Do Burns Cause Hypokalemia or Hyperkalemia?

Burns can cause both hypokalemia and hyperkalemia, and the direction of the shift depends on the type of burn, how much time has passed since the injury, and what treatments the patient is receiving. In the earliest moments after a severe burn, damaged cells spill their contents into the bloodstream, and potassium is the most abundant ion inside cells, which should theoretically push levels up. Yet in clinical practice, low potassium turns out to be at least as common as high potassium in burn patients, driven by aggressive fluid resuscitation, wound losses, and hormonal stress responses that push potassium back into cells.

Why Burns Should Push Potassium Up

When heat, electricity, or a chemical agent destroys skin and deeper tissues, cell membranes break apart. The contents of those cells flood into the surrounding fluid and eventually reach the bloodstream. Because potassium is far more concentrated inside cells than outside them, widespread cell death creates a sudden surge of potassium into the extracellular space. In theory, this should drive serum potassium levels up, and in the most severe cases it does.

High-voltage electrical injuries provide the clearest example. Electrical current follows the path of least resistance, traveling through muscle, blood vessels, and nerves rather than just skin. When large masses of muscle are destroyed, the resulting condition, rhabdomyolysis, floods the bloodstream with myoglobin, creatine kinase, and potassium. An estimated 10% of survivors of high-voltage electrical injuries develop rhabdomyolysis, and acute kidney injury is its most significant complication because myoglobin is toxic to the kidney’s filtering system.¹ When the kidneys cannot clear the excess potassium, levels climb further. This combination of massive potassium release and impaired kidney function is the scenario most likely to produce dangerous hyperkalemia after a burn.

Yet even in electrical burns, frank hyperkalemia at hospital admission is surprisingly uncommon. A retrospective study of electrical burn patients in Colombia found that only about 1% had elevated potassium on arrival, while roughly 14% actually had low potassium and about 85% had normal levels.² The researchers found no association between the potassium level and either the percentage of body surface area burned or the degree of muscle breakdown. That finding caught many clinicians off guard, because the intuition that more tissue damage equals higher potassium turns out to be far too simple.

Why Low Potassium Is More Common Than You Might Expect

If burns destroy cells packed with potassium, why doesn’t hyperkalemia dominate? Several forces push potassium in the opposite direction, and in most burn patients they win out.

The stress response to a major burn triggers a surge of adrenaline and cortisol. These hormones activate the sodium-potassium pumps on cell membranes throughout the body, driving potassium from the bloodstream back into intact cells. This redistribution can happen fast enough to counterbalance the potassium being released from damaged tissue. Burn patients also lose enormous volumes of fluid through their wounds. The protein-rich exudate that weeps from injured skin carries electrolytes with it, and the larger the burn, the greater these losses become.

Probably the most important factor in modern burn care is intravenous fluid resuscitation. Burn patients receive large volumes of crystalloid solution in the first 24 to 48 hours to maintain blood pressure and organ perfusion. That fluid dilutes serum potassium and increases urine output, flushing potassium out through the kidneys. A study examining serum electrolyte concentrations on the first day of hospitalization found that potassium values in burn patients tended to sit at the lower end of the normal reference range, with no significant relationship between potassium levels and either the extent or severity of the burn.³

The type of resuscitation fluid matters too. A study comparing isotonic crystalloids to hypotonic crystalloids in major flame burns found that isotonic solutions produced better overall electrolyte balance.⁴ Hypotonic fluids dilute serum sodium more aggressively and create downstream electrolyte instability, making it harder to keep potassium in a safe range. This is one reason burn units are particular about which fluids they hang on the IV pole.

Chemical Burns and Unusual Electrolyte Patterns

Not all burns are thermal or electrical. Chemical burns can produce electrolyte shifts through mechanisms that have nothing to do with simple cell lysis, and the results can be the opposite of what you would predict from tissue destruction alone.

Hydrofluoric acid, used in industrial settings and some cleaning products, is a particularly dangerous example. A case report described a 48-year-old man exposed to 70% hydrofluoric acid who developed hypocalcemia, hypomagnesemia, and hypokalemia after his injury.⁵ Fluoride ions bind avidly to calcium and magnesium in the blood, pulling those levels down. The resulting low potassium was likely driven partly by the magnesium depletion, because the kidneys need adequate magnesium to retain potassium, and partly by acid-base disturbances that followed. The pattern, where the burn itself drives potassium down rather than up, underscores why the type of burn matters so much when predicting electrolyte changes.

The Succinylcholine Problem

One of the most consequential potassium issues in burn care has nothing to do with the burn itself and everything to do with a drug commonly used during surgery: succinylcholine (also called suxamethonium). This muscle relaxant is a standard tool for rapid intubation in emergency medicine, but it is contraindicated in burn patients after roughly the first day post-injury.

Succinylcholine works by activating the same receptors on muscle cells that the nerve signal normally uses. In healthy muscle, this causes a brief, controlled release of potassium into the bloodstream, usually too small to matter. But after a major burn, the body grows extra acetylcholine receptors across the muscle membrane, including immature receptor types that allow a much larger potassium efflux than the normal mature receptors do.⁶ Burns share this receptor-proliferation phenomenon with spinal cord injuries, prolonged immobility, major trauma, and muscular dystrophy.

The practical result is that giving succinylcholine to a burn patient who is days to weeks out from the injury can trigger a sudden, massive release of potassium into the blood. That spike can be severe enough to cause fatal cardiac arrhythmias or cardiac arrest.⁷ The risk persists for months after the burn, sometimes up to a year or more, because the receptor changes take a long time to reverse. Burn units therefore use alternative muscle relaxants for intubation. The protocol is so well established that succinylcholine-induced hyperkalemia in burn patients has become a textbook example taught to every anesthesiology trainee, and yet the occasional error still occurs when a burn patient undergoes an unrelated surgery at a facility less familiar with the risk.

How Timing Changes the Clinical Picture

The electrolyte story in a burn patient is not static. It unfolds over hours and days, and the predominant direction of potassium shift changes with it.

In the first minutes to hours after a major burn, the dominant force is cellular destruction. Potassium leaves damaged cells and enters the extracellular fluid. If the burn is massive, involves substantial muscle (as in electrical injuries), or if kidney function is compromised, hyperkalemia is a real early threat. This window is short, though. Within hours, as the stress response kicks in and fluid resuscitation begins, potassium is driven back into cells by catecholamines and diluted by large volumes of intravenous fluid. By the time most patients are established in a burn intensive care unit, hypokalemia is often the more pressing concern.

In the days and weeks that follow, nutritional losses compound the problem. Burn patients have dramatically elevated metabolic rates and need large amounts of nutrition, but meeting those needs takes time. Inadequate potassium intake through feeding, combined with ongoing wound losses, keeps hypokalemia as a persistent management challenge well into the recovery phase. Clinicians in burn units check potassium levels frequently, sometimes multiple times a day in patients with large burns, and supplement potassium intravenously when levels drift below normal.

Cardiac Risks From Potassium Disturbances

Whether potassium swings high or low, the heart is the organ most immediately at risk. The heart’s electrical system depends on a narrow range of potassium to generate and conduct the signals that produce a regular heartbeat, and burn patients are already under enormous cardiovascular stress.

Hyperkalemia slows electrical conduction through the heart muscle. Mild elevations may show up only as subtle changes on a heart tracing, but severe hyperkalemia can cause the heart to stop beating entirely. This is the mechanism behind cardiac arrest from succinylcholine in burn patients and is also the feared outcome when rhabdomyolysis from an electrical burn goes unrecognized.⁷

Hypokalemia is dangerous in a different way. Low potassium makes the heart more excitable, increasing the risk of abnormal rhythms, particularly the rapid, disorganized ventricular arrhythmias that can be fatal without immediate intervention. In a critically ill burn patient who may already have low blood pressure and poor oxygen delivery, even moderate hypokalemia narrows the margin of safety considerably. This is one reason the choice of resuscitation fluid receives so much scrutiny: a solution that does a better job maintaining electrolyte balance is not just a biochemical nicety, it is a cardiac safety measure.

When Potassium Levels Do Not Follow the Pattern

Not every burn patient follows the trajectory described above, and pre-existing conditions can tip the balance in unexpected ways. People with chronic kidney disease may be unable to clear even a modest potassium surge, making hyperkalemia more likely and more dangerous from a moderate burn. Patients on potassium-sparing diuretics, ACE inhibitors, or angiotensin receptor blockers arrive with baseline conditions that already favor higher potassium levels.

Conversely, patients with conditions that chronically deplete potassium, like long-term diuretic use, eating disorders, or alcoholism, may drop to dangerous levels faster than expected once the burn triggers additional losses. Age plays a role too: older adults generally have less muscle mass and less kidney reserve, which narrows the margin for error in both directions.

The size and depth of the burn matter, but not always in the ways people assume. A very large superficial burn affecting mostly the outer skin layers can produce enormous fluid and electrolyte losses through the wound surface, favoring hypokalemia. A smaller but deeper burn that penetrates into muscle may produce a sharper potassium release despite involving a smaller area of skin. The Colombian electrical burn study found no correlation between the percentage of body surface burned and the serum potassium level, suggesting that it is the type and depth of tissue destruction, not simply the area of skin involved, that determines which direction potassium moves.² Clinicians who care for burn patients treat potassium as a number that requires constant surveillance rather than one that can be predicted from the burn characteristics alone.