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Efficacy of Ultrasound-Guided Serratus Plane Block on Postoperative Quality of Recovery and Analgesia After Video-Assisted Thoracic Surgery: A Randomized, Triple-Blind, Placebo-Controlled Study

Kim, Do-Hyeong MD*; Oh, Young Jun MD, PhD*; Lee, Jin Gu MD, PhD; Ha, Donghun MD; Chang, Young Jin MD, PhD§; Kwak, Hyun Jeong MD, PhD§

doi: 10.1213/ANE.0000000000002779
Regional Anesthesia and Acute Pain Medicine: Original Clinical Research Report

BACKGROUND: The optimal regional technique for analgesia and improved quality of recovery after video-assisted thoracic surgery (a procedure associated with considerable postoperative pain) has not been established. The main objective in this study was to compare quality of recovery in patients undergoing serratus plane block (SPB) with either ropivacaine or normal saline on the first postoperative day. Secondary outcomes were analgesic outcomes, including postoperative pain intensity and opioid consumption.

METHODS: Ninety patients undergoing video-assisted thoracic surgery were randomized to receive ultrasound-guided SPB with 0.4 mL/kg of either 0.375% ropivacaine (SPB group) or normal saline (control group) after anesthetic induction. The primary outcome was the 40-item Quality of Recovery (QoR-40) score at 24 hours after surgery. The QoR-40 questionnaire was completed by patients the day before surgery and on postoperative days 1 and 2. Pain scores, opioid consumption, and adverse events were assessed for 2 days postoperatively.

RESULTS: Eighty-five patients completed the study: 42 in the SPB group and 43 in the control group. The global QoR-40 scores on both postoperative days 1 and 2 were significantly higher in the SPB group than in the control group (estimated mean difference 8.5, 97.5% confidence interval [CI], 2.1–15.0, and P = .003; 8.5, 97.5% CI, 2.0–15.1, and P = .004, respectively). The overall mean difference between the SPB and control groups was 8.5 (95% CI, 3.3–13.8; P = .002). Pain scores at rest and opioid consumption were significantly lower up to 6 hours after surgery in the SPB group than in the control group. Cumulative opioid consumption was significantly lower up to 24 hours postoperatively in the SPB group.

CONCLUSIONS: Single-injection SPB with ropivacaine enhanced the quality of recovery for 2 days postoperatively and improved postoperative analgesia during the early postoperative period in patients undergoing video-assisted thoracic surgery.

From the Departments of *Anesthesiology and Pain Medicine, Anesthesia and Pain Research Institute

Thoracic and Cardiovascular Surgery

Anesthesiology and Pain Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea

§Department of Anesthesiology and Pain Medicine, Gil Medical Center, Gachon University, Incheon, Republic of Korea.

Published ahead of print January 9, 2018.

Accepted for publication November 28, 2017.

Funding: None.

The authors declare no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website.

Reprints will not be available from the authors.

Address correspondence to Hyun Jeong Kwak, MD, PhD, Department of Anesthesiology and Pain Medicine, Gil Medical Center, Gachon University, 1198 Guwol-dong, Namdong-gu, Incheon 405–760, Republic of Korea. Address e-mail to

Since video-assisted thoracic surgery (VATS) was first introduced, it has become increasingly popular and gradually becoming the standard of care for lung surgery.1–3 Although VATS reduces postoperative pain because of its smaller incisions, pain control after VATS remains challenging.4,5 Thoracic epidural analgesia (TEA) and paravertebral blocks (PVBs) are optimal methods for postthoracotomy pain relief, and they are also widely used for pain management after VATS.6,7 However, the optimal regional analgesic technique for VATS procedures has not been established.8 Anesthesiologists and surgeons face the dilemma of using TEA and PVB, which are relatively invasive techniques accompanied by a risk of serious complications involving the pleura or central neuraxial structures, or other, less invasive methods of analgesia.

Regional analgesia was recently reported to improve recovery after nonthoracic surgery, when assessed by the 40-item Quality of Recovery (QoR-40) questionnaire, a validated multidimensional assessment tool.9–11 In this respect, regional analgesia may be a crucial component of multimodal postoperative pain management. Serratus plane block (SPB), a novel regional anesthetic technique, is an interfascial block introducing local anesthetic into the plane either above or below the serratus anterior muscle, under ultrasound guidance.12 It provides analgesia over most of the chest wall by blocking the lateral cutaneous branches of the thoracic intercostal nerves passing through these planes.13 Ultrasound-guided SPB is safe and easy to perform, owing to its easy-to-learn technique and distinct bony landmarks. Therefore, it could be an attractive alternative for pain control after VATS. Several recent reports described using SPB for thoracoscopic surgery.14,15 However, no clinical trial has investigated the effects of this block on recovery and analgesia after VATS.

In this prospective, randomized, triple-blind, placebo-controlled study, we tested the hypothesis that ultrasound-guided SPB would improve patient-perceived quality of recovery after VATS by reducing acute postsurgical pain. Our primary outcome measure was the global QoR-40 score on the first postoperative day (POD) in patients undergoing SPB with either ropivacaine or normal saline. Secondary outcomes were analgesic outcomes, including postoperative pain intensity and opioid consumption.

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The study protocol was approved by the Institutional Review Board of the Yonsei University Health System, Seoul, Korea (IRB #4-2014-0853) on November 26, 2014, and written informed consent was obtained from all subjects participating in the trial. The trial was registered before patient enrollment at (NCT02311517, principal investigator: Young Jun Oh; date of registration: December 8, 2014). This single-center study was conducted at Yonsei University College of Medicine in Seoul, Korea, between December 2014 and July 2016. We enrolled 90 patients (20–65 years old) with an American Society of Anesthesiologists’ physical status class of I or II, who were scheduled for elective VATS. Exclusion criteria were as follows: allergy to local anesthetics or contraindications to ropivacaine; known or suspected coagulopathy; injection site infection; preexisting neurological deficit or psychiatric illness; severe cardiovascular disease; liver failure; renal insufficiency (estimated glomerular filtration rate <15 mL/min/1.73 m2); chronic opioid use; pregnancy; and inability to communicate.

Enrolled patients were randomized to receive an ultrasound-guided SPB with either ropivacaine 0.375% (SPB group) or normal saline (control group). Randomization was performed using a computer-generated randomization sequence ( by an investigator not involved in patient care or perioperative assessment. Allocation results were concealed in sealed opaque envelopes, which were given to an anesthesia nurse not involved with the study. The nurse prepared ropivacaine or normal saline in identical 30-mL syringes according to the allocation. Consequently, the surgeons, attending anesthesiologists, investigators, nursing staff, and patients were blinded to the group assignment during the entire study. The anesthesiologist performed the SPB and subsequently assessed sensory blockade on arrival in the postanesthesia care unit (PACU) to ensure an experienced anesthesiologist with at least 5 years’ experience in pain management would accurately examine the dermatomal distribution of blockade. This anesthesiologist was blinded to group allocation and was not involved in patient care, perioperative assessment, or data collection. After patients were discharged from the hospital, which make the termination point of data collection, group assignment was revealed only to the attending surgeon to help provide appropriate pain management. This did not have an effect on the outcome of this blind study because the attending surgeon was not involved in data analysis and verification.

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Intraoperative Management

No premedication was administered. On arrival in the operating room, standard monitoring and measurement of the bispectral index were commenced. Immediately before anesthesia induction, patients were given intravenous (IV) glycopyrrolate 0.1 mg. General anesthesia was induced with propofol 1.5–2.0 mg/kg and remifentanil 1 µg/kg after administration of crystalloid 4 mL/kg. After the patient lost consciousness, rocuronium 0.9 mg/kg was administered to facilitate tracheal intubation, and intubation was performed using a double-lumen tube.

During 2-lung ventilation, patients received a 50/50 air/oxygen mixture and were mechanically ventilated using constant-flow volume-controlled ventilation. The tidal volume was 6–8 mL/kg predicted body weight, and the ventilatory frequency was adjusted to maintain an end-tidal carbon dioxide tension of 35–40 mm Hg. During 1-lung ventilation, patients were mechanically ventilated with 100% oxygen, using a tidal volume of 6 mL/kg predicted body weight and maintaining the end-tidal carbon dioxide tension at approximately 37–45 mm Hg. A radial artery catheter was placed for continuous arterial pressure monitoring. A 7-Fr central venous catheter was inserted if appropriate, depending on the anticipated extent of surgery and patient’s condition. Anesthesia was maintained with sevoflurane at a 0.7–1.5 age-adjusted minimal alveolar concentration and remifentanil 0.05–0.2 μg/kg/min, aiming for a bispectral index of 40–60. Sevoflurane and remifentanil were also adjusted to maintain the mean arterial blood pressure (MAP) and heart rate (HR) within 80%–120% of preoperative values. Hypotension (MAP <80% of baseline) persisting for 5 minutes was treated with normal saline boluses and, if required, ephedrine, phenylephrine, or norepinephrine. Bradycardia (HR <40/min) was treated with atropine 0.5 mg.

IV fentanyl 1 µg/kg was injected 30 minutes before the end of surgery for postoperative analgesia, followed by IV patient-controlled analgesia (PCA). The PCA regimen consisted of fentanyl 10 μg/kg and palonosetron 0.075 mg, mixed with normal saline to a total volume of 100 mL. The disposable PCA device (Accufusor Plus; Woo Young Medical Co, Ltd, Seoul, Korea) was set to deliver a 2 mL/h background infusion and 0.5 mL on-demand bolus, with a 15-minute lockout time. Thus, this PCA setting allowed a background infusion of fentanyl 0.2 μg/kg/h and a bolus of fentanyl 0.05 μg/kg. The PCA was used for the first 48 hours postoperatively. At the end of surgery, neuromuscular blockade was antagonized with neostigmine 1 mg and glycopyrrolate 0.2 mg, and the trachea was extubated when the patient was fully awake and breathing adequately. Wound infiltration was not applied during the operation. All patients were transferred to the PACU.

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Serratus Plane Block

The SPB was performed after induction of anesthesia and positioning the patient for surgery. A single anesthesiologist (D.H.K.) familiar with ultrasound-guided nerve blocks performed the SPBs under ultrasound (GE LOGIQ e; GE Healthcare, Seoul, South Korea) guidance using a 5- to 13-MHz linear ultrasound transducer (12L-RS transducer; GE Healthcare). Superficial SPB, targeting the interfascial plane between the serratus anterior and latissimus dorsi muscles, was performed using the Blanco et al’s12 technique, with slight modifications. Superficial SPB is less dangerous than deep SPB because the needle enters shallower and the needle approach of superficial SPB is easier to most physicians. Although both techniques produce widespread dermatomal block, the superficial technique is known to provide wider and longer analgesia.12

After aseptically preparing the area required for the block, the transducer (in a sterile sleeve) was placed over the midclavicular region in the sagittal plane. It was moved in an inferior-lateral direction from the second rib in the midclavicular line to the fifth rib in the midaxillary line. The transducer was then advanced posteriorly and obliquely until the latissimus dorsi muscle was clearly visible between the midaxillary and posterior axillary lines. During the scout scanning, the thoracodorsal artery was visualized in every case, allowing us to avoid it. A 25-G 50-mm Quincke needle was introduced into the superficial serratus plane, using an in-plane technique from an inferoposterior to superoanterior direction. Correct positioning of the needle tip was confirmed by injecting normal saline (3 mL) to hydrodissect the intended plane. After confirming negative aspiration, 0.4 mL/kg of the prepared solution (ropivacaine or normal saline) was injected, and gradual spread of the injectate was confirmed in the target interfascial plane. The patient remained in the same position for surgical preparation and draping. Surgery began approximately 20 minutes after SPB was performed.

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PACU Management and Patient Assessments

In the PACU, patients rated their pain at rest and during coughing using an 11-point numeric rating scale (NRS: 0 = no pain, 10 = worst imaginable pain). Rescue analgesics (IV fentanyl 0.5–1.0 µg/kg or pethidine 25 mg) were administered when the pain score at rest was ≥4 or on patient request. Thirty minutes after PACU arrival, the anesthesiologist that performed the SPB determined the dermatomal distribution of sensory blockade by assessing the response to pinprick (25-G needle) along the midclavicular, midaxillary, and midscapular lines. Other than sensory blockade assessment, the anesthesiologist that performed the block was not involved in any data collection or patient care, thus maintaining his blind status. When their modified Aldrete scoring system reached 10, patients were eligible for PACU discharge. In the ward, the patients continued to receive PCA analgesia and as a supplement, all patients were prescribed with a codeine 10 mg/acetaminophen 250 mg/ibuprofen 200 mg combination tablet every 8 hours to maintain an NRS pain score <4. If patients reported an NRS pain score ≥4, tramadol 75 mg or oxycodone 10 mg was administered every 12 hours as a supplement. However, if the patients reported a persistent NRS pain score ≥4 or on patient request, rescue IV pethidine 25 mg, IV tramadol 50 mg, or short-acting oxycodone 5 mg was given. The type and dosage of opioid analgesics were determined by the attending surgeon. If severe nausea or vomiting occurs, we treated the patients with 10 mg metoclopramide. If severe nausea persisted despite the pharmacological treatment, or if respiratory depression (<6 breaths/min or oxygen saturation measured using a pulse oximeter <92% despite the supply of oxygen at 5 L/min via nasal prongs), urinary retention, dizziness, or pruritus occurred, PCA was stopped temporarily. Then, after these symptoms reversed, the PCA restarted.

The primary study outcome was the global QoR-40 score on POD 1. QoR-40 contains 40 questions assessing 5 recovery domains: emotional status, physical comfort, psychological support, physical independence, and pain.16,17 Each question is graded on a 5-point Likert scale: 1 = none of the time, 2 = some of the time, 3 = usually, 4 = most of the time, and 5 = all of the time. Global QoR-40 scores range from 40 to 200. While formal validation of the QoR-40 questionnaire is still lacking in the thoracic surgery population, QoR-40 has been widely validated for different surgical types and anesthetic techniques.18 All patients completed the questionnaire 1 day preoperatively and on PODs 1 and 2. We explained the system and verified that the patients understood all questions preoperatively. The secondary outcomes included postoperative pain, opioid consumption, and adverse effects. NRS pain scores at rest and during coughing were recorded 10 and 30 minutes after PACU arrival, immediately before PACU discharge, and 6, 24, and 48 hours postoperatively. Maximal pain scores during the time intervals 0–6, 6–24, and 24–48 hours after surgery were recorded. We also recorded opioid consumption during 0–6, 6–24, and 24–48 hours postoperatively and cumulative opioid consumption at 6, 24, and 48 hours after surgery. The consumption of the different type of postoperative opioids was converted to IV morphine equivalents using the GlobalRPh morphine equivalence calculator assuming no cross-tolerance accessed at Adverse effects, such as postoperative nausea and vomiting (PONV), urinary retention, dizziness, arrhythmia, atelectasis, lung abscess, and pneumonia, were recorded. The following perioperative data were also collected: MAP and HR (preinduction, 1 and 30 minutes after surgery start, just before the end of surgery, 10 and 30 minutes after PACU arrival, and just before PACU discharge), total remifentanil dose, total amount of PCA fentanyl used, anesthesia time, length of PACU stay, chest tube indwelling time, and length of hospital stay. An investigator blinded to the group allocation collected all outcome and perioperative data.

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Statistical Analysis

Normality of the data distribution was assessed using Kolmogorov–Smirnov test and Q–Q plot. Standard descriptive statistics of baseline variables were reported. Demographic balance of the randomized groups was analyzed using absolute standardized difference, defined as the absolute difference in proportions or means divided by the pooled standard deviation. Groups were compared on normally distributed data with an independent t test, nonnormally distributed data with the Mann–Whiney U test, and categorical variables with the χ2 test or Fisher exact test. The treatment effect of SPB on the QoR-40 scores measured on PODs 1 and 2 was assessed using a linear mixed model presented as difference in means with adjustment for the baseline score as a covariate. Fixed effects included treatment group, time, and treatment group-by-time interaction, and the random effect was patient indicator. An unstructured covariance structure was used. The corresponding confidence interval (CI) was appropriately adjusted for multiple comparisons with a Bonferroni correction.

Secondary outcomes were assessed as follows: The treatment effect of SPB on NRS pain scores at rest and during coughing measured 10 and 30 minutes after PACU arrival, immediately before PACU discharge, and 6, 24, and 48 hours postoperatively was assessed, respectively, using a linear mixed model with patient indicator as a random effect, and group, time, and group-by-time interaction as fixed effects. An unstructured covariance structure was used. The treatment effect of SPB on maximal pain scores and the opioid consumption during 0–6, 6–24, and 24–48 hours postoperatively was also assessed, respectively, using a linear mixed model, as per the previously described model. The effect of SPB on MAP and HR (preinduction, 1 and 30 minutes after the beginning of surgery, just before the end of surgery, 10 and 30 minutes after PACU arrival, and just before PACU discharge) was assessed using a linear mixed model with patient indicator as a random effect, and group, time, and group-by-time interaction as fixed effects. These linear mixed model analyses were followed by post hoc test with a Bonferroni correction.

In addition, both secondary outcomes at 6 hours after surgery (pain score at rest and opioid consumption) were analyzed together using a joint hypothesis testing as described by Mascha and Turan.19 We first assessed noninferiority on the pain score at rest and opioid consumption at 6 hours after surgery. Then, we evaluated superiority on each outcome at 6 hours after surgery only if noninferiority was established on both outcomes. Noninferiority hypotheses were assessed against a 1-sided significance criterion of 0.025 and superiority hypotheses were evaluated against a 1-sided significance criterion of 0.0125 (0.025/2). We used the CI method for noninferiority and superiority testing. For each noninferiority comparison, noninferiority was claimed if the upper limit of the 95% CIs for the difference in means of pain score at rest 6 hours postoperatively was less than the noninferiority Δ of 1, and if difference in means of opioid consumption at 6 hours after surgery was less than the noninferiority Δ of 2.0 mg.6 Superiority was claimed if the upper limit of the 97.5% CIs was <0 for either pain score at rest or opioid consumption.

All statistical analyses except linear mixed model analysis were performed using IBM SPSS software, version 20.0 (IBM Corp, Armonk, NY). SAS software version 9.2 (SAS Institute Inc, Cary, NC) was used for linear mixed model analysis. P < .05 was considered statistically significant. Data are presented as mean ± standard deviation, mean (CI), median (interquartile range), or number (%) except where otherwise indicated.

In the previous studies, the standard deviations of the global QoR-40 score on POD 1 were reported to be 23 or 16.2 in patient population undergoing diverse surgery, 16 in cardiac surgical patients, and 19 in neurosurgical patients.17,20–22 Among these standard deviations, the sample size calculation in this study was based on a standard deviation of 23.17 A >10-point difference between groups for the global QoR-40 score was considered clinically significant, based on past studies.9,10 Assuming α = .05 and β = .20 for a 10-point difference in global QoR between groups, the calculated sample size was 41 patients per group. To allow for a possible 10% dropout rate, the sample size was 45 patients per group.

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Of the 97 patients assessed for eligibility, 7 were excluded because of age <20 (n = 1), thrombocytopenia with a platelet count <50,000/mm2 (n = 1), or refusal to participate (n = 5). Thus, 90 subjects were enrolled. Five were excluded from analysis because of surgery conversion to open thoracotomy (n = 2 patients, SPB group) or refusal to participate during follow-up (n = 3; 2 in control group, 1 in SPB group). Consequently, 85 patients completed the study (Figure 1). Patient and operation characteristics including preoperative QoR-40 scores are detailed in Table 1.

Table 1.

Table 1.

Figure 1.

Figure 1.

Postoperative QoR-40 scores are demonstrated in Table 2. The group-by-time interaction for the comparison of global QoR-40 scores between the SPB group and the control group was not significant (P = .992). However, the global QoR-40 scores on both PODs 1 and 2 were significantly higher in the SPB group than in the control group (estimated mean difference 8.5, 97.5% CI, 2.1–15.0, and P = .003; 8.5, 97.5% CI, 2.0–15.1, and P = .004, respectively). The overall mean difference between the SPB and control groups was 8.5 (95% CI, 3.3–13.8; P = .002). For each QoR-40 dimension, there were no group-by-time interactions between the 2 groups over time. The overall mean differences between the 2 groups were 2.4 (99% CI, −0.2 to 5.0) in emotional status, 2.7 (99% CI, −0.5 to 5.8) in physical comfort, 0.8 (99% CI, −0.9 to 2.5) in psychological support, 1.5 (99% CI, 0.0–3.1) in physical independence, and 1.2 (99% CI, −0.7 to 3.1) in pain dimension (Table 2).

Table 2.

Table 2.

There was significant group-by-time interaction for the comparison of the pain scores at rest between the SPB group and the control group (P = .002). They were significantly lower in the SPB group at 10 and 30 minutes after PACU admission, PACU discharge, and 6 hours postoperatively (estimated mean difference −2.2, 95% CI, −2.9 to −1.4, P < .001; estimated mean difference −1.9, 95% CI, −2.5 to −1.2, P < .001; estimated mean difference −1.3, 95% CI, −1.9 to −0.7, P < .001; estimated mean difference −1.7, 95% CI, −2.5 to −0.9, P < .001, respectively). They were not significantly different in both groups at 24 and 48 hours after surgery. Pain scores during coughing were not significant different between groups when all time points were combined (P = .183). There was no significant group-by-time interaction for the comparison of maximal pain scores between the SPB group and the control group (P = .203, Supplemental Digital Content 1, Figure 1,

Figure 2 shows the time course for opioid consumption after surgery. Opioid consumption over time was significantly lower in the SPB group than in the control group (P = .021). In intergroup comparisons at each time interval, consumption was lower in the SPB group during 0–6 hours postoperatively (17.4 ± 5.4 mg vs 21.9 ± 7.1 mg; P = .005). Cumulative opioid consumption was significantly lower in the SPB group than in the control group at 6 hours (17.4 ± 5.4 mg vs 21.9 ± 7.1 mg; P = .002) and 24 hours (41.8 ± 11.9 mg vs 52.0 ± 17.9 mg; P = .003) postoperatively.

Figure 2.

Figure 2.

A joint hypothesis test was performed using both pain score at rest and opioid consumption at 6 hours after surgery (Table 3). The SPB group was noninferior to the control group on pain score at rest and opioid consumption; the upper confidence limits of pain score at rest (difference −1.69, 95% CI, −2.45 to −0.92; P < .001) and opioid consumption (difference −4.45, 95% CI, −7.17 to −1.73; P < .001) were less than their respective deltas. Furthermore, superiority was found on both pain score at rest (difference −1.69, 97.5% CI, −2.60 to −0.81; P < .001) and opioid consumption (difference −4.45, 97.5% CI, −7.57 to −1.33; P < .001). Therefore, SPB was more effective than placebo.

Table 3.

Table 3.

Supplemental Digital Content 2, Table 1,, shows the dermatomal distribution of sensory blockade in the SPB group. In 3 patients, the typical superficial serratus plane separation identified in sonographic images after injection was not seen while performing the block. Despite several needle position adjustments, the injectate spread in only a convex lens configuration. If we consider these block failures, the failure rate was 6.7%. However, the sensory blockade distributions in the midclavicular/midaxillary/midscapular lines were T3–T6/T3–T6/T3–T6, T3–T7/T3–T8/T3–T8, and T3–T5/T3–T7/T3–T5 in these patients. Therefore, we considered these partially successful blocks and included the patients in the final analysis.

Table 4.

Table 4.

The between-group difference in change of MAP and HR from baseline was consistent over time (group-by-time interaction P = .727, and P = .853, respectively, Supplemental Digital Content 3, Figure 2, Table 4 shows the data in intraoperative period in 2 groups including total remifentanil dose, blood loss or transfusion, frequency of hypotensive events, use of vasopressors, and operation or anesthesia time. Postoperatively, the incidence of PONV was 39.5% in the control group, and 16.7% in the SPB group. The incidences of urinary retention and dizziness were 0.0% and 2.3% in the control group, and 4.8% and 0.0% in the SPB group, respectively. The number of patients requiring temporary discontinuation of PCA was 9 (20.9%) in the control group and 5 (11.9%) in the SPB group. Discontinuation reasons were PONV (n = 8) and dizziness (n = 1) in the control group and PONV (n = 3) and urinary retention (n = 2) in the SPB group (Table 4). No patient exhibited block-related complications, such as local anesthetic toxicity, bleeding, or infection.

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This randomized, triple-blind, placebo-controlled study demonstrated significant improvement in the quality of recovery in patients undergoing VATS who received a single-injection ultrasound-guided SPB with ropivacaine 0.375% compared with normal saline. Furthermore, ropivacaine SPB provided superior pain relief in the early postoperative period, with significantly lower pain scores at rest and less opioid consumption up to 6 hours compared with control. Cumulative opioid consumption remained significantly lower up to 24 hours postoperatively in the ropivacaine SPB group.

Previous studies reported that regional analgesic techniques, including peripheral nerve blocks, not only improve postoperative analgesia but also improve patient-reported outcomes, especially the quality of recovery after surgery.9–11,23 Furthermore, when compared to open thoracotomy, VATS can minimize tissue damage and the stress response, thereby facilitating rapid recovery.24 However, decreasing pain scores may not be perceived by patients as an improved outcome if side effects are concurrently increased.25 Therefore, to determine the optimal regional analgesic technique for VATS, it is meaningful to assess improvement in patient-perceived recovery as a component of “fast-track” surgery26 and as part of the consumer-centered health care trend considering patient-reported outcomes as important end points.27 In this study, the global QoR-40 score on POD 1, which was the main outcome, was significantly higher in patients receiving ropivacaine SPB than in the control group. This supports the use of SPB for “fast-track” recovery after VATS.

Although patients receiving SPB had significantly lower pain scores and lower opioid consumption during 0–6 hours postoperatively, statistically significant differences between groups did not persist beyond this time. Considering the average duration of intraoperative anesthesia (approximately 164 minutes in this study), these outcomes are similar to the 730–780 minutes for the duration of blockade produced by superficial SPB using 0.125% levobupivacaine 0.4 mL/kg reported by Blanco et al.12 In patients undergoing bilateral VATS sympathectomy, Fiorelli et al28 found that preincisional infiltration of the surgical wounds with lidocaine on 1 side produced lower pain scores than normal saline on the other side in the first 24 hours postoperatively, but not thereafter. In patients receiving single-injection PVB for VATS, Vogt et al6 found significantly lower pain scores at rest and with coughing compared with the control group, which persisted for 48 hours postoperatively. However, there were no differences in postoperative PCA morphine consumption. Hill et al29 found that compared with controls, patients undergoing preoperative multilevel single-dose PVB received significantly less cumulative PCA morphine and reported lower pain scores in only the first 6 hours after block placement.

In this study, the duration of analgesia after single-injection SPB did not extend beyond the duration of the sensory block. This may be because SPB produces only a somatic block, not a sympathetic block, although the role of the sympathetic nervous system in acute pain is not firmly established.30–32 In addition, either the concentration or volume of local anesthetic used for SPB may not have been adequate for prolonged analgesia after VATS. The relatively high percentage of patients undergoing an extended VATS procedure, such as VATS lobectomy or segmentectomy, could be another cause. However, cumulative opioid consumption was significantly lower in the SPB group up to 24 hours, and although the differences between groups were not statistically significant, median pain scores at rest and during coughing were 1 point lower in the SPB group at 24 hours postoperatively. Therefore, the possibility that single-injection SPB performed before surgical incision provided preemptive analgesia for VATS could not eliminated. Further research is required to determine whether increasing the concentration of local anesthetic or using continuous infusion through a catheter prolongs analgesia.

Since SPB was originally introduced by Blanco et al,12 there has been increasing interest in this block as a useful regional technique for thoracoscopic surgery.33 Previous case reports or case series demonstrated its effectiveness for analgesia after VATS minor procedures and VATS lobectomy,14,15 during awake VATS,34 and after thoracotomy.35 Our study is the first published clinical trial demonstrating the effectiveness of single-injection ultrasound-guided SPB in patients undergoing VATS in not only significantly reducing pain and opioid consumption during the early postoperative period but also in significantly enhancing the quality of recovery up to POD 2. It has been known that most patients exhibit moderate to severe pain in the first hour after VATS.36 Therefore, although SPB did not produce prolonged analgesia, it is a valuable regional technique for the brief, but intense, pain associated with VATS. Furthermore, although the study was not powered to detect the difference in the incidence of PONV, patients receiving SPB had a lower incidence of PONV than the control group, which may reflect the block’s opioid-sparing effect. When performing SPB, the plane was easily viewed during ultrasonography because of its simple sonoanatomy and distinct bony landmarks. SPB is also safe to perform because the needle enters the chest wall at a shallow angle. Furthermore, the patient’s position can be the same as that used for the surgery; thus, no additional time is required for patient repositioning and the flow from anesthetic induction to surgical preparation and draping is uninterrupted.

Despite the advantages and analgesic effectiveness of SPB, when we reviewed postoperative pain scores and opioid consumption in patients receiving PVB for VATS reported in previous studies, although direct comparison was not possible, PVB seems to be superior.6,7,29 Therefore, SPB (as a simple somatic, peripheral nerve block) may not be a direct replacement for PVB or TEA. Instead, the primary clinical value of SPB could be as the main component of multimodal analgesia for patients undergoing VATS, rather than as a direct alternative to PVB or TEA. When considering strategies for pain management after VATS, an important variable is the possibility of converting to open thoracotomy.5 Therefore, the following algorithm might be a reasonable analgesic strategy for VATS: perform the less invasive SPB first before VATS, then if VATS is switched to an open thoracotomy, perform PVB or TEA (including the use of an indwelling catheter) at the end of surgery. Further research should examine the usefulness of multimodal analgesic strategies including SPB, as well as directly comparing SPB alone to PVB alone.

Our study has limitations. First, we assessed the dermatomal distribution of blockade 30 minutes after arrival in the PACU because the blocks were performed under anesthesia. Consequently, the spread of sensory blockade was tested approximately 3 hours after performing SPB, and the interval between block and testing varied among patients. However, while performing the block, we adjusted the position of the needle real-time using ultrasound guidance to try to obtain proper spread of the injectate in the target interfascial plane. Despite these efforts, in a few patients, the injectate spread was limited and the distribution of sensory blockade was relatively narrow. Although past studies reported that incomplete separation at the interfascial plane could occur with hydrodissection during superficial SPB in patients with previous breast cancer surgery,37,38 patients in the present study had no history of thoracic or breast surgery. Further studies should assess the time course of spread of sensory blockade after SPB and the definition of a failed block. Second, the Korean written version of the QoR-40 questionnaire, which was used in the present study, has not been formally validated. However, a previous study used this version with reliable results.39,40 Moreover, the range of scores obtained in this study was comparable to the scores of previous studies.41 Therefore, the language difference may not have distorted the results of this study. Third, the success of wound infiltration in studies addressing different surgical procedures suggested that wound infiltration might be an effective analgesic method in VATS.42 Thereby, comparing SPB and wound infiltration could lead to meaningful research reflecting real clinical situations. Nonetheless, there is a lack of research on the effectiveness of wound infiltration as an analgesic technique for VATS patients. Also, while there was no randomized controlled study on analgesic efficacy of SPB, there was a cadaveric study only on “deep” SPB.13 If SPB compared with wound infiltration, blinding could not be maintained. Therefore, the authors in this study prioritized to perform a randomized, blind, and placebo-controlled study making the patients receiving an SPB with normal saline as a control group. Fourth, it should be noted that this study was not powered for secondary outcomes including the incidence of PONV. Therefore, further studies are needed to investigate whether SPB in practice reduces the incidence of PONV. Finally, we admit that a mistake was made in calculating the sample size in this study. Based on the standard deviation of 23 reported in Myles et al’s17 study, the calculated sample size is, considering a 10-point difference in global QoR-40 scores between 2 groups with 2-sided α = .05 and β = .20, 82 patients per group. Therefore, the sample size in this study, 41 patients per group, was miscalculated. However, we could get the same sample size as in this study from the standard deviation of 16.2 which was shown in another report studying global QoR-40 scores in patient population undergoing various noncardiac surgeries similar to Myles et al’s17 study.

In conclusion, single-injection superficial SPB in patients undergoing VATS not only enhances the quality of recovery but also decreases pain and opioid consumption during the early postoperative period.

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Name: Do-Hyeong Kim, MD.

Contribution: This author helped conduct the study and write the manuscript.

Name: Young Jun Oh, MD, PhD.

Contribution: This author helped design the study and review the analysis of the data.

Name: Jin Gu Lee, MD, PhD.

Contribution: This author helped recruitment and collect the data.

Name: Donghun Ha, MD.

Contribution: This author helped conduct the study and collect the data.

Name: Young Jin Chang, MD, PhD.

Contribution: This author helped design the study, analyze the data, and review the analysis of the data.

Name: Hyun Jeong Kwak, MD, PhD.

Contribution: This author helped design the study, analyze the data, review the analysis of the data, and write the manuscript.

This manuscript was handled by: Richard Brull, MD, FRCPC.

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