5 Jan, 2017
Intubation and Airway Management
Airway Management: 
Emergency airway management is associated with a high complication rate. Evaluating the patient prior to airway management is important to identify patients with increased risk of failed airways. Induction agents are often required, but most induction agents are associated with hypotension during emergency intubation. Use of muscle relaxants is controversial for emergency intubation, but they are commonly used in the emergency department. 
 
Evaluation of the Patient 
Two crucial questions that a healthcare provider performing airway management has to answer are:  
  1. Can I perform effective mask ventilation?  
  2. Can I safely intubate this patient?  
The most commonly used scheme for predicting difficult intubation is the Mallampati classification system, which is based on visualization of the uvula, palate, and pharyngeal structures in awake patient in sitting position with open mouth and protruded tongue. Other important predictors of difficult airway are Mallampati class 3-4, small mouth opening (< 3 cm or 3 finger breadth), short thyromental distance (< 6 cm), decreased neck extension, inability to prognath, facial hair, and short thick neck.  
 
Modified Mallampati Score 
  • Class I: Soft palate, uvula, fauces, pillars visible 
  • Class II: Soft palate, uvula, fauces visible 
  • Class III: Soft palate, base of uvula visible 
  • Class IV: Only hard palate visible  
Before attempting intubation, check LEMON (look, evaluate 3-3-2 rule for mouth opening, mentum to hyoid distance, hyoid to thyroid distance, mallampati, obstruction, neck mobility) and YBAGPEOPLE ( Yankauer, bag valve mask, access iv, get help if not an anesthesiologist, position, ET tube, oxygen, pharmacy/medications, laryngoscope and other equipment, and evaluate for difficult airway).  
 
The steps in effective RSI intubation are:  
 
Pre-oxygenation  
Pre-oxygenation replaces nitrogen in the lungs by filling the entire functional residual capacity with oxygen – 450 mL of oxygen is present in the lungs when breathing room air; this amount increases to 3,000 mL ( more than 6 times normal ) when a patient breathes 100% oxygen.  
 
Healthy adults breathing room air (FIO2 of 0.21) will develop oxygen desaturation (SpO2 <90%) within 2 min of apnea. However, healthy individuals pre-oxygenated with 100% oxygen can maintain oxygen saturation above 90% for more than 6-8 min.  
 
Preoxygenate for at least 3 mins. CPAP or PEEP improves oxygenation by increasing FRC thus preventing atelectasis and by reversing ‘shunt physiology’ by recruiting poorly ventilated lung units. It is important to note, however, that patients with respiratory failure due to cardiopulmonary disease may not have an adequate response to conventional preoxygenation. 
 
Preinduction Drugs 
Stimulation of the airway with a laryngoscope and endotracheal tube presents an extremely noxious stimulus, which is associated with an intense sympathetic discharge resulting in hypertension and tachycardia (called the pressor response). Endotracheal intubation also can provoke bronchospasm and coughing that may aggravate underlying conditions, such as asthma, intraocular hypertension, and intracranial hypertension. Patients who are at risk for adverse events from airway manipulation benefit from the use of preinduction drugs, which include opioids, lidocaine, beta-adrenergic antagonists, and non-depolarizing neuromuscular blockers. 
 
Caution is advised when using opioids in patients who are in severe shock states. Opioids can block the sympathetic compensatory response to hypotension, resulting in cardiovascular collapse. The doses used are:  
  • Fentanyl: 2-3mcg/kg as slow IV. 
  • Lidocaine: 1-1.5mg/kg as rapid IV. Lidocaine can blunt the rise in intracranial pressure during intubation. 
Induction Agents 
The goals in administering induction agents are to produce a state of unconsciousness, optimize intubating conditions, and prevent hemodynamic response to airway manipulation. Commonly used induction drugs include benzodiazepines, barbiturates, narcotics, propofol, etomidate, and ketamine, either as sole agents or in combination with each other.
 
Doses of these medications are: 
  1. Etomidate : 0.3mg/kg 
Etomidate provides fast onset within 30 sec, rapid recovery from a single bolus within 3-5 mins, and maintains cardiovascular stability, which has made it a very popular induction agent. Etomidate maintains hemodynamic stability by preserving both sympathetic outflow and autonomic reflexes, and does not significantly affect heart rate, mean arterial pressure, stroke volume, cardiac index, or pulmonary or systemic vascular resistance, over a wide range of induction doses.  
 
Etomidate produces adrenal suppression and even a single dose inhibits steroid production, resulting in adrenal suppression. The use of etomidate in critically ill patients with sepsis and septic shock should be discouraged. If patients who are in septic shock receive etomidate, corticosteroid supplementation to prevent unnecessary deaths is recommended. Since the adrenal suppression by the drug lasts longer than previously estimated (up to 72 h), some authors have questioned the use of etomidate in critically ill patients altogether.  
 
However, recent data shows that in a mixed group of critically ill patients with sepsis, severe sepsis, and septic shock, single-dose etomidate administration for intubation in the ICU was not associated with higher mortality or other adverse clinical outcomes. Crit Care Med. 2013 Mar; 41(3):774-83. 
 
  1. Ketamine: 2mg/kg 
Ketamine is unique among the hypnotic agents in that it has analgesic, sedative, and amnestic effects. It has a slower onset and offset compared to propofol or etomidate following IV infusion, and stimulates the cardiovascular system. 
 
Ketamine produces excitatory CNS effects and increases the cerebral metabolic rate of oxygen, cerebral vasodilation and cerebral perfusion pressure, and increase intracranial pressure, which might limit its use in patients with underlying intracranial hypertension.  
 
Preservation of respiration and sympathomimetic effects make ketamine a potentially useful agent for emergency airway management. The sympathomimetic effects of ketamine mediate increase in heart rate, blood pressure, cardiac output, and myocardial oxygen demand. These effects can be beneficial in hypovolemic, hemodynamically unstable patients, but can also be detrimental in patients with coronary artery disease.  
 
Ketamine is a safe and valuable alternative to etomidate for endotracheal intubation in critically ill patients, and should be considered in those with sepsis. The bronchodilator properties of ketamine make it suitable for patients with bronchospasm due to status asthmaticus or COPD. 
 
Ketamine infusion can be used to maintain procedural sedation. It acts in 1-2 mins and drug action wears off in 10 mins. 
 
  1. Propofol: 2mg/kg ( can give in 2-3 divided doses ) 
Typical doses given by anesthesia is 100mg as starting and then 20mg every 2-3 mins. Propofol is one of the most commonly used hypnotic agents for induction and maintenance of anesthesia and sedation. Propofol has very fast onset, short duration of action and creates excellent intubating conditions. It relaxes the muscles of the pharynx and larynx, resulting in intubating conditions superior to those obtained with thiopental or etomidate. The major disadvantage of propofol is hypotension. Propofol has a negative inotropic effect and decreases stroke volume, cardiac output, and systemic vascular resistance. 
  1. Versed: 0.3mg/kg, same as in etomidate.  
  1. Dexmedetomidine: 1mcg/kg bolus followed by 0.3-0.7 mcg/kg/hr 
  1. Sodium thiopental
Muscle Relaxants 
Neuromuscular blocking agents improve intubation conditions and ease mask ventilation. Furthermore, intubating without muscle relaxants carries significant risk of laryngeal and vocal-cord morbidity. When neuromuscular blocking agents are used for emergency intubation, rapid onset is crucial to allow quickly securing the airway. 
 
Succinylcholine (1-1.5 mg/kg) Succinylcholine is a depolarizing and hence irreversible neuromuscular blocking agent that mimics the action of acetylcholine by binding to acetylcholine receptors, resulting in depolarization of the motor end plate, inactivation of sodium channels, and inhibition of further activation of sodium channels by acetylcholine. Fast onset (within 30 s) and short duration (8–10 min) makes succinylcholine a useful agent when rapid-sequence induction is planned. Unless there are contraindications, it is the drug of choice when the airway must be secured quickly.  
 
One major complication of succinylcholine is exaggerated potassium release, resulting in life-threatening hyperkalemia. The drug may trigger malignant hyperthermia in genetically susceptible persons. Avoid succinylcholine in patients with crush injuries and who are bedridden for more than 5 days. Also, succinylcholine may cause muscle fasciculations, increased ICP and increased oxygen demand. 
 
Rocuronium (0.6-1.2 mg/kg) Rocuronium is non-depolarizing but reversible neuromuscular blocking agent with rapid onset (60–90 s) and intermediate duration of action (30–60 min).  
 
Rapid sequence intubation: 
Rapid-sequence intubation consists of pre-oxygenation, pre induction agents followed by administration of an induction agent and muscle relaxant in rapid succession. After waiting 45–60 s (without mask ventilation) for the induction agent and muscle relaxant to take effect, direct laryngoscopy and endotracheal intubation are performed. 
 
When the airway team is called for emergency airway management, evaluation of the airway is the first step. If a difficult airway is suspected, additional equipment (such as a fiberoptic bronchoscope and/or a video laryngoscope) for airway management is promptly obtained. A supply of 100% oxygen, a well-fitting mask with attached bag-valve device, suctioning equipment, a magill forceps, and oral and nasal airways should be immediately available. If suspicion is high for possible need of a surgical airway, the surgical team is notified and present at bedside as backup prior to intubation attempts. Ensure adequate intravenous access and availability of vasopressors is necessary before administering any induction medications. 
 
Traditional teaching recommends placing the patient in the “sniffing” position, in which the neck is flexed and the head is slightly extended about the atlantooccipital joint in order to align the oral, pharyngeal, and laryngeal axes. The ear and sterna notch should be in the same horizontal axis and this can be achieved with some pillows under head, but never under shoulder. (Remember bag-mask ventilation is achieved with head tilt and chin lift, where we typically use some pillows under shoulders). 
 
Post intubation, fluid resuscitation and vasopressor support are often needed to achieve the patient’s blood pressure goals during this period. Adequately fluid resuscitate the patient before intubation, if time permits. Following intubation it is important to adequately sedate the patient, since the patient may have residual paralysis from neuromuscular blocking agents received during induction. 
 
Complications include vocal cord trauma, subglottic stenosis, tracheoesophageal fistula, bronchospasm, aspiration during intubation, hypotension due to PEEP after intubation, myocardial ischemia, potential spinal cord injury if neck trauma is present and raised ICP. 
 
Post intubations complications: 
  • Bradycardia : Assume hypoxia and therefore tube displacement until proven otherwise 
  • Desaturation : Displaced tube or Obstruction-pass suction catheter through tube  
  • Hypotension:
    1. Pneumothorax 
    2. Decreased Venous Return from PPV. Disconnect from vent for 30-60 seconds and observe for increased BP and decreased pulse. Consider reducing PEEP and decreasing VT  
    3. Induction Agents- diagnosis of exclusion, give fluid bolus 
    4. Cardiogenic
 
Laryngeal Mask Airway: 
 
The manufacturer recommends two size selection criteria: weight based (for adults patients: size 4 for 50-70 kg, size 5 for 70-100 kg, and recently size 6 for >100 kg) and gender based (size 4 for female and size 5 for male adults). 
 
Insertion of the LMA during inadequate level of anesthesia is a common mistake. A patient who is not deep enough (gagging, coughing) will fight the LMA insertion and discourage the rescuer from inserting the index finger deep into the mouth resulting in misplacement of the device. A misplaced LMA is more likely to be dislodged or to trigger reflexes (laryngospasm, glottic closure, vomiting, or hiccups). 
 
The most common error made is the insertion of the LMA straight into the mouth without using the hard palate as a slide and with the index finger not inserted deep enough into the mouth, misplacing the LMA. 
 
One technique instead of intubating LMA is insert bougie via LMA, get LMA out and insert tube over bougie. 
 
LMA also provides for ventilation during bronchoscopy. Insert LMA over ET tube, ventilate via LMA and bronch via ET tube. 
 
 
PEARLS: 
  • Air leak test: More than 110ml or 25% of tidal volume leak is favorable and suggests no laryngeal edema. It doesn’t detect supraglottic obstructions though. 
  • Awake intubation: Glycopyrolate 0.2 mg IV (and 0.1mg thereafter every 2-3 mins) or Atropine .01 mg/kg. Onset of action is 15 min and lasts 5 hours. Wait for 5 mins, and use 5 ml of 4% lidocaine inhaled to numb the airway. Wait for 3-5 mins and give 2% viscous lidocaine at the posterior end of tongue with tongue depressor and have patient gargle it. Lidocaine works best when oral airway is very dry. 
  • Bimanual Laryngoscopy: Pressure on thyroid cartilage with yield better views, especially if the larynx is too anterior. Cricoid pressure will theoretically compress the esophagus and prevent regurgitation.  
  • When used to confirm endotracheal placement, the bougie is passed down the endotracheal tube and there should be ‘hold up’ at 30-40cm depth, if this does not occur the bougie is likely to be in the esophagus. Hold up of the bougie occurs when the tip reaches the small bronchi. 
  • Surgical Airway: If sats below 70% for more than 3 mins and unable to oxygenate, it’s time for emergent Cricothyrotomy. 
  • Cricoid pressure to compress esophagus has been disproved due to lack of evidence 
  • RSI is specifically done to optimize laryngoscopy conditions and permit oral intubation. If it is apparent that the oral route has obvious anatomic problems (not merely potential difficulty), RSI should never be considered. When the oral route is impossible, intubation will need to take place through the nose or neck, and this should be done with the patient awake. Examples include massive angioedema, advanced Ludwig’s angina, wired jaw, or readily apparent combinations of airway distortion, disproportion, and dysmobility (cervical spine and mandible), that preclude oral intubation. 
  • Ketamine: Airway reflexes like cough reflex are preserved and better choice in awake intubation. However, rapid administration of ketamine can render the patient apneic.  
  • Never give half doses of paralytics; either full dose or none 
  • Post-intubation, once patient settles in, try coming down on sedatives and increase opiate analgesia, if needed, which also acts as sedative. 
  • High aspiration risk like GI bleeders will benefit from NG tube placement before intubation. 
  • When used at a dose of 1.2mg/kg, Rocuronium is as good as sux in achieving paralysis.  
  • Tracheostomy intracuff pressure should be high enough to achieve a closed respiratory system and be between 20- 30cmH2O.  
  • In general, tracheostomy should be delayed until at least 10 days after initiating mechanical ventilation. No evidence to support trach at least before 10 days 
  • Percutaneous Trach vs. Open surgical Trach: Perc. Trach has less complications and less bleeding but may need bronchoscopy during procedure. There was no difference in mortality, ventilator days, sedation, ICU days or VAP. 
  • Fenestrated Trach tubes prevent disuse atrophy of vocal cords but must warn patients that they will have sensation of air coming up through vocal cords 
  • Decreased Glasgow Coma Scale score does not mandate endotracheal intubation in the emergency department. Intoxicated patients in ED are often intubated for low GCS and lack of airway protection. However, the loss of airway reflexes and risk of aspiration doesn’t correlate well using the GCS alone. J Emerg Med. 2009 Nov; 37(4):451-5, Resuscitation. 2012 Jan;83(1):86-9
  • An amp of phenylephrine at the bedside can come in handy, in case the intubating agents cause vasodilatory hypotension.  
  • Laryngeal exposure during laryngoscopy is better in the 25 degrees back-up position (i.e. head up without a pillow) than in the supine position. Br J Anaesth. 2007 Oct; 99(4):581-6. 
  • Morbidly obese patients with borderline saturations will benefit from nasal cannula while intubating. 
  • If patient is very tachycardic before intubation, better give some beta blockers before intubation. 
  • Use half the dose of fentanyl, etomidate, propofol or versed if vital signs are borderline or if elderly. 
  • Adequate analgesia and sedation will produce acceptable intubating conditions and may minimize use of paralytics. 
  • IM Sux-need 4mg/kg to get 2-3 minute induction time (Anaesthesia. 2007 Aug;62(8):757-9) 
  • Duration of action of cisatracurium is around 45-60 mins. 
  • Do not bag paralysed patients unless sats fall below 90. If you bag with paralysis, some of that air goes into stomach. 
  • If EtCO2 is inconclusive and you are confident of tube being in trachea, either do a fiberoptic laryngoscopy or pass a bougie into tube. If you hit a stop point at 30-40cm, then tube is in trachea.  
  • Distally placed pulse ox has a 60-90 second lag from true saturation. Newer pulse ox meters are better and have a lag time of 30-60 secs. 
  • When intubating with bougie, rotate the ETT 90 degrees before the tip of the ETT passes through the vocal cords. (The hole faces the side). This maneuver prevents the beveled tip of the ETT from catching on the right arytenoid process, aryepiglottic fold, right vocal cord, or epiglottis.  
  • The GlideScope-specific rigid stylet and standard malleable stylet are equally effective for GlideScope use. Can J Anaesth. 2007 Nov;54(11):891-6. 
  • Ketofol: Get ketamine and propofol doses 2mg/kg into a 10 cc syringe and give combo of 2cc each at a time. This can help avoid propofol induced hypotension at the time of intubation.
  • Glidescope vs Laryngoscope : Amongst patients in ICU requiring intubation, video laryngoscopy compared with direct laryngoscopy did not improve first pass orotracheal intubation rates. This trial shows that Glidescope improves the view of glottis but not necessarily leads to higher first pass intubation rates.  MACMAN Trial , Chest. 2017 Sep;152(3):510-517 , Crit Care. 2017 Nov 24;21(1):288
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Mechanical Ventilation