Postoperative fluid retention after heart surgery is accompanied by a strongly positive sodium balance and a negative potassium balance

Abstract

The conventional model on the distribution of electrolyte infusions states that water will distribute proportionally over both the intracellular (ICV) and extracellular (ECV) volumes, while potassium homes to the ICV and sodium to the ECV. Therefore, total body potassium is the most accurate measure of ICV and thus potassium balances can be used to quantify changes in ICV. In cardiothoracic patients admitted to the ICU we performed complementary balance studies to measure changes in ICV and ECV. In 39 patients, fluid, sodium, potassium, and electrolyte‐free water (EFW) balances were determined to detect changes in ICV and ECV. Cumulatively over 4 days, these patients received a mean ± SE infusion of 14.0 ± 0.6 L containing 1465 ± 79 mmol sodium, 196 ± 11 mmol potassium and 2.1 ± 0.1 L EFW. This resulted in strongly positive fluid (4.0 ± 0.6 L) and sodium (814 ± 75 mmol) balances but in negative potassium (−101 ± 14 mmol) and EFW (−1.1 ± 0.2 L) balances. We subsequently compared potassium balances (528 patients) and fluid balances (117 patients) between patients who were assigned to either a 4.0 or 4.5 mmol/L blood potassium target. Although fluid balances were similar in both groups, the additionally administered potassium (76 ± 23 mmol) in the higher target group was fully excreted by the kidneys (70 ± 23 mmol). These findings indicate that even in the context of rapid and profound volume expansion neither water nor potassium moves into the ICV.

Estimation of sodium and chloride storage in critically ill patients: a balance study

“…Critical illness is often accompanied with critical illness myopathy, and loss of sodium and chloride to the ICV might then also be conceivable [ 31 ]. As we reported in an earlier study [ 8 ], our patients displayed a negative potassium balance of 101 mmol, which is another argument for possible intracellular uptake of sodium in exchange for potassium release. Moreover, we also observed a negative electrolyte-free water (EFW) balance in these patients.…”

“…Moreover, we also observed a negative electrolyte-free water (EFW) balance in these patients. Together, this suggests that no ICV expansion occurred [ 8 ]. Therefore, we assumed that all fluids administered (including EFW) remained in the ECV.…”

“…The most important components to determine electrolyte balances are detailed records of fluids, administered to or lost by the patient, including 24-h urine analyses. The detailed calculations used for determining water, sodium and chloride balances, including the estimation for (in)sensible perspiration, have been described earlier and are specified in detail in Additional file 1 : Tables S1–S3 [ 8 ]. Insensible perspiration was calculated as: Insensible perspiration = 10 mL/kg/day + 2.5 mL/kg/day per degree centigrade above 37 °C (max body weight in equation 100 kg) (× 0.6 if intubated)(× 0.5 on admission day) [ 14 ].…”

“…Patients admitted to the intensive care unit (ICU) typically receive large amounts of sodium and chloride during their ICU treatment [ 8 ]. Both hypernatremia and hyperchloremia are a frequent complication in critically ill patients and are associated with adverse outcome [ 9 – 12 ].…”

Intensive Care Unit Acquired Hypernatremia after Major Surgery is Associated with Urine Concentrating Defect: An Observational Study

“…Supporting this, in logistic regression analysis, no association could be seen between the development of hypernatremia and the administration of loop diuretics, hydrocortisone, noradrenalin or argipressin (Additional le, S2). Interestingly, the potassium balance in both groups was negative as observed in a study with heart surgery patients [12].…”