What is the best course of treatment for a patient with severe vomiting for 3 days, resulting in hypokalemia and dehydration?

Immediate Management of Severe Vomiting with Hypokalemia and Dehydration

This patient requires immediate intravenous fluid resuscitation with isotonic crystalloids and concurrent potassium replacement, as 3 days of vomiting has likely caused severe dehydration (≥10% fluid deficit) and dangerous hypokalemia that threatens cardiac stability. 1

Initial Assessment and Severity Classification

Assess dehydration severity immediately by evaluating pulse quality, perfusion status, mental status, postural vital signs, and capillary refill time. 1 After 3 days of vomiting, this patient likely has severe dehydration (≥10% fluid deficit) requiring emergency intervention. 1

Obtain immediate labs including serum potassium, sodium, chloride, bicarbonate, magnesium, glucose, and renal function (creatinine, BUN). 2, 3 Check an ECG immediately to assess for hypokalemia-induced cardiac changes (ST depression, T wave flattening, prominent U waves, QT prolongation). 2, 3

Emergency Fluid Resuscitation

Begin immediate IV fluid resuscitation with isotonic crystalloids (normal saline or lactated Ringer's solution) at 20 mL/kg boluses until pulse, perfusion, and mental status normalize. 1 This may require two IV lines or alternate access sites (venous cutdown, femoral vein, intraosseous infusion) if the patient is in shock or near-shock. 1

For severe dehydration with vomiting, administer isotonic IV fluids aggressively - patients with prolonged vomiting typically have total water deficits of 6-9 liters and require fluid replacement within the first 24 hours. 1, 4

Potassium Replacement Strategy

Do NOT delay potassium replacement once adequate urine output is confirmed and serum potassium is known. 1, 2

If serum potassium is <3.3 mEq/L:

• Hold any insulin therapy until potassium is restored to prevent life-threatening arrhythmias. 2
• Administer IV potassium chloride 20-40 mEq/L added to maintenance IV fluids (NOT as a bolus). 1, 5
• Use central venous access if available for concentrations >40 mEq/L to avoid peripheral vein irritation and ensure thorough dilution. 5

If serum potassium is 3.3-5.5 mEq/L:

• Add 20-30 mEq/L potassium chloride (2/3 KCl and 1/3 KPO4) to each liter of IV fluid. 1, 2

Administration rates:

• Standard rate: 10 mEq/hour maximum (200 mEq per 24 hours) if serum potassium >2.5 mEq/L. 5
• Urgent correction: up to 40 mEq/hour (400 mEq per 24 hours) if serum potassium <2.0 mEq/L with ECG changes or muscle paralysis, but ONLY with continuous cardiac monitoring. 5, 6

Critical Concurrent Interventions

Check and correct magnesium immediately - hypomagnesemia is the most common reason for refractory hypokalemia and must be corrected before potassium levels will normalize. 2, 3 Target magnesium >0.6 mmol/L (>1.5 mg/dL). 2

Administer antiemetics to stop ongoing losses - ondansetron 4-8 mg IV is first-line for severe vomiting. This is critical because ongoing vomiting will continue depleting potassium and fluids faster than you can replace them.

Monitor serum osmolality carefully - the induced change should not exceed 3 mOsm/kg/h to prevent neurological complications, especially if the patient is also hyperglycemic. 4

Monitoring Protocol

Continuous cardiac monitoring is mandatory during IV potassium administration, especially if initial potassium <2.5 mEq/L or ECG changes are present. 5, 3

Recheck potassium levels:

• Within 1-2 hours after starting IV potassium correction 2
• Every 2-4 hours during acute treatment phase until stabilized 2
• Before each additional dose if multiple doses needed 2

Reassess hydration status every 2-4 hours until pulse, perfusion, and mental status normalize, then the patient can transition to oral rehydration. 1

Transition to Maintenance Therapy

Once rehydrated and able to tolerate oral intake, transition to oral rehydration solution (ORS) containing 50-90 mEq/L sodium. 1 Commercial formulations include Pedialyte, CeraLyte, or Enfalac Lytren - do NOT use apple juice, Gatorade, or soft drinks. 1

Replace ongoing losses with 10 mL/kg ORS for each episode of vomiting and continue until vomiting resolves. 1

Oral potassium supplementation (20-40 mEq daily divided into 2-3 doses) should continue until dietary intake is adequate and potassium stabilizes at 4.0-5.0 mEq/L. 2, 3

Common Pitfalls to Avoid

Never administer potassium as an IV bolus - this can cause cardiac arrest. Always dilute in IV fluids and infuse slowly. 5, 6

Never use glucose-containing solutions (D5W) as the primary diluent for potassium in severe hypokalemia - glucose stimulates insulin release, driving potassium intracellularly and worsening hypokalemia. 7 Use normal saline or lactated Ringer's instead.

Never supplement potassium without checking magnesium first - this is the most common reason for treatment failure. 2, 3

Do not discharge until potassium is >2.5 mEq/L, vomiting has stopped, patient can tolerate oral intake, and outpatient follow-up within 3-7 days is arranged. 2