Effects of low-dose ketamine infusion on remifentanil-induced acute opioid tolerance and the inflammatory response in patients undergoing orthognathic surgery.

PURPOSE: Remifentanil is associated with acute opioid tolerance that can lead to increased postoperative consumption of opioid analgesics. The purpose of this study was to determine whether a low dose of ketamine prevents remifentanil-induced acute opioid tolerance and affects the neutrophil-lymphocyte ratio (NLR), a newly recognized biomarker of inflammation. MATERIALS AND METHODS: Forty patients undergoing orthognathic surgery were enrolled in this prospective, randomized, double-blind study and randomly assigned to intraoperative administration of one of the following anesthetic regimens: high-dose remifentanil (0.6 µg/kg/minute); low-dose remifentanil (0.2 µg/kg/minute); or high-dose remifentanil with ketamine (remifentanil 0.6 µg/kg/minute with 0.5 mg/kg ketamine just after induction followed by an intraoperative infusion of ketamine 5 µg/kg/minute until wound closure). Fentanyl by intravenous patient-controlled analgesia was used for postoperative pain control. Visual Analog Scale pain scores and fentanyl consumption were recorded in the first 24 hours postoperatively. Perioperative serum C-reactive protein level and NLR were also determined. RESULTS: Baseline characteristics were similar in the three study groups. There were no between-group differences in Visual Analog Scale pain scores during the study period. The high-dose remifentanil group had a significantly higher requirement for fentanyl than the other two groups. Addition of ketamine did not affect the C-reactive protein level but increased the NLR; this increase was associated with decreased fentanyl consumption. CONCLUSION: High-dose intraoperative remifentanil induced postoperative acute opioid tolerance that was prevented by infusion of low-dose ketamine. Ketamine increased the postoperative NLR associated with decreased fentanyl requirement for postoperative pain control.

Expression of ß-endorphin in peripheral tissues after systemic administration of lipopolysaccharide as a model of endotoxic shock in mice.

BACKGROUND: Endogenous ß-endorphin is delivered exclusively from the pituitary gland in various stressful conditions and plays an essential role in the nervous system. Recently, a few studies demonstrated peripheral endogenous opioid secretion from immune cells at inflammatory sites. Here, we investigated the expression of ß-endorphin, the most powerful endogenous opioid peptide, in peripheral tissues in response to systemic administration of lipopolysaccharide in mice. METHODS: Male C57BL/6N mice received intravenously administered lipopolysaccharide to induce an endotoxic shock-like condition. mRNA for proopiomelanocortin, a precursor of ß-endorphin, was quantified in peripheral blood cells, liver and spleen. ß-endorphin peptide was measured in the liver and spleen. RESULTS: Expression of proopiomelanocortin mRNA was detected in peripheral tissues after systemic administration of lipopolysaccharide. Lipopolysaccharide also induced ß-endorphin expression in the liver and spleen. CONCLUSION: Expression of proopiomelanocortin mRNA and ß-endorphin was detected in peripheral tissues after systemic administration of lipopolysaccharide. These results provide new evidence that peripheral endogenous opioids can be produced not only as a result of local inflammation but also by severe systemic stress such as endotoxic shock. Further study is required to clarify the role of peripheral ß-endorphin during endotoxic shock.

Massive ameloblastoma: A case report of difficult fiberoptic intubation.

INTRODUCTION: Intubation can sometimes be difficult in patients with lesions in the mouth floor. Ameloblastoma is a frequently encountered tumor of the maxillofacial area. An extensive lesion might occupy the floor of the mouth, prevent displacement of the tongue, limiting the space for inserting a laryngoscope blade and resulting in difficult intubation even with fiberoptic bronchoscopy. CASE PRESENTATION: A 66-year-old man (67 kg; 171 cm) with a mental swelling was diagnosed with ameloblastoma and scheduled for surgical resection. The tumor was extensive, occupying most of the anterior floor of the mouth. We were concerned about impossible direct laryngoscopy because the massive tumor in the floor of the mouth compressed the base of the tongue against the posterior wall of the pharynx, restricting the space for inserting the laryngoscope blade. Therefore, we planned to perform awake nasal fiberoptic intubation to secure the airway. Although the procedure was complicated by the massive tumor, successful intubation was achieved by hand-assisted alteration of the direction of the endotracheal tube (ETT) under direct laryngoscopy. DISCUSSION: Awake fiberoptic intubation was complicated by the tumor protrusion to deviate the ETT. Discovering of the ETT deviation by the insufficient blade insertion facilitated visualizing the vocal cords with the fiberoptic scope. CONCLUSION: Identification of ETT deviation even with insufficient blade insertion and hand-assisted alteration of the direction of the ETT might raise the chances of successful fiberoptic intubation. The anesthesiologist should be aware of the likelihood of failed fiberoptic intubation and plan for alternative approaches to secure the airway.