Plastic, Reconstructive, and Burns surgery Flashcards
In a patient who sustained significant burn injury, the blood concentration of propofol is:
a) Increased due to reduced cardiac output
b) Increased due to dehydration and reduced circulating volume
c) Reduced due to increased volume of distribution and clearance
d) Increased due to reduced renal clearance
e) Reduced due to increased inflammatory cytokines
REPEAT
c) Reduced due to increased volume of distribution and clearance
2010 Paper on major burns
The pharmacokinetic characteristics of a propofol bolus administered in patients with major burns were enhanced clearance and expanded volume of distribution.
BURN and WT were the important covariates. For sedation or anesthesia induction, a higher than recommended dose of propofol may be required to maintain therapeutic plasma drug concentrations in patients with severe burns.
Vigilance regarding the burned individual and careful titration of hypnotics to the desired effect cannot be overemphasized.
https://pubmed.ncbi.nlm.nih.gov/20510522/
A 30-year-old has had a free-flap operation of eight hours duration. They received an intraoperative remifentanil infusion and 10 mg morphine 30 minutes before the end of the operation. During recovery their pain score increased from 6/10 on arrival to 9/10 despite a further 10 mg of intravenous morphine. The most likely diagnosis is:
a. Acute behavioural change
b. OIH
c. Inadequate analgesia
D. Physical dependence
Nikki:
B)
Opioid induced hyperalgesia;
The key features are long case with Remi running, as well as increased pain following additional opioids.
https://associationofanaesthetists-publications.onlinelibrary.wiley.com/doi/full/10.1111/anae.13602
Kate A 25-year-old sustains a burn to 30% of their total body surface area. A physiological change expected within the first 24 hours is:
a) Increased CI
b) Decreased SVR
c) Increased PVR
d) Increased hepatic blood Flow
REPEAT
C) Increased PVR
Initial - may lead to burns shock
Increased SVR (by 200%)
Increased PVR
Increased capillary permeability- loss of intravascular volume/Increased interstitial oedema
Reduced CO
SIRS
By day 5 hyperdynamic circulation
Tachycardia
Increased CO (remains for at least 2 years maybe longer)
20.1 A 25-year-old man suffers a 30% total body surface area burn. A physiological change expected within the first 24 hours is
a) Increase PVR
b) Decreased SVR
c) Increased cardiac index
d) Increased stroke volume
a) Increase PVR
UTD:
Low cardiac output “ebb,” phase (resuscitative phase) –
In the first 48 hours after a major burn, cardiac output (CO) is reduced up to 60 percent from baseline due to:
1. hypovolemia from permeability-induced plasma loss
2. reduced myocardial response to catecholamines
3. increased systemic vascular resistance due to elevated vasopressin levels
4. depressed myocardial contractility
5. possible myocardial ischemia due to decreased coronary blood flow
The large volumes that these patients require can sometimes result in over-resuscitation, leading to pulmonary edema and right heart failure.
High cardiac output “flow,” phase (recovery phase)
During the recovery phase 72 to 96 hours postburn, hyperdynamic and hypermetabolic responses result in:
1. increased CO
2. Tachycardia
3. increased myocardial oxygen consumption
4. decreased systemic vascular resistance
Elevation of catecholamines in major burns produces:
1. hyperdynamic circulation
2. augments energy expenditure
3. romotes protein catabolism in skeletal muscle.
Nonselective beta blocker therapy is sometimes used to block catecholamine receptors, treat cardiac dysfunction, and modulate the hyperdynamic response during this phase
21.1 A 100 kg 32-year-old male presents two hours after suffering a 30% total body surface area electrical burn. He has had no resuscitation fluids. The infusion rate of isotonic crystalloid resuscitation fluid required for this man for the next six hours is
a. 500 ml/hr
b. 750 ml/hr
c. 1000 ml/hr
d. 1200 ml/hr
c. 1000 ml/hr
30% x 100kg x 4ml= 12000ml
50% in first 8hrs = 6000ml
pt presents 2hrs late = 6000ml/6hrs = 1000ml/hr
or
30% x 100kg x 3ml= 9000ml
50% in 1st 8 hrs= 4500ml
pt presents 2hrs late= 4500ml/6hrs= 750ml/hr
750mls/hr
EMSB recommends 3ml/kg, BJA recommends 4ml/kg
-> go with 4ml/kg because electrical burn and more likely to require increased fluids anyway
21.1 A 40-year-old man suffers a hydrofluoric acid burn to 60% of his total body surface area in an industrial accident. An expected electrolyte disturbance is:
a. Hypocalcemia
b. Hyponatremia
c. Hypophosphatemia
d. Hypomagnesemia
hypoCALCEMIA
Hydrofluoric acid: highly corrosive inorganic aacid of element fluorine
- used in glass etching, electronics industry and cleaning solutions for metals, stone and marble
- dilute solutions can rapidly penetrate the skin and exposure of even a small area can be fatal (2%TBSA)
Fluoride ions bind with calcium and magnesium ions in the tissues
-> significant hypocalcaemia and hypomagnesaemia
-> Hyperkalaemia may also be seen
Direct cardiotoxic effects of fluoride ions can lead to cardiac arrhythmias that are difficult to treat
21.1 A 25-year-old man suffers a 30% total body surface area burn. A cardiovascular physiological change expected within the first 24 hours is
a. Decreased PVR
b. Increased SVR
c. Decreased SVR
d. Reduced PA pressure
e. Increased hepatic blood flow
increased SVR
EMSB handbook
CO is reduced after Burn injury 2ry to:
- myocardial depressant mediators
- decreased blood volume
- reduced venous return
- increased pulmonary and systemic vascular resistance due to increased levels of catecholamines
In the first 24hrs reduced cardiac output persists even after restoration of blood volume
Between 24-48hrs post burn a hyperdynamic state develops with reduced peripheral resistance, increased oxygen consumption and increased cardiac output
22.2 In a burns patient, the blood concentration of propofol is
a) Increased due to reduced cardiac output
b) Increased due to dehydration and reduced circulating volume
c) Reduced due to increased volume of distribution and clearance
d) Increased due to reduced renal clearance
e) Reduced due to increased inflammatory cytokines
c) Reduced due to increased volume of distribution and clearance
2010 Paper on major burns
The pharmacokinetic characteristics of a propofol bolus administered in patients with major burns were enhanced clearance and expanded volume of distribution.
BURN and WT were the important covariates. For sedation or anesthesia induction, a higher than recommended dose of propofol may be required to maintain therapeutic plasma drug concentrations in patients with severe burns.
Vigilance regarding the burned individual and careful titration of hypnotics to the desired effect cannot be overemphasized.
https://pubmed.ncbi.nlm.nih.gov/20510522/
23.1 Burns sustained from electrocardiography equipment during magnetic resonance imaging (MRI) scanning are minimised by
a. Low impedance ECG leads
b. Wet skin
c. Shaved skin
d. Looped leads
e. Ensure leads securely attached
e) ensure leads securely attached
https://journals.lww.com/nursing/Citation/2006/11000/Cables_and_electrodes_can_burn_patients_during_MRI.12.aspx#:~:text=The%20radiofrequency%20fields%20that%20occur,enough%20to%20require%20plastic%20surgery.
https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.107.187256#d1e281
20.2 A 100 kg twenty-five year old male presents 2 hours after suffering a 30% Total Body Surface Area electrical burn. He has had no resuscitation fluids. The infusion rate of isotonic crystalloid resuscitation fluid required for this man for the next 6 hours is
a) 500 ml/hr
b) 750 ml/hr
c) 1000 ml/hr
d) 1200 ml/hr
e) 1500ml/hr
c) 1000 ml/hr
4ml/kg/hr x 30%TBSA x 100kg = 12,000mL
1/2 within the first 8hrs, remainder over the next 16 hours (starting at 6 hour mark in this stem so beware)
6,000mL/6hrs = 1000 mL/hr which is the rate you would run it over the next 6 hours.
20.2 A 40 year old man suffers a hydrofluoric acid burn to 60% of his total body surface area in an industrial accident. An expected electrolyte disturbance is
a. Hypokalaemia
b. Hyponatremia
c. Hypophosphatemia
d. Hypomagnesemia
e. Hypocalcemia
e. Hypocalcemia
UTD:
> HF penetrates quickly through the epidermal layer into the dermis and deeper.
Fluoride ions complex with calcium and magnesium, which can lead to hypocalcemia and hypomagnesemia.
These electrolyte abnormalities and the direct cardiotoxic effects of fluoride ions contribute to the development of cardiac arrhythmias, which are the primary cause of death in HF burns.
Hypocalcemia may stimulate an efflux of potassium ions from cells resulting in hyperkalemia, and predisposing to cardiotoxicity.
QTc interval prolongation, due to hypokalemia, hypomagnesemia, and/or hypocalcemia may be seen.
Calcium salts are the mainstay of treatment of hydrofluoric acid burns; the dose and route depend upon the clinical situation
22.2 A six-year-old child weighing 20 kg presents to hospital two hours after sustaining a burn to 25% of her body. Appropriate fluid management should include 1000 mL Hartmann’s solution in the next
a. 4 hours
b. 6 hours
c. 8 hours
d. 12 hours
e. 24 hours
B 6 hours
20 x 25 x 4 = 2000 L
(Parklands)
In first 8 hours 50%
1 L in 8 hours FROM TIME OF BURN
So in 6 hours.
