Hypotension after intercostal nerve block during thoracotomy under general anaesthesia

Efficacy of intraoperative thoracoscopic intercostal nerve blocks in nonintubated and intubated video-assisted thoracic surgery: A randomized study

BACKGROUND

The efficacy of thoracoscopic intercostal nerve blocks (TINBs) for noxious stimulation from video-assisted thoracic surgery (VATS) remains unclear. The efficacy of TINBs may also be different between nonintubated VATS (NIVATS) and intubated VATS (IVATS). We aim to compare the efficacy of TINBs on analgesia and sedation for NIVATS and IVATs intraoperatively.

METHODS

Sixty patients randomized to the NIVATS or IVATS group (30 each) received target-controlled propofol and remifentanil infusions, with bispectral index (BIS) maintained at 40-60, and multilevel (T3-T8) TINBs before surgical manipulations. Intraoperative monitoring data, including pulse oximetry, mean arterial pressure (MAP), heart rate, BIS, density spectral arrays (DSAs), and propofol and remifentanil effect-site concentration (Ce) at different time points. A two way ANOVA with post hoc analysis was applied to analyze the differences and interactions of groups and time points.

RESULTS

In both groups, DSA monitoring revealed burst suppression and α dropout immediately after the TINBs. The Ce of the propofol infusion had to be reduced within 5 min post-TINBs in both NIVATS (p < 0.001) and IVATS (p = 0.252) groups. The Ce of remifentanil infusion was significantly reduced after TINBs in both groups (p < 0.001), and was significantly lower in NIVATS (p < 0.001) without group interactions.

CONCLUSION

The surgeon-performed intraoperative multilevel TINBs allow reduced anesthetic and analgesic requirement for VATS. With lower requirement of remifentanil infusion, NIVATS presents a significantly higher risk of hypotension after TINBs. DSA is beneficial for providing real-time data that facilitate the preemptive management, especially for NIVATS.

Postthoracotomy pain management

The following techniques appear efficacious in controlling postthoracotomy pain and reducing the amount of systemic opioids consumed: continuous intercostal blockade, paravertebral blockade, and epidural opioids and/or anesthetics. The combination of thoracic epidural opioid and local anesthetic is very effective at relieving postthoracotomy pain, however, considerable experience is required for insertion of the thoracic epidural catheter and postoperative respiratory monitoring. Intercostal and paravertebral catheters can be inserted intraoperatively under direct visualization, to reduce complications of insertion. One-time intraoperative intercostal blockade may effectively reduce postoperative pain in the first day, but is not a practical long-term method for postthoracotomy pain. The effectiveness of interpleural analgesia, even with proper technique, appears inferior to epidural and other regional techniques. We have incorporated the principles outlined in this review into our general thoracic surgery protocol, as detailed in Fig. 1. Every patient is assessed preoperatively for epidural catheter placement. Contraindications include low platelet count (< 100,000), abnormal coagulation profile, medicinal anticoagulation (aspirin and nonsteroidal anti-inflammatories are not contraindications), bony spinal abnormalities, or neurological disorders. The T5/6 interspace is our preferred level, but T10 can work well with an increased dose of bupivacaine. Upon completion of the muscle sparing, minimal-access thoracotomy, we close the wound and perform a percutaneous intercostal nerve block (two ribs above and three below the incision). We then use patient-controlled epidural analgesia, with a basal infusion of bupivacaine and hydromorphone. To supplement inadequate or nonfunctioning epidurals, intravenous patient-controlled opioids are added. When choosing an approach to postthoracotomy pain management, the thoracic surgeon and anesthesiologist must consider the following: (1) the physician's experience, familiarity and personal complication rate with specific techniques; (2) the desired extent of local and systemic pain control; (3) the presence of contraindications to specific analgesic techniques and medications; and (4) availability of appropriate facilities for patient assessment and monitoring postthoracotomy. Refinements in surgical technique including limited or muscle-sparing thoracotomy, video-assisted thoracoscopic surgery (VATS) and robotic surgery may lessen the magnitude of postthoracotomy pain. We encourage all thoracic surgeons to be knowledgeable of available techniques and maintain a protocol to generate a database for periodic assessment of safety and efficacy.

Haemothorax after attempted intercostal catheterisation

A 30-year-old man with chronic abdominal pain was referred to the Pain Relief Unit after a course of unsuccessful diagnostic blocks and treatments. On admission, history, examination and clinical investigations were consistent with a large pleural effusion due to a recent attempt to catheterise the intercostal space. Pleural drainage confirmed the diagnosis of haemothorax. Percutaneous intercostal nerve blocks are usually considered as safe and simple and no-one to our knowledge has reported such a complication.

Hemodynamic effects of interpleural analgesia in pigs

Six anesthetized pigs received bupivacaine 2 mg/kg with epinephrine 2 micrograms/kg interpleurally while six saline injected animals served as controls. The animals were monitored hemodynamically for 120 min after injection. There were no significant changes in hemodynamic variables in the control group. In the group receiving bupivacaine with epihephrine there was a pattern of increase in mean arterial blood pressure, systemic vascular resistance and mean pulmonary arterial blood pressure after 60 min of observation. There were no other significant changes in pulmonary or systemic hemodynamics or gas exchange as evaluated by blood gases or whole body oxygen consumption. It is speculated that the increased systemic vascular resistance was an effect of the epinephrine added to the anesthetic. Interpleural analgesia may be a safe pain-relieving method even in slightly hypovolemic individuals.

Upper limb sympathetic blockade following intercostal nerve blocks

A case of transient sympathetic block of the arm following percutaneous intercostal nerve injections is described and the possible aetiology discussed.

Anatomy of the intercostal nerve: its importance during thoracic surgery

Complications from attempts to block the intercostal nerves intraneurally before closure of a thoracotomy have resulted in hypotension with or without spinal block. Placement of a chest tube has resulted in transection of the intercostal nerve. The first of these complications can be avoided by not attempting intraneural block of the nerves intrathoracically. Avoidance of the latter requires careful dissection of the intercostal spaces and identification of the intercostal nerve, as opposed to stab insertion of a chest tube.