5.2 Differentiation & Resuscitation of Non-Septic Shock States
Key Takeaways
Typical untreated shock profiles are useful patterns, not mandatory diagnostic cutoffs: hypovolemic (low CVP, low PCWP, low CO/CI, high SVR), cardiogenic (high CVP, high PCWP, low CO/CI, high SVR), distributive (low CVP, low PCWP, high/normal CO/CI, low SVR), and obstructive (high CVP, variable PCWP, low CO/CI, high SVR).
Hemorrhagic shock is stratified across ATLS Classes I through IV; Class III and IV hemorrhage mandates immediate balanced blood product resuscitation (1:1:1 MTP) and damage control resuscitation with permissive hypotension (SBP 80-90 mmHg), strictly avoided in traumatic brain injury.
First-line therapy for anaphylactic shock is intramuscular epinephrine 0.3 to 0.5 mg (1:1,000 concentration) administered into the anterolateral thigh every 5 to 15 minutes, accompanied by aggressive crystalloid loading.
For anaphylaxis refractory to repeated IM epinephrine, use a monitored IV epinephrine infusion and fluids with expert support. In patients taking beta-blockers, consider adjunctive glucagon (1–5 mg IV over five minutes, then 5–15 mcg/min), monitoring for vomiting and aspiration.
Neurogenic shock after cervical/high thoracic SCI causes hypotension, often bradycardia and warm skin. Current SCI guidance suggests augmenting MAP to at least 75–80 mmHg without active augmentation above 90–95 for 3–7 days; individualize the agent, with norepinephrine reasonable when bradycardia is present.
5.2 Differentiation & Resuscitation of Non-Septic Shock States
Clinical Scenario: A 42-year-old female presents following a high-speed collision with bilateral open femur fractures and pelvic instability. Vital signs: BP 82/56 mmHg, HR 136 bpm, RR 32/min, SpO2 94% on non-rebreather. Labs show lactate 5.8 mmol/L and base deficit -9 mEq/L. Ultrasound confirms pelvic free fluid without tamponade.
Hemodynamic Profiles Across Major Shock States
Shock represents acute circulatory failure where oxygen delivery () fails to meet cellular oxygen consumption (). The following are typical untreated profiles. Values vary with stage, treatment and mixed shock; isolated RV pump failure can have high CVP with normal/low PCWP, and distributive shock can develop low cardiac output. Integrate these patterns with examination and echocardiography:
| Shock Class | CVP | PCWP | CO / CI | SVR | Mixed Venous () | Primary Pathophysiology |
|---|---|---|---|---|---|---|
| Hypovolemic | Low (<4–6 mmHg) | Low (<6–8 mmHg) | Low () | High (>1200 dynes·s/) | Low (<65%) | Intravascular volume depletion |
| Cardiogenic | High (>12–15 mmHg) | High (>18 mmHg) | Severely Low () | High (>1400 dynes·s/) | Severely Low (<55–60%) | Primary pump failure with pulmonary congestion |
| Distributive | Low / Normal | Low / Normal | High (early) to Normal | Severely Low (<800 dynes·s/) | High (>75–80%) in sepsis | Profound peripheral vasodilation and vasomotor collapse |
| Obstructive: PE | High (>12–15 mmHg) | Normal / Low | Low () | High (>1200 dynes·s/) | Low (<60%) | RV outflow obstruction; acute cor pulmonale |
| Obstructive: Tamponade | High (>15–20 mmHg) | High (>15–20 mmHg) | Low () | High (>1200 dynes·s/) | Low (<60%) | Diastolic equalization (RA = RVEDP = PCWP = PAD) |
| Obstructive: Tension PTX | High (JVD present) | Low / Normal | Severely Low | High | Low | Intrathoracic pressure collapses vena cava |
Note
Distributive shock is the only shock class characterized by a primary decrease in SVR (<800 dynes·s/). Hypovolemic, cardiogenic, and obstructive shock usually trigger compensatory vasoconstriction; concurrent vasodilation or treatment can alter SVR.
Hemorrhagic Shock & ATLS Resuscitation
The American College of Surgeons classifies hemorrhage across four classes (70-kg adult):
| Parameter | Class I | Class II | Class III | Class IV |
|---|---|---|---|---|
| Blood Loss (mL / %) | <750 mL (<15%) | 750–1500 mL (15–30%) | 1500–2000 mL (30–40%) | >2000 mL (>40%) |
| Heart Rate (bpm) | <100 | 100–120 | 120–140 | >140 |
| Blood Pressure | Normal | Normal | Decreased | Severely Decreased |
| Pulse Pressure | Normal | Narrowed | Decreased | Severely Decreased |
| Respiratory Rate | 14–20 | 20–30 | 30–40 | >35 |
| Urine Output (mL/hr) | >30 | 20–30 | 5–15 | Negligible |
| Mental Status | Slightly Anxious | Mildly Anxious | Anxious / Confused | Confused / Lethargic |
| Resuscitation | Crystalloid | Crystalloid ± Blood | MTP 1:1:1 Blood | Immediate MTP + OR |
Base Deficit & Damage Control Resuscitation
Arterial base deficit quantifies anaerobic debt: mild (-2 to -5 mEq/L), moderate (-6 to -9 mEq/L), severe (<=-10 mEq/L). A worsening base deficit directly correlates with transfusion requirement and coagulopathy.
- Permissive Hypotension: In non-compressible torso hemorrhage, target SBP 80–90 mmHg (MAP 50–60 mmHg) until surgical hemostasis. This prevents "popping the clot" and minimizes dilutional coagulopathy.
- TBI Contraindication: Strictly contraindicated in Traumatic Brain Injury (TBI); maintain SBP >= 100–110 mmHg to preserve cerebral perfusion ().
- Balanced Transfusion: Activate MTP with a 1:1:1 ratio of PRBCs, FFP, and platelets. Administer tranexamic acid (TXA) 1 g IV over 10 minutes then 1 g over 8 hours within 3 hours of injury.
Anaphylactic Shock: Recognition & Epinephrine Protocols
Anaphylaxis is an acute, life-threatening systemic hypersensitivity causing massive release of histamine, tryptase, and leukotrienes.
- First-Line Drug: Intramuscular (IM) Epinephrine 0.3 to 0.5 mg of 1:1,000 concentration (1 mg/mL) injected into the mid-anterolateral thigh. Repeat every 5 to 15 minutes.
- Mechanisms: Alpha-1 reverses vasodilation and mucosal edema; beta-1 restores cardiac output; beta-2 halts mast cell degranulation and reverses bronchospasm.
- IV Epinephrine Safety: For refractory anaphylaxis, use a carefully titrated IV infusion with expert support and continuous monitoring. IV boluses in a patient with a pulse are reserved for experienced specialists while an infusion is established. Never inject undiluted 1 mg/mL (1:1,000) epinephrine IV.
- Fluids & Glucagon for Beta-Blocker Patients: Rapidly infuse 1 to 2 liters balanced crystalloids. Beta-blockers may contribute to refractory shock. After repeated IM epinephrine, establish a monitored IV epinephrine infusion with expert support and reassess fluids. Consider adjunctive glucagon 1–5 mg IV over five minutes, then 5–15 mcg/min, to increase cAMP independently of beta receptors; monitor for vomiting and aspiration.
- Adjuncts: After stabilization, an H1 antihistamine may relieve persistent skin symptoms. Antihistamines and corticosteroids do not reliably prevent biphasic reactions or treat shock. Do not give routine steroids; consider them after resuscitation for ongoing asthma or refractory reactions.
Neurogenic Shock: Pathophysiology & Perfusion Protocols
Neurogenic shock results from cervical or high thoracic spinal cord injury at or above T6:
- Mechanism: Loss of descending sympathetic tone causes massive arterial and venous dilation. Disruption of cardiac acceleratory fibers (T1–T4) leaves parasympathetic vagal tone unopposed.
- Classic Triad: Hypotension (SVR <800 dynes·s/), bradycardia, and warm, dry extremities with poikilothermia.
- Spinal Shock Differentiation: Spinal shock is a transient neurologic loss of reflexes and motor function below the injury; neurogenic shock is a hemodynamic collapse.
- Perfusion Targets: The 2024 AO Spine/Praxis guideline weakly suggests augmenting MAP to at least 75–80 mmHg, without active augmentation above 90–95 mmHg, for 3–7 days. Individualize the target and duration to protect cord perfusion.
- Vasoactive Agents: Use agents with dual alpha-1 and beta-1 activity (e.g., norepinephrine). Avoid pure alpha-1 agonists like phenylephrine, which trigger baroreceptor-mediated reflex bradycardia and asystole.
High-Yield Board Exam Traps & Clinical Pearls
- TBI Resuscitation Trap: Never allow permissive hypotension (SBP 80–90 mmHg) in trauma patients with concurrent TBI; maintain SBP >= 100–110 mmHg.
- Tamponade Equalization Trap: Tamponade features elevated CVP, elevated PCWP, and equalization of chamber end-diastolic pressures within 5 mmHg (RA = RVEDP = PCWP = PAD).
- Beta-Blocker Anaphylaxis Trap: Continue indicated epinephrine escalation despite beta-blocker use. Consider glucagon as an adjunct when shock remains refractory to epinephrine and fluids.
- Phenylephrine Neurogenic Trap: Avoid single-agent phenylephrine in neurogenic shock; pure vasoconstriction induces reflex bradycardia that can precipitate arrest.
A 42-year-old female who was an unrestrained driver in a high-speed motor vehicle collision is brought to the trauma intensive care unit. She is tachypneic and pale. Vital signs: blood pressure 82/56 mmHg, heart rate 136 bpm, respiratory rate 32/min, and SpO2 94% on non-rebreather mask. Laboratory assessment reveals a serum lactate of 5.8 mmol/L and an arterial base deficit of -9 mEq/L. Estimated blood loss from bilateral femur fractures and a pelvic fracture is 1,800 mL. FAST examination demonstrates free fluid in the pelvis without pericardial effusion. While awaiting emergent surgical stabilization, what is the most appropriate hemodynamic resuscitation target and strategy?
Rapidly infuse 3 liters of normal saline to achieve a normal blood pressure (systolic >= 120 mmHg) prior to surgical incision.
Initiate high-dose phenylephrine infusion to maintain a mean arterial pressure of 85 mmHg without blood products.
Implement damage control resuscitation with balanced blood component therapy (1:1:1 ratio of packed red blood cells, fresh frozen plasma, and platelets) targeting permissive hypotension with systolic blood pressure of 80 to 90 mmHg.
Target a systolic blood pressure > 110 mmHg using aggressive crystalloids and recombinant factor VIIa as the initial hemostatic agent.
A 58-year-old male with a history of hypertension and chronic stable angina managed with carvedilol receives an intravenous infusion of cefazolin prior to elective hernia repair. Within five minutes, he develops generalized urticaria, facial angioedema, stridor, and severe bronchospasm. His blood pressure plummets to 66/38 mmHg and heart rate is 58 bpm. The acute care team administers intramuscular epinephrine 0.5 mg (1:1,000) into the anterolateral thigh and initiates rapid IV crystalloid infusion. Despite repeat IM epinephrine, adequate fluid resuscitation and a monitored IV epinephrine infusion managed by the resuscitation team, his blood pressure remains 70/40 mmHg. Which adjunctive drug should be considered because of his beta-blocker therapy?
Administer intravenous glucagon 1 to 5 mg over 5 minutes, followed by a continuous infusion of 5 to 15 mcg/min.
Administer intravenous diphenhydramine 50 mg alone and wait 30 minutes for therapeutic effect.
Administer an intravenous push of 1 mg epinephrine in a 1:1,000 concentration over 30 seconds.
Initiate an esmolol infusion to reverse catecholamine-induced receptor desensitization.
A 26-year-old male is admitted following a diving accident resulting in complete C5 quadriplegia. On arrival to the ICU, his vital signs are: blood pressure 76/44 mmHg, heart rate 42 bpm (sinus bradycardia), respiratory rate 14/min, and temperature 35.4°C (95.7°F). Physical examination reveals flaccid paralysis below the clavicles and warm, dry, flushed extremities with brisk capillary refill. Pulmonary artery catheterization shows a CVP of 4 mmHg, PCWP of 6 mmHg, cardiac index of 2.1 L/min/m2, and systemic vascular resistance of 520 dynes·sec/cm5. What is the primary diagnosis, and what is the target mean arterial pressure (MAP) management goal?
Cardiogenic shock secondary to blunt cardiac trauma; target a central venous pressure of 16 mmHg with inotropic milrinone infusion.
Spinal shock; withhold all vasoactive agents because hypotension is benign and self-limiting in motor neuron injury.
Septic shock from occult aspiration pneumonia; target a mean arterial pressure >= 65 mmHg with pure alpha-1 phenylephrine infusion.
Neurogenic shock; augment MAP to at least 75–80 mmHg without active augmentation above 90–95 for 3–7 days, using an individualized vasopressor such as norepinephrine for this bradycardic patient.
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