4 Distributive and Septic Shock

How distributive shock presents

Distributive shock occurs when widespread vasodilation and altered blood flow impair tissue perfusion, even when total blood volume is not initially depleted. Causes include sepsis, anaphylaxis, and neurogenic injury.

In early distributive shock, skin may be warm and flushed, with bounding pulses. Later, vasoconstriction may make the skin cool and clammy. Confusion, tachycardia, rapid breathing, reduced urine output, and hypotension are important warning signs. Normal blood pressure does not rule out early shock.

Recognizing possible septic shock

Suspect septic shock when infection is accompanied by signs of poor perfusion or organ dysfunction, even before severe hypotension appears. For example, an older adult with a suspected urinary infection who is newly confused, breathing rapidly, has a heart rate of $122$ per minute, warm skin, and blood pressure of $104\ \mathrm{mm\,Hg}$ systolic and $66\ \mathrm{mm\,Hg}$ diastolic may have early distributive shock. A systolic pressure above $90\ \mathrm{mm\,Hg}$ does not rule it out, and cool skin is not required.

Assess and escalate promptly. Consider airway, breathing, circulation, vital signs, oxygenation, perfusion, and the likely infection source. Follow local protocols and reassess the patient frequently.

Assessing perfusion and organ dysfunction

Worsening drowsiness, falling urine output, delayed capillary refill, and elevated lactate can signal impaired perfusion and possible organ dysfunction. Assess trends and the whole clinical picture rather than relying on a single finding.

Lactate is useful in assessment, but lactate alone does not confirm the infection’s location. Reduced urine output is relevant to assessing perfusion.

Starting emergency sepsis care

Sepsis and septic shock are emergencies. For adults with septic shock, the stated guideline recommends immediate antimicrobials, ideally within $1$ hour of recognition. Obtain blood cultures promptly, ideally before antimicrobials when doing so will not delay treatment, and measure lactate.

Begin intravenous crystalloid resuscitation promptly. The guideline suggests at least $30\ \mathrm{mL/kg}$ within the first $3$ hours for sepsis-induced hypoperfusion or septic shock. Individual circumstances matter, so reassess frequently to avoid both under-resuscitation and over-resuscitation. Crystalloids are used, with balanced crystalloids preferred when appropriate.

Do not delay treatment until all culture results are available. Oral fluids or waiting several hours to reassess are not the stated initial approach.

Managing persistent hypotension

If hypotension persists after initial fluid resuscitation in an adult with septic shock, norepinephrine is the recommended first-line vasopressor. The usual initial mean arterial pressure target for most adults is about $65\ \mathrm{mm\,Hg}$, with targets individualized as needed. For adults aged $65$ years or older, the stated guideline suggests an initial target range of $60$–$65\ \mathrm{mm\,Hg}$.

Reassessing treatment and evaluating the source

After treatment begins, reassess perfusion and fluid responsiveness, monitor vital signs and urine output, and follow lactate trends when appropriate. Dynamic measures can help guide further fluid resuscitation. Do not continue repeated fluid boluses without checking the patient’s response, and do not stop monitoring simply because blood pressure improves.

Rapidly evaluate whether the infection source requires source control. Continue to assess for ongoing organ dysfunction rather than waiting for shock to resolve before investigating the source.

Responding to possible anaphylaxis

Anaphylaxis is another cause of distributive shock. Hives, lip swelling, wheezing, and dizziness shortly after a medication is given are concerning for possible anaphylaxis. Give intramuscular epinephrine promptly and activate the emergency response; do not wait for laboratory confirmation. An antihistamine is not a substitute for epinephrine.

• Tissue hypoperfusion