Dose of Vasopressin per kg
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"vasopressin" AND "septic shock" AND dosing
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Vasopressin Dosing
Vasopressin dosing depends heavily on the clinical indication and the patient's age. Unlike norepinephrine, epinephrine, or dopamine, adult vasopressin infusions are usually dosed as a fixed rate (units/min), not weight-based — this is a key distinction from other vasopressors.
Adults (fixed dose, not weight-based)
| Indication | Dose |
|---|---|
| Septic/vasoplegic shock (adjunct to norepinephrine) | 0.01–0.04 units/min, up to ~0.03–0.04 U/min - Rosen's Emergency Medicine; Goldman-Cecil Medicine; Sabiston Textbook of Surgery |
| Post-cardiac surgery vasoplegia | 0.01–0.05 units/min - Barash, Cullen, and Stoelting's Clinical Anesthesia |
| Cardiac arrest (historical, no longer favored) | 40 units IV push (single fixed dose) - Tintinalli's Emergency Medicine, p. showing no survival benefit over epinephrine |
Pediatrics (weight-based, per kg)
| Indication | Dose |
|---|---|
| General cardiac output/shock support (Harriet Lane Handbook) | 0.17–8 milliunits/kg/min (i.e., 0.00017–0.008 units/kg/min) - The Harriet Lane Handbook, Table 1.5 |
| Upper GI bleeding (when octreotide unavailable) | 0.002–0.005 unit/kg/min, titrated, maximum 0.01 unit/kg/min - Tintinalli's Emergency Medicine |
So if you specifically need a per-kg figure, the pediatric weight-based range is roughly 0.0002–0.01 units/kg/min depending on indication, with the Harriet Lane general range being 0.17–8 milliunits/kg/min. In adults, clinicians typically do not calculate a per-kg dose at all - they run vasopressin at a fixed 0.01–0.04 units/min and titrate to effect.
Note: this is distinct from desmopressin (DDAVP), a different synthetic vasopressin analog used for diabetes insipidus/bleeding disorders, which has its own separate (also weight-based in some indications) dosing - let me know if you meant that drug instead.
Recent systematic reviews (2025-2026, PMIDs 41067173, 39965613, 41039619) focus on timing of vasopressin initiation relative to norepinephrine and renal outcomes in septic shock, not on per-kg dosing revisions, so they don't contradict the dosing above.
Bicarbonate correction formula
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Sodium Bicarbonate Correction Formula
There are a few validated versions, all based on the same principle: NaHCO3 dose (mEq) = bicarbonate space x body weight (kg) x bicarbonate deficit. They differ mainly in what value is used for the "bicarbonate space" (volume of distribution).
1. Base-deficit method (Morgan and Mikhail's Clinical Anesthesiology)
$$\text{NaHCO}_3 (\text{mEq}) = \text{Base Deficit} \times 0.3 \times \text{body weight (kg)}$$
- Uses an estimated HCO3- space of ~30% of body weight (physiologic range 25-60%, widening as acidosis becomes more severe/chronic).
- Worked example: 70-kg man, base deficit -10 mEq/L → NaHCO3 = 10 x 0.3 x 70 = 210 mEq calculated deficit.
- In practice, only 50% of the calculated dose is given (~105 mEq here), then a repeat ABG is drawn before giving more.
- Morgan and Mikhail's, p. 2232
2. Surgical/trauma method (Current Surgical Therapy)
$$\text{Bicarbonate deficit (mEq)} = \tfrac{1}{3} \times \text{body weight (kg)} \times \text{base deficit}$$
- Functionally the same as above (1/3 ≈ 0.3-0.33 x body weight), derived directly from the base deficit on an ABG.
- Current Surgical Therapy, 14e, p. 1609
3. Nephrology method - target-driven (Comprehensive Clinical Nephrology)
$$\text{Bicarbonate deficit (mmol)} = 0.5 \times \text{LBW (kg)} \times (24 - \text{measured HCO}_3^-)$$
- Uses a fixed volume of distribution of 0.5 L/kg lean body weight, and targets a serum HCO3- of 24 mmol/L.
- Caveats: add extra volume for edema fluid; when serum HCO3- is ≤5 mmol/L, the volume of distribution can rise to ≥1 L/kg (so this formula underestimates the deficit in very severe acidosis).
- Give ~50% of the calculated deficit over the first 24 hours, then reassess.
- Comprehensive Clinical Nephrology, 7th ed., p. (ALKALI TREATMENT OF METABOLIC ACIDOSIS section)
4. Empiric fixed dose
Alternatively, many clinicians simply give 1 mEq/kg empirically when arterial pH < 7.20, followed by serial blood gases to titrate further doses (Morgan and Mikhail's).
Practical points common to all methods
- Correct only partially (usually 50% of the calculated deficit) and re-check an ABG before giving more - overcorrection risks overshoot alkalosis, hypernatremia, and volume overload.
- Bicarbonate treats the acidemia, not the underlying cause - identify and treat the cause (sepsis, DKA, toxin, renal failure) simultaneously.
- Routine large-dose NaHCO3 in cardiac arrest/low-flow states is not recommended - it can cause paradoxical intracellular acidosis (CO2 generated crosses cell membranes faster than HCO3- does).
- Goal is usually pH > 7.20-7.25, not full normalization.
If you tell me the specific clinical context (DKA, RTA, cardiac arrest, toxic alcohol ingestion, pediatric case), I can narrow down which formula and target is most appropriate.
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