Abstract
Objectives
Subcostal transversus abdominis plane (TAP) block and paravertebral block (PVB) offer postoperative analgesia for laparoscopic and thoracoscopic surgery, respectively. We investigated the early postoperative analgesic effects of PVB in combination with subcostal TAP block in patients undergoing minimally invasive esophagectomy (MIE) for esophageal cancer.
Methods
Seventeen patients undergoing MIE without nerve block for postoperative analgesia and 16 patients undergoing MIE with PVB and subcostal TAP block for postoperative analgesia were enrolled for the study. The surgeon performed PVB with bupivacaine at T4, T6, and T8 levels under video-assisted thoracoscopy at the end of the thoracoscopic stage. The anesthesiologist responsible for the anesthesia performed ultrasound-guided bilateral subcostal TAP with bupivacaine at the end of the surgery. Postoperative morphine consumption, pain severity, vital capacity, intensive care unit (ICU) stay, and complication rate were compared between groups.
Results
The group receiving nerve blocks consumed less morphine on postoperative Day 0 (p = 0.016), experienced lower levels of pain at postoperative 0 hour (p = 0.005) and 2 hours (p = 0.049), and had a shorter ICU stay (p = 0.02). No between-group differences in postoperative vital capacity and respiratory complications were observed.
Conclusion
PVB in combination with subcostal TAP block could reduce morphine consumption and pain severity in the early postoperative period but did not offer other clinical benefits in MIE.
Keywords
esophagus; nerve block: thoracic paravertebral; nerve block: transversus abdominis plane; surgical procedures, minimally invasive; thoracoscopy;
1. Introduction
Esophagectomy is a major surgical procedure often associated with significant morbidity and mortality.1, 2 Esophagectomy with thoracotomy incision is also a very painful surgery where thoracic epidural analgesia is usually used as a component of multimodal strategies to improve outcomes and thus it reduces costs.3, 4, 5 In an attempt to reduce postoperative morbidity and to shorten the recovery time, minimally invasive esophagectomy (MIE) has been used more often and is considered a comparable alternative in treating esophageal cancer.6
In contrast to open esophagectomy where epidural pain control has been considered as a gold standard and could be crucial in affecting outcome,3, 4, 5, 7, 8, 9, 10 the analgesic scheme for MIE is yet to be established. Peripheral regional anesthetic techniques could be considered as an attractive alternative to central blocks because their complication profile is better than that of neuraxial blocks,11 and the minimally invasive nature of MIE. Paravertebral block (PVB) with continuous infusion for esophagectomy through open thoracotomy offered early mobilization and lowered pain scores.12Continuous paravertebral infusion proved to be superior to epidural analgesia because of fewer side effects, preservation of pulmonary function, less neuroendocrine stress response, and less compromise of postoperative respiratory function while offering comparable analgesic effects in patients after thoracotomy.13, 14 For minimally invasive surgeries, subcostal transversus abdominis plane (TAP) block15 and PVB16, 17, 18, 19, 20 have an important role in multimodal postoperative analgesia in laparoscopic upper abdomen surgeries and video-assisted thoracic surgeries, respectively.
We hypothesized that PVB and subcostal TAP block could reduce postoperative pain in patients undergoing MIE for esophageal cancer. In this pilot study, we collected data on pain score, usage of analgesics, and other immediate postoperative outcomes from esophageal cancer patients undergoing minimally invasive surgery for esophageal cancer under general anesthesia with or without combined PVB and subcostal TAP block. The aim of the study was to investigate the analgesic effects of these peripheral regional anesthetic techniques and their influence on early postoperative outcome in patients who underwent MIE for esophageal cancer.
2. Methods
This study was approved by the Institutional Review Board of Koo Foundation Sun Yat-Sen Cancer Center. Data collection was carried out under rigid adherence of institutional guidelines and pursuant to the principles outlined in the Declaration of Helsinki.
PVB and subcostal TAP block had been used in a variety of surgeries in our center. We started the employment of combined PVB and subcostal block for MIE in January 2011. Data were retrospectively collected between January 2010 and January 2012 from consecutive patients undergoing MIE.
The techniques of MIE include entirely and partially minimally invasive procedures performed endoscopically either during the thoracic or the abdominal stage. In our institute, the standardized MIE comprises procedures of en bloc thoracoscopic esophagectomy, intrathoracic radical lymphadenectomy followed by laparoscopic gastric mobilization, cardiectomy, formation of gastric conduit, gastric tube pull-up via a posterior mediastinal route, and cervical anastomosis. These procedures are performed between stages I and IV esophageal cancer by one chest surgeon. Four thoracoscopic ports are placed. The 1.2-cm camera thoracoscopic port is placed through the right eighth intercostal space (ICS) at the posterior-axillary line. The 1.2-cm working thoracoscopic port is placed over the right sixth ICS at the anterior axillary line. Two additional 0.5-cm thoracoscopic ports are located over the right fourth ICS, one at the posterior axillary line and the other at the tip of the scapula. The sites for trocar placement are located over the upper abdomen, including one 12-mm and one 5-mm trocar over the bilateral paramedian about 5 cm above the umbilicus, another two 5-mm trocars over the bilateral subcostal areas and another 12-mm trocar over the umbilicus, and a 5-mm trocar over the subxyphoid area.
2.1. Procedure of anesthesia
The standardized anesthetic technique with general anesthetics consisted of propofol 2–2.5 mg/kg, cisatracurium 0.15 mg/kg, and fentanyl 100 μg for endotracheal intubation, and 5–8% desflurane titrated according to age, blood pressure, and heart rate for maintenance. All patients were intubated with double lumen endotracheal tubes.
2.2. Paravertebral block
A previous study showed that 97% of patients had adequate loss of sensation with four injections as opposed to only 11% with a single injection.21 To achieve better analgesia, a multilevel injection technique was adopted. Injections at T4, T6, and T8 were performed by the surgeon with 3 mL of 0.5% bupivacaine at each level under direct thoracoscopic visualization at the end of thoracic phase.
2.3. Ultrasound-guided subcostal TAP block
Subcostal TAP block accessed on the upper part of the transversus abdominis plane offered sensory block up to the T6–7 levels.22 Because the trocar sites for laparoscopy were located over the upper abdomen above the umbilical level, subcostal TAP block was thus used in this study. Ultrasound-guided (USG) subcostal TAP block was performed at the end of surgery by anesthesiologists experienced in this technique. The TAP was visualized using a SonoSite ultrasound apparatus (M-Turbo; Sono-Site, Inc., Bothell, Washington, USA) with a linear-array ultrasound transducer (13-6 MHz; HFL38). We adopted the in-plane technique as described by Hebbard,22 where the transducer was placed parallel to the costal margin as cephalad and as medially as possible. In all patients, the neurovascular and fascial planes between the transversus abdominis and the rectus abdominis muscles, or between the rectus abdominis and the posterior rectus sheath if the transversus abdominis was not behind the rectus abdominis at that level, were identified. Twenty milliliters of 0.375% bupivacaine with 1:400,000 epinephrine were injected incrementally on each side of the abdomen in a medial-to-lateral direction with a 22-gauge, 3.5-inch spinal needle (Terumo spinal needle, Terumo Corporation; Tokyo, Japan). After the block was administered, the patient was extubated and sent to the intensive care unit (ICU) for close observation.
2.4. Postoperative pain
Upon arrival at the ICU, patients were subject to assessment of pain scores with the numeric rating scale (NRS, 0 = no pain, 10 = worst pain). The intensity of pain was classified as mild (NRS 0–3), moderate (NRS 4–6), and severe (NRS 7–10).
In all patients, the goal of standardized postoperative analgesic management was an NRS pain score less than 4. Intravenous morphine 0.1–0.15 mg/kg was given as needed for severe pain throughout the postoperative course. In patients experiencing moderate pain, intravenous morphine 0.1 mg/as needed since the day of surgery, tramadol 37.5 mg/acetaminophen 325 mg combination (Ultracet®, Janssen Korea, Ltd., Korea) two tablets, or ibuprofen 400 mg would be given via the feeding jejunostomy beginning the day after surgery unless contraindicated.
Patients were discharged from the ICU when they met the discharge criteria, i.e., stable hemodynamics, absence of significant blood loss, and sufficient respiration under room air.
Because immediate postoperative pain level was chosen as the primary endpoint in this study, those patients who reentered the operating room during the early postoperative period and lacked the data of immediate postoperative pain level would be excluded.
The following matters were assessed: (1) level of pain on arrival at the ICU (postoperative 0 hour) and 2 hours and 6 hours postoperatively, (2) morphine or analgesic consumption during postoperative day (POD) 0 and POD 4, (3) vital capacity (VC) measured by incentive spirometer (IS), once per day from POD 0–4; (4) length of ICU stay, total complication rate, and respiratory complication defined as pneumonia with clinical symptoms, roentgenological findings, yielding culture, and the use of antibiotics.
Statistical analysis was carried out with SAS version 9.1 software (SAS Institute Inc., Cary, NC, USA). Data were presented as median (minimum, maximum). Nonparametric Wilcoxon two-sample test and Fisher exact test were used to test differences between the two groups of patients. The effect of nerve block on pain level was further tested with ordered logistic regression analysis. A two-tailed p < 0.05 was considered statistically significant.
3. Results
Between January 2010 and January 2012, there were 39 patients undergoing MIE, of whom two were excluded from the study because of reentry to the operating room on the same day due to bleeding, and 37 patients were subjected to provisional analysis. Among these 37 patients, one had epidural analgesia and three had an incomplete record of NRS pain scores.
A total of 33 patients (28 males and 5 females) were eligibly enrolled, among whom 16 had MIE with PVB and subcostal TAP block in the space from January 2011 to January 2012 (block group) and 17 had MIE without nerve block during 2010 (nonblock group).
Patient characteristics and surgical parameters are shown in Table 1. There was no significant difference in the patient demographic data, (age, sex, weight, and height) between the two groups. The nonblock group had a trend of more blood loss. The groups did not differ in ASA physical status classification, tumor staging, preoperative VC, history of preoperative concurrent chemoradiotherapy (CCRT), and surgical duration.
The degrees of severity of postoperative pain are shown in Table 2. More patients in the nonblock group had moderate or severe pain at postoperative 0 hour (p = 0.005) and 2 hours (p = 0.049). At postoperative 6 hours, only borderline significance (p = 0.071) was noted. On arrival at the ICU, six patients had severe pain and seven had moderate pain in the nonblock group. With intravenous morphine 0.1–0.15 mg/kg on demand for pain control and cumulative morphine consumption of 10 mg (range, 5–22 mg) on POD 0, a few patients in the nonblock group still had moderate pain at postoperative 2 hours and 6 hours (Table 2). The block group was less likely to be subjected to severe level of pain at all time points (p < 0.05; Table 3).
Morphine consumption on POD 0 in the block group was 5 mg (range, 0–10 mg) which was significantly lower than 10 mg (range, 5–22 mg) in nonblock group (p = 0.016), but was not so on POD 1, POD 2, POD 3, or POD 4. There was no difference in cumulative nonopioid analgesic consumption throughout the postoperative 4 days (Table 4).
No between-group differences in the VC on POD 0, POD 1, POD 2, POD 3, and POD 4 were observed. The incidence of pneumonia was similar in nonblock group and block group (11.8% vs. 12.5%), and was also similar in the total complication rate (41.2% vs. 37.5%). ICU stay was shorter in the block group as 1 (range, 1, 1) opposed to 1 (range, 1, 2) in the nonblock group (p = 0.02). Five patients of the nonblock group needed an additional day in the ICU because of postoperative complications such as fever in two patients, bleeding in one patient, and arrhythmia in two patients (Table 4).
There were no symptoms or signs suggestive of complications related to PVB, subcostal TAP block, or local anesthetic toxicities. There was no 30-day mortality in this cohort.
4. Discussion
This study is a retrospective evaluation of TAP block in combination with paravertebral block for postoperative analgesia following MIE. As far as we know, this is the first study that used PVB in combination with subcostal TAP block for management of postoperative pain in patients receiving MIE. In these two groups with matched patient characteristics and uniform procedure, PVB in combination with TAB block significantly reduced pain severity at postoperative 0 hour and 2 hours and morphine consumption on the day of surgery.
Although interpreted literally, MIE is a minimally invasive surgical procedure; we found that it was associated with significant levels of pain in patients without peripheral nerve blocks. First assessment on the arrival at the ICU revealed moderate to severe pain in 13 patients in the nonblock group and moderate pain in five patients in the block group. Morphine treatment was initiated immediately after the assessment. However, a majority of the patients (11 of 17) in the nonblock group had pain beyond moderate level at postoperative 2 hours. This implied that morphine alone was insufficient to adequately control the pain associated with MIE in the immediate postoperative period.
Pain level at postoperative 6 hours was not significantly different between groups. In contrast to our findings, single-shot PVB and TAP block could produce lower pain scores up to 48 hours after surgery in some studies.16, 23, 24, 25 Nevertheless, the duration of these blocks was studied in heterogeneous groups of surgical procedures among which none could reach a scale comparable to MIE in terms of extent and duration.
In previous studies, single-dose PVB 16, 19 and single-dose TAP block15 have been shown to improve postoperative pain control in video-assisted thoracoscopic surgeries and laparoscopic surgeries, respectively. Considering the entirely minimally invasive nature of MIE, which was performed endoscopically in both the thoracic and the abdominal stages, we chose a single dose instead of continuous infusion in our study. We found that morphine-sparing effect was only apparent on the day of surgery but was not so from POD 1 to POD 4. It is compatible with previous studies26, 27, 28 that single-shot PVB or TAP block produced an opioid-sparing effect for 24 hours.
PVB performed with the aid of thoracoscopy was considered simple and effective, and allowed direct visualization of correct delivery of local anesthetic.17, 20 However, pain from incisions crossing midline in the abdominal stage could hardly be covered by unilateral PVB. Bilateral PVB was not adopted in our study because it was associated with about eightfold unexpected pleural puncture or pneumothorax when performed with the aid of nerve stimulator as described in a previous study.11 We used bilateral subcostal TAP for analgesia of the superficial incisional pain29 over the upper abdomen, leaving visceral pain to be attended by systemic analgesics. In each patient, PVB and subcostal TAP block were performed at least 3 hours apart, with 45 mg of bupivacaine for PVB at the end of thoracoscopic stage and 150 mg for subcostal TAP block at the end of surgery. Although the total amount of bupivacaine was high, there were no clinical symptoms or signs suggestive of toxicity.
Incentive spirometer (IS) was demonstrated to be highly correlated with ventilometer in the measurement of VC in patients receiving coronary artery bypass graft surgery.30 IS can also be used to follow lung function in the postoperative period after lobectomy.31, 32 In our study, VC measured by IS showed no difference between groups throughout the postoperative period, indicating little effect of the blocks on the recovery of pulmonary function. However, small patient number, retrospective study design, suboptimal pain management with this technique, and short duration of single-dose block could also have contributed to the result. The incidence of pneumonia was similar in both groups in our study. However, according to the meta-analysis by Ballantyne et al,33 surrogate measures such as VC failed to predict or determine postoperative pulmonary morbidity. The number of patients in our study is insufficient to confirm these findings.
Significantly longer ICU stay in the nonblock group could have been due to situations that required one more day for observation in the ICU. Although the total complication rates were similar between groups, early complications in the block group seemed to be milder and thus allowed patients to be discharged to the floor earlier. The precise explanation for the increase in ICU stay in the nonblock group is unknown. Because the patients of the nonblock group were collected in the early period of the study, surgeon skill could have been a factor affecting the outcomes. Suboptimal perioperative pain management was less likely a factor directly affecting this parameter. However, small patient number and the design of the study did not allow us to draw a conclusion on the causal relationship among ICU stay, surgical factors, and analgesic factors. The role of blocks and surgical skills in the reduction of ICU stay remains speculative.
There were limitations in our study. First, it was a retrospective study using a historical control. Although identical surgical techniques and perioperative protocols were applied throughout the period of the study, and because more than 30 MIEs had been performed by the surgeons prior to 2010 when this study started, proficiency bias on the part of surgeon probably existed as was reflected by the trend of more blood loss in the nonblock group. Second, the small sample size and the retrospective study design could have made the clinical effect of blocks in the immediate postoperative period not readily apparent and thus limited the interpretation. Third, we did not discriminate the chest or the abdomen as the location where the patients suffered the most pain. Different locations of pain might have a different effect on postoperative pulmonary function or other clinical outcomes. Fourth, we performed single-shot PVB and single-shot subcostal TAP block instead of continuous infusion. The marginal benefits shown in this study were possibly due to the limited duration of the single local anesthetic dose. In addition it was not unexpected that the patients who underwent regional blocks were more comfortable than those who received only analgesics. A more pertinent comparison would be with thoracic epidural analgesia. Larger randomized studies of either PVB or subcostal TAP block with continuous infusion in comparison with epidural analgesic technique are necessary to substantiate the clinical effect of the blocks on the patients receiving MIE.
In this pilot report, we demonstrated that combined PVB and subcostal TAP block performed in patients receiving MIE as a part of multimodal postoperative analgesia could reduce early postoperative pain level and morphine consumption. Other clinical benefits were not significant. More controlled studies are required to substantiate the effects of combined PVB and subcostal TAP block on patients receiving MIE.