The total required amount CB should have been receiving for the past 4 hours should be:
Required quantity = (75 mL / hr) * 4 hr
Required quantity = 300 mL
The actual quantity CB received however is only:
Actual quantity = (45 mL / hr) * 4 hr
Actual quantity = 180 mL
Therefore the deficit is:
Deficit quantity = 300 mL – 180 mL
Deficit quantity = 120 mL
Since in a 1 liter (1000 mL) bag there is 40 mEq of KCl, therefore the needed extra mEq of KCl that CB has to receive now is:
Additional KCl = 120 mL * ( 40 mEq / 1000 mL)
Additional KCl = 4.8 mEq