Influence of data resolution and interpolation method on assessment of secondary brain insults in neurocritical care

Continuous monitoring of physiologic vital signs is routine in neurocritical care. However, this patient information is usually only recorded intermittently (most often hourly) in the medical record. It is unclear whether this is sufficient to represent the occurrence of secondary brain insults (SBIs) or whether more frequent data collection will provide more comprehensive information for patient care. In 16 patients, physiologic data were acquired concurrently via two methods: per clinical routine, usually hourly, in the medical record (MR) and every minute via a custom data acquisition system (DA). SBIs were defined as a mean arterial pressure < 90 mmHg, an intracranial pressure > 20 mmHg or a temperature > 37.5 degrees C. Number of events, cumulative duration of events and area under the curve (AUC) were compared between the two methods and 95% limits of agreement were assessed for various methods of MR data interpolation. For all three parameters, analysis of the DA and MR data frequently differed with regard to number of events, total duration of events and AUC. MR data tended to underestimate the number of total events. 95% limits of agreement were most narrow for trapezoidal interpolation of MR data, but even these limits were fairly broad. Assessment of secondary brain insults is highly dependent on (1) the temporal resolution of the method used to acquire patient data and on (2) the interpolation method if data are acquired intermittently. High frequency data acquisition may be necessary for more precise evaluation of secondary brain injury in neurocritical care.