Approach to shock: Clinical sciences

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Introduction0:00–1:05

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.

Acute Management1:05–2:08

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.

Focused H&P2:08–3:13

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.

Distributive shock3:13–6:59

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.

Hypovolemic shock6:59–9:55

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.
Now, let’s take a look at non-hemorrhagic shock. These individuals report a history of vomiting, diarrhea, or burns.
In this case, physical exam often reveals decreased skin turgor, dry mucous membranes, as well as decreased urine output.
Additionally, CBC reveals high hemoglobin, which suggests hemoconcentration. These patients should make you think of non-hemorrhagic shock, so the next step is to assess each organ system for the cause of fluid loss.
In patients who describe excessive diarrhea or vomiting, think of gastrointestinal causes like irritable bowel syndrome or GI infection.
On the other hand, if your patient presents with severe blistering or eschar formation, consider burn injury. Either of these will support the diagnosis of non-hemorrhagic shock.Here’s a high yield fact!
Management of hypovolemic shock includes addressing the underlying cause, while also giving IV fluids, or even blood transfusions if needed.
Keep in mind that vasopressors are typically not recommended here, since they can further decrease tissue perfusion.Ok, let’s go over the last two categories of shock, starting with cardiogenic shock.

Cardiogenic shock9:55–11:59

When treating patients that have cold, clammy skin and delayed CRT with no evidence of blood or fluid loss, you should consider either cardiogenic or obstructive shock.
So, if you suspect cardiogenic shock, you should immediately order labs, including cardiac enzymes and BNP, ECG, and imaging such as transthoracic echocardiography, or TTE for short.
These diagnostic methods will help you differentiate between the most common causes of cardiogenic shock, heart failure and myocardial infarction.Let’s start with heart failure.
These individuals usually report shortness of breath and fatigue. Physical exam often reveals signs of volume overload, such as peripheral edema, crackles, and jugular venous distension; but keep in mind that some patients can also occasionally present without volume overload.
Laboratory studies will typically show an elevated BNP; while a TTE might demonstrate systolic or diastolic dysfunction, structural changes, or valvular incompetence.
With these findings, you can have confidence that the diagnosis is heart failure.Another important cause is myocardial infarction.
These patients typically report a squeezing substernal chest pain that radiates to the arm and might be diaphoretic on a physical exam.
Additionally, ECG findings can include ST elevations, while labs reveal elevated cardiac enzymes, which confirm the diagnosis of myocardial infarction.Now, let’s go back to obstructive shock.

Obstructive shock11:59–17:48

So, if you suspect obstructive shock, history and physical should point to the most likely underlying cause and guide your next steps in management, such as labs or imaging.
These diagnostic methods will help you differentiate between the most common causes of obstructive shock, such as pulmonary embolism, cardiac tamponade, and tension pneumothorax.
First, let’s start with pulmonary embolism, which is typically associated with pleuritic chest pain, hemoptysis, and a history of DVT.
Physical exam findings usually include tachypnea, as well as unilateral leg swelling; while labs might reveal a high D-dimer level.
In these patients, use Wells criteria and imaging, primarily CTPA to diagnose pulmonary embolism. Moreover, Wells score above 2 and filling defects on CTPA confirm the diagnosis of pulmonary embolism.
On the other hand, in cardiac tamponade, individuals usually report chest pain that’s relieved by sitting up and leaning forward.
The classic physical findings, known as the Beck triad, include hypotension, jugular venous distension, and muffled heart sounds.Chest X-ray might reveal a widened mediastinum and a water bottle sign, where the cardiac silhouette appears enlarged and stretched.
Diagnosis of cardiac tamponade can be confirmed via echocardiogram, which typically shows pericardial effusion, as well as the diastolic collapse of the right atrium and ventricle.
Finally, let’s take a look at tension pneumothorax, which is associated with a history of sudden and severe chest pain and shortness of breath; as well as physical exam findings, such as shallow breathing, tachypnea, absent breath sounds on the affected side, and tracheal deviation toward the opposite side.
Remember that tension pneumothorax is a clinical diagnosis based on history and physical, so it doesn’t need further testing.
Here’s a clinical pearl! If you suspect tension pneumothorax, proceed with emergent needle decompression to release trapped air from the chest cavity.
Once released, the patient’s general condition will immediately improve. This confirms the diagnosis of tension pneumothorax.
Sometimes, you can order a chest X-ray to detect a visible visceral pleural edge with absent distal lung markings on the affected side, as well as tracheal deviation and mediastinal shift toward the opposite side.
Now one last high yield fact. While not routinely used in clinical practice, placement of a pulmonary artery catheter, or PAC, can be useful in the differentiation of one type of shock from another as well as help guide hemodynamic resuscitation efforts, like the rate of IV fluid infusion and the decision to use vasopressors or inotropes.
PAC parameters commonly utilized include pulmonary capillary wedge pressure or PCWP, which gives an indirect measure of left atrial pressure; central venous pressure, or CVP, is a reflection of right atrial pressure; systemic vascular resistance, or SVR, is the afterload, or the resistance to blood flow in the peripheral arteries; cardiac index, or CI, indicates the cardiac output from the left ventricle; and finally, venous oxygen saturation or SVO2 measures the oxygen saturation in venous blood.
In cardiogenic shock, PAC values you’ll see include an increased PCWP and CVP, increased SVR, and decreased CI and SVO2.
In obstructive shock, PAC will reveal a decreased PCWP, except in tamponade where PCWP can be paradoxically increased; as well as increased CVP, increased SVR, and decreased CI and SVO2.
In hypovolemic shock, your PAC values will reveal a decreased PCWP and CVP, increased SVR, and decreased CI and SVO2. In distributive shock, your PAC values will reveal a decreased PCWP and CVP, decreased SVR, and increased CI and SVO2 in sepsis or anaphylaxis, but decreased CI and SVO2 in neurogenic shock.
Also, keep in mind that there are minimally invasive and noninvasive hemodynamic monitoring devices that can be used as alternatives to PAC.Alright, as a quick recap… Shock is a life-threatening condition that needs to be diagnosed and treated quickly.

Review17:48–18:56

Patients with shock are unstable and require airway support, IV fluid resuscitation, and vital sign monitoring. Once you suspect shock, assess the patient’s skin temperature and CRT.
Warm, dry, flushed skin and a normal CRT suggest distributive shock, such as septic, anaphylactic, and neurogenic shock.
On the other hand, if you notice cold, clammy skin and delayed CRT, assess for evidence of volume loss. Volume loss is associated with hypovolemic shock, further classified as hemorrhagic or non-hemorrhagic.
If there’s no evidence of blood or fluid loss, think of cardiogenic shock, most commonly due myocardial infarction and heart failure; or obstructive shock, which can occur due to pulmonary embolism, cardiac tamponade, and tension pneumothorax.
Approach to shock: Video, Causes, and Symptoms | Osmosis