Understanding Anesthesiology - The Global Regional Anesthesia ...

SECTION 2
Fluid Management
In This Section
1. Fluid Requirements
2. Assessment of Fluid Status
3. Vascular Access
4. Types of Fluid
The goal of fluid management is the maintenance
or restoration of adequate organ perfusion and
tissue oxygenation. The ultimate consequence of
inadequate fluid management is hypovolemic
shock.
Fluid Requirements
Peri-operative fluid management must take into
account the pre-operative deficit, ongoing maintenance
requirements and intra-operative losses
(blood loss, third space loss).
Pre-operative Deficit: The pre-operative fluid
deficit equals basal fluid requirement (hourly
maintenance x hours fasting) plus other losses
that may have occurred during the pre-operative
period.
Maintenance fluid requirements correlate best
with lean body mass and body surface area. To
calculate maintenance, use the “4/2/1 rule”:
First 10 kilograms (i.e. 0-10 kg):!
Next 10 kilograms (i.e. 11-20 kg):!
4 cc/kg/hr
2 cc/kg/hr
All remaining kilograms over 20 kg:! 1 cc/kg/hr
For example, a 60 kg woman fasting for 8 hours:
! 10 kg x 4 cc/kg/hr ! = 40 cc/hr
! 10 kg x 2 cc/kg/hr ! = 20 cc/hr
+ ! 40 kg x 1 cc/kg/hr ! = 40 cc/hr!
! ! ! ! ! = 100 cc/hr x 8 hr
! ! ! ! ! = 800 cc
Therefore, the pre-operative deficit (excluding
other losses) is 800 cc.
“Other losses” (including fluid lost through
sweating, vomiting, diarrhea and nasogastric
drainage) are more difficult to estimate. In the
febrile patient, maintenance requirements are increased
by 10% per degree Celsius elevation in
temperature.
As a rule, half of the deficit should be corrected
prior to induction and the remainder replaced
intra-operatively. However, if the pre-operative
deficit is greater than 50% of the estimated blood
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