Airway Management for a Patient with Post-Burn Contractures

Patient History and Presentation

Who is the patient and what are his chief complaints?

The patient is a gentleman, Rajan Mason by occupation, aged approximately 50 years. His chief complaint is excessive post-burn scarring at the lower part of his chin, neck, extending to the front of his chest, upper abdomen, and bilateral upper arms. This has resulted in a grossly restricted neck movement with an inability to look upward.

What is the history of the present illness?

The patient sustained burns from an oil lamp at 10 years of age. The burns involved approximately 20% of his total body surface area, including the lower part of his chin, front of neck, chest, upper abdomen, and bilateral upper arms. He was initially managed in an HTU and later in a Burns unit, being discharged after one month.

What is his surgical history related to the burns?

He gradually developed scar tissue on the burned areas. He has a history of three surgeries for post-burn contracture release under general anesthesia, with the last surgery being five years ago.

Is there any history of airway intervention?

There is no past history of airway intervention or tracheostomy.

General and Airway Examination Findings

What were the findings on general examination?

The patient was conscious and oriented, comfortably sitting with no signs of respiratory distress. He was of thin build and nourishment, with a BMI of 18.4.

What were the specific findings on airway examination?

Mouth opening: More than three fingers (inter-incisor gap > 5 cm).
Mallampati grade: Three.
Thyromental distance: Could not be assessed due to scar contracture.
Mandibular protrusion: Grade 3 (unable to protrude the lower mandible).
Neck movements: Both extension and lateral rotation are limited.
Sternomental distance: 8 cm.
Nostrils: Both were patent, though this was not initially specified using a test like the cold spatula test.

What were the findings on local examination of the neck?

Inspection: Burn scars over the lower chin, extending to the upper sternum, front of neck, laterally to the medial border of the right clavicle, and down to the umbilicus. The left clavicle is visible, but one-third of the right clavicle is covered by scar tissue. There are two contraction bands from the mentum to the right presternal area.
Palpation: The scar is non-tender, firm, and raised above the skin. The cricothyroid membrane is not palpable, and the trachea is not palpable.

How was the patency of the nostrils checked?

Patency can be checked using simple methods like the cold spatula test (observing condensation), asking the patient which side they can breathe through better, or holding a wisp of cotton in front of each nostril to see which one moves.

What is the significance of assessing the submandibular space in this patient?

Assessing the submandibular space is crucial because during laryngoscopy, the tongue needs to be displaced into this space. In this patient, scar tissue makes the area stiff and non-compliant, which will likely make displacing the tongue and achieving a good view for laryngoscopy very difficult.

What do the measured distances (inter-incisor gap, thyromental, sternomental) tell us?

Inter-incisor gap: An adequate mouth opening of > 5 cm suggests that using a direct or video laryngoscope is possible. For a supraglottic airway device, an opening of approximately 4 cm (or two finger breadths) is generally sufficient.
Sternomental distance (8 cm): This is less than the normal 12.5-13 cm, indicating restricted neck extension, which prevents achieving the "sniffing the morning air" position.
Thyromental distance: Although it couldn't be assessed here, it helps evaluate the mandibular space and the ability to displace the tongue.

Anticipated Problems and Anesthetic Concerns

What are the main anesthetic problems anticipated in this patient?

Difficult Airway: Due to contractures limiting neck movement and mouth opening, and scar tissue in the submandibular space.
Difficult Venous Access: Scarring on the upper limbs may make finding a suitable vein challenging.
Difficult Monitoring:
- ECG: Gel electrodes may not adhere to scarred skin; needle electrodes or alternative placement sites on the lower chest/abdomen may be needed.
- NIBP: A cuff may not fit on scarred upper arms; it could be placed on the lower limbs, or invasive arterial blood pressure monitoring might be required.
- Neuromuscular monitoring: Placing electrodes on scarred arms may be difficult.
Intraoperative Temperature Loss: Due to the large surface area of scarred skin.
Patient Psychology: The patient, having had three uneventful surgeries, may be casual about the risks, making thorough pre-operative counseling essential.

What is the significance of the burn having occurred 46 years ago?

The time elapsed since the burn injury is crucial for deciding the safety of using the muscle relaxant suxamethonium (succinylcholine). It is considered unsafe to use between 24 hours and up to two years post-burn due to the risk of fatal hyperkalemia. After two years, as in this case, it is generally safe to use.

Why is there concern about using muscle relaxants in burn patients?

Suxamethonium (depolarizing relaxant): Can cause a life-threatening rise in serum potassium (hyperkalemia) due to upregulation and hypersensitivity of extra-junctional acetylcholine receptors.
Non-depolarizing muscle relaxants (NDMRs): Patients may exhibit resistance, requiring higher initial doses, and the duration of action may be shortened.

How can the severity of the post-burn contracture be classified?

According to Uno's classification:

Type 1: Patient can flex the neck to bring the chin to a normal position.
Type 2: More severe contracture; patient can flex the neck, but looking up pulls the lower lip down.
Type 3 (Severe): Patient can flex the neck, but the chin is attached to the lower sternum and cannot be brought to a normal position.
Type 4: Posterior contraction.

Airway Management Plan and Intraoperative Challenges

What is the airway management plan for this patient?

The primary plan is an awake fiber-optic nasotracheal intubation. This is chosen because of the anticipated difficult airway due to contractures and scar tissue.

Why not use the same technique as in the patient's three previous surgeries?

The details of the previous anesthetics are not available. It is unknown what techniques were used or what difficulties were encountered. Furthermore, the contractures may have progressed since the last surgery, making the airway potentially more difficult now.

How will the patient be prepared for an awake fiber-optic intubation?

Pre-operative: Counsel the patient about the procedure, advise fasting, and administer anti-aspiration prophylaxis and anti-anxiolytics (e.g., pantoprazole 40 mg, alprazolam 0.5 mg).
Day of surgery: Confirm NPO status, obtain high-risk consent, check baseline electrolytes (especially potassium), and secure IV access.
Preparation for the procedure: Calculate the maximum safe dose of local anesthetic for topicalization (e.g., lidocaine 4% for nebulization, 10% spray). Use xylometazoline nasal drops for decongestion. Administer a drying agent like glycopyrrolate (0.2 mg IV).
During the procedure: Apply standard monitors, pre-oxygenate, and administer gentle, titrated sedation (e.g., fentanyl 1 mcg/kg, midazolam in small increments) while maintaining spontaneous ventilation and patient cooperation.

How is the maximum dose of local anesthetic calculated?

For a 50 kg patient, a safe dose of lidocaine for topicalization is up to 9 mg/kg with adrenaline. The total dose would be 450 mg. It's crucial to be cautious as the exact amount absorbed during topicalization is unknown.

What are some problems that can occur during fiber-optic intubation and how can they be managed?

Fogging of the scope: Clean the lens, reinsert, apply antifog solution, or administer oxygen through the suction channel to clear the lens.
Blood or secretions obscuring the view: Withdraw the scope slightly, suction the area, and re-advance. The tip can be gently touched against the mucosa to clear it.
Loss of identifiable anatomy (pink-out): Withdraw the scope slowly until familiar anatomy is visible again, then proceed.

What difficulties can arise when railroading the endotracheal tube?

The tube can get caught at various points:

Inferior turbinates: The tube may get hung up in the nasal passage.
Epiglottis or anterior commissure: The tube tip can impinge on these structures, preventing passage into the trachea.

How can tube impingement be managed?

Identify the point of impingement: Look for a bulge on the front of the neck to see where the tube is hinging, though this is difficult with contractures.
Maneuvers: Change the patient's head position or ask the patient to phonate to open the glottis.
Tube rotation: Rotate the tube 90 degrees anticlockwise before advancing. Because the rotation at the tip is less than at the hub, a more significant external rotation is needed.
Use a different tube: A reinforced (armored) tube, with its curved tip, may have a higher success rate in negotiating the glottis than a standard PVC tube.