Approach to the Unconscious Patient - An Anesthesia Perspective

1. IMMEDIATE PRIORITY: CALL FOR HELP AND APPLY THE ABC FRAMEWORK

2. STEP A - AIRWAY: YOUR PRIMARY OBLIGATION AS AN ANESTHESIOLOGIST

"The tongue of the comatose patient in the supine position must be regarded as a foreign body in the oropharynx." - Pye's Surgical Handicraft

Immediate actions:

• Position: Head tilt-chin lift (if no cervical spine injury) OR jaw thrust (if trauma suspected) to displace the tongue anteriorly
• Clear the airway: Suction oropharyngeal secretions, blood, vomitus. Check for loose teeth, food
• Oropharyngeal airway (Guedel): Insert even if the patient appears to clench teeth - prevents tongue from obstructing
• Cervical spine precaution: In any trauma patient, assume an unstable C-spine until proven otherwise. Use manual in-line stabilization (MILS) - not traction - during all intubation attempts. Remove the front of the collar to allow wider mouth opening while maintaining inline stabilization

When to secure definitively?

• Any depression of cough reflex or level of consciousness = cuffed endotracheal tube (ETT)
• Aspiration of pharyngeal secretions or gastric contents
• GCS ≤ 8 (classical threshold for definitive airway)
• Inability to protect airway

3. PREOXYGENATION: NON-NEGOTIABLE BEFORE INTUBATION

Methods:

Safe apnea time after maximal preoxygenation:

• Healthy adult: up to 9 minutes
• Obese adult: ~3 minutes
• Child: <3 minutes
• Pregnant: significantly reduced

Apneic oxygenation (bonus):

• Nasal cannula at 15 L/min during laryngoscopy (NO DESAT technique) extends safe apnea time by passive diffusion into alveoli. Consider in every difficult/emergency intubation.

4. ASSESS THE CAUSE IN PARALLEL: THE AEIOU-TIPS MNEMONIC

• Dextrose 50% IV (hypoglycemia is immediately reversible and immediately deadly)
• Thiamine 100 mg IV FIRST (before glucose in any alcoholic or malnourished patient - prevents precipitating Wernicke's encephalopathy)
• Naloxone 0.4-2 mg IV (opioid reversal - look for pinpoint pupils, respiratory depression)
• Flumazenil (benzodiazepine reversal - use cautiously, can precipitate refractory seizures)

5. RAPID NEUROLOGICAL ASSESSMENT: "DISABILITY" IN ABCDE

A. Glasgow Coma Scale (GCS)

• GCS ≤ 8: defines coma, mandates airway protection
• GCS 9-12: moderate brain injury
• GCS 13-15: mild

B. Pupils - Critical Localizing Sign

C. Motor Posturing

• Decorticate posturing (flexion of arms, extension of legs): lesion above midbrain, at corticospinal tract level - interruption of cortical input to brainstem
• Decerebrate posturing (arm adduction + extension, wrist pronation, leg extension - opisthotonos): indicates upper midbrain/pontine level dysfunction; far more ominous
  • Only ~10% of head-injured patients with extensor posturing recovered (Jennett & Teasdale series)
  • None with extensor posturing recovered after cardiac arrest (Chen et al.)
• Flaccidity: lower brainstem or spinal cord level

D. Brainstem Reflexes

• Oculocephalic (Doll's eye): rotate head side to side - eyes should move conjugately in opposite direction in intact brainstem. CONTRAINDICATED if C-spine not cleared. Absent = brainstem dysfunction
• Oculovestibular (cold caloric): instill cold water in external auditory canal - slow eye deviation toward cold ear in intact brainstem. Most powerful brainstem test
• Corneal reflex: CN V afferent, CN VII efferent via brainstem; loss indicates pontine dysfunction
• Cough/Gag reflex: CN IX/X; loss = inability to protect airway

E. Cushing's Triad - ALARM SIGN

• HOB 30°
• Hyperventilate to PaCO2 30-35 mmHg (temporary measure for impending herniation)
• Mannitol 0.5-1 g/kg IV or hypertonic saline 3% 250 mL
• Emergency neurosurgery consultation

6. RAPID SEQUENCE INTUBATION (RSI): THE ANESTHESIOLOGIST'S CORE SKILL

Indications for RSI:

• Unconscious patient with unknown NPO status
• Bowel obstruction, pregnancy (2nd trimester onward), GERD, morbid obesity, gastroparesis

The 7 Ps of RSI:

1. Preparation: Equipment ready - ETT (7.5-8 for males, 7.0-7.5 for females), stylet, laryngoscope, suction on, drugs drawn up, IV access, monitoring, failed airway trolley
2. Preoxygenation: 100% O2, 3 minutes or EtO2 >90%; consider apneic oxygenation via nasal cannula
3. Pretreatment: Optional - atropine (bradycardia, peds), lidocaine (attenuate ICP rise), fentanyl (blunt intubation response in raised ICP)
4. Paralysis with induction:
   • Induction agents (titrate to LOC):
     • Ketamine 1-2 mg/kg: preserves airway tone, bronchodilator, maintains BP - preferred in hemodynamically unstable/trauma/asthma
     • Etomidate 0.3 mg/kg: minimal cardiovascular depression, preserves cerebral autoregulation - preferred in hemodynamic instability. Caution: adrenal suppression (one dose in critically ill is controversial)
     • Propofol 1.5-2.5 mg/kg: avoid if hypotensive (causes vasodilation and decreased cardiac output). Good for raised ICP if normotensive
     • Thiopentone 3-5 mg/kg: reduces ICP and CMRO2, but causes hypotension. Now largely replaced.
   • Paralytic agents:
     • Succinylcholine 1.5 mg/kg (depolarizing): fastest onset (~60 seconds), ultra-short duration (~10 min). Still gold standard for RSI
       • Contraindications: burns >24-48h, denervation, crush injury, hyperkalaemia, myopathies, personal/family history of malignant hyperthermia, pseudocholinesterase deficiency
     • Rocuronium 1.2 mg/kg (non-depolarizing): onset ~60-90 seconds at this dose; reversible with sugammadex 16 mg/kg (rapid reversal now makes this a true alternative to succinylcholine)
5. Protection/positioning: Cricoid pressure (Sellick maneuver) - 10 N awake, 30 N after LOC. Note: controversial - can worsen laryngoscopic view in 30% of patients; release if intubation is difficult. MILS if cervical spine not cleared
6. Placement of ETT (with confirmation): Capnography (gold standard), misting of tube, bilateral auscultation, improving SpO2, chest X-ray
7. Post-intubation management: Confirm position, secure tube, CXR, ventilator settings, sedation

7. TARGETS AFTER SECURING THE AIRWAY

8. HISTORY AND EXAMINATION PEARLS

From bystanders, family, ambulance crew:

• Duration and mode of onset (sudden vs. gradual)
• Witnessed seizure? Head injury? Fall?
• Known medical conditions (diabetes, epilepsy, cardiac disease, liver disease)
• Medications, drugs, alcohol
• Recent fever, headache, neck stiffness (meningitis?)
• Suicide attempt/poisoning?

Complete undress the patient:

• Examine front AND back, in good light
• Medical alert bracelet?
• Track marks (drug use)?
• Signs of head/facial injury

9. INVESTIGATIONS

• Blood glucose (capillary) - the single most important bedside test
• SpO2, ECG, ABG
• Point-of-care electrolytes/blood gas: pH, Na, lactate

• FBC, urea, creatinine, electrolytes, LFTs, glucose, osmolality
• Coagulation
• Blood cultures (if fever/sepsis)
• Serum calcium, ammonia (if liver disease)
• Toxicology screen (blood + urine)
• TFTs, cortisol
• Cardiac enzymes (if MI suspected)

• CT brain (without contrast first): emergent if focal neurological deficit, head trauma, suspicion of intracranial event, or deteriorating GCS
• CXR (post-intubation, aspiration, thoracic trauma)
• CT C-spine if trauma

• After ruling out raised ICP on CT
• If meningitis/SAH suspected and CT normal
• Do NOT delay antibiotics for LP if meningitis is suspected

10. DOCUMENTATION AND HANDOVER

1. Level of consciousness (GCS)
2. Pupil size and reaction
3. Blood pressure
4. Pulse rate
5. Respiratory rate

VIVA QUESTIONS & MODEL ANSWERS

GCS ≤ 8 - classically defined as coma and inability to protect the airway. However, the trend (rapidly falling GCS, high aspiration risk) matters as much as the absolute number.

In thiamine-deficient patients (alcoholics, malnourished), glucose administration precipitates acute Wernicke's encephalopathy by depleting remaining thiamine stores needed for glucose metabolism (pyruvate dehydrogenase requires thiamine). Thiamine must come first.

Hypertension + Bradycardia + Irregular respirations. It represents a brainstem reflex response to critically raised ICP - the body raises systemic BP to maintain cerebral perfusion pressure, and the baroreceptors respond with reflex bradycardia. It signals imminent herniation and demands immediate treatment.

Uncal (transtentorial) herniation - an expanding ipsilateral supratentorial mass compresses CN III (parasympathetics travel on the outside of the nerve and are compressed first), leading to unopposed sympathetic dilation. This is a neurosurgical emergency. Immediately hyperventilate to PaCO2 30-35, give mannitol 0.5-1 g/kg or 3% hypertonic saline, elevate HOB 30°, call neurosurgery for emergency decompression.

Decorticate (flexion) = lesion at or above the upper midbrain, interrupting corticospinal fibers but leaving brainstem postural reflexes intact. Decerebrate (extension) = lesion at the midbrain/upper pontine level, releasing vestibulospinal and reticulospinal reflexes from forebrain inhibition. Decerebrate is far worse - only ~10% of head-injured patients with extensor posturing recovered.

Burns (after 24-48 hours onset of upregulated extrajunctional ACh receptors), denervation injuries, crush/prolonged immobilization injuries (all cause hyperkalemia on succinylcholine due to extrajunctional receptor upregulation), known or suspected hyperkalaemia, myopathies (especially Duchenne - risk of rhabdomyolysis and cardiac arrest), pseudocholinesterase deficiency, personal or family history of malignant hyperthermia, and penetrating eye injuries (raises intraocular pressure transiently).

A healthy adult gets ~9 minutes. Factors that shorten it: obesity (~3 minutes), pregnancy, children (small FRC), critically ill/septic patients (high O2 consumption), pre-existing lung disease. THRIVE and apneic oxygenation with nasal cannula at 15 L/min extend this window.

The Sellick maneuver (30 N after LOC) aims to occlude the esophagus by compressing the cricoid against it. However, MRI studies show the esophagus is often displaced laterally rather than compressed. Cricoid pressure worsens laryngoscopic view in up to 30% of cases. Its use has been downgraded - the AHA recommends against it during cardiac arrest, and EAST guidelines removed it as Class I. If intubation is difficult, release cricoid pressure. Apply only if you have a trained assistant.

Follow the difficult airway algorithm: Call for help. Attempt videolaryngoscopy (VAL). Try a supraglottic airway device (LMA/LMA Supreme) as a bridge. If still unable to oxygenate = CICO (Can't Intubate Can't Oxygenate) = surgical airway is mandatory - cricothyrotomy (surgical or Seldinger technique). In a trauma patient, unlike elective cases, "wake the patient up" is rarely an option - commit to securing the airway.

The doll's eye reflex - rotating the head rapidly side to side in an unconscious patient with an intact brainstem results in conjugate eye movement in the OPPOSITE direction (eyes look "left" when head rotates right). It is CONTRAINDICATED when the cervical spine has not been cleared. Loss of the reflex indicates brainstem dysfunction at the level of the MLF (medial longitudinal fasciculus)/pons.

Ketamine 1-2 mg/kg IV. It stimulates catecholamine release, maintaining or increasing heart rate and blood pressure. It also causes bronchodilation (useful in asthma/bronchospasm). Note: in a catecholamine-depleted patient (prolonged shock), ketamine's direct myocardial depressant effects may paradoxically cause hypotension - use with extreme caution and consider vasopressors in parallel. Etomidate (0.3 mg/kg) is an acceptable alternative for cardiovascular stability.

Stupor: a state of reduced consciousness from which the patient can be aroused by vigorous stimulation and from which they return to the reduced state when stimulation stops. Coma: a state of complete unresponsiveness - no purposeful response to any external stimulus. Neurologically, coma requires dysfunction of either (a) both cerebral hemispheres bilaterally or (b) the ascending reticular activating system (ARAS) in the brainstem (midbrain/upper pons).

Normocapnia (PaCO2 35-40 mmHg) is the standard target. Hyperventilation to PaCO2 30-35 mmHg causes cerebral vasoconstriction and is used only as a temporary bridge for impending herniation (Cushing's triad, blown pupil), NOT as prophylaxis or routine maintenance. Excessive hyperventilation (<30 mmHg) causes profound vasoconstriction and ischemia.

• Miller's Anesthesia, 10th Edition (Preoxygenation, RSI, Emergency Airway Algorithm)
• Morgan & Mikhail's Clinical Anesthesiology, 7th Edition (Aspiration risk, cricoid pressure)
• Plum & Posner's Diagnosis and Treatment of Stupor and Coma (Motor posturing, coma examination)
• Sabiston Textbook of Surgery (GCS, TBI treatment targets)
• Pye's Surgical Handicraft, 22nd Edition (Initial management of unconscious patient)
• Adams & Victor's Principles of Neurology, 12th Edition
• Harrison's Principles of Internal Medicine, 22nd Edition (Brainstem reflexes)
• Rosen's Emergency Medicine & Tintinalli's Emergency Medicine (AEIOU-TIPS, RSI)
• Neuroanatomy through Clinical Cases, 3rd Edition (Cushing's triad, reflexes)