Post-Operative Fluid Management

Post-op Fluids

Written by Dr Hyerim Su

Daily requirements of electrolytes and water 

• Water – 25mL/kg/day 
• Sodium – 1.0mmol/kg/day 
• Potassium – 1.0mmol/kg/day 
• Glucose 50g/day 

Table 1. Composition of intravenous fluids

• Dextrose is a hypotonic solution as the dextrose is metabolised, leaving only free water. Only 7% of the fluid stays in the intravascular component. 
• 0.9% saline equilibrates in the intravascular and interstitial spaces, with 25% staying in the intravascular space. It is useful in resuscitation, but using it as the sole maintenance fluid can result in hyperchloremic acidosis. 
• Hartmann’s is the most physiological fluid out of the three as it contains more electrolytes. A common misconception is that Hartmann’s causes lactic acidosis, but Hartmann’s solution contains lactate (the conjugate base), thus is actually an alkalising solution. 

References

https://teachmesurgery.com/perioperative/preoperative/intravenous-fluid-composition/