6 Shock Management: Integrated Practice

Recognizing shock

Shock is a time-critical failure of tissue perfusion: the circulation does not deliver enough oxygen to tissues. Suspect it with altered mentation, weak pulses, cool or mottled skin, delayed capillary refill, low urine output, tachypnea, or hypotension. Hypotension may be a late sign, so the absence of low blood pressure does not rule out deterioration.

Compare the shock mechanisms

A useful first comparison is volume, pump, vessels, or blockage. These patterns guide the search for a cause, but they are clues rather than rules; more than one mechanism can coexist. For example, a patient with sepsis may also be volume-depleted or have impaired cardiac function.

• Hypovolemic shock: There is not enough circulating volume. Possible causes include bleeding, vomiting, diarrhea, and burns. Clues often include tachycardia, cool skin, flat neck veins, and narrow pulse pressure.

• Cardiogenic shock: The heart cannot pump effectively, for example after infarction or with dysrhythmia. Clues often include pulmonary crackles, jugular venous distention, chest discomfort, or cool extremities.

• Distributive shock: Vessels dilate and blood is maldistributed. Causes include sepsis, anaphylaxis, and neurogenic injury. Skin may be warm early in sepsis, and findings vary by cause.

• Septic shock: This is infection-related distributive shock with impaired perfusion. Fever may be absent, and lactate can be elevated.

• Obstructive shock: A mechanical blockage impairs cardiac filling or blood flow. Consider tension pneumothorax, tamponade, or massive pulmonary embolism; treat the obstruction urgently.

Act on the cause

In undifferentiated shock, act in parallel: summon emergency help, assess airway and breathing, provide oxygen when indicated, establish vascular access, monitor ECG and oxygen saturation, and rapidly search for reversible causes. Use focused examination and bedside ultrasound where available, but do not let tests delay lifesaving treatment of an obvious emergency. Activate the appropriate response team and follow local protocols.

Match treatment to the mechanism: replace lost volume and control bleeding in hypovolemia; support the pump and treat the cardiac cause in cardiogenic shock; restore vascular tone and address the cause in distributive shock; and remove the blockage in obstructive shock. Fluids are not automatically beneficial, especially when pulmonary congestion or cardiac pump failure is present.

Treat volume loss and pump failure

Bleeding and fluid loss

After a motor-vehicle collision, restlessness, pallor, diaphoresis, a heart rate of $132/\text{min}$, blood pressure of $84/56\ \text{mm Hg}$, weak peripheral pulses, and a distended abdomen suggest hypovolemic hemorrhagic shock. A distended abdomen after trauma raises concern for internal bleeding; no major external bleeding does not exclude severe blood loss. Call for trauma and hemorrhage-control support, control any external bleeding, establish rapid vascular access, and prepare blood products and definitive bleeding control. Avoid delaying hemorrhage control with repeated crystalloid boluses.

Several days of vomiting and diarrhea with dizziness on sitting up, dry mucous membranes, heart rate of $118/\text{min}$, cool hands, reduced urine output, and clear lung sounds suggest hypovolemic shock from fluid loss. Give isotonic crystalloid in reassessed increments as appropriate, address the ongoing source of loss, and monitor electrolytes and renal function. Improvement in mentation, pulse, blood pressure, capillary refill, and urine output suggests better perfusion. New crackles or worsening breathing may indicate fluid intolerance and should prompt reassessment.

Pump failure

Crushing chest pressure, pallor, clammy skin, blood pressure of $78/50\ \text{mm Hg}$, heart rate of $118/\text{min}$, oxygen saturation of $91\%$, bilateral crackles, and acute ischemic ECG changes suggest cardiogenic shock due to acute myocardial infarction. Support oxygenation as needed, obtain continuous ECG and hemodynamic monitoring, and activate urgent cardiology and revascularization care. Avoid reflexive large-volume fluid administration because pulmonary congestion may worsen; any fluid trial should be cautious and guided by assessment. Emergency revascularization of the culprit vessel is indicated for acute coronary syndrome with cardiogenic shock. A response includes improved perfusion and oxygenation without increased pulmonary edema.

Treat distributive shock

Sepsis

Confusion and hypotension in a patient with pneumonia, temperature of $39^\circ\text{C}$, heart rate of $124/\text{min}$, respiratory rate of $30/\text{min}$, blood pressure of $82/48\ \text{mm Hg}$, elevated lactate, and warm skin suggest septic distributive shock. Begin prompt sepsis care: obtain cultures when feasible without delaying treatment, administer appropriate antimicrobials promptly, assess for source control, and give crystalloid with frequent reassessment.

For adults with sepsis-induced hypoperfusion or septic shock, guidelines suggest at least $30\ \text{mL/kg}$ of crystalloid within the first $3$ hours, individualized to the patient's condition and response. If hypotension persists, norepinephrine is the usual first-line vasopressor; an initial mean arterial pressure (MAP) target of about $65\ \text{mm Hg}$ is commonly recommended.

Anaphylaxis

Hives, lip swelling, wheezing, and blood pressure of $76/42\ \text{mm Hg}$ developing minutes after a medication suggest anaphylactic distributive shock. Give intramuscular epinephrine promptly according to protocol, activate emergency support, and support airway and breathing. Additional treatment may include oxygen, IV fluids, and further clinician-directed therapy. Antihistamines do not replace epinephrine as the initial lifesaving treatment. Symptoms can recur, so reassess airway swelling, breathing, blood pressure, skin findings, and response to treatment.

Relieve obstructive causes

Tension pneumothorax

After chest trauma, rapidly worsening severe shortness of breath and hypotension, absent breath sounds on one side, distended neck veins, and an apparently shifted trachea suggest obstructive shock from tension pneumothorax. This is a clinical emergency: urgently decompress the chest using the trained clinician's approved method, then place a chest tube. In an unstable patient with a strongly suspected tension pneumothorax, do not delay decompression for imaging. Look for improved breathing, oxygenation, blood pressure, and perfusion after the obstruction is relieved.

Cardiac tamponade

Hypotension and tachycardia after a recent penetrating chest injury, together with distended neck veins and distant heart sounds, suggest cardiac tamponade. Bedside ultrasound showing pericardial fluid with impaired cardiac filling supports the concern. Arrange immediate definitive decompression and trauma or surgical management. In trauma-related tamponade, surgical decompression may be required; the appropriate procedure depends on the cause and setting. Improvement in blood pressure and perfusion after decompression supports relief of the obstruction.

Pulmonary embolism

Sudden shortness of breath and chest discomfort after a period of immobility, with tachycardia, hypotension, hypoxemia, relatively clear lungs, and bedside echocardiography suggesting right-ventricular strain, raises concern for obstructive shock from high-risk pulmonary embolism. Support oxygenation and circulation, obtain urgent specialist assessment, and pursue definitive treatment. Depending on the patient's risk and contraindications, treatment may include anticoagulation and urgent reperfusion strategies such as thrombolysis, catheter-based treatment, or embolectomy. Reassess hemodynamics, oxygenation, mental status, and right-heart findings.

Reassess perfusion and response

Judge response by trends rather than a single blood-pressure reading. Reassess mental status, pulse quality, skin temperature and capillary refill, MAP, urine output, oxygenation, lactate trend when available, and signs of fluid overload. In the individual cases, also reassess ongoing blood loss, pulmonary edema, breathing, airway swelling, and right-heart findings as relevant.

If perfusion does not improve, reconsider the diagnosis, look for mixed shock or ongoing losses, and escalate definitive treatment. The central goal is to recognize the pattern without relying on any one sign, treat the cause urgently, and repeatedly determine whether tissue perfusion is improving.