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Biomedical subjects

G B Young

Publications and source records attributed to G B Young.

At least 37 records · Page 2Linked to original sources
PubMed1999

Seizure and electroencephalographic changes in the newborn period induced by opiates and corrected by naloxone infusion.

OBJECTIVE: To describe the association between opioid administration in the newborn period and neurologic abnormalities. STUDY DESIGN: Case reports of two infants who presented with seizure activity and abnormal electroencephalograms associated with opiate administration, and reversed by naloxone. RESULTS: The first was a preterm infant who developed a burst-suppression pattern on the electroencephalogram while receiving a continuous infusion of morphine and muscle paralysis. Naloxone injection during the electroencephalogram recording reversed the burst-suppression pattern. The second was a term infant receiving fentanyl infusion for pain control following surgery, who presented with motor seizure that was only partially controlled with barbiturates. An abnormal electroencephalogram recording during the opiate infusion improved with naloxone administration. CONCLUSION: Our observations indicate a potential for neurologic abnormalities, including induction of seizure activity and electroencephalogram abnormalities, suggesting caution when opiates are used for sedation and/or pain control in the newborn period.

Brain↗
PubMed1999

EEG monitoring in the intensive care unit: pitfalls and caveats.

Electroencephalogram monitoring is a valuable means of monitoring thalamocortical function in the comatose, sedated, or paralyzed patient in the intensive care unit. The following problems arise especially with long-term recordings that are beyond those experienced in the standard EEG laboratory: 1) faulty electrodes, either single- or multiple-scalp electrodes or ground or reference electrodes; 2) connections of electronic equipment; 3) induced artifacts from electronic devices and nonelectronic equipment; 4) electrode placement issues; and 5) biologic, including movement-related, artifacts. Continuous quality improvement strategies should be implemented to minimize problems. Prompt troubleshooting and regular review sessions are two important components.

Artifacts↗
PubMed1999

EEG and clinical associations with mortality in comatose patients in a general intensive care unit.

The authors examined EEG findings and clinical factors for their association with outcome in comatose patients in their general intensive care unit. The following individual and combinations of factors were strongly related to mortality, with positive predictive values of >0.80 and odds ratios >2.0: age over 65 years, anoxic/ischemic encephalopathy, EEG suppression, lack of EEG reactivity; anoxia-ischemia with partial or complete cranial nerve areflexia, anoxia-ischemia with EEG suppression; anoxia-ischemia and generalized epileptiform activity; anoxia-ischemia with partial cranial nerve areflexia and EEG suppression. Conversely, the following factors favored survival rather than death: systemic infection/sepsis, metabolic derangement (excluding anoxic-ischemic insult), trauma; dysrhythmia, focal epileptiform activity, and regional delta and reactivity on EEGs. The findings of this study support the integration of these data into intensive care unit prognostic scoring systems, such as later versions of the Acute Physiology and Chronic Health Evaluation (APACHE).

Coma↗
PubMed1998

Metabolic and inflammatory cerebral diseases: electrophysiological aspects.

The electroencephalogram (EEG) is an important diagnostic tool in coma. Although comatose patients may be similar on neurological examination, the EEG reveals a wide range of abnormalities. For metabolic and septic encephalopathies, the "anesthesia model" is a useful analogy. The EEG is very sensitive to the depth or severity of brain dysfunction in coma as well as the direction of the process if serial tracings or continuous recordings are used. While the EEG is rarely specific for the etiology of coma, it may help determine the class or general category of disease process. In conditions capable of causing neuronal death, e.g., anoxia-ischemia, the EEG can be of prognostic value.

Anesthesia↗
PubMed1997

An electroencephalographic classification for coma.

BACKGROUND: The assessment of thalamocortical function in comatose patients in the intensive care unit (ICU) can be difficult to determine. Since the electroencephalogram (EEG) affords such assessment, we have developed an EEG classification for comatose patients in our general ICU. METHODS: One hundred EEGs were classified in a blinded fashion by two EEGers, using our method and that of Synek. Interobserver agreement was assessed using kappa score determination. RESULTS: Kappa scores were 0.90 for our system and 0.75 for the Synek system. (The Kappa score represents the inter-rater agreement that is beyond chance; 0.90 is almost perfect agreement, while 0.75 is substantial agreement). CONCLUSION: Our system for classifying EEGs in comatose patients has a higher interobserver reliability than one that was previously published. This EEG classification scheme should be useful in clinical electrophysiological research involving ICU patients, allowing for internal consistency and comparisons among centres.

Adult↗
PubMed1997

Digital conversion of paper electroencephalograms using a hand scanner.

We report a method of quantifying the analog signal of paper-recorded EEGs that involves readily available technology, including a standard personal computer and a compatible hand scanner. Simulations assessed the effects of erroneously scanning the paper at a slight angle and estimating pen arc distortion; these effects were demonstrated to be insignificant. The method allows application of several quantitative techniques, including power spectral analysis and determination of the squared coherence between homologous regions. In a companion study, we applied this technique to compare the coherence in patients with alpha pattern coma to coherence in normal subjects.

Analog-Digital Conversion↗
PubMed1997

Comparison between the alpha pattern in normal subjects and in alpha pattern coma.

Alpha pattern coma (APC) is an uncommon clinical EEG pattern in comatose patients, most commonly in association with anoxic-ischemic encephalopathy after cardiac arrest. Despite the pattern's striking similarity to that of the normal awake EEG, there are theoretical and experimental reasons for believing that the two rhythms result from different processes. The analysis of quantitative differences in APC from normal rhythms requires computer analysis. Because most cases of this rare entity have been collected over the years on paper traces, computer analysis appears implausible. In a companion article, we describe a method to quantify sections of paper EEGs. We applied this method to EEGs of five APC patients and five normal controls and noted a significant difference in the coherence between the two hemispheres in the alpha range. This finding is in keeping with theoretical, experimental, and clinical observations suggesting that APC may result from significant thalamo-cortical disruption.

Alpha Rhythm↗
PubMed1996

Unusual effects of an engineered disulfide on global and local protein stability.

The global and local stabilities of a eukaryotic ferricytochrome c variant with an engineered disulfide are examined. The disulfide connects position 20, which is usually a valine, to position 102, which is usually a threonine. The cross-linked variant is approximately 1.2 kcal mol-1 less stable than the wild-type protein at 298 K, pH 4.6, in H2O and D2O. Circular dichroism studies show that the decreased stability results from structure-induced stabilization of the denatured state [Betz, S. F., & Pielak, G. J. (1992) Biochemistry 31, 12337-12344]. Here, we use proton chemical shift, paramagnetic shift, and amide proton exchange data to obtain atomic level structural and energetic information. Chemical and paramagnetic shift data indicate only minor native state structural changes. Local stability is obtained from amide proton-deuterium exchange data, using model peptide intrinsic exchange rates. As expected, the exchange data indicate that cross-link incorporation decreases the majority of local stabilities. Near the cross-link, however, local stability seems to increase despite the overall global stability decrease. Furthermore, local stability changes for hydrophobic core residues seem to be greater than the global stability change. We interpret these observations as cross-link-induced changes in exchange competent states and relate them to changes in the denatured state.

Amino Acid Sequence↗
PubMed1996

Brain mapping of median nerve somatosensory evoked potentials with combined 99mTc-ECD single-photon emission tomography and magnetic resonance imaging.

Single-photon emission tomography (SPET) was performed during electrical median nerve stimulation and used to detect focal neuronal activation in the somatosensory pathways. Intravenously administered technetium-99m ethyl cysteinate dimer (ECD) was used as a blood flow tracer to obtain baseline and activated images in each of three subjects. After image registration, baseline images were compared voxel by voxel with the activation images. In addition, the mean summation of the activated-state images of the subjects was compared with the mean summation of the baseline-state images of ten normal subjects. Discrete brain regions occupying 0.9%-1.6% of total brain volume showed an increase in signal from 33.6% to 35.0%. For further anatomical localization of regional increases in signal, the MRI scan of each subject was registered and superimposed on the activated-state SPET image. This method may be used to localize lesions in various disorders of the central nervous system.

Adult↗
PubMed1996

An assessment of nonconvulsive seizures in the intensive care unit using continuous EEG monitoring: an investigation of variables associated with mortality.

Of 49 patients with nonconvulsive seizures studied with continuous EEG monitoring, the overall mortality was 33% (16/49). Of the 23 patients with nonconvulsive status epilepticus (NCSE), 13 died (mortality 57%). Individual variables significantly associated with mortality were age, presence of NCSE, seizure duration, hospital and NICU length of stay, and delay to diagnosis and etiology (acute illness versus remote symptomatic). With multivariate logistic regression, only seizure duration (p = 0.0057, OR = 1.131/hour) and delay to diagnosis (p = 0.0351, OR = 1.039/hour) were associated with increased mortality. Acute symptomatic cases could not be adequately classified as either absence, simple, or complex partial status epilepticus when the impairment of consciousness arose form the initial illness. Current classifications of status epilepticus are inadequate for such cases.

Adult↗
PubMed1996

The cortical representation of somatosensory evoked potentials of the phrenic nerve.

Respiratory electrophysiological studies are of essential value in diagnosing and managing patients with respiratory failure, but assessment of the sensory phrenic nerve fibres has been neglected. We recorded phrenic nerve somatosensory evoked potentials (SSEPs) by combining neurophysiological and neuroimaging techniques in three healthy subjects. Evoked potentials of the phrenic nerve showed the highest amplitude at CP3, determined by the modified 10-20 EEG system, and occurred at a constant latency, PI at 12.0 +/- 0.6 ms, and NI at 17.3 +/- 0.8 ms. Single photon emission computer tomography (SPECT) performed during phrenic nerve stimulation revealed focal neuronal activation in the somatosensory pathways. Intravenously administered Tc-99m Ethyl Cysteinate Dimer (ECD) was used as a blood flow tracer to obtain baseline and activated images. After image registration, baseline images were compared voxel-by-voxel with the activation images. The mean inter-subject summation image of the activated state was compared with that of the baseline state using ten normal subjects. The extent of the total voxel volume increase on the mean images of the 3 activated SPECT images was 0.7%, and a mean signal increase of 22%. For further anatomic localization of regional increases in signal, the magnetic resonance image (MRI) scan of each subject was registered and superimposed on the activated stage SPECT image. This method may be used clinically to study the pathophysiology of impaired central respiratory drive.

Adult↗
PubMed1996

Metabolic encephalopathies.

Metabolic encephalopathies are common among patients in the critical care unit. Septic, hypoxic-ischaemic, hepatic and uraemic encephalopathies are most frequently seen. They produce global neurological dysfunctions ranging from lethargy or mild confusion to coma. Metabolic encephalopathies must be distinguished from other conditions such as structural brain lesions, infections of the central nervous system or drug reactions. Neurological manifestations are often present in the early stages of systemic illness and may be the first symptom. The severity of encephalopathy generally correlates with that of the systemic illness. Appropriate investigations often include drug and metabolic screens, cultures of blood and cerebrospinal fluids and neuro-imaging studies. Electroencephalogram is useful to grade the severity of encephalopathy. With some exceptions such as hypoxic-ischaemic encephalopathy, most metabolic encephalopathies are reversible unless secondary complications such as brain herniation occurred. Treatment is generally that of the underlying systemic illness and supportive measures.

Brain Diseases, Metabolic↗