Understanding Anesthesiology - The Global Regional Anesthesia ...

Assessment of Fluid Status
Fluid status is assessed by history, physical exam and
laboratory exam. Thorough history will reveal losses of
blood, urine, vomit, diarrhea and sweat. As well, the
patient is questioned regarding symptoms of hypovolemia,
such as thirst and dizziness.
On physical exam, vital signs, including any orthostatic
changes in vital signs, are measured. A decrease in
pulse pressure and decreased urine output are two of
the most reliable early signs of hypovolemia. Poor capillary
refill and cutaneous vasoconstriction indicate compromised
tissue perfusion. Severely depleted patients
may present in shock (Table 3).
Hemoglobin, sodium, urea and creatinine levels may
show the concentration effect which occurs in uncorrected
dehydration. When blood loss occurs, hemoglobin
and hematocrit levels remain unchanged until intravascular
volume has been restored with non-blood containing
solutions. Therefore, only after euvolemia has
been restored is the hemoglobin level a useful guide for
transfusion. Lactic acidosis is a late sign of impaired tissue
perfusion.
Table 3 Classification of hemorrhagic shock in a 70 kg person
BLOOD LOSS
(cc)
BLOOD LOSS
(%)
CLASS 1 CLASS 2 CLASS 3 CLASS 4
2000
40
PULSE RATE 140
BLOOD
PRESSURE
PULSE
PRESSURE
RESPIRATORY
RATE
URINE
OUTPUT
normal
orthostatic
drop
decreased
decreased
normal decreased decreased decreased
14-20 20-30 30-40 >40
>30 cc/hr 20-30 cc/hr