Noninvasive Neuromonitoring of Hypothermic Circulatory Arrest in Aortic Surgery.

BACKGROUND AND AIMS: Circulatory arrest carries a high risk of neurological damage, but modern monitoring methods lack reliability, and is susceptible to the generalized effects of both anesthesia and hypothermia. The objective of this prospective, explorative study was to research promising, reliable, and noninvasive methods of neuromonitoring, capable of predicting neurological outcome after hypothermic circulatory arrest. MATERIALS AND METHODS: Thirty patients undergoing hypothermic circulatory arrest during surgery of the thoracic aorta were recruited in a single center and over the course of 4 years. Neuromonitoring was performed with a four-channel electroencephalogram montage and a near-infrared spectroscopy monitor. All data were tested off-line against primary neurological outcome, which was poor if the patient suffered a significant neurological complication (stroke, operative death). RESULTS: A poor primary neurological outcome seen in 10 (33%) patients. A majority (63%) of the cases were emergency surgery, and thus, no neurological baseline evaluation was possible. The frontal hemispheric asymmetry of electroencephalogram, as measured by the brain symmetry index, predicted primary neurological outcome with a sensitivity of 79 (interquartile range; 62%-88%) and specificity of 71 (interquartile range; 61%-84%) during the first 6 h after end of circulatory arrest. CONCLUSION: The hemispheric asymmetry of frontal electroencephalogram is inherently resistant to generalized dampening effects and is predictive of primary neurological outcome. The brain symmetry index provides an easy-to-use, noninvasive neuromonitoring method for surgery of the thoracic aorta and postoperative intensive care.

Long-Term Survival and Quality of Life After Hypothermic Circulatory Arrest in Aortic Surgery.

BACKGROUND AND AIMS:: Hypothermic circulatory arrest carries a high risk of mortality and neurological complications. An important part of assessing surgical treatment is the evaluation of long-term survival and postoperative health-related quality of life. MATERIAL AND METHODS:: In this prospective study, 30 patients undergoing hypothermic circulatory arrest during surgery of the thoracic aorta, and 31 comparison patients undergoing elective coronary artery surgery without hypothermic circulatory arrest were evaluated for long-term survival and health-related quality of life, using the RAND 36-Item Health Survey questionnaire. The results were compared to national age- and sex-matched reference populations of the chronically ill and healthy adults. RESULTS:: After 4.6-8.0 years, available study (88%) and comparison (59%) patients were interviewed. The life expectancy was similar with 4- and 8-year survival of 90%, and 87% for the study group, and 94%, and 94% for the comparison group, respectively (log rank test, p = 0.62). The RAND-36 scores for study and comparison groups were congruent in all dimensions, describing physical, mental, and social domains. The study patients' health-related quality of life results were similar to the national reference population with chronic illnesses. CONCLUSION:: After hypothermic circulatory arrest, patients undergoing surgery of the thoracic aorta achieve a similar long-term life expectancy and health-related quality of life as do patients undergoing coronary surgery without hypothermic circulatory arrest, and a health-related quality of life similar to the national reference population with chronic illnesses. These results justify operative treatment in this high-risk patient population.

Topographic electroencephalogram in children during mask induction of anaesthesia with sevoflurane.

BACKGROUND: Epileptiform patterns, spikes, polyspikes and periodic epileptiform discharges (PED) have been reported in electroencephalograms (EEGs) during anaesthesia induction with sevoflurane in healthy adults and children. Published recordings have been performed with a limited number of channels, and therefore the topographic distributions of these patterns are not known. METHODS: Twenty ASA I children aged 4-10 years undergoing routine operations were anaesthetized with 8% sevoflurane in 50%/50% oxygen and nitrous oxide using mask induction with controlled normoventilation. An EEG was recorded with a full 10-20 electrode system including orbitofrontal and ear electrodes, and a recording band of 0.016-70 Hz. Beat-to-beat heart rate (HR) was calculated off-line. RESULTS: Nineteen out of 20 children developed multifocal spikes and polyspikes with a maximum over the frontal lobes. Four patients developed suppression, which was almost continuous and lasted several minutes, and thereafter a continuous EEG resumed, a few spikes were seen and then a nonepileptiform pattern. In three children a couple of PED waves were seen at the onset of a continuous EEG. HR increased maximally before the onset of spikes. No motor phenomena were seen. CONCLUSION: These recordings confirm the epileptogenic property of sevoflurane in mask induction. The spikes and polyspikes had frontal multifocal maxima and may be missed in recordings from frontopolar electrodes used by depth-of-anaesthesia monitors. PED and burst suppression were synchronous over the whole cortex. Epileptiform activity was indiscernible from epileptiform waveforms without anaesthesia, such as the patterns seen in status epilepticus.

Surgical stress index as a measure of nociception/antinociception balance during general anesthesia.

BACKGROUND: No validated monitoring method is available for evaluating the nociception/antinociception balance. We assessed the surgical stress index (SSI), computed from finger photoplethysmographic waveform amplitudes and pulse-to-pulse intervals, in patients undergoing shoulder surgery under general anesthesia (GA) and interscalene plexus block and in patients with GA only. METHODS: In this prospective, randomized study in 26 patients, increased blood pressure (BP) or heart rate, movement, and coughing were considered to be signs of intraoperative nociception and were treated with alfentanil. GA was maintained with desflurane aiming at a State Entropy level of 50. Photoplethysmographic waveforms were collected from the contra-lateral arm to the surgery and SSI values from 0 (no surgical stress) to 100 (maximal surgical stress) were calculated off-line. RESULTS: Two minutes after skin incision, SSI had not increased in the plexus group and was lower in the plexus group (38 +/- 13) compared with the controls (58 +/- 13, P<0.005). Among the controls, 1 min before alfentanil administration, the SSI value was higher than during periods of adequate antinociception, 59 +/- 11 vs. 39 +/- 12 (P<0.01). The total cumulative need for alfentanil was higher in controls (2.7 +/- 1.2 mg) compared with the plexus group (1.6 +/- 0.5 mg; P=0.008). Tetanic stimulation to the ulnar region of the hand increased SSI significantly only among the patients with plexus block not covering the site of the stimulation. CONCLUSION: SSI values were lower in patients with plexus block covering the sites of nociceptive stimuli. In detecting nociceptive stimuli, SSI had better performance than heart rate, BP, or response entropy.

Operating room management: why, how and by whom?

Operating room (OR) is a cost-intensive environment, and it should be managed efficiently. When improving efficiency, shortening case duration by parallel processing, training of the resident surgeons, the choice of anesthetic methods, effective scheduling, and monitoring of the overall OR performance are important. When redesigning the OR processes, changes should be given a clear target and the achieved results monitored and reported to everyone involved. Advanced, reliable, and easy to use information technology solutions for OR management are under development. Pre-operative clinic and functionally designed facilities support efficiency. OR personnel must be kept motivated by clear management and leadership, supported by superiors.

Regular tramadol use does not affect the propofol dose requirement for induction of anaesthesia.

BACKGROUND AND OBJECTIVES: An increased risk of awareness during general anaesthesia in patients receiving tramadol has been reported. We studied whether tramadol affects the amount of propofol required for induction of anaesthesia. METHODS: In this prospective controlled study, we evaluated 46 patients, half of whom used tramadol regularly. Entropy indices, state entropy and response entropy, were used to assess the level of hypnosis. Patients were anaesthetized with a propofol infusion (1 mg kg(-1) min(-1)) until they first became unconscious, and further until they developed a burst suppression pattern in the electroencephalogram. The doses of propofol needed to reach these end-points were recorded. RESULTS: The amount (median, (range)) of propofol required for loss of consciousness was 2.0 (1.0-5.5) mg kg(-1) and 2.4 (0.9-8.3) mg kg(-1) (P=0.95) in the tramadol users and controls, respectively. The amount of propofol required for burst suppression was 5.8 (3.9-12.7) mg kg(-1) and 6.4 (2.9-15.1) mg kg(-1) (P=0.89) in the tramadol users and controls. There was no difference between the groups in state entropy and response entropy during different stages of induction of anaesthesia. CONCLUSIONS: Tramadol did not affect the dose of propofol required to achieve loss of consciousness or burst suppression pattern in electroencephalogram during induction of general anaesthesia. However, there was a ninefold inter-individual variation in propofol dose requirement for loss of consciousness and a fivefold variation for reaching burst suppression. Due to extensive inter-individual variability, monitoring the level of hypnosis during general anaesthesia using propofol may enhance the correct dosage.

Allocation of tasks between anesthesiologists and anesthesia nurses in Finland.

BACKGROUND: The shortage of anesthesiologists in Finland is worsening. A survey was carried out in 2003 among head anesthesiologists and head nurses to clarify current practice and the potentials for reorganizing tasks between anesthesiologists and anesthesia nurses. A national working group analyzed the results. METHODS: A questionnaire concerning doctor and nurse resources in anesthesiology, current allocation of tasks, and opinions on how these tasks could be reallocated was sent to 87 head anesthesiologists and 32 head nurses in 45 different hospitals. The answers from the doctors and nurses were compared. RESULTS: The response rate of doctors and nurses was 87% and 100%, respectively. In the enrolled hospitals there were 64 unoccupied positions for specialists in anesthesiology. The ratio of anesthesiologists to operation rooms (OR) they attended varied between 0.3 and 1.5. Doctors and nurses reported the allocation of tasks quite similarly. The great majority of respondents considered spinal, epidural, and interscalene brachial plexus blocks, and the induction of general anesthesia to be tasks that should be performed by an anesthesiologist. Very few respondents of either profession were willing to reallocate tasks so that nurses could deliver general anesthesia, including endotracheal intubation, even in low-risk patients. CONCLUSION: Nurses could be trained nationwide to perform procedures already performed by locally trained nurses in some hospitals. To cope with the shortage of anesthesiologists, other strategies must be adopted in addition to transferring part of their work load to nurses.

Experience of Mars therapy with and without transplantation in 101 patients with liver insufficiency.

Liver support devices are used to treat life-threatening organ dysfunction until a hepatic graft is available or recovery of the native liver. We used a blood purification system--molecular adsorbent recycling system (MARS)--that is based on removal of both protein-bound and water-soluble substances and toxins. Within 2.5 years we treated 101 patients, who were stratified to three subgroups: acute liver failure (ALF; n = 56), acute decompensation in chronic liver failure (AcOCh; n = 35) and liver graft failure (n = 10). MARS seems to be a promising therapy for ALF, allowing the patient's own liver to recover or to gain enough time to find a liver graft. The most promising results, namely the highest number of livers to recovery were observed among acute patients with liver failure due to a toxic etiology. However, we did not discover much benefit of MARS for patients with AcOCh without liver transplantation.

Time-frequency balanced spectral entropy as a measure of anesthetic drug effect in central nervous system during sevoflurane, propofol, and thiopental anesthesia.

BACKGROUND: Time-frequency balanced spectral entropy of electroencephalogram (EEG) and frontal electromyogram (FEMG) is a novel measure of hypnosis during anesthesia. Two Entropy parameters are described: Response entropy (RE) is calculated from EEG and FEMG; and State Entropy (SE) is calculated mainly from EEG. This study was performed to validate their performance during transition from consciousness to unconsciousness under different anesthetic agents. METHODS: Response entropy, SE [S/5 Entropy Module, M-ENTROPY (later in text: Entropy), Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland] and BIS (BIS XP, A-2000, Aspect Medical Systems, Newton, MA) data were collected from 70 patients; 30 anesthetized with propofol 2 mg kg-1, 20 with sevoflurane inhalation, and 20 with thiopental 5 mg kg-1. Loss and regaining of consciousness (LOC, ROC) was tested every 10 s, and sensitivity, specificity, and prediction probability (Pk) were calculated. Behavior of the indices was studied. RESULTS: Sensitivity, specificity, and Pk values for consciousness were high and similar for all indices. During regaining of consciousness after propofol bolus, RE, SE, and BIS values recovered by 81 +/- 22%, 75 +/- 26%, and 59 +/- 18% (mean +/- SD), respectively, from the minimum relative to their baseline. After thiopental bolus, RE, SE, and BIS values recovered by 86+/-21%, 88 +/- 13%, and 63 +/- 14%, respectively. The relative rise was higher in RE and SE compared with BIS (P < 0.01). During deep levels of hypnosis, RE and SE decreased monotonously as a function of burst suppression ratio, while BIS showed biphasic behavior. On average, RE indicated emergence from anesthesia 11 s earlier than SE, and 12.4 s earlier than BIS. CONCLUSIONS: All indices, RE, SE, and BIS, distinguished excellently between conscious and unconscious states during propofol, sevoflurane, and thiopental anesthesia. During burst suppression, Entropy parameters RE and SE, but not BIS, behave monotonously. During regaining of consciousness after a thiopental or propofol bolus, RE and SE values recovered significantly closer to their baseline values than did BIS. Response entropy indicates emergence from anesthesia earlier than SE or BIS.

Experience with albumin dialysis in five patients with severe overdoses of paracetamol.

Five patients in whom the serum paracetamol levels or the amount of ingested paracetamol was high enough to cause severe liver injury were treated with N-acetyl-cysteine (NAC) and a molecular absorbant recirculating system (MARS). MARS treatment was started as early as possible in order to prevent or retard the development of hepatocyte necrosis. Four of our five patients survived without liver transplantation, and one died due to brain oedema. The early commencement with NAC and MARS treatments in paracetamol intoxication might give enough time for the liver to regenerate and thus avoid liver transplantation.

Sevoflurane mask induction of anaesthesia is associated with epileptiform EEG in children.

BACKGROUND: Sevoflurane inhalation induction of anaesthesia is widely used in paediatric anaesthesia. We have found that this method is frequently associated with epileptiform electroencephalogram (EEG) in adults, especially if controlled hyperventilation is used. METHODS: We assessed EEG during sevoflurane inhalation induction in 31 children, aged 2-12 yr. Anaesthesia was induced with 8% sevoflurane in O2 in N2O 1:2. The patients were randomized to undergo controlled ventilation (CV group), or to breathe spontaneously (SB group) for 5 min. EEG was recorded as were noninvasive blood pressure and heart rate (HR). EEG recordings were classified by a clinical neurophysiologist. RESULTS: Three different types of interictal epileptiform discharge were detected. Suppression with spikes (SSP) was found in 25% and 0% in the CV and SB groups, rhythmic polyspikes (PSR) in 44% and 20%, and periodic epileptiform discharges (PED) in 44% and 0% (P<0.01), respectively. The incidence of all different types of interictal epileptiform discharge (SSP+PSR+PED) was 88% and 20% (P<0.001), respectively. Epileptiform EEG was associated with increased heart rate and blood pressure during anaesthetic induction. CONCLUSION: Both ventilation modes produced epileptiform EEG. With controlled ventilation, epileptiform discharges were seen in 88% of children. This warrants further studies of the suitability of this induction type in general, and especially in children with epilepsy.

Epileptiform EEG during sevoflurane mask induction: effect of delaying the onset of hyperventilation.

BACKGROUND: Hyperventilation during sevoflurane-N2O-O2 mask induction in adults is associated with a hyperdynamic circulatory response and epileptiform electroencephalogram (EEG). We tested the hypothesis that delaying onset of hyperventilation will prevent severe (periodic) epileptiform EEG and hyperdynamic response. METHODS: Thirty patients were randomized to receive either delayed (group D, n=15) or immediate (group I, n=15) onset of hyperventilation during sevoflurane (8% in N2O 50%) mask inhalation induction with single-breath method for unconsciousness. Fifteen patients were allowed to breathe spontaneously for 2 min after loss of consciousness and controlled hyperventilation (ETCO2 <4%) was started thereafter. In 15 patients controlled hyperventilation was started immediately after loss of consciousness. EEG was recorded, and mean arterial pressure (MAP) and heart rate (HR) registered. RESULTS: Epileptiform EEG patterns were seen in 13 patients in group I and in 9 patients in group D (n.s.). Periodic epileptiform discharges (PED) tended to occur more often in group I (P=0.07). Heart rate and MAP were higher in group I than in group D from 2 min to 3 min (P < 0.05), and both HR and MAP rose significantly from the baseline in group I. In group D, HR but not MAP rose significantly from baseline. CONCLUSION: Regardless of its timing, hyperventilation at a high sevoflurane concentration produced severe epileptiform EEG with a hyperdynamic response. PED tended to occur more often with immediate onset of hyperventilation.

Epileptiform electroencephalogram during mask induction of anesthesia with sevoflurane.

BACKGROUND: Sevoflurane is suggested as a suitable anesthetic agent for mask induction in adults. The authors recently found that hyperventilation during sevoflurane-nitrous oxide-oxygen mask induction is associated with cardiovascular hyperdynamic response. We tested the hypothesis that the hyperdynamic response can be explained by electroencephalography (EEG) findings. METHODS: Thirty women were randomly allocated to receive sevoflurane-nitrous oxygen-oxygen mask induction using a single-breath method, followed by either spontaneous breathing (n = 15) or controlled hyperventilation (n = 15) for 6 min. EEG was recorded. Blood pressure and heart rate were recorded at 1-min intervals. RESULTS: Epileptiform EEG activity (spikes or polyspikes) was seen in all patients with controlled hyperventilation, and in seven patients with spontaneous breathing (P < 0.01). Jerking movements were seen in three patients with controlled hyperventilation. In the controlled hyperventilation group, heart rate increased 54% from baseline at 4 min after induction (P < 0.001). Mean arterial pressure increased 17% (P < 0.05), peaking at 3 min. In the spontaneous breathing group, heart rate showed no change, and mean arterial pressure decreased by 14% (P < 0.01) at 6 min. Heart rate and mean arterial pressure differed significantly between the groups from 2 min after beginning of the induction to the end of the trial. An increase in heart rate of more than 30% from baseline always was associated with epileptiform EEG activity. CONCLUSIONS: Sevoflurane mask induction elicits epileptiform EEG patterns. These are associated with an increase in heart rate in patients with controlled hyperventilation and also during spontaneous breathing of sevoflurane.

Sevoflurane requirement for laparoscopic tubal ligation: an electroencephalographic bispectral study.

It has been shown in healthy volunteers that a concentration of volatile anaesthetic lower than 1 minimum alveolar concentration provides unconsciousness. We tested the hypothesis that, using the electroencephalogram bispectral index, less than 1 minimum alveolar concentration of sevoflurane can produce unconsciousness in patients. Anaesthesia was induced and maintained with sevoflurane in N2O and O2 (33%) in 32 ASA I-II women undergoing laparoscopic tubal ligation. For the first patient, the sevoflurane concentration was adjusted to 1 minimum alveolar concentration with an end-tidal concentration of 0.7%. The electroencephalogram bispectral index values were used to determine the concentration to be used for the next patient. The ED50 (effective dose) measured using end tidal concentrations of sevoflurane for laparoscopic tubal ligation in a 40-year-old patient was 0.70% (CI 95%: 0.63-0.77) and ED95 0.83% (CI 95%: 0.75-0.90). None of the patients had any operation-associated recall. It is concluded that the sevoflurane concentration needed for laparoscopic tubal ligation is not lower than 1 minimum alveolar concentration.

Transient hyperdynamic response associated with controlled hypocapneic hyperventilation during sevoflurane-nitrous oxide mask induction in adults.

UNLABELLED: We assessed hemodynamic variables during sevoflurane face mask anesthetic induction in female ASA physical status I or II patients. Anesthesia was induced with a single-breath inhalation method with 8% sevoflurane in 50% nitrous oxide in oxygen. Thirty patients were randomized either to breathe spontaneously (SB group, n = 15) or to receive controlled ventilation (CV group, n = 15) for 6 min after the loss of consciousness. Noninvasive blood pressure and heart rate (HR) were recorded at 1-min intervals. Mean +/- SD HR increased from 83+/-18 to 112+/-24 bpm at 4 min in the CV group (P < 0.001 between groups and within group compared with baseline). Mean arterial pressure increased from 97+/-9 to 106+/-26 mm Hg at 4 min in the CV group, which was significantly higher than that in the SB group (P < 0.01). In the SB group, mean arterial pressure decreased significantly, from 96+/-8 to 78+/-13 mmHg, at 6 min (P < 0.001), and HR remained unchanged. Therefore, hyperventilation should be avoided during the induction of sevoflurane anesthesia via a mask. IMPLICATIONS: In this randomized, prospective study, we found that controlled hypocapneic hyperventilation delivered manually during sevoflurane/ N2O/O2 mask induction was associated with a significant transient hyperdynamic response. This kind of hemodynamic arousal can be detrimental to many patients and can be avoided by conducting sevoflurane mask induction with unassisted spontaneous breathing.

EEG bispectral index monitoring in sevoflurane or propofol anaesthesia: analysis of direct costs and immediate recovery.

BACKGROUND: Recent studies have suggested that electroencephalogram (EEG) bispectral index (BIS) monitoring can improve recovery after anaesthesia and save money by shortening patients' postoperative stay. We wanted to evaluate the direct costs of BIS monitoring and to measure immediate recovery after anaesthesia in patients with or without BIS monitoring. METHODS: Eighty patients undergoing gynaecological surgery were studied. At first, 40 patients were randomized to receive either propofol or sevoflurane anaesthesia. In these patients, BIS was collected but the information was not displayed. Thereafter, the anaesthesiologists were trained to follow and understand the BIS information, and 40 patients were anaesthetized with aid of the monitoring. Recovery times were measured by a study coordinator. Drug consumption was calculated. RESULTS: BIS monitoring improved the immediate recovery after propofol anaesthesia, while no differences were seen in patients receiving sevoflurane. The consumption of both propofol and sevoflurane decreased significantly (29% and 40%, respectively). BIS monitoring increased direct costs in these patients; the break-even times (704 min for propofol and 282 min for sevoflurane) were not reached. CONCLUSION: BIS monitoring decreased the consumption of both propofol and sevoflurane and hastened the immediate recovery after propofol anaesthesia. Detailed cost analysis showed that the monitoring increased direct costs of anaesthesia treatment in these patients, mainly due to the price of special EEG electrodes used for relatively short anaesthesias.