7.4 Emergency Airway, Anesthesia & Oncology Screening

7.4 Emergency Airway, Anesthesia & Oncology Screening

Core Surgical Rule: In a 'Cannot Intubate, Cannot Ventilate' (CICV) crisis, stop repeated, futile laryngoscopy attempts. Transition immediately to front-of-neck access: surgical cricothyroidotomy through the cricothyroid membrane. Furthermore, never add adrenaline to local anesthetics when infiltrating end-artery structures (digits, penis, ears, nose), as profound vasospasm precipitates ischemic gangrene and autoamputation.

Clinical Officers in Kenyan district and sub-county hospitals routinely encounter critical airway loss, perform minor surgical procedures under local anesthesia, and serve on the frontlines of national cancer early-detection programs. Mastery of emergency surgical airway access, local anesthetic safety, toxicity resuscitation, and cancer screening guidelines is essential for clinical practice.

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1. Emergency Surgical Airway: CICV & Surgical Techniques

The 'Cannot Intubate, Cannot Ventilate' (CICV) scenario occurs when endotracheal intubation fails and oxygenation via face mask and supraglottic airway (LMA) is impossible. Without immediate intervention, severe hypoxemia precipitates irreversible anoxic brain injury and cardiac arrest within 3 to 4 minutes.

                               ['CANNOT INTUBATE, CANNOT VENTILATE' (CICV)]
                                                     │
                                                     ▼
                                   [Declare Emergency Front-of-Neck Access]
                                                     │
                     ┌───────────────────────────────┴───────────────────────────────┐
                     ▼                                                               ▼
        [Adults & Children >= 10-12 yrs]                                [Children < 10-12 yrs]
          **SURGICAL CRICOTHYROIDOTOMY**                                 **NEEDLE CRICOTHYROIDOTOMY**
     - Scalpel-Finger-Bougie Technique                             - 12-14G IV cannula through membrane
     - Transverse stab in cricothyroid membrane                    - High-pressure jet ventilation
     - Railroad size 6.0 cuffed ETT over bougie                    - Temporary oxygenation (max 30-45 min)
     - Definitive cuffed airway secured                            - Avoids subglottic stenosis risk

Anatomical Landmarks: Cricothyroid Membrane versus Tracheal Rings

The cricothyroid membrane lies between the inferior border of the thyroid cartilage (laryngeal prominence) and the superior border of the cricoid cartilage. It measures approximately 9 to 10 mm vertically and 10 mm horizontally. It is subcutaneous, avascular, and lacks overlying major vessels or glandular tissue, making it the ideal emergency portal. In contrast, the 2nd and 3rd tracheal rings are crossed by the vascular thyroid isthmus and surrounded by anterior jugular venous plexuses; formal tracheostomy at this level is strictly an elective or semi-elective operative procedure.

Scalpel-Finger-Bougie Technique (Step-by-Step)

1. Position & Identify: Extend the neck (unless cervical spine trauma is suspected). Palpate the thyroid cartilage, slide index finger inferiorly into the cricothyroid depression, and stabilize the larynx with the non-dominant thumb and middle finger.
2. Transverse Incision: Make a 2 to 3 cm transverse stab incision through the skin and cricothyroid membrane using a #10 or #11 scalpel blade, keeping the blade horizontal.
3. Dilate & Guide: Turn the scalpel blade 90° or insert the tip of the gloved little finger into the tracheal lumen to maintain the opening. Introduce a coudé-tipped tracheal bougie angled caudally into the trachea; palpable tracheal 'clicks' confirm intratracheal position.
4. Railroad Tube: Advance a lubricated size 6.0 mm cuffed endotracheal tube or small tracheostomy tube over the bougie into the airway. Inflate the cuff, confirm bilateral breath sounds and end-tidal CO2, and secure the tube.

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2. Local Anesthetic Pharmacology & Safe Dosing Calculations

Local anesthetics block voltage-gated sodium (Na+) channels on axonal membranes, arresting sodium influx and halting action potential conduction along sensory nerves.

Chemical Classification: Amides versus Esters

• Amino-Amides: Contain an 'amide' linkage; metabolized primarily by hepatic cytochrome P450 enzymes. Mnemonic: all amides contain the letter 'i' twice in their generic name (Lidocaine, Bupivacaine, Prilocaine, Ropivacaine).
• Amino-Esters: Contain an 'ester' linkage; rapidly hydrolyzed by circulating plasma pseudocholinesterases. Generic names contain the letter 'i' only once (Procaine, Tetracaine, Cocaine, Benzocaine).

Concentration-to-Milligram Conversion Rules

• A 1% solution contains 1 g / 100 mL = 10 mg/mL.
• A 2% solution contains 2 g / 100 mL = 20 mg/mL.
• A 0.5% solution contains 0.5 g / 100 mL = 5 mg/mL.
• Clinical Example: For a 60 kg adult receiving plain 1% Lidocaine, the maximum safe dose is 60 kg * 3 mg/kg = 180 mg, which equals 180 mg / (10 mg/mL) = 18 mL.

The End-Artery Vasoconstrictor Contraindication

Adrenaline (1:200,000 concentration = 5 mcg/mL) is added to local anesthetics to induce local vasoconstriction, which reduces operative bleeding, slows systemic absorption, decreases peak plasma toxicity, and prolongs anesthetic duration.

ABSOLUTE CONTRAINDICATION: Adrenaline is strictly prohibited in anatomical territories supplied by end-arteries lacking collateral circulation: the fingers, toes, penis, ear pinna, and tip of the nose. Epinephrine-induced alpha-1 vasospasm in terminal digital arteries induces prolonged ischemia, dry gangrene, and autoamputation. Digital ring blocks must always be performed using plain 1% or 2% Lidocaine.

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3. Local Anesthetic Systemic Toxicity (LAST): Presentation & Intralipid Protocol

LAST is a life-threatening complication resulting from accidental direct intravascular injection or rapid systemic absorption of excessive doses. Bupivacaine is particularly cardiotoxic due to slow dissociation from cardiac sodium channels.

                     LOCAL ANESTHETIC SYSTEMIC TOXICITY (LAST) CASCADE

      EARLY CNS SYMPTOMS                     CNS EXCITATION & COLLAPSE              CARDIOVASCULAR COLLAPSE
   ┌─────────────────────┐                   ┌─────────────────────┐                ┌─────────────────────┐
   │ Circumoral numbness │                   │ Muscle twitching    │                │ Bradycardia, Blocks │
   │ Metallic taste      │ ────────────────► │ Generalized Tonic-  │ ─────────────► │ Ventricular Arrhyth │
   │ Tinnitus, dizziness │                   │   Clonic Seizures   │                │ Hypotension, Shock  │
   │ Blurred vision      │                   │ Coma, Apnea         │                │ Asystole            │
   └─────────────────────┘                   └─────────────────────┘                └─────────────────────┘

Emergency Management Protocol for LAST

1. Stop Injection Immediately: Halt the local anesthetic administration and call for the resuscitation team and the LAST rescue cart.
2. Airway & 100% Oxygen: Hyperventilate with 100% oxygen. Preventing hypoxia, hypercapnia, and metabolic acidosis is paramount: acidosis increases the un-ionized free fraction of local anesthetic and worsens myocardial toxicity.
3. Seizure Suppression: Administer intravenous Benzodiazepines (e.g., Midazolam 0.05–0.1 mg/kg IV). Avoid propofol if hemodynamic instability or hypotension is present.
4. Resuscitation Modifications: Initiate ACLS. Avoid vasopressin, calcium channel blockers, and beta-blockers. Reduce individual Epinephrine boluses to < 1 mcg/kg (e.g., 10–50 mcg in adults) rather than standard 1 mg doses, as large doses worsen ventricular arrhythmias.
5. Specific Antidote: 20% Intravenous Lipid Emulsion (Intralipid):
   • Mechanism ('Lipid Sink'): Lipid droplets capture lipophilic local anesthetic molecules from plasma and myocardial tissue, driving clearance; simultaneously provides high-energy fatty acids to fuel failing myocardial mitochondria.
   • Bolus: 1.5 mL/kg IV bolus of 20% Lipid Emulsion over 1 minute (~100 mL for a 70 kg adult).
   • Infusion: Continuous IV infusion at 0.25 mL/kg/min (~18 mL/min for 70 kg adult).
   • Persistent Asystole: Repeat bolus once or twice every 3–5 minutes; double infusion to 0.5 mL/kg/min.
   • Continue infusion for at least 10 minutes after hemodynamic stability is achieved (maximum cumulative dose: 10–12 mL/kg over 30 minutes).

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4. Kenya National Cancer Screening Guidelines & Surgical Oncology Principles

Cancer represents the second leading cause of non-communicable disease mortality in Kenya. The Ministry of Health National Cancer Screening Guidelines mandate structured screening protocols to shift cancer detection to early, curable stages.

Breast Cancer Screening & The Triple Assessment

Breast cancer is the most frequently diagnosed cancer among Kenyan women.

• Kenya Screening Recommendations:
  • Average-Risk Women (25 to 49 years): Annual Clinical Breast Examination (CBE) by a trained health worker; monthly Breast Self-Awareness/Examination (BSE).
  • Average-Risk Women (50 to 74 years): Biennial (every 2 years) screening mammography combined with annual CBE.
  • High-Risk Women (BRCA mutations, 1st-degree relative diagnosed < 50 years): Annual clinical breast examination and annual screening MRI or mammography starting at age 30 (or 5–10 years prior to the youngest affected relative).

                              [TRIPLE ASSESSMENT OF BREAST LUMPS]

         1. CLINICAL EXAMINATION      2. DIAGNOSTIC IMAGING           3. HISTOPATHOLOGY
         - Detailed bilateral exam    - Age < 35 years: ULTRASOUND    - CORE NEEDLE BIOPSY
         - Nipple, skin, axillary       (Dense fibroglandular tissue)   (Preserves architecture,
           lymph nodes                - Age >= 35 years: MAMMOGRAPHY    differentiates in situ vs
                                        (+/- Ultrasound)                invasive; ER/PR/HER2)

         * Sensitivity > 99% when all three diagnostic modalities are concordant.
         * Core needle biopsy is strictly preferred over FNAC (which gives cytology only).

Colorectal Cancer Screening in Kenya

Colorectal cancer incidence is rising rapidly across Kenya, presenting predominantly in individuals aged 45 to 65 years.

• Target Population: Average-risk asymptomatic adults beginning at age 45 to 50 years through age 75.
• Screening Modalities:
  • Annual Fecal Immunochemical Test (FIT) or high-sensitivity Guaiac Fecal Occult Blood Test (gFOBT). Any positive result mandates diagnostic optical colonoscopy.
  • Optical Colonoscopy every 10 years (the gold standard for direct mucosal visualization and immediate therapeutic polypectomy).
  • Flexible Sigmoidoscopy every 5 years (where colonoscopy is unavailable).
• High-Risk Surveillance: Patients with Lynch syndrome (HNPCC), Familial Adenomatous Polyposis (FAP), or long-standing inflammatory bowel disease require specialized colonoscopic surveillance beginning in adolescence or early adulthood (e.g., FAP surveillance starting at age 10–12 years; Lynch syndrome starting at age 20–25 years).