A 53-year-old man is brought to the emergency department after being involved in a motor vehicle collision as an unrestrained driver. The patient was found unresponsive at the scene and was intubated by the paramedics. On arrival, blood pressure is 74/50 mm Hg and pulse is 116/min. The patient is intubated and mechanically ventilated. The trachea is midline. There are multiple bruises over the anterior chest. Breath sounds are present and equal bilaterally, and heart sounds are normal. A central venous catheter is placed for fluid resuscitation. Initial central venous pressure (CVP) is 12 mm Hg (normal: 6-8). After rapid infusion of 2 L of normal saline, blood pressure is 78/52 mm Hg, pulse is 120/min, and CVP is 18 mm Hg. Which of the following is the most likely diagnosis?
Central venous pressure in different types of shock | ||||
Shock | Hypovolemic | Distributive | Obstructive | Cardiogenic |
CVP | ↓ | ↓ | ↑ | ↑ |
Mechanism | ↓ Intravascular volume | ↓ Systemic vascular resistance | ↑ Back pressure from obstructed cardiac filling | ↑ Back pressure from forward pump failure |
| CVP = central venous pressure. | ||||
This patient with blunt chest trauma from a motor vehicle collision has tachycardia and severe hypotension consistent with shock. In patients with shock, a central venous catheter is often placed to facilitate fluid administration. It also allows measurement of central venous pressure (CVP), which is the pressure in the superior vena cava (SVC) where the catheter tip is located. Because SVC pressure approximates right atrial pressure, CVP provides an estimate of cardiac preload.
The CVP value can help differentiate between different types of shock:
A low CVP (low preload) typically reflects hypovolemic or distributive shock.
An elevated CVP (high preload) typically reflects cardiogenic or obstructive shock.
In the trauma setting, shock is first assumed to be due to hypovolemia (ie, hemorrhage), which would cause low CVP. However, this patient has elevated CVP; therefore, a source of cardiogenic or obstructive (rather than hypovolemic) shock should be sought (Choice C). Blunt cardiac injury (BCI) due to blunt chest trauma can lead to cardiogenic shock (with acute right heart dysfunction causing elevated CVP and left heart dysfunction causing refractory hypotension) or to obstructive shock (eg, cardiac tamponade). Other manifestations of BCI can include arrhythmia, acute coronary syndrome, and valve or wall rupture.
(Choice A) Anaphylaxis can cause severe hypotension due to severely decreased systemic vascular resistance (ie, distributive shock). However, the decreased resistance would result in low CVP.
(Choice D) Intracranial hemorrhage with increased intracranial pressure is associated with Cushing triad, characterized by hypertension (rather than hypotension), bradycardia (rather than tachycardia), and irregular respiration.
(Choice E) Spinal cord injury can cause severe hypotension due to disruption of the autonomic nervous system and decreased sympathetic tone in the peripheral vasculature (ie, distributive shock). However, this would cause low (rather than elevated) CVP. In addition, bradycardia (rather than tachycardia) would be seen due to decreased cardiac sympathetic stimulation.
(Choice F) Tension pneumothorax is another cause of obstructive shock but can be ruled out by the patient's bilateral equal breath sounds.
Educational objective:
Although shock in the trauma setting is initially assumed to be hypovolemic shock (from hemorrhage), elevated central venous pressure (CVP) is more consistent with obstructive or cardiogenic shock. Blunt cardiac injury with myocardial dysfunction can cause cardiogenic shock with elevated CVP and refractory hypotension.