The quantification and monitoring of intraoperative nociception levels in thoracic surgery: a review

Surgical pleth index monitoring in perioperative pain management: usefulness and limitations

Surgical pleth index (SPI) monitoring is a representative, objective nociception-monitoring device that measures nociception using photoplethysmographic signals. It is easy to apply to patients and the numerical calculation formula is intuitively easy to understand; therefore, its clinical interpretation is simple. Several studies have demonstrated its efficacy and utility. Compared with hemodynamic parameters, the SPI can detect the degree of nociception during surgery under general anesthesia with greater accuracy, and therefore can provide better guidance for the administration of various opioids, including remifentanil, fentanyl, and sufentanil. Indeed, SPI-guided analgesia is associated with lower intraoperative opioid consumption, faster patient recovery, and comparable or lower levels of postoperative pain and rates of adverse events compared with conventional analgesia. In addition, SPI monitoring allows for the degree of postoperative pain and analgesic requirements to be predicted through the SPI values immediately before patient arousal. However, because patient age, effective circulating volume, position, concomitant medication and anesthetic regimen and level of consciousness may be confounding factors in SPI monitoring, clinicians must be careful when interpreting SPI values. In addition, as SPI values can differ depending on anesthetic and analgesic regimens and the underlying disease, an awareness of the effects of these variables with an understanding of the advantages and disadvantages of SPI monitoring compared to other nociception monitoring devices is essential. Therefore, this review aimed to help clinicians perform optimal SPI-guided analgesia and to assist with the establishment of future research designs through clarifying current usefulness and limitations of SPI monitoring in perioperative pain management.

Machines, mathematics, and modules: the potential to provide real-time metrics for pain under anesthesia

The brain-based assessments under anesthesia have provided the ability to evaluate pain/nociception during surgery and the potential to prevent long-term evolution of chronic pain. Prior studies have shown that the functional near-infrared spectroscopy (fNIRS)-measured changes in cortical regions such as the primary somatosensory and the polar frontal cortices show consistent response to evoked and ongoing pain in awake, sedated, and anesthetized patients. We take this basic approach and integrate it into a potential framework that could provide real-time measures of pain/nociception during the peri-surgical period. This application could have significant implications for providing analgesia during surgery, a practice that currently lacks quantitative evidence to guide patient tailored pain management. Through a simple readout of "pain" or "no pain," the proposed system could diminish or eliminate levels of intraoperative, early post-operative, and potentially, the transition to chronic post-surgical pain. The system, when validated, could also be applied to measures of analgesic efficacy in the clinic.

The association of hemodynamic parameters and clinical demographic variables with acute postoperative pain in female oncological breast surgery patients: A retrospective cohort study

OBJECTIVES

Appropriate administration of intraoperative analgesia is an essential factor in care and reasonable recovery times. Inappropriate intraoperative analgesia puts the patient at risk of acute postoperative pain (APOP). The absence of an objective standard for intraoperative nociceptive monitoring complicates pain care. Heart rate (HR) and mean arterial blood pressure (MABP) have been suggested as useful parameters during general anesthesia for nociceptive monitoring. However, studies focusing on whether intraoperative heart rate variability (HRv) and mean arterial blood pressure variability (MABPv) during general anesthesia can accurately monitor nociception in patients have remained inconclusive. The current study aimed to (1) identify the association of intraoperative heart rate and blood pressure variability in patients undergoing low-risk surgery with the incidence of APOP in the immediate postoperative setting and (2) evaluate the associations of clinical demographic factors with the incidence of APOP.

METHODS

A retrospective observational cohort study was conducted. The outcome was moderate-to-severe APOP, defined as a numeric rating scale score of ≥ 4. HRv, MABPv, and potential confounders, such as age, body mass index, duration of surgery, smoking, depression, preoperative use of analgesics, and type of surgery, were used as independent variables.

RESULTS

Data from 764 female oncological breast surgery patients were analyzed. No statistically significant association of HRv and MABPv with APOP was found. Lower age was associated with higher odds of APOP (odds ratio [OR] 0.978, p = 0.001). Increased length of surgery (OR 1.013, p = 0.022) and a history of depression were associated with increased odds of APOP (OR 2.327, p = 0.010). The subtype of surgery was statistically significantly associated with APOP (p = 0.006).

CONCLUSIONS

Our results suggest that heart rate and blood pressure variability intraoperatively, in female patients undergoing low-risk surgery, are not associated with, and thus not predictive of, APOP in the immediate postoperative setting.

Feasibility of the pupillary pain index as a guide for depth of analgesia during opioid-sparing anesthesia with continuous infusion of dexmedetomidine

BACKGROUND

The pupillary dilation reflex (PDR) is an objective indicator of analgesic levels in anesthetized patients. Through measurement of the PDR during increasing tetanic stimulation (10-60 mA), it is possible to obtain the pupillary pain index (PPI), a score that assesses the level of analgesia.

OBJECTIVES

The depth of analgesia during opioid-sparing anesthesia (OSA) with continuous infusion of dexmedetomidine in addition to general anesthesia was assessed.

DESIGN

Observational prospective feasibility pilot study SETTING: This study was performed in the operating rooms of the Spedali Civili University-affiliated hospital of Brescia, Italy.

PATIENTS

Forty-five adults who underwent elective open (5-cm incision) surgery under general anesthesia (78% inhalation anesthesia), from Feb. 18th to Aug. 1st, 2019, were enrolled. Exclusion criteria were as follows: implanted pacemaker or ICD, ophthalmological comorbidities, chronic opioid use, peripheral neuropathy, other adjuvant drugs, epidural analgesia, or locoregional block.

MAIN OUTCOME MEASURES

The first aim was to verify the feasibility of applying a study protocol to evaluate the depth of analgesia during intraoperative dexmedetomidine administration using an instrumental pupillary evaluation. The secondary outcome was to evaluate appropriate analgesia, drug dosage, anesthesia depth, heart rate, blood pressure, transient side effects, postoperative nausea and vomiting (PONV), and pain numerical rating scale (NRS) score.

RESULTS

Thirty out of 50 patients (60%) treated with dexmedetomidine during the study period were included in the DEX group (8 males, age 42 ± 13 years, BMI 45 ± 8), and 15 other patients were included in the N-DEX group (8 males, age 62 ± 13 years, BMI 26 ± 6). Patients who underwent bariatric, abdominal, or plastic surgery were enrolled. At least 3 pupillary evaluations were taken for each patient. PPI ≤ 3 was observed in 97% of patients in the DEX group and 53% in the N-DEX group. Additionally, the DEX group received less than half the remifentanil dose than the N-DEX group (0.13 ± 0.07 vs 0.3 ± 0.11 mcg kg-1 min-1). The average dose of dexmedetomidine administered was 0.17 ± 0.08 mcg kg-1 h-1.

CONCLUSION

The feasibility of applying the protocol was verified. An OSA strategy involving dexmedetomidine may be associated with improved analgesic stability: a randomized controlled trial is necessary to verify this hypothesis.

TRIAL REGISTRATION

Trial.gov registration number: NCT05785273.

Nociception Control of Bilateral Single-Shot Erector Spinae Plane Block Compared to No Block in Open Heart Surgery-A Post Hoc Analysis of the NESP Randomized Controlled Clinical Trial

Background and Objectives: The erector spinae plane block (ESPB) is an analgesic adjunct demonstrated to reduce intraoperative opioid consumption within a Nociception Level (NOL) index-directed anesthetic protocol. We aimed to examine the ESPB effect on the quality of intraoperative nociception control evaluated with the NOL index. Materials and Methods: This is a post hoc analysis of the NESP (Nociception Level Index-Directed Erector Spinae Plane Block in Open Heart Surgery) randomized controlled trial. Eighty-five adult patients undergoing on-pump cardiac surgery were allocated to group 1 (Control, n = 43) and group 2 (ESPB, n = 42). Both groups received general anesthesia. Preoperatively, group 2 received bilateral single-shot ESPB (1.5 mg/kg/side 0.5% ropivacaine mixed with dexamethasone 8 mg/20 mL). Until cardiopulmonary bypass (CPB) was initiated, fentanyl administration was individualized using the NOL index. The NOL index was compared at five time points: pre-incision (T1), post-incision (T2), pre-sternotomy (T3), post-sternotomy (T4), and pre-CPB (T5). On a scale from 0 (no nociception) to 100 (extreme nociception), a NOL index > 25 was considered an inadequate response to noxious stimuli. Results: The average NOL index across the five time points in group 2 to group 1 was 12.78 ± 0.8 vs. 24.18 ± 0.79 (p < 0.001). The NOL index was significantly lower in the ESPB-to-Control group at T2 (12.95 ± 1.49 vs. 35.97 ± 1.47), T3 (13.28 ± 1.49 vs. 24.44 ± 1.47), and T4 (15.52 ± 1.49 vs. 34.39 ± 1.47) (p < 0.001) but not at T1 and T5. Compared to controls, significantly fewer ESPB patients reached a NOL index > 25 at T2 (4.7% vs. 79%), T3 (0% vs. 37.2%), and T4 (7.1% vs. 79%) (p < 0.001). Conclusions: The addition of bilateral single-shot ESPB to general anesthesia during cardiac surgery improved the quality of intraoperative nociception control according to a NOL index-based evaluation.

Evaluation of Nociception during Pediatric Surgery: A Topical Review

The association between intraoperative nociception and increased patient's morbidity is well established. However, hemodynamic parameters, such as heart rate and blood pressure, may result in an inadequate monitor of nociception during surgery. Over the last two decades, different devices have been marketed to "reliably" detect intraoperative nociception. Since the direct measure of nociception is impractical during surgery, these monitors measures nociception surrogates such as sympathetic and parasympathetic nervous systems responses (heart rate variability, pupillometry, skin conductance), electroencephalographic changes, and muscular reflex arc. Each monitor carries its own advantages and disadvantages. The manuscript aims to give an overview of the most up-to-date information available in the literature on current nociceptor monitors available in clinical practice, with particular focus on their applications in pediatrics.

Intraoperative Assessment of Surgical Stress Response Using Nociception Monitor under General Anesthesia and Postoperative Complications: A Narrative Review

We present a narrative review focusing on the new role of nociception monitor in intraoperative anesthetic management. Higher invasiveness of surgery elicits a higher degree of surgical stress responses including neuroendocrine-metabolic and inflammatory-immune responses, which are associated with the occurrence of major postoperative complications. Conversely, anesthetic management mitigates these responses. Furthermore, improper attenuation of nociceptive input and related autonomic effects may induce increased stress response that may adversely influence outcome even in minimally invasive surgeries. The original role of nociception monitor, which is to assess a balance between nociception caused by surgical trauma and anti-nociception due to anesthesia, may allow an assessment of surgical stress response. The goal of this review is to inform healthcare professionals providing anesthetic management that nociception monitors may provide intraoperative data associated with surgical stress responses, and to inspire new research into the effects of nociception monitor-guided anesthesia on postoperative complications.

Association between averaged intraoperative nociceptive response index and postoperative complications after lung resection surgery

OBJECTIVES

Since postoperative complications, defined as Clavien-Dindo grade ≥II, correlate with long-term survival after lung resection surgery in patients with primary lung cancer, identification of intraoperative risk factors for postoperative complications is crucial for better perioperative management. In the present study, we investigated the possible association between intraoperative variables for use in anaesthetic management and Clavien-Dindo grade ≥II.

METHODS

In this multi-institutional observational study, consecutive adult patients undergoing video-assisted thoracic surgery for primary lung cancer under general anaesthesia from March 2019 to April 2021 were enrolled. All patients were divided into 2 groups with Clavien-Dindo grade <II and ≥II. Uni- and multivariable analyses were performed to identify intraoperative risk factors.

RESULTS

After univariable analysis between patients with Clavien-Dindo grade <II (n = 415) and ≥II (n = 121), multivariable analysis revealed higher averaged nociceptive response (NR) index during surgery (mean NR), male sex, lower body mass index, longer duration of surgery, higher blood loss and lower urine volume, as independent risk factors for postoperative complications. In sensitivity analysis, based on the cut-off value of mean NR for postoperative complications, all patients were divided into high and low mean NR groups. The incidence of postoperative complications was significantly higher in patients with high mean NR (n = 332) than in patients with low mean NR (n = 204; P < 0.001).

CONCLUSIONS

Higher mean NR, as intraoperative variables for use in anaesthetic management, is associated with the higher incidence of postoperative complications after primary lung cancer surgery.

Retrospective assessment of the relationship between intraoperative nociception and postoperative analgesia requirements in dogs undergoing thoracic surgery

BACKGROUND

The analgesia management of thoracic surgery can be challenging and debate exists regarding the efficacy of pre-emptive analgesia and its relationship with postoperative pain. The aim of this study was to assess the relationship between intraoperative nociception and postoperative pain in dogs undergoing thoracic surgery. If proven, effective prevention of intraoperative nociception could imply prospective lower postoperative analgesia requirements.

METHODS

The study was retrospective and observational. Clinical records from dogs undergoing thoracic surgery (2015-2019) were reviewed and cases were allocated to one of two groups: NOCI-FREE - dogs with no evidence of intraoperative nociception; NOCI - dogs that required intraoperative rescue analgesia to address a nociceptive response. Pre-anaesthetic medication, locoregional analgesia, intraoperative infusions and rescue analgesia were used. Additionally, postoperative pain scores and analgesia plans were registered and compared between groups.

RESULTS

Our study failed to identify a difference in the postoperative pain scores and analgesia requirements between dogs having signs of intraoperative nociception and those without. Additionally, the use of postoperative analgesic preventive infusions and rescue analgesia was similar for both NOCI and NOCI-FREE. Being on an intraoperative infusion of opioids, dexmedetomidine or lidocaine was identified as a protective factor for nociception [OR = 11; (4.15-29.7)].

CONCLUSIONS

In the population studied, it appears that dogs showing signs of nociception intraoperatively do not necessarily show higher pain scores nor do they need additionally pain relief in the postoperative period.

Preemptive analgesic efficacy of ultrasound-guided transversalis fascia plane block in children undergoing inguinal herniorrhaphy: a randomized, double-blind, controlled study

Background

Surgical repair of congenital inguinal hernia results in significant postoperative discomfort and pain. The aim of the current study was to evaluate the pre-emptive analgesic efficacy of a transversalis fascia plane (TFP) block after pediatric inguinal herniorrhaphy.

Methods

Forty-four patients aged 12 to 60 months who underwent unilateral inguinal herniorrhaphy were enrolled. Four patients were excluded, and the remaining were allocated to the control group and the TFP block group. In the TFP block group, 0.4 ml/kg bupivacaine 0.25% was instilled in the plane between the transversus abdominis and transversalis fascia, while in the control group 0.9% saline was used instead of bupivacaine. The collected data were the total dose of paracetamol consumed during the first 12 h postoperatively, the postoperative Face, Leg, Activity, Cry, Consolability (FLACC) pain score, time to first use of rescue analgesia, number of patients required additional postoperative analgesics, and parents' satisfaction.

Results

The median paracetamol consumption was significantly lower in the TFP block group than in the control group, and FLACC pain scores were significantly lower for all study times in the TFP block group with higher parental satisfaction scores than those for the control group. The number of patients who required additional analgesics was significantly lower in the TFP block group than in the control group.

Conclusions

The use of a TFP block decreases postoperative analgesic consumption and postoperative pain intensity after pediatric inguinal herniorrhaphy. Future studies with larger sample size are required to evaluate the actual complications rate of TFP block.

Malewicz N, Ebel M, K. Zahn P, H. Meyer-Frießem C. Pupillometric Monitoring of Nociception in Cardiac Anesthesia

BACKGROUND

High-dose opioids are conventionally used for cardiac anesthesia, but without monitoring of nociception. In non-cardiac surgical procedures the intra - operative dose of opioids can be individualized and reduced with pupillometric monitoring of the pupillary pain index (PPI; scale 1-9). A randomized controlled trial was carried out to explore whether pupillometry can be used for nociception monitoring in cardiac anesthesia and whether it leads to opioid reduction.

METHODS

A sample of 57 cardiac surgery patients receiving continuously administered sufentanil (initial dosage 0.7 μg*kg-¹*h-¹) was divided into a PPI group (sufentanil reduction if PPI<3 up to a minimum of 0.15 μg*kg-¹*h-¹, n=32) and a control group (standard anesthesia; n = 25). The primary outcome was the time from the end of anesthesia to extubation. The secondary outcomes were total intraoperative dose of sufentanil/noradrenaline, postoperative pain intensity (numeric rating scale [NRS] 0-10) and intraoperative awareness. German Clinical Trials Registry no. DRKS 00012329.

RESULTS

The primary outcome, extubation time, did not differ between the two groups (1.14 h, 95% confidence interval [-0.99; 3.27], p = 0.592). Compared with the control patients (68% male, age 70 ± 10.4 years, PPI 1.1 ± 0.2), the mean sufentanil infusion rate in the PPI patients (81% male, age 68 ± 10.3 years, PPI 1.1 ± 0.2) decreased by 81.8% (-0.68 μg*kg-¹*h-¹ [-0,7; -0.67], p<0.001) to the predetermined minimum level, without intraoperative awareness. Moreover, the noradrenaline dose was reduced by 56% (1235.51 μg [321.91; 2149.12], p = 0.005) and the postoperative pain intensity by 45% (2.11 NRS [0.93; 3.3] after 24 h, p = 0.003).

CONCLUSION

Pupillometry is appropriate for nociception monitoring in cardiac anesthesia. Thereby a considerable reduction of intraoperative opioids as well as increased intraoperative hemodynamic stability was achieved and postoperative opioid-induced hyperalgesia was prevented. The consistently low PPI scores, indicating adequate analgesia, suggest that further reduction of opioid doses is feasible.