Jamie Sleigh

Caregiver burden at 1 year following severe traumatic brain injury

Sixty-nine primary caregivers of adults with a severe traumatic brain injury (TBI) were assessed at 1-year post-injury. Caregivers completed questionnaires on the physical, cognitive, emotional, behavioural, and social functioning of the person with TBI. Caregiver objective burden, psychosocial functioning, and subjective burden were also assessed. Clinically significant levels of anxiety and depression were evident in over a third of the caregivers. Similarly, a quarter of the caregivers reported poor social adjustment. There was no consistent relationship between the prevalence of various types of objective burden and the level of subjective distress that resulted from these changes. The person with TBIs emotional difficulties, in particular their anger, apathy, and dependency, caused the greatest distress for caregivers. With regard to the impact that caregiving had on their own lives, caregivers were most distressed by the loss of personal free time. Results from a regression analysis indicated that the person with TBIs physical impairment, number of behavioural problems, and social isolation were the strongest predictors of caregiver burden. The impact that caring for a person with severe TBI can have on the extended family unit is discussed.

Psychosocial functioning during the year following severe traumatic brain injury

The psychosocial functioning of a group of 65 adults with severe traumatic brain injury was assessed at 6 months and 1 year post-injury. Aspects of emotional, behavioural, and social functioning were investigated. The prevalence of depression remained constant (24%) over time, although there was some individual variation in the reporting of symptoms. Impatience was the most frequently reported behavioural problem at both assessments. Whilst there was a slight increase in the number of behavioural problems and level of distress reported over time, the most obvious change was in the type of behavioural problems that caused distress. At 1 year post-injury, problems with emotional control were found to be most distressing for the patients. A comparison with pre-morbid social functioning showed the loss of employment to be 70%, 30% returned to live with their parents, and relationship breakdown occurred for 38%. There was also a significant and ongoing decrease in all five aspects of social and leisure activities.

The Bispectral Index: A Measure of Depth of Sleep?

UNLABELLED How does physiological sleep affect the Bispectral Index (BIS)? We collected electroencephalographic (EEG) data from five subjects during the early part of the night, comparing the changes in the BIS with the conventional EEG stages of sleep. We found that the BIS was a consistent marker of depth of sleep. Light sleep occurred at BIS values of 75-90, slow-wave sleep occurred at BIS values of 20-70, and rapid eye movement sleep occurred at BIS values of 75-92. The effects of natural sleep on the BIS seem to be similar to the effects of general anesthesia on the BIS. The BIS may have a role in monitoring depth of sleep. IMPLICATIONS Electroencephalographic data were collected from five subjects during sleep. We found that the Bispectral Index decreased during increasing depth of sleep in a fashion very similar to the decrease in Bispectral Index that occurs during general anesthesia. This study further highlights the electroencephalographic similarities of states of sleep and general anesthesia.

Caregiver burden at 6 months following severe traumatic brain injury

Sixty-nine primary caregivers of people with a severe traumatic brain injury (TBI) were assessed at 6 months post injury. Caregivers completed questionnaires on the physical, cognitive, emotional, behavioural, and social functioning of the persons with the TBI. Caregiver psychosocial functioning and levels of subjective and objective burden were also assessed. Clinically significant levels of anxiety, depression, and impairment in social adjustment were evident in over a third of the caregivers. The frequency with which various changes in the person with the TBI and types of objective burden were reported had little relationship to the degree of distress caused by these changes. The person with TBIs social isolation and negative emotional behaviours caused the greatest degree of stress for caregivers. Caregivers were also most distressed by the impact that caregiving had on their personal health and free time. The results from a multiple regression analysis suggest that it is the presence of behavioural problems in the person with the TBI that has the most severe and pervasive impact on all aspects of caregiver functioning. It is suggested that these findings be taken into account when providing rehabilitation services to people with TBI and their families.

The howling cortex: seizures and general anesthetic drugs.

The true incidence of seizures caused by general anesthetic drugs is unknown. Abnormal movements are common during induction of anesthesia, but they may not be indicative of true seizures. Conversely, epileptiform electrocortical activity is commonly induced by enflurane, etomidate, sevoflurane and, to a lesser extent, propofol, but it rarely progresses to generalized tonic-clonic seizures. Even “nonconvulsant” anesthetic drugs occasionally cause seizures in subjects with preexisting epilepsy. These seizures most commonly occur during induction or emergence from anesthesia, when the anesthetic drug concentration is relatively low. There is no unifying neural mechanism of anesthetic drug-related seizurogenesis. However, there is a growing body of experimental work suggesting that seizures are not caused simply by “too much excitation,” but rather by excitation applied to a mass of neurons which are primed to react to the excitation by going into an oscillatory seizure state. Increased &ggr;-amino-butyric acid (GABA)ergic inhibition can sensitize the cortex so that only a small amount of excitation is required to cause seizures. This has been postulated to occur 1) at the network level by increasing the propensity for reverberation (e.g., by prolongation of the “inhibitory lag”), or 2) via different effects on subpopulations of interneurons (“inhibiting-the-inhibitors”) or 3) at the synaptic level by changing the chloride reversal potential (“excitatory GABA”). On the basis of applied neuropharmacology, prevention of anesthetic-drug related seizures would include 1) avoiding sevoflurane and etomidate, 2) considering prophylaxis with adjunctive benzodiazepines (&agr;-subunit GABAA agonists), or drugs that impair calcium entry into neurons, and 3) using electroencephalogram monitoring to detect early signs of cortical instability and epileptiform activity. Seizures may falsely elevate electroencephalogram indices of depth of anesthesia.

Caregiver burden during the year following severe traumatic brain injury.

Fifty-two primary caregivers of people with a severe traumatic brain injury (TBI) were assessed at 6-months and 1-year postinjury. Caregiver appraisal of the person with TBIs physical, cognitive, emotional, behavioural, and social functioning was assessed. Caregiver psychosocial functioning and levels of subjective and objective burden were also assessed. Some aspects of the difficulties reported for the people with TBI remained stable, while others increased in frequency, over time. At 6-months postinjury, approximately one third of caregivers reported clinically significant symptoms of anxiety and depression, and poor social adjustment. By 1-year postinjury, the prevalence of anxiety and depression remained the same, although only one-quarter continued to report poor social adjustment. There was some evidence of adaptation by care-givers, as the frequency with which various types of objective burden were reported remained stable, while the distress caused by these decreased in the first year postinjury. It appears that the impact on caregivers of physical impairment is comparatively short-lived and that caregivers learn some practical ways to manage the behavioural problems of the people with TBI. Despite this, over time the person with TBIs behavioural and cognitive problems begins to play a larger role in the level of distress experienced by the caregiver. However, it is the person with TBIs social isolation that has a stable and consistent role in the experience of subjective burden for primary caregivers in the first year postinjury.

The use of polymerase chain reaction to detect septicemia in critically ill patients

OBJECTIVE To describe the use of bacterial DNA amplification of conserved bacterial 16S ribosomal DNA nucleotide sequences by polymerase chain reaction (PCR) to detect the presence of septicemia in critically ill septic patients. DESIGN Case series of blood samples from septic patients comparing the PCR results with conventional blood culture results. SETTING A general intensive care unit in a tertiary referral hospital. PATIENTS Two sets of samples (n = 101 and n = 55) from patients diagnosed as clinically septic and requiring blood cultures. They were classified by internationally accepted criteria into systemic inflammatory response syndrome, severe sepsis, and septic shock groups. INTERVENTIONS Blood samples taken in a sterile fashion concurrently for blood culture, and PCR of the bacterial 16S ribosomal RNA gene in leukocytes and plasma. Two different DNA extraction techniques for PCR were tried sequentially. MEASUREMENTS AND MAIN RESULTS Blood culture and PCR positivity were measured in relation to the clinical classification of severity of sepsis. Using the initial extraction method (n = 101), ten patients were positive by both PCR and blood culture, eight patients were PCR positive and blood culture negative, and seven patients were blood culture positive and PCR negative. From the clinical criteria, PCR detected at least six true positives that had been missed on blood culture and missed four true Gram-positive bacteremias. When the initial code was broken, this deficiency was rectified using the improved extraction technique (n = 55), in which ten patients were positive by PCR and blood culture, 29 patients were PCR positive and blood culture negative, and two patients were PCR negative and PCR positive. CONCLUSIONS We conclude that the use of PCR (for the 16S ribosomal DNA in the plasma) was significantly more sensitive than the use of conventional blood culturing techniques for the detection of bacteremia in seriously ill patients. This could prove to be a valuable adjunct to conventional blood cultures.

Practical use of the raw electroencephalogram waveform during general anesthesia: the art and science.

Quantitative electroencephalogram (qEEG) monitors are often used to estimate depth of anesthesia and intraoperative recall during general anesthesia. As with any monitor, the processed numerical output is often misleading and has to be interpreted within a clinical context. For the safe clinical use of these monitors, a clear mental picture of the expected raw electroencephalogram (EEG) patterns, as well as a knowledge of the common EEG artifacts, is absolutely necessary. This has provided the motivation to write this tutorial. We describe, and give examples of, the typical EEG features of adequate general anesthesia, effects of noxious stimulation, and adjunctive drugs. Artifacts are commonly encountered and may be classified as arising from outside the head, from the head but outside the brain (commonly frontal electromyogram), or from within the brain (atypical or pathologic). We include real examples of clinical problem-solving processes. In particular, it is important to realize that an artifactually high qEEG index is relatively common and may result in dangerous anesthetic drug overdose. The anesthesiologist must be certain that the qEEG number is consistent with the apparent state of the patient, the doses of various anesthetic drugs, and the degree of surgical stimulation, and that the qEEG number is consistent with the appearance of the raw EEG signal. Any discrepancy must be a stimulus for the immediate critical examination of the patient’s state using all the available information rather than reactive therapy to “treat” a number.

Multiscale permutation entropy analysis of EEG recordings during sevoflurane anesthesia

Electroencephalogram (EEG) monitoring of the effect of anesthetic drugs on the central nervous system has long been used in anesthesia research. Several methods based on nonlinear dynamics, such as permutation entropy (PE), have been proposed to analyze EEG series during anesthesia. However, these measures are still single-scale based and may not completely describe the dynamical characteristics of complex EEG series. In this paper, a novel measure combining multiscale PE information, called CMSPE (composite multi-scale permutation entropy), was proposed for quantifying the anesthetic drug effect on EEG recordings during sevoflurane anesthesia. Three sets of simulated EEG series during awake, light and deep anesthesia were used to select the parameters for the multiscale PE analysis: embedding dimension m, lag tau and scales to be integrated into the CMSPE index. Then, the CMSPE index and raw single-scale PE index were applied to EEG recordings from 18 patients who received sevoflurane anesthesia. Pharmacokinetic/pharmacodynamic (PKPD) modeling was used to relate the measured EEG indices and the anesthetic drug concentration. Prediction probability (P(k)) statistics and correlation analysis with the response entropy (RE) index, derived from the spectral entropy (M-entropy module; GE Healthcare, Helsinki, Finland), were investigated to evaluate the effectiveness of the new proposed measure. It was found that raw single-scale PE was blind to subtle transitions between light and deep anesthesia, while the CMSPE index tracked these changes accurately. Around the time of loss of consciousness, CMSPE responded significantly more rapidly than the raw PE, with the absolute slopes of linearly fitted response versus time plots of 0.12 (0.09-0.15) and 0.10 (0.06-0.13), respectively. The prediction probability P(k) of 0.86 (0.85-0.88) and 0.85 (0.80-0.86) for CMSPE and raw PE indicated that the CMSPE index correlated well with the underlying anesthetic effect. The correlation coefficient for the comparison between the CMSPE index and RE index of 0.84 (0.80-0.88) was significantly higher than the raw PE index of 0.75 (0.66-0.84). The results show that the CMSPE outperforms the raw single-scale PE in reflecting the sevoflurane drug effect on the central nervous system.

Cortical entropy changes with general anaesthesia: theory and experiment

Commonly used general anaesthetics cause a decrease in the spectral entropy of the electroencephalogram as the patient transits from the conscious to the unconscious state. Although the spectral entropy is a configurational entropy, it is plausible that the spectral entropy may be acting as a reliable indicator of real changes in cortical neuronal interactions. Using a mean field theory, the activity of the cerebral cortex may be modelled as fluctuations in mean soma potential around equilibrium states. In the adiabatic limit, the stochastic differential equations take the form of an Ornstein-Uhlenbeck process. It can be shown that spectral entropy is a logarithmic measure of the rate of synaptic interaction. This model predicts that the spectral entropy should decrease abruptly from values approximately 1.0 to values of approximately 0.7 as the patient becomes unconscious during induction of general anaesthesia, and then not decrease significantly on further deepening of anaesthesia. These predictions were compared with experimental results in which electrocorticograms and brain concentrations of propofol were recorded in seven sheep during induction of anaesthesia with intravenous propofol. The observed changes in spectral entropy agreed with the theoretical predictions. We conclude that spectral entropy may be a sensitive monitor of the consciousness-unconsciousness transition, rather than a progressive indicator of anaesthetic drug effect.