What is the cause of decompensation in a patient with a non-displaced fracture of the left humerus, who develops difficulty breathing, hypotension, and bilateral wheezing after placement of two large intravenous (IV) catheters and a bladder catheter, with a blood pressure of 76/52?

Anaphylaxis to Intravenous Agents

This patient is experiencing anaphylaxis, most likely triggered by one of the intravenous agents administered (IV catheters placement or bladder catheter materials/antiseptics), presenting with the classic triad of hypotension (76/52 mmHg), bronchospasm (bilateral wheezing), and cutaneous manifestations (diffuse urticarial rash). 1

Clinical Presentation Analysis

The timing and constellation of symptoms are pathognomonic for anaphylaxis:

• Cardiovascular collapse occurred within 20 minutes of IV/catheter placement, consistent with the typical onset window for anaphylactic reactions to procedural agents 1
• Hypotension (76/52 mmHg) represents cardiovascular collapse, seen in 50.8% of allergic anaphylaxis cases 1
• Bilateral wheezing indicates bronchospasm, present in 39.8% of allergic anaphylaxis 1
• Diffuse urticarial rash represents cutaneous involvement, occurring in 71.9% of allergic anaphylaxis 1

Most Likely Causative Agents

The temporal relationship points to substances administered during the procedure 1:

• Latex from gloves or catheters (reactions can occur within minutes to an hour) 1
• Chlorhexidine used for skin antisepsis during catheter placement 1
• IV colloids if administered for volume resuscitation 1
• Antibiotics if given prophylactically (though not mentioned in this case) 2

The American Academy of Otolaryngology-Head and Neck Surgery confirms that cardiovascular involvement with hypotension or cardiovascular collapse requires immediate epinephrine administration 3

Immediate Management Algorithm

Step 1: Administer epinephrine immediately - this is the only effective first-line treatment 1, 3:

• 50 mcg IV (0.5 mL of 1:10,000 solution) given the presence of IV access and cardiovascular collapse 1
• Repeat every 5-15 minutes if hypotension or bronchospasm persists 1
• Consider starting an epinephrine infusion if multiple doses are required 1

Step 2: Remove all potential causative agents 1:

• Remove latex gloves if present
• Discontinue any IV colloids
• Remove chlorhexidine-soaked materials

Step 3: Aggressive fluid resuscitation 1:

• Administer 0.9% saline or lactated Ringer's solution at high rate through large-bore IV catheter
• Large volumes may be required due to massive vasodilation 1

Step 4: Airway management 1:

• Administer 100% oxygen
• Prepare for intubation given bilateral wheezing and potential for laryngeal edema 1
• Immediate referral to someone with expertise in surgical airway management if oropharyngeal edema develops 1

Step 5: Secondary medications (never delay epinephrine for these) 1, 3:

• Chlorphenamine 10 mg IV 1
• Hydrocortisone 200 mg IV 1
• For persistent bronchospasm: IV salbutamol infusion, consider aminophylline or magnesium sulfate 1

Step 6: Vasopressor support if needed 1:

• If blood pressure doesn't recover despite epinephrine infusion, add metaraminol or other vasopressor 1

Diagnostic Confirmation

Obtain mast cell tryptase levels at specific time points 1:

• Initial sample as soon as feasible (don't delay resuscitation)
• Second sample at 1-2 hours after symptom onset
• Third sample at 24 hours or in convalescence for baseline comparison 1

Critical Pitfalls to Avoid

• Never delay epinephrine administration while giving antihistamines or corticosteroids - these do not prevent biphasic reactions and are not first-line therapy 1, 3
• Do not assume intramuscular route only - with established IV access and cardiovascular collapse, IV epinephrine (50 mcg doses) is reasonable and faster-acting 1
• Monitor for biphasic anaphylaxis - occurs in 1-7% of patients, with risk factors including severe initial presentation and requiring >1 dose of epinephrine 3
• Failure to recognize anaphylaxis due to absence of cutaneous signs in some cases - the absence of rash does not exclude anaphylaxis 1

Why Not Other Diagnoses

• Fat embolism from humeral fracture would not cause urticarial rash and typically presents 24-72 hours post-injury
• Pulmonary embolism would not explain the diffuse urticarial rash or bilateral wheezing pattern
• Tension pneumothorax would present with unilateral findings and no rash
• Vasovagal syncope would show bradycardia without pruritus, not tachycardia with urticaria 3

The combination of rapid onset after procedural intervention, hypotension, bronchospasm, and urticaria makes anaphylaxis the definitive diagnosis requiring immediate epinephrine administration 1, 3, 4.