Hypotension / Shock

Shock is a life-threatening situation. In most cases, shock is due to poor tissue perfusion with impaired cellular metabolism, leading to progressive organ failure which if not reversed results in irreversible organ damage and death. Rapid and effective intervention is required to impede the progression of this serious disorder and ultimately impact patient survival.

Diagnosing shock in a timely way is an important training problem for medical students because accurate diagnosis requires prudent selection and interpretation of common diagnostic studies. Also, determining appropriate management strategies for shock under significant pressure is important because of its impact on patient morbidity and on health care cost.

Required Skills/Procedures:

1. Perform situation-appropriate (problem-focused or complete) history and physical examinations
2. Interpret clinical information to formulate a prioritized differential diagnosis
3. Guide the creation of a patient-specific management plan

Appropriate Setting: Inpatient

Expected level of Responsibility: Direct supervision with real patients

Learning Topics during encounters with a patient with HYPOTENSION/SHOCK can include:

Medical Knowledge Learning Topics related to HYPOTENSION/SHOCK

1. Signs and symptoms, distinguishing clinical characteristics, and typical clinical course of the different types of shock:

hypovolemic shock
cardiogenic shock
extracardiac obstructive shock
distributive shock (profound decrease in systemic vascular tone)

2. Distinguishing features of the different stages of shock:

stage I – early, reversible and compensatory shock
stage II – intermediate or progressive shock
stage III – refractory or irreversible shock

3. Common conditions that result in shock:

severe bleeding
heart attacks
severe burns
severe bacterial infections
abdominal emergencies
excessive loss of body fluids
crush injuries

4. Utility and limitations of diagnostic tests including indications and cost:

vital signs
chest x-rays
Central Venous Pressure
ECG
arterial blood gases
pulmonary capillary wedge (Swann-Ganz)
echocardiogram

5. Priorities and specific goals of resuscitation for each form of shock:

priorities in resuscitation (ABCs)
choice of fluids
indications for transfusion
management of acute coagulopathy
indications for invasive monitoring
use of inotropes, afterload reduction in management

6. Vasopressors used in shock states

7. Strategies to prevent a patient from developing shock

8. Psychosocial, ethical, and legal issues relevant to patients suffering from shock

Diagnostic Evaluation Learning Topics related to HYPOTENSION/SHOCK

1. Age-appropriate medical history that differentiates among etiologies of disease, including:

known cardiac disease (coronary disease, CHF, pericarditis)
recent fever or infection (leading to sepsis)
drugs (excess diuretics or antihypertensives)
conditions predisposing for pulmonary embolism
possible bleeding from any site, particularly GI tract

2. Focused physical exam to include neck veins, cardiac, pulmonary, establish the diagnosis and severity of disease including:

jugular veins are flat in oligemic or distributive shock; jugular venous distention (JVD) suggests cardiogenic shock; JVD in presence of paradoxical pulse may reflect cardiac tamponade
evidence of CHF, murmurs of aortic stenosis, acute regurgitation (mitral or aortic), ventricular septal defect
asymmetry of pulses (aortic dissection)
tenderness or rebound in abdomen may indicate peritonitis or pancreatitis; high-pitched bowel sounds suggest intestinal obstruction; stool guaiac tests can rule out GI bleeding
fever and chills usually accompany septic shock; sepsis may not cause fever in elderly, uremic, or alcoholic patients.
skin lesions that may suggest specific pathogens in septic shock: petechiae or purpura (Neisseria meningitidis), erythema gangrenosum (Pseudomonas aeruginosa), generalized erythroderma (toxic shock due to Staphylococcus aureus or Streptococcus pyogenes).

3. Differential diagnosis recognizing specific history and physical exam findings that suggest a specific etiology

4. Diagnostic and laboratory tests and be able to interpret them (with consultation), both prior to and after initiating treatment based on the differential diagnosis. Considerations of test cost and performance characteristics as well as patient preferences

Hematocrit, WBC, electrolytes. If actively bleeding, check platelet count, PT, PTT, DIC screen.
Arterial blood gas usually shows metabolic acidosis (in septic shock, respiratory alkalosis precedes metabolic acidosis).
If sepsis suspected, blood cultures, urinalysis, and Gram stain and cultures of sputum, urine, and other suspected sites.
ECG (myocardial ischemia or acute arrhythmia), chest x-ray (CHF, tension pneumothorax, aortic dissection, pneumonia). Echocardiogram may be helpful (cardiac tamponade, CHF).
Central venous pressure or pulmonary capillary wedge (PCW) pressure measurements may be necessary to distinguish between different categories of shock:
- Mean PCW 6 mmHg suggests oligemic or distributive shock
- PCW 20 mmHg suggests left ventricular failure
- Cardiac output (thermodilution) is decreased in cardiogenic and oligemic shock, and usually increased initially in septic shock.

5. Skill in the placement of large-bore intravenous access (Seldinger technique)

6. Communication of the diagnosis to the patient

Management Plan Learning Topics related to HYPOTENSION/SHOCK

1. Airway control, breathing and circulatory support including:

rapid improvement of tissue hypoperfusion and respiratory impairment: serial measurements of bp (intraarterial line preferred), heart rate, continuous ECG monitor, urine output, pulse oximetry, blood studies: Hct, electrolytes, creatinine, BUN, ABGs, calcium, phosphate, lactate, urine Na concentration (20 mmol/L suggests volume depletion)
continuous monitoring of CVP and/or pulmonary artery pressure, with serial PCW pressures.
supplemental oxygen therapy may be needed; intubation may be needed if consciousness is an issue.

2. Foley catheter to monitor urine flow

3. Frequent mental status assessments

4. Augmentation systolic bp to _100 mmHg:

place in reverse Trendelenburg position
IV volume infusion (500- to 1000-mL bolus), unless cardiogenic shock suspected (begin with normal saline, then whole blood, dextran, or packed RBCs, if anemic); continuation of volume replacement as needed to restore vascular volume

5. Vasoactive drugs after intravascular volume is optimized; administration of vasopressors if systemic vascular resistance (SVR) is decreased (begin with norepinephrine or dopamine; for persistent hypotension add phenylephrine or vasopressin)

6. Addition of inotropic agents (usually dobutamine) to maintain cardiac index 2.2 (L/m2)/min [4.0 (L/m2)/min in septic shock] in CHF

7. Administration of 100% O2; intubation with mechanical ventilation if PO _ 70 2mmHga

8. If severe metabolic acidosis present (pH _ 7.15), administration NaHCO3 (44.6–89.2 mmol)

9. Identification and treatment of the underlying cause of shock

Emergent coronary revascularization may be lifesaving if persistent ischemia is present
Consideration of cardiac tamponade

10. Management of infection if sepsis present

Potential Differential Diagnosis Topics Include:

Hypovolemic shock

hemorrhage
volume depletion (e.g., vomiting, diarrhea, diuretic over-usage, ketoacidosis, third spacing such as burns)
internal sequestration (ascites, pancreatitis, intestinal obstruction)

Cardiogenic shock

myopathic (acute MI, dilated cardiomyopathy)
mechanical (acute mitral regurgitation, ventricular septal defect, severe aortic stenosis, tampanode)
arrhythmic
dissection

Extracardiac obstructive shock

pericardial tamponade
massive pulmonary embolism
tension pneumothorax

Distributive shock (profound decrease in systemic vascular tone)

sepsis
toxic overdoses
anaphylaxis
neurogenic (e.g., spinal cord injury)
endocrinologic (Addison’s disease, myxedema)