RECOGNITION & TREATMENT OF SHOCK

IN ANIMALS

EMERGENCY PROCEDURES

SHOCK: RECOGNITION AND TREATMENT

SHOCK is inadequate tissue perfusion resulting in poor oxygen deliveryCardiogenicDistributiveObstructiveHypovolemic

Shock• TYPES OF SHOCK:–Cardiogenic: results from heart failure • ↓ blood pumped by heart• HCM, DCM, valvular

insufficiency/stenosis

–Distributive: blood flow maldistribution (Vasodilation)• Sepsis, anaphylaxis →↓arteriole

resistance →loss of fluid from vessels to interstitial spaces →↓BP→ ↓ blood return to heart

SHOCK: RECOGNITION & TREATMENTTYPES OF SHOCK:–Obstructive - physical obstruction in circulatory system• HW disease → heart pumping against

the adult worm blockage• Gastric torsion →↓blood return to

heart

–Hypovolemic - decreased intravascular volume• Most common in small animals• Blood loss, dehydration from

excessive vomiting/diarrhea, effusion of fluid into 3rd spaces

HYPOVOLEMIC SHOCK

Pathophysiology of hypovolemic shock:

↓blood vol →↓venous return, ↓vent filling →↓stroke vol, ↓CO →↓BP

HYPOVOLEMIC SHOCK Stage I: Compensation

◦ Baroreceptors detect hypotension (↓BP)a. Sympathetic reflex—(Epi, Norepi, cortisol

released from adrenals)- ↑ HR, contractility- Constriction of arterioles (↑BP) to skin (cold,

clammy), muscles, kidneys, GI tract; not brain, heart

b. Renin (kidney)→angiotensin (blood)→aldosterone (adrenals) reflex- ↑ Na+ and water retention → ↑ intravascular vol

(↑BP)

◦ PE findings Tachycardia Prolonged cap refill time Pale mm

HYPOVOLEMIC SHOCK• Pathophysiology of hypovolemic shock

• Stage II: Decompensation– Tachycardia–Delayed cap refill time–Muddy mm (loss of pink color, more

brown than pink)–BP IS DROPPING–Altered mental state

• Stage III: Irreversible shock– PE findings worsen– cannot revive– death will occur

HYPOVOLEMIC SHOCK Treatment: the goal of therapy is

to improve O2 deliveryO2 supplementation

Face maskO2 cage/hoodsTranstracheal/nasal insufflation

Venous accessCephalicSaphenousJugularIntraosseous

Oxygen supplementation

FLUID ADMINISTRATION

CEPHALIC CATHETER PLACEMENT

INTRAOSSEOUS CATHETER PLACEMENT

CONTRAINDICATED IN PATIENTS WITHSEPSIS,FRACTURES, OR INFECTED BONES

INTRAOSSEOUS CATHETER PLACEMENT

SHOCK • Treatment–Fluid resuscitation (O2 delivery is improved by ↑CO)1. Crystalloids • Isotonic solutions (electrolytes: Na+, Cl-, K+,

bicarbonate)– Examples (body fluid=280-300 mOsm/L)» Lactated Ringer’s (273 mOsm/L)»Normal saline (0.9%) (308 mOsm/L)

– Dose: Dog 50-90 ml/kg/hr Cat 40-60 ml/kg/hr

SHOCK• Treatment:• 1. Crystalloids continued• Hypertonic solutions—when lg vol of fluid cannot

be administered rapidly enough– Examples—7.5% saline– Causes fluid shift from intercellular space→

intravascular space →↑vascular vol →↑venous return → ↑CO

– Also causes vasodilation → ↑ tissue perfusion– Dose: 4-6 ml/kg over 5 min

• Hypotonic solutions should never be used for hypovolemic shock– Examples—5% Dex in water (252 mOsm/L)

SHOCK Treatment

Fluid resuscitation (O2 delivery is improved by ↑CO)2. Colloids—Large molecular wt solutions that do not leave

vascular systemBetter blood volume expanders than crystalloids50-80% of infused volume stays in blood vesselsExamples

Whole bloodPlasma Dextran 70, Hetastarch, Vetstarch

SHOCK• Treatment (continued)

– SympathomimeticsUse only after adequate fluid administration if BP and

tissue perfusion have not returned to normal• Dopamine (Inotropin®)– 0.5-3.0 μg/kg/min

» Dilation of renal, mesenteric, coronary vessels– 3.0-7.5 μg/kg/min

» ↑ contractility of heart» ↑ HR

– >7.5μg/kg/min

» Vasoconstriction • Dobutamine (Dobutrex®)– ↑ contractility of heart (min effect on HR)

SHOCK• Monitoring Hemodynamic/metabolic sequelae of shock are continually

changing– Physical Parameters• Respiratory– Color of mm– RR – Breathing efforts smooth?– Breathing pattern regular?– Auscultation normal?

• Cardiovascular – HR normal?– ECG normal?– Color of mm– Cap refill time (1-2 sec)– Urine production? (1-2 ml/kg/hr)– Weak pulse? → ↓stroke volume

SHOCK Monitoring

Physiologic Monitoring ParametersO2 Saturation

Pulse oximetry—noninvasiveNormal: Hb saturations (SpO2)>95%

oSpO2<90%--serious hypoxemiaArterial BP—a product of CO, vascular capacity,

blood volume

SHOCK• Monitoring –Laboratory Parameters• Hematocrit (PCV)– Increase →dehydration–Decrease →blood loss

• Electrolytes– Proper balance needed for proper cell

function– Fluid therapy may alter the balance;

supplement fluid as needed

SHOCK• Monitoring• Arterial pH and blood gases– PaCO2 tells how well patient is ventilating» PaCO2 <35 mm Hg → hyperventilation

» PaCO2 >45 mm Hg → hypoventilation

– PaO2 Tells how well patient is being oxygenated» PaO2 <90 mm Hg → hypoxemia

– pH tells acid/base status of patient–<7.35 → acidosis–>7.45 → alkalosis