Section
3a
Systematic
Hemodynamic Changes
Decreased oxygen
delivery to tissues is the primary problem during
this period. Cardiovascular instability arises from
the loss of intra-vascular fluid (not red cells).
The rate of loss of plasma volume is the greatest
during the first 4 to 6 hours, decreasing
substantially by 18 to 24 hours. The degree of
hypovolemia is relative to burn size (see rule of
nines).
Central
venous pressure and pulmonary artery wedge pressure
usually remain low even when cardiac output and
perfusion are adequate, for vasculature in a burn
patient can be perceived as a large garden hose in
which holes are punched in a proximal segment (burn)
of the hose. Changes in upstream pressure lead to a
change in the rate of leak through the holes,
whereas downstream pressure and flow remains
relatively constant. An overzealous attempt at
restoring blood volume over and above that necessary
for adequate perfusion can markedly accentuate
edema-related complications, because fluid and
protein losses in burn tissue are markedly
aggravated by any increase in venous pressure.
|
Cardiovascular
Changes |
- Decreased blood volume
-
Decreased oxygen delivery
-
Increased pulse rate
-
Normal to low blood pressure
-
Increased systematic vascular permeability
-
Edema related complications
|
Hematologic Changes Diagram
Rate of Infusion
Rate of
fluid administration is dependent on the rate of
loss, the latter being assessed by the perfusion
monitors. An initial rate for the first 24 hours can be
estimated using the size of the burn (combined
second and third degree) relative to body surface
area and body weight:
|
Adult
formula: Fluid first 24 hours = 4cc x % total body
surface x body weight (one
half in first 8 hours)
For
children, especially under 6 years of age,
replacement must also include normal daily
requirements, not considered in the adult formula.
Children’s
formula: Fluid first 24 hours = 5000 ml/m /% TBSA +
2000 ml/m /BSA of 5% DSW in lactated
ringers (one half in first 8 hours) |
|
Rate of Infusion
- begin using formula
- if shock present give bolus of fluid
until perfusion restored
- then use constant rate, adjusting
as needed
- after 10 to 12 hrs. gradually
decrease infusion rate to avoid excess edema
while maintaining perfusion
|
Assess
according to a Pediatric Burn Formula Plus Patient
Response
ASSESSING BURN SIZE AS % OF TOTAL BODY SURFACE
(Second and Third Degree combined)
Intravenous
Access
A
peripheral vein catheter through nonburn tissue is
the route preferred for fluid administration. A
central line or pulmonary artery line is only
occasionally needed to monitor the patient during
the initial resuscitation period and is removed as
soon as it is no longer needed. The possibilities
for intravenous access are:
|
Choices
For Access
- First
choice: Peripheral vein; nonburn area
- Second
choice: Central venin; nonburn area
- Third
choice: Peripheral vein; burn area
- Worst choice:
Central vein; burn area
|
Monitoring
lines are required primarily for the elderly patient
or the patient with severe heart disease. A high
complication rate has been reported with central
catheters in burn patients as a result of infection.
  
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