Biomedical subjects

C Kerssens

Publications and source records attributed to C Kerssens.

3 recordsLinked to original sources

PubMed2001

Auditory information processing during adequate propofol anesthesia monitored by electroencephalogram bispectral index.

UNLABELLED: Memory for intraoperative events may arise from inadequate anesthesia when the hypnotic state is not continuously monitored. Electroencephalogram bispectral index (BIS) enables monitoring of the hypnotic state and titration of anesthesia to an adequate level (BIS 40 to 60). At this level, preserved memory function has been observed in trauma patients. We investigated memory formation in elective surgical outpatients during target-controlled propofol anesthesia supplemented with alfentanil. While BIS remained between 40 and 60, patients listened to a tape with either familiar instances (exemplars) from two categories (Experimental [E] group, n = 41) or bird sounds (Control [C] group, n = 41). After recovery, memory was tested directly and indirectly. BIS during audio presentation was on average (+/- SD) 44 +/- 5 and 46 +/- 5 for Groups E and C, respectively. No patient consciously recalled the intraoperative period, nor were presented words recognized reliably (Group E, 0.9 +/- 0.8 hits; Group C, 0.8 +/- 0.8 hits) (P = 0.7). When asked to generate category exemplars, Group E named 2.10 +/- 1.0 hits versus 1.98 +/- 1.0 in Group C (P = 0.9). We found no explicit or implicit memory effect of familiar words presented during adequate propofol anesthesia at BIS levels between 40 and 60 in elective surgical patients. IMPLICATIONS: This study suggests that stable levels of adequate hypnosis may prevent information processing and memory formation during general anesthesia and supports the feasibility of electroencephalogram bispectral index as a monitor of adequate anesthesia.

Acoustic Stimulation↗

PubMed2000

Memory formation during general anesthesia for emergency cesarean sections.

BACKGROUND: Occurrence of explicit memory (i.e., conscious recall) has been reported especially after surgical procedures in which anesthesia is considered to be "light." In addition, previous research has shown that implicit memory (e.g., improved memory test performance in absence of conscious recall) decreases with increasing hypnotic state. The current study investigated explicit and implicit memory during emergency cesarean sections with consistently light levels of hypnotic state. METHOD: Words were presented via headphones, and the bispectral index was recorded throughout surgery. Memory for the presented words was tested after recovery with a word-stem completion test. Using both parts of the process dissociation procedure allowed separation of explicit and implicit memory. In the "inclusion" part of the process dissociation procedure, patients are asked to complete word stems, if possible, with the corresponding words recalled from the intraoperative presentation. In the "exclusion" part, patients are instructed to avoid the words presented intraoperatively and to use other words instead. In the absence of recall, patients are asked to use the first word that comes to mind. RESULTS: The mean bispectral index during word presentation was 76.3 (+/-3.0). On average, the 24 patients were able to make correct inclusion-exclusion decisions: In the inclusion part, hit rates (i.e., the probability of responding with a word presented during surgery) were higher than base rates (0.37 vs. 0.31), whereas in the exclusion part hit rates were lower (0.23 vs. 0.28). Importantly, the patients made these inclusion-exclusion decisions without being able to consciously recall the words presented during surgery. CONCLUSIONS: This study shows that if words are presented at relatively light levels of anesthesia, patients are able to control their inclusion-exclusion decisions. This weak form of explicit memory can occur in the absence of conscious recall.

Adult↗

PubMed1999

Dependence of explicit and implicit memory on hypnotic state in trauma patients.

BACKGROUND: It is still unclear whether memory of intraoperative events results entirely from moments of inadequate anesthesia. The current study was designed to determine whether the probability of memory declines with increasing depth of the hypnotic state. METHOD: A list of words was played via headphones during surgery to patients who had suffered acute trauma. Several commonly used indicators of anesthetic effect, including the bispectral index, were recorded during word presentation. First, these indicators served as predictors of the memory performance in a postoperative word stem completion test. Second, general memory performance observed in the first part was separated into explicit and implicit memory using the process dissociation procedure, and then two models of memory were compared: One model assumed that the probability of explicit and implicit memory decreases with increasing depth of hypnotic state (individual differences model), whereas the other assumed equal memory performance for all patients regardless of their level of hypnotic state. RESULTS: General memory performance declined with decreasing bispectral index values. None of the other indicators of hypnotic state were related to general memory performance. Memory was still significant at bispectral index levels between 60 and 40. A comparison of the two models of memory resulted in a better fit of the individual differences model, thus providing evidence of a dependence of explicit and implicit memory on the hypnotic state. Quantification of explicit and implicit memory revealed a significant implicit but no reliable explicit memory performance. CONCLUSIONS: This study clearly indicates that memory is related to the depth of hypnosis. The observed memory performance should be interpreted in terms of implicit memory. Auditory information processing occurred at bispectral index levels between 60 and 40.

Adolescent↗