2022 年 29 巻 3 号 p. 43-45
Robot-assisted thoracic surgery (RATS) was introduced as a low invasive surgery system. In this study, we retrospectively investigated the frequency of patients prescribed gabapentinoids who underwent RATS and VATS for a possible occurrence of chronic postoperative neuralgia (CPN).
This study was approved by the institutional review board of Graduate School of Medicine, Chiba University (IRB #3063). The information of the study was disclosed on our website and the participants were given the chance to opt-out from the study on his/her own will.
The study was conducted retrospectively using electronic medical records and anesthesia charts. Patients were those who underwent RATS or VATS in the department of respiratory surgery between August 1, 2018 and August 1, 2020 in Chiba University hospital. All patients underwent general anesthesia with single lung ventilation using double lumen endotracheal intubation. We investigated the prescription rate of gabapentinoids (pregabalin or milogabalin besilate) postoperatively up to 3 months of the surgery. It was the surgeon's decision to prescribe and also to stop gabapentinoids.
The primary endpoint was the frequency of patients prescribed gabapentinoid in RATS and VATS. First, the frequency of prescription was simply compared between the two surgery methods. After which, propensity score matching was performed to exclude the difference in the patients' backgrounds. Statistical analysis was performed using EZR with R (3.5.2).
The number of patients who underwent RATS and VATS within the period covered was 85 and 314, respectively. Patients had either primary lung tumors, malignant mesothelioma or mediastinal tumors.
Patients prescribed gabapentinoids were 14 out of 85 (16.5％) in RATS and 23 out of 314 (7.3％) in VATS (p＝0.018, χ2 test). However, the patient backgrounds showed significant difference in age (RATS: 67.9±9.9, VATS: 63.7±16.3, p＝0.02, t-test), preoperative use of analgesics (RATS: 1 [1.2％], VATS: 44 [14.0％], p＜0.001, χ2-test), thoracic epidural anesthesia (RATS: 74 [87.1％], VATS: 228 [72.6％], p＝0.006, χ2-test), anesthetic time (RATS: 245±72.5, VATS: 216.6±66.1, p＜0.001, t-test), and operation time (RATS: 163.3±63.8, VATS: 131.7±60.0, p＜0.001, t-test). The results after 1 to 1 PS matching is summarized in Table 1. Total of 82 patients in each surgery groups were analyzed. Prescription rate of gabapentinoids was significantly higher in RATS patients.
| Factors | RATS （82） | VATS （82） | P |
| Gabapentinoids prescription | 14 （17.1％） | 5 （6.1％） | 0.049＊ |
| Sex （M:F） | 45:37 | 49:33 | 0.636 |
| Age | 67.77±9.96 | 68.18±12.34 | 0.72 |
| Height （cm） | 160.89±8.47 | 161.81±8.19 | 0.48 |
| Weight （kg） | 60.68±10.00 | 62.61±11.51 | 0.38 |
| Disease | 0.75 | ||
| Primary lung cancer | 68 （82.9） | 68 （82.9） | |
| Mediastinal tumor | 12 （14.6） | 10 （12.2） | |
| Malignant mesothelioma | 2 （2.4） | 4 （4.9） | |
| Preoperative use of analgesics | 1 （1.2） | 1 （1.2） | 1.00 |
| History of psychiatric disease | 2 （2.4） | 1 （1.2） | 1.00 |
| Thoracic epidural anesthesia | 71 （86.6） | 72 （87.8） | 1.00 |
| Anesthesia time （min） | 257.80±70.35 | 242.49±70.54 | 0.45 |
| Operation time （min） | 170.52±63.95 | 163.65±61.34 | 0.48 |
| Intraoperative drugs | |||
| remifentanil dosage （µg/kg） | 28.01±15.60 | 26.97±16.45 | 0.68 |
| fentanyl dosage （µg/kg） | 3.17±1.90 | 3.02±1.72 | 0.61 |
| acetaminophen＊＊ use | 59 （71.95％） | 58 （70.73％） | 1.00 |
| flurbiprofen axetil＊＊＊ use | 36 （43.90％） | 30 （36.56％） | 0.43 |
＊Significant difference, ＊Dosage of acetaminophen was 15 mg/kg or 1,000 mg if patients’ weight were over 50 kg, ＊＊Dosage of flurbiprofen axetil was 10 mg/kg or 50 mg if patients’ weight were over 50 kg.
RATS: robot-assisted thoracic surgery, VATS: video-assisted thoracic surgery, CPN: chronic postoperative neuralgia.
The prescribed gabapentinoids were pregabalin in most cases (both 78％ in RATS and VATS), started within 4 to 90 days (median 27.5 days) post-operation. There was no patient who needed additional treatment such as neural blocks.
The present study revealed that patients operated with RATS were observed with significantly more adjuvant analgesics prescription presumably indicating more incidence of CPN than those with VATS.
RATS, a newly developed surgery approach, which provide improved view and degree of freedom with forceps movement, is considered less traumatic to the intercostal nerves. Accordingly, less incidence of CPN is expected. However, superiority of RATS regarding pain has not been reported so far. Other reports show similar acute and chronic pain after RATS and VATS1).
Although the surgeon's prescription is not after precise diagnostic criteria for neuropathic pain, our result may suggest the possibility of RATS being more prone to induce CPN than VATS.
The reason for increased incidence is not clear. Simple increase in the number of ports in RATS (5 ports) compared with VATS (3–4 ports) may explain increased acute post-operative pain leading to CPN. The importance of the number of ports in postoperative pain has been reported2).
Multiple-limitations of this study must be considered. First, it is a retrospective study conducted at a single facility which newly introduced the method. Surgeons' learning curve needs to be considered3). Second, the diagnosis of pain nor decision for prescription was not following the diagnosis of neuropathic pain. Medical questionnaire, for example pain DETECT, should be used to diagnose neuropathic pain more precisely. However, pain in the area of surgery diagnosed by the surgeons who are experts in detecting infection and/or tumor recurrence, is very likely to be CPN. Third, the intensity nor the prognosis of the CPN was not investigated. Thus we do not know whether these pain reponded to gabapentinoids.
In conclusion, although RATS is considered to be a representative of minimally invasive surgery, the frequency of patients prescribed gabapentinoids was judged to be higher than that of VATS in this study. There are still few reports examining the relationship between RATS and CPN, and the factor contributing to CPN in RATS is not clear. We need to continuously explore the risk factors for CPN in RATS as more cases are expected to be indicated in the future.
