Hyponatremia Workup And Treatment With Drug Dosing And Adverse Effects

Authored by Eric Kowalchyk, published on 2026-09-14 22:05:49.0

  1. Assess Neurologic Symptoms, Chronicity, Volume Status, and ODS Risk
    • Severe Symptoms or Significant Neurologic Manifestations Attributable to Hyponatremia?
      • Give 3% Sodium Chloride 100 mL IV Over 10 Minutes → Reassess Symptoms and Serum Sodium → Repeat Up to Twice as Needed Until Symptoms Improve or Na⁺ Rises 4–6 mmol/L
        • Repeat Sodium; Obtain Serum Osmolality, Glucose, K, Creatinine, Urine Osmolality, and Urine Sodium
          • Is Serum Osmolality Below 275 mOsm/kg?
            • Treat Hyperglycemia or Osmotic Shift; Confirm Pseudohyponatremia With Direct ISE
            • Is Urine Osmolality 100 mOsm/kg or Lower?
              • Stop Excess Free Water; Restore Dietary Protein and Solute Cautiously
                • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                  High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                  • High ODS risk: ≤8 mmol/L/24 h
                    • Has the Applicable Correction Ceiling Been Exceeded?
                      High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                      • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                        Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                      • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                  • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                    • Has the Applicable Correction Ceiling Been Exceeded?
                      High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                      • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                        Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                      • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
              • Check Urine Sodium: ≤30 mmol/L Suggests Low Effective Arterial Volume
                • Assess Volume Status, Diuretic Use, Renal Function, Cortisol ± TSH
                  • Stop Causative Losses/Diuretics; Restore Volume With 0.9% Sodium Chloride; Reassess Serum Na and Volume Status
                    • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                      High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                      • High ODS risk: ≤8 mmol/L/24 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                      • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                  • Adrenal Insufficiency: Start Glucocorticoids ± IV Saline; Crisis: Hydrocortisone 100 mg IV, Then 50 mg Every 6 Hours
                    • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                      High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                      • High ODS risk: ≤8 mmol/L/24 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                      • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                  • Clinically Significant Hypothyroidism: Start Levothyroxine After Excluding or Treating Adrenal Insufficiency
                    • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                      High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                      • High ODS risk: ≤8 mmol/L/24 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                      • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                  • Restrict Fluids to 1–1.5 L/Day; Treat Congestion and Underlying Heart, Liver, or Kidney Disease
                    • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                      High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                      • High ODS risk: ≤8 mmol/L/24 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                      • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                  • Stop Causative Drugs; Restrict Fluids to 800–1,000 mL/Day and Increase Protein
                    • Persistent Clinically Significant SIADH Despite Fluid Restriction?
                      • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                        High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                        • High ODS risk: ≤8 mmol/L/24 h
                          • Has the Applicable Correction Ceiling Been Exceeded?
                            High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                            • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                              Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                            • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                        • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                          • Has the Applicable Correction Ceiling Been Exceeded?
                            High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                            • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                              Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                            • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                      • Select Second-Line SIADH Therapy Based on Patient Factors
                        • Generally Preferred: Start Oral Urea 15 g Twice Daily
                          • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                            High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                            • High ODS risk: ≤8 mmol/L/24 h
                              • Has the Applicable Correction Ceiling Been Exceeded?
                                High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                                • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                  Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                                • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                            • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                              • Has the Applicable Correction Ceiling Been Exceeded?
                                High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                                • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                  Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                                • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                        • Selected Hospitalized or Refractory SIADH: Start Tolvaptan 15 mg Daily
                          • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                            High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                            • High ODS risk: ≤8 mmol/L/24 h
                              • Has the Applicable Correction Ceiling Been Exceeded?
                                High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                                • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                  Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                                • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                            • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                              • Has the Applicable Correction Ceiling Been Exceeded?
                                High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                                • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                  Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                                • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
      • Repeat Sodium; Obtain Serum Osmolality, Glucose, K, Creatinine, Urine Osmolality, and Urine Sodium
        • Is Serum Osmolality Below 275 mOsm/kg?
          • Treat Hyperglycemia or Osmotic Shift; Confirm Pseudohyponatremia With Direct ISE
          • Is Urine Osmolality 100 mOsm/kg or Lower?
            • Stop Excess Free Water; Restore Dietary Protein and Solute Cautiously
              • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                • High ODS risk: ≤8 mmol/L/24 h
                  • Has the Applicable Correction Ceiling Been Exceeded?
                    High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                    • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                      Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                    • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                  • Has the Applicable Correction Ceiling Been Exceeded?
                    High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                    • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                      Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                    • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
            • Check Urine Sodium: ≤30 mmol/L Suggests Low Effective Arterial Volume
              • Assess Volume Status, Diuretic Use, Renal Function, Cortisol ± TSH
                • Stop Causative Losses/Diuretics; Restore Volume With 0.9% Sodium Chloride; Reassess Serum Na and Volume Status
                  • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                    High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                    • High ODS risk: ≤8 mmol/L/24 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                    • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                • Adrenal Insufficiency: Start Glucocorticoids ± IV Saline; Crisis: Hydrocortisone 100 mg IV, Then 50 mg Every 6 Hours
                  • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                    High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                    • High ODS risk: ≤8 mmol/L/24 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                    • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                • Clinically Significant Hypothyroidism: Start Levothyroxine After Excluding or Treating Adrenal Insufficiency
                  • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                    High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                    • High ODS risk: ≤8 mmol/L/24 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                    • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                • Restrict Fluids to 1–1.5 L/Day; Treat Congestion and Underlying Heart, Liver, or Kidney Disease
                  • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                    High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                    • High ODS risk: ≤8 mmol/L/24 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                    • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                      • Has the Applicable Correction Ceiling Been Exceeded?
                        High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                        • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                          Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                        • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                • Stop Causative Drugs; Restrict Fluids to 800–1,000 mL/Day and Increase Protein
                  • Persistent Clinically Significant SIADH Despite Fluid Restriction?
                    • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                      High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                      • High ODS risk: ≤8 mmol/L/24 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                      • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                        • Has the Applicable Correction Ceiling Been Exceeded?
                          High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                          • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                            Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                          • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                    • Select Second-Line SIADH Therapy Based on Patient Factors
                      • Generally Preferred: Start Oral Urea 15 g Twice Daily
                        • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                          High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                          • High ODS risk: ≤8 mmol/L/24 h
                            • Has the Applicable Correction Ceiling Been Exceeded?
                              High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                              • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                              • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                          • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                            • Has the Applicable Correction Ceiling Been Exceeded?
                              High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                              • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                              • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                      • Selected Hospitalized or Refractory SIADH: Start Tolvaptan 15 mg Daily
                        • Check Serum Sodium Every 2–4 Hours During Active Correction; Adjust Frequency Once Stable
                          High ODS risk includes very low starting sodium, especially Na ≤105 mmol/L, hypokalemia, alcohol use disorder, malnutrition, or advanced liver disease. Replace potassium and track urine output during active correction.
                          • High ODS risk: ≤8 mmol/L/24 h
                            • Has the Applicable Correction Ceiling Been Exceeded?
                              High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                              • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                              • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
                          • Standard risk: ≤10–12 mmol/L/24 h and ≤18 mmol/L/48 h
                            • Has the Applicable Correction Ceiling Been Exceeded?
                              High ODS risk: do not exceed an 8 mmol/L sodium rise in any 24 hours. Standard ODS risk: avoid a rise above 10–12 mmol/L in 24 hours or above 18 mmol/L in 48 hours.
                              • Stop Active Correction; Give Desmopressin 2–4 mcg IV Every 8 Hours ± D5W to Halt or Reverse Overcorrection; Monitor Na Frequently
                                Stop hypertonic saline and other active sodium-raising therapy. Give desmopressin 2–4 mcg IV or SC every 6–8 hours to halt water diuresis; add D5W at approximately 3 mL/kg/hour when sodium must be relowered, titrating to return below the applicable correction ceiling. Check serum sodium every 2 hours during rescue, monitor urine output closely, and adjust or stop D5W once the relowering goal is reached.
                              • Continue Etiology-Directed Therapy; Space Sodium Checks After Stable for 24–48 Hours
  2. Prevent Osmotic Demyelination and Hypertonic Saline Toxicity
    High ODS risk includes sodium ≤105 mmol/L, alcohol use disorder, malnutrition, advanced liver disease, and hypokalemia. Target an initial 4–6 mmol/L rise. Limit correction to 8 mmol/L per 24 hours when ODS risk is high; at standard risk, avoid more than 10–12 mmol/L in 24 hours or 18 mmol/L in 48 hours. Hypertonic saline may cause volume overload, phlebitis, hypernatremia, and rapid overcorrection.
  3. Know Urea and Tolvaptan Toxicities
    Urea may cause nausea, diarrhea, dysgeusia, and increased BUN; titrate within approximately 15–60 g/day to the sodium response. Tolvaptan may cause thirst, polyuria, hypernatremia, rapid correction, hypotension, and liver injury. Initiate in hospital, avoid strong CYP3A inhibitors, anuria, hypovolemia, inability to drink, and underlying liver disease, and limit use to 30 days. Major guidelines disagree about routine vaptan use; reserve it for selected resistant SIADH with specialist oversight. Avoid demeclocycline and lithium.
  4. Know Loop Diuretic and Glucocorticoid Toxicities
    For clinically important congestion, a loop-naive adult may receive furosemide 20–40 mg IV; use a higher dose based on prior loop exposure. Monitor urine output, blood pressure, K, Mg, and creatinine because hypovolemia, AKI, hypokalemia, and hypomagnesemia may occur. Hydrocortisone can cause hyperglycemia, fluid retention, delirium, and infection risk; give glucocorticoid before thyroid hormone when adrenal insufficiency is possible.
  5. Avoid Isotonic Saline as Routine SIADH Treatment
    When urine remains concentrated, isotonic saline may be excreted while retained water worsens hyponatremia. Do not routinely add salt tablets plus a loop diuretic; efficacy is limited and AKI or hypokalemia may occur.
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