L28: Heat Stroke (Cooke)

Question 1

70% of total body heat loss is via what mechs?

Answer 1

Radiation

convection (movement of air across body to cool)

Question 2

Mechanisms of heat dissipation

Answer 2

Radiation
Convection
Conduction
Evaporation (more difficult as humidity increases)

Question 3

Relationship between CO and heat loss

Answer 3

Increased CO (due to increased HR and/or stroke volume) –> peripheral vasodilation –> increased circulation to skin –> facilitates heat loss through radiation, convection, and conduction

Question 4

2 main predisposing causes of heatstroke

Answer 4

Decreased heat dissipation

Increased heat production

Question 5

Causes of decreased heat dissipation

Answer 5

Lack of acclimation
Confinement/poor ventilation
Increased humidity
Dehydration
Abnormal respiration (brachys, lar par, CNS dz)

Question 6

Causes of increased heat PRODUCTION

Answer 6

• exercise
• seizures
• hyperthyroidism
• drugs/toxin (amphetamines, macadamia nuts)

Question 7

CS of heatstroke

Answer 7

Panting
Ataxia
Vomiting/diarrhea
Disorientation/seizures

Question 8

Systemic effects of heatstroke (T > 106.9)

Answer 8

Protein denaturation
Enzyme dysfx
Mitochondrial dysfx
Cell membrane dysfx
Cardiopulmonary effects (vasodilation, +/- dehydration)

–> SYSTEMIC CELL DEATH

Question 9

Consequences of vasodilation +/- dehydration 2ary to hyperthermia

Answer 9

Decreased perfusion and heat dissipation –> cell death (esp. Of RBCs and endothelium)

Question 10

Death of cardiac myocytes –>

Answer 10

Arrhythmias –> death

Question 11

Death of pulmonary endothelium –>

Answer 11

ARDS –> vasculitis, leaking protein and fluid –> death

*any endothelium can be affected, but pulmonary endothelium most sensitive

Question 12

Death of neurons –>

Answer 12

Cerebral edema –> seizures, coma –> death

Question 13

Death of enterocytes –>

Answer 13

Hemorrhage, bacterial transduction –> anemia, sepsis –> DIC/death

*enterocytes extra susceptible b/c of long villi far from blood supply

Question 14

Death of hepatocytes –>

Answer 14

Necrosis, cholestasis –> hepatic failure –> DIC/death

Question 15

Death of renal tubular cells –>

Answer 15

Tubular necrosis –> renal failure (acute anuric or oliguric) –> death

-

Question 16

Death of RBCs/endothelium –>

Answer 16

Sludging
Hemolysis
Ischemia
Thromboplastin release

—> DIC –> death

Reason: cell damage –> protein exposure –> thrombus formation

Damaged endothelium allows for blood/fluid to leak out of vascular space, or for sludging, which sets up for DIC

Question 17

PE findings in EARLY heatstroke

Answer 17

Increased temp
Tachycardia
Bounding pulses
Tachypnea +/- upper airway sounds
Hyperemic mm
CRT

Question 18

PE findings of LATE heatstroke

Answer 18

Inc. OR dec. temp
Tachycardia
WEAK pulses (2ary to hypovolemia or dec. CO due to cardiac myocardium dysfx)

Tachypnea +/- upper airway sounds
Pale/grey mm
CRT >2 sec
Demented, obtunded
May have blood on rectal, urine may be discolored, +/- petechia

Question 19

Initial Diagnostics of heatstroke patient**

Answer 19

PCV/TP (dehydrated?)
Blood smear (thrombocytopenic?)
Basic Chem
Blood gas (acidemic? Lactate?) - can be venous
UA (what is SG? Evidence of myoglobin or hemoglobin?)
Coag status: ACT or PT/PTT (DIC?)
Arterial BP
Rectal exam (hemorrhage present?)

*presence of myoglobin/Hb in UA negative prognostic indicator

Question 20

Common bloodwork, UA, and BP changes in heatstroke patient

Answer 20

• Hemoconcentration INITIALLY with an increase in nRBCs
• Anemia LATER (probably from damage to bone marrow)
• azotemia (may be pre-renal)
• thrombocytopenia
• increased liver values (AST, ALT, bilirubin)
• hypotension
• hemoglobinuria/myoglobinuria
• urinary casts

Question 21

Steps in treating heatstroke patient

Answer 21

1) start cooling ASAP!!
2) secure airway/O2
3) IV catheter, draw blood for MDB and hold samples for full CBC, Chem, UA
4) stop cooling at 103-103.5
5) indirect BP

Question 22

Fluid therapy guidelines

Answer 22

• caution, not all heatstroke patients are dehydrated and they are susceptible to fluid overload if have leaky vessels
• goal = support perfusion, correct acid/base abnormalities
• crystalloids first choice
• colloids indicated when can’t get HR/BP and acid/base status resolved, and may need to add pressors (plasma if evidence of coagulopathy, hetastarch/dextrans if no coagulopathy)
• DON’T give entire shock dose! (Give 1/4 to 1/3 shock dose)

Question 23

Vasopressors you can use in heatstroke patients

Answer 23

Dopamine
Dobutamine
Vasopressin
Norepi

Question 24

Common sequelae of heatstroke

Answer 24

ARF
GI ulceration/hemorrhage +/- sepsis
Hepatic failure
DIC
Seizures
Arrhythmias
ARDS

Question 25

Tx/prevention of ARF in heatstroke patient

Answer 25

- support perfusion, ensure urine output (give fluids, pressors, monitor output) - reverse any oliguric failure

Question 26

Tx/prevention of GI ulceration (and subsequent hemorrhage, sepsis, vomiting) in heatstroke patient

Answer 26

- goals: support perfusion to reduce formation and promote healing, control vomiting, reduce risk of sepsis - tx with fluids, pressors, famotidine (H2 blocker) OR pantoprazole (proton pump inhibitor), antiemetics, +/- abx - don't give proton pump inhibitor if vomiting

Question 27

Tx/prevention of hepatic failure in heatstroke patient

Answer 27

- major concerns: coagulopathy, hyoglycemia (2ary to sepsis), hypoalbuminemia (from leaky vessels or hepatic failure), hepatic encephalopathy - tx with plasma, dextrose fluids, lactulose PRN - SAMe, milk thistle, etc. - give plasma if hypoalbuminemia AND coagulopathic**

Question 28

Tx/prevention of DIC in heatstroke patient

Answer 28

- monitor for evidence of petechia/ecchy, internal bleeding | - tx with plasma if above occurs or if coags become prolonged

Question 29

Calculate shock dose

Answer 29

90 mls/kg X BW (kg)

Question 30

Tx reduced urine production with

Answer 30

Furosemide

Question 31

Tx/prevention of Seizures in heatstroke patient

Answer 31

- diazepam +/- mannitol (if there is cerebral edema) | - ideally should NOT give mannitol if not rehydrated yet!

Question 32

Tx/prevention of arrhythmias in heatstroke patient

Answer 32

- monitor ECG - assess effect on CO - goal = prevent sudden death - lidocaine - don't always tx VPCs unless having negative effect on CO

Question 33

Tx/prevention of ARDS in heatstroke patient

Answer 33

- concerns: thromboembolism, vasculitis - want to avoid fluid overload and support resp. System - monitor RR, SpO2 - O2 therapy, colloids PRN

Question 34

Negative prognostic indicators in heatstroke patients

Answer 34

``` Comatose Hypothermic Persistent hypoglycemia Progressive azotemia DIC Refractory hypotension Hyperbilirubinemia Oliguria ```

Question 35

Prognosis of heatstrok

Answer 35

Guarded to grave - complications can occur 12 hrs to 7 days later - should monitor for 24-48 hrs minimum - requires intensive management - can be very expensive

Question 36

4 main stages of heat-related injury in HUMANS

Answer 36

1) Heat cramps 2) Heat exhaustion 3) Heat prostration (headache, tachycardia, hypotension) 4) Heat stroke (CNS dysfx, circulatory insufficiency)