Pathophys FTW
What is shock?
Bonus: What are the 5 components of oxygen delivery?
PaO2, SaO2, Hgb, HR, SV (preload, afterload, and contractility)
7 year old MN Beagle presenting with a 24 hour history of profuse vomiting. QAR, HR 150, RR 30, MM pink + tachy, CRT 1-2 sec, Temp 100.2F, strong synchronous pulses, MAP 68.
Answer: Not shock
Borderline MAP alone does not = shock. Other perfusion parameters are adequate.
Hit by car dog with pale MM, weak pulses, HR 190, CRT 3 sec, MAP 72.
Answer: Compensated hypovolemic shock
Volume loss resulting in decreased preload and CO.
3 year old FS mixed-breed dog presents with acute hemorrhagic diarrhea. HR 180, pale MM, CRT 3 sec, MAP 35, lactate 5.6 mmol/L.
Fluids - isotonic crystalloid at 20mL/kg (1/4 shock bolus) and reassess
List four perfusion parameters you should monitor in a hospitalized shock patient.
HR, MM/CRT, lactate, urine output, MAP, mentation, temperature, pulse quality
Discuss the mechanism of the most common type of shock.
Hypovolemic - not enough circulating volume to deliver oxygen to the tissues
5 year old FS DSH cat presenting for unexplained lethargy. Temp 98.1F, HR 150, dull mentation, MAP 72.
Answer: Yes, decompensated shock
Hypothermia with bradycardia
Puppy presents after acutely collapsing following their vaccine appointment.
Distributive shock (vasodilatory shock d/t anaphylaxis)
Low SVR from vasodilation.
A dog in early hypovolemic shock has an improved MAP after a shock bolus, but pulses are still weak, he remains dull, and lactate remains elevated. What’s the next best step?
Administer another 1/4 shock bolus (20mL/kg) and reassess perfusion parameters
Which parameter is often the last to normalize during a successful shock resuscitation?
Lactate
Define septic shock. How is it unique in its response to treatment?
Shock secondary to an infectious nidus that is UNRESPONSIVE to volume resuscitation and requires pressor support.
8 year old MN Lab presenting in post-ictal phase after cluster seizures. HR 165, MM pink, CRT <1sec, strong pulses, MAP 100, lactate 5.1 mmol/L.
Answer: Not shock
Seizure related Type B hyperlactemia, not due to hypoperfusion
Cat with historic HCM presenting with hypotension and pulmonary edema.
Cardiogenic shock
A 10 year old dog presents for acute collapse with tachycardia and hypotension. On the physical he had distended jugular veins, weak pulses, and muffled heart sounds. What is the best treatment for his shock?
Pericardiocentesis - This is obstructive shock due to compression of the heart; fluids will not fix him until you relieve the obstruction.
What is the urine output goal for dogs and cats in shock recovery?
Greater than or equal to 1mL/kg/hr
Briefly discuss the mechanisms for obstructive, cardiogenic, and vasodilatory shock. Give an example of each.
Obstructive: Blood is not able to return to the heart, decreasing CO (GDV, thromboembolism, mesenteric volvulus, cardiac tamponade)
Cardiogenic: The heart is unable to produce enough CO (decreased contractility or the afterload is too high) - CVD, DCM, HCM in cats
Vasodilatory: Inability to keep vascular tone = tanked BP, blood unable to return to heart (anaphylaxis, SIRS, neurogenic)
6 year old FS Golden Retriever presenting after being hit by car injury. HR 190, pale MM, CRT 3 sec, weak pulses. Map 78. PCV 46%, TP 7.0, Lactate 6.3 mmol/L
Answer- yes compensated hypovolemic shock
Normal PCV/TS does not rule out acute hemorrhage
Hemangiosarcoma dog with muffled heart sounds and hypotension
Obstructive shock (cardiac tamponade)
A septic dog remains hypotensive (MAP 58) after receiving 90 mL/kg of crystalloids. Lactate remains elevated. Pulses are weak but lungs are clear.
Vasopressors (ex: norepinephrine)
Name three patient populations that are at increased risk of developing pulmonary edema during shock fluid resuscitation
Cardiac disease patients, hypoproteinemic patients, kidney disease patients, and SIRS/Septic patients
List the acute, moderate, and chronic compensation mechanisms of shock and mechanism of action.
Acute: Catecholamines (increase HR, contractility, vasoconstriction), cortisol (volume retention, augment catecholamines)
Moderate: angiotensin II (volume retention, vasoconstriction), vasopressin (ADH- vasoconstriction)
Chronic: Aldosterone (volume retention, vasoconstriction), ADH (volume retention)
10 year old MN Boxer who is currently under general anesthesia for a splenectomy. HR 70 bpm, MAP 55, ETCO2 48 mmHg, temp 99.6, warm extremities, strong pulse.
Not shock, this is anesthetic hypotension
A cat presents obtunded after falling from a 3rd story window. HR: 100, CRT 2sec, MAP 210, RR 50 and irregular respiration
Not in shock, this is a Cushing reflex (hypertension, bradycardia, irregular respirations) - this patient likely has brain trauma and increased ICP
A Doberman with known DCM presents. HR 200, weak pulses, MAP 55, cold extremities, pulmonary crackles are present.
Ionotropes (improve contractility and CO - dopamine, dobutamine, norepinephrine)
What lactate trend indicates adequate response to therapy?
Greater than or equal to 20% decrease in 2-4 hours