This topic foe randomized prospective study.Detection of elderly patients with lunmbar spinal postoperative inflammatory substances in the blood and drainage of liquid level ,clear whether low-dose dexamethasone can inhibit the inflammation, the observation of elderly patients with lumbar spinal postoperative drainage star, to explor whether low-dose dexamthasone can reduce postoperative incision drainage, thus impove the postoprative drainage tube pull rate within three days, which in turn reduce because of the place a retrograde infection caused by drainage tube.

A total of 100 patients undergoing posterior lumbar disc fusion were randomly divided into control group (group C,n=50) and dexamethasone group (group D,n=50). Group D was given 0.15mg/kg dexamethasone (2ml) intravenously after anesthesia induction. Group C was also intravenously injected with 2ml normal saline after anesthesia induction.On this basis, monitor the main results and secondary results

Inclusion Criteria:

• Adult patients ≥65years of age
• American Society of Anesthesiologists (ASA) physical status 2-4
• Elective or expedited non-cardiac surgery of at least 2 hours dura- tion under general anaesthesia
• Requiring a hospital stay of at least one postoperative night
• A surgical skin incision >5 cm in length or multiple incisions with a total incision length of >5 cm

Exclusion Criteria:·

• Poorly controlled diabetes (HbA1c>9.0%)
• Endovascular procedure with a small (<5 cm length) skin incision Ophthalmic surgery
• Planned dexamethasone (or other corticosteroid) therapy (eg, history of intractable PONV, maxillofacial surgery, intracranial neurosurgery)
• Recent (<2 weeks since end of treatment) infective episode requir- ing treatment with antibiotics
• Chronic antibiotic therapy (eg, for bronchiectasis, cystic fibrosis etc)