To evaluate the effects of early oral carbohydrates after TKA on nutritional status, comfort and safety in elderly patients.

Most of the current clinical studies of oral carbohydrate effects on postoperative recovery focus on the preoperative oral phase, and only a few small samples have shown that postoperative oral carbohydrate improves postoperative comfort. Therefore, further systematic studies on the effects of early postoperative oral carbohydrates on postoperative recovery remain lacking.

This clinical study uses a single center, randomized, single-blind, parallel controlled trial design divided into screening, treatment and follow-up period.

Actively control blood pressure, blood pressure and blood sugar, correct anemia and hypoproteinemia, and increase protein intake before surgery. The dietary plan was informed by the ward nurse: all patients were fasted with solid food 6 hours before surgery and took 200 milliliters of carbohydrates orally 2-3 hours before surgery.

The venous access was open after home invasion and was routinely monitored electrocardiogram (ECG), non-invasive blood pressure (NBP) ，oxygen saturation (SpO2) ，bispectral index (BIS). Parecoxib 40 milligrams of analgesia was given intravenously at 30 minutes before the start of the procedure. Adductor canal block (ACB) and Infiltration between popliteal artery and capsule of knee (IPACK) block were performed on the lower limbs of the surgical side using an ultrasound high-frequency line array probe before induction of the general anesthesia procedure.

Anesthesia induction: after static injection of Midazolam 0.03 milligrams / kilogram, Propofol 2 milligrams / kilogram， Sufentanyl 0.4 milligrams / kilogram, Cisatracurium 0.2 milligrams / kilogram. The tracheal tube was inserted after 3minutes and mechanical controlled ventilation was performed mechanical controlled ventilation, fraction of inspired oxygen（FiO2） 40%, oxygen flow 2 liters/ minutes, minute ventilation 7 milliliters / kilogram, respiratory rate（RR）12 times/ inspiration-to-expiratory ratio（I: E）1:2, maintain partial pressure of carbon dioxide in end expiratory gas （PETCO2） 35-40 millimeters of mercury（mmHg）. Anesthesia maintenance: intravenous propofol 4~7 milligrams / kilogram/ hour, remifentanil 0.3-0.5micrograms /kilogram/ hour, maintain BIS 40~60. A restrictive fluid management strategy was adopted, with 6ml/ kg·h supplemented with physiological needs, blood loss was supplemented with hydroxyethyl starch fluid, and concentrated red blood cells were infused at hemoglobin (Hb) <80 grams / litre to maintain patient blood pressure and heart rate fluctuations less than ±20% of the basal value. Dexamethasone 5mg and Tropisetron 2mg for prophylactic antiemesis were given intravenously at 30min before the end of the surgery. All patients used hydromorphone patient-controlled intravenous analgesia（PCIA ） pump for continuous: 1ml / h, automatic control: 5ml, locking: 10min, limit: 35ml / h, adjust parameters according to the pain.

Internal post anesthesia care unit （PACU） management: Patients will randomly enter the PACU into two study groups: early carbohydrate feeding group (EOF group) and conventional feeding group (control group). Routine feeding group (Group C): Patients in group C were observed with 60min of abnormal vital signs after extubation, and returned to the ward for fasting and fasting for at least 6 h, and began to eat gradually through the mouth after anal exhaust. Early carbohydrate feeding group (EOF group): The EOF group drank 10.5% of 5 ml/kg body weight (100ml containing 12.5g maltodextrin, fructose and glucose) after extubation in the resuscitation room. PACU management: Patients will randomly enter the PACU into two study groups: early carbohydrate feeding group (EOF group) and conventional feeding group (control group). Routine feeding group (Group C): Patients in group C were observed with 60min of abnormal vital signs after extubation, and returned to the ward for fasting and fasting for at least 6 h, and began to eat gradually through the mouth after anal exhaust. Early carbohydrate feeding group (EOF group): The EOF group drank 10.5% of 5 ml/kg body weight (100ml containing 12.5g maltodextrin, fructose and glucose) after extubation in the resuscitation room.

To evaluate the drinking criteria for patients in the EOF group: Steward wake score of 6 and wake level 3, take 5 ml/kg body weight of 12.5% carbohydrate (100ml containing 12.5g maltodextrin, fructose, and glucose) according to the patient's consent. The process of drinking carbohydrates was to take 30ml orally first. After observing the swallowing without abnormality, the patient was ordered to drink the remaining drinks within 2h. After the patient returns to the ward, the liquid diet is gradually excessive to the normal diet. When the patient was able to tolerate the normal diet, v.

1. Steward score: Awakening degree: 0-no response to stimulus; 1-some response to stimulus; 2-full awake.(2) Respiratory tract patency degree: 0 points-the patient's respiratory tract needs support; 1 points-the patient's respiratory tract can maintain patency without support; 2 points-the patient can cough according to the doctor's guidance.(3) Body activity degree: 1 points-the patient's limb has no activity; 2 points-the patient's limb has an unconscious activity; 3 points-the patient's limb can carry out conscious activities
2. Wakefulness classification according to the patient's consciousness performance: Level 0: the patient is completely asleep, Call without any response; Level 1: The patient is falling asleep, However, head and neck movement, eye opening or limb movement when breathing; level 2: the patient is awake, Have the same performance as level 1, At the same time can also open the mouth, stretch the tongue; Level 3: The patient is awake, Have the same performance as level 2, At the same time can also clearly say their own name, age and other information; Level 4: The patient is awake, Have the same performance as level 3, It can also accurately identify the surrounding environment, And tell you exactly where you are.
3. In addition to receiving different feeding treatment programs in the PACU, the two groups received the same care and diet program formulated by the same care group.

Record: Patients had fasting serum prealbumin, retinol-binding protein levels, and insulin resistance index on the same day, 1day and 3 days after surgery.

Record: 2 hours, 6 hours and 8 hours postoperative digital scores; bloating, hypoxemia and reflux aspiration occurred 24 hours after surgery.

Record: length of hospitalization, first anal exhaust time, first ambulation time, nausea and vomiting, and patient satisfaction.

Inclusion Criteria:

• Patients undergoing elective knee replacement surgery.
• The patient gave informed consent.
• Age ≥65 years, Sex is not limited
• American Society of Anesthesiologists (ASA)Ⅰ~Ⅲ level
• Body Mass Index (BMI)18~28kg/m2

Exclusion Criteria:

• Preoperative gastric emptying disorders, such as gastroesophageal reflux or previous surgery.
• Diabetes mellitus, severe renal insufficiency, or other severe metabolic diseases.
• History of motion sickness.
• Mental disorders, alcoholism, or a history of substance abuse.
• Patients with abnormal swallowing function.
• Maltodextrin, fructose allergy or intolerance.
• Surgery time was greater than 3 hours.