Multimodal neuromonitoring
Indications
Categories
Direct signals which are monitored invasively:
Intracranial pressure (ICP)
Cerebral regional tissue oxygenation
Microdialysis, parenchymal blood flow, etc.);
Variables which may be monitored noninvasively
Transcranial Doppler (TCD)
Near-infrared spectroscopy (NIRS)
variables describing brain pathophysiology which are not monitored directly but are calculated at the bedside by dedicated computer software. The simplest example is the cerebral perfusion pressure (CPP)
More sophisticated examples include various indices of vascular reactivity or cerebral autoregulation 1) , brain compensatory reserve 2) , vascular resistances, and brain compartmental compliances 3).
Hummingbird neuromonitoring Synergy is a novel single-port access device for multimodal intracranial monitoring that can be placed safely at the bedside or in the operating room with placement accuracy and has a complication profile similar to or better than that for standard external ventricular drains 4).
Multimodality monitoring of cerebral physiology encompasses the application of different monitoring techniques and integration of several measured physiologic and biochemical variables into assessment of brain metabolism, structure, perfusion, and oxygenation status.
Intracranial pressure monitoring is now widely used in neurosurgical critical patients. Besides mean ICP value, the ICP derived parameters such as ICP waveform, amplitude of pulse (AMP), the correlation of ICP amplitude and ICP mean (RAP), pressure reactivity index (PRx), ICP and arterial blood pressure (ABP) wave amplitude correlation (IAAC), and so on, can reflect intracranial status, predict prognosis, and can also be used as guidance of proper treatment. However, most of the clinicians focus only on the mean ICP value while ignoring these parameters because of the limitations of the current devices. We have recently developed a multimodality monitoring system to address these drawbacks. This portable, user-friendly system will use a data collecting and storing device to continuously acquire patients' physiological parameters first, i.e., ABP, ICP, and oxygen saturation, and then analyze these physiological parameters. We hope that the multimodality monitoring system will be accepted as a key measure to monitor physiological parameters, to analyze the current clinical status, and to predict the prognosis of the neurosurgical critical patients 5).
Techniques
Novel monitoring techniques include transcranial Doppler ultrasonography, neuroimaging, intracranial pressure, cerebral perfusion, and cerebral blood flow monitors, brain tissue oxygen tension monitoring, microdialysis, evoked potentials, and continuous electroencephalogram. Multimodality monitoring enables immediate detection and prevention of acute neurologic injury as well as appropriate intervention based on patients' individual disease states in the neurocritical care unit. Real-time analysis of cerebral physiologic, metabolic, and cardiovascular parameters simultaneously has broadened knowledge about complex brain pathophysiology and cerebral hemodynamics. Integration of this information allows for more precise diagnosis and optimization of management of patients with brain injury 6).
Case series
In a study Bailey et al., examined the safety and reliability of multimodality monitoring.
Five hundred and one patients, including 300 males and 201 females (mean age 58 + 39 years) were identified retrospectively from a prospective observational database at a Level I Trauma Center. Each patient received a triple lumen bolt and 3 monitors: intracranial pressure, brain temperature and brain oxygen (Licox, Integra NeuroSciences). ICU and hospital records were examined to identify complications, reasons for device replacement, malfunction and infection. Head CT scans obtained both before and after the monitors were inserted, were examined for evidence of monitor-related adverse effects.
A total of 696 triple lumen bolts were placed. The median (IQR) duration of monitoring was 78.88 hours (33.0-133.2). Twenty-two (3.16%) patients had bilateral monitors. Ten (1.43%) monitors were replaced to allow MR imaging and 40 (5.74%) were replaced to facilitate additional cranial surgery. Thirty-five (5.02%) monitors were replaced because they were thought to not be functioning properly; among these, 19 (54.29%) were subsequently found to be functioning normally. Follow up CT scans were compared with pre-insertion CT scans: 9 (2.13%) small contusions and 10 (2.36%) extra-axial hematomas associated with the devices were identified. Based on the CT findings, the hematomas were thought to be associated with the insertion technique rather than the device. Four hematomas required treatment. Twenty-two (3.16%) devices were incorrectly placed, e.g. the probe was in an infarct or an already existing contusion. Only 1 associated infection was identified.
Placement of intracranial monitors for multimodality neuromonitoring using a triple lumen bolt appears to be safe. The complication rate is similar to that published for single-lumen bolts and single monitors 7).
included 43 consecutive sTBI patients who required MMM to guide clinical care based on institutional protocol and had a four-lumen bolt placed to measure intracranial pressure, brain tissue oxygen, regional cerebral blood flow, brain temperature, and intracranial electroencephalography.
RESULTS: sTBI patients were aged 41.6 ± 17.5 years (mean ± SD) and 84% were men. MMM devices were placed at a median of 12.5 h (interquartile range [IQR] 9.0-21.4 h) after injury and in non-dominant frontal lobe in 72.1% of cases. Monitoring was conducted for a median of 97.1 h (IQR 46.9-124.6 h) per patient. While minor hemorrhage, pneumocephalus, or small bone chips were common, only one (2.4%) patient experienced significant hemorrhage related to device placement. Radiographically, device malpositioning was noted in 13.9% of patients. Inadvertent device discontinuation occurred for at least one device in 58% of patients and was significantly associated with the frequency of travel for procedures or imaging. Devices remained in place for > 80% of the total monitoring period and generated usable data > 50% of that time.
CONCLUSIONS: A standardized, bedside single burr hole approach to MMM was safe. Despite some probe-specific recording limitations, MMM provided real-time measurements of intracranial pressure, oxygenation, regional cerebral blood flow, brain temperature, and function 8).