L28: Heat Stroke (Cooke) Flashcards
70% of total body heat loss is via what mechs?
Radiation
convection (movement of air across body to cool)
Mechanisms of heat dissipation
Radiation
Convection
Conduction
Evaporation (more difficult as humidity increases)
Relationship between CO and heat loss
Increased CO (due to increased HR and/or stroke volume) –> peripheral vasodilation –> increased circulation to skin –> facilitates heat loss through radiation, convection, and conduction
2 main predisposing causes of heatstroke
Decreased heat dissipation
Increased heat production
Causes of decreased heat dissipation
Lack of acclimation Confinement/poor ventilation Increased humidity Dehydration Abnormal respiration (brachys, lar par, CNS dz)
Causes of increased heat PRODUCTION
- exercise
- seizures
- hyperthyroidism
- drugs/toxin (amphetamines, macadamia nuts)
CS of heatstroke
Panting
Ataxia
Vomiting/diarrhea
Disorientation/seizures
Systemic effects of heatstroke (T > 106.9)
Protein denaturation Enzyme dysfx Mitochondrial dysfx Cell membrane dysfx Cardiopulmonary effects (vasodilation, +/- dehydration)
–> SYSTEMIC CELL DEATH
Consequences of vasodilation +/- dehydration 2ary to hyperthermia
Decreased perfusion and heat dissipation –> cell death (esp. Of RBCs and endothelium)
Death of cardiac myocytes –>
Arrhythmias –> death
Death of pulmonary endothelium –>
ARDS –> vasculitis, leaking protein and fluid –> death
*any endothelium can be affected, but pulmonary endothelium most sensitive
Death of neurons –>
Cerebral edema –> seizures, coma –> death
Death of enterocytes –>
Hemorrhage, bacterial transduction –> anemia, sepsis –> DIC/death
*enterocytes extra susceptible b/c of long villi far from blood supply
Death of hepatocytes –>
Necrosis, cholestasis –> hepatic failure –> DIC/death
Death of renal tubular cells –>
Tubular necrosis –> renal failure (acute anuric or oliguric) –> death
-
Death of RBCs/endothelium –>
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
PE findings in EARLY heatstroke
Increased temp Tachycardia Bounding pulses Tachypnea +/- upper airway sounds Hyperemic mm CRT
PE findings of LATE heatstroke
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
Initial Diagnostics of heatstroke patient**
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
Common bloodwork, UA, and BP changes in heatstroke patient
- 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
Steps in treating heatstroke patient
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
Fluid therapy guidelines
- 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)
Vasopressors you can use in heatstroke patients
Dopamine
Dobutamine
Vasopressin
Norepi
Common sequelae of heatstroke
ARF GI ulceration/hemorrhage +/- sepsis Hepatic failure DIC Seizures Arrhythmias ARDS
Tx/prevention of ARF in heatstroke patient
- support perfusion, ensure urine output (give fluids, pressors, monitor output)
- reverse any oliguric failure
Tx/prevention of GI ulceration (and subsequent hemorrhage, sepsis, vomiting) in heatstroke patient
- 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
Tx/prevention of hepatic failure in heatstroke patient
- 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**
Tx/prevention of DIC in heatstroke patient
- monitor for evidence of petechia/ecchy, internal bleeding
- tx with plasma if above occurs or if coags become prolonged
Calculate shock dose
90 mls/kg X BW (kg)
Tx reduced urine production with
Furosemide
Tx/prevention of Seizures in heatstroke patient
- diazepam +/- mannitol (if there is cerebral edema)
- ideally should NOT give mannitol if not rehydrated yet!
Tx/prevention of arrhythmias in heatstroke patient
- monitor ECG
- assess effect on CO
- goal = prevent sudden death
- lidocaine
- don’t always tx VPCs unless having negative effect on CO
Tx/prevention of ARDS in heatstroke patient
- concerns: thromboembolism, vasculitis
- want to avoid fluid overload and support resp. System
- monitor RR, SpO2
- O2 therapy, colloids PRN
Negative prognostic indicators in heatstroke patients
Comatose Hypothermic Persistent hypoglycemia Progressive azotemia DIC Refractory hypotension Hyperbilirubinemia Oliguria
Prognosis of heatstrok
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
4 main stages of heat-related injury in HUMANS
1) Heat cramps
2) Heat exhaustion
3) Heat prostration (headache, tachycardia, hypotension)
4) Heat stroke (CNS dysfx, circulatory insufficiency)
