Approach to shock: Clinical sciences

Shock is a life-threatening condition that occurs when inadequate tissue perfusion and oxygen delivery leads to end organ damage and potentially death.

Now, the four types of shock include distributive, hypovolemic, cardiogenic, and obstructive. Distributive shock occurs in the setting of excessive systemic vasodilation, leading to impaired blood flow distribution. Next up, hypovolemic shock occurs due to a critical loss of fluid volume. Cardiogenic shock results from a compromise of myocardial performance, leading to a severely decreased cardiac output. Finally, obstructive shock results from obstruction of blood flow from either filling the heart or ejecting into the great vessels, which also ultimately leads to a decreased cardiac output.

Now, patients presenting with signs and symptoms of shock will be unstable, so immediately perform an ABCDE assessment and begin acute management. Start by stabilizing their airway, breathing, and circulation. This means that you might need to intubate the patient. Next, obtain IV access, and consider giving IV fluids, as well as placing a central venous catheter for administration of medications and hemodynamic monitoring.

Additionally, you can insert an arterial catheter for continuous monitoring of the mean arterial pressure, or MAP. Occasionally, you may also place a pulmonary artery catheter, or PAC, to measure certain hemodynamic parameters. Finally, put the patient on continuous vital sign monitoring, including heart rate, pulse oximetry, and blood pressure.

Ok, now that you’ve initiated acute management, it’s important to obtain a focused history and physical, as well as order lab tests. Patients may describe generalized weakness, fatigue, lethargy, and postural dizziness.

Physical exam typically reveals hypotension and weak peripheral pulses, as well as tachycardia, and possibly altered mental status. At this point you can suspect shock, so your next step is to assess the patient’s skin temperature as well as capillary refill time, or CRT.

CRT is an indicator of perfusion and is done by squeezing the patient’s digit until it blanches, then releasing the pressure and recording the time it takes to go back to its normal color. Normally this takes 2 seconds or less. Anything longer may be an indicator of poor perfusion due to impaired cardiac output.

So, if you notice warm, dry, flushed skin, you should immediately consider distributive shock. In addition, these patients may have a normal CRT. The different causes of distributive shock include sepsis, anaphylaxis or neurologic injury. First, let’s start with septic shock. These patients typically present with fever and symptoms suggestive of a source of infection, such as flank pain.

Physical exam might also reveal signs of a source of infection, like costovertebral tenderness; while labs could demonstrate leukocytosis and thrombocytopenia, as well as elevated lactate and inflammatory markers like ESR, CRP, and procalcitonin.

These findings should make you consider septic shock, so order blood cultures and imaging like X-ray and CT. If blood cultures are positive, and imaging reveals a source of infection, this supports the diagnosis of septic shock.

Here’s a high yield fact! Management includes fluid resuscitation, broad-spectrum antibiotics, and vasopressors like norepinephrine or dopamine.

Now, here’s a clinical pearl to keep in mind! If your patient presents with hypotension, warm skin and normal CRT in combination with fever, flank pain, and costovertebral tenderness, think of septic shock due to pyelonephritis!

Another type is anaphylactic shock. In this case, history typically reveals exposure to a known or suspected allergic trigger, such as food, insect stings or bites. Important physical exam findings include urticaria and itchy skin, as well as labored breathing, wheezing, and stridor due to airway edema.

In these individuals you should consider anaphylactic shock, so you can order tryptase which, if elevated, will help confirm the diagnosis of anaphylactic shock. However, keep in mind that tryptase won’t peak until 1 to 1.5 hours after the onset of symptoms.

As a high yield fact, management includes immediately removing the allergic trigger and giving intramuscular epinephrine.

The least common type of distributive shock is neurogenic shock. History generally reveals brain or high-level spinal cord injury or trauma. In contrast to other types of shock that compensate for low cardiac output by increasing the heart rate, in patients with neurogenic shock you may see a paradoxical bradycardia due to disruption of autonomic tracts.

Additionally, the physical exam might reveal neurologic deficits, such as paresis or paralysis. All of these findings should make you consider neurogenic shock, so immediately order a CT scan which may reveal a skull or vertebral fracture, cerebrovascular accident, as well as spinal cord injury. Positive image findings from the CT will support the diagnosis of neurogenic shock.

Now, let’s look at hypovolemic shock, which is characterized by a decrease in intravascular blood volume to a point where tissue perfusion can’t be adequately maintained.

So, if you notice cold, clammy skin and delayed CRT, then assess your patient for evidence of volume loss. If you see evidence, like from blood loss or dehydration, then consider hypovolemic shock. Hypovolemic shock can be further classified as hemorrhagic or non-hemorrhagic.

First, let’s start with patients that present with history suggesting a bleeding source, most commonly due to trauma or blood loss from the gastrointestinal or genitourinary tracts. These individuals often present with hematemesis, melena, or hematochezia, but sometimes there might be no visible sign of bleeding.

Additionally, CBC reveals low hemoglobin, which helps confirm blood loss. At this point, you should consider hemorrhagic shock, so your next step is to order imaging methods like ultrasound and CT, as well as diagnostic procedures such as EGD or colonoscopy, to visualize the bleeding source, which if found, supports the diagnosis of hemorrhagic shock.