Pre-optimisation of surgical patients.

There have been a number of publications looking at the pre-operative optimisation of oxygen delivery for high risk patients. They are based on studies showing that high-risk patients surviving major surgery achieved consistently higher postoperatrive oxygen delivery and cardiac index compared with non-survivors.

Shoemaker showed the following values to be associated with survival:
Cardiac Idex (CI)                    4.5 l/min/m2
Oxygen delivery (DO2)            600 ml/min/m2
Oxygen consumption (VO2)     170 ml/min/m2

Shoemaker et al. in 1987 and Boyd et al. in 1993 showed that producing supranormal values of oxygen delivery(>600 ml/min/m2) resulted in a reduction in pot-operative mortality in high risk surgical patients.

A paper in Critical Care Medicine in 2000 (prospective, randomized controlled trial of 412 patients undergoing major abdominal surgery in 13 hospitals from 6 European countries) compared the effects on morbidity/mortality of dopexamine infusion or placebo on fluid resuscitated patients. Patients were taken to ICU pre-operatively, invasive monitoring inserted and fluids given until set criteria met. Randomization to dopexamine 0.5 mcg/kg/min, 2 mcg/kg/min or placebo followed. There was no statistically significant difference in 28-day mortality in the three groups, although the authors speculated a trend towards lower mortality in the low-dose dopexamine group.

Consensus meeting: management of the high-risk surgical patient, April 2000
-Increasing global oxygen delivery in high risk patients significantly reduces mortality.
-In patients with significant IHD, care needs to be taken to minimize oxygen demand.
-The earlier the intervention, the better the outcome.
-Strategy should be as defined by shoemaker's criteria for CI, DO2, and VO2.
-Low dose dopexamine may have additional benefits.

A meta-analysis of fluid optimization by Kern and Shoemaker in Critical Care Medicine in 2002 concluded that patients at high risk (predicted mortality >20%) would benefit from fluid optimization but not those with a predicted mortality <15%.

On the flip side of the coin, excessive fluid resuscitation has been shown to worsen outcome in abdominal surgery (Brandstrup et al. 2003)