Hyperkalemia

Hyperkalemia Definition

Hyperkalemia is referred to as the condition, where the electrolyte “potassium” concentration gets elevated in the blood (hyper means- high, kalium- potassium, emia- in blood).

Benefits of potassium

• Potassium is the most abundant cation inside the cell that is essential for several physiological processes.
• Potassium is very essential for the normal functioning of the heart, muscles and nerves.
• It controls the activity of smooth muscles, including muscles of the heart, digestive tract and extremities.
• It helps in the normal transmission of electrical signals in the nervous system of the body.
• It maintains the normal electrical rhythm of heart
• The intracellular is to extracellular potassium ratio is essential in the determination of cellular membrane potential. Small changes in the extracellular potassium level may profoundly affect the function of the neuromuscular and cardiovascular systems.

Nearly 95%of the total potassium present in the body is present within the cells, and the remaining amount is found in the blood. This concentration gradient is regulated by the Na+/K+ pump. Hyperkalemia is a life-threatening illness, which may be difficult to diagnose due to a paucity of distinctive signs and symptoms.

The physician must be quick in diagnosing hyperkalemia in patients who are at risk. Both hyperkalemia and hypokalemia can lead to abnormal heart rhythms. Often, severe hyperkalemia becomes a medical emergency, as death mostly occurs due to arrhythmia.

• Normal serum potassium level- 3.5 – 5.0 mEq/L.
• Mild hyperkalemia- 5.1 to 6.0 mEq/L
• Moderate hyperkalemia- 6.1 to 7 mEq/L
• Severe hyperkalemia- above 7 mEq/L

Hyperkalemia Epidemiology

Frequency

8% of the total hospitalized patients are diagnosed as having hyperkalemia.

Sex

The male: female ratio is 1:1, i.e., both the genders are equally affected.

Mortality/Morbidity

The primary cause of morbidity and death is potassium’s effect on cardiac function. Severe hyperkalemia, if not treated on time, causes a high mortality rate of 67%.

Hyperkalemia Symptoms

Often there are no symptoms with hyperkalemia. Symptoms that may occur include:

• Nausea
• Palpitations
• Slow, weak, or irregular heartbeat
• Heart stoppage (in severe cases)
• Fatigue
• Difficulty breathing
• Tingling and numbness
• Muscle paralysis (hyperkalemia suppresses the muscle’s electrical activity)

Hyperkalemia Causes

Ineffective elimination:

Renal insufficiency

Medication interfering with urinary excretion:

• NSAIDs such as naproxen, ibuprofen or celecoxib
• Potassium-sparing diuretics (e.g. spironolactone and amiloride)
• ACE inhibitors and angiotensin receptor blockers
• The antibiotic trimethoprim
• The calcineurin inhibitor immunosuppressants- tacrolimus and ciclosporin
• The antiparasitic drug – pentamidine

Mineralocorticoid deficiency or resistance, such as:

• Addison’s disease
• Few forms of congenital adrenal hyperplasia
• Aldosterone deficiency
• Renal tubular acidosis -Type IV (resistance of renal tubules to aldosterone)

Gordon’s syndrome (type II -pseudohypoaldosteronism)

• This is familial hypertension along with hyperkalemia, which is a rare genetic disorder occurring due to defective modulators of salt transporters, such as the thiazide-sensitive Na-Cl cotransporter.

Excessive intake

• Excess intake by salt-substitute, dietary supplements containing potassium, or potassium chloride (KCl) infusion. In a normal functioning kidney where the elimination process is intact, hyperkalemia due to potassium intake would occur only in cases of oral doses of several hundred mEq of KCl, or large infusions of KCl

Excessive release from cells

• Rhabdomyolysis, burns or other rapid tissue necrosis causes, including tumor lysis syndrome
• Shifts/transport out of cells due to acidosis, beta-blocker therapy, digoxin overdose, low insulin levels, or succinylcholine (paralyzing agent)
• Massive hemolysis or massive blood transfusion

Lethal injection:

• In the United States, hyperkalemia is brought intentionally as the lethal injection. A lethal dose of potassium chloride is the third and eventual of the total three drugs administered; it is certainly the one causing death.

Diet

Diet high in potassium like bananas, tomatoes, oranges, salt substitutes, high protein diets, potassium supplements

Pseudo hyperkalemia

It occurs due to excessive potassium leakage from the cells while or after blood is drawn, i.e., hemolysis during venipuncture. This may be due to collection needle having very fine gauge or excessive vacuum of the blood draw. It is not a biological abnormality; instead, it is a laboratory artifact. Pseudo hyperkalemia is also due to excessive tourniquet time; delay in blood specimen processing; fist clenching while phlebotomy, thereby making the muscle’s potassium efflux into the blood. This is also seen in patient’s specimen containing abnormal platelet values of greater than 500,000/mm³, erythrocytes (hematocrit >55 %), leukocytes > 70 000/mm3.

Hyperkalemia Pathophysiology

The potassium elimination from the kidneys through the glomeruli is a passive process, while its reabsorption in the ascending limb of Henle’s loop and proximal tubule is an active process. Also, there is active potassium excretion in the collecting duct and distal tubule. This active process is controlled by aldosterone.

Hyperkalemia develops due to excessive production of potassium, due to oral consumption or tissue breakdown or ineffective potassium elimination. Ineffective potassium elimination may be hormonal due to aldosterone deficiency, or may be caused by the pathology of renal parenchyma, which impair the excretion.

Increased potassium levels in the extracellular region causes depolarization of the cell’s membrane potential, resulting in opening of voltage-gated sodium channels that is not enough for generating action potential. These opened sodium channels gets inactivated after some time, thereby becoming refractory that increases the action potential threshold. Hence, cardiac, neuromuscular and gastrointestinal system gets impaired. Among these, the most severe is the cardiac conduction impairment resulting in asystole or ventricular fibrillation.

During vigorous exercise, potassium gets released from the muscles, and the level of potassium in blood rises to a level that can prove to be dangerous at rest. It is believed that the high adrenaline and noradrenaline levels possess a protective effect on the cardiac electrophysiology. Patients with hereditary hyperkalemic periodic paralysis have sensitivity of muscular symptoms, which are associated with transient potassium level elevation. Exercise or fasting precipitates episodes of muscle spasm and muscle weakness.

Hyperkalemia Diagnosis

Laboratory Studies:

Potassium level

• The relationship between the potassium level in serum and symptoms is not consistent. The rapid change in the level of potassium influences the symptoms being observed at various potassium levels.

BUN and creatinine level

• For evaluating the renal status

Glucose level

• In diabetes mellitus patients

Calcium level

• If patient is having renal failure, calcium level evaluation is very essential (because hypocalcaemia can exacerbate disturbances of cardiac rhythm)

Arterial or venous blood gas

• If suspecting acidosis, blood gas analysis is performed.

Digoxin level

• If patient is on a digitalis medication

Urinalysis

• If renal insufficiency signs are noted without an existing known cause (to rule out glomerulonephritis)

Cortisol and aldosterone levels

• To rule out mineralocorticoid deficiency, while eliminating other causes

Trans-tubular potassium gradient

• It may sometimes assist in distinguishing the hyperkalemia cause

Renal ultrasound:

• To rule out renal failure

B. Continuous cardiac monitoring

Indicated for evaluating the rhythm disturbances

ECG (EKG)

• ECG is instrumental and essential in diagnosing hyperkalemia in the clinical setting. ECG changes have a sequential progression of effects that roughly correlate with the serum potassium level. In general, ECG findings correlate with the potassium level, but life-threatening arrhythmias can be caused without prior warning at any level of hyperkalemia.

ECG findings seen are as follows:

• Peaked T waves, ST-segment depression shortened QT interval.
• Bundle-branch blocks are seen that causes a widening of the QRS complex, decreased P wave amplitude and increased PR interval.
• If hyperkalemia is not treated, eventually P wave disappears, and morphology of QRS widens for resembling a sine wave. After this, asystole or ventricular fibrillation begins.
• Heart block occurs, as the electrical impulse through the heart gets slower or stops
• Slower than normal heartbeat (bradycardia).
• Membrane depolarization and inactivation of sodium channels.

Your doctor should evaluate your serum potassium; hence, should perform kidney blood tests regularly if:

• You are on ACE inhibitors, spironolactone, angiotensin receptor blockers, triamterene (Dyrenium) and amiloride (Midamor).
• You are a kidney disease patient of chronic duration
• You use salt substitutes
• You are prescribed additional potassium.

ECG findings conclusion:

• Mild hyperkalemia- has limited effect on the heart.
• Moderate hyperkalemia– produce EKG changes like reduction of P wave size and peaked T waves.
• Severe hyperkalemia– widening of the QRS complex is seen due to inactivation of the sodium channels that make the conduction of electrical wave around the heart, along with ECG complex evolving to a sinusoidal shape. It suppresses the heart’s electrical activity, and may make the heart stop beating.

Things to do when diagnosed as hyperkalemia

1. Follow the doctor’s instructions to lower your serum potassium level. If severely elevated, medications to lower the levels to a safe range may be prescribed.
2. If you are on heart medication, and have chronic elevated serum potassium level, it’s advisable to eat a low potassium diet.
3. Take the drugs/medications as directed.
4. Conduct the laboratory blood tests, as recommended by the doctor.
5. Avoid alcohol and caffeine, as there are chances of electrolyte disturbances.

Hyperkalemia Differential diagnosis

• Hypocalcaemia

Hyperkalemia Treatment

If the potassium level is extremely high (>6.5 mEq/L), or if changes in ECG are seen, like arrhythmias, emergency mandatory lowering of potassium level is necessary. The choice of measures depends on the cause and degree of hyperkalemia along with other aspects contributing to the patient’s condition.

Emergency treatment includes:

• Calcium (IV) to treat the muscle and heart problems caused due to high potassium levels.
• Glucose and insulin (IV) is given to lower the potassium levels to correct the cause
• Kidney dialysis, if kidney functioning is poor
• Medications to remove potassium from the intestines prior to getting absorbed
• Diuretics (Water pills) to decrease the total potassium amount
• Sodium bicarbonate, if the cause for hyperkalemia is acidosis

Medications:

• Loop Diuretics (water pills): This decreases the blood potassium levels, by enabling you to urinate out the extra fluid. When you lose fluid through the kidneys, it is certain that you will lose potassium too.
• Calcium gluconate or calcium chloride increases the threshold potential through a mechanism (myocardial excitability) that restores the normal gradient between threshold potential and resting membrane potential that is abnormally elevated in hyperkalemia. One ampule of CaCl2 (calcium chloride) has thrice the calcium than in calcium gluconate. Onset of action is less than 5 minutes, and persists for about 30-60 minutes. Doses should be modified with constant monitoring of ECG changes during drug administration, and repeat dose may be needed, if ECG changes do not become normal within 3-5 minutes.
• Sodium polystyrene sulfonate. – For instance, Kayexalate lowers the serum potassium levels; it binds along with the potassium inside your gut or stomach. It can be taken orally, or by enema. There are chances that this medicine may make you constipated; hence, take a special laxative (called sorbitol) to get relief from constipation. However, as small risk of colon necrosis persists with the usage of these drugs.
• Hemodialysis – In case of severely elevated blood potassium level in patients with kidney failure, the physician or nephrologist may recommend dialysis treatment for rapid removal of potassium.
• Insulin/Bicarbonate/Calcium – These are given usually intravenously, for driving the potassium electrolyte from the serum, back into the cells. This is usually administered with another potassium lowering therapy.
• Furosemide (diuretic) may be used for promoting excretion of potassium in the urine.

Diet modification:

• Limit or avoid the use of avocados, winter squash, asparagus, potatoes, tomatoes or tomato sauce, cooked spinach and pumpkin
• Limit or avoid the use of oranges and orange juice, Kiwis, honeydew, cantaloupe, bananas, nectarines raisins or other dried fruit, prunes, and nectarines
• If prescribed a low-salt diet, avoid salt substitutes.

Hyperkalemia Complications

• Arrhythmias
• Changes in nerve and muscle (neuromuscular control)
• Cardiac arrest

Hyperkalemia Prognosis

The outcome of hyperkalemia varies. In some people, it causes deadly complications, whereas, others tolerate it and respond well.

When to Call Your Doctor in hyperkalemia?

• Nausea interfering with your eating ability, and is unrelieved by the prescribed medication.
• Vomiting (more than 4-5 times every 24 hour period).
• Severe constipation, which is unrelieved by laxatives, and lasting 2 to 3 days.
• Palpitations (feeling your rapid heartbeats).
• Weak or absent heartbeat.
• Loss of consciousness.
• Muscle weakness, and non-improving poor appetite.

Hyperkalemia Prevention

Always follow your physician’s advice, if you are under his treatment for hyperkalemia.

• Follow the prescribed schedule always.
• Never start or stop any medicines without your doctor’s permission.
• Disclose details of any medicines, supplements or vitamins taken or currently taking.
• Reduce the amount of potassium in diet.
• Addition of diuretic like furosemide or oral bicarbonate.
• Sodium polystyrene sulfonate and sorbital (Kayexalate) for maintaining low serum potassium levels.

References

http://en.wikipedia.org/wiki/Hyperkalemia

http://www.medicinenet.com/hyperkalemia/page2.htm

http://www.nlm.nih.gov/medlineplus/ency/article/001179.htm

http://emedicine.medscape.com/article/766479-overview

http://www.mayoclinic.com/health/hyperkalemia/MY00940

http://www.umm.edu/altmed/articles/hyperkalemia-000085.htm

http://health.nytimes.com/health/guides/disease/hyperkalemia/overview.html

http://www.webmd.com/a-to-z-guides/hyperkalemia

http://www.bami.us/Diet/Hyperkalemia.html

http://www.chemocare.com/managing/hyperkalemia-high-potassium.asp

http://www.drugs.com/condition/hyperkalemia.html

http://www.patient.co.uk/leaflets/hyperkalemia.htm