8.5 Immune Disorders, Trauma, Burns, Shock, Substance Use & Organ Transplantation
Key Takeaways
- Perioperative anaphylaxis often appears first as hypotension and tachycardia with bronchospasm; epinephrine is first-line, antihistamines and steroids are second-line add-ons, and tryptase is drawn soon afterward.
- Latex allergy ranges from irritant dermatitis to Type IV contact reactions to IgE-mediated anaphylaxis; spina bifida, repeated surgery, and cross-reacting foods (banana, avocado, kiwi, chestnut) raise risk, and a latex-safe setup prevents exposure.
- HIV transmission risk after a percutaneous exposure is about 0.3%, AIDS means a CD4 count below 200 cells/mm³ or an AIDS-defining illness, and ritonavir or cobicistat can intensify midazolam and fentanyl.
- Shock is hypovolemic, distributive, cardiogenic, or obstructive; burn care uses the rule of nines, Parkland-based fluids adjusted to urine output, co-oximetry for carbon monoxide, and avoidance of succinylcholine after the first 24 hours.
- A transplanted heart is denervated, so it ignores atropine and vagal reflexes but responds to direct-acting drugs such as epinephrine and isoproterenol; tacrolimus and cyclosporine can injure the kidneys.
8.5 Immune Disorders, Trauma, Burns, Shock, Substance Use & Organ Transplantation
The ASATT content outline groups immune disorders (anaphylaxis, AIDS/HIV, and latex allergy) with additional topics: trauma, burns, shock, substance abuse, and organ transplants. These patients often arrive with unstable physiology, unusual drug responses, or special equipment and infection control needs.
Immune Disorders
Anaphylaxis
Anaphylaxis is a severe, rapid, potentially fatal systemic allergic reaction. In classic anaphylaxis, a sensitized patient's IgE antibodies trigger mast cells and basophils to release histamine, tryptase, leukotrienes, and other mediators. Non-IgE reactions can look identical and are treated the same way.
- Common perioperative triggers: Neuromuscular blocking agents, antibiotics (especially cephalosporins such as cefazolin), chlorhexidine, latex, sugammadex, and blue dyes used for lymphatic mapping.
- Signs under anesthesia: Hypotension and tachycardia are often the first signs. Bronchospasm raises peak airway pressure and produces an obstructive capnogram, while flushing, hives, and swelling may be hidden under drapes. End-tidal CO2 can fall as cardiac output drops.
| Step | Management of Perioperative Anaphylaxis |
|---|---|
| 1. Stop and call | Stop the suspected agent (for example, the antibiotic infusion or latex contact) and call for help |
| 2. Oxygen and airway | Give 100% oxygen and secure the airway if needed |
| 3. Epinephrine | The first-line drug: small IV boluses titrated by the anesthesia provider during anesthesia, or 0.3 to 0.5 mg IM in adults |
| 4. Volume | Rapid IV fluid boluses and leg elevation for severe hypotension |
| 5. Second-line drugs | Bronchodilators, antihistamines (H1 and H2 blockers), and corticosteroids, which do not replace epinephrine |
| 6. Refractory shock | Epinephrine infusion and other vasopressors; glucagon for patients taking beta-blockers |
| 7. Follow-up | Serum tryptase drawn soon after the reaction (ideally within about 1 to 2 hours) and referral for allergy testing |
Latex Allergy
| Reaction Type | Mechanism | Presentation |
|---|---|---|
| Irritant contact dermatitis | Not immune-mediated | Dry, cracked skin where gloves are worn |
| Allergic contact dermatitis (Type IV) | Delayed T-cell reaction to chemical additives in latex products | Rash hours to days after contact (often 24 to 72 hours) |
| Immediate hypersensitivity (Type I) | IgE antibodies to latex proteins | Hives, bronchospasm, and anaphylaxis |
- Higher-risk groups: Children with spina bifida or many prior surgeries, health care workers, and people allergic to foods that cross-react with latex, such as banana, avocado, kiwi, and chestnut.
- Timing clue: Latex anaphylaxis may appear later in a case, after latex touches mucous membranes or the surgical wound, rather than within minutes of an IV drug.
- Latex-safe setup: Post signs, use a latex-free cart, and check gloves, tourniquets, blood pressure cuffs, catheters, drains, and masks for latex. Facilities often schedule these patients as the first case of the day.
AIDS and HIV
HIV is a bloodborne retrovirus that destroys CD4 T cells. AIDS is diagnosed when the CD4 count falls below 200 cells/mm³ or an AIDS-defining illness develops.
- Occupational risk: The average transmission risk after a percutaneous exposure to HIV-infected blood is about 0.3%, far lower than for hepatitis B. Standard Precautions and prompt post-exposure evaluation protect staff.
- Drug interactions: Antiretroviral boosters such as ritonavir and cobicistat strongly inhibit the CYP3A4 enzyme and can intensify and prolong midazolam and fentanyl.
- Other concerns: Opportunistic infections (suspected tuberculosis calls for airborne precautions), low platelet counts, cardiomyopathy, and peripheral neuropathy, which is documented before regional anesthesia.
Trauma, Shock & Burns
Shock
Shock is inadequate oxygen delivery to tissues. The four major categories are:
| Type | Examples | Typical Findings |
|---|---|---|
| Hypovolemic | Hemorrhage, burns, dehydration | Low filling pressures, tachycardia, cool skin |
| Distributive | Sepsis, anaphylaxis, neurogenic shock | Low systemic vascular resistance; neurogenic shock from a high spinal cord injury causes hypotension with bradycardia |
| Cardiogenic | Myocardial infarction, severe heart failure | Pump failure with high filling pressures |
| Obstructive | Tension pneumothorax, cardiac tamponade, massive pulmonary embolism | Blocked filling or outflow of the heart |
The American College of Surgeons' ATLS program grades hemorrhage by estimated blood loss: Class I up to 15% of blood volume, Class II 15% to 30%, Class III 30% to 40% (blood pressure usually falls), and Class IV more than 40%.
Trauma Resuscitation
- Damage control resuscitation: Control bleeding early, limit crystalloid, and give plasma, platelets, and red cells in a balanced ratio (often close to 1:1:1) through a massive transfusion protocol.
- The lethal triad: Hypothermia, acidosis, and coagulopathy worsen one another, so every fluid and blood product is warmed.
- Tranexamic acid: The CRASH-2 trial found benefit when it was started within 3 hours of injury.
- Airway: Assume a full stomach and a possible cervical spine injury, with manual in-line stabilization during intubation.
- Technologist setup: Rapid infuser and fluid warmer, massive transfusion coolers, cell salvage when appropriate, point-of-care testing (blood gases, TEG or ROTEM), and a difficult airway cart.
Burns
- Size: The adult rule of nines assigns 9% to the head, 9% to each arm, 18% to the front of the trunk, 18% to the back, 18% to each leg, and 1% to the perineum.
- Fluids: The classic Parkland formula gives 4 mL/kg per percent of total body surface area (TBSA) burned of lactated Ringer's over 24 hours, with half in the first 8 hours after the burn. Many burn centers start lower and adjust to urine output (about 0.5 mL/kg/h in adults).
- Inhalation injury: Singed nasal hair, soot in the mouth, hoarseness, or stridor call for early intubation before swelling closes the airway.
- Carbon monoxide: Standard pulse oximetry reads carboxyhemoglobin as oxyhemoglobin and can look falsely normal, so co-oximetry is needed; treatment is 100% oxygen.
- Muscle relaxants: Succinylcholine is generally avoided from about 24 hours after a major burn until healing, because extra acetylcholine receptors can cause life-threatening hyperkalemia. Burned patients often need larger doses of non-depolarizing blockers.
- Heat loss: Warm the room and use warming devices, because burned skin cannot hold in heat.
Substance Use Disorders
| Substance | Acute Intoxication | Chronic Use and Withdrawal |
|---|---|---|
| Alcohol | Lowers anesthetic requirements; aspiration risk | Raises requirements through cross-tolerance; withdrawal can progress to seizures and delirium tremens; possible cardiomyopathy and cirrhosis |
| Opioids | Respiratory depression | Tolerance raises analgesic needs; naloxone can trigger acute withdrawal; methadone can prolong the QT interval |
| Cocaine and methamphetamine | Hypertension, tachycardia, dysrhythmias, coronary vasospasm, and myocardial ischemia | Pure beta-blockers have traditionally been avoided in acute cocaine toxicity because of concern about unopposed alpha stimulation; benzodiazepines and vasodilators are common first choices |
| Cannabis | Tachycardia and airway irritation when smoked | May increase anesthetic requirements in regular users |
For the technologist, substance use also means drug diversion prevention: securing controlled substances, using tamper-resistant waste containers, and reporting concerns as described in the professional standards section.
Organ Transplantation
Transplant Recipients
- Immunosuppression: Drugs such as tacrolimus, cyclosporine, mycophenolate, and corticosteroids prevent rejection. Tacrolimus and cyclosporine can cause kidney injury and hypertension, and long-term steroid users may need stress-dose steroids as ordered.
- Infection prevention: Strict aseptic technique for every line and airway device matters in immunosuppressed patients. Some recipients need irradiated or leukoreduced (CMV-safe) blood products.
- The denervated transplanted heart: The nerves to the donor heart are cut, so the resting heart rate is often faster (about 90 to 110 beats per minute), and the heart does not respond to vagal reflexes or to atropine or glycopyrrolate. It does respond to direct-acting drugs such as epinephrine and isoproterenol, while indirect agents such as ephedrine have a weaker effect. Cardiac output depends heavily on adequate preload.
Organ Donors
After brain death, donors often develop diabetes insipidus (large urine losses), hypotension, hypothermia, and electrolyte disturbances. The team supports blood pressure, oxygenation, fluids, and temperature to protect the organs until recovery.
A patient with burns over 40% of total body surface area 10 days ago returns for excision and grafting. Which neuromuscular blocker plan fits burn pathophysiology?
Ten minutes after a cefazolin infusion starts under general anesthesia, the patient develops severe hypotension, tachycardia, and rising peak airway pressures with a sloped capnogram. After stopping the antibiotic and giving 100% oxygen, what is the first-line drug treatment?
A patient who received a heart transplant 3 years ago develops bradycardia with hypotension during surgery. Why would atropine be expected to have little effect?