Impact of Dexmedetomidine and Ketamine and Their Combination for the Reduction of Postoperative Morphine Requirements After VATS Surgery

Video-assisted thoracic surgery (VATS) for pulmonary resection is associated with less tissue trauma, less impairment in lung function, and reduced postoperative pain compared with thoracotomy, although many patients continue to report significant acute postoperative pain. If not well-controlled, postoperative thoracic pain can lead to splinting and inadequate recovery of pulmonary function.

Enhancing the quality of postoperative analgesia while reducing intra and postoperative opioid requirements is an important issue that has been one of the main focus of Enhanced Recovery After Surgery (ERAS) protocols. Indeed, the key factors that delay postoperative recovery include parenteral opioids and bed rest and immobility secondary to postoperative pain. While opioids are effective at treating even severe pain, their use is associated with dose-related adverse effects such as respiratory depression, sedation, postoperative nausea and vomiting, urinary retention, ileus, opioid-induced hyperalgesia and chronic postoperative pain. More importantly, opioids depress host immunity and neuroendocrine function and may negatively affect cancer recurrence and survival after lung cancer surgery.

Hence, given the importance of good postoperative analgesia and the significance of opioid-related adverse effects, the reduction of opioid requirements and postoperative pain through multimodal analgesia is an important matter. Focusing on this goal, the ERAS protocols have shown great efficacy in improving patient's care after colorectal surgery and they are now being applied to pancreatic, ENT, bariatric, urologic and many more major surgeries.

It is probably only a matter of time before ERAS protocols are applied to VATS surgery; however, the optimal way of providing postoperative analgesia after VATS has not yet been determined, unlike colorectal surgery. Indeed, thoracic epidural analgesia, single-shot and continuous paravertebral and intercostal nerve blocks and patient-controlled intravenous analgesia have all been evaluated, and none of these has consistently emerged as being superior to the others or to intravenous analgesia. Thoracic epidural analgesia provides effective pain control for thoracotomy but its benefits following thoracoscopy are not uniform. Furthermore, the risks of sympathectomy-induced hypotension and neurologic injury from epidural hematoma may not be justified considering the lesser postoperative pain and impairment in pulmonary function compared to thoracotomy. Continuous paravertebral blocks are an effective alternative to epidural analgesia although their performance may be challenging and time consuming, and catheters may be difficult to thread or get accidentally removed, leading to block failure. Furthermore, as for epidural analgesia, paravertebral catheter placement is contra-indicated in patients with impaired coagulation and/or infection. Single-shot intercostal and paravertebral blocks are less invasive although their benefit is restricted to the first twelve postoperative hours.

Moreover, none of these regional anesthesia techniques can treat the ipsilateral shoulder pain that is often associated with VATS, and opioid analgesia might still be required.