Pharmacology & Complications in Intubation

Pharmacology in Endotracheal Intubation

• Applying nerve transmission principles to neuromuscular blocking agents
• Describing clinical applications of neuromuscular blocking drugs
• Stating the mechanisms of action of hypnotic, sedative, or anxiolytic medications and their importance in respiratory care practices
• Describing the mechanism and role of ventilatory stimulants
• Explaining the pain pathway (nociceptive pathway) and discussing the role of analgesics
• Discussing the role of medications used for local and general anesthesia
• Describing the process of rapid sequence intubation

Complications of Intubation

• Failed intubation
• Spinal cord and vertebral column injury
• Corneal abrasion
• Trauma to lips, teeth, tongue, and nose
• Hyper/hypo-tension
• Tachy/brady-cardia
• Arrhythmias
• Increased ICP and IOP
• Laryngospasm
• Bronchospasm
• Laryngeal trauma
• Airway perforation
• Tension pneumothorax
• Esophageal intubation
• Increased Raw
• Gastric Aspiration
• Residual muscle paralysis
• Right main stem intubation
• Impaired swallowing
• Myocardial infarction

Mechanisms Causing Hypotension

• Volume depletion
• Positive pressure ventilation
• Peep and Auto-peep
• Medications
• Myocardial Ischemia

When to Intubate

• Intubation is required in patients who have at least one of the following 5 indications
• Inability to maintain airway patency
• Inability to protect the airway against aspiration
• Failure to ventilate
• Failure to oxygenate
• Anticipation of a deteriorating course that will eventually lead to respiratory failure

Keys For Success and Safety in Intubation

• ASSESSMENT
• ADEQUATE PREPARATION
• PROPER POSITIONING
• BACK-UP PLAN (A,B,C......Z)
• CALL EARLY FOR HELP

Intubation During Cardiac Arrest

• Patient is Apneic
• Agonal breathing is an abnormal pattern of breathing and brainstem reflex characterized by gasping and labored breathing accompanied by strange vocalizations and myoclonus (involuntary muscles jerks/twitches)
• Patient is Unresponsive
• Patient is Flaccid
• Patient is Areflexic
• Indication of “Crash” airway; easy to intubate and no meds necessary
• Preoxygenate, prepare equipment, and intubate

Airway Management

• Awake Intubation
• Rapid Sequence Intubation
• Surgical Airway (i.e., cricothyrotomy)

Awake Intubation

• Commonly performed when a patient has a known or suspected difficult airway or history, where loss of protective airway reflexes may have catastrophic events
• Use of local anesthesia with lidocaine spray
• Preoxygenate with BVM or LMA
• Prepare equipment
• Position the patient into a sniffing position
• Opioids for pain are used for substances that act on opioid receptors to produce morphine-like effects and medically they are primarily used for pain relief, including anesthesia
• Analgesics like Benzodiazepines/IV anesthetics for sedation
• Benzodiazepines are a class of drugs primarily used for treating anxiety but also effective in treating several conditions
• Intubate

Rapid Sequence Intubation (RSI)

• Multiple observational studies confirm implementation leads to improved success and decreased complication rates for emergency intubation
• RSI is the administration of a sedative (induction) and neuromuscular blocking (paralytic) agent to render a patient rapidly unconscious and flaccid to facilitate emergent endotracheal intubation and minimize aspiration risk
• RSI is the cornerstone of emergency airway management outside of the operating room
• RSI assumes the patient is at risk for aspiration of stomach contents and incorporates medications and techniques to minimize this risk
• RSI helps mitigate airway manipulation's potential adverse effects
• Preoxygenation permits a longer period of apnea without clinically significant oxygen desaturation
• Bag-mask ventilation is avoided between drug administration and endotracheal tube placement, to minimize gastric insufflation and reduce aspiration risk
• RSI is the standard of care in emergency airway management for intubations not anticipated to be difficult
• The goal of RSI is to intubate the trachea without having to use BVM
• RSI is not indicated in an unconscious and apneic patient

Considerations for RSI

• Approach RSI with caution if the patient has a suspected difficult airway
• Unstable C-spine injury
• Airway tumor
• Significant facial trauma
• Unfavorable anatomy
• Elevated ICP
• Increased risk of ICH
• If difficulty is anticipated, then an awake technique or the use of airway adjuncts is used.

Indications for RSI

• Failure to maintain airway tone

  • Swelling of upper airway as in anaphylaxis or infection
  • Facial or neck trauma with oropharyngeal bleeding or hematoma

• Decreased consciousness and loss of airway reflexes

  • Failure to protect airway against aspiration - Decreased consciousness that leads to regurgitation of vomit, secretions, or blood

• Failure to ventilate

  • End result of failure to maintain and protect airway
  • Prolonged respiratory effort that results in fatigue or failure, as in status asthmaticus or severe COPD

• Failure to oxygenate (i.e., transport oxygen to pulmonary capillary blood)

  • End result of failure to maintain and protect airway or failure to ventilate
  • Diffuse pulmonary edema
  • ARDS
  • Large pneumonia or air-space disease
  • Pulmonary embolism
  • Cyanide toxicity, carbon monoxide toxicity, methemoglobinemia

• Anticipated clinical course or deterioration

  • Uncooperative trauma patient with life-threatening injuries who needs procedures
  • Stab wound to neck with expanding hematoma
  • Septic shock with high minute-ventilation and poor peripheral perfusion
  • Intracranial hemorrhage with altered mental status and need for close blood pressure control
  • Cervical spine fracture with concern for edema and loss of airway patency

Contraindications to RSI

• Absolute

  • Total upper airway obstruction, which requires a surgical airway
  • Total loss of facial/oropharyngeal landmarks, which requires a surgical airway

• Relative

  • Anticipated "difficult" airway, in which endotracheal intubation may be unsuccessful, resulting in reliance on successful bag-valve-mask (BVM) ventilation to keep an unconscious patient alive

• Techniques for awake intubation and difficult airway adjuncts can be used

• The "crash" airway is for a patient in an arrest situation, unconscious and apneic

  • The patient may be flaccid and no time for preoxygenation, pretreatment, or induction and paralysis
  • BVM ventilation, intubation, or both should be performed immediately without medications
  • Multiple methods can be used to evaluate the airway and the risk of difficult intubation (i.e., LEMON rule, 3-3-2, Mallampati class, McCormack and Lehane grade).

7 Steps of Rapid Sequence Intubation

• Preparation
• Preoxygenation*
• Pretreatment/Premedication
• Paralysis with induction
• Positioning and Protection (Sellick maneuver)
• Placement of ETT with proof
• Post-intubation care/management

Preparation for RSI

• Assess the patient for a difficult airway
• Confirm that intubation equipment is functional
• Establish intravenous access
• Draw up essential drugs and determine sequence of administration (induction agent immediately followed by paralytic agent)
• Review possible contraindications to medications
• Attach necessary monitoring equipment

Preoxygenation in RSI

• Aimed at maximizing saturation levels and creating an O2 reservoir in the lungs to eliminate the need for BVM ventilation for the period of apnea after induction and paralysis to minimize the risk of stomach insufflation and aspiration
• Most critical of all steps
• Assist ventilation with bag-valve-mask (BVM) system only if needed to obtain oxygen saturation =90%.

Pretreatment/Premedication for RSI

• Ancillary meds are administered to mitigate the adverse physiologic consequences of intubation
• Opioids for pain, HTN, CAD, ICP
• Lidocaine spray 4% and 1-2 mL of 2% jelly for local anesthesia of the hypopharynx (1.5 mg/kg IV for ICP/asthma)
• Atropine 1 mg for decreasing secretions and bradycardia
• Give 3-5 minutes before sedation and paralysis
• Above meds have side effects and must be chosen cautiously

Paralysis and Positioning with Induction for RSI

• Administer a rapidly-acting sedative induction agent via IV push to produce loss of consciousness, followed IMMEDIATELY by administration of a paralytic via IV push
• Position a patient for optimal laryngoscopy (sniffing position)
• Sellick's maneuver (if desired) is applied upon observing the beginning of unconsciousness
• Firm pressure over the cricoid cartilage to prevent regurgitation of gastric contents; Maintain pressure until ET tube is verified.

Placement of ET tube with proof

• Visualize the ET tube passing through the vocal cords
• Confirm tube placement with the following

  1. Condensation in tube

  2. Colorimetry (purple to yellow) or ETCO2

  3. Auscultation of bilateral breath sounds and equal chest rise

     • Triangle auscultation

  4. Increase in SPO2

  5. CXR

Postintubation care/management

• Secure the ET tube into place
• Initiate mechanical ventilation
• Administer appropriate analgesic and sedative agents for patient comfort, to decrease O₂ demand, and to decrease ICP.

Med Classes in RSI

• Analgesics
  • Medications that decrease the patients perception of pain or pain intensity
  • Opioids*
  • Opioid antagonist
  • Steroids
  • Nonsteroidal Anti-inflammatory

Analgesics

• Opioids (i.e., Morphine, Fentanyl):

  • Natural or synthetic chemical that can bind to an opioid receptor and exert an action -Combine with pain receptor sites in the thalamus and limbic system to prevent transmission of pain impulses -Differ in potency, onset of action, duration of action, chemical structure, available routes of administration, side effects, abuse potential, and cost

• Side effects consist of

  • Drowsiness and euphoria
  • Depressed Respiration and cough
  • Constricted Pupils
  • Release of histamine
    • Vasodilation
    • Bronchoconstriction
  • Nausea and Vomiting
  • Urinary Retention and Tolerance

• Opioid Analgesics: Common Agents

  -Morphine* - 2.5 – 5 mg IV push; onset 5-10 min; duration of action = 3-4 hrs. -Codeine/ Hydromorphone (Dilaudid) -Fentanyl (Sublimaze)* - 1-2 mcg/kg IV push; immediate onset; duration of action = 30-60 min -Meperidine (Demerol)) -Oxycodone/Nalbuphine (Nubain)/Methadone (Dolophine) -Morphine or Fentanyl are commonly used opioids for the premedication phase of RSI

• Analgesic Antagonists

  -Reverse the CNS and ventilatory depression that can be caused by opioids -They can be used when there is suspicion of narcotic overdose -One common agent is Naloxone (Narcan)

Induction

• The induction phase of rapid sequence intubation (RSI) produces anesthesia and rapid unresponsiveness.
• Many drug classes today can be used, but etomidate is most common in the ED for this.
• The goal of the drugs is to produce rapid unconsciousness, short duration of action, and causes minimal alterations in hemodynamics, respirations and ICP
• Most sedatives cause cardiovascular depression exaggerated in patients acutely ill and may be hypovolemic/hypotensive
• Clinical status dictates which induction agent to use
  • Factors include altered hemodynamics, suspected ICP abnormalities, and reactive airway disease

Sedatives/Hypnotics/Anxiolytics

• A drug that reduces CNS arousal counts as a sedative and can induce sleep in larger doses
• A med that induces sleep counts as a hypnotic
• A med that reduces anxiety counts as an anxiolytic
• Some drug classes, such as benzodiazepines, contain all 3 characteristics
• Often needed with analgesics to improve tolerance of ET tubes, facilitate acceptance of mechanical ventilation, suppress spontaneous ventilation, and prevent self-extubation

Sedatives/Hypnotics/Anxiolytics: Relationship to CNS

• Cortex: Responsible for skeletal muscle control, sensations, senses, intellect and memory.

  -If depressed: slowed reflexes, slurred speech, decreased mental ability.

• Brain Stem: Respiratory and Cardiovascular regulation

• Reticular activating system:

  -Cells in the midbrain which control sleep and wakefulness -Sensory filtering

• Limbic system

  -Brain stem control of emotion -Disorders such as schizophrenia, manic depression

• Extrapyramidal system: Balance and coordination

Sedatives/Hypnotics/Anxiolytics: Benzodiazepines

• Most common drug class that enhances inhibitory effect on the receptor for the neurotransmitter GABA (Gamma aminobutyric acid) in the brain
  • GABA is the major inhibitory neurotransmitter. Benzodiazepines increase the efficiency of GABA, thus causing greater inhibition or calming.
• Common agents:
  • Alprazolam (Xanax)
  • Chlordiazepoxide (Librium)
  • Diazepam (Valium)
  • Midazolam (Versed)
  • Lorazepam (Ativan)
• Benzodiazepine Reversal Medication:
  • Flumazenil (Romazicon)
• Midazolam (Versed)
  • Most rapid onset of all the BZD
  • Major disadvantage: requires titration
  • Optimal effects are not observed for 3-5 min
  • No longer recommended as a 1st line induction agent due to its slow onset and variable potency
  • Mild respiratory depressant
  • Overdose can reversed with flumazenil

Anesthetics Classes

• Anesthesia:
  • Refers to the inability to perceive sensations
  • Types: Local or general
• Terminology:
  • Induction: Creates appropriate anesthesia level
  • Maintenance: Continuation of state
  • Termination: Time to recover
• Mode of Action:
  • Local Anesthesia: Acts locally to stop transmission of sensations from area
  • General Anesthesia: Medication delivered by inhalation or IV that induces state in which patient responds to any stimuli
• Normal stresses on patients are reserved for surgical procedures
  • Local Anesthesia: Caine” medications chemically divided into amide/ester types
  • Makes a body area insensitive to pain without loss of consciousness
  • Can be given topically on mucous membranes or injected to the site

Local and IV Anesthetics

• Local Ester Anesthetics

  • Procaine (Novocain)
  • Benzocaine (Anbesol)
  • Tetracaine (Pontocaine)
  • Cocaine

• Local Amide Anesthetics

  • Lidocaine (Xylocaine)
  • Mepivacaine (Carbocaine)
  • Bupivacaine (Marcaine)

• IV Anesthetics

  • Adjuncts/primary agents for maintaining a state of anesthesia
  • Rapid Onset and Short Duration
  • High lipid solubility
  • Excreted by Kidney and classified as barbiturate, benzodiazepine or miscellaneous

• IV Anesthetics: Common Agents

  • Thiopental (Pentothal)
  • Methohexital (Brevital)
  • Propofol (Diprivan)
  • Etomidate (Amidate)*
  • Ketamine (Ketalar): Induction agent in patients with reactive airway disease (bronchospasm)
  • Midazolam (Versed)
  • Etomidate: 0.3 mg/kg IV with Onset: 10-15 sec and Duration of action 4-10 min.

• "Ideal" sedative for RSI with rapid onset, short duration, lack of cardio depressant effects, safety in patients with head injury, and minimal adverse effects

  • Lacks analgesic effects and has no absolute contraindications in RSI

Additional Anesthetic Factors

• Propofol – 1-2.5 mg/kg IV
  • Onset: 15-45 sec.
  • Duration: 5-10 min.
  • Produces a dose-dependent and potent depression of consciousness ranging from light sedation to a comatose state.
  • Lacks analgesic activity, though has amnesic properties
  • Has Ultrashort onset, brief duration of action, and extreme potency
  • Hypotension, bradycardia, tachycardia can occur

Neuromuscular Blocking Agents (Paralytics)

• History shows that it was first used by South American Indians as Curare
• Used clinically for Muscle paralysis during surgery, conjunction with anesthesia prior to endotracheal intubation, and for Muscle paralysis for mechanical ventilation
• Two Classifications:
  • Non-depolarizing and depolarizing

Non-Depolarizing/Depolarizing Agents

• MOA of Non-depolarizing Agents has competitive inhibition of ACh at nerve-muscle receptor sites without depolarization
  • Blockade can be reversed with Cholinesterase inhibitors that break down Ach
  • Inhibition of cholinesterase allows more Ach to act as an "Indirect Acting" parasympathomimetics
    • Neostigmine and pyridostigmine
• Specific Agents:
  • Pancuronium (Pavulon)
  • Vecuronium (Norcuron)
  • Atracurium (Tracrium)
  • Rocuronium (Zemuron): Has rapid onset and duration of 30-40 min.
  • Mivacurium (Mivacron)/Cisatracurium (Nimbex)/Doxacurium (Nuromax)
• Side Effects:
  • Hypotension, prolonged apnea, tachycardia, histamine release, and bronchoconstriction
• Depolarizing Agents have MOA in which Depolarization does occur
  • Muscle membrane stays in a refractory state that makes further contraction impossible till drug is metabolized
  • No antidote for reversing blockade with short-acting metabolites of cholinesterase
• Succinylcholine (Anectine) 1.5 mg/kg IV is a specific Depolarizing Agents with onset 45 sec.
  • Lasts 6-10 min and it is known as “gold standard” for quick action intubation because it works quickly at vocal cords
  • Onset is rapid and duration is short with bolus/infusion qualities
    • SE: Cardiovascular, hyperkalemia, malignant hyperthermia, fasciculations, rise in ICP, IOP, IGP, histamine release
• Contraindications:
  • Major Burns during the past year
  • Crush Injuries
  • Malignant hyperthermia
  • Hyperkalemia/Elevated ICP

Side Effects of NMBA

• Side Effects of depolarizing agents include Histamine release and Muscle Soreness
• Prolonged Duration of Action
  • Inherited Abnormality with Cholinesterase of atypical molecular structure
  • Requires Hours of Supported Ventilation
• Sedation MUST precede use of paralytics
• Drugs used for Sedation consists of benzodiazepines and intravenous anesthetic agents
• Drugs used for Paralysis consists of depolarizing NMBA (succinylcholine) and Non-depolarizing NMBA – gantacurium, rocuronium, cisatracurium, vecuronium, pancuronium