how to fix electrolyte imbalance

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Companion Handbook to the WHO Guidelines for the Programmatic Management of Drug-Resistant Tuberculosis. Geneva: World Health Organization; 2014.

Cover of Companion Handbook to the WHO Guidelines for the Programmatic Management of Drug-Resistant Tuberculosis

Companion Handbook to the WHO Guidelines for the Programmatic Management of Drug-Resistant Tuberculosis.

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Contents

ANNEX 7 Management of electrolyte disturbances³

Possible anti-TB drug causes: Cm, Km, Am, S

Possible antiretroviral treatment causes: tenofovir disoproxil fumarate (TDF) (rare)

Suggested management strategy

Monitor serum potassium, magnesium and calcium frequently in patients with vomiting/diarrhoea and patients receiving injectables.
Hypokalaemia is defined as serum potassium <3.5 mEq/l.
Severe hypokalaemia or symptomatic hypokalaemia is <2.0 mEq/l.
Hypomagnesaemia is defined as serum magnesium <1.5 mEq/l.
Hospitalization is necessary in severe cases of hypokalaemia.
Check for signs of dehydration in patients with vomiting and diarrhoea. Start oral or intravenous rehydration therapy immediately until volume status is normal.
Replete potassium and magnesium; see tables for guidance.
Hypokalaemia may be refractory if concurrent hypomagnesaemia is not also corrected.
If unable to check serum magnesium, give empiric oral replacement therapy in all cases of hypokalaemia with magnesium gluconate, 1000 mg twice daily.
Check ECG in patients with significant serum electrolyte disturbances. Drugs that prolong the QT interval should be discontinued in patients with evidence of QT interval prolongation.
Electrolyte abnormalities are reversible upon discontinuation of the injectable. Even after suspending the injectable, it may take weeks or months for this syndrome to disappear, so electrolyte replacement therapy should continue for several months after completion of the injectable phase of multidrug-resistant tuberculosis (MDR-TB) treatment.

Comments

Hypokalaemia and hypomagnesaemia are often asymptomatic.

Moderate cases may present with fatigue, myalgias, cramps, paresthesias, lower extremity weakness, behaviour or mood changes, somnolence and confusion.
Severe disturbances can lead to tetany, paralysis and life-threatening cardiac arrhythmias.

Hypokalaemia and hypomagnesaemia are common in patients receiving MDR-TB treatment. Common causes are:

Vomiting and diarrhoea.
Renal tubular toxicity from the injectable (probably more common in capreomycin than the aminoglycosides).

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Injectables can cause a syndrome of electrolyte wasting, including potassium, magnesium, calcium and bicarbonate.

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This syndrome is more common and severe in HIV coinfected patients; and hospitalization and aggressive serum electrolyte monitoring and correction may be necessary.
Formulations of oral potassium chloride vary by manufacturer and country. Slow-release versions are common in resource-limited settings. The amount of potassium is often different than the tablet size. For example, one 200 mg tablet of Slow-K contains 8 mEq of potassium.

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Oral potassium, magnesium or calcium should be administered either two hours before or four to six hours after fluoroquinolones as they can interfere with fluoroquinolone absorption.

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Oral potassium can cause nausea and vomiting. Oral magnesium can cause diarrhoea.
Dietary intake of potassium should be encouraged. Bananas, oranges, tomatoes and grapefruit juice are good sources of supplementation.
Amiloride 5 to 10 mg orally daily or spironolactone 25 mg orally daily may decrease potassium and magnesium wasting due to the injectable and may be useful in severe cases that are refractory to replacement therapy.

Potassium replacement therapy

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POTASSIUM LEVEL	DOSING	MONITORING FREQUENCY
4.0 or more	None	Monthly
3.6–4.0	None	Monthly
3.3–3.5	40 mEq orally daily	Monthly
2.9–3.2	60–80 mEq orally daily	Weekly
2.7–2.8	60 mEq orally three times a day	One to two days
2.4–2.6	80 mEq orally every eight hours	Daily
<2.4	10 mEq/hr IV and 80 mEq orally every six to eight hours	One hour after infusion, every six hours with IV replacement

: Note: The normal preparation of a potassium chloride infusion is 40 mEq in 200 ml of normal saline. Do not exceed an infusion rate of 20 mEq/hr (100 ml/hr).

Magnesium replacement therapy

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MAGNESIUM LEVEL	TOTAL DAILY DOSE	MONITORING FREQUENCY
2.0 or more	None	Monthly
1.5–1.9	1000 mg–1200 mg	Monthly
1.0–1.4	2000 mg	One to seven days
<1.0	3000 mg–6000 mg	Daily

: Note: Quantities greater than 2000 mg are usually given by IV or intramuscular (IM). The normal preparation is magnesium sulfate 2 g in 100 ml or 4 g in 250 ml of 5% dextrose or normal saline. Do not exceed an infusion rate of 150 mg/min (2 g in 100 ml administered over one to two hours, 4 g in 250 ml administered over two to four hours).

Calcium replacement therapy

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CALCIUM LEVEL (TOTAL NONIONIZED CALCIUM VALUE ADJUSTED FOR LOW ALBUMIN)	DOSING	MONITORING FREQUENCY
>8.5 mg/dl (>4.2 mEq/l)	None
7.5–8.4	500 mg three times a day	Monthly
7.0–7.4	1000 mg three times a day	One to two weeks
<7.0	Consider intravenous and taper to 1000 mg three times a day	One to four days

: Note: Normal calcium is 8.5–10.3 mg/dl (2.12–2.57 mmol/l). To adjust for low albumin in nonionized values of calcium, use this formula: Corrected calcium = 0.8 × (4.0 – measured albumin) + reported calcium. If ionized calcium is being tested, it does not need to be adjusted for low albumin and normal value is 4.5–5.6 mg/dl (1.11–1.30 mmol/l).

3: This annex is adapted from The PIH guide to the medical management of multidrug-resistant TB. 2nd Edition. Boston: Partners In Health; 2013. .

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