Sau khi đầu gối phẫu thuật, chân có thể được nâng lên hông (35 ◦ bẻ gập lại) và giữ thẳng đầu gối, đầu gối (70-90 ◦) và hông (90 ◦) có thể được uốn cong. Cả hai biện pháp này dường như để giảm mất máu đáng kể [7]. | Anesthesia More than Sleeping 193 Table Positions proposed to reduce blood loss in spinal surgery. Positions without frames Positions with frames Use of chest rolls Canadian frame Hastings Kneeling position 1969 Relton-Hall frame 1969 Ecker 1949 Mohammedan praying Andrews frame position Lipton 1950 Knee-chest position Wilson bank Tarlov 1967 Tuck position Jackson table Wayne 1967 Cloward surgical saddle Heffington frame Remarks in parentheses Person who was attributed to have it described first. pressure should be taken from the abdomen and especially the vena cava. This can be done by supporting the hips and the shoulders with pillows or other devices frames Table . The blood can nowfollow gravityand collects in the abdomen rather than in the surgical area 1 . Blood loss decreases 5 . Intraoperative positioning may also serve purposes that are only tangentially associated with reducing blood loss. Liver resection maybe performed in 15 head-down position. This may seem contrary to the principle of positioning patients with elevated surgical fields. However when liver surgery is performed in controlled hypotension tilting the head down may improve renal perfusion and aid in maintaining a marginal urine output during surgery 6 . Thus this position may allow for reduction of blood loss by means of the reduced systemic blood pressure without unduly compromising renal perfusion. Using certain positions may indeed reduce blood loss. However care must be taken that nerves are not injured eyes not unduly compressed and joints not overly flexed being especially detrimental for patients with joint replacement or joint diseases. As well an overly flexed position may cause vascular compression and myolysis with resulting renal failure. Therefore care must be taken that the chosen position is attained carefully and points ofpres-sure must be padded. The patient s posture not only influences intraoperative blood loss but may also be important in the postoperative .
