Home About us Current issue Ahead of Print Back issues Submission Instructions Advertise Contact Login   

Search Article 
Advanced search 
Saudi Journal of Kidney Diseases and Transplantation
Users online: 1443 Home Bookmark this page Print this page Email this page Small font sizeDefault font size Increase font size 

ORIGINAL ARTICLE Table of Contents   
Year : 2008  |  Volume : 19  |  Issue : 1  |  Page : 47-53
Electrocardiography and Serum Potassium before and after Hemodialysis Sessions

1 Department of Medicine, College of Medicine, King Saud University, Saudi Arabia
2 Division of Nephrology and Division of Cardiology, College of Medicine, King Saud University, Saudi Arabia

Click here for correspondence address and email


This study was undertaken to assess potassium level and electrocardiographic (ECG) changes post hemodialysis and whether fall in potassium level during dialysis may potentiate cardiac arrythemia. We studied 21 chronic hemodialysis (HD) patients who had their serum electrolytes measured before and immediately after dialysis session, and ECG performed at the same time. The patients included 14 females and 7 males with a mean age of 53.1±15.6 years and range from 26 to 81 years; 9 (43%) patients were diabetics. All the patients had been on dialysis for a minimum of 6 months each Pre-HD serum potassium levels had no correlation with any ECG parameters except a negative correlation with the T wave amplitude r=-0.5, p=0.021. ECG parameters significantly changed post­HD; the T wave amplitude decreased, and the R wave amplitude increased. A comparatively higher R wave significantly decreased the T to R wave ratio post dialysis. The QRS duration and QTc interval also increased significantly. The patients with post-HD serum potassium of < 3.5 -in comparison to those with levels >3.5 mmol/L -had a higher R wave amplitude and a significantly less T to R wave ratio (11.8±9.7 vs 6.4±5.1, p=0.045 and 0.4±0.38 vs 1.0±0.97, p=0.049, respectively. In patients with serum potassium decrement of > 2.0 mmol/L, the T to R wave ratio decreased significantly, 0.32±0.21 vs 0.85 ±0.26, p=0.023; The T wave amplitude decreased more than the rise in R wave. Multiple regression analysis did not reveal any relationship of pre or post HD ECG changes and serum potassium, serum calcium or net change in serum potassium post-HD. We conclude that post-HD serum potassium decrement results in a decrease in T to R wave ratio on ECG; this change may have an arrhythmogenic potential.

Keywords: Hemodialysis, Hyperkalemia, hypokalemia, electrocardiography.

How to cite this article:
Tarif N, Yamani H, Bakhsh AJ, Al-Wakeel JS, Sulaimani F, Memon NA, Al Suwaida AK. Electrocardiography and Serum Potassium before and after Hemodialysis Sessions. Saudi J Kidney Dis Transpl 2008;19:47-53

How to cite this URL:
Tarif N, Yamani H, Bakhsh AJ, Al-Wakeel JS, Sulaimani F, Memon NA, Al Suwaida AK. Electrocardiography and Serum Potassium before and after Hemodialysis Sessions. Saudi J Kidney Dis Transpl [serial online] 2008 [cited 2021 Jun 24];19:47-53. Available from: https://www.sjkdt.org/text.asp?2008/19/1/47/37432

   Introduction Top

Hyperkalemia is common complication in end-stage renal disease (ESRD) patients. [1] In fact, the pre-Hemodialysis (HD) potassium levels are usually > 5.0 mmol/L and 19% of patients have a serum potassium levels of > 6 mmol/L. [2] Many studies have shown that the presence of hyperkalemia does not corre­late with the presence of electrocardio­graphic (ECG) changes.[1],[2],[3],[4],[5],[6] Higher potassium levels may be tolerated by the ESRD patients without major consequences or even electrocardiographic changes. [2],[3],[7] However, there are still no recommendations for the optimal values of serum potassium for ESRD patients on dialysis. Moreover, cardiovascular morta­lity accounts for 50% of deaths in hemo­dialysis patients, including a higher incidence of cardiac arrest, sudden death and arrhythmias. [8]

In this study we evaluated the potassium levels and ECG both pre and post dialysis to observe whether changes in serum potassium levels influence ECG recordings post dialysis that may suggest a state of arrhythmo­genecity.

   Subjects and Methods Top

We studied 21 chronic HD patients of various etiologies who were receiving hemo­dialysis (HD) for more than > 6 months (range 1 year to 15 years). All patients were dialyzed at a university hemodialysis unit using Fresenius Hemodialysis machine 4008H (Fresenius Corporation, Germany) and Vitamin E coated cuprophane dialyzers (Terumo, Japan), bicarbonate dialysate. The duration of dialysis was 3.5 to 4 hours and a blood flow of >300 ml/min. Dialysate potassium concentration of 2.0 mmol/L was used for patients with pre dialysis potassium level of < 6.0 mmol/L, while 1.0 mmol/L potassium dialysate concentration was used for patients with potassium levels > 6.0 mmol/L. In occasional patients with dietary indis­cretions and potassium levels reaching >7.0 mmol/L we used the dialysate without pota­ssium. All the patients were over 18 years age and none were on any medications that could interfere with cardiac conduction.

Serum levels of potassium, sodium, urea, creatinine, calcium, phosphorus were obtained immediately before the dialysis session. Serum level of potassium, sodium, urea and creatinine were also obtained immediately post hemodialysis according to dialysis out­come quality initiative (DOQI) guidelines. Laboratory measurements were performed within one hour of sample collection at our hospital laboratory using automated analyzers. A simultaneous 12 lead ECG was obtained immediately pre and post HD. All ECGs and echocardiographs were reviewed by one of the authors (HY) who is a consultant cardio­logist. ECG was interpreted for the ampli­tudes of T wave and R wave in the chest leads, duration of QRS, corrected QT (QTc), and presence of "U" waves. The presence of left ventricular hypertrophy (LVH) was docu­mented by echocardiography. We followed up the patients for 18 months to detect arrhythmias or sudden cardiac death.

   Statistical Analysis Top

All statistical analysis was performed using SPSS (Statistical program for social sciences version 10.0.7, 2000, SPSS Inc, USA). Des­criptive analysis is given as mean ± standard deviation. Student "t" test was used to compare between individual means. Multiple regression analysis was used to assess the independent association of T and R wave amplitude, and T to R wave ratio with all the other variables. Bi-variant analysis with Pearson correlation was used for assessment of relationships between variables. T wave to R wave ratio for both pre and post dialysis ECG was correlated with the concentration and magnitude of change of serum potassium. P <0.05 was considered as significant.

   Results Top

The 21 study patients comprised 14 females and 7 males with a mean age of 53.1±15.6 years (range from 26-81 years). Mean duration of HD was 48.6±60.8 months (6-180 months). Nine (43%) patients were diabetic, while the rest had various other diagnoses (adult cystic disease = 1, hypertension = 5, Glomerulo­nephritis = 4, primary hyperoxaluria = 1, interstitial nephritis = 1). None of the patients had a history of arrhythmias prior to the ECG recordings, although two patients, both dia­betics, had history of coronary artery disease.

The mean serum potassium levels pre dialysis and post dialysis were respectively 5.20±0.88 mmol/L (range: 3.8-6.9mmol/L) and 3.31±0.77 mmol/L (range: 2.0-5.2 mmol/L). However, this difference did not reach statistical significance, [Table - 1]. Pre-HD serum potassium levels had no influence on R wave amplitude, or T to R wave ratio, but only a significant negative correlation with T wave amplitude, r=-0.5, p=0.021, [Figure - 1].

Seven patients had serum potassium level > 5.5, but this was not significantly associated with any pre dialysis ECG parameters such as T or R wave amplitude, QRS or QTc duration and T/R ratio. Even in the patient with serum potassium of 6.9 mmol/L, the T wave ampli­tude was only 2.5 mm. Only two patients had peaked T waves in chest leads and in these, the pre dialysis serum potassium levels were only 3.9 and 4 mmol/L, respectively.

ECG parameters significantly changed post­HD, [Table - 1]. The T wave amplitude de­creased, and the R wave amplitude increased at the same time. A comparatively higher R wave significantly decreased the T to R wave ratio post dialysis. The QRS duration and QTc interval also increased significantly. Using Pearson Bi-variant correlation we found that serum potassium post-HD had no significant influence on the T or R wave am­plitudes or T to R wave ratio) (r=-0.14, p=0.5, r=0.18, p=0.44, r=0.23, p=0.35 respectively). Similarly net change in serum potassium levels did not correlate with change in T wave amplitude post-HD (r=0.14, p=0.55).

The patients with post-HD serum potassium of < 3.5 -in comparison to those with >3.5 mmol/L- had a higher R wave amplitude and thus a significantly less T to R wave ratio (11.8±9.7 vs 6.4±5.1 p=0.045 and 0.4±0.38 vs 1.0±0.97, p=0.049, respectively). The mean decrement in serum potassium following dialysis was 1.89±0.96 mmol/L (range: 0.60­4.40). In patients with serum Potassium decrement of > 2.0 mmol/L (8 patients), T to R wave ratio decreased significantly, 0.32± 0.21 vs 0.85±0.26, p=0.023. Individually, however, the R and T waves did not change significantly. Bi-variant analysis revealed a significant negative correlation between the change of serum potassium and T wave amplitude, r=-0.59, p=0.005, suggesting that T wave amplitude decreased more than the rise in R wave, [Figure - 2].

Multiple regression analysis did not reveal any association between ECG changes (pre­or post- HD) and serum potassium, serum calcium or net change in serum potassium post-HD. Six patients developed "U" wave post-HD. These, when compared to the rest of patients, had a higher amplitude of the R wave (15.9±12.1 vs 7.3±5.4, p=0.03), however, T/R ratios in the post dialysis ECG was not significantly different (p=0.38) Post­HD, and net change in serum potassium were also not significantly different among patients with and without U waves, [Figure - 3].

ECG revealed incomplete right bundle branch block in one and complete right bundle branch block in another patient. One of the patients was discovered later to be on Amiodarone 200 mg daily for an episode of acute resolved atrial fibrillation. Excluding these patients from analysis did not change the results.

During the follow-up period of 18 months, 3 patients died; 2 because of complications of sepsis, and the third- a diabetic patient - developed ventricular arrhythmias that required a pacemaker insertion and later died of acute myocardial infarction. In this later patient, the usual serum potassium levels pre­HD were <5.5 mmol/L, and the usual serum potassium levels and post HD were in the range of 3.2- 4.0 mmol/L, however, his ECG at the time of study did not show any significant post HD change.

   Discussion Top

Our findings were consistent with cardio­vascular instability associated with changes in serum potassium. We found that the net change of serum potassium with the hemo­dialysis procedure was associated with ECG changes. A more significant decrease in T wave and T to R wave ratio was observed when serum potassium decreased > 2.0 mmol/L.

The optimal serum potassium levels in ESRD patients in preoperative evaluation is controversial. [9] A serum potassium of > 5.5 mmol/L (normal upper limit) raises concerns and frequently leads to cancellation of procedures or to asking for urgent pre­operative dialysis for patients requiring anesthesia. Hyperkalemia reduces the resting membrane potential, slows the conduction velocity and increases the rate of repolarization. [10],[11] Hypokalemia on the other hand increases the resting membrane potential, and increases the duration of action potential and refractory period, which are potentially arrhythmogenic. [12] All these changes are the hallmarks of membrane instability and cardiac arrest or ventricular fibrillation may ensue and thus this situation usually requires careful and prompt management.

In a retrospective analysis by Olson et al, 8 out of 45 chronic kidney disease (CKD) patients with serum potassium of > 6.0 mmol/ L underwent procedures requiring general anesthesia. [9] Although no adverse effects were noted, only one patient had general anesthesia and another regional block, while the rest had regional anesthesia. It should be, however, stressed that acute decrease in GFR secon­dary to complications of surgery and hemo­dynamic instability may result in further elevations in serum potassium levels. Succinylcholine used as a muscle relaxant, causes shifts of serum potassium extracellularly and thus may aggravate an already existing hyperkalemia.[13]

Serum potassium levels do not correlate well with the ECG changes especially in hemodialysis patients as also revealed in our study. Although this suggests that heart might be relatively protected from the delete­rious effects of high potassium levels, yet no consensus exists about the safe upper limit of serum potassium.[1],[2],[3],[4],[5],[6] This contrast was shown in patients with as high levels of potassium as > 9.0 mmol/L without any ECG changes. [2] In our patients, pre-HD ECG findings did not correlate with the level of hyperkalemia consistent with the previous reports except a negative correlation between serum potassium and T wave amplitude.

Removal of serum potassium during the HD procedure is dependent on the duration, type of dialyzer, blood flow and most importantly dialysate potassium concentration. [12] Four of our patients were dialyzed with dialysate K of 1.0 mmol/L and the rest with dialysate K of 2.0 mmol/L. Hypokalemia of < 3.5 mmol/ L was associated with a significant decrease in T wave amplitude and T to R wave ratio. Similarly there was a significant increase in QRS duration and QTc interval. Does all this suggest that patients have improvement in their ECG parameters or are more prone to arrhythmia in the immediate post dialysis period? Main decrease in serum potassium is noted in the first hour of hemodialysis and later takes few hours to equilibrate. [14]

Covic et al noted an increase in QTc duration post dialysis if a lower pre HD level of K was present along with greater decre­ments in serum calcium levels post-HD. [15] We did not find a significant correlation between the level or net change in serum potassium with QTc duration. This might suggest the effect of serum calcium levels as more pronounced on the QTc duration. We could not confirm this since we did not measure the post HD serum calcium.

Furthermore, serum calcium levels may have a protective effect on T wave ampli­tude as reported by Aslam et al. [1] In our patients, serum calcium did not influence the T wave amplitude; this however may be due to our smaller sample size.

We also compared the T to R wave ratio and individual amplitudes of T and R waves. These changes in T and R wave are more associated with serum potassium levels and are representative of repolarization hetero­genecity. Our results were compatible with the findings of Covic et al. [15]

In conclusion, Pre-HD serum potassium levels do not correlate with the ECG changes. Post-HD serum potassium of < 3.5 and a decrement of > 2.0 mmol/L is associated with decrease in T wave and an increase in R wave. QTc and QRS duration also prolong post hemodialysis. This all may translate into arrhythmogenic potential immediately post-HD. Further evaluations are required for the safety of routine pre-operative HD in chronic dialysis patients and milder degrees of hyperkalemia.

   Acknowledgements Top

Special thanks to Mohammed Faseeh Nauman and Firasat Nauman for their secretarial help.

   References Top

1.Aslam S, Friedman EA, Ifudu O. Electro­cardiography is unreliable in detecting potentially lethal hyperkalaemia in haemo­dialysis patients. Nephrol Dial Transplant 2002;17:1639-42.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Szerlip HM, Weiss J, Singer I. Profound hyperkalemia without electrocardiographic manifestations. Am J Kidney Dis 1986;7:4 61-5.  Back to cited text no. 2    
3.Martinez-Vea A, Bardaji A, Garcia C. Severe hyperkalaemia with minimal electrocardiographic manifestations: a report of seven cases. J Electrocardiol 1999;32:45-9.  Back to cited text no. 3    
4.Tzamaloucas AH, Avashti PS. Temporal profile of serum potassium concentration in nondiabetic and diabetic outpatients on chronic dialysis. Am J Nephrol 1987;7:101-9.  Back to cited text no. 4    
5.Papadimitrou M, Roy RR, Varkarakis M. Electrocardiographic changes and plasma potassium levels in patients on regular haemodialysis. Br Med J 1970;2:268-9.  Back to cited text no. 5    
6.Frohnert PP, Giuliani ER, Friedberg M, Johnson WJ, Tauxe WN. Statistical investigation of correlations between serum potassium levels and electrocardiographic findings in patients on intermittent hemodialysis therapy. Circulation 1970;41: 667-76.  Back to cited text no. 6  [PUBMED]  
7.Surawicz B, Chlebus H, Muzzoleni A. Hemodynamic and electrocardiographic effects of hyperpotassemia: differences in response to slow and rapid increases in concentration of plasma K. Am Heart J 1967;73:647-66.  Back to cited text no. 7    
8.Bleyer AJ, Russell GB, Satko SG. Sudden and cardiac death rates in hemodialysis patients. Kidney Int 1999;55:1553-9.  Back to cited text no. 8  [PUBMED]  [FULLTEXT]
9.Olson RP, Schow AJ, McCann R, Lubarsky DA, Gan TJ. Absence of adverse outcomes in hyperkalemic patients undergoing vascular access surgery. Can J Anesth 2003;50: 553-7.  Back to cited text no. 9  [PUBMED]  [FULLTEXT]
10.Fisch C. Relation of electrolyte disturbances to cardiac arrhythmia. Circulation 1973; 47:408-19.  Back to cited text no. 10  [PUBMED]  
11.Ettinger PO, Regan TS, Olderwurtel HA. Hyperkalemia cardiac conduction and the electrocardiogram: Overview. Am Heart J 1974;88:360-71.  Back to cited text no. 11    
12.Webster A, Brady W, Morris F. Recognizing signs of danger: ECG changes resulting from an abnormal serum potassium concentration. Emerg Med J 2002;19:74-7.  Back to cited text no. 12  [PUBMED]  [FULLTEXT]
13.Markewitz BA, Elstad MR. Succinylcholine­induced hyperkalemia following prolonged pharmacologic neuromuscular blockade. Chest 1997;111:248-50.  Back to cited text no. 13  [PUBMED]  [FULLTEXT]
14.Blumberg A, Roser HW, Zehnder C, Muller-Brand J. Plasma potassium in terminal renal failure during and after hemodialysis; Relationship with dialytic potassium removal and total body potassium. Nephrol Dial Transplant 1997; 12:1629-34.  Back to cited text no. 14    
15.Covic A, Diaconita M, Gusbeth-Tatomir B, et al. Hemodialysis increases QTc interval but not QTc dispersion in ESRD patiens with out manifest cardiac disease. Nephrol Dial Transplant 2002;17:2170-7.  Back to cited text no. 15    

Correspondence Address:
Nauman Tarif
17-B, Fort Villas, New Iqbal Park, Lahore cantt, Pakistan

Login to access the Email id

PMID: 18087122

Rights and Permissions


  [Figure - 1], [Figure - 2], [Figure - 3]

  [Table - 1]

This article has been cited by
1 Preparation for surgery: Optimal time for blood collection following haemodialysis
Ko, N. and Stewart, G. and Li, F. and Gallagher, M. and Davidson, F.
Renal Society of Australasia Journal. 2011; 7(3): 116-120
2 Hyperkalemia as a medical emergency in patients with esrd in hemodialysis
Ahmad, Z.
Pakistan Journal of Medical Sciences. 2010; 26(1): 117-122


    Similar in PUBMED
    Search Pubmed for
    Search in Google Scholar for
  Related articles
    Email Alert *
    Add to My List *
* Registration required (free)  

    Subjects and Methods
    Statistical Analysis
    Article Figures
    Article Tables

 Article Access Statistics
    PDF Downloaded932    
    Comments [Add]    
    Cited by others 2    

Recommend this journal