Division of Neurosurgery

Department of Clinical Neurosciences

About ICM+

ICM Screenshot

Introduction

In an established environment of Clinical Neuroscience Department enormous quantities of data can be captured from each patient from which information regarding cerebral autoregulation, cerebrospinal compensatory reserve, oxygenation, metabolite production and function can be obtained [11,12,13]. Recognition of changing cerebrovascular haemodynamics and oxygenation demands not only reliable monitoring techniques, but also sophisticated and time consuming signal analysis. This can be provided by dedicated computer support.

History

The first specialised computer-based systems for neurointensive care were introduced at the beginning of the 1970s. Initially these systems were oriented to the monitoring of ICP and ABP allowing calculation of CPP and a basic analysis of the pulsatile ICP waveform. In contrast, contemporary systems are highly sophisticated multi-channel digital trend recorders with built-in options for complex signal processing [3,21,28]. The considerable flexibility of such systems allows almost unlimited signal analysis, which can generate a state of data chaos. Thus the modern user is faced with the problem of which parameters should be considered, and how the data should be interpreted. This information should then be presented in a manner that is comprehensible to medical and nursing staff. The mechanism of presentation is also important. Although personal computers with designated software are portable, they have yet to gain widespread clinical acceptance as an intensive care tool. They are seen as stand alone instruments requiring specialised skills for their operation, and occupying precious space. In contrast a commercial hardware system with a customised console can be more user-friendly, but will be less flexible and certainly more expensive.

The intensive care multimodality monitoring system adopted in the Cambridge Neurosurgical Unit is based on software for the standard IBM compatible personal computer, equipped with a digital to analogue converter and RS232 serial interface. First version of the software was introduced into clinical practice in Poland, Denmark and the UK in the middle 1980s and has subsequntly been extended into a system for multimodal neuro-intensive care monitoring (ICM) and waveform analysis of intracranial pressure [3,21] used in Cambridge UK and other centres in Europe (Copenhagen [1], Goteborg [26], Toulouse) and United States (Detroit). Most data has been derived from head injured [6,27] and hydrocephalus patients [5]. However, the same or similar techniques are being increasingly applied to those suffering from severe stroke, subarachnoid haemorrhage, cerebral infections, encephalopathy, liver failure, benign intracranial hypertension, etc.

Apart from monitoring of multiple variables [12], describing dynamics of the studied pathology, some secondary indices have proved to be useful in clinical neurosciences[15]. The best known example is the cerebral perfusion pressure, calculated as a difference between mean arterial pressure and ICP. More sophisticated indices describing cerebrospinal compensatory reserve, pressure autoregulation and vascular reactivity were introduced to clinical practice recently and proved to be useful in head injury [4,12] or poor grade subarachnoid haemorrhage [14]. Carbon-dioxide or acetozolamide reactivity indices are good descriptors of haemodynamic reserve in patients with carotid artery stenotic disease [10,17,20]. Transient-hyperaemic response is a simple test of cerebral autoregulation used in patients after subarachnoid haemorrghage [14]. Analysis of cerebrospinal fluid circulatory and compensatory reserves was used in hydrocephalic patients for at least few decades. It aids decision abut shunting and also helps in objective detection of shunt failure, needing revision. This method has been refined in form of so-called computerized infusion test with built in data-base derived from the UK Shunt Evaluation Laboratory, valuable in shunt testing in-vivo [7,8,9].
Overnight ICP monitoring to detect abnormal CSF dynamics (hydrocephalus, pseudotumor cerebri, cranistenosis) has been supplemented by automatic analysis of B waves of ICP, waveform assessment of pulse wave and respiratory wave.

Our Software

All these, already documented methodologies, are incorporated in the new software as pre-defined set up configurations. On top of this, performance of the software may be programmed and new form of analysis may be added by the user. Flexibility of the software is therefore virtually unlimited.