In this case, VT occurred without any preceding ECG change despite hyperkalemia due to mannitol. Lethal arrhythmia often occurs during neurosurgery. In general, there have been cases during surgical operations near the brainstem with an increased sympathetic nerve system due to the rupture of a cerebral aneurysm and with hemorrhage shock during craniotomy. There are a few reports of fatal arrhythmia, VT, and/or ventricular fibrillation due to mannitol, which mainly is due to hyperkalemia [3,4,5].
Mannitol is widely used to reduce the intracranial pressure due to an increase in plasma osmolality. However, it has several side effects, including osmotic nephrosis and electrolyte imbalance [6]. The rapid infusion of mannitol can cause hyponatremia or hyperkalemia. Hyponatremia is mainly due to a transient dilution. During mannitol-induced hyperkalemia, intracellular K is thought to be released into the extracellular space due to an acute increase in plasma osmolality, rhabdomyolysis, hemolysis, and acidosis [1, 7]. In this case, preoperative renal function was normal and there were no findings of acidosis, rhabdomyolysis, or hemolysis. The frequency of mannitol-induced hyperkalemia is 7.7%, and the total dose of mannitol as well as its rate of infusion and decreased renal function may have a role in the development of mannitol-induced hyperkalemia [4]. We used a total dose of 40 g mannitol, which was within the recommended dose (0.25–1 g/kg) [8], and the infusion rate was 60 min, which was not rapid.
In most cases, the ECG change—elevated T waves—was the primary finding. All cases of lethal arrhythmia reported thus far have been preceded by ECG change, including peaked T waves and a wide QRS complex [3,4,5]. However, no preceding ECG change was observed in our case, and transient peaked T waves appeared after recovery to sinus rhythm from VT. With regard to ECG changes in hyperkalemia, such as elevated T wave (tentative T wave), P wave decrease, prolonged PQ interval due to an increase in serum K value, QRS width extension, P wave disappearance and its further increase that leads to an unclear distinction between QRS and T waves, and heartbeats becoming standstill [9]. However, ECG without any finding consistent with hyperkalemia is noted in > 50% of patients with K > 6.5 mEq/L, and arrhythmia and cardiac arrest have been reported in patients with hyperkalemia without a preceding peak T wave [10, 11]. It is not clear why VT occurred in this case, but in addition to transient potassium elevation due to potassium permeability to cardiac membrane by myocardial ischemia [12] and mannitol, craniotomy itself may have influenced it.
Therefore, physicians should be aware that lethal arrhythmia can occur due to mannitol-induced hyperkalemia.