Assessing Vocal Cord Function Post-Surgery: A Guide for Anesthesiologists

Ink & Air

Vocal cord assessment after surgery is critical in anesthesia, as intubation and airway management can affect vocal cord integrity. This review integrates anatomy, physiology, clinical practice, and diagnostic tools, emphasizing diverse patient populations and resource-limited settings.

Anatomy and Physiology of the Vocal Cords

• Vocal Cord Structure
• Mucosal folds covering the thyroarytenoid muscles
• Supported by cricoid and thyroid cartilages
• Innervation
• Recurrent laryngeal nerve (RLN): motor control of most intrinsic laryngeal muscles
• Superior laryngeal nerve (SLN): sensation and cricothyroid function
• Function
• Vibration produces sound
• Controlled by airflow from lungs and intrinsic laryngeal muscles
• Anesthesia Relevance
• Intubation may cause trauma, edema, or nerve injury
• Special risk groups: pediatric (smaller airways), geriatric (reduced elasticity), neurological patients
• Basic Science Integration
• RLN vulnerability during thyroidectomy and neck surgeries
• Anatomical variations across age and comorbidities affect intubation strategies

Clinical Observations

• Key Signs
• Hoarseness or dysphonia: may indicate RLN/SLN dysfunction
• Stridor or breathing difficulty: suggests obstruction or bilateral paralysis
• Weak cough: impaired glottic closure and airway protection
• Dysphagia: SLN injury increasing aspiration risk
• Clinical Integration
• Assess voice quality 1–2 hours post-extubation
• Pediatric patients: monitor for stridor or weak cry
• Geriatric/neurological patients: bedside swallow test for aspiration
• Documentation: note symptoms (e.g., hoarse voice, weak cough) in chart
• Resource-limited settings: rely on visual inspection and early ENT referral

Patient Interviews

• Patient-Reported Complaints
• Hoarseness, vocal fatigue, difficulty projecting voice
• Acute vs delayed onset of symptoms
• Daily communication and cultural impact
• Clinical Integration
• Structured questions (“Does your voice tire after speaking?”)
• Conduct interviews within 24 hours post-surgery
• Professional voice users: ask about pitch range and stamina
• Use translated questionnaires for multilingual patients
• Repeat interviews at 48–72 hours if symptoms persist

Maximum Phonation Time (MPT)

• Definition and Procedure
• Duration of sustained vowel (/a/) on one breath
• Normal values: 25–35 sec (males), 15–25 sec (females), 10–15 sec (children)
• <10 seconds in adults suggests dysfunction
• Clinical Integration
• Bedside test with stopwatch post-extubation
• Pediatric adaptation: shorter phonation tasks
• Adjust expectations in COPD or Parkinson’s disease
• <10 seconds requires ENT referral
• Document values in anesthesia record

GRBAS Scale

• Description
• Perceptual rating: Grade, Roughness, Breathiness, Asthenia, Strain
• Each parameter scored 0–3; ≥2 indicates dysfunction
• Clinical Integration
• Requires brief training for anesthesiologists
• Apply during postoperative checks
• Adjust for age-related changes or neurological tremor
• In resource-limited settings: reliable screening tool
• Referral for score ≥2

Voice Handicap Index (VHI)

• Overview
• 30-item questionnaire (0–120 total score)

30 indicates moderate to severe handicap

• Clinical Integration
• Use pre- and post-surgery in professional voice users
• Repeat within 24–48 hours, and at 1 week if persistent
• Use validated translations for multilingual patients
• Scores >30 trigger speech pathology referral
• Document in chart

V-RQOL Questionnaire

• Purpose
• 10-item tool focusing on quality of life impacts
• Scored 0–100; <75 indicates significant impact
• Clinical Integration
• Short, suitable for busy recovery units
• Administer within 48 hours post-surgery; repeat at 1–2 weeks
• Use translated versions for tonal languages
• Scores <75 prompt referral

Acoustic Analysis

• Parameters
• Jitter (<1%), shimmer (<3%), noise-to-harmonics ratio (<0.2)
• Tools
• Software (e.g., Praat, MDVP) for voice recordings
• Clinical Integration
• Performed 48–72 hours post-surgery for persistent hoarseness
• Collaborate with speech pathologists
• Adjust interpretation for neurological baseline voice changes
• Best suited to tertiary centers

Laryngoscopy

• Types
• Direct, indirect, flexible fiberoptic
• Findings
• Detects edema, hematoma, paralysis, granulomas
• Clinical Integration
• Indicated for abnormal MPT/GRBAS or high-risk patients
• ENT collaboration within 24–48 hours if persistent
• Pediatric: flexible fiberoptic preferred
• In low-resource settings: reserve for severe cases

Transcutaneous Laryngeal Ultrasonography

• Technique
• Non-invasive ultrasound to visualize vocal fold movement
• Clinical Integration
• Bedside use post-extubation
• Safe for pediatric and geriatric patients
• Repeat at 48 hours if abnormal
• Especially useful in resource-limited environments

Fiberoptic Bronchoscopy

• Purpose
• Visualizes larynx and subglottis with high resolution
• Clinical Integration
• Intraoperative use for trauma assessment
• Postoperative use for stridor or severe hoarseness
• Pediatric scopes minimize trauma
• Reserved for severe or unclear cases in resource-limited centers

Indirect Laryngoscopy

• Method
• Mirror or endoscope via oral cavity
• Clinical Integration
• Bedside screening within 24 hours
• Suitable for geriatric or neurological patients
• Rapid assessment with phonation task (/e/)
• Abnormal findings prompt ENT referral

Emerging Technologies

• Intraoperative Neuromonitoring (IONM)
• Electromyography monitoring of RLN during high-risk surgery
• AI-Based Voice Analysis
• Detects subtle pitch or quality changes via machine learning
• High-Resolution Imaging
• Narrow-band imaging and advanced endoscopy improve detection of lesions
• Clinical Integration
• IONM during thyroidectomy and neurosurgery
• AI analysis for professional voice users
• Advanced imaging in tertiary centers

Considerations for Diverse Patient Populations

• Pediatric: Small cords, higher risk of trauma; use smaller tubes and early stridor monitoring
• Geriatric: Reduced elasticity, aspiration risk; perform bedside swallow tests
• Professional Voice Users: Baseline VHI/V-RQOL critical; coordinate rehabilitation with speech therapy
• Neurological Conditions: Pre-existing weakness may compound injury; document baseline voice
• Multilingual Patients: Use culturally adapted and translated questionnaires

Integration into Anesthesia Practice

• Preoperative Assessment
• Baseline evaluation using MPT, GRBAS, or VHI/V-RQOL
• Identify high-risk patients (prior neck surgery, neurological disease)
• Document baseline for postoperative comparison
• Intraoperative Care
• Use video laryngoscopy to minimize trauma
• Select appropriate ETT sizes; maintain cuff pressure <20–30 cmH₂O
• Consider IONM in high-risk surgeries
• Postoperative Evaluation
• Bedside MPT and GRBAS within 1–2 hours
• Repeat at 24–48 hours if abnormal
• Use ultrasonography in low-resource settings
• ENT referral for persistent abnormalities
• Collaboration
• ENT for structural and functional assessment
• Speech pathology for rehabilitation planning
• Patient Education
• Inform about risk of voice changes
• Encourage reporting of hoarseness, swallowing difficulty
• Provide follow-up details
• Documentation
• Record MPT, GRBAS, VHI/V-RQOL, ultrasonography, or laryngoscopy findings
• Ensure clear follow-up and referral notes

Conclusion

Anesthesiologists are central to the early detection and management of postoperative vocal cord dysfunction. A multimodal strategy—combining bedside screening tools (MPT, GRBAS), patient-reported measures (VHI, V-RQOL), and advanced diagnostics (ultrasonography, laryngoscopy, acoustic analysis)—ensures timely intervention. Integration of clinical vigilance, patient education, and multidisciplinary collaboration optimizes outcomes across all patient groups, including pediatric, geriatric, professional voice users, neurological, and multilingual populations, even in resource-limited settings.