1. The composition of various colloids that are available commercially is shown in Table I(1). It may be seen that all the available colloids are "colloids in saline" solutions.

TABLE I

Characteristics of Various Colloids.

Mw (kDa)

69

35

450

200

40

Sodium  (mmol/L)

130-160

145

154

154

154

Potassium (mmol/L)

1

5.1

0

0

0

Duration of action (Hrs)

6

3-4

>8

6-8

3-4

Water binding
 (Ml H2O/g colloid)

18

41.7

20

30

37

2. In septic shock, infection triggers endogenous mediators, which in turn injure the capillary endothelium and other organs. Vascular injury leads to mal-distribution of circulation with vasodilatation and pooling of blood (arterial and venous) and capillary leaks leading to loss of intravascular fluid to interstitial space ("third spacing"). The major physiologic aberration, therefore, in septic shock is hypovolemia and reduced pre-load. Myocardial dysfunction is next important physiologic aberration, responsible for poor tissue perfusion. Vasoactive and inotropic drugs are used as soon as intravascular volume is restored. Many of our patients did receive inotropes. It should however, be appreciated that after completion of initial resuscitation the fluid leak from intravascular compartment to interstitial space (‘third-space loss’) does not stop immediately. Moreover, a significant proportion of administered fluid continues to move out of intravascular space. It has been shown that only about 20% of administered saline stays in intravascular compartment by the end of two hours(4). The capillary leak may take several hours, sometime days, before it is reversed. In such patients, therefore, the continuing management of intravascular volume requires replacement of ongoing’ ‘third space loss’. Usually, this is achieved by administration of maintenance fluids at a higher infusion rate but some patients need fluid bolus because of continuing rapid ‘third space loss’.