A subset of patients being treated for actual or potential intracranial pressure (ICP) increases respond to nursing care, such as being positioned or suctioned, with frequent sharp and sustained increases in ICP that threaten adequate cerebral perfusion pressure (CPP). These adverse physiologic responses may reflect impaired craniocerebral compliance due to failing cerebral autoregulation. Advanced bioinstrumentation technology (transcranial Doppler ultrasonography - TCDU - and computerized intracranial pressure waveform analysis - ICPWFA) exists to assess cerebrovascular autoregulation and compliance relatively noninvasively. However these advanced technologies have not been examined simultaneously for their ability to predict cerebrovascular instability, as indicated by adverse ICP/CPP changes in response to necessary care activities.
The specific aims of this study are to: 1) Determine the relationship of a TCDU indictor of autoregulation and an ICPWFA indicator of cerebral compliance to the number of episodes of untoward physiological responses to nursing care, and 2) describe the temporal relationship of TCDU evidence of decreased cerebral autoregulation, altered ICP waveform and elevated intracranial pressure. This is an important step to enhance the bioinstrumentation capabilities of an ongoing program of nursing research aimed at identifying patient care activities that threaten neuronal integrity. The design is prospective, with descriptive and correlational elements. Approximately 60 patients with ICP monitoring and a variety of diagnoses will be monitored continuously during the first 24 hours as part of their routine care, using multichannel TCDU instrumentation that allows simultaneous recording of cerebral blood flow velocity (CBFV), ICP, arterial bloodpressure (ABP) with derivation of spectral CBFV profiles and autoregulatory indices. Data for this study is derived from multichannel continuous TCDU analog and digital records, patient records and bedside monitoring records. Existing software routines for generating Fast Fourier on-line signal transformation of the TCDU cerebral blood flow velocity waveform will be modified to produce the spectral harmonic array and power density function for the ICP waveform, based on modeling the hydraulic transfer function. Continuous ICP, SABP and CBFV monitoring data from a 4-8 hour segment during the first 24-36 hours will be used to compare ICPWFA evidence of decreased compliance and TCDU evidence of decreased cerebral autoregulation to predict multiple episodes DIICP, with frequency of DIICP calculated from clinical monitor trend recordings. The autoregulation score will be regressed on the frequency of DIICP in the subsequent 24 hours to predict this relationship, the R2 values compared for ICPWFA and autoregulation index as predictors.
Aim 2, to compare the temporal relationship of TCDU evidence of decreased cerebral autoregulation, elevated P2 wave and elevated intracranial pressure in the first 24 hours, will be approached using hard copy trend recordings displaying the spectral array CBFV, ICP and SABP using the spectral profiles from the multichannel monitoring period.
