Does Adrenaline Decrease Pulmonary Vascular Resistance?
No, epinephrine (adrenaline) does not decrease pulmonary vascular resistance—it increases both pulmonary artery pressure and pulmonary vascular resistance. 1
Direct Evidence from Guidelines
The most authoritative evidence comes from the 2018 Intensive Care Medicine guideline on vasoactive agents in shock, which explicitly states: "Norepinephrine and epinephrine similarly increase pulmonary artery pressure and pulmonary vascular resistance with little effects on pulmonary capillary wedge pressure." 1 This represents the consensus expert opinion on epinephrine's pulmonary vascular effects.
Mechanism and Dose-Dependent Effects
Epinephrine's effects on pulmonary vasculature are complex and dose-dependent:
At low doses (<0.3 mcg/kg/min): Epinephrine primarily exerts β-adrenergic effects, which can cause systemic vasodilation through β2-receptor activation 2. However, even at these doses, the pulmonary circulation responds differently than systemic circulation.
At higher doses (>0.3 mcg/kg/min): α-adrenergic vasoconstriction predominates, further increasing pulmonary vascular resistance 2.
Alpha-receptor mediated effects: Research demonstrates that epinephrine increases pulmonary vascular resistance through α1- and α2-receptor stimulation, with precapillary α1- and α2-receptors and postcapillary α2-receptors causing vasoconstriction 3.
Clinical Context: When Epinephrine May Be Used Despite Increasing PVR
While epinephrine increases PVR, it may still be considered in specific clinical scenarios:
In right ventricular failure with pulmonary hypertension, epinephrine is listed among inotropes that have "neutral or beneficial effects on PVR" alongside dobutamine and milrinone 4. However, this statement is misleading—the benefit comes from improved cardiac output and systemic pressure, not from reducing PVR.
The critical principle: Maintain systemic vascular resistance (SVR) greater than pulmonary vascular resistance (PVR) to preserve right ventricular coronary perfusion 4. If systolic pulmonary artery pressure exceeds systolic systemic arterial pressure, right ventricular ischemia occurs.
Pediatric Evidence
A 2016 pilot study in children with pulmonary hypertension showed that epinephrine (1 mcg/kg bolus) decreased the ratio of pulmonary-to-systemic vascular resistance in only 3 of 5 patients 5. This inconsistent response occurred because epinephrine increased systemic pressure more than pulmonary pressure in some patients, not because it reduced PVR.
Vasopressin performed better in this study, consistently decreasing the PVR/SVR ratio in 5 of 5 patients by selectively increasing systemic vascular resistance without pulmonary vasoconstriction 5.
Alternatives That Actually Decrease PVR
If your goal is to reduce pulmonary vascular resistance:
- Inhaled pulmonary vasodilators: Nitric oxide (5-10 ppm) or inhaled prostacyclin (20-30 ng/kg/min) reduce PVR without systemic hypotension 6
- Dobutamine: Decreases both systemic and pulmonary vascular resistance through β-receptor effects 1
- Phosphodiesterase III inhibitors (milrinone): Reduce PVR but risk hypotension 1
- Levosimendan: May decrease PVR and improve right ventricular function when pulmonary artery pressure is elevated 1
Common Pitfall
Do not confuse improved hemodynamics with reduced PVR. Epinephrine may improve cardiac output and systemic blood pressure in shock states, which can secondarily benefit right ventricular function. However, this occurs despite increased PVR, not because of decreased PVR. The FDA label confirms epinephrine causes "peripheral vasoconstriction" affecting "most vascular beds including renal, splanchnic, mucosal and skin" 7, and the pulmonary circulation is no exception.