Cerebral state index response to incision: a clinical study in day-surgical patients

BACKGROUND: Inadequate anaesthesia, with somatic/autonomic response or awareness, is often revealed at intubation and surgical incision. Anaesthetic depth monitors should be able to prevent this risk. This explorative study examined the ability of the cerebral state monitor to predict autonomic/somatic responses to incision. METHODS: Forty-two ASA I-II day-surgical patients [19 men and 23 females; mean age 52 (29-79) years, mean weight 77 (50-118) kg] were induced clinically with fentanyl/propofol with sevoflurane after placement of the laryngeal mask airway. The cerebral state index (CSI) was blindly recorded 4 min prior to and 4 min after incision. RESULTS: During the 4 min prior to incision, the mean CSI was 45 (16-62) and increased by 9 (-13-40) when the mean value for the first 4 min after incision was subtracted from the value prior to incision, corresponding to a relative change of 21% (-21-118). The change in CSI did not show any consistent relation to the value before incision. Five patients showed minor movements after incision and six patients had > 25% increase in blood pressure. Neither CSI nor the change in index differed between patients who did or did not respond somatically or autonomically to incision. The last CSI value just prior to incision was 44 for non-responders and 40 and 42 for somatic and autonomic responders, respectively. CONCLUSION: The CSI in the majority of patients was within acceptable ranges during clinically adjusted anaesthesia prior to incision but seems not to be able to reliably predict an autonomic or somatic response to incision.     

Cerebral state monitor, a new small handheld EEG monitor for determining depth of anaesthesia: a clinical comparison with the bispectral index during day-surgery

BACKGROUND AND OBJECTIVE: The cerebral state index (CSI) derived from a new small handheld electroencephalogram monitor was studied during routine day surgical anaesthesia titrated according to the bispectral index (BIS). The objective was to determine the degree of agreement between the two monitors. METHODS: Anaesthesia was induced with propofol and fentanyl (0.1 mg) in 38 patients undergoing general anaesthesia for routine day-surgery. Maintenance anaesthesia (sevoflurane (20/38), desflurane (10/38) or propofol (8/38)) titrated by BIS XP (Aspect Medical, Natwick, MA, USA) and BIS and CSI (cerebral State Monitor, Danmeter; Odense, Denmark) index values were recorded every minute. No patient received muscle relaxation. Observer's Assessment of Alertness/Sedation rating scale was used to assess level of sedation. RESULTS: Pair-wise recordings (914) of CSI and BIS were collected. The indices showed similar pattern and decreased with increasing level of sedation, however with large ranges for each level of sedation. Median indices were similar during surgery (BIS: 50 (14-89); CSI: 51 (7-88)) and both indices increased (P 20% from BIS-index in 24% of readings, and on rare occasions CSI indices deviated >100% from the BIS reading. When BIS < 40, CSI decreased slower than BIS and with wider spreading. CONCLUSIONS: When used for day-surgery anaesthesia without muscle relaxation, CSI and BIS show similar patterns and numerical values but with the incidence of occasionally large discrepancies between pair-wise readings. Which monitor is the more dependable remains to be established and cannot be implied from this initial explorative study.     

Cerebral state index: comparison between pairwise registrations from the left and the right sides of the brain

Background. Lateralization of cerebral blood flow and EEG activityis known to vary during cognition, sleep and waking. In spiteof this, electrode placement for the cerebral state index (CSI^TM)monitor is not specified to a particular side of the brain.This study is designed to determine if pairwise registrationsdiffer for CSI measured simultaneously from the left or rightsides of the brain. Methods. In total, 25 ASA I–II patients undergoing electiveday surgery under general anaesthesia were recruited. Pairwiserecordings were made every minute from two CSI^TM monitors (CerebralState Monitor, Danmeter A/S; Odense, Denmark) connected to theleft and the right side of the head. Sedation was graded accordingto the observer's assessment of alertness/sedation rating scaleand correlated with CSI. Results. A large overlap of indices, of similar magnitude, foreach side of the brain was seen between different levels ofsedation. The agreement between pairwise registrations was high,correlation between the 584 CSI pairs of recordings left/rightwas r²=0.92. Conclusions. Despite known lateralization of the EEC, this studyfound a very high correlation in CSI derived simultaneouslyfrom the left and right sides of the brain by two independentmonitors. LMA® is the property of Intavent Ltd.     

Plasma concentrations following repeated rectal or intravenous administration of paracetamol after heart surgery

BACKGROUND: Paracetamol is commonly used for post-operative pain management in combination with more potent analgesics. The best route of paracetamol administration after major surgery, when oral intake may not be optimal, is not known. Our primary purpose was to study plasma concentrations after the 1st and 4th dose of 1 g of paracetamol given either rectally or intravenously (i.v.) after major surgery. METHODS: In this prospective, randomized study, 48 patients undergoing heart surgery were randomized upon arrival to the intensive care unit (ICU) to receive paracetamol every 6th hour either as suppositories or intravenous injections. In half the patients (n = 24), blood samples for paracetamol concentration were obtained before and 20, 40 and 80 min after the first dose. In the other patients (n = 24), additional samples were taken prior to, and at 20, 40, 80 min and 4 and 6 h after, the 4th dose. RESULTS: Plasma paracetamol concentration peaked (95 +/- 36 micromol/l) within 40 min after initial i.v. administration but did not increase within 80 min after the 1st suppository. Plasma concentration before the 4th dose was 74 +/- 51 and 50 +/- 27 in the rectal and i.v. groups, respectively. Paracetamol concentration peaked 20 min after the 4th dose for the i.v. patients (210 +/- 84 micromol/l) and declined to 99 +/- 27 micromol/l at 80 min as compared with the rectal patients 69 +/- 44 to 77 +/- 48 micromol/l. CONCLUSION: Both time course and peak plasma concentrations of paracetamol given rectally differ from the one seen after intravenous administration. The clinical impact of these differences needs further investigation.