Comparison of Changes in the Optic Nerve Sheath Diameter Following Thoracic Epidural Normal Saline Injection in Laparoscopic Surgery.

BACKGROUND: Thoracic epidural analgesia is useful for postoperative pain control after upper abdominal surgery. However, epidural analgesia in patients undergoing laparoscopic surgery may potentiate an increase in intracranial pressure (ICP). ICP can be effectively evaluated by measuring the optic nerve sheath diameter (ONSD).

OBJECTIVES: The purpose of this study is to investigate changes in the ONSD following thoracic epidural normal saline injection during laparoscopic surgery.

STUDY DESIGN: Prospective randomized trial.

SETTING: An interventional pain management clinic in South Korea.

METHOD: This study included 60 patients receiving thoracic epidural catheterization for postoperative pain control following laparoscopic or open gastrectomy. Patients were divided into 3 groups. The open group consisted of patients undergoing open gastrectomy without epidural normal saline injection. The lapa-saline and lapa groups consisted of patients undergoing laparoscopic gastrectomy with and without 10 mL epidural normal saline injection, respectively. The ONSD was measured using ultrasound at 4 time points.

RESULTS: The lapa-saline group showed the most pronounced increase in the ONSD compared to the open and lapa groups at the time points of T1 and T2. Only the lapa-saline group demonstrated 4 patients with ONSD values of more than 5.8 mm. The increase in the ONSD continued even after the deflation of pneumoperitoneum in the lapa-saline group, whereas the ONSD in the lapa group returned to near baseline value after the deflation of pneumoperitoneum.

LIMITATIONS: Epidural normal saline was injected instead of a local anesthetic to prevent the occurrence of hypotension. However, the injection of epidural normal saline is considered to be the same physiological condition causing elevation of ICP compared with epidural injection with local anesthetics.

CONCLUSIONS: The lapa-saline group showed the most pronounced increase in the ONSD. The ONSD values higher than 5.8 mm were observed only in the lapa-saline group. The increase in the ONSD continued even after the deflation of pneumoperitoneum only in the lapa-saline group.