Colloid Vs Crystalloid in Critically Ill

Mild blood loss (15%): fluid shifts from interstitial to vascular space. However this effect is predominant only w/ mild blood loss. This might argue for crystalloid resuscitation to replete the interstitial volume, but in the case of mild blood loss, no volume rescuscitation is necessary because the body can compensate.

If blood loss is more severe, we need to make sure the vascular volume is maintained. This would argue for colloid. One could use crystalloid, but would need 3x the volume of colloid.

Survival: colloid does not confer a higher survival rate.

Expense: accounting for the fact that e.g. 250 ml of colloid expands volume to the same degree of 1000 ml of crystalloid, colloid is still 3-6 times more expensive.

Edema: seen in both. Crystalloid moves mainly into interstitium. With colloid, do not forget that 50% of the albumin is in the interstitium too, so infused albumin does eventually get there. The albumin egress is worsened in the critically ill with increased capillary permeability.