Monitoring nociception during general anesthesia with cardiorespiratory coherence

Nociception monitoring tools using autonomic tone changes for intraoperative analgesic guidance in pediatric patients

Nociception monitoring devices using changes in autonomic nervous system activity have been developed in numerous ways. Although there have been few studies conducted on children, compared to the relatively higher number of studies on adults, most of the nociception monitors in children, as in adults, appear to be more useful than the standard clinical practice that uses hemodynamic parameters in the evaluation and treatment of intraoperative nociception (pain) during general anesthesia. Particularly, when monitoring the surgical pleth index (SPI) in anesthetized children, the application of a new target range of SPI values (≤ 40) to the SPI monitoring criteria seems to be necessary for providing a more proper intraoperative analgesia. The analgesia nociception index (ANI) shows promising results in anesthetized adults, and recently, positive results along with cardiorespiratory coherence have been reported in pediatric patients. Newborn infant parasympathetic evaluation (NIPE) could be useful for providing adequate analgesia in newborns, infants, and children under 2 years of age in anesthetized or awake states. In cases of skin conductance and pupillometry, further studies are needed. Understanding the pros, cons, and limitations of these nociception monitoring tools will provide more effective and safe intraoperative analgesia to pediatric patients undergoing general anesthesia, and it may also help to plan and conduct promising research on the use of perioperative nociception monitoring in pediatric patients in the future.

Monitoring regional blockade

This review attempts to draw on the published literature to address three practical clinical questions. First, what means of testing the degree of regional blockade pre-operatively are available, and can eventual success or failure be determined soon after injection? Second, is it possible to predict if a block inserted after the induction of general anaesthesia will be effective when the patient wakes? Third, what features, and what duration, should cause concern when a block does not resolve as expected after surgery? Although the relevant literature is limited, we recommend testing of multiple sensory modalities before surgery commences; temperature and thermographic changes may offer additional early warning of success or failure. There are a number of existing methods of assessing nociception under general anaesthesia, but none has yet been applied to gauge the onset of a regional block. Finally, criteria for further investigation and neurological referral when block symptoms persist postoperatively are presented.

Correlation of changes in hemodynamic response as measured by cerebral optical spectrometry with subjective pain ratings in volunteers and patients: a prospective cohort study

Purpose

Noninvasive cerebral optical spectrometry is a promising candidate technology for the objective assessment physiological changes during pain perception. This study’s primary objective was to test if there was a significant correlation between the changes in physiological parameters as measured by a cerebral optical spectrometry-based algorithm (real-time objective pain assessment [ROPA]) and subjective pain ratings obtained from volunteers and laboring women. Secondary aims were performance assessment using linear regression and receiver operating curve (ROC) analysis.

Patients and methods

Prospective cohort study performed in Human Pain Laboratory and Labor and Delivery Unit. After institutional review board approval, we evaluated ROPA in volunteers undergoing the cold pressor test and in laboring women before and after epidural or combined spinal epidural placement. Linear regression was performed to measure correlations. ROCs and corresponding areas under the ROCs (AUC), as well as Youden’s indices, as a measure of diagnostic effectiveness, were calculated.

Results

Correlations between numeric rating scale or visual analog scale and ROPA were significant for both volunteers and laboring women. AUCs for both volunteers and laboring women with numeric rating scale and visual analog scale subjective pain ratings as ground truth revealed at least good (AUC: 70%–79%) to excellent (AUC >90%) distinction between clinically meaningful pain severity differentiations (no/mild–moderate–severe).

Conclusion

Cerebral Optical Spectrometry-based ROPA significantly correlated with subjectively reported pain in volunteers and laboring women, and could be a useful monitor for clinical circumstances where direct assessment is not available, or to complement patient-reported pain scores.

Habituation of phase-locked local field potentials and gamma-band oscillations recorded from the human insula

Salient nociceptive and non-nociceptive stimuli elicit low-frequency local field potentials (LFPs) in the human insula. Nociceptive stimuli also elicit insular gamma-band oscillations (GBOs), possibly preferential for thermonociception, which have been suggested to reflect the intensity of perceived pain. To shed light on the functional significance of these two responses, we investigated whether they would be modulated by stimulation intensity and temporal expectation - two factors contributing to stimulus saliency. Insular activity was recorded from 8 depth electrodes (41 contacts) implanted in the left insula of 6 patients investigated for epilepsy. Thermonociceptive, vibrotactile, and auditory stimuli were delivered using two intensities. To investigate the effects of temporal expectation, the stimuli were delivered in trains of three identical stimuli (S1-S2-S3) separated by a constant 1-s interval. Stimulation intensity affected intensity of perception, the magnitude of low-frequency LFPs, and the magnitude of nociceptive GBOs. Stimulus repetition did not affect perception. In contrast, both low-frequency LFPs and nociceptive GBOs showed a marked habituation of the responses to S2 and S3 as compared to S1 and, hence, a dissociation with intensity of perception. Most importantly, although insular nociceptive GBOs appear to be preferential for thermonociception, they cannot be considered as a correlate of perceived pain.

Physiological Signal Processing for Individualized Anti-nociception Management During General Anesthesia: a Review

OBJECTIVE

The aim of this paper is to review existing technologies for the nociception / anti-nociception balance evaluation during surgery under general anesthesia.

METHODS

General anesthesia combines the use of analgesic, hypnotic and muscle-relaxant drugs in order to obtain a correct level of patient non-responsiveness during surgery. During the last decade, great efforts have been deployed in order to find adequate ways to measure how anesthetic drugs affect a patient's response to surgical nociception. Nowadays, though some monitoring devices allow obtaining information about hypnosis and muscle relaxation, no gold standard exists for the nociception / anti-nociception balance evaluation. Articles from the PubMed literature search engine were reviewed. As this paper focused on surgery under general anesthesia, articles about nociception monitoring on conscious patients, in post-anesthesia care unit or in intensive care unit were not considered.

RESULTS

In this article, we present a review of existing technologies for the nociception / anti-nociception balance evaluation, which is based in all cases on the analysis of the autonomous nervous system activity. Presented systems, based on sensors and physiological signals processing algorithms, allow studying the patients' reaction regarding anesthesia and surgery.

CONCLUSION

Some technological solutions for nociception / antinociception balance monitoring were described. Though presented devices could constitute efficient solutions for individualized anti-nociception management during general anesthesia, this review of current literature emphasizes the fact that the choice to use one or the other mainly relies on the clinical context and the general purpose of the monitoring.

Prevention of anesthesia-induced injection pain of propofol in pediatric anesthesia

Objective:

Propofol is a new anesthetic agent in clinical practice, but randomized double-blinded prospective studies on its role in pediatric anesthesia remain limited. We aimed to compare the preventive effects of pre-injected lidocaine or ketamine and its pre-mixture on the anesthesia-induced injection pain of propofol using a randomized double-blinded prospective method, and to compare the outcomes with those of medium-/long-chain propofol (M/LCT).

Methods:

A total of 360 pediatric patients (aged 5-12 years old) who received elective surgery were randomly divided into six groups (n= 60) as follows. S group: control group; L group: lidocaine group; L + P group: lidocaine + propofol group; K group: ketamine group; K + P group: ketamine + propofol group; M group: M/LCT group. After the drug fluid completely entered the cubital vein, the venous access was closed. During propofol injection, the injection pain was scored using the VRS 4-point scale. Meanwhile, the heart rates before and during injection were recorded, the adverse reactions during and after injection were observed, and the incidence rate and degree of pain were evaluated.

Results:

The VRS 4-point scale showed that the incidence rates of injection pain of S group, L group, L + P group, K group, K + P group and M group were 78.3%, 66.67%, 51.66%, 43.33%, 48.33% and 45% respectively. The incidence rates of injection pain of all experimental groups were significantly lower than that of S group (P<0.01). The incidence rates of injection pain of L + P group, K group, K + P group and M group were significantly lower than that of L group (P<0.05). The differences among the other groups were not statistically significant.

Conclusions:

Intravenous pre-injection of lidocaine, ketamine or those mixed with propofol can all significantly reduce the incidence rate of injection pain of propofol.

Effects of transcutaneous electrical acupoint stimulation at different frequencies on perioperative anesthetic dosage, recovery, complications, and prognosis in video-assisted thoracic surgical lobectomy: a randomized, double-blinded, placebo-controlled trial

BACKGROUND

Transcutaneous electrical acupoint stimulation (TEAS), a non-invasive and non-pharmacological adjunctive intervention for perioperative analgesia, may also reduce the incidence of postoperative pulmonary complications. The effect of TEAS on video-assisted thoracic surgical (VATS) patients is still unknown, however. The purpose of this study was to investigate the effects of TEAS of different frequency on perioperative anesthetic dosage, recovery, complications, and prognosis for patients undergoing VATS lobectomy.

METHODS

Eighty VATS lobectomy patients with no previous experience of TEAS or acupuncture were randomly assigned to four groups: control (con), 2/100, 2, and 100 Hz. The last three experimental groups received TEAS at the indicated frequencies for 30 min before induction, during the operation, and for another 30 min 24 and 48 h after surgery. 2/100 Hz is a type of alternating frequency which goes between 2 and 100 Hz every 3 s. TEAS was administered over acupoints Neiguan, Hegu, Lieque, and Quchi on the sick lateral. Electrodes were applied to the patients in the control group, but no TEAS was used. Anesthetic dosage, blood gas analysis results, lung function indexes FEV₁ and FVC, post-anesthesia care unit (PACU) status, postoperative complications, and quality of life scores were recorded and analyzed statistically.

RESULTS

Intraoperative opioid consumption was lowest in the 2/100 Hz group, with statistical significance (con, P ≤ 0.001; 2 Hz, P ≤ 0.001; 100 Hz, P = 0.026). Compared with preoperative FEV₁ and FVC, postoperative FEV₁ and FVC were significantly lower in all groups; during one-lung ventilation, arterial oxygen partial pressure (PaO₂) decreased more slowly in the 2/100 Hz group than in the con group (P = 0.042). Moreover, in the 2/100 Hz group extubation time was shorter (P = 0.038), visual analgesia scale score lower (P = 0.047), and duration of PACU stay shorter (P = 0.043) than in the con group. In the 100 Hz group incidence of postoperative nausea and vomiting (PONV) was lower than the con group (P = 0.044). In all groups mean postoperative physical component scores were significantly lower than mean preoperative scores.

CONCLUSIONS

TEAS is a safe noninvasive adjunctive intervention for anesthesia management among patients undergoing VATS lobectomy. TEAS at 2/100 Hz can reduce intraoperative opioid dosage and slow the decrease of PaO₂ during one-lung ventilation. It can also effectively reduce pain score, extubation time, and PACU stay immediately after surgery. Further, 100 Hz TEAS can reduce PONV morbidity.

Assessing pain objectively: the use of physiological markers

Pain diagnosis and management would benefit from the development of objective markers of nociception and pain. Current research addressing this issue has focused on five main strategies, each with its own advantages and disadvantages. These encompass: (i) monitoring changes in the autonomic nervous system; (ii) biopotentials; (iii) neuroimaging; (iv) biological (bio-) markers; and (v) composite algorithms. Although each strategy has shown areas of promise, there are currently no validated objective markers of nociception or pain that can be recommended for clinical use. This article introduces the most important developments in the field and highlights shortcomings, with the aim of allowing the reader to make informed decisions about what trends to watch in the future.

Real-time cardiorespiratory coherence is blind to changes in respiration during general anesthesia

PURPOSE

A novel real-time cardiorespiratory coherence (CRC) algorithm has been developed to monitor nociception during general anesthesia. CRC uses custom designed filters to track and analyze the respiratory sinus arrhythmia (RSA) as it moves in time and frequency. CRC is a form of sensor fusion between heart rate and respiration, estimating the strength of linear coupling between the two signals. The aim of this study was to estimate the effect of changes in respiration rate (RR) and peak airway pressure (PPaw) on CRC. The response of CRC was compared to a prior offline wavelet-based algorithm (WTCRC) as well as traditional univariate heart rate variability (HRV) measures. A nociception index was created for each algorithm, ranging from 0 (no nociception) to 100 (strong nociception).

METHODS

Following ethics approval and informed consent, data were collected from 48 children receiving general anesthesia during dental surgery. The times of change in RR and PPaw events were noted in real-time. A total of 43 RR and 35 PPaw change events were analyzed post hoc in pseudo real-time. The nociception index averages were compared between a baseline period and a response period around each event. A Wilcoxon rank-sum test was used to compare changes.

RESULTS

The change in RR changed the CRC nociception index by an average of -2.2 [95% CI from -10 to 4.7] (P > 0.3), and the change in PPaw changed the CRC nociception index by an average of 5.4 [-1.0 to 11] (P > 0.1). The changes were smaller than those of many traditional HRV measures.

CONCLUSIONS

Real-time CRC was blind to the changes in respiration, and was less sensitive than many of the traditional HRV measures. A nociception index based on CRC can thus function across a wider range of respiratory conditions than can many traditional univariate HRV measures. The real-time CRC algorithm shows promise for monitoring nociception during general anesthesia.