, with TPN provided as needed. Diuretics such as furosemide (1 mg/kg every 8 h) were utilized for fluid overload, and acidosis was managed by monitoring blood gases, with sodium bicarbonate administered for base deficits exceeding 4 mEq/l.
2.7
Inclusion criteria
All medical records of pediatric patients who underwent open cardiac surgery at FMIC between January 1, 2021, and September 30, 2023, were included in this study.
2.8
Exclusion criteria
Patients with incomplete relevant information or those with chronic renal disease or gastrointestinal disorders were excluded from the study analysis.
2.9
Statistical analysis
After the completion of data collection, the collected data were subjected to statistical analysis. The Kolmogorov-Smirnov test was conducted to assess the distribution of the investigated data, revealing a skewed distribution. Consequently, median values were primarily utilized for analysis. The patients were categorized into four groups based on age and type of cardiac surgery, as well as into three groups based on BMI, duration of bypass, and blood transfusion (refer to Table 1 ). The data are presented as mean ± standard deviation (with minimum and maximum levels). In addition to basic descriptive statistics, frequency and percentage were calculated for baseline characteristics. Further statistical analysis was performed using SPSS version 22 software. Statistical significance was determined at a p-value < 0.05. Comparison between serological data before surgery, immediately after surgery, 24 h after surgery, and the second postoperative day with age and gender were assessed using the Wilcoxon signed rank test. The Kruskal-Wallis rank test was employed to compare postoperative electrolyte levels with duration of bypass, type and amount of blood transfusion, and types of cardiac surgery. The categorical nature of the data required the use of binomial regression analysis to determine the prevalence ratio. Furthermore, Spearman correlation test was conducted to investigate correlations among electrolyte levels.
| Variable | Categories | Frequency | Percentile |
|---|---|---|---|
| Gender | Female Male | 175 218 | 44.5 55.5 |
| Age (years) | Toddler 1– Preschooler 3– School age 5– Adolescent 12> | 107 135 102 49 | 27.2 34.4 26.0 12.5 |
| 4.2 (5.4), 1–17 ⁎ | |||
| BMI | Underweight Ideal Pre obese | 367 23 3 | 93.4 5.90 .8 |
| 14.8 (2.4), 7.1–27.5 ⁎ | |||
| Bypass duration (min) | >60 60– 120> | 39 293 49 | 10.2 76.9 12.9 |
| 75 (30), 30–300 ⁎ | |||
| Blood transfusion | Packed cell Whole blood Mixed | 281 69 42 | 71.7 17.6 10.7 |
| Type of cardiac surgery | TOF VSD Closure ASD Closure Other | 127 162 84 19 | 32.4 41.3 21.4 4.8 |
3
Results
The present study enrolled 393 pediatric patients who underwent cardiac surgery. The median age of the patients was 4.2 years (IQR = 5.4), and 218 (55.5 %) of them were male. The majority of the patients, 367 (93 %) were classified as underweight, with a median body mass index of 14.8 kg/m2 (IQR = 2.4). Ventricular septal defect (VSD) closure was the most frequently performed surgery, accounting for 162 (41 %) of the cases. Additionally, 293 patients (76 %) had a bypass duration exceeding 60 min, and 281 patients (72 %) received packed-cell transfusions, making it the most common type of blood transfusion administered. A summary of the clinical and demographic characteristics of patients is shown in Table 1 .
3.1
Serum electrolyte levels of cardiac surgical patients
The percentage of electrolyte imbalance between preoperative and immediately after surgery, the first and second postoperative days, is shown in Table 2 . Prior to surgery, 72 patients (18.6 %) exhibited hyponatremia, and all the patients with imbalances received appropriate management to correct these levels before the cardiac procedure.
| Variable | Category | Pre operative, n (%) | Post operative, n (%) | ||
|---|---|---|---|---|---|
| 1 h | First day | Second day | |||
| Na + | Hyponatremia <136 mmol/l | 72 (19) | 7 (2) | 67 (18) | 199 (60) |
| Hypernatremia >145 mmol/l | 2 (1) | 64 (17) | 18 (5) | 4 (1) | |
| Normal | 313 (81) | 320 (82) | 292 (78) | 127 (39) | |
| K + | Hypokalemia <3.5 mmol/l | 27 (7) | 251 (64) | 72 (19) | 100 (28) |
| Hyperkalemia >5.5 mmol/l | 1 (1) | 0 (0) | 3 (1) | 2 (1) | |
| Normal | 365 (92) | 141 (36) | 314 (81) | 256 (72) | |
| Ca 2+ | Hypocalcemia <8.7 mg/dl | 54 (14) | 120 (31) | 243 (64) | 209 (63) |
| Hypercalcemia >10.1 mg/dl | 21 (80) | 79 (20) | 16 (4) | 117 (35) | |
| Normal | 301 (6) | 191 (49) | 122 (32) | 6 (2) | |
| Mg 2+ | Hypomagnesemia <1.6 mg/dl | 8 (2) | 16 (4) | 34 (11) | 46 (18) |
| Hypermagnesemia >2.5 mg/dl | 20 (5) | 82 (22) | 6 (2) | 1 (1) | |
| Normal | 345 (93) | 284 (74) | 269 (88) | 210 (82) | |
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