Objective: Assess optimal equation to noninvasively estimate intracranial pressure (eICP) and cerebral perfusion pressure (eCPP) following severe traumatic brain injury (TBI) using transcranial color-coded duplex sonography (TCCDS).
Design and setting: This is an observational clinical study in a university hospital.
Patients: A total of 45 continuously sedated (BIS < 50), normoventilated (paCO(2) > 35 mmHg), and non-febrile TBI patients.
Methods: eICP and eCPP based on TCCDS-derived flow velocities and arterial blood pressure values using three different equations were compared to actually measured ICP and CPP in severe TBI patients subjected to standard treatment. Optimal equation was assessed by Bland-Altman analysis.
Results: The equations: ICP = 10:927 x PI(pulsatility index) - 1:284 and CPP = 89:646 - 8:258 PI resulted in eICP and eCPP similar to actually measured ICP and CPP with eICP 10.6 +/- 4.8 vs. ICP 10.3 +/- 2.8 and eCPP 81.1 +/- 7.9 vs. CPP 80.9 +/- 2.1 mmHg, respectively. The other two equations, eCPP = (MABP x EDV)/mFV + 14 and eCPP = mFV / (mFV - EDV)] x (MABP - RRdiast), resulted in significantly decreased eCPP values: 72.9 +/- 10.1 and 67 +/- 19.5 mmHg, respectively. Superiority of the first equation was confirmed by Bland-Altman revealing a smallest standard deviations for eCPP and eICP.
Conclusions: TCCDS-based equation (ICP = 10.927 x PI - 1.284) allows to screen patients at risk of increased ICP and decreased CPP. However, adequate therapeutic interventions need to be based on continuously determined ICP and CPP values.