Contribution of the Spinal Cord to Arousal from Inhaled Anesthesia

Effects of Early Exposure to Isoflurane on Susceptibility to Chronic Pain Are Mediated by Increased Neural Activity Due to Actions of the Mammalian Target of the Rapamycin Pathway

Patients who have undergone surgery in early life may be at elevated risk for suffering neuropathic pain in later life. The risk factors for this susceptibility are not fully understood. Here, we used a mouse chronic pain model to test the hypothesis that early exposure to the general anesthetic (GA) Isoflurane causes cellular and molecular alterations in dorsal spinal cord (DSC) and dorsal root ganglion (DRG) that produces a predisposition to neuropathic pain via an upregulation of the mammalian target of the rapamycin (mTOR) signaling pathway. Mice were exposed to isoflurane at postnatal day 7 (P7) and underwent spared nerve injury at P28 which causes chronic pain. Selected groups were treated with rapamycin, an mTOR inhibitor, for eight weeks. Behavioral tests showed that early isoflurane exposure enhanced susceptibility to chronic pain, and rapamycin treatment improved outcomes. Immunohistochemistry, Western blotting, and q-PCR indicated that isoflurane upregulated mTOR expression and neural activity in DSC and DRG. Accompanying upregulation of mTOR and rapamycin-reversible changes in chronic pain-associated markers, including N-cadherin, cAMP response element-binding protein (CREB), purinergic P2Y12 receptor, glial fibrillary acidic protein (GFAP) in DSC; and connexin 43, phospho-extracellular signal-regulated kinase (p-ERK), GFAP, Iba1 in DRG, were observed. We concluded that early GA exposure, at least with isoflurane, alters the development of pain circuits such that mice are subsequently more vulnerable to chronic neuropathic pain states.

Sufentanil infusion before extubation suppresses coughing on emergence without delaying extubation time and reduces postoperative analgesic requirement without increasing nausea and vomiting after desflurane anesthesia

Background

Coughing, hypertension, tachycardia, and even laryngospasm can occur due to airway irritation during emergence from anesthesia. We investigated the effect of maintaining a sufentanil infusion during emergence from anesthesia by evaluating the incidence of cough and recovery profiles at extubation.

Methods

In total, eighty-four patients undergoing an elective laparoscopic hysterectomy were randomly divided into two sufentanil groups and a control group. During emergence, sufentanil was administered in the sufentanil groups at a rate of 0.2 µg/kg/hr (Group S1) or 0.3 µg/kg/hr (Group S2), and saline was administered to the control group. Cough score, hemodynamic changes, and recovery profiles, such as duration from skin closure to a bispectral index of 80, to eye opening at verbal command, to tracheal extubation and the total duration of study solution infusion, were recorded. The pain score, the total volume of administered patient-controlled analgesia (PCA), and the postoperative nausea and vomiting (PONV) score were evaluated 1, 6, and 24 hours after surgery.

Results

Groups S1 and S2 showed significantly lower cough scores and smaller hemodynamic changes on extubation compared to Group C. Recovery profiles showed no significant differences among the three groups. Pain score, PONV at 1 hour postoperatively, and the total volume of PCA administered at all evaluation times were significantly lower in Groups S1 and S2 than in the control group. However, pain score, and PONV at 6 hours and 24 hours postoperatively showed no significant differences.

Conclusions

A sufentanil infusion (0.2-0.3 µg/kg/hr) during emergence from desflurane anesthesia may suppress coughing on extubation in patients with body mass indexes (BMI) of 21-26 without delaying extubation time. It may also reduce the postoperative analgesic requirement without increasing PONV.

Advances in regional anaesthesia and pain management

Advances in regional anaesthesia to date have made it one of the safest modalities for surgical anaesthesia and pain management. Continued refinement and development of new block techniques and approaches enhance the potential for block success, rapid postoperative recovery and patient safety. This will benefit both patient care and the health care economy.