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Three Part Question

In [adults (>16 years) presenting to the emergency department with hyperkalaemia] is the [12-lead ECG] [sensitive and specific enough to rule in/out the condition]?

Clinical Scenario

A 50- year old woman presents to the Emergency Department with a letter from her GP stating that her serum potassium level is 5.6 mmol/L. A repeat blood test confirms hyperkalaemia, with a serum potassium of 5.8 mmol/L. You immediately order a 12-lead ECG, then wonder if the findings are going to alter your management plan.

Search Strategy

Cochrane Library for Systematic Reviews: May 2011
MEDLINE using OVID interface: 1948 to June week 2
EMBASE: 1980 to 2011 week 25
Cumulative Index to Nursing and Allied Health Literature (CINAHL) Plus: 1947 to June 26th 2011


COCHRANE: hyperkalaemia, hyperkalemia, hyperkal*, hyperpotass*, potassium and hyperpotassaemia

MEDLINE: [exp Potassium/ OR exp Hyperkalemia/ OR hyperkalaemia.mp/ OR high potassium.mp/ OR hyperkal$.mp/ OR hyperpotass$.mp] AND [ECG.mp. OR exp Electrocardiography/ OR EKG.mp/ OR electrocardiogram.mp/ OR Electrokardiogram.mp/ OR Electrocardio$.mp/ OR Electrokardio$.mp/ OR ECG$.mp/ OR EKG$.mp] Limit to (english language and humans and "all adult (19 plus years)")

EMBASE:[exp Potassium/ OR exp Hyperkalemia/ OR hyperkalaemia.mp/ OR high potassium.mp/ OR hyperkal$.mp/ OR hyperpotass$.mp] AND [ECG.mp/ OR exp Electrocardiography/ OR EKG.mp/ OR electrocardiogram.mp/ OR Electrokardiogram.mp/ OR Electrocardio$.mp/ OR Electrokardio$.mp/ OR ECG$.mp/ OR EKG$.mp] Limit to (human and english language and adult <18 to 64 years>)

CINAHL: [Hyperkalaemia/ OR Hyperkalemia/ OR Hyperkal*/ OR High potassium /OR Potassium/ OR Hyperpotass*] AND [ECG/ OR electrocardiography/ OR EKG/ OR Electrokardiogram/ OR electrocardiogram/ OR ECG*/ OR EKG*/ OR Electrocardio*/ OR Electrokardio*] Limit to (english language and humans)

Search Outcome

COCHRANE: 51 papers found, none of which were relevant.
MEDLINE: 923 papers found, of which 6 were relevant and are shown in the table below.
EMBASE: 963 papers found, 4 of which were relevant but were duplicates of the MEDLINE papers. CINAHL:90 papers found, 3 of which were relevant, but were duplicates of the MEDLINE papers.
Therefore no additional studies were identified using EMBASE and CINAHL.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Aslam S, Friedman EA, Ifudu O 2002 New York, USA.	74 consecutively selected stable outpatients with ESRD receiving HD.	Prospective blinded cohort.	T wave amplitude (mm)	K+ < 4.4 mEq/l : 4.9± 2.4.	Sample size estimates were not performed and the sample size was small. Specific to ESRD patients receiving HD.
				K+ 4.4 - 4.9 mEq/l : 4.9± 3.2.
				K+ 4.9 - 5.2 mEq/l : 5.7± 3.8.
				K+ > 5.2 mEq/l : 7.3± 4.9,
				P= 0.1
			T wave to R wave ratio	P = 0.14
Wren KD, Slovis CM, Slovis BS 1991 New York, USA.	220 consecutive patients admitted to the hospital from the ED with renal failure or hyperkalaemia. 87 were hyperkalaemic.	Retrospective blinded cohort.	Potassium >5.0 mmol/l : ECG sensitivity.	0.43 and 0.34.	Sample size estimates not performed. High prevalence of left ventricular hypertrophy and bundle branch block in study population may have affected results.
			Best positive predictive value.	0.65
			Potassium >5.0 mmol/l : ECG specificity	0.85 and 0.86.
			Best negative predictive value.	0.69
			Potassium >6.5 mmol/l : ECG sensitivity.	0.62 and 0.55
Nemati E, Taheri S 2010 Iran	80 stable patients with ESRD receiving HD selected from 4 out-patient HD centres.	Cross-sectional study	Relationship of ECG parameters to quartiles of serum K+ conc. (<4.4; 4.4-4.9; 4.9-5.2; >5.2)	P > 0.05	Specific to ESRD patients receiving HD. Sample size estimates not performed. Not all patients accounted for (80 included in study but results for only 78)
			Relationship of ECG parameters to serum K+ conc. divided into 2 groups (> 5.2 and ≤ 5.2)	T wave duration : P = 0.008. Decreased T wave duration associated with hyperkalaemia : P = 0.009
Montague BT, Ouellette JR, Buller GK 2008 Connecticut, USA.	90 inpatients with a serum/plasma potassium concentration ≥6.0 mmol/L.	Retrospective review.	Cardiologist : P wave amplitude changes	0 patients	Sample size estimates not performed. Potential for bias as reviewers were not blinded to the diagnosis of hyperkalaemia.
			New QRS prolongation	6 patients
			T wave findings	24 patients: 21 non-specific, 3 peaked
			Reviewers: ECG changes	47 patients. Sensitivity 0.52
			Peaked and symmetrical T waves.	16 patients. Sensitivity 0.18
			Correlation between presence of T waves by cardiologist and serum K+ conc.	Not significant. P = 0.21
			Correlation between Increasing conc. of serum K+ and ECG changes	Positive association. P = 0.0038
Acker CG, Johnson JP, Palevsky PM, Greenberg A 1988 Pittsburgh, USA.	127 (for observation phase) and 115 (for notification phase)consecutive inpatients with a serum K+ ≥ 6.0 mmol/l. 85 (observation) and 76 (notification) ECG's obtained.	Prospective study	K+ > 6.0mmol/L : ECG changes	1st degree atrioventricular block: 1%. Junctional rythm: 4%. Widened QRS: 8%. Peaked T waves: 36%.	Sample size estimates and P values not calculated. No information detailing how ECG changes were interpreted and whether it was blinded or not.
			ECG suggestive of hyperkalaemia.	46%.
			K+ > 6.8 mmol/L : ECG changes	10/18 (55%)
			K+ < 6.8 mmol/L : ECG changes	23/54 (43%)
			ECG changes in comparison to severity of hyperkalaemia	No relation.
Sanchez JLC, Camarero ARA, Perez MC, Sota MAM, et al. 2007 Spain	34 patients with ESRD receiving HD. 10 patients hyperkalaemic (serum potassium ≥ 5.5mEq/l).	Descriptive, cross-sectional prospective study.	T wave elevation pre-HD (mm)	Range: 3- 13. Mean: 6.2.	Sample size estimates not performed and number of hyperkalaemic patients very small. No statistical analysis of results performed. Many ECG parameters measured (eg PR- interval) but not followed up. Data difficult to interpret. Range and means calculated myself. Only patients with ESRD included. Includes non-hyperkalaemic patients but no attempt made to compare the two groups.
			T wave elevation post-HD (mm)	Range: 0- 8. Mean: 1.3.

Comment(s)

It appears that the ECG is more specific than sensitive in the diagnosis of hyperkalaemia and therefore may be of benefit in ruling in, rather than ruling out, the condition. However, there is contradictory evidence as to whether the frequency of ECG changes increases with increasing serum K+ concentration, and when ECG changes are detected they are often non-specific. It is also unclear which ECG parameter is the most sensitive as the different studies choose to evaluate some ECG parameters and ignore others, making it difficult to standardise results. It is important to note that many of the sample sizes used in these studies are small and the majority of patients studied are those with ESRD receiving HD. This is not representative of the emergency department population and so it may be inappropriate to generalise the findings.

Clinical Bottom Line

A positive ECG finding should not be ignored and can help rule in the diagnosis of hyperkalaemia. A negative result does not rule out the possibility of hyperkalaemia. Further research is required into the use of ECG in hyperkalaemic patients in the ED.

References

1. Aslam S, Friedman EA, Ifudu O Electrocardiography is unreliable in detecting potentially lethal hyperkalaemia in haemodialysis patients European Renal Association - European Dialysis and Transplant Association 2002; 17: 1639 - 1642
2. Wren KD, Slovis CM, Slovis BS The ability of physicians to predict hyperkalemia from the ECG. Annals of Emergency Medicine 1991; 20; 1229 - 1232
3. Nemati E, Taheri S Electrocardiographic manifestations of hyperkalemia in hemodialysis patients Saudi Center for Organ Transplantation 2010; 21(3): 471 - 477
4. Montague BT, Ouellette JR, Buller GK Retrospective review of the frequency of ECG changes in hyperkalemia. American Society of Nephrology 2008; 2: 324 - 330
5. Acker CG, Johnson JP, Palevsky PM, Greenberg A Hyperkalemia in hospitalized patients. Archives of Internal Medicine 1988; 158: 917- 924
6. Sanchez JLC, Camarero ARA, Perez MC, Sota MAM, et al. Hyperkalaemia and haemodialysis patients: electrocardiographic changes. Journal of Renal Care. 2007; 33 (3): 124 - 129