Drug Assisted Intubation Procedure Review
There is no doubt that the use of Drug Assisted Intubation (DAI) in the pre-hospital environment has been one the most hotly debated topics in recent years. Many people question whether paramedics should be intubating, let alone performing this procedure. Because of this, it is imperative that we endeavor to maintain proficiency in this important skill. Please review this information and feel free to pass along tips that may help others.
- Patient is unable to protect and/or maintain an adequate airway despite the use of basic airway adjuncts.
- Patient is unable to maintain appropriate oxygenation/ventilation despite the use of medications, BVM, and/or CPAP.
- Anticipated airway compromise due to trauma, burns, or head injury.
- Major facial or laryngeal trauma.
- Upper airway obstruction.
- Distorted facial or airway anatomy.
- Significant burns greater than 24 hours old
- History of neuromuscular disease; myasthenia gravis, amyotrophic lateral sclerosis, muscular dystrophy, Guillain-Barre syndrome
- Chronic renal failure and on hemodialysis
- The patient is less than 12 years of age
- Patient or family history of malignant hyperthermia
- Less than 2 EMT-Paramedics on scene able to participate in patient care
The Medications [top]
Lidocaine has been used as an adjunct to anesthesia since the early 1960s. Initially, lidocaine was used to blunt the cough elicited from endotracheal stimulation. However, in the 1970s, it began to be used to improve hemodynamic stability. More recently, lidocaine has been studied as an agent used to prevent the rise in ICP associated with laryngeal stimulation. Lidocaine is administered as an IV bolus of 1 mg/kg. Lidocaine should be administered 2-3 minutes prior to intubation, studies have demonstrated maximum efficacy at this duration.
Etomidate is the medication of choice for the initial sedation of the patient. Etomidate is a gamma-aminobutyric acid (GABA) agonists like Versed. But unlike Versed, Etomidate does not affect blood pressure in the same manner. This property makes this an ideal medication in patients with low blood pressures. Etomidate has both sedative and hypnotic effects, but does not have any analgesic effects. Etomidate’s initial onset is 30-60 seconds, with peak effect within 1 minute. Etomidate is also short acting, effects lasting 3-5 minutes. Because of this, the patient must be re-sedated with a longer acting agent after the airway is placed. Dosage for Etomidate is 0.3 mg/kg IV, the typical adult dose is 20mg.
Succinylcholine is considered an ideal paralytic agent because of its rapid onset of action (within 45 seconds) and the drug's short duration (4-5 minutes). Succinylcholine binds to acetylcholine receptors at the neuromuscular junction and stimulates depolarization of the muscle cell. Succinylcholine produces continuous stimulation of the muscle cell, which is unable to return to its resting state and paralysis occurs. Succinylcholine dosage is 1.5 mg/kg IV.
Vecuronium is an amino-steroid non-depolarizing paralytic agent. Vecuronium competitively binds at the post synaptic receptor sites preventing acetylcholine from depolarizing the muscle cell, thus causing paralysis. Vecuronium has a longer onset of action than Succinylcholine, 2 ½ min for maximum blockade. Vecuronium also has an increased duration time, 45-60 min. Vecuronium should be administered only after the patient has been successfully intubated, and the airway has been verified and properly secured. Dosing for Vecuronium is 0.1 mg/kg IV.
Benzodiazepines, such as Versed, are sedative-hypnotic agents that act as indirect gamma-aminobutyric acid (GABA) agonists. They are effective anxiolytic and amnestic agents and, as such, are popular for sedation. Midazolam has a rapid onset and relatively short duration of action, is considered an ideal choice for maintaining sedation after an airway has been established. Versed produces sedation within 1-2 minutes, with its effects lasting 15-30 minutes. When given to maintain sedation post airway placement, administer an initial dose of 0.5-2mg slow IV push. Repeat doses may be given to a total of 5mg, in order to maintain adequate sedation.
The Procedure [top]
Assess the Airway
Before jumping into the procedure right away, take a moment to quickly assess the patient, in particular the airway. By assessing the airway you can anticipate any difficulties that you may face. It has been said: “The difficult airway is something you anticipate, the failed airway is something you experience.” (Ron Walls) When you assess the airway and anticipate potential problems, you can prevent failure for both you and the patient.
An easy way to assess the airway and predict potential difficulties is to use the LEMON method.
Look: Look externally for signs that the patient may be difficult to intubate: malformations, facial hair, facial shape, buck teeth, obesity, or a short neck.
Evaluate: Use the 3-3-2 rule to evaluate the patient’s external airway anatomy. (This should be done while the patient is sitting upright)
3 fingers between the patient’s teeth
3 fingers between the tip of the jaw and the beginning of the neck (under the chin)
2 fingers between the thyroid notch and the floor of the mandible (top of the neck)
If the patients anatomy is smaller than these measurements anticipate a difficult airway.
Mallampati: Use the Mallampati chart to score the airway. The higher the score the more difficult the airway will be.
Obstruction: Assess for any obstructions: foreign body, tumors, abscess, epiglottis or hematomas
Neck Mobility: Patient’s with limited neck mobility, whether from spinal immobilization or underlying medical conditions, will potentially have a difficult airway.
Prepare the Equipment
After assessing the patient’s airway, all equipment and medications should be prepared, tested, and be ready to used prior to beginning. This means assembling all equipment and drawing up all of the medications. Needed equipment includes:
- Appropriately sized bag-valve-mask with reservoir
- Suction (fully hooked up and working)
- Oxygen (hooked up to a bag-valve mask)
- Laryngoscope with appropriate sized blades and functioning lights
- Appropriately sized endotracheal tube with stylet (have immediately available at least one size above and below the anticipated size)
- Alternative airway equipment at the operator's side.
Equipment for an alternative airway should always be readily available. This includes an alternate airway device such as the King LTD. In addition, the surgical cricothyrotomy kit should be available if an emergency airway is needed.
Monitor the Patient
The patient must be closely monitored before, during, and after intubation. All patients must be placed on the cardiac monitor and have continuous pulse oximetry at all times. The patient’s vital signs should be measured prior to and after placing the airway. The patient’s heart rate and pulse ox must be closely monitored during intubation. Sudden bradycardia or tachycardia, or marked decrease in oxygen saturation may be an indication of patient distress. If patient distress is suspected, the intubation attempt should be stopped and the patient ventilated with high flow 02.
Preoxygenate the Patient
Pre-oxygenation replaces the patient's functional residual capacity of the lung with oxygen. This gives a limited time of security if the patient is apneic during the drug assisted intubation. If the patient is placed on high flow oxygen (assisted respiration with bag-valve-mask or non-rebreathing high- flow mask) as soon as intubation is considered, the patient has already been pre-oxygenated prior to the intubation.
Administer the Medications
Once all equipment has been prepared, medications have been drawn up, and the patient has been pre-oxygenated it is time to begin the drug assisted intubation. This should not be a rushed procedure. Give each medication approximately one minute apart, this gives time for the medications to begin working fully.
- T-minus 3 Minutes: Lidocaine, if indicated - 1 mg/kg
- T-minus 2 Minutes: Etomidate - 0.3 mg/kg
After administration of the initial sedative use the Sellick’s Maneuver to help occlude the esophagus and reduce the chance of aspiration. In order to properly apply the Sellick’s Maneuver, locate the cricoid cartilage and apply downward pressure to press the esophagus against the cervical spine. The cricoid cartilage is located just below the thyroid cartilage, aka the Adam’s apple. Be sure not to press on the thyroid cartilage, this can occlude the airway.
- T-minus 1 Minute: Succinylcholine - 1.5 mg/kg
Intubate the Patient
Intubation is performed after there is full relaxation of the airway muscles. This usually occurs about 45-60 seconds after administration of succinylcholine. Cricoid pressure should be maintained until the cuff is inflated and the tube position verified.
Using BURP can help enhance visualization of the vocal cords during intubation. To use the BURP method, simply apply Backward, Upward, and Rightward Pressure on the Thyroid Cartilage. This is different from the Sellick’s Maneuver which applies downward pressure on the Cricoid cartilage.
If intubation fails, maintain cricoid pressure and ventilate the patient with a bag-valve mask. After the patient is re-oxygenated, either attempt another intubation (times 1 additional attempt) or employ an alternative airway technique. If an additional dose of sedative or paralytic agent is required, it should be employed about 5 minutes after the first. If the patient’s condition warrants, use the BVM with an oralphangeal airway until arrival at ED or return of spontaneous respirations is acceptable.
After intubation, the tube must be confirmed to be in the trachea. This verification is more important than the intubation itself. There is no sin in an esophageal intubation, but there is much sin in not recognizing esophageal placement. Assessment of endotracheal tube placement is done by several methods: Visualization, Auscultation, End Tidal CO2 detection, and Pulse Oximetry.
Visualization: In a perfect intubation, the tube will be seen to pass through the cords. Unfortunately, in the stress of an emergency intubation, with vomitus or blood and with difficult anatomy or cervical immobilization, visualization of the tube's passage through the cords is all too often a fond aspiration.
Likewise, it is difficult to look for even expansion of the chest without any gastric distention in the immobilized patient with potential chest trauma. It is nice to see, but can't be depended on as the only sign of a good intubation.
Auscultation: After visualizing the tube pass thru the vocal cords the next step is to assess the patient’s breathe sounds. This should be a 5 point check. First listen over the epigastrium, if bubbling is heard, this indicates placement of the ET tube in the esophagus and the tube should be removed and the patient ventilated with the BVM. If no gastric sounds are heard then listen for equal bilateral lung sounds. Breath sounds are assessed at the level of the 3rd intercostal space mid-clavicular and the 5th intercostal space mid-axillary. Breath sounds should be equal bilaterally. If sounds are only heard on the right side, suspect that the tube as been advanced into the right main stem and pull back on the tube slightly until bilateral sounds are heard.
Carbon Dioxide Detection: End-tidal carbon dioxide detection/measurement has become the gold standard for assessing proper tube placement. By detecting the presence of carbon dioxide in exhale air, either by colorimetric device or capnography, we can say with confidence that the ET tube has been properly placed. During states of decreased profusion end-tidal C02 may be difficult to detect, but will still produce a normal shaped wave form using capnography. Recent ingestion of carbonated beverages may also show false levels of end-tidal C02, but will not produce a normal wave form. By contentiously monitoring ETC02 levels using capnography we can instantaneously see when an ET tube becomes displaced by the absence of a normal wave form. In addition, a patient’s perfusion status can by assessed by the use of capnography, sudden changes in ETC02 level can indicate changes in perfusion at the cellular level of the respiratory system.
Pulse oximetry: Pulse oximetry has long been a standard method of monitoring the patient with respiratory difficulties. If oxygen saturation is rising, or stays at an acceptable level in a paralyzed patient, the endotracheal tube is certainly in the appropriate place. Unfortunately, a pulse oximeter is not particularly useful in the patient with profound shock or cardiac arrest.
If at any time there is doubt about proper placement of the advanced airway, it is safer to remove the airway, ventilate and reattempt insertion, or choose an alternate device.
Secure the Tube
After you have verified that the airway is in the proper place, the airway must be secured. Readymade, purpose built, commercial devices provide a quick easy way to secure the ET tube. Be sure to note tube depth before and after securing the tube, this will allow you to assess if the tube was moved accidently while placing the securing device.
Security of the tube includes sedation so the patient will not move and ensuring that the patient's head does not move during transport after intubation. Consider placing a c-collar on the patient, or at least using head blocks to prevent excess movement of the patient’s head during transport. After each movement of the patient, reassess breath sounds and closely monitor end tidal C02 levels and waveform.
Administer Long Acting Paralytic
Norcuron 0.1 mg / kg, repeat 15 to 30 minutes to maintain paralysis
After the airway has been established, confirmed, and properly secured, the patient will require continued sedation. Remember that Etomidate only sedates the patient for approximately 5 minutes. Versed should be used as a longer acting sedative. Administer an initial dose of 0.5-2mg slow IV push. Repeat doses may be given to a total of 5mg, in order to maintain adequate sedation.
Remember that paralyzing a patient without proper sedation is cruel!!
Think About These Do's and Don'ts [top]
- Have 2 Paramedics while performing the Drug Assisted Intubation
- Compete the NCOEMS Advance Airway form completely, and turn in to medical control along with a copy of the Patient Care Report
- Have all equipment ready - including suction
- Explain to patient what's going to happen, if necessary
- Label drugs as they are drawn
- Use all PPE - including face shield
- Maintain cricoid pressure to prevent aspiration
- Keep track of BVM face mask in case of failed attempt
- Protect patients eyes by applying KY jell and/or taping shut
- Monitor End Tidal C02 continuously after placing the airway
- Monitor heart rate – an increase could indicate need for additional sedation
- Start until all equipment is ready - including suction
- Toss BVM face mask after intubation, in case of failure
- Rush the process, allow the drugs to work
- Interrupt ventilation longer than 30 seconds
- Hyperventilate after intubation – 10-12 bpm is adequate, maintain End Tidal C02 levels at 35-45 mmHg