Which Goal for Fluid Therapy During Colorectal Surgery is Followed by the Best Outcome: Near Maximal Stroke Volume or Restricted Fluid Therapy

Background Hypovolemia can cause postoperative complications, circulatory collapse and death, regardless if the cause is blood loss or loss of other fluids. Therefore, doctors are giving fluid intravenously to patients undergoing surgery, and often in an amount larger than the measured losses. Recent studies, however, have shown that also fluid overload plays a part in complication development after surgery (1-3). It is therefore important to find the optimal fluid treatment for surgical patients.

In Denmark, approximately 3500 patients are undergoing surgery every year for colorectal cancer, and in addition, operations are performed for benign diseases. However, the complication rate after colorectal surgery remains high (approximately 30%).

Disagreement about which fluid treatment is optimal exist between three "schools for fluid therapy":

1. "Standard fluid therapy" which in addition to replacing external fluid loss (blood loss, urine and evaporation) include fluid to replace a "third space loss" and fluid to counteract low blood pressure (4-5). Standard therapy is poorly defined and differ between hospitals. It cause a bodyweight increase by 3-6 kilo (6-7).
2. "Goal-directed fluid therapy", where volume is given in a bolus injection of a colloid (typically hydroxyethyl starch (HES)) in order to keep the patient's stroke volume (SV) at a near maximum level (1). The heart is brought close to maximum performance. In theory, hypovolemia is prevented and oxygen supply to the tissues increased. In the studies available, HES is given on top of "standard therapy" and "Goal-directed fluid therapy" therefore result in a weight gain not measured in the available studies.
3. "Restrictive fluid therapy", replace only measurable fluid losses and strive to maintain the patient's normal (preoperative) body weight. The hypothesis is that excess fluid cause interstitial edema which may be harmful to the healing of tissue and function. (2,3,8).

"Standard fluid therapy" is meaningful if a benefit exists in giving fluid to a possible third space loss and treat the vasodilatation caused by epidural analgesia by volume. However, a recent critical review of the literature poses serious doubts about the existence of a third space loss (9), and no beneficial effect of volume treatment of the vasodilatation caused by epidural analgesia been shown.