Severe Hypernatremia Management

Algorithm Steps

1. ▶

   Start

   Hypernatremia Detected

   Serum Na >145 mmol/L

   1. ◆

      Decision

      Assess Severity

      Classify hypernatremia

      • Mild: 146-150 mmol/L
      • Moderate: 151-159 mmol/L
      • Severe: ≥160 mmol/L
      • Also assess acuity: Acute (<48h) vs Chronic (≥48h)
      1. ●

         Action

         Clinical Manifestations

         Neurologic symptoms predominate

         • Lethargy, weakness, irritability
         • Altered mental status, confusion
         • Hyperreflexia, spasticity
         • Seizures (usually in acute cases)
         • Coma (severe hypernatremia)
         • Signs of volume depletion if hypovolemic
         1. ◆

            Decision

            Assess Volume Status

            Guides initial fluid choice

            • HYPOVOLEMIC: Tachycardia, hypotension, dry mucosa, poor skin turgor
            • EUVOLEMIC: Normal vitals, often pure water loss
            • HYPERVOLEMIC: Edema, hypertension (iatrogenic Na loading)
            1. ●

               Action

               Hypovolemic Hypernatremia

               Lost water > sodium

               • Causes: GI losses, osmotic diuresis, burns, fever
               • Step 1: Volume resuscitate with 0.9% NS first
               • Step 2: Once stable, switch to 0.45% NS or D5W
               • Replace volume deficit + ongoing losses
               1. ●

                  Action

                  Calculate Free Water Deficit

                  Guide replacement volume

                  • Formula: FWD = TBW × [(Serum Na / 140) - 1]
                  • TBW = Weight (kg) × 0.6 (men) or 0.5 (women)
                  • Example: 70kg male, Na=160: TBW=42L, FWD=42×(160/140-1)=6L
                  • Replace deficit + ongoing losses over 48-72 hours
                  1. ⚠

                     Warning

                     ⚠️ Correction Rate - CRITICAL

                     Avoid cerebral edema from rapid correction

                     • ACUTE (<48h): Can correct 1-2 mmol/L/hr, normalize within 24h
                     • CHRONIC (≥48h): MUST correct slowly
                     • Target: ≤0.5 mmol/L/hr or 8-10 mmol/L/24h maximum
                     • Brain adapts to chronic hypernatremia with organic osmolytes
                     • Rapid correction → water shifts into brain → cerebral edema
                     • Too slow (<0.25 mmol/L/hr, <6 mmol/L/day) also increases mortality
                     1. ●

                        Action

                        Fluid Selection

                        Choose appropriate replacement

                        • D5W: Most hypotonic, for pure water deficit
                        • 0.45% NS: Half normal saline, moderate hypotonicity
                        • 0.9% NS: For initial resuscitation in hypovolemic patients
                        • Oral water: If patient can drink safely
                        • Rate depends on deficit size and target correction
                        1. ●

                           Action

                           Monitoring

                           Close follow-up during correction

                           • Serum Na: q2-4h during active treatment
                           • Urine output and specific gravity
                           • Neurologic status
                           • Adjust infusion rate based on response
                           • Account for ongoing losses
                           1. ●

                              Action

                              Treat Underlying Cause

                              Prevent recurrence

                              • Central DI: Desmopressin intranasal/IV
                              • Nephrogenic DI: Thiazides, NSAIDs, low Na diet
                              • Osmotic diuresis: Control glucose/urea
                              • Access to water: Ensure adequate intake
                           2. ✓

                              Outcome

                              Safe Correction Achieved

                              Na normalized, symptoms improved

                           3. ⚠

                              Warning

                              ICU Admission

                              Severe (Na≥160) or symptomatic cases

            2. ●

               Action

               Euvolemic Hypernatremia

               Pure water loss

               • Causes: Diabetes insipidus (central or nephrogenic), insensible losses
               • Treatment: Free water replacement
               • D5W or 0.45% NS IV
               • If DI: Desmopressin for central DI, thiazides for nephrogenic DI
            3. ●

               Action

               Hypervolemic Hypernatremia

               Sodium excess

               • Causes: Hypertonic saline, NaHCO3, salt tablets, mineralocorticoid excess
               • Treatment: D5W + Loop diuretics
               • Remove sodium while replacing water
               • Consider dialysis if severe