To BIS or not to BIS? That is the question.
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Adolescent↗
Biomedical subjects
Chantal Kerssens
Publications and source records attributed to Chantal Kerssens.
Functional connectivity changes with concentration of sevoflurane anesthesia.
Low-frequency oscillations (<0.08 Hz) have been detected in functional magnetic resonance imaging studies, and appear to be synchronized between functionally related areas. The effect of anesthetic agents on cortical activity is not completely characterized. This study assessed the effect of anesthesia on the temporal relations in activity in the motor cortices. Resting-state magnetic resonance data were acquired on six volunteers under different anesthetic states (using 0.0%, 2.0% and 1.0% stable end-tidal sevoflurane). Across all volunteers, the number of significant voxels (p<2.5 x 10) in the functional connectivity maps was reduced by 78% for light anesthesia and by 98% for deep anesthesia, compared with the awake state. Additionally, significant correlations in the connectivity maps were bilateral in the awake state but unilateral in the light anesthesia state.
Adult↗
Reluctant acceptance of xenotransplantation in kidney patients on the waiting list for transplantation.
Previous research has shown contradictory results regarding the acceptance of xenotransplantation (XT) by kidney patients. This variance in attitude towards XT could be explained by differences in knowledge of XT, the availability of alternative treatment options, specific beliefs and cognitions of the patient, and differences in the health status of the patients. We studied 61 patients in this contention in the Netherlands waiting for a kidney transplant. All took part in in-depth interviews and filled out questionnaires on two occasions, once before and once after an information brochure on XT had been read. We found that a better health status is correlated with a greater acceptance of XT, but only before information was given. After information had been given, the acceptance of XT decreased significantly. However, if XT is the only possibility in a life-threatening situation, almost all patients are willing to accept XT, except for a small group (approximately 10-15%) with fundamental religious and/or spiritual objections against such treatment. When alternative treatment options such as a human cadaver donor, a living related donor or commercial donor are offered, the majority of patients would prefer those to XT. The main reason for reluctance is uncertainty about the risks of XT to personal health. Because alternatives are currently available, we expect that XT will become more popular only if future results of this procedure have proved to be comparable to transplantation with a human donor kidney.
Female↗
No evidence of memory function during anesthesia with propofol or isoflurane with close control of hypnotic state.
BACKGROUND: The authors previously demonstrated memory function during apparently adequate general anesthesia in trauma patients. Hypnotic state fluctuations, stress, and variable amnesic qualities of commonly used anesthetics could account for this effect. METHODS: The authors replicated the trauma investigation in 90 elective surgical patients to enable anesthetic titration to a bispectral index value of 50-55 during auditory presentation of word stimuli. Patients were randomly assigned to maintenance with propofol (n = 48) or isoflurane (n = 42). Before surgery, state anxiety and trait anxiety were assessed using self-report measures. Postoperative memory assessment relied on the process dissociation procedure using a word stem completion task. RESULTS: There were no differences between groups for relevant demographic, preoperative, or supplemental drug variables. Ninety-eight percent of words were presented within a bispectral index range of 40-60, with values averaging 48.8 (SD = 5.7) during word presentation. Neither the process dissociation procedure nor standard measures of conscious recall and recognition memory showed evidence of explicit or implicit memory. Preoperative stress levels did not correlate with postoperative memory test scores in either study group. CONCLUSIONS: In contrast to the results of their previous study, the authors found no evidence of memory function with close control of hypnotic state. This suggests that hypnotic state fluctuations are important to memory activation under anesthesia. Other variables may contribute to preserved memory function as well. Propofol and isoflurane block memory equally well during adequate anesthesia.
Adult↗
Attenuated brain response to auditory word stimulation with sevoflurane: a functional magnetic resonance imaging study in humans.
BACKGROUND: Functional magnetic resonance imaging offers a compelling, new perspective on altered brain function but is sparsely used in studies of anesthetic effect. To examine effects on verbal memory encoding, the authors imaged human brain response to auditory word stimulation using functional magnetic resonance imaging at different concentrations of an agent not previously studied, and tested memory after recovery. METHODS: Six male volunteers were studied breathing 0.0, 2.0, and 1.0% end-tidal sevoflurane (awake, deep, and light states, respectively) via laryngeal mask. In each condition, they heard 15 two-syllable English nouns via closed headphones. Each word was repeated 15 times (1/s), followed by 15 s of rest. Blood oxygenation level-dependent brain activations during blocks of stimulation versus rest were assessed with a 3-T Siemens Trio scanner and a 20-voxel spatial extent threshold. Memory was tested approximately 1.5 h after recovery with an auditory recognition task (chance performance = 33% correct). RESULTS: Scans showed widespread activations (P < 0.005, uncorrected) in the awake state, including bilateral superior temporal, frontal, and parietal cortex, right occipital cortex, bilateral thalamus, striatum, hippocampus, and cerebellum; more limited activations in the light state (bilateral superior temporal gyrus, right thalamus, bilateral parietal cortex, left frontal cortex, and right occipital cortex); and no significant auditory-related activation in the deep state. During recognition testing, subjects correctly selected 77 +/- 12% of words presented while they were awake as "old," versus 32 +/- 15 and 42 +/- 8% (P < 0.01) correct for the light and deep stages, respectively. CONCLUSIONS: Sevoflurane induces dose-dependent suppression of auditory blood oxygenation level-dependent signals, which likely limits the ability of words to be processed during anesthesia and compromises memory.
Acoustic Stimulation↗
Awareness: Monitoring versus remembering what happened.
BACKGROUND: Awareness during anesthesia is foremost assessed with postoperative interviews, which may underestimate its incidence. On-line monitors such as the Bispectral Index and patient response to verbal command are not necessarily commonly used. This study investigated response to command during deep sedation (Bispectral Index 60-70) and the ability of prevailing monitoring techniques to indicate awareness and predict recall. METHODS: The authors systematically assessed the response to command using the isolated forearm technique while monitoring electroencephalographic and hemodynamic variables. Fifty-six elective surgical patients were repeatedly given verbal instructions to squeeze the observer's hand during target-controlled infusion with propofol and alfentanil. After recovery, conscious recall was assessed with a short structured interview. RESULTS: Overall, 1,082 commands were given. No response was observed to 887 (82%) commands, an equivocal response was observed to 56 (5%) commands, and an unequivocal response was observed to 139 (13%) commands. Of the 37 patients (66%) with an unequivocal response to command ("awareness"), nine (25%) reported conscious recall after recovery. Their reports provided valuable insights as to how awareness may be adequately addressed. Hemodynamic variables poorly predicted awareness, whereas parameters derived from the encephalogram, especially the Bispectral Index, were highly significant predictors (P < 0.0001). Electroencephalographic parameters did not discriminate between patients with or without conscious recall, whereas heart rate and responsiveness to command did. CONCLUSIONS: The incidence of awareness is underestimated when conscious recall is taken as evidence. Awareness can be monitored on-line with behavioral and modern neurophysiologic measures. Providing feedback during intra-anesthetic awareness helps patients to cope with a potentially stressful situation.
Adult↗
Memory function during propofol and alfentanil anesthesia: predictive value of individual differences.
BACKGROUND: Conscious recall and implicit memory have been shown to depend on hypnotic state as measured by electroencephalographic (EEG) bispectral index (BIS). A third expression of memory (unconscious-controlled memory) was recently observed after moderate to light sedation (BIS, 70-80). The present study investigated memory function during deep sedation (BIS, 60-70). As memory effects are small, the authors studied potential predictors of individual differences in memory performance. METHODS: Memory function and speed of information processing were assessed in 56 outpatients before surgery. During propofol anesthesia supplemented with alfentanil, patients heard a series of words while anesthesia was titrated to BIS, 60-70. In between words, response to command was assessed using the Isolated Forearm Technique. The authors tested memory with a word stem completion task and process dissociation procedure to distinguish explicit from implicit effects. RESULTS: Mean (+/- SD) BIS during word presentation was 64.0 +/- 3. Patients with conscious recall of verbal commands (n = 9) did not recall or recognize presented words. Even so, the process dissociation procedure revealed evidence of memory by a significantly higher hit rate in the inclusion condition (0.26) than in the exclusion condition (0.12). Patients without conscious recall showed no evidence of memory for presented words. Hit scores correlated significantly with scores in the preoperative memory test (r = 0.35). CONCLUSIONS: The authors found evidence of weak explicit memory function during anesthesia titrated to BIS, 60-70. The observations strongly suggest that postoperative memory relates to awareness during anesthesia, but the nature of this relation remains unclear. Memory seems more likely in patients with good preoperative memory performance.
Adult↗