11.2 Fluid Overload, Severe Dysnatremias & Life-Threatening Hyperkalemia Emergencies
Key Takeaways
Estimate cumulative fluid accumulation using intake minus output indexed to baseline weight. Increasing accumulation with organ dysfunction warrants reassessment and early nephrology input. Percentages are risk markers, not automatic dialysis thresholds.
Treat seizures from hypotonic hyponatremia with prompt 3% saline bolus rescue. Reassess symptoms and sodium and aim for an initial rise of about 4–6 mEq/L.
In chronic or unknown-duration hyponatremia, count the rescue rise toward a conservative 8 mEq/L first-day ceiling. Use a lower target for high-risk patients and monitor for water diuresis.
Restore perfusion first in hypernatremic dehydration. Then adjust the deficit and ongoing-loss prescription to serial sodium, commonly aiming for a fall no faster than 0.5 mEq/L/h when chronicity is uncertain.
In severe hyperkalemia, monitor the ECG and give IV calcium promptly for cardiotoxic changes. Shift potassium with insulin and dextrose, with inhaled albuterol as appropriate. Track glucose and potassium while treating the cause and arranging removal, including urgent KRT when indicated.
Fluid Overload, Severe Dysnatremias & Life-Threatening Hyperkalemia Emergencies
Quick Answer: Index cumulative fluid balance to baseline weight and interpret it alongside organ function. Treat severe symptomatic hypotonic hyponatremia with prompt 3% saline rescue and then control the total sodium rise. Restore perfusion before gradual correction of hypernatremic dehydration. Give IV calcium for hyperkalemic cardiotoxicity while shifting and arranging removal of potassium.
Fluid Overload in the PICU: Mathematical Quantification and Clinical Prognosis
Fluid administration is a cornerstone of early shock resuscitation. However, once intravascular volume is restored, persistent positive fluid balances drive pathological interstitial third-spacing, tissue edema, and end-organ dysfunction. Fluid accumulation can contribute to organ dysfunction. It also tracks illness severity, which complicates causal interpretation of outcomes.
The Percentage Fluid Overload (%FO) Formulation
Index cumulative intake minus output to a documented baseline weight, approximating 1 L of water as 1 kg:
Serial weights provide a separate estimate. Compare measurements obtained under similar conditions. Fluid records and scale weights can disagree because of unmeasured loss, equipment or changes in tissue mass:
Interpret fluid accumulation with organ function
In the original ppCRRT cohort, mortality by fluid accumulation at CRRT initiation was 45/153 (29.4%) below 10% fluid accumulation, 22/51 (43.1%) from 10% to below 20%, and 61/93 (65.6%) at or above 20%. These are cohort rates among children already receiving CRRT. In the newer WE-ROCK registry analysis, greater accumulation was associated with fewer ventilator- and ICU-free days after adjustment, without an independent ICU mortality association. Check perfusion, lung findings, fluid inputs and urine output. Involve nephrology early if fluid accumulation progresses with organ dysfunction despite medical measures. Original ppCRRT registry · WE-ROCK study · KDIGO AKI guideline
Connect accumulation to the bedside findings
Pulmonary hydrostatic pressure and increased permeability can both contribute to edema. Worsening compliance and oxygenation can reflect more than fluid accumulation alone. Renal function depends on arterial perfusion and can also worsen with venous or intra-abdominal congestion. After Fontan surgery, the arterial-minus-central-venous pressure gradient was associated with AKI in a cohort. Use it as a contextual estimate. Abdominal perfusion pressure is a different calculation (MAP minus intra-abdominal pressure). Neither is an automatic fluid or dialysis target. Fontan cohort · WSACS consensus
Treat severe dysnatremias according to symptoms and trajectory
Hyponatremia
Determine whether low sodium represents hypotonicity. Check glucose and measured serum osmolality when appropriate. Severe hyperglycemia can lower measured sodium through a transcellular water shift. When feasible, obtain paired serum and urine osmolality and urine sodium to assess water handling and volume status. Do this in parallel with emergency care. Acute hypotonicity can cause cerebral edema, while a brain adapted to chronic hypotonicity is vulnerable to overly rapid correction.
Seizure or severe encephalopathy attributed to hypotonic hyponatremia: Support the airway and circulation, treat an ongoing seizure, and give a prompt pediatric-protocol bolus of 3% saline. Sodium correction is time-critical because seizures may persist despite antiseizure medication. Bolus regimens vary. The Moritz–Ayus pediatric regimen uses 2 mL/kg of 3% saline (maximum 100 mL) over 10 minutes with reassessment for repeat dosing. Use the local pediatric protocol and check sodium promptly after rescue dosing. Aim for symptom improvement with an initial rise of about 4–6 mEq/L. A child who remains symptomatic despite that rise needs urgent reassessment for other causes. The initial rescue is indicated even when the duration of hyponatremia is chronic or uncertain. Pediatric seizure study · Moritz–Ayus pediatric regimen · Pediatric hyponatremia guideline
After rescue: In chronic or unknown-duration hyponatremia, count the rescue rise in the total change. A conservative pediatric limit is 8 mEq/L in 24 hours, with a lower target in those at high risk of osmotic demyelination, such as patients with marked hyponatremia, malnutrition, hypokalemia or advanced liver disease. Treat the cause and use frequent sodium and urine-output monitoring. A sudden water diuresis may accelerate correction even after stopping hypertonic saline. For example, a rise from 114 to 119 mEq/L achieves a 5 mEq/L rescue rise. An 8 mEq/L first-day ceiling leaves only another 3 mEq/L by 24 hours from the original value. If the rise threatens to exceed the limit, stop active correction and obtain expert input. Desmopressin and electrolyte-free water may be used to arrest or reverse overcorrection in selected cases, with close monitoring. They are not the initial treatment for a hyponatremic seizure. Pediatric correction limit · U.S. expert panel · Desmopressin clinical series
Hypernatremic dehydration
Separate water loss or inadequate intake from sodium gain. Gastrointestinal losses, diabetes insipidus and concentrated formula illustrate different mechanisms. Paired serum and urine osmolality can help distinguish renal water loss from intact renal concentration. Restore perfusion first with isotonic crystalloid in hypovolemic shock. After stabilization, replace the deficit and ongoing losses while adjusting for maintenance needs and serial sodium. The Royal Children’s Hospital Melbourne guideline starts moderate water-deficit hypernatremia with 0.9% saline plus 5% glucose, including deficit replacement over about 48 hours. Change rate and composition to match the response. Consult critical care early for severe or rapidly changing values, sodium intoxication or a suspected concentrating defect. Routine pediatric maintenance-fluid guidance excludes conditions such as DI and renal dysfunction. Pediatric hypernatremia guideline · AAP maintenance-fluid scope
An estimate for free water alone uses current total body water () in liters. Holding body solute constant, the calculated water addition dilutes the initial concentration toward the chosen target.
TBW varies with age and body composition. The estimate omits ongoing loss and isotonic volume deficit and does not prescribe a fluid or delivery rate. For chronic or unknown-duration hypernatremia, a common pediatric protocol limits the decrease to about 0.5 mEq/L/h and 12 mEq/L/day after perfusion is restored. Check sodium early after starting therapy (for example, after 1–2 hours) and serially thereafter. Adjust promptly when the trend is too fast or too slow. A retrospective cohort of children aged six months and older did not find excess neurologic events with faster correction. It does not establish a safe faster rate in neonates or every cause. New seizures or neurologic change require urgent reassessment of sodium trajectory, glucose, and intracranial complications. Hypertonic saline may be considered with critical care input if sodium has fallen too rapidly. Water deficit model · Pediatric hypernatremia guideline · Pediatric correction cohort
Stabilize the child with severe hyperkalemia
Rising extracellular potassium makes the resting membrane potential less negative. Sustained depolarization inactivates sodium channels and slows conduction. Look for peaked T waves, PR prolongation, loss of P waves, widening QRS, bradyarrhythmia or a sine-wave pattern. These changes can occur in different orders, and an initially normal ECG can accompany severe hyperkalemia. Use a reliable sample, the trend and the clinical context alongside the ECG. Start cardiac monitoring, stop potassium-containing infusions and repeat a suspect hemolyzed sample promptly. Treat immediately if there is credible hyperkalemia with cardiotoxicity. ECG study · Nationwide Children's inpatient pathway
Stabilize the myocardium
IV calcium counteracts the effect of hyperkalemia on excitability without reducing the potassium concentration. Give it immediately for cardiotoxic ECG changes. In the 2026 Nationwide Children's inpatient pathway for children at least 90 days old, calcium gluconate is preferred at 60–100 mg/kg IV over 10 minutes (maximum 3 g). Calcium chloride via a central line is an alternative at 20 mg/kg over 10 minutes (maximum 1 g). These are doses of the salts. At a 10% concentration, calcium chloride provides about three times the elemental calcium per mL and poses greater injury if it extravasates. Use the local emergency protocol, monitor the ECG and reassess promptly for persistent or recurrent changes that may require repeat calcium.
Shift potassium temporarily
Give regular insulin with dextrose and consider nebulized albuterol as an adjunct. Both activate cellular sodium-potassium pumps. For example, the same inpatient pathway uses regular insulin 0.1 unit/kg IV (maximum 10 units) with 0.5–1 g/kg dextrose (5–10 mL/kg if using D10). It uses 10 mg aerosolized albuterol below 15 kg or 15 mg from 15 kg upward. Follow the local dose and administration plan. Check glucose and potassium frequently for hypoglycemia and rebound hyperkalemia. Consider bicarbonate separately in selected patients with significant metabolic acidosis. Its response is variable, and it adds sodium and can lower ionized calcium.
Remove potassium and address the cause
A loop diuretic may increase urinary potassium loss if the child is producing urine and the hemodynamics allow it. Oral binders are too slow or unpredictable for emergency stabilization. Sodium zirconium cyclosilicate has a U.S. adult indication and a label limitation for emergency use. Sodium polystyrene sulfonate carries warnings for serious intestinal injury, including necrosis, and concurrent sorbitol is discouraged. In a child with AKI and severe refractory or recurrent hyperkalemia, arrange KRT urgently while temporary measures are taking effect. Select intermittent hemodialysis or continuous support according to clearance needs and hemodynamic tolerance. Inpatient pediatric hyperkalemia pathway · LOKELMA U.S. label · Sodium polystyrene sulfonate U.S. label · KDIGO AKI guideline
A 5-year-old child with severe septic shock weighed 20.0 kg upon admission to the PICU. Over the first four hospital days, the electronic health record documents a cumulative fluid intake of 14,500 mL and a cumulative fluid output of 11,500 mL. The child remains intubated and exhibits bilateral pulmonary crackles, gross anasarca, and worsening oliguria with rising central venous pressure. His oxygen requirement is increasing. What is his cumulative percentage fluid accumulation, and how should the team use it?
The %FO is 7.5%; this level is benign and requires no modification of current maintenance fluid administration.
The %FO is 10.0%; this reflects moderate fluid retention that rarely impacts mechanical ventilation duration or ICU length of stay.
The %FO is 25.0%; this degree of fluid overload directly correlates with acute pulmonary hypertension requiring emergency vasodilators.
The fluid accumulation is 15%. With worsening oxygenation and oliguria, reassess fluid delivery and perfusion and involve nephrology early.
A 2-year-old has received excessively diluted formula for three weeks and has no recent normal sodium result. He is actively seizing with serum sodium 114 mEq/L and glucose 92 mg/dL. Alongside airway and seizure support, which sodium-directed treatment and follow-up best fit?
Give a prompt pediatric-protocol 3% saline bolus. Recheck sodium and symptoms for repeat dosing, aiming for an initial rise of about 4–6 mEq/L and counting it toward a conservative 8 mEq/L first-day ceiling.
Use isotonic saline alone for seizure rescue and target an increase of 15–20 mEq/L by 24 hours.
Give desmopressin and electrolyte-free water immediately to lower sodium before treating the seizure.
Use mannitol alone and wait for urine output to increase before addressing sodium.
A 10-year-old boy with newly diagnosed T-cell acute lymphoblastic leukemia develops acute tumor lysis syndrome and oliguric AKI in the PICU. Continuous cardiac monitoring reveals tall, symmetrical, tented T waves, PR interval prolongation to 240 ms, and marked widening of the QRS complex to 160 ms. STAT serum electrolytes confirm a potassium level of 7.9 mEq/L. The patient has a functioning right internal jugular double-lumen central venous catheter. What is the immediate first-line pharmacological action, and why?
Give insulin with dextrose first because potassium shifting immediately restores myocardial stability.
Give IV calcium immediately according to the pediatric emergency protocol to stabilize the myocardium.
Start an oral potassium binder first because intestinal potassium removal acts within minutes.
Give rapid IV bicarbonate first to stabilize the cardiac membrane before addressing potassium.
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