Philip R Judge BVSc MVS PG Cert Vet Stud MACVS (VECC, Medicine of Dogs)
Based on the recent review by Hiroto et al., synthesising current evidence on vasopressor strategies in septic shock, here are 6 key points to apply in clinical practice.
1. Early norepinephrine initiation improves haemodynamic stabilisation and may reduce fluid overload
The Surviving Sepsis Campaign Guidelines 2026 recommend initiating norepinephrine within the first hour of resuscitation when hypotension persists.
The CENSER trial demonstrated that early low-dose norepinephrine significantly shortened the time to achieve target MAP and reduced cardiopulmonary complications compared with delayed initiation.
A recent meta-analysis (Shi et al., 2025) further confirmed associations between early norepinephrine use and decreased mortality, as well as reduced fluid overload.
Early norepinephrine also augments stressed intravascular volume and cardiac preload, which may help limit excessive fluid administration.
2. An initial norepinephrine dose of approximately 0.1 mcg/kg/min is a reasonable starting point in patients with severe hypotension
Many clinical trials initiate norepinephrine at 0.05–0.1 mcg/kg/min. However, a recent high-resolution analysis of ICU data demonstrated that lower starting doses (0.025 or 0.05 mcg/kg/min) appeared insufficient to achieve target MAP within 60 minutes in patients with severe hypotension. Higher initial doses (0.1 mcg/kg/min) were associated with both larger and faster MAP increases. The authors note that sepsis-specific mechanisms impair vasopressor responsiveness, so overly conservative starting doses may delay restoration of adequate perfusion pressure. Administration of norepinephrine at 0.1–0.2 mcg/kg/min has been shown to be safe. The starting dose should be individualised based on the severity of hypotension and underlying cardiovascular conditions.
3. Escalating norepinephrine beyond moderate doses has diminishing returns and increases adverse effects
Vascular responsiveness to norepinephrine diminishes as the baseline dose increases, with a markedly attenuated MAP response observed at doses of 0.3 mcg/kg/min and above in patients with septic shock (Bosch et al., 2023).
High-dose norepinephrine is associated with dysrhythmias (34% of patients in one observational study), with both duration of infusion and maximum dose independently associated with arrhythmic risk. Limb ischaemia and tissue necrosis may necessitate surgical intervention in approximately 50% of patients requiring multiple vasopressors.
These findings suggest a dose-dependent relationship between norepinephrine exposure and harm, supporting a strategy of avoiding continued dose escalation once moderate requirements are reached.
4. Earlier vasopressin initiation at lower norepinephrine doses may be beneficial; emerging evidence suggests around 0.2 mcg/kg/min
Current guidelines recommend initiating vasopressin when norepinephrine requirements reach approximately 0.25–0.50 mcg/kg/min. However, several lines of evidence suggest that earlier initiation may be advantageous:
- In the VASST trial, a survival signal was observed in patients receiving lower baseline norepinephrine doses (<15 mcg/min).
- In the VANISH trial, vasopressin was initiated at a median norepinephrine dose of approximately 0.16 mcg/kg/min and was associated with reduced renal replacement therapy requirements.
- The OVISS reinforcement learning study indicated that optimal strategies favoured vasopressin initiation at a median norepinephrine dose of approximately 0.20 mcg/kg/min, substantially lower than the 0.37 mcg/kg/min observed in clinical practice.
- A recent meta-analysis defining early vasopressin initiation as within 6 hours of septic shock onset demonstrated improved haemodynamic stability and shorter hospital stay compared with delayed or no vasopressin use.
The authors propose that early addition of vasopressin when norepinephrine reaches approximately 0.2 mcg/kg/min represents a physiologically rational strategy, but they emphasise that this remains investigational and has not been confirmed by randomised controlled trials.
5. Vasopressin offers non-adrenergic vasoconstriction and potential renal protective effects, but survival benefit remains unproven
Vasopressin provides vasoconstriction through vascular V1a receptors via a mechanism independent of norepinephrine, which is clinically important in septic shock where vascular hypo-responsiveness to catecholamines can occur.
Additionally, circulating vasopressin levels are inappropriately low in septic shock despite ongoing hypotension, indicating relative vasopressin deficiency. Vasopressin may also preserve renal perfusion by preferentially constricting efferent arterioles and maintaining glomerular filtration rate.
However, randomised trials have not consistently demonstrated survival benefits:
- VASST showed no reduction in 28-day mortality overall, though a potential benefit was observed in less severe shock.
- VANISH found no significant difference in mortality between early vasopressin and norepinephrine strategies, despite lowering requirement for renal replacement therapy.
- An individual patient data meta-analysis (Nagendran et al., 2019) showed no overall survival benefit.
Despite the lack of consistent survival benefit, adjunctive vasopressin is a rational strategy for enhancing haemodynamic stability, reducing catecholamine requirements, and potentially preserving renal perfusion. Non-adrenergic vasopressors as a class have been associated with a reduced risk of renal replacement therapy in meta-analyses.
6. Vasopressin is typically given at a fixed dose of 0.03 U/min without titration to blood pressure targets
In major randomised human trials (VASST and VANISH), vasopressin was administered at a fixed dose of 0.03 U/min. Unlike catecholamines, vasopressin is not typically titrated to blood pressure targets, reflecting its use as a fixed-dose adjunct rather than a primary vasopressor. Higher doses may be associated with increased adverse effects, including ischaemic skin lesions and decreased cardiac output. The dose of 0.03 U/min has been the standard regimen in clinical trials and remains the recommended starting dose.
Final Notes:
- The proposed integrated strategy is:
- Initiate norepinephrine early after fluid resuscitation at a starting dose of approximately 0.1 mcg/kg/min to achieve target MAP (≥65 mmHg).
- Reassess haemodynamic response within 30–60 minutes using both MAP and markers of tissue perfusion.
- If response is inadequate or norepinephrine requirements escalate, consider early addition of vasopressin when the norepinephrine dose reaches approximately 0.2 mcg/kg/min, rather than continuing to escalate norepinephrine alone.
- The article authors emphasise that this strategy is derived exclusively from observational studies, post hoc analyses, and reinforcement learning models.
- Angiotensin II is mentioned as another non-adrenergic option for catecholamine-resistant vasodilatory shock. The ATHOS-3 trial demonstrated that angiotensin II significantly improved MAP in refractory shock, though without proven mortality reduction.
- Careful monitoring during vasopressor therapy should include frequent assessment of infusion sites for extravasation or local ischaemic complications, continuous monitoring of heart rate and rhythm, peripheral perfusion, urine output, lactate concentration, and capillary refill time.
Reference:
Hiroto G, Nishikimi M, Shime N. Optimizing Timing and Dose of Starting Norepinephrine and Vasopressin in Septic Shock. Life. 2026 May 29;16(6):913.
