Skin conductance monitoring compared with bispectral index ® monitoring to assess emergence from general anaesthesia using sevoflurane and remifentanil

Monitoring surgical nociception using multisensor physiological models

Monitoring nociception, the flow of information associated with harmful stimuli through the nervous system even during unconsciousness, is critical for proper anesthesia care during surgery. Currently, this is done by tracking heart rate and blood pressure by eye. Monitoring objectively a patient's nociceptive state remains a challenge, causing drugs to often be over- or underdosed intraoperatively. Inefficient management of surgical nociception may lead to more complex postoperative pain management and side effects such as postoperative cognitive dysfunction, particularly in elderly patients. We collected a comprehensive and multisensor prospective observational dataset focused on surgical nociception (101 surgeries, 18,582 min, and 49,878 nociceptive stimuli), including annotations of all nociceptive stimuli occurring during surgery and medications administered. Using this dataset, we developed indices of autonomic nervous system activity based on physiologically and statistically rigorous point process representations of cardiac action potentials and sweat gland activity. Next, we constructed highly interpretable supervised and unsupervised models with appropriate inductive biases that quantify surgical nociception throughout surgery. Our models track nociceptive stimuli more accurately than existing nociception monitors. We also demonstrate that the characterizing signature of nociception learned by our models resembles the known physiology of the response to pain. Our work represents an important step toward objective multisensor physiology-based markers of surgical nociception. These markers are derived from an in-depth characterization of nociception as measured during surgery itself rather than using other experimental models as surrogates for surgical nociception.

Cerebral Tissue Oxygen Saturation Correlates with Emergence from Propofol-Remifentanil Anesthesia: An Observational Cohort Study

Anesthesia emergence is accompanied by changes in cerebral circulation. It is unknown whether cerebral tissue oxygen saturation (SctO₂) could be an indicator of emergence. Changes in SctO₂, bispectral index (BIS), mean arterial pressure (MAP), and heart rate (HR) were evaluated during the emergence from propofol-remifentanil anesthesia. At the time of cessation of anesthetic delivery, SctO₂, BIS, MAP, and HR values were recorded as baseline. The changes of these parameters from the baseline were recorded as Δ SctO₂, Δ BIS, Δ MAP, and Δ HR. The behavioral signs (body movement, coughing, or eye opening) and response to commands (indicating regaining of consciousness) were used to define emergence states. Prediction probability (Pk) was used to examine the accuracy of SctO₂, BIS, MAP, and HR as indicators of emergence. SctO₂ showed an abrupt and distinctive increase when appearing behavioral signs. BIS, MAP, and HR, also increased but with a large inter-individual variability. Pk value of Δ SctO₂ was 0.97 to predict the appearance behavioral signs from 2 min before that, which was much higher than the Pk values of Δ BIS (0.81), Δ MAP (0.71) and Δ HR (0.87). The regaining of consciousness was associated with a further increase in the SctO₂ value.

Available Instruments to Assess Pain in Infants

Pain assessment in newborns and infants is challenging for clinicians. Although behavioral and behavioral-physiological scales are validated pain assessment instruments, their use in this age group has significant limitations. In this review, we summarize the methods currently available for assessing pain in neonates and infants. It is possible that these pain detection methods are also useful for assessing the quality of anesthesia and analgosedation in these populations. Further research should be aimed at confirming the usefulness of these tools in infants and identifying additional pain assessment options for clinical practice.

[Nociception monitoring : Method for intraoperative opioid control?]

The intraoperative dosing of opioids is a challenge in routine anesthesia as the potential effects of intraoperative overdosing and underdosing are not completely understood. In recent years an increasing number of monitors were approved, which were developed for the detection of intraoperative nociception and therefore should enable a better control of opioid titration. The nociception monitoring devices use either continuous hemodynamic, galvanic or thermal biosignals reflecting the balance between parasympathetic and sympathetic activity, measure the pupil dilatation reflex or the nociceptive flexor reflex as a reflexive response to application of standardized nociceptive stimulation. This review article presents the currently available nociception monitors. Most of these monitoring devices detect nociceptive stimulations with higher sensitivity and specificity than changes in heart rate, blood pressure or sedation depth monitoring devices. There are only few studies on the effect of opioid titration guided by nociception monitoring and the possible postoperative benefits of these devices. All nociception monitoring techniques are subject to specific limitations either due to perioperative confounders (e.g. hypovolemia) or special accompanying medical conditions (e.g. muscle relaxation). There is an ongoing discussion about the clinical relevance of nociceptive stimulation in general anesthesia and the effect on patient outcome. Initial results for individual monitor systems show a reduction in opioid consumption and in postoperative pain level. Nevertheless, current evidence does not enable the routine use of nociception monitoring devices to be recommended as a clear beneficial effect on long-term outcome has not yet been proven.

The prediction probabilities for emergence from sevoflurane anesthesia in children: A comparison of the perfusion index and the bispectral index

BACKGROUND

Predicting recovery of consciousness is one of the most essential functions of anesthesia depth monitors in anesthesia practice. Perfusion index and bispectral index are 2 indicators of the anesthesia depth monitoring with different working principles. The progression of the anesthesia emergence stages reflected by those monitors has not been well understood, especially in pediatric patients. The goals of this study were to compare the prediction probabilities of perfusion index and bispectral index in predicting awakening and in differentiating the different levels of arousal during emergence after sevoflurane anesthesia in children undergoing open inguinal hernia repairs.

METHODS

Forty-five patients, aged 1 to 5 years, ASA Status I or II and scheduled for elective open inguinal hernia repairs under general anesthesia were enrolled. The perfusion index and bispectral index were monitored simultaneously during anesthesia recovery. The University of Michigan Sedation Scale was applied to evaluate the clinical arousal levels during emergence. The prediction probability was used to assess the performance of perfusion index and bispectral index in predicting awakening and distinguishing different levels of arousal corresponding to the University of Michigan Sedation Scale during recovery.

RESULTS

The prediction probability of perfusion index (Pk_PI-Awakening  = .81, 95% CI 0.73-0.89) in differentiating full consciousness from unconsciousness during recovery was comparable to that of bispectral index (Pk_{BIS- Awakening}  = .86, 95% CI 0.79-0.92) (P = .47). The prediction probability for perfusion index (Pk_PI-UMSS  = .61, 95% CI 0.55-0.73) and bispectral index (Pk_BIS-UMSS  = .64, 95% CI 0.53-0.69) had similar performance in distinguishing different University of Michigan Sedation Scale levels.

CONCLUSION

Both the perfusion index and bispectral index performed comparably well in predicting awakening and different arousal levels when emerging from sevoflurane anesthesia in children.

Monitoring depth of anesthesia: from consciousness to nociception. A window on subcortical brain activity

Anesthesia results from several inhibitor processes, which interact to lead to loss of consciousness, amnesia, immobility, and analgesia. The anesthetic agents act on the whole brain, the cortical and subcortical areas according to their receptor targets. The conscious processes are rather integrated at the level of the cortical neuronal network, while the nonconscious processes such as the nociception or implicit memory require subcortical processing. A reliable and meaningful monitoring of depth of anesthesia should provide assessment of these different processes. Besides the EEG monitoring which gives mainly information on cortical anesthetic effects, it would be relevant to have also a subcortical feedback allowing an assessment of nociception. Several devices have been proposed in this last decade, to give us an idea of the analgesia/nociception balance. Up to now, most of them are based on the assessment of the autonomic response to noxious stimulation. Among the emerging clinical devices, we can mention those which assess vascular sympathetic response (skin conductance), cardiac and vascular sympathetic response (surgical pleth index), parasympathetic cardiac response (analgesia nociception index), and finally the pupillometry which is based on the assessment of the pupillary reflex dilatation induced by nociceptive stimulations. Basically, the skin conductance might be the most adapted to assess the stress in the awake or sedated neonate, while the performances of this method appear disappointing under anesthesia. The surgical pleth index is still poorly investigated in children. The analgesia nociception index showed promising results in adults, which have to be confirmed, especially in children and in infants, and lastly pupillometry, which can be considered as reliable and reactive in children as in adults, but which is still sometimes complicated in its use.

Pain assessment in children undergoing venipuncture: the Wong-Baker faces scale versus skin conductance fluctuations

The aim of this study was to evaluate the efficacy of the subjective Wong–Baker faces pain rating scale (WBFS) and of the objective skin conductance fluctuation (SCF) test in assessing pain in children undergoing venipuncture. One-hundred and fifty children (aged 5–16 years) entered the study. All underwent venipuncture at the antecubital fossa to collect blood specimens for routine testing in the same environmental conditions. After venipuncture, the children indicated their pain intensity using the WBFS, whereas the number of SCFs was recorded before, during and after venipuncture. So, pain level was measured in each child with WBFS and SCF. We found that the level of WBFS-assessed pain was lower in all children, particularly those above 8 years of age, than SCF-assessed pain (p < 0.0001). Moreover, the number of SCFs was significantly higher during venipuncture than before or after venipuncture (p < 0.0001). At multivariate regression analysis, age and previous experience of venipuncture influenced the WBFS (β = −1.81, p < 0.001, and β = −0.86, p < 0.001, respectively) but not SCFs. In conclusion, although both procedures can be useful for research and clinical practice, our findings show that WBFS was affected by age and previous venipuncture, whereas SCF produced uniform data. If verified in other studies, our results should be taken into account when using these tools to evaluate pain in children.

Acute pain therapy in postanesthesia care unit directed by skin conductance: a randomized controlled trial

Background

After surgery, effective and well-directed acute pain therapy is a necessary and integral part of the overall treatment plan. Generally, the assessment of pain intensity depends on a patient’s self-evaluation using scoring systems such as numeric rating scales (NRS, 0 to 10). Recently, a “Pain Monitor” was commercially provided which is based on measurements of fluctuations of skin conductance (NFSC). In this randomized, controlled, single-blind trial, possible benefits of this certain device were studied.

Methods

Postoperative patients (n = 44) were randomly assigned to a test or a control group during their stay in the postanesthesia care unit (PACU). All patients were treated and monitored according to internal hospital standards. Whereas all patients systematically evaluated their pain each 15 min, test group patients were additionally addressed when NFSC exceeded a predefined level. In cases of NRS≥5 during a routine elevation or in between, pain relief was achieved by standard procedures irrespective of group allocation.

Results

During their stay in PACU, both test and control groups experienced a significant decrease in NRS as a consequence of pain therapy. No significant differences in mean NRS or in NFSC values were found between the test and control groups. No correlation was observed between NRS and NFSC.

Conclusion

Postoperative patients experience diverse stressors, such as anxiety, disorientation, shivering, sickness and pain. Although the application of continuous pain monitoring would be meaningful in this clinical setting, the tested device failed to distinguish pain from other stressors in postoperative adult patients.

Trial Registration

German Clinical Trials Register DRKS00000755.

Arousal modulation of memory and amygdala-parahippocampal connectivity: a PET-psychophysiology study in specific phobia

Phobic fear is accompanied by intense bodily responses modulated by the amygdala. An amygdala moderated psychophysiological measure related to arousal is electrodermal activity. We evaluated the contributions of electrodermal activity to amygdala-parahippocampal regional cerebral blood flow (rCBF) during phobic memory encoding in subjects with spider or snake phobia. Recognition memory was increased for phobia-related slides and covaried with rCBF in the amygdala and the parahippocampal gyrus. The covariation between parahippocampal rCBF and recognition was related to electrodermal activity suggesting that parahippocampal memory processes were associated with sympathetic activity. Electrodermal activity further mediated the amygdala effect on parahippocampal activity. Memory encoding during phobic fear therefore seems contingent on amygdala's influence on arousal and parahippocampal activity.

Recent advance in patient monitoring

Recent advance in technology has developed a lot of new aspects of clinical monitoring. We can monitor sedation levels during anesthesia using various electroencephalographic (EEG) indices, while it is still not useful for anesthesia depth monitoring. Some attempts are made to monitor the changes in sympathetic nerve activity as one of the indicators of stress, pain/analgesia, or anesthesia. To know the balance of sympathetic and parasympathetic activity, heart rate or blood pressure variability is investigated. For trend of cardiac output, low invasive monitors have been investigated. Improvement of ultrasound enables us to see cardiac structure and function continuously and clearer, increases success rate and decreases complication of central venous puncture and various kinds of nerve blocks. Without inserting an arterial catheter, trends of arterial oxygen tension or carbon dioxide tension can be monitored. Indirect visualization of the airway decreases difficult intubation and makes it easier to teach tracheal intubation. The changes in blood volume can be speculated non-invasively. Cerebral perfusion and metabolism are not ordinary monitored yet, but some studies show their usefulness in management of critically ill. This review introduces recent advances in various monitors used in anesthesia and critical care including some studies of the author, especially focused on EEG and cardiac output. However, the most important is that these new monitors are not almighty but should be used adequately in a limited situation where their meaning is confirmed.

New parameters of skin conductance compared with bispectral index ® monitoring to assess emergence from total intravenous anaesthesia

BACKGROUND

Arousal after total i.v. anaesthesia (TIVA) has been reported to be detectable by monitoring the number of fluctuations per second (NFSC), a parameter of skin conductance (SC). However, compared with monitoring of the bispectral index (BIS), the predictive probability of NFSC was significantly lower. The aim of this study was to determine the value of the two new, not yet published parameters of SC, area under the curve (AUC) methods A and B, for monitoring emergence from TIVA compared with monitoring of NFSC and BIS.

METHODS

Twenty-five patients undergoing surgery were investigated. NFSC, AUC A, AUC B, BIS, and haemodynamic parameters (mean arterial pressure and heart rate) were recorded simultaneously. The performance of the monitoring devices in distinguishing between the clinical states 'steady-state anaesthesia', 'first clinical reaction', and 'extubation' were compared using the method of prediction probability (Pk) calculation.

RESULTS

BIS showed the best performance in distinguishing between 'steady-state anaesthesia' vs 'first reaction' (Pk BIS 0.95; NFSC 0.73; AUC A 0.54; AUC B 0.62) and 'steady-state anaesthesia' vs 'extubation' (Pk BIS 0.99; NFSC 0.73; AUC A 0.71; AUC B 0.67). However, the time from first BIS>60/SC>0 to a first clinical reaction was significantly shorter for BIS (median BIS((R)) 180 s; NFSC 780 s; AUC A 750 s; AUC B 690 s; P < 0.001).

CONCLUSIONS

AUC A and AUC B did not improve accuracy of SC monitoring in patients waking after TIVA.

Skin conductance monitoring compared with Bispectral Index to assess emergence from total i.v. anaesthesia using propofol and remifentanil

BACKGROUND

Arousal after sevoflurane anaesthesia has been detectable by monitoring changes in skin conductance (SC) with similar accuracy as monitoring Bispectral Index (BIS). As SC monitoring detects changes in sympathetic tone, the measurements might be confounded by the sympatholytic properties of propofol, a component of total i.v. anaesthesia (TIVA). Therefore in this study, monitoring of SC during emergence from TIVA was compared with the monitoring of BIS.

METHODS

Twenty-five patients undergoing plastic surgery were investigated. The number of fluctuations of SC per second (NFSC), BIS and haemodynamic variables [systolic blood pressure (SBP) and heart rate (HR)] were recorded simultaneously. The performance of the monitoring devices in distinguishing between the clinical states 'steady-state anaesthesia', 'first clinical reaction' and 'extubation' were compared using the method of prediction probability (Pk) calculation.

RESULTS

BIS((R)) showed the best performance in distinguishing between 'steady-state anaesthesia' and 'first reaction' (Pk BIS 0.99 vs NFSC 0.80; P<0.01), and 'steady-state anaesthesia' and 'extubation' (Pk BIS) 1.00 vs NFSC 0.91; P<0.05); the time from first change of BIS or NFSC to a first clinical reaction was significantly longer for NFSC (median BIS 135 s vs NFSC 191 s; P<0.05). BIS and NFSC performed better in distinguishing between the investigated clinical states than SBP and HR.

CONCLUSIONS

In this study, BIS was found to predict arousal with a higher probability but slower response times than NFSC in patients waking after TIVA.