The following is a summary of “Micro- and macrocirculatory effects of norepinephrine on anaesthesia-induced hypotension: a prospective preliminary study,” published in the November 2023 issue of Critical Care by Kindermans et al. 

The occurrence of intraoperative arterial hypotension (IOH) frequently contributes to heightened postoperative complications. Norepinephrine often serves as a primary intervention to manage IOH. However, the optimal mode of administering norepinephrine, whether via bolus or continuous infusion, remains uncertain. This study aims to delineate and compare the effects of bolus and constant norepinephrine infusion on macrocirculatory and microcirculatory functions when addressing IOH.

A prospective observational study was conducted involving adult patients undergoing neurosurgery. Eligibility criteria included patients with invasive arterial blood pressure and cardiac output (CO) monitoring. Microcirculation monitoring comprised video-capillaroscopy, laser Doppler, near-infrared spectroscopy technology, and tissular CO2 measurements. In instances of IOH, patients received either a bolus of 10 µg or a continuous infusion of 200 µg/h of norepinephrine. Comparative analyses between bolus and continuous infusion were focused on the peak of mean arterial pressure (MAP). The primary outcome measure was the Microvascular Flow Index (MFI) assessed through videocapillaroscopy.

A total of 35 patients were included, comprising 41 bolus administrations and 33 continuous infusions. Both bolus and continuous infusion of norepinephrine exhibited a maximal increase in mean arterial pressure, demonstrating increments of +30[20-45] % and +23[12-34] %, respectively (P=0.07). In terms of macrocirculatory parameters, continuous infusion demonstrated a lesser decrease in cardiac output and stroke volume (p<0.05).

Regarding microcirculatory parameters, there were notable discrepancies in response between bolus and continuous infusion. The microvascular flow index, perfusion index, and total vessel density displayed significant opposite variations with bolus and continuous infusion, highlighting dissimilar impacts on microcirculation.

In conclusion, these findings emphasize the potential advantages associated with continuous infusion of norepinephrine over bolus administration in managing anesthesia-induced hypotension, particularly in relation to both macrocirculatory and microcirculatory responses.

Source: bmcanesthesiol.biomedcentral.com/articles/10.1186/s12871-023-02342-3