Perfusion index and mean arterial pressure after return of spontaneous circulation in out-of hospital cardiac arrest (OHCA) and their relationship with perfusion and survival
Authors: Fasolino A , Bagliani A , Benjelloun L , Baldi E , Contri E , Vecchione A , Quilico F , Ambrosini E , Primi R , Currao A , Bendotti S , Palo A , Malinverni S , Tavazzi G , Savastano S 
Published: May 2024

Abstract

Funding Acknowledgements
None.

Background
Current guidelines for post-cardiac arrest care recommend targeting mean arterial pressure (MAP) to restore adequate perfusion indicated by adequate urine output (UO) and normal or decreasing lactate, avoiding hypotension (MAP &lt; 65 mmHg). The peripheral perfusion index (PI) is the ratio of the pulsatile blood flow to the non-pulsatile blood flow measured peripherally by a standard pulse-oximeter, and it represents a promising non-invasive tool to assess perfusion. The goal of this study is to assess whether prehospital PI and MAP measurements are associated with lactate clearance (LC), adequate UO and 30-days survival with good neurological outcome.

Methods
A retrospective analysis of prospectively collected data (January 2018 - March 2023) in two cardiac arrest registries located in Italy and Belgium was performed. PI was automatically and continuously measured by the manual monitor/defibrillator. The mean PI value of each minute after ROSC was extracted from the monitor data report and the mean value of 30 min of PI monitoring (MPI30) was calculated and categorized in tertiles (MPI30 T1-T3). The lowest prehospital value for MAP recording was considered. LC was defined by a serum lactate level &lt;2 mmol/L at 6 hours. Inadequate UO was defined as &lt; 0.5mL/kg/h averaged at 12 hours. Neurological outcome was assessed with the Cerebral Performance Category (CPC) at 30 days.

Results
Out of the 397 OHCA patients admitted to the ICU after ROSC enrolled over the study period 206 had a MPI30 value available and were included in this study; MAP value was available in 186 patients. In the subgroup of patients with hypotension, patients with MPI30 in T1 showed higher incidence of inadequate UO at 12 hours (78.9% vs 25.8%, p&lt;0.001). At multivariable logistic regression, after adjusting for MAP, shockable rhythm, age, and dosage of adrenaline administered, MPI30 was independently associated with inadequate UO (OR 0.68, 95% CI 0.50-0.91, p=0.01). Patients with hypotension and MPI30 in T1 showed lower LC at 6h (15.8% vs 43.4%, p=0.02) when compared to the remaining population. At multivariable Cox proportional-hazard regression, after correction for shockable rhythm, age, and total amount of adrenaline administered, patients with hypotension and MPI30 in T1 showed lower survival with CPC 1-2 at 30 days (HR 2.61, 95% CI 1.52-4.51, p=&lt;0.001) when compared to patients without hypotension or with hypotension but MPI30 in T2-T3. No difference in LC, adequate UO and survival with good neurological outcome was found between patients with hypotension and MPI30 in T2-T3 compared to patients without hypotension.

Conclusion
PI is a useful indicator of perfusion in patients with hypotension after OHCA. Patients with hypotension and reduced PI showed higher incidence of inadequate UO and lower incidence of LC, as well as association with lower survival at 30 days with CPC 1-2.Lactate clearenceSurvival at 30days with CPC 1-2