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Biomedical subjects

G Bryan Young

Publications and source records attributed to G Bryan Young.

At least 19 recordsLinked to original sources
PubMed2006

A comparison of subdermal wire electrodes with collodion-applied disk electrodes in long-term EEG recordings in ICU.

OBJECTIVE: To compare long-term electroencephalographic (EEG) recordings of standard collodion-applied scalp disk electrodes (SDEs) with newly developed subdermal wire electrodes (SWEs) in comatose intensive care unit (ICU) patients. METHODS: Ten comatose ICU patients had simultaneous recordings from 8 active SDEs and 8 active SWE for >24 h. The timing and number of 60 Hz and other electrode artifacts were compared for each set of electrodes by an EEGer who read the recordings in a blinded manner. RESULTS: Sixty Hertz artifact was seen in 16 of 80 SDE and one of 80 SWEs within the first 6 h (P=0.0002). Large, persistent artifacts occurred in 30/80 SDE and 8 of 80 SWE (P=0.0001). Motion artifact with chest physiotherapy was more common in SWEs. CONCLUSIONS: SWE are less susceptible to artifacts and are more suitable for the long-term EEG monitoring in ICU. SIGNIFICANCE: This is the first controlled study that demonstrates the superiority of SWEs compared to SDEs in an ICU population.

Adolescent↗
PubMed2006

Brief review: the role of ancillary tests in the neurological determination of death.

PURPOSE: The acceptance of brain death by society has allowed for the discontinuation of "life support" and the transplantation of organs. In Canada we accept the clinical criteria for brain death (essentially brain stem death) when they can be legitimately applied. Ancillary tests are needed when these clinical criteria cannot be applied or when there are confounders. Ancillary tests include tests of intracranial blood circulation, electrophysiological tests, metabolic studies and tests for residual vagus nerve function. The ideal confirmatory test is one which, when positive, would be incompatible with recoverable brain function (i.e., has no false positives), is not influenced by drugs or metabolic disturbances and which can be readily applied. A critical review of the various ancillary tests used to support the neurological determination of death (brain death) was undertaken. METHODS: A literature review based on a MEDLINE search of relevant articles published between January 1966 to January 2005 was undertaken. RESULTS: Tests of whole brain perfusion/intracranial blood circulation are the only ones that meet stated criteria. CONCLUSIONS: At present only cerebral angiography and nuclear medicine tests of perfusion are accepted by Canadian standards, but computed tomography and magnetic resonance angiography should prove to be suitable. Transcranial Doppler studies may be suitable for specific cases once appropriate guidelines are established.

Brain Chemistry↗
PubMed2005

Continuous EEG monitoring in comatose intensive care patients: epileptiform activity in etiologically distinct groups.

INTRODUCTION: It is unclear whether patients or subpopulations of patients might benefit from EEG monitoring. METHODS: We conducted a prospective trial of continuous electroencephalogram monitoring (CEEG; 48 hours). RESULTS: Eleven of 55 (20%) patients who underwent CEEG monitoring recorded seizures. Of patients with acute structural brain lesions (ASBLs), 10 of 31 (32%) patients experiences recorded seizures, whereas only 24 (4%) patients with metabolic encephalopathies experienced recorded seizures (p < 0.01). Six patients with ASBLs (11%) and one patient with metabolic encephalopathy (4%) had spikes/interictal epileptiform discharges (p = 0.087). CONCLUSION: Our study suggests that CEEG monitoring may be more valuable for detection of seizures in patients with ASBLs than in patients with metabolic encephalopathies.

Adult↗
PubMed2005

Prolonged deficits after focal inhibitory seizures.

INTRODUCTION: Seizures are most commonly associated with positive phenomena such as tonic, clonic or myoclonic movements, automatisms, paresthesias and hallucinations. Negative phenomena, however, are not an uncommon manifestation of seizure activity. Examples of negative seizure phenomena include speech arrest, aphasia, amaurosis, amnesia, numbness, deafness, neglect and atonic seizures. Less commonly described in the literature are focal inhibitory motor seizures. METHODS AND RESULTS: Two patients presenting with rapidly progressive, prolonged hemiparesis, sensory neglect and hemi-visual field obscuration are described. Computed tomography (CT) and magnetic resonance imaging (MRI) of the brain did not reveal progression of known structural lesions or new lesions. The superficial cortex of the hemisphere contralateral to the hemiparesis and sensory neglect enhanced diffusely with gadolinium on T1-weighted MRI images. Electroencephalography demonstrated periodic lateralized epileptiform discharges (PLEDs) in one patient and lateralized suppression and slowing in the other patient. Single photon emission computed tomography (SPECT) revealed hyperperfusion in the hemisphere contralateral to the hemiparesis and sensory neglect. The changes seen on MRI and SPECT resolved with resolution of the symptoms. CONCLUSION: Taken together with the clinical history, the results from these investigations suggest focal inhibitory seizure as the underlying etiology. A review of the literature and investigations helpful in making this difficult diagnosis are provided.

Adolescent↗
PubMed2005

Anoxic-ischemic encephalopathy: clinical and electrophysiological associations with outcome.

INTRODUCTION: Prognostic determination of patients in coma after resuscitation from cardiac arrest is both common and difficult. We explored clinical and electrophysiological testing to determine their associations with favorable and poor outcomes. METHODS: We studied 75 comatose patients resuscitated from cardiac arrest, excluding those who were brain dead or continuously sedated; none received hypothermia therapy. Clinical examinations were performed on day 1. RESULTS: The following proportions recovered awareness: 2 of 18 patients with absent pupillary reflexes; 18 of 57 with preserved pupillary reflexes (p = 0.08); 2 of 32 with absent corneal reflexes; 16 of 43 with preserved corneal reflexes (p = 0.001); 0 of 15 with absent oculovestibular reflexes; and 8 of 29 with preserved oculovestibular reflexes (p < 0.037). Purposeful movements were associated with a high probability of recovery, whereas other categories were unfavorable. Other categories of motor response were associated with an increased proportion of those who died without recovering awareness, but each category had some survivors. Somatosensory evoked potentials (SSEPs) were recorded from 47 patients. One of 21 patients with loss of the N20 component survived, compared with survival of 11 of 26 patients in whom it was present (p = 0.003). All 5 patients with preserved N70 responses recovered awareness in a subgroup of 33 patients. Sixteen of 22 subjects with mild electroencephalogram (EEG) abnormalities recovered consciousness, compared with the survival of 3 of 50 patients with malignant EEG patterns (p = 0.0000001). Combining SSEP with EEG findings produced even greater predictive value. CONCLUSION: It seems unlikely that any single test will prove to have 100% predictive value for outcome; further studies combining clinical, EEG, and SSEP testing are warranted.

Adult↗
PubMed2004

A stronger approach to weakness in the intensive care unit.

ICU-acquired limb and respiratory muscle weakness is a common, serious ICU syndrome, increasing in frequency with prolonged ICU stay and sepsis. A systematic approach facilitates precise localization of the problem within central or peripheral nervous system. Most cases relate to critical illness polyneuropathy or myopathy or a combination of both (critical illness neuromyopathy). Within the latter entity, the relative contribution of neuropathy versus myopathy varies considerably among affected patients. Muscle enzyme testing, electromyography-nerve conduction and muscle biopsy are valuable investigative tests. Nerve biopsy is less commonly needed, but is useful when vascultis is suspected.

Critical Illness↗
PubMed2004

Treatment of refractory status epilepticus with inhalational anesthetic agents isoflurane and desflurane.

BACKGROUND: Refractory status epilepticus (RSE) is defined as continued seizures after 2 or 3 antiepileptic drugs have failed. Several intravenous agents have been used for RSE; however, problems occur with their toxicity and/or effectiveness. OBJECTIVE: To report our experience with inhalational anesthesia (IA) in patients who were refractory to other antiepileptic drugs. DESIGN, SETTING, AND PARTICIPANTS: Retrospective review during a 4-year period of patients with RSE treated with isoflurane and/or desflurane. MAIN OUTCOME MEASURE: Efficacy of IA on therapy in terminating RSE. RESULTS: Seven patients (4 male) aged 17 to 71 years received 7 to 15 (mean, 10) antiepileptic drugs in addition to IAs. The IAs were initiated after 1 to 103 (mean, 19) days of RSE and were used for a mean +/- SD 11 +/- 8.9 days. All patients received isoflurane, and 1 patient in addition received desflurane anesthesia 21 days after the onset of RSE for a total of 19 days. Regardless of seizure type, isoflurane and desflurane consistently stopped epileptic discharges with adequate, sustained electroencephalographic burst suppression within minutes of initiating IA therapy. Four patients had good outcomes, 3 died (1 of acute hemorrhagic leukoencephalitis, 1 of bowel infarction, and 1 of toxic encephalopathy, who remained in a persistent vegetative state until death 5.5 months after the onset of seizures). Complications during IA therapy included hypotension (7/7), atelectasis (7/7), infections (5/7), paralytic ileus (3/7), and deep venous thrombosis (2/7). No patient developed renal or hepatic dysfunction. CONCLUSIONS: Isoflurane and desflurane adequately suppressed RSE in all cases. Complications were common, but mortality and long-term morbidity were related to the underlying disease and duration of RSE. Prolonged use of isoflurane and desflurane is well tolerated.

Adolescent↗
PubMed2004

Prognostic value of evoked responses and event-related brain potentials in coma.

The behaviourally unresponsive patient, unable to exhibit the presence of cognition, constitutes a conundrum for health care specialists. Prognostic uncertainty impedes accurate management decisions and the application of ethical principles. An early, reliable prognosis is highly desirable. In this review investigations studying comatose patients with coma of different etiologies were selected. It is concluded that objective prognostication is enhanced by the use of electrophysiological tests. Persistent abnormalities of brainstem auditory evoked potentials and short-latency somatosensory evoked potentials reliably indicate the likelihood of irreversible neurological deficit or death. Meanwhile, the presence of "cognitive" event-related brain potentials (e.g., P300 and mismatch negativity) reflects the functional integrity of higher level information processing and, therefore, the likelihood of capacity for cognition. An approach that combines clinical and electrophysiological values provides optimal prediction of outcome and level of disability.

Acoustic Stimulation↗
PubMed2004

The apnea test for brain death determination: an alternative approach.

INTRODUCTION: Problems associated with the standard apnea test relate to overshooting or undershooting the target PaCO2, potentially compromising the viability of organs for transplantation or invalidating the test. MATERIALS AND METHODS: In 60 adult patients, the authors used an alternative method using exogenously administered CO2 and measurement of end-tidal CO2. RESULTS: All patients achieved an adequate respiratory stimulus (mean increase in PaCO2 was 28+/-3 mmHg, postapnea test pH was 7.20+/-.02). There was a clinically insignificant reduction in arterial blood pressure during testing, but no other complications occurred. Multiple regression analysis demonstrated a correlation between the predicted PaCO2 (predicted from the end-tidal CO2) and measured PaCO2 (64+/-9 versus 67+/-9; r=.75169, p<0.0001). CONCLUSION: Exogenously administered CO2 as an alternative method for the standard apnea test was a reliable and safe method, with minimal complications that offers several advantages over the standard method.

Adolescent↗
PubMed2004

A critique of ancillary tests for brain death.

The acceptance of brain death by society has allowed for the discontinuation of "life support" and the transplantation of organs. The standard clinical criteria for brain death, when rigorously applied, ensure that the brainstem is destroyed. Because more rostral structures are more vulnerable than the brainstem, these are almost invariably devastated when brainstem function is irreversibly lost as a result of whole brain insults. Then, clinical criteria for "brainstem death" ensure that "whole-brain death" is present. However, if the brainstem is selectively damaged or if brainstem function cannot be adequately assessed clinically, ancillary tests are needed to confirm whole-brain death with certainty. Ancillary tests are also required in very young children. In addition, some societies require their use as a matter of principle. Only tests of whole-brain perfusion adequately serve these purposes.

Brain Death↗