Postoperative pulmonary complications draws anesthetists' attention as it can be associated with prolonged postoperative hospital stays, increased hospitalization expense, retardeding postoperative recovery and increased hospital mortality. In recent years, lung protective ventilation strategy has been applied during operation under general anesthesia, and current protective lung ventilation strategies generally involve some degree of hypercapnia. Increasing evidences support that hypercapnia is well tolerated and hypercapnia can attenuate the inflammatory response during lung injury, which would assign it a specific role within lung protection strategies during mechanical ventilation. In this paper, we summarize the influence of permissive hypercapnia on the body and the research development in the application of permissive hypercapnia in general anesthesia.

Objective: To observe the analgesic and sedative effect of epidural dexmedetomidine injection in patients undergoing transurethral resection of prostate (TURP) and its effect on postoperative cognitive function. Methods: A total of 60 patients undergoing TURP under combined spinal-epidural anesthesia (CSEA) were randomly divided into dexmedetomidine group and normal saline group. Patients in the dexmedetomidine group were given 0.1 μg/kg of dexmedetomidine injection after epidural anesthesia, and 0.9 μg/kg of dexmedetomidine was added into epidural analgesia pump after operation; patients in the normal saline group were given the same dose of normal saline. The vital signs, visual analogue scale (VAS) and Ramsay sedation score of patients in the two groups at different time points[before intervention (T₀), after intervention for 15 min (T₁), after intervention for 30 min (T₂), after intervention for 45 min (T₃), after intervention for 60 min (T₄), after surgery for 12 h (T₅), after surgery for 36 h (T₆)] were recorded. The mini mental state examination (MMSE) of patients in the two groups 1 d before operation and 3 d after operation were recorded. Results: Compared with normal saline group, the VAS scores of patients in dexmedetomidine group were significantly lower at T₁-T₆ (P < 0.05), and the Ramsay scores were significantly higher (P < 0.05). There was no significant difference of MMSE total score [25.00(23.50, 27.50) scores] in the patients of dexmedetomidine group 3 d after operation but the memory ability score [4.00(3.00, 5.00) scores] was significantly decreased (P < 0.05), and the language ability score [9.00(8.00, 9.00) scores] was significantly increased (P < 0.05). There was no significant difference in MMSE score between the two groups in comparison with that 1 d before operation. Conclusions Epidural dexmedetomidine injection (1 μg/kg) enhancesd the analgesic effect of ropivacaine and producesd sedative effect. Although there was is no significant effect on the overall cognitive function, it might have some effect on memory function.