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#Comprehensive Notes

##I. Overview

Focus: 6 electrolytes + 4 acid–base disorders

Goal: Know one classic sign + one lifesaving intervention for each

NCLEX weight: High (8–16 questions across categories)

Foundational rule: Always assess volume status first — dry vs overloaded guides almost every intervention

II. Sodium

A. Hyponatremia

Classic sign: seizures (especially when levels plunge)
Why: water shifts into brain → swelling → seizure risk
Lifesaving action: 3% hypertonic saline, rapid bolus for active seizure
Additional pearls:

Chronic hyponatremia (e.g., “tea and toast” elderly patient): correct slowly to prevent osmotic demyelination syndrome

Limit correction to 6–8 points in 24 hours once stable

B. Hypernatremia

Classic sign: intense thirst + confusion
Why: brain cells shrink from dehydration
Lifesaving action: give free water (D5W IV, oral, or tube)
Rule: correct slowly to prevent cerebral edema

III. Potassium

A. Hypokalemia

Classic sign: U-waves on ECG
Lifesaving action: potassium replacement
Safety rules:

Never exceed 10–20 per hour through a peripheral line

Oral preferred

Replace magnesium first—low magnesium prevents potassium correction

B. Hyperkalemia

The most urgent electrolyte emergency

Classic sign: tall peaked T-waves → wide QRS → sine-wave → cardiac arrest

Three-step lifesaver sequence:

Stabilize: calcium gluconate protects myocardium

Shift: insulin + dextrose (or high-dose albuterol) moves potassium into cells

Remove: kayexalate, loop diuretics, or dialysis

IV. Calcium & Magnesium

A. Hypocalcemia

Classic signs:

Chvostek sign (facial twitch with cheek tap)

Trousseau sign (carpal spasm with BP cuff)

Lifesaving action: slow IV calcium gluconate
Risk of fast push: bradycardia, severe hypotension

B. Hypermagnesemia

Often renal failure or magnesium infusions

Classic signs:

Profound hypotension

Loss of deep tendon reflexes (areflexia)

Lifesaving action:

Stop magnesium

Give calcium gluconate to counteract cardiac depression

V. Acid–Base Disorders

Interpretation Rule:

pH + bicarbonate same direction → metabolic

pH + CO₂ opposite directions → respiratory

Clinical principle:

Treat the patient before the number
Volume status affects everything.

A. Respiratory Acidosis

Cause: CO₂ retention from hypoventilation (opioids, COPD flare)
Signs: sleepiness, poor arousal
Lifesaving action: improve ventilation — stimulate, bilevel support, or intubate

B. Respiratory Alkalosis

Cause: hyperventilation (pain, anxiety, early sepsis, PE)
Signs: tingling around mouth and fingers, lightheaded
Lifesaving action: treat cause — calm anxiety, treat PE, manage pain

C. Metabolic Acidosis

Classic sign: Kussmaul respirations (deep, rapid breathing)
DKA clue: fruity acetone breath

Mnemonic for causes: MUDPILES

Methanol

Uremia

DKA

Propylene glycol

Iron

Lactic acidosis

Ethylene glycol

Salicylates

Lifesaving action: treat underlying cause

DKA → insulin

Lactic acidosis → fix shock
Give bicarbonate only when pH < 7.1 and patient is crashing.

D. Metabolic Alkalosis

Cause: loss of stomach acid (vomiting, NG suction)
Often causes: secondary low potassium

Lifesaving action: normal saline + potassium

Chloride allows kidneys to excrete excess bicarbonate

Potassium replaces losses
Consider acetazolamide in severe cases.

VI. Practice Scenarios (High-Yield NCLEX Style)

1. Vomiting × 3 days

pH high + bicarbonate high → metabolic alkalosis
Interventions: normal saline + potassium; consider acetazolamide

2. Severe DKA

pH extremely low + bicarbonate low → metabolic acidosis
First action: start regular insulin infusion

3. Chronic COPD

pH low + CO₂ high + bicarbonate high → partially compensated respiratory acidosis

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