Analgesia Nociception Index-guided intraoperative fentanyl consumption and postoperative analgesia in patients receiving scalp block versus incision-site infiltration for craniotomy

Cost-effectiveness and efficacy of scalp block for elective supratentorial craniotomy in resource-limited settings: A randomized controlled trial

Background

Remifentanil is favored for neurosurgical pain management, but its utilization in low- and middle-income countries (LMICs) is limited. Scalp block techniques are effective in LMICs, but cost-effectiveness is uncertain. This study compares costs and perioperative outcomes of scalp block versus fentanyl infusion in patients undergoing elective supratentorial craniotomy.

Methods

A prospective double-blind randomized controlled trial was conducted with 36 patients aged 18- 65 years undergoing elective supratentorial craniotomy. Patients were randomly assigned to receive either scalp block with 0.5% bupivacaine (Group S) or fentanyl infusion (Group F), with normal saline placebo administered in both groups. The primary endpoint was the anesthetic costs, with secondary endpoints including perioperative opioid consumption, intraoperative hemodynamic changes, and perioperative complications.

Results

The cost of fentanyl was significantly lower than that of local anesthetics (3.31 [3.31, 3.75] vs. 4.27 [4.27, 4.27] United States dollars, P < 0.001). However, the overall anesthetic cost did not differ significantly between groups. Group F demonstrated a significant reduction in mean arterial pressure immediately and 5 min after pin insertion compared to Group S (75.8 [13.9] vs. 92.5 [16.9] mmHg, P = 0.003 and 67.7 [6.4] vs. 78.5 [10.7] mmHg, P < 0.001, respectively).

Conclusion

Fentanyl infusion presents cost advantages over scalp block in LMIC settings. However, prudent opioid use is imperative. This study underscores the need for ongoing research to optimize neurosurgical pain management and evaluate long-term safety implications.

Analgesia-nociception index accurately predicts inadequate pectoralis muscle fascia block (PECS) in patients undergoing breast surgery: A prospective observational study

BACKGROUND

Postoperative opioid administration has been largely replaced by regional anesthesia techniques. We aimed to determine whether intraoperative Analgesia-Nociception Index (ANI) can aid in early evaluation of the effectiveness of regional blocks such as the pectoralis muscle fascia block (PECS, pectoserratus and interpectoral plane blocks) and predicting the need for analgesics postoperatively.

METHODS

This prospective observational study enrolled 30 women (age: 20-80 years) undergoing unilateral, non-intubated, breast tumor excision alone or in conjunction with sentinel lymph node biopsy. PECS block was performed following sedation. ANI readings were obtained at 1-min intervals, and polar coordinates were assigned to the distance from the nipple (0.5-cm intervals) and o'clock position (15-min intervals) for each reading. Pain scores were assessed using a numeric rating scale from 0 to 10, and analgesics were administered depending on pain score post-operatively.

RESULTS

8 (27%), 19 (63%), and 3 (10%) patients received morphine, tramadol, and no analgesics, respectively. In total, 954 ANI measurements were obtained. At the proposed cut-off of 50, the sensitivity and specificity of the ANI nadir for need of post-operative opioids were 0.875 and 0.932, respectively. Block effectiveness was most satisfactory in the upper lateral quadrant of the breast with nipple-areolar complex (NAC) sparing effect. Most average ANI measurements for the NAC were <50. No patient experienced postoperative nausea/vomiting, although one reported dizziness.

CONCLUSIONS

The intraoperative ANI nadir <50 was strongly correlated with need for postoperative opioids. The ANI may aid in objectively evaluating the effectiveness of pectoralis muscle fascial blocks and predicting postoperative need for analgesics.

Pain Assessment Using the Analgesia Nociception Index (ANI) in Patients Undergoing General Anesthesia: A Systematic Review and Meta-Analysis

The analgesia nociception index (ANI) has emerged as a potential measurement for objective pain assessment during general anesthesia. This systematic review and meta-analysis aimed to evaluate the accuracy and effectiveness of ANI in assessing intra- and post-operative pain in patients undergoing general anesthesia. We conducted a comprehensive search of Ovid-MEDLINE, Ovid-EMBASE, Cochrane Central Register of Controlled Trials, Google Scholar, public clinical trial databases (ClinicalTrials and Clinical Research Information Service), and OpenSIGLE to identify relevant studies published prior to May 2023 and included studies that evaluated the accuracy and effectiveness of ANI for intra- or post-operative pain assessment during general anesthesia. Among the 962 studies identified, 30 met the eligibility criteria and were included in the systematic review, and 17 were included in the meta-analysis. For predicting intra-operative pain, pooled sensitivity, specificity, diagnostic odds ratio (DOR), and area under curve of ANI were 0.81 (95% confidence interval [CI] = 0.79-0.83; I2 = 68.2%), 0.93 (95% CI = 0.92-0.93; I2 = 99.8%), 2.32 (95% CI = 1.33-3.30; I2 = 61.7%), and 0.77 (95% CI = 0.76-0.78; I2 = 87.4%), respectively. ANI values and changes in intra-operative hemodynamic variables showed statistically significant correlations. For predicting post-operative pain, pooled sensitivity, specificity, and DOR of ANI were 0.90 (95% CI = 0.87-0.93; I2 = 58.7%), 0.51 (95% CI = 0.49-0.52; I2 = 99.9%), and 3.38 (95% CI = 2.87-3.88; I2 = 81.2%), respectively. ANI monitoring in patients undergoing surgery under general anesthesia is a valuable measurement for predicting intra- and post-operative pain. It reduces the use of intra-operative opioids and aids in pain management throughout the perioperative period.

Incidence, predictors, and impact of acute post-operative pain after cranial neurosurgery: A prospective cohort study

Objectives

Pain is common after craniotomy. Its incidence and predictors in developing nations are not adequately studied. We aimed to assess the incidence, predictors, and impact of acute post-operative pain after intracranial neurosurgeries.

Materials and Methods

This prospective observational study was conducted in adult patients undergoing intracranial neurosurgeries. After patient consent, ethics committee approval, and study registration, we assessed the incidence of post-operative pain using numerical rating scale (NRS) score. Predictors and impact of pain on patient outcomes were also evaluated.

Results

A total of 497 patients were recruited during 10-month study period. Significant (4-10 NRS score) post-operative pain at any time-point during the first 3 days after intracranial neurosurgery was reported by 65.5% (307/469) of patients. Incidence of significant pain during the 1st post-operative h, on the 1st, 2nd, and 3rd post-operative days was 20% (78/391), 50% (209/418), 38% (152/401), and 24% (86/360), respectively. Higher pre-operative NRS score and pain during the 1st h post-operatively, predicted the occurrence of pain during the first 3 days after surgery, P = 0.003 and P < 0.001, respectively. Pain was significantly associated with poor sleep quality on the first 2 post-operative nights (P < 0.001). Patient satisfaction score was higher in patients with post-operative pain, P = 0.002.

Conclusion

Every two in three patients undergoing elective intracranial neurosurgery report significant pain at some point during the first 3 postoperative days. Pre-operative pain and pain during 1st post-operative h predict the occurrence of significant post-operative pain.

Analgesia nociception index and high frequency variability index: promising indicators of relative parasympathetic tone

At present, there is no objective and absolute measure of nociception, although various monitoring techniques have been developed. One such technique is the Analgesia Nociception Index (ANI), which is calculated from heart rate variability that reflects the relative parasympathetic tone. ANI is expressed on a non-unit scale of 0-100 (100 indicates maximal relative parasympathetic tone). Several studies indicated that ANI-guided anesthesia may help reduce intraoperative opioid use. The usefulness of ANI in the intensive care unit (ICU) and during surgery has also been reported. However, some limitations of ANI have also been reported; for example, ANI is affected by emotions and some drugs. In 2022, a high frequency variability index (HFVI), which was renamed from ANI and uses the same algorithm as ANI, was commercialized; therefore, ANI/HFVI are currently in the spotlight. Unlike ANI, HFVI can be displayed along with other biometric information on the Root® monitor. ANI/HFVI monitoring may affect the prognosis of not only patients in the perioperative period but those in ICU, those who receive home medical care, or outpatients. In this article, we present an updated review on ANI that has been published in the last decade, introduce HFVI, and discuss the outlooks of ANI/HFVI.

Comparison between Analgesia Nociception Index (ANI) and self-reported measures for diagnosing pain in conscious individuals: a systematic review and meta-analysis

The Analgesia Nociception Index (ANI), an objective measure of pain based on heart rate variability (HRV), has its usefulness in awake patients still unclear. This systematic review and meta-analysis aimed to assess ANI's accuracy compared to self-reported pain measures in conscious individuals undergoing medical procedures or painful stimuli. PubMed, Ovid, Web of Science, Scopus, Embase, and grey literature were searched until March 2021. Of the 832 identified citations, 16 studies complied with the eligibility criteria. A meta-analysis including nine studies demonstrated a weak negative correlation between ANI and NRS for pain assessment in individuals in the post-anesthetic recovery room (r = − 0.0984, 95% CI = − 0.397 to 0.220, I² = 95.82%), or in those submitted to electrical stimulus (r = − 0.089; 95% CI = − 0.390 to 0.228, I² = 0%). The evidence to use ANI in conscious individuals is weak compared to self-report measures of pain, yet ANI explains a part of self-report. Therefore, some individuals may be benefited from the use of ANI during procedures or in the immediate postoperative period.

An Update of Neuroanesthesia for Intraoperative Brain Mapping Craniotomy

The perioperative multidisciplinary team approach has probably been best exemplified by the care of awake craniotomy patients. Advancement in anesthesia and meticulous perioperative care has supported the safety and complexity of the surgical and mapping efforts in glioma resection. The discussions in this review will emphasize on anesthetic and perioperative management strategies to prevent complications and minimize their effects if they occur, including current practice guidelines in anesthesia, updates on the applications of anesthetic medications, and emerging devices. Planning the anesthetic and perioperative management is based on understanding the pharmacology of the medications, the goals of different stages of the surgery and mapping, and anticipating potential problems.

Updates on Wound Infiltration Use for Postoperative Pain Management: A Narrative Review

Local anesthetic wound infiltration (WI) provides anesthesia for minor surgical procedures and improves postoperative analgesia as part of multimodal analgesia after general or regional anesthesia. Although pre-incisional block is preferable, in practice WI is usually done at the end of surgery. WI performed as a continuous modality reduces analgesics, prolongs the duration of analgesia, and enhances the patient’s mobilization in some cases. WI benefits are documented in open abdominal surgeries (Caesarean section, colorectal surgery, abdominal hysterectomy, herniorrhaphy), laparoscopic cholecystectomy, oncological breast surgeries, laminectomy, hallux valgus surgery, and radical prostatectomy. Surgical site infiltration requires knowledge of anatomy and the pain origin for a procedure, systematic extensive infiltration of local anesthetic in various tissue planes under direct visualization before wound closure or subcutaneously along the incision. Because the incidence of local anesthetic systemic toxicity is 11% after subcutaneous WI, appropriate local anesthetic dosing is crucial. The risk of wound infection is related to the infection incidence after each particular surgery. For WI to fully meet patient and physician expectations, mastery of the technique, patient education, appropriate local anesthetic dosing and management of the surgical wound with “aseptic, non-touch” technique are needed.

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.

Virtual reality vs. Kalinox® for management of pain in intensive care unit after cardiac surgery: a randomized study

Introduction

The management of pain and anxiety remains a challenge in the intensive care unit. By distracting patients, virtual reality (VR) may have a role in painful procedures. We compared VR vs. an inhaled equimolar mixture of N₂O and O₂ (Kalinox®) for pain and anxiety management during the removal of chest drains after cardiac surgery.

Methods

Prospective, non-inferiority, open-label study. Patients were randomized, for Kalinox® or VR session during drain removal. The analgesia/nociception index (ANI) was monitored during the procedure for objective assessment of pain and anxiety. The primary endpoint was the ΔANI (ANI_min − ANI₀) during the procedure, based on ANIm (average on 4 min). We prespecified VR as non-inferior to Kalinox® with a margin of 3 points. Self-reported pain and anxiety were also analysed using numeric rate scale (NRS).

Results

200 patients were included, 99 in the VR group and 101 in the Kalinox® group; 90 patients were analysed in both groups in per-protocol analysis. The median age was 68.0 years [60.0–74.8]. The ΔANI was − 15.1 ± 12.9 in the Kalinox® group and − 15.7 ± 11.6 in the VR group (NS). The mean difference was, therefore, − 0.6 [− 3.6 to 2.4], including the non-inferiority margin of 3. Patients in the VR group had a significantly higher pain NRS scale immediately after the drain removal, 5.0 [3.0–7.0] vs. 3.0 [2.0–6.0], p = 0.009, but no difference 10 min after. NRS of anxiety did not differ between the two groups.

Conclusion

Based on the ANI, the current study showed that VR did not reach the statistical requirements for a proven non-inferiority vs. Kalinox® in managing pain and anxiety during chest drain removal. Moreover, VR was less effective based on NRS. More studies are needed to determine if VR might have a place in the overall approach to pain and anxiety in intensive care units.

Trial registration NCT, NCT03956264. Registered 20 May 2019, https://clinicaltrials.gov/ct2/show/NCT03956264

Multiparametric Monitoring of Hypnosis and Nociception-Antinociception Balance during General Anesthesia-A New Era in Patient Safety Standards and Healthcare Management

The development of general anesthesia techniques and anesthetic substances has opened new horizons for the expansion and improvement of surgical techniques. Nevertheless, more complex surgical procedures have brought a higher complexity and longer duration for general anesthesia, which has led to a series of adverse events such as hemodynamic instability, under- or overdosage of anesthetic drugs, and an increased number of post-anesthetic events. In order to adapt the anesthesia according to the particularities of each patient, the multimodal monitoring of these patients is highly recommended. Classically, general anesthesia monitoring consists of the analysis of vital functions and gas exchange. Multimodal monitoring refers to the concomitant monitoring of the degree of hypnosis and the nociceptive-antinociceptive balance. By titrating anesthetic drugs according to these parameters, clinical benefits can be obtained, such as hemodynamic stabilization, the reduction of awakening times, and the reduction of postoperative complications. Another important aspect is the impact on the status of inflammation and the redox balance. By minimizing inflammatory and oxidative impact, a faster recovery can be achieved that increases patient safety. The purpose of this literature review is to present the most modern multimodal monitoring techniques to discuss the particularities of each technique.

Pharmacological interventions for the prevention of acute postoperative pain in adults following brain surgery

BACKGROUND

Pain following brain surgery can compromise recovery. Several pharmacological interventions have been used to prevent pain after craniotomy; however, there is currently a lack of evidence regarding which interventions are most effective.

OBJECTIVES

The objectives are to assess the effectiveness of pharmacological interventions for prevention of acute postoperative pain in adults undergoing brain surgery; compare them in terms of additional analgesic requirements, incidence of chronic headache, sedative effects, length of hospital stay and adverse events; and determine whether these characteristics are different for certain subgroups.

SEARCH METHODS

We searched MEDLINE, Embase, CINAHL, CENTRAL, Web of Science and two trial registries together with reference checking and citation searching on 28th of November 2018.

SELECTION CRITERIA

We included blinded and non-blinded, randomized controlled trials evaluating pharmacological interventions for the prevention of acute postoperative pain in adults undergoing neurosurgery, which had at least one validated pain score outcome measure.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. We calculated mean differences for the primary outcome of pain intensity; any pain scores reported on a 0 to 100 scale were converted to a 0 to 10 scale.

MAIN RESULTS

We included 42 completed studies (3548 participants) and identified one ongoing study. Nonsteroidal anti-inflammatories (NSAIDs) Nonsteroidal anti-inflammatories (NSAIDs) reduce pain up to 24 hours (0 to 6 hours, MD -1.16, 95% CI -1.57 to -0.76; 12 hours, MD -0.62, 95% CI -1.11 to -0.14; 24 hours, MD -0.66, 95% CI -1.18 to -0.13; 6 studies, 742 participants; all high-quality evidence). Results for other outcomes were imprecise (additional analgesic requirements: MD 1.29 mg, 95% CI -5.0 to 2.46, 4 studies, 265 participants; nausea and vomiting RR 1.34, 95% CI 0.30 to 5.94, 2 studies, 345 participants; both low-quality evidence). Dexmedetomidine reduces pain up to 12 hours (0 to 6 hours, MD -0.89, 95% CI -1.27 to -0.51, moderate-quality evidence; 12 hours, MD -0.81, 95% CI -1.21 to -0.42, low-quality evidence). It did not show efficacy at 24 hours (MD -0.08, 95% CI -0.32 to 0.16; 2 studies, 128 participants; low-quality evidence). Dexmedetomidine may decrease additional analgesic requirements (MD -21.36 mg, 95% CI -34.63 to -8.1 mg, 2 studies, 128 participants, low-quality evidence). Results for other outcomes were imprecise (nausea and vomiting RR -0.43, 95% CI 0.06 to 3.08, 3 studies, 261 participants; hypotension RR 0.5, 95% CI 0.05 to 5.28, 3 studies, 184 participants; both low-quality evidence). Scalp blocks may reduce pain up to 48 hours (0 to 6 hours, MD -0.98, 95% CI -1.66 to -0.3, 10 studies, 414 participants; 12 hours, MD -0.95, 95% CI -1.53 to -0.37, 8 studies, 294 participants; 24 hours, MD -0.78, 95% CI -1.52 to -0.05, 9 studies, 433 participants, all low-quality evidence; 48 hours, MD -1.34, 95% CI -2.57 to -0.11, 4 studies, 135 participants, very low-quality evidence. When studies with high risk of bias were excluded, significance remained at 12 hours only. Scalp blocks may decrease additional analgesia requirements (SMD -1.11, 95% CI -1.97 to -0.25, 7 studies, 314 participants). Results for other outcomes were imprecise (nausea and vomiting RR 0.66, 95% CI 0.33 to 1.32, 4 studies, 165 participants, very low-quality evidence). Scalp Infiltration may reduce pain postoperatively but efficacy was inconsistent, with a significant effect at 12 and 48 hours only (12 hours, MD -0.71, 95% CI -1.34 to -0.08, 7 studies, 309 participants, low-quality evidence; 48 hours, MD - 1.09, 95% CI -2.13 to - 0.06, 3 studies, 128 participants, moderate-quality evidence). No benefit was observed at other times (0 to 6 hours, MD -0.64, 95% CI -1.28 to -0.00, 9 studies, 475 participants, moderate-quality evidence; 24 hours, MD -0.39, 95% CI -1.06 to 0.27,6 studies, 260 participants, low-quality evidence. Scalp infiltration may reduce additional analgesia requirements MD -9.56 mg, 95% CI -15.64 to -3.49, 6 studies, 345 participants, very low-quality evidence). When studies with high risk of bias were excluded, scalp infiltration lost the pain benefit at 12 hours and effects on additional analgesia requirements, but retained the pain-reducing benefit at 48 hours (MD -0.56, 95% CI -1.20 to -0.32, 2 studies, 100 participants, very low-quality evidence). Results for other outcomes were imprecise (nausea and vomiting, RR 0.74, 95% CI 0.48 to 1.41, 4 studies, 318 participants, low-quality evidence). Pregabalin or gabapentin may reduce pain up to 6 hours (2 studies, 202 participants), MD -1.15,95% CI -1.66 to -0.6, 2 studies, 202 participants, low-quality evidence). One study examined analgesic efficacy at 12 hours showing significant benefit. No analgesia efficacy was shown at later times (24 hours, MD -0.29, 95% CI -0.78 to -0.19; 48 hours, MD - 0.06, 95% CI -0.86 to 0.77, 2 studies, 202 participants, low-quality evidence). Additional analgesia requirements were not significantly less (MD -0.37 (95% CI -1.10 to 0.35, 3 studies, 234 participants, low-quality evidence). Risk of nausea and vomiting was significantly reduced (RR 0.51, 95% CI 0.29 to 0.89, 3 studies, 273 participants, low-quality evidence). Results for other outcomes were imprecise (additional analgesia requirements: MD -0.37, 95% CI -1.10 to 0.35, 3 studies, 234 participants, low-quality evidence). Acetaminophen did not show analgesic benefit (0 to 6 hours, MD -0.35, 95% CI -1.00 to 0.30; 12 hours, MD -0.51, 95% CI -1.04 to 0.03, 3 studies, 332 participants, moderate-quality evidence; 24 hours, MD -0.34, 95% CI -1.20 to 0.52, 4 studies, 439 participants, high-quality evidence). Results for other outcomes remained imprecise (additional analgesia requirements, MD 0.07, 95% CI -0.86 to 0.99, 4 studies, 459 participants, high-quality evidence; length of hospitalizations, MD -3.71, 95% CI -14.12 to 6.7, 2 studies, 335 participants, moderate-quality evidence).

AUTHORS' CONCLUSIONS

There is high-quality evidence that NSAIDs reduce pain up to 24 hours postoperatively. The evidence for reductions in pain with dexmedetomidine, pregabalin or gabapentin, scalp blocks, and scalp infiltration is less certain and of very low to moderate quality. There is low-quality evidence that scalp blocks and dexmedetomidine may reduce additional analgesics requirements. There is low-quality evidence that gabapentin or pregabalin may decrease nausea and vomiting, with the caveat that the total number of events for this comparison was low.

Evaluation of Surgical Pleth Index and Analgesia Nociception Index as surrogate pain measures in conscious postoperative patients: an observational study

We evaluated the performance of the Surgical Plethysmographic Index (SPI) and the Analgesia Nociception Index (ANI) as surrogate pain measures and determined their respective cut-off values for detecting pain in conscious postoperative patients. In total, 192 patients after elective surgery were enrolled. Baseline SPI and ANI data were acquired for 10 min in the operating room prior to surgery when the patients rated their pain as 0 on the numerical rating scale (NRS). Upon arrival in the post-anaesthesia care unit (PACU) after surgery, SPI and ANI data were recorded for 10 min. The means of the recorded data at OR and PACU were defined as the values representing baseline and postoperative pain, respectively. SPI and ANI data obtained from 189 patients were analysed, who were anesthetized with propofol (n = 149) or sevoflurane (n = 40). Remifentanil was continuously infused intraoperatively in all patients. The values of SPI and ANI were significantly different in conscious patients without (NRS = 0) and with pain (NRS > 0). The areas under the receiver operating curves for SPI and ANI were 0.73 (P < 0.0001) and 0.67 (P < 0.0001), respectively. The cut-off values for SPI and ANI in predicting postoperative pain were 44 (sensitivity: 84%, specificity: 53%) and 63 (sensitivity: 52%, specificity: 82%), respectively, which are different from those suggested by their respective manufacturers for use in intraoperative state under general anaesthesia. The cut-off values of SPI and ANI for detecting pain were similar regardless of the type of anesthesia.

Effects of Thoracic Paravertebral Block on Nociceptive Levels After Skin Incision During Video-Assisted Thoracoscopic Surgery

Background

Regional anesthesia provides excellent analgesic effects after surgery. However, the effects of regional anesthesia on nociceptive levels during surgery under general anesthesia have not been quantitatively evaluated. To reveal the effects of thoracic paravertebral block (PVB) on nociceptive levels after skin incision during general anesthesia, we performed a retrospective cohort study in patients without serious preoperative conditions or comorbidities undergoing elective video-assisted thoracoscopic surgery (VATS). Nociceptive levels during general anesthesia were calculated using our previously determined Nociceptive Response (NR) equation, which utilizes common hemodynamic parameters.

Material/Methods

Data on 77 adult patients who underwent VATS from May 2018 to August 2018 were retrospectively obtained from our institutional database. We then performed propensity score matching between patients who received thoracic PVB (PVB group: n=29) and those who did not (Control group: n=48). The averaged values of systolic blood pressure (SBP), heart rate (HR), perfusion index (PI), bispectral index (BIS), and NR from 10 to 5 minutes before skin incision (T0), 5 to 10 minutes (T1), 10 to 15 minutes (T2), 15 to 20 minutes (T3), and 20 to 25 minutes after skin incision (T4), were calculated.

Results

Twenty-four propensity score-matched patients in each group were analyzed. Mean NR values at T1 and T2 in the PVB group were significantly lower than those in the Control group. SBP, HR, PI, and BIS, however, showed no significant differences between the 2 groups, except for SBP at T2.

Conclusions

Thoracic PVB prevented an increase in NR values, which quantitatively represent nociceptive levels under general anesthesia, in patients undergoing VATS.