Potassium derangements are associated with increased mortality at the intensive care unit
(ICU). This study hypothesizes that increased renal loss of potassium plays a role in the
development of potassium derangements in patients with traumatic brain injury who received
thiopental to induce barbiturate coma (Study A) and in patients who were cooled to
therapeutic hypothermia (TH, 33°C) or therapeutic normothermia (TN, 36°C) following an
out-of-hospital cardiac arrest (OHCA) (Study B).
A single-centre retrospective study was performed. Serum potassium levels were used to
determine the incidence of potassium derangements. Potassium balances were calculated from
potassium intake and potassium excretion. In Study A three phases were compared; before,
during and after thiopental infusion. In Study B the hypothermia/normothermia phase
(HT/NT phase) consisted of two calendar days after admission. The post-HT/NT phase
consisted of two calendar days following cessation of the HT/NT phase.
Five patients were included in Study A and 34 patients in Study B (n=16 for TH, n=18 for
TN). In Study A, the incidence of hypokalemia was higher during thiopental infusion
compared to before and after therapy, respectively, 100%, 60% and 25% (P=0.03). There
were no significant differences between potassium balances during thiopental therapy
compared to before and after therapy. In Study B, median cumulative potassium
administration during the HT/NT phase was 112 (IQR, 65 to 142) mmol in the TH group
compared to 36 (IQR, 25 to 54) mmol in the TN group (P<0.001), which resulted in median
serum potassium levels of, respectively, 4.2 (IQR, 3.9 to 4.6) mmol/L and 4.0 (IQR, 3.8 to
4.3) mmol/L (P<0.001). Hyperkalemia was more common in the TH group than in the TN
group, respectively, in 63% and 11% of patients (P=0.003). There was no difference in
median potassium balances between the TH group and the TN group (P=0.145).
In our study increased renal loss of potassium did not play an evident role in the development
of hypokalemia during thiopental infusion and during hypothermia. Since hypokalemia was
common during thiopental infusion whereas hyperkalemia was common during and after
cooling in the TH group, potassium should be monitored regularly in order to be able to adjust
potassium administration. An additional study with increased sample size is necessary to
determine the exact role of renal potassium loss in patients who received a barbiturate coma
or were cooled to hypothermia/normothermia after hospital admission with an OHCA.
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