An induced coma is a temporary state of unconsciousness brought on by a controlled dose of a barbiturate or hypnotic, usually pentobarbital or thiopental. Induced comas protect the brain during major brain surgery and are also induced to control intracranial hypertension caused by brain injury and to treat intractable seizure (status epilipticus). Induced comas are used when conventional therapy has failed. Drug dosing is geared toward achieving the burst-suppression state which effectively reduces brain activity as measured electroencephalography. This reduction in brain activity is balanced against potential side effects of barbiturates or other drugs used in the procedure, which include allergic reactions and cardiovascular effects.
One of the great hazards associated with brain injury is intracranial hypertension. Brain injury may be caused by an accidental head injury or a medical condition such as stroke, tumor, or infection. When the brain is injured, fluids accumulate in the brain, causing it to swell. The skull does not allow for the expansion of the brain; in effect, the brain becomes compressed. If the pressure does not abate, oxygenated blood may not reach all areas of the brain. Also, the brain tissue may be forced against hard, bony edges on the interior of the skull. In either the brain tissue may die, causing permanent brain damage or death. Hypnotics reduce metabolic rate of brain tissue as well as the cerebral blood flow. With these reductions, blood vessels of the brain narrow, decreasing swelling. With swelling relieved, the pressure decreases and some or all brain damage may be averted.

In the neurological intensive-care setting, the most relied-upon neurophysiologic device is the continuous electroencephalographic monitor (cEEG). The cEEG both monitors and displays electrical activity of the brain. Sub-dermal (surface) electrodes are placed symmetrically around the head which are attached to the device that displays and records electrical signals from the brain (EEG). Although simple, the cEEG is has proved quite useful after brain insult or injury (including trauma, surgical procedures such as tumor resection ) and whenever a possibility of seizure exists. Careful monitoring of EEG ensures adequate patient care. cEEG is also necessary to induced coma properly.

The cEEG monitors the electrical silence of the brain induced by hypnotics. Electrical silences are broken by very brief, large electrical discharges (bursts). The EEG is comprised of a sequence of bursts and suppressions. The interval between bursts is used as a measure of the depth of anesthesia. In the case of long-term intensive-care-unit (ICU) monitoring, evaluation and charting of the burst-suppression pattern are routinely practiced while there is no established protocol. Visual segmentation of the burst-suppression pattern is typically performed by nursing staff who attempt to calculate the inter-burst interval in order to titrate hypnotics. In our experience, this process is error-prone and, for all practical purposes, impossible to perform. Furthermore, it is burdensome to the staff as they recognize the difficulty – if not impossibility – of determining the correct interval. The usual result is over- or under-sedation of the patient. Observing this process is what led us to create Wavestate’s neuromonitor.

Wavestate’s monitor uses an automatic computer-aided segmentation algorithm. As such, it calculates and displays – with statistical accuracy – the true interval. Wavestate's machine features a simple, useful, easy-to-understand display. This, we believe, is key. At the very heart of the notion behind Wavestate's devices is an awareness of the importance of the simplicity of the display. In other words, it will tell the staff in real time, in a clear unambiguous manner, the current electrographic state of the patient. It will eliminate all guesswork. As the development of the device progresses, it will recommend to the staff the proper dose of hypnotics to administer – and eventually, following FDA approval that the machine will be capable of attaching directly to a pump which will then administer the drug quickly and accurately itself. This will ensure rapid feedback between the state of the patient and adequate treatment.

Patients displaying either status epilepticus or trauma with increased ICP are often seen in settings that have no neurointensive-care unit and as such, their care may be compromised. Both these events – status epilepticus and increased ICP – can and do occur far from a hospital setting where there is no neurocritical unit equipped to handle such problems. In fact, even in a hospital with an equipped unit, the patients may end up in non-neuro ICU where their management is difficult. Since Wavestate’s machine is portable and has the option of running on battery power, it can easily be used outside the neurointensive-care unit. This will allow for treatment in places where necessary care has been heretofore impossible. It is my hope that Wavestate’s monitor will expand the use of induced coma in the treatment of patients previously deemed untreatable.

Constant monitoring of patient electrophysiology and depth of consciousness provides too much information for human review. Automated EEG analysis has been a dream of physicians for decades and now it is a necessity in modern ICUs. This data-processing problem is especially serious for burst suppression coma as patients may be monitored for days and improper sedation hinders recovery.

Problems and Solutions: Seizure

Detection and report of seizure events is another unresolved dilemma within neurocritical care. Existing EEG units, and there are many, can all display, store, and archive continuous EEG data but they all lack a functional seizure-detection system dedicated to the kind of EEG and seizure activity observed in neurocritical patients. The EEG we see in the ICU contains numerous pathological electrographic signatures, notwithstanding seizure, and these signals are quite different from events recorded in otherwise healthy brains including patients with epilepsy. Current seizure detection software products are designed to detect events in those otherwise healthy patients and not in head trauma patients, which is why they generally fail in the ICU. Wavestate has developed seizure detection technology specifically dedicated to the neurocritical patient. Furthermore, display of seizure events are presented in real time for immediate and timely treatment – not post-hoc analysis as is currently the case with existent EEG technology.

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      4. Induced Coma
      5. Seizure