Hyperkalemia & AKI NGN Case Study

The life threat: K⁺ 6.8 with EKG changes — peaked T waves and bradycardia. Potassium this high with cardiac effects can degrade to a sine wave and arrest with little warning. The leg weakness is the same story told by skeletal muscle.

The kidney story: creatinine tripled from baseline (3.1 from 1.1), BUN 88, and minimal urine output — acute kidney injury, with a BUN:Cr ratio and an exam (dry, hypotensive-for-him, three days of GI losses) that scream volume depletion.

The medication cue everyone misses: ACE inhibitor + potassium-sparing diuretic + NSAID — the “triple whammy.” Each impairs renal perfusion or potassium excretion; together, on a dehydrated patient, they built this lab panel.

Prerenal AKI (most supported): vomiting and diarrhea drained his volume; the NSAID constricted the afferent arteriole and the ACE inhibitor dilated the efferent — together they stripped the glomerulus of perfusion pressure exactly when it had no volume reserve. Low flow → falling GFR → BUN and creatinine climb, urine output falls.

The potassium arithmetic: failing filtration stops potassium excretion; spironolactone blocks what excretion remains; the ACE inhibitor suppresses aldosterone further. Intake continued, elimination stopped — serum potassium climbs.

Worth excluding: intrinsic AKI (ATN from prolonged hypoperfusion — possible if this has cooked too long; urine studies help), postrenal obstruction (bladder scan — quick and free, especially in an older man), and pseudohyperkalemia from a hemolyzed sample — but with EKG changes, you treat first and re-verify in parallel, never wait.

1. The myocardium — hyperkalemia with EKG changes is the immediate killer; everything else waits behind it.

2. The volume deficit — it is both a circulation problem and the cause of the AKI; restoring perfusion is how the kidneys come back online and start excreting potassium again.

3. The offending medications — all three are held today; this is the relapse-prevention move.

NGN logic: stabilize what’s lethal (the heart), treat the cause (volume), remove the perpetuating factors (the triple whammy) — three tiers, worked nearly in parallel but prioritized in exactly that order.

Protect (does nothing to the K⁺ level): IV calcium gluconate stabilizes the cardiac membrane within minutes — it buys time, nothing more. With EKG changes, it is always first.

Shift (hides K⁺ inside cells — temporary): IV regular insulin with dextrose (the workhorse) and nebulized albuterol drive potassium intracellularly for a few hours. The level falls; the total body burden doesn’t.

Remove (actually lowers total potassium): restore urine output with isotonic fluids for his prerenal state (working kidneys are the best potassium remover), potassium-binding agents per orders, and dialysis if he stays oliguric and hyperkalemic despite everything.

Plus the housekeeping that prevents round two: hold lisinopril, spironolactone, and naproxen; stop any K⁺-containing fluids or supplements; continuous cardiac monitoring; strict I&O with a bladder scan; serial K⁺ and glucose checks.

Calcium first, even though it arrived second. The membrane is the emergency — peaked T waves mean the heart is one rhythm strip from trouble, and calcium is the only drug on the list that protects it now. Then the shifters (insulin/D50, albuterol), then the removers (fluids, binder), in quick succession.

The insulin commitment: IV insulin in a patient who isn’t hyperglycemic means scheduled glucose checks for several hours — hypoglycemia is the most common complication of hyperkalemia treatment, and it often lands after everyone has relaxed. Set the timer when you push the dose.

And re-verify while treating: repeat K⁺ (rules out a hemolyzed first sample and tracks response), continuous monitoring with the 12-lead compared against the strip, and watch the urine — the bolus’s report card is the Foley bag.

Improving: the EKG normalized (the goal that mattered), potassium trending down, and — most importantly — urine flowing, which means the prerenal insult is reversing and his kidneys can finish the job the medications started.

Temporary and worth saying out loud at handoff: the insulin/albuterol shift wears off in hours — potassium can rebound, so serial levels continue; glucose checks continue; the creatinine needs days to declare whether this was pure prerenal or earned some tubular injury.

The teaching that prevents the readmission: sick-day rules — when vomiting/diarrhea hits, hold the ACE inhibitor, spironolactone, and NSAIDs and call; no more around-the-clock naproxen with his kidneys and heart failure (gout needs a safer plan); which meds restart, when, and who decides; and the salt-substitute warning (most are potassium chloride). His pharmacist and PCP both need this story.