6.4 Allergic Reactions, Anaphylaxis, Asthma & Airway Obstruction

6.4 Allergic Reactions, Anaphylaxis, Asthma & Airway Obstruction

Respiratory emergencies and immunological crises demand the most urgent, time-critical interventions in dental assisting. Because airway patency and tissue oxygenation are prerequisites for cellular survival, any process compromising alveolar ventilation—whether acute immunological laryngeal edema, inflammatory bronchial smooth muscle constriction, or mechanical foreign body aspiration—can cause irreversible hypoxic brain injury within 4 to 6 minutes. The dental assistant must master rapid recognition, pharmacological deployment, and physical airway clearance maneuvers.

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Allergic Reactions: Type I Hypersensitivity vs. Contact Dermatitis

Allergic responses occur when an individual's immune system mounts an exaggerated, pathological hypersensitivity reaction against a foreign antigen (allergen) following prior sensitization.

Immunological Classification in Dentistry

• Type I (Immediate / IgE-Mediated) Hypersensitivity: The allergen binds to antigen-specific Immunoglobulin E (IgE) antibodies bound to high-affinity receptors on tissue mast cells and circulating basophils. This cross-linking triggers rapid cellular degranulation, releasing preformed primary chemical mediators—predominantly histamine—and generating secondary lipid mediators including leukotrienes, prostaglandins, and platelet-activating factor. Symptoms erupt rapidly within seconds to minutes of exposure. Clinical manifestations range from mild cutaneous wheals to fatal systemic anaphylaxis.
• Type IV (Delayed / Cell-Mediated) Hypersensitivity: Mediated by sensitized T-lymphocytes rather than antibodies. Upon re-exposure, sensitized T-cells release inflammatory cytokines that recruit macrophages over a 24- to 72-hour period. Classic dental examples include allergic contact dermatitis or contact stomatitis triggered by chemical accelerators in latex gloves, methyl methacrylate acrylic monomers, impression components, or nickel-containing alloys.

Common Dental Allergens

• Latex: Natural rubber latex proteins harvested from Hevea brasiliensis trees, historically prevalent in examination gloves, rubber dam sheets, prophy cups, and orthodontic elastics.
• Local Anesthetics & Preservatives: True allergic reactions to modern amide local anesthetics (lidocaine, articaine, mepivacaine) are extraordinarily rare (<1% of adverse anesthetic reactions; most are psychogenic syncope or intravascular epinephrine responses). However, patients may exhibit severe hypersensitivity to sodium metabisulfite or potassium metabisulfite, the antioxidant preservative added to local anesthetic cartridges containing vasoconstrictors (epinephrine or levonordefrin) to prevent catecholamine oxidation. Bisulfite allergy is particularly prevalent among steroid-dependent asthmatic patients.
• Antibiotics: Beta-lactam antibiotics (penicillin VK, amoxicillin, ampicillin, cephalosporins) represent the single leading cause of fatal prescription drug-induced anaphylaxis in healthcare.
• Analgesics: Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs such as ibuprofen and naproxen), capable of triggering severe bronchospasm and angioedema.

Mild-to-Moderate Cutaneous Reactions and Management

Cutaneous allergic manifestations develop over minutes to hours without systemic respiratory or cardiovascular involvement:

• Urticaria (Hives): Intensely pruritic, well-circumscribed, raised erythematous wheals with blanched centers caused by localized histamine-induced histamine H1 receptor capillary vasodilation and increased vascular permeability.
• Pruritus & Erythema: Severe generalized skin itching and flushed, warm cutaneous erythema.
• Angioedema: Rapid, non-pitting edema of the deep dermis and subcutaneous or submucosal tissues, classically involving the lips, eyelids, cheeks, or tongue. If angioedema is localized without pharyngeal or laryngeal involvement, it remains a moderate reaction.
• Chairside Management: Discontinue dental treatment and remove the suspected offending allergen. Administer oral diphenhydramine (Benadryl) 25 to 50 mg for adults (1 mg/kg for pediatric patients). Keep the patient under clinical observation for a minimum of 60 minutes to ensure symptoms do not advance into systemic anaphylaxis. Provide a 3-day prescription for oral antihistamines and dismiss the patient into the care of a responsible adult.

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Acute Systemic Anaphylaxis: Life-Threatening Emergency

Anaphylaxis represents the ultimate, catastrophic clinical manifestation of Type I immediate hypersensitivity. It is an explosive, multisystemic, life-threatening crisis that can progress from initial exposure to complete cardiovascular collapse and asphyxiation within 2 to 15 minutes.

[Allergen Enters System (Penicillin, Latex, Bisulfite)]
          │
          ▼
[IgE Cross-Linking on Mast Cells & Basophils]
Massive Degranulation & Systemic Release of Histamine & Leukotrienes
          │
          ▼
┌───────────────────────┬───────────────────────┬───────────────────────┐
│      Cutaneous        │      Respiratory      │    Cardiovascular     │
│ Urticaria, Pruritus,  │ Laryngeal Edema,      │ Massive Vasodilation, │
│ Facial Angioedema,    │ Bronchospasm, Stridor,│ Fluid Extravasation,  │
│ Flushing & Tingling   │ Dyspnea & Cyanosis    │ Severe Shock / Hypot. │
└───────────────────────┴───────────────────────┴───────────────────────┘
          │
          ▼
[EMERGENCY FIRST-LINE INTERVENTION: INTRAMUSCULAR EPINEPHRINE 1:1,000]
Adult: 0.3 mg IM / Pediatric: 0.15 mg IM into Anterolateral Thigh (Vastus Lateralis)

Clinical Presentation: Multisystemic Collapse

1. Cutaneous System: Diffuse, rapidly spreading urticaria, severe pruritus of the scalp, palms, and soles, intense generalized flushing, and prominent periorbital and perioral angioedema.
2. Respiratory System: Acute swelling of the hypopharynx, epiglottis, and vocal cords (laryngeal edema), producing hoarseness, high-pitched inspiratory crowing (stridor), feeling of throat closure, and severe bronchospasm with expiratory wheezing, tachypnea, and cyanosis.
3. Cardiovascular System: Widespread systemic vasodilation combined with sudden massive leakage of intravascular plasma fluid into interstitial tissues (up to 35-50% of circulatory volume lost in minutes), producing severe hypotension (anaphylactic shock), rapid weak thready tachycardia, cardiac arrhythmias, and loss of consciousness.
4. Gastrointestinal System: Severe spasmodic abdominal cramps, nausea, vomiting, and incontinence.

The Standardized Anaphylaxis Emergency Protocol

1. Inject Epinephrine Immediately:
   • Formulation: Epinephrine 1:1,000 concentration (1 mg/mL).
   • Adult Dosage: 0.3 mg (0.3 mL) intramuscularly.
   • Pediatric Dosage: 0.15 mg (0.15 mL) intramuscularly for children 15 to 30 kg.
   • Anatomical Site: Administer immediately into the anterolateral aspect of the middle third of the thigh (vastus lateralis muscle). The vascularity of the vastus lateralis achieves significantly faster peak arterial drug concentrations than the deltoid or subcutaneous routes.
   • Pharmacological Action: Alpha-1 receptor stimulation causes intense peripheral vasoconstriction, reversing profound hypotension and reducing laryngeal edema; beta-1 stimulation enhances cardiac contractility; beta-2 stimulation produces powerful bronchial smooth muscle dilation and shuts down further mast cell mediator release.
2. Activate EMS (Call 911): Inform dispatch that an adult or child is in acute anaphylactic shock.
3. Position the Patient: Place the patient supine with the lower extremities elevated to restore venous return and preserve coronary and cerebral perfusion. (If respiratory distress is the overwhelming symptom and lying flat makes breathing impossible, allow a semi-reclined posture while continuously monitoring blood pressure.)
4. Administer High-Flow Oxygen: Deliver 100% oxygen via a non-rebreather reservoir mask at 10 to 15 L/min. Be prepared to support ventilation using a bag-valve-mask (BVM).
5. Repeat Epinephrine if Refractory: If severe hypotension, airway edema, or respiratory distress persists or worsens after 5 to 15 minutes, administer a repeat dose of intramuscular epinephrine 1:1,000.
6. Secondary Adjunctive Medications: Administered ONLY AFTER epinephrine has been injected and emergency services summoned:
   • Antihistamines: Diphenhydramine 50 mg IM or slow IV (blocks further histamine H1 binding).
   • Corticosteroids: Hydrocortisone 100 mg IM/IV or dexamethasone 4-8 mg IM/IV. Corticosteroids act slowly (over hours) and do not treat acute symptoms. They were long given to prevent biphasic anaphylaxis, a recurrence hours after apparent recovery (usually within 12 hours, occasionally up to 72), but current anaphylaxis practice parameters find little evidence that they prevent it; observation after epinephrine is what matters.

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Asthma and Acute Bronchospasm

Asthma is a chronic inflammatory disorder of the tracheobronchial tree characterized by bronchial hyperresponsiveness, smooth muscle bronchospasm, mucosal inflammation/edema, and excessive secretion of thick, viscous mucus.

Operatory Triggers and Pathophysiology

In dental operatories, acute asthmatic attacks are commonly triggered by psychological stress, inhalation of dental aerosols containing tooth dust or silica, cold ambient operatory air, eugenol fumes, methyl methacrylate monomer, or bisulfite preservatives in local anesthetic cartridges. During an attack, inflammatory mediators cause contraction of bronchial smooth muscle, narrowing the lower airways. Because airways naturally narrow during expiration, the patient experiences severe difficulty expelling air from the lungs, leading to air trapping, hyperinflation, and ventilation-perfusion mismatch.

Clinical Presentation

• Symptoms: Acute dyspnea (shortness of breath), tightness in the chest, persistent non-productive coughing, and audible expiratory wheezing.
• Physical Signs: Tachypnea (respirations >25-30 bpm), tachycardia, prominent use of accessory muscles of respiration (sternocleidomastoid retractions and intercostal indrawing), nasal flaring, and cyanosis of the nail beds and lips.
• The "Silent Chest" Emergency: In severe, catastrophic bronchospasm, air movement becomes so minimal that wheezing completely disappears. A silent chest accompanied by extreme dyspnea indicates impending respiratory arrest and requires instant emergency escalation.

Step-by-Step Chairside Asthma Protocol

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Foreign Body Airway Obstruction (FBAO)

Foreign body airway obstruction (choking) represents a constant operational hazard in dental practice. The combination of a reclined patient, slippery saliva-coated instruments, impaired swallowing reflexes from local anesthesia, and manipulation of miniature dental items in the posterior oral cavity creates high risk for accidental aspiration or ingestion.

High-Risk Dental Armamentarium and Materials

• Small restorative castings: Cast gold or porcelain crowns, inlays, onlays, and veneers during trial seating or cementation.
• Endodontic instruments: Miniature endodontic files, reamers, and gutta-percha points.
• Implant hardware: Miniature implant hex screwdrivers, healing abutments, and fixation screws.
• Operatory sundries: Broken dental bur heads, matrix band wedges, rubber dam clamps, cotton rolls, and tooth fragments during surgical extractions.

Prevention Protocols: The Auxiliary Standard of Care

[Primary Prevention Strategies for the Dental Team]
  ├── 1. Rubber Dam Isolation: Mandatory for all endodontic therapy;
  │      creates an impenetrable barrier protecting the pharynx
  ├── 2. Floss Ligatures (Safety Leashes): 12-18 inch floss tied to
  │      rubber dam clamps, endo files, implant screwdrivers
  ├── 3. Gauze Throat Screens: 2x2 or 4x4 gauze unfolded across anterior
  │      tonsillar pillars during surgical extractions or cementation
  └── 4. Proactive HVE: Dental assistant maintains high-volume suction
         tip directly adjacent to operative site to capture dropped items

Clinical Differentiation: Partial vs. Severe Airway Obstruction

Partial Airway Obstruction with Good Air Exchange

• Clinical Signs: The patient is conscious, highly anxious, able to speak or make vocal sounds, coughs forcefully, and breathes with mild wheezing between coughs.
• Management: DO NOT INTERFERE WITH THE PATIENT'S EFFORTS. Do not deliver back blows or abdominal thrusts, as physical interference can dislodge a partially occluding object into an irreversible complete impaction. Keep the patient seated upright, provide calm encouragement, and instruct them to cough forcefully until the item is expelled into the oral cavity where it can be retrieved with HVE or cotton pliers.

Severe or Complete Airway Obstruction

• Clinical Signs: The patient displays the universal choking distress sign (both hands clutching the throat and neck); is completely unable to speak, breathe, or cough; exhibits inspiratory stridor (high-pitched crowing) or silent chest excursions; displays rapid facial and lip cyanosis; and exhibits widening eyes of panic, progressing to unconsciousness within 30 to 60 seconds if untreated.

Emergency Physical Rescue Protocols

1. Conscious Adult or Child Choking Victim: Back Blows and Abdominal Thrusts

The 2025 AHA guidelines changed the sequence. For a responsive adult or child with severe obstruction, give repeated cycles of 5 back blows followed by 5 abdominal thrusts until the object comes out or the person becomes unresponsive. (Earlier guidelines used abdominal thrusts alone.)

1. Back blows: Stand slightly behind and to the side, support the chest with one hand, lean the patient forward, and give up to 5 firm blows between the shoulder blades with the heel of the other hand.
2. Abdominal thrusts: Stand behind the patient and wrap your arms around the waist. Place the thumb side of a fist on the midline slightly above the navel and well below the tip of the xiphoid process, grasp the fist with the other hand, and give up to 5 quick inward-and-upward thrusts.
3. Each blow and each thrust is a separate attempt to force the object out.
4. Keep alternating 5 and 5 until the object is expelled or the patient becomes unresponsive.

2. Obese or Late-Term Pregnant Patients: Chest Thrust Protocol

If the patient is in the late stages of pregnancy or is morbidly obese, the rescuer cannot encircle the abdomen, and abdominal thrusts risk fatal hepatic laceration or fetal injury. Rescuers deliver chest thrusts in place of the abdominal thrusts (back blows still alternate with them): stand behind the patient, wrap arms under the axillae, place the thumb side of the fist against the center of the sternum (mid-breastbone, avoiding the xiphoid process), grasp the fist with the second hand, and deliver forceful, straight backward thrusts.

3. Unresponsive / Unconscious Choking Patient Sequence

1. Lower and Support: Carefully support the patient and lower them to a flat, firm surface (the floor or a fully reclined dental chair).
2. Activate EMS (Call 911): Direct an auxiliary to call 911 immediately.
3. Initiate CPR Chest Compressions: Immediately begin cardiopulmonary resuscitation starting with 30 chest compressions at a rate of 100 to 120 per minute. Compressions generate substantial intrathoracic pressure that can dislodge foreign bodies.
4. Open Airway and Inspect Oral Cavity: After 30 compressions, open the patient's mouth using the tongue-jaw lift. Look inside the pharynx:
   • If the object is clearly visible, perform a careful hooked finger sweep to extract it.
   • If no object is visible, do not perform a sweep.
5. Attempt Rescue Breaths: Deliver 2 rescue breaths using a pocket mask or BVM. If the chest does not rise, reposition the head (re-tilt chin) and attempt 2 breaths again.
6. Continue 30:2 Cycles: Continue uninterrupted cycles of 30 chest compressions, visual oral inspection, and attempted ventilations until the object is successfully dislodged, spontaneous respirations return, or emergency medical personnel arrive.

Mandatory Legal and Radiographic Protocol for Lost Objects

If a small dental object (casting, file, bur) slips into the posterior pharynx and disappears without confirmation of recovery, the dental team must act under the legal and medical presumption that the object has entered a vital tract:

• Aspiration vs. Ingestion: The object may have been aspirated into the tracheobronchial tree (typically entering the wider, steeper, more direct right mainstem bronchus) or swallowed into the gastrointestinal tract.
• Mandatory Medical Referral: The patient must be immediately escorted to an outpatient imaging center or hospital emergency facility for posteroanterior (PA) and lateral chest radiographs as well as abdominal radiographs.
• An aspirated foreign body is a surgical emergency: if not retrieved promptly via bronchoscopy, it causes atelectasis, severe lung abscess, chronic bronchiectasis, or fatal sepsis. Detailed documentation of the event, patient notification, and imaging referrals must be recorded contemporaneously in the patient's dental record.