European Journal of Cardiovascular Medicine

The kidneys regulate electrolyte and acid-base balance, but CKD disrupts these processes, leading to serious complications. CKD affects 5–10% of the global population,¹ with a prevalence of around 800 per million in India.² Dialysis helps remove excess fluids, toxins like urea, and restores electrolyte balance by using a dialysate with normal mineral concentrations.³

Hemodialysis (HD) is an effective treatment for hyperkalemia, uremia, and reducing serum creatinine and salt levels in renal failure. Despite advancements in technology and pharmaceutical care, the mortality rate among dialysis patients remains high, with 9–13% of hemodialysis patients in India dying within a year. Many individuals with stable CKD have increased total body salt and water content, often undetectable on clinical examination. While CKD leads to a decline in GFR, urinary potassium excretion remains largely maintained due to aldosterone-dependent secretion in the distal nephron and enhanced GI potassium excretion. However, hyperkalemia can still occur suddenly due to factors like increased dietary potassium intake, hemolysis, hemorrhage, transfusion, protein breakdown, metabolic acidosis, and certain medications that impair renal potassium excretion.^4,5

Metabolic acidosis is common in severe CKD, as patients can acidify urine but struggle to excrete sufficient protons due to reduced ammonia production. Hyperkalemia further inhibits ammonia formation. Hyperkalemia and hyperchloremic metabolic acidosis often coexist in diabetic nephropathy, tubulointerstitial disease, and obstructive uropathy, even in early CKD (stages 1-3). Electrolyte imbalances during dialysis are linked to sudden cardiac fatalities and severe arrhythmias.^5-7

ECG changes are common in CKD patients and can help predict cardiovascular events. The prevalence of ECG abnormalities varies, and CKD patients are at risk of sudden cardiac mortality due to electrolyte imbalances and blood pressure fluctuations post-hemodialysis. Monitoring these patients after dialysis is crucial.⁸This study aimed to assess the frequency of ECG abnormalities in CKD patients and analyze electrolyte changes post-dialysis.

A cross-sectional study was conducted at a tertiary care medical center on patients with CKD undergoing hemodialysis. Total 200 patients aged more than 12 yearswith diagnosed with CKD according to KDIGO criteriaand patients with end-stage renal disease (ESRD), who provided consent were enrolled during the 18-month study period.Patients aged less than 12 years, patients with ischemic heart disease (based on medical history and ECG findings), ECG changes of atrial fibrillation, left ventricular hypertrophy, left bundle branch block (LBBB), or those on anti-arrhythmic medication and patients with acute renal failure, cardiovascular disease, hepatic disease, or any chronic or acute inflammatory illnesswere excluded.

Each subject underwent a detailed clinical history evaluation and clinical examination. The mean duration of dialysis sessions was 4 hours. Patients were treated with a bicarbonate dialysate containing the following electrolyte concentrations: K+ (2.0 mmol/L), Mg2+ (1.0 mmol/L), Ca2+ (1.75 mmol/L), Na+ (135 mmol/L), and HCO3 (32 mmol/L). The blood flow rate was maintained at 250–300 mL/min, with a dialysate flow of 500 mL/min. Dialysis was performed using a polysulfone-based dialysis membrane. Blood samples were obtained before and after each dialysis session to measure serum levels of K+, Ca2+, Mg++, Na+, HCO3, urea, and creatinine. Additionally, a standard 12-lead ECG was recorded before and after dialysis.ECG parameters analyzed included the amplitude of the P wave, QRS complex, T wave, and R wave, along with PR, QT, and R-R intervals. Changes in QT dispersion, sum of V1S + V5R, and ST depression were also assessed. Patients undergoing hemodialysis for the first time were included in the study. Data was collected using a predesigned, pretested questionnaire, including socio-demographic factors, clinical history, investigations, diagnosis, and treatment details.

Statistical analysis

Data was analyzed using IBM SPSS Ver. 20.0.0.0. Descriptive statistics was presented in the form of numbers and percentages. Association between the two non-parametric variables was evaluated using Pearson Chi-square test. Proportional comparison was done using Z test for two sample proportion. A p value A p value <0.05 was considered as statistically significant.

Majority of the patients were in the age range of 51-60 years (22%) followed by 31-40 years (21%),61-70 years (20%) and 41-50 years (19%) with male predominance (66%), (Table 1). Majority of the patients were hypertensive (65%). AV fistula was seen in 67%, AV graft in 27% and catheter in 6% of cases.

Table 1: Demographic profile of patients

There was a slight increase in SBP and a minor decrease in DBP post-dialysis, but neither change was statistically significant (>0.05). However, a significant reduction in weight was observed (p<0.001), indicating effective fluid removal during dialysis, (Table 2).

Table 2: Pre and post dialysis BP and weightchanges

Hemodialysis led to significant changes in serum sodium (p<0.001), calcium (p<0.05), potassium (p<0.001), magnesium (p<0.05), bicarbonate (p<0.001), urea (p<0.001), and creatinine (p<0.05) as shown in table 3.

Table 3:  Pre and post dialysis Serum electrolytes

Table 4 presents electrocardiographic changes before and after hemodialysis. The RR and PR intervals showed no significant difference (p=0.56 and p=0.58, respectively). A significant increase was observed in QRS amplitude (p<0.001) and QRS duration (p<0.001), while P-wave and T-wave amplitudes showed significant changes (p=0.001). The QT interval and corrected QT (QTc) interval decreased significantly post-dialysis (p<0.001 and p=0.01, respectively). Additionally, QT dispersion and corrected QT dispersion increased significantly (p<0.001). The sum of QRS duration, QRS amplitude, and V1S + V5R also increased significantly (p<0.001), whereas the sum of T-wave amplitude decreased (p<0.001). These findings highlight the significant impact of hemodialysis on cardiac electrical activity.

Table 4: Pre and post dialysiselectrocardiographic changes

The present study involved 200 CKD patients receiving hemodialysis at a tertiary care hospital, who were evaluated for the changes in serum electrolytes and ECG following hemodialysis.In the current study, there were decreased levels of potassium, calcium and magnesium after dialysis. Whereas sodium and bicarbonate levels increased following dialysis.Patients with CKD are more likely to have hyperkalemia, which increases their risk of cardiovascular complications such reduced action potential, increased QRS complex, and prolonged PR interval. Because hemodialysate rapidly shifts serum K+, it induces hypokalemia⁹, which necessitates strict monitoring and treatment. Hyperkalemia causes decreased resting membrane potential, slower conduction velocity, and faster repolarization on the other hand, Hypokalemia, which elevates the resting membrane potential and refractory period and may be arrhythmogenic, is the most common cause of death in most patients receiving chronic hemodialysis¹⁰

After HD, the potassium level in the current research dramatically decreased, (5.27 ± 1.01 v/s 3.70 ± 0.8, p<0.001) which is consistent with other study done by Ajam WH et al¹¹ and Tandukar et al¹². In the current study, post-dialysis sodium (139.6±3.61 vs. 137.12±3.45) was substantially greater than pre-dialysis sodium. The pre-HD Na+ in the study by Ajam WH et al¹¹ was 136.5±4.14 while the post-HD Na+ was 138.6±4.41 (p = 0.36). According to a study by Tarif Net al¹³mean blood Na+ levels were higher in post-HD patients than in pre-HD patients (138.00 ± 4.41 vs. 136.87±4.14)¹³. After HD, Andrews L et al¹⁴ noticed a noticeably higher salt level. The inter-dialytic dietary salt intake and the intra-dialytic elimination of Na+ are the two main factors that affect Na+ balance in chronic hemodialysis patients. Serum sodium levels in dialysis patients seem to have a certain fixed point. A negative sodium balance would cause changes in blood pressure, and net sodium transfer from serum to dialysate is a possibility.^15,16

In the present investigation, post-dialysis chlorine was statistically significantly lower than pre-dialysis chloride (p 0.001). According to Kirschbaum B et al.'s study¹⁷, the mean serum chloride levels (Mean-103) of post-HD patients were lower than those of pre-HD patients (Mean-103). Following hemodialysis, sodium increased, and chloride decreased in the study by Correa S. et al⁵. After hemodialysis, Liborio et al¹⁸attempted to correct the unmeasured anions produced unchanged chloride. The patients in their study had hyperchloremia, hyperphosphatemia, and excessive unmeasured anions, which caused acidosis. Hypoalbuminemia has an alkalinizing impact.

In the present study, we found reduced levels of calcium and magnesium following dialysis. Calcium (2.6±0.8, 2.3±0.4, p<0.001), magnesium (0.7±0.4, 0.5±0.2, p<0.05). These findings are in accordance with a study done by Ahmed fathy¹⁹, where they also found a reduction in serum calcium and magnesium following dialysis. Calcium (2.6±0.8, 2.3±0.4, p <0.05), magnesium (0.7±0.5, 0.5±0.3, p <0.05). The bicarbonate levels were increased in our study, following dialysis (22.1±4, 25.4±3.9, p <00.001). Similar findings were noticed in a study by Ahmed fathy¹⁹ (22.1±5, 25.5±4.2, p <0.001). Wu et al²⁰ used alterations in cellular or interstitial fluid composition to explain extended QT dispersion in dialysis patients, which could also be responsible for greater ventricular repolarization in hemodialysis patients. Important elements for maintaining normal cellular excitability, impulse propagation, and regular ventricular recovery in the myocardium include potassium, calcium, magnesium, and metabolic acidosis. This is consistent with our research, which found that hemodialysis significantly altered the levels of bicarbonate, sodium, potassium, calcium, and magnesium in the serum. These findings concur with those of Lorincz et al²¹.

Serum urea level was reduced following dialysis (130.7±29, 47.4±12.8, p <0.001) and serum creatinine level were increased following dialysis (7±1.1, 9.6±4.1, p <0.05). This is in accordance with a study done by Ahmed fathy et al¹⁹. Urea ((131.2±30, 47.6±13.2, p <0.001) and creatinine (7±1.3, 9.6±4.3, p <0.05). Kirschbaum¹⁷ who found changes in serum urea, creatinine, clearance, bicarbonate and serum potassium level with hemodialysis and stated that; serum creatinine changes are widely used to assess the efficacy of dialysis.In the immediate posthemodialysis phase, we observed a statistically significant extension of the QRS duration, an increase in the QRS and P-wave amplitudes in lead 2, and an increase in the sum of the QRS durations and amplitudes. The electrical impulses that originate in the heart travel all around the body, becoming less intense in direct proportion to the distribution of body fluids. When dialysis patients have peripheral edema or when patients have peripheral edema for other reasons, these electrical potentials decrease even more.²²

Further research is warranted since a decreased potassium level can contribute to prolonged QRS duration by slowing down cardiac conduction. In light of this, hypokalemia which is frequently overlooked may prolong the QRS length in patients who have peripheral edema for other reasons by having a synergistic or cumulative effect. Furthermore, dialysis lowers blood potassium levels, and this alteration in the body's electrical environment may be the real cause of dialysis patients' prolonged QRS length after hemodialysis²³. Our study's findings about decreased T-wave amplitudes during hemodialysis could be the result of lower blood potassium levels. T-wave amplitudes are known to decrease as blood potassium levels drop.Hemodialysis patients should be aware of the increase in the total of the amplitudes of V1S + V5R after fluid withdrawal. These findings imply that hemodialysis has a significant role in the evaluation of the left ventricular hypertrophy criteria¹⁹⁴.

In the present study, hemodialysis significantly reduced potassium, magnesium, calcium, urea, and creatinine levels, while sodium and bicarbonate levels increased. ECG changes included a decrease in T-wave amplitude, QT interval, PR interval, and RR interval, with an increase in QRS amplitude, QT dispersion, and V1S+V5R sum. Hemodialysis significantly alters electrolyte levels and induces ECG changes, highlighting the need for continuous cardiac monitoring in CKD patients undergoing dialysis. As cardio-respiratory failure is a leading cause of mortality in CKD, monitoring these changes can aid in better diagnosis and management.

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