Chapter 76 - Burns Flashcards
how do you calculate the total body surface area in burns?
Rule of 9’s
Head/neck - 9%
RUE - 9%
LUE - 9%
RLE - 18%
LLE - 18%
Front of body - 18%
Back of body - 18%
genitals - 1 %
What are the pathophysiologic effects of major burns on cardiac, resp, heme/coagulation, renal, immune, and metabolism system?
Burns - associated with systemic release of inflammatory mediators: histamine, bradykinin, vasoactive amines, and interleukins –> affect all systems.
1) Cardiac
- Early - hypovolemic shock
- inflam mediators -> inc capillary permeability -> third space -> intravascular depletion
- CO decreased, SVR increased
- 2/2 circulating mediators
- Late (24-48hr later) - SIRS
- CO increased, SVR decreased
2) Lungs
- direct injury - upper airway swelling, smoke inhalation injury
- indirect injury - pulm edema & pulm HTN 2/2 leaky capillary membrane in lungs
3) Kidneys
* AKI 2/2 decrease renal blood flow 2/2 hypovolemia and increase R-A-A = systemic vasoconstriction
4) heme/coag
* DIC (activated by inflamm mediators)
5) hypermetabolism
* increase metabolic rate, increase O2 utilization, increase Co2 production, impaired thermoregulation
What fluid would you use and how much would you want to transfuse for an adult burn patient? (parkland formula)
- LR = fluid of choice since it most closely resembles human plasma
Parkland Formula
- 4 ml / kg / % TBSA burned
- half of fluid administered in first 8 hours
- remaining half given over next 16 hours
for initial resucitation, would you use colloid or crystalloid?
- burn injury is associated with large inflammatory mediator release, causing permeable capillary membranes –> edema and third spacing
- Do NOT give colloids in first 24 hours, not more effective in restoring volume than crystalloids in this time frame
What is a possible complication of fluid resuscitation in a burn patient?
- burn patients are intravascularly depleted 2/2 third space losses and evaporation of fluids, as well as bleeding.
- they have leaky capillaries from systemic inflammatory mediator release
- fluids can worsen interstital edema:
- increase abdominal compart pressure
- increase orbtial pressure
- increase extremitiy compartment pressure
How do you diagnose smoke inhalation injury?
Clinical features + bronch
Clinical features
- facial burn
- singed nasal hairs
- carbonaceous sputum
- hoarseness
- respiratory distress
FOB = Gold Standard
what are the anesthestic concerns with smoke inhalation injury, how do you manage it?
Smoke
- casues swelling of upper airway, can quickly lead to airway obstruction
- damages respiratory tract and alveoli –> bronchospasm, edema, mucous membrane ulceration
Mgmt
- goal - maintain airway patency, maximize gas exchange
- Secure Airway - protection and/or resp failure
-
Mech Vent
- lungs are damaged from smoke injury –> minimize barotrauma using ARDS protocol
- consider permissive hypercapnia to minimize airway pressure
- PaO2 > 60 is acceptable -> reduce O2 toxicity
- supportive care
Pathophys of CO?
CO Pathophys
- higher affinity for HgB than O2
- 1) displaces O2 from HgB
- decrease oxygen-carrying capacity of HgB
- 2) shifts O2-HgB dissociation curve to left
- reduces unloading of O2 to tissues
- 3) binds to cytochrome oxidase and impairs activity of intracellular enzymes
Dx and TX of CO poisioning?
DX:
- measure carboxyhemoglobin levels
-
cooximeter - measure oxyhemo and carboxy hemo
- normal pulse ox cannot differentiate betwen oxy and carboxy -> normal SaO2
Tx:
- supplemental O2
- 100% FiO2 = eliminates CO 60-90 min
- hyperbaric O2 = eliminates CO even faster
Discuss Cyanide toxicity pathophys and tx
CN toxicity
- inhibits cytochrome oxidase in mitochondria –> prevents them from using O2 –> prevents ability to generate ATP.
- Metabolic Acidosis and increased SVO2
Tx:
- supplemental oxygen
- hemodynamic support
-
give meds that bind to cyanide and eliminate from body (meds that compete for cyanide to prevent it from binding to cytochrome oxidase)
- sodium thiosulfate
- amyl nitrate
- cyanocobalamin
patient comes with severe burn 5 hours ago, how would you assess his airway and how would you intubate this patient? How would you intubate a peds burn patient?
1) H&P
- emergent intubation required?
- Respiratory distress, stridor, hypoxemia/hypercarbia
- If yes -> RSI
- airway exam, pre-existing airway abnormalities, prior intubation history, history of head/neck surgery
- pre-op FOB of nasopharyngeal airway to look at structures, look for edema and impending airway obstruction
Airway
- no airway abnormalitiy –> RSI
- abnormal airway or stable upper airway obstruction –> Awake FOB
- Peds pts are not cooperative –> inhaled induction with nonpungent voltaile - sevo. intubate with DL, glidescope, asleep FOB, etc..
Patient had a severe burn injury 5 hours ago, you plan to do RSI, would you use succinylcholine?
- Burn injuries are associated with upregulation of extrajunctional nicotinic cholinergic receptors at NMJ
- SUX places pt at risk for hyperkalemic cardiac arrest
-
**Safe to use SUX within first 24 hours after burn injury**
- AVOID SUX THEREAFTER
A patient with a burn injury 4 days ago comes to the OR for exicsion and grafting. Explain the surgical management of burns and appropiate timing of surgery.
Overview
- burns produce eschar formation –> nidus for inflammation and infection –> leads to sepsis
Timing of surgery
- Early exicision and grafting (2-5 days after burn injury) –> shown benefits in terms of survival, incidence of sepsis, length of hospitalization
- day 1-2 fluid resucictate and optimze for surgery
Surgery
- excision of eschar until healthy wound bed developos.
- autograft from donor site used to cover wound
- major bleeding associated with autograft sites and exicision of eschar.
patient comes to your OR after suffering burn injury 4 days ago. He is fluid resusciated pre-operatively in the unit, is intubated as well. His burn wound is 40% of total body surface area (TBSA). What are your anesthetic considerations?
1) Airway
* if patient is intubated, how was the intubation performed
2) Muscle relaxants
- burn associated with upreg of extrajunc AcH recep at NMJ
- avoid SUX 24 hours after burn injury
- use NMBD –> large doses required due to decreased sensitivity from inc of extrajunc AcH recep
3) Blood Loss
- rapid and massive blood loss
- major fluid shifts associated with large burn surgery
- blood products readily available, constant commun with surgical team
4) Hypothermia
- skin barrier is destroyed –> lose heat and water
- hypothermia –> negative effects such as coagulation, inc hypermetabolism, inc O2 consumption
- Inc room temp, monitor core temp, IV fluid warmer, forced air warming devices
