Obstructive Shock

Question 1

OBSTRUCTIVE SHOCK

Answer 1

Obstructive shock is due to a decrease in venous return or cardiac compliance due to an increased left ventricular outflow obstruction or marked preload decrease.

Cardiac tamponade and tension pneumothorax are common causes.

***CARDIAC TAMPON AND TENSION PNEUMO***

Question 2

CARDIAC TAMPONADE

Answer 2

Cardiac tamponade, characterized by the accumulation of pericardial fluid under pressure, can be found in up to 2% of penetrating trauma to the thoracoabdominal region and very rarely in blunt trauma.

Question 3

CARDIAC TAMPONADE. Whats happening to the blood in the pericardial cavity?

Answer 3

• Blood in the pericardial cavity may be defibrinated resulting in a hematoma that may inhibit normal myocardial function.
• Intrapericardial blood accumulation eventually causes elevated intrapericardial pressure, which leads to decreasing right and left ventricular filling.
• Catecholamines are released in this state as a compensatory mechanism that results in tachycardia and further elevated right-sided filling pressures.
• Once the distensibility limits from intrapericardial fluid are reached by the pericardium, the myocardial septum shifts toward the left side, which further reduces left ventricular filling and subsequent cardiac output.
• This downward spiral eventually produces irreversible shock and death. Even small amounts of blood (65 to 100 mL) can lead to an acute rise in intrapericardial pressure.

Question 4

CT is identified by?Brainscape

Answer 4

• FAST exam
• Without bedside US, cardiac tamponade can be deceptively difficult to diagnose as the body compensates for the hemodynamic effects by various mechanisms.
• The reduced CO is offset by the increase in heart rate and increase in SVR.

-Often, the only clinical finding of pericardial tamponade is sinus tachycardia.

• Hypotension may be a sign of ominous decompensation and emergent need for surgical intervention if due to pericardial tamponade or systemic hypovolemia from other injuries.
• The classic finding of Beck’s triad of muffled heart sounds, hypotension, and distended neck veins is present in less than 10% of cases.2 Pulsus paradoxus, a substantial fall in systolic blood pressure during inspiration, and Kussmaul’s sign, an increase in jugular venous distention on inspiration, are not reliable signs and may only be found with moderate to severe tamponade.11
• A more reproducible sign of cardiac tamponade is a narrowing of the pulse pressure, which along with elevation of the central venous pressure, is cardiac tamponade until proven otherwise.

-The narrowed pulse pressure is not sensitive, and its absence should never be used to exclude tamponade. Usually the jugular venous pressure is elevated and may be associated with venous distention of the neck veins, forehead, and even scalp.