Continuous Versus Bolus Norepinephrine Administration to Treat Postinduction Hypotension

Hypotension after induction of general anesthesia, referred to as postinduction hypotension, is common in patients having non-cardiac surgery and is associated with acute kidney injury. Risk factors for postinduction hypotension include older age, higher American Society of Anesthesiologists physical status, chronic arterial hypertension - and higher doses of vasodilating anesthetic drugs. It is reasonable to assume that careful anesthetic management can help maintain blood pressure stability and limit postinduction hypotension. Consistent with this assumption, continuous blood pressure monitoring with an arterial catheter during induction of general anesthesia helps clinicians reduce postinduction hypotension - and is thus recommended in non-cardiac surgery patients at risk for hypotension-related complications.

Besides continuous monitoring, anesthesiologists routinely give vasopressors - such as norepinephrine - to maintain blood pressure. Norepinephrine is a fast acting vasopressor with a short half-life and is usually given as repeated manual boluses during induction of general anesthesia. Given as a bolus, it effectively and rapidly increases blood pressure. However, boluses need to be frequently repeated and well-timed to ensure blood pressure stability.

In a single-center randomized trial, we demonstrated that continuous - compared to bolus - administration of norepinephrine during induction of general anesthesia helps maintain blood pressure stability in high-risk non cardiac surgery patients. We now aim to test the hypothesis that continuous - compared to bolus - administration of norepinephrine during induction of general anesthesia reduces postinduction hypotension in high-risk non-cardiac surgery patients who have continuous blood pressure monitoring with an arterial catheter.

Inclusion criteria

We will include consenting patients ≥45 years scheduled for elective non-cardiac surgery under general anesthesia with planned continuous intra-arterial blood pressure monitoring with a radial arterial catheter and with at least two of the following risk criteria for developing acute kidney injury:

• Age ≥65 years
• ASA physical status III or IV
• Chronic arterial hypertension
• Diabetes mellitus requiring medication
• Intra-abdominal surgery
• Preoperative renal insufficiency (serum creatinine ≥1.2 mg/dL)

Exclusion criteria

• Pregnancy
• Cardiac arrhythmia
• History of intracranial hemorrhage or intracranial aneurysm
• Clinical indication for continuous norepinephrine infusion during induction of general anesthesia (e.g., severe aortic valve stenosis, coronary artery disease, or heart failure)
• Patients who are unable to understand, read, and provide informed consent in German