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Biomedical subjects

H R Ortega

Publications and source records attributed to H R Ortega.

4 recordsLinked to original sources
PubMed2006

Patient state index.

The patient state index (PSI) is a clinically validated measure of the effect of anaesthesia and sedation. The PSI is calculated via a proprietary algorithm by a high-resolution 4-channel electroencephalograph (EEG) monitor after advanced artifact rejection. The PSI has been designed specifically for intra-operative and intensive care use to monitor patient sedation and drug effect. The algorithm relies on EEG power, frequency and phase information from anterior-posterior relationships of the brain as well as coherence between bilateral brain regions. The EEG monitor, initially called the PSA4000, is also the SEDLine monitor, the newest generation of the device. The SEDLine system provides the clinician the option of storing and downloading patient data for future use as well as monitoring bilateral brain function and symmetry with a density spectral array (DSA) display.

Algorithms↗
PubMed1991

Dermatomal somatosensory evoked potentials in brachial plexus injuries.

The dermatomally stimulated somatosensory evoked potential is an essentially painless, noninvasive procedure that can add useful information to the diagnosis of the site and extent of brachial plexus injuries. In this study, 13 patients with unilateral brachial plexus injuries who had previously undergone conventional electromyographic testing underwent somatosensory evoked potential recording with median, ulnar, radial, musculocutaneous nerve and C5, C6, C7, C8 and T1 dermatomal stimulation. There was no significant difference in the peak latencies, interpeak latencies, or amplitudes of the major peaks between the normal values and the values from the affected levels. However, analysis for absence or presence of major peaks from side-to-side was useful in supporting the data from electromyographic and radiologic studies, as well as in providing more specific information as to the level of injury and extent of injury in two of the cases. The accurate diagnosis can provide the information needed to determine patient treatment as well as plan the rehabilitation program of the patient. The dermatomal somatosensory evoked potential can be a useful supplement to the assessment of the patient with a brachial plexus injury.

Adult↗
PubMed1988

Somatosensory evoked responses to dermatomal stimulation in cervical spinal cord injured and normal subjects.

This exploratory study investigates dermatomal evoked potential patterns in the upper extremities of normal and spinal cord injured subjects. Fifteen normal subjects without neurologic deficits and twelve patients with partial or complete spinal cord injuries were tested at dermatomal levels C5, C6, C7, C8, and T1, and also at median and ulnar nerve sites. Responses were recorded at the scalp. Analyses of evoked response patterns included measurement and comparison of peak and interpeak latencies and amplitudes as well as blind ratings of the degree of abnormality of evoked potential waveforms. Analyses were also made of relationships between evoked potential data and neurological findings on clinical examination. There appeared to be a fairly consistent SEP response among normals when dermatomes C6 through C8 are stimulated. Less consistent responses are observed when C5 and T1 are stimulated. In general, spinal cord injured subjects as compared to normal subjects had evoked responses with less consistent peaks, more amplitude diminution, and greater diffuseness and overall pattern abnormality even at dermatomal levels that were intact on clinical neurologic examination. There was also a distinct progression of overall SEP abnormality in dermatomes with impaired vibration, light touch, and position sense. There were no consistent differences in interpeak latencies between SEPs of normal and spinal cord injured subjects at intact dermatomes, but there were significant differences in EP abnormalities (EPA scores). Possible reasons for the differences in the SEP responses between normals and spinal cord injured subjects include spinal cord injury not detectable by clinical exam. Difficulty in obtaining objective and accurate sensory reports also contributes to data unreliability. In conclusion, we believe that stimulation of specific sensory dermatomes merits further study, as it has a number of possible clinical uses. These include: (1) surgical monitoring at more specific levels than monitoring with mixed nerve root stimulation, (2) for study of specific nerve root injury, and (3) as an aid in examining the neurological status in acutely injured spinal cord patients who are unable to cooperate adequately during examination, such as the very young or those with lowered levels of awareness associated with head injury. Additional information which could be useful to obtain is cervical dermatomal stimulation with spinal recording sites.

Adolescent↗