Comment on: “Thoracic Paravertebral Block Ameliorates POD in Geriatric Patients”

Re: Heng et al Thoracic paravertebral block ameliorates postoperative delirium in geriatric patients. Thorac Cardiovasc Surg 2021 Sep 14. (e-pub ahead of print). doi:10.1055/s-0041-1731788.

As this is a letter to the editor that comments on the published paper in The Thoracic and Cardiovascular Surgeon and is not involved in any human study, the IRB approval, consent statement, and clinical trial registration are not applicable.

By a randomized controlled trial (RCT) of 128 geriatric patients undergoing pulmonary resection, Heng et al [1] showed that in comparison to conventional patient-controlled analgesia (PCA), continuous thoracic paravertebral block (CTPB) decreased the incidence of postoperative delirium (POD) and improved postoperative pain control. The findings of this study have potential clinical implications, but there are several methodological issues on which we wish to invite the authors to comment.

First, this is an RCT with strict inclusion and exclusion criteria. According to the revised CONSORT guidelines,[2] the authors should provide a flowchart for the eligibility of their study objects. In this way, the readers can clearly know how many patients were screened based on the criteria of inclusion and exclusion to obtain 128 eligible study objects. Furthermore, the objects of this study are geriatric patients with a mean age of approximately 70 years. The patients with severe auditory and visual impairment, a long-term use of narcotic analgesics and sedative and hypnotic drugs, and a history of cognitive dysfunction or chronic alcoholism were excluded, but it was unclear whether preoperative cognitive scores of included patients were comparable between the groups. In the available literature, a decreased preoperative cognitive score has been significantly associated with the occurrence of POD following surgery in geriatric patients.[3]

Second, the design of this study did not include a sample size evaluation, though it is a crucial content of designing a RCT for preventing the type I and type II statistical errors.[4] Furthermore, the authors did not clearly describe the expected minimal clinically important difference of primary end point between the groups. Because of these limitations, we are concerned that the sample size of this study may not be powered to show the between-group differences in the incidences of POD at 3 and 4 days after surgery.

Third, the authors described that propofol infusion rate for maintenance of anesthesia was adjusted to maintain the target Bispectral Index Score at 40 to 60 and the total consumption of propofol was significantly decreased in the patients receiving CTPB. We are very interested in knowing whether two groups were comparable with respect to mean Bispectral Index Scores during anesthesia. In clinical practice, the dosages of anesthetic and analgesic drugs are generally calculated according to the body weight of a patient. It was unclear whether the CTPB had significantly decreased total consumption of propofol when expressed per kg body weight. In addition, mean operation time was 151 to 157 minutes and infusion rate of remifentanil for maintenance of anesthesia was 0.1 to 0.3 mg/kg/min. However, the total consumption of remifentanil only was 2.1 ± 0.5 mg and 2.7 ± 0.6 mg in the CTPB and PCA groups, respectively. We questioned the total consumption of remifentanil for the maintenance of anesthesia in the two groups.

Fourth, the authors did not provide the goal of postoperative analgesia. To determine the real impact of an intervention on primary outcome in an RCT, other influencing factors must be strictly controlled to avoid bias. We noted that pain scores during coughing at 6, 12, and 24 hours after operation were considerably decreased in the patients receiving CTPB. Because inadequate postoperative pain control is a known risk factor for the development of POD in elderly patients,[5] we argue that this imbalanced factor would have biased their findings.

Finally, the prevalence of postoperative adverse events including POD, pulmonary atelectasis, nausea/vomiting, and itchiness was significantly decreased. Indeed, a 0.7-day of mean hospital stay was also shortened in the patients receiving CTPB. Relative to twofold to threefold of reduction in the incidence of POD with CTPB, however, it is difficult for the readers to determine whether this slightly shortened hospital stay should be considered as being clinically important. Especially, the authors did not assess other quality outcomes of enhanced recovery after surgery protocols for thoracoscopic surgery, such as the time to first ambulation, patients' satisfaction with postoperative analgesia, preservation of lung function, the quality of postoperative recovery and others.[6] Thus, an important issue that this study cannot well answer is whether both reduced incidence of POD and improved postoperative pain control by CTPB compared with PCA can really be translated into the clinical benefits of recovery outcomes in patients undergoing thoracoscopic surgery.

The authors of the original article chose not to reply.

Markus K Heinemann, MD, PhD

Editor-in-Chief

The Thoracic and Cardiovascular Surgery

Publication History

Received: 14 February 2022

Accepted: 18 March 2022

Article published online:
27 July 2022

• References

• 1 Heng L, Wang M, Wang M, Li L, Zhu S. Thoracic paravertebral block ameliorates postoperative delirium in geriatric patients. Thorac Cardiovasc Surg 2022; 22: 1
• 2 Schulz KF, Altman DG, Moher D. CONSORT Group. CONSORT 2010 statement: updated guidelines for reporting parallel group randomized trials. Ann Intern Med 2010; 152 (11) 726-732
• 3 Nazemi AK, Gowd AK, Carmouche JJ, Kates SL, Albert TJ, Behrend CJ. Prevention and management of postoperative delirium in elderly patients following elective spinal surgery. Clin Spine Surg 2017; 30 (03) 112-119
• 4 Greene T. Randomized controlled trials 5: determining the sample size and power for clinical trials and cohort studies. Methods Mol Biol 2015; 1281: 225-247
• 5 Denny DL, Such TL. Exploration of relationships between postoperative pain and subsyndromal delirium in older adults. Nurs Res 2018; 67 (06) 421-429
• 6 Gupta R, Van de Ven T, Pyati S. Post-thoracotomy pain: current strategies for prevention and treatment. Drugs 2020; 80 (16) 1677-1684