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22 October 2009

Rapid Sequence Intubation (EAM part 2)

Rapid Sequence IntubationRapid sequence intubation (RSI) consists of a series of discrete steps that are best followed to insure the greatest success. The patient should first be evaluated for the presence of a difficult airway and the ability to ventilate with a bag-valve-mask should intubation not be successful. It is obvious that the intubation should take place in a room that is prepared in advance with all equipment needed for resuscitation should that be necessary. It is the physician’s responsibility to make sure that all equipment is present and in working order before proceeding! Although nurses may assure you that everything is in working order, the physician is ultimately responsible and will be the one to have to handle the problem if some critical equipment is not functioning or a critical drug is not available.

1. Preoxygenation “Bagging” the patient unnecessarily prior to RSI increases the possibility of vomiting and aspiration. Critical to the philosophy of rapid sequence is the “no bagging” principle. Pre-oxygenation is the establishment of an oxygen reservoir within the lungs to permit several minutes of apnea to occur without arterial oxygen desaturation. Pre-oxygenation not only establishes an oxygen reservoir in the lungs, but also creates an oxygen surplus in the blood and body tissue protecting from hypoxia. In the spontaneously breathing patient, administration of 100% oxygen (15 liters of O2 in a non rebreather mask provides 80-90% oxygen) for 5 minutes prior to using paralyzing drugs allows for approximately 5 minutes of apnea before the hemoglobin desaturates below 90% in the adult. (It is of note that this is not the case in a child who has a much lower functional residual capacity and may desaturate after 1 or 2 minutes.) A pulse oximeter should be used throughout the procedure to allow the physician to gauge the oxygen saturation. In situations wherein time is more critical and it is not possible to pre-oxygenate for 5 minutes, a significant pre-oxygenation effect can be obtained by having the patient take 3-5 large capacity breaths on high oxygen.
2. Pretreatment “Pretreatment” is the administration of medications to attenuate the normal physiologic and pathophysiologic reflex responses that are caused by airway manipulation and the physical presence of the endotracheal tube. These are usually medications used to blunt the sympathetic discharge that accompanies laryngoscopy from insertion of the laryngoscope or manipulation of the airway. Situations where pretreatment is desirable include 1) conditions where there is increased intracranial or intraocular pressure, as in a head injured patient; 2) conditions where sympathetic discharge would have deleterious effects on the heart or cardiovascular system as in patients with coronary artery disease, or in children who might have bradycardia and hypotension from airway manipulation; and 3) in patients with airway disease, as in asthma, who might have laryngospasm with airway manipulation. There are also times when it might be advisable to administer a small defasciculating dose of a competitive neuromuscular blocking agent three minutes prior to the administration of succinylcholine. Lidocaine (1.5 mg/kg given 3 minutes prior to intubation) has been shown to suppress the cough reflex and attenuate the increased airway resistance, which results from bronchospasm caused by irritation of the larynx. It also mitigates the effects on a potential increase in intracranial pressure. Thus it should be considered in all patients prior to the administration of a neuromuscular blocking agent who have reactive airway disease or elevated ICP.
Fentanyl (3 micro-gms/kg IV 3 minutes before induction) also attenuates the reflex sympathetic response to laryngoscopy. Fentanyl has no effect on ICP and will cause some hypotension and may suppress respiratory effort. However, it is useful in patients who might be adversely effected by an increase in heart rate or blood pressure. This is especially true in patients with ischemic heart disease, pulmonary edema and cardiogenic shock and in patients with vascular catastrophes like a AAA, subarachnoid hemorrhage or thoracic dissection. Defasciculating agents like vecuronium and pancuronium in small, nonparalyzing doses, given 3 minutes before succinylcholine mitigate against potential increases in intracranial pressure and should be considered when increased ICP is of concern. Lastly, almost all children should receive atropine before airway manipulation to mitigate against the bradycardia and hypotension induced from airway manipulation and laryngoscopy.
3. Paralysis and Induction Approximately 5 minutes after pre-oxygenation has begun and 3 minutes after pretreatment drugs are administered, a sedative and a neuromuscular blocking agent should be rapidly administered to induce rapid loss of consciousness and paralysis. This should not be titrated or done tentatively, but should be done as a push to allow for the full effect of the medication. This provides the best chance at rapid intubation without the possibility of partial or incomplete paralysis. Succinylcholine is the drug of choice for almost all emergency department intubations and should be given in a full dose of at
least 1.5 mg/kg IV push. Since there are no complications from succinylcholine in larger than normal doses, the medication should be “rounded up” and a slightly higher dose given rather than a low dose, which might not induce full paralysis. A sedative should be given almost simultaneously by IV push. This usually will be midazolam and care must be taken as midazolam may cause some hypotension. Another but more expensive drug, Etomidate, is gaining rapid popularity in emergency medicine and eventually may replace Versed. A few seconds after administration of the neuromuscular blocker and sedative, the patient will loose consciousness and respirations will cease. Between 20-30 seconds of apnea is almost universal. Sellick’s maneuver should be applied to the cricoid cartilage to prevent regurgitation of gastric contents and should be maintained throughout the entire sequence until the endotracheal cuff is inflated. It should be noted that Sellick’s maneuver is often improperly performed. Most often those doing the Sellick’s maneuver will press down on the thyroid cartilage instead of the cricoid cartilage. This actually makes intubation more difficult by pushing the cords posterior and out of visualization of the laryngoscopist. It also does not protect the airway as the esophagus is not occluded. Pressure on the cricoid cartilage occludes the esophagus and tilts the cords upward toward the visual axis of the laryngoscopist.
4. Place the tube Approximately 45 seconds after succinylcholine is administered the patients jaw should be tested for flaccidity and intubation should be undertaken. Intubation attempts before 45 seconds and full relaxation are rarely successful. It is hard to wait the full 45 seconds when the patient is apneic. It is also hard not to want to “bag” the patient when he/she is apneic. However, the full 45 seconds should pass before the tube is introduced. Remember- we pre-oxygenated the patient, so there is plenty of oxygen to last for several minutes (usually 5), which is plenty of time to get the patient intubated with minutes to spare. Intubation can proceed calmly in a non- rushed manner. The success rate should be very high and approach 99% using this algorithm.
5. Post intubation care Tube placement must be confirmed. One of the most disastrous complications from RSI is unrecognized esophageal intubations. Proper placement of the tube can be confirmed if the operator actually saw the tube go through the cords. Otherwise, the best method of confirming tube placement is by end-tidal CO2 monitoring or aspiration techniques. An end tidal CO2 monitor can be easily attached to the ET tube and color changes noted. Purple (“problem”) means you are not in the right place. Yellow (“yes”) means you are in the trachea and CO2 is passing by the monitor. If an intermediate color (tan) is detected, tube placement should be immediately checked. In a small number of cardiac arrest cases, no color change may be detected even though the tube is properly placed in the trachea. This is caused by cessation of carbon dioxide production and delivery to the lungs. If a CO2 monitor is not available, another test, based upon the knowledge that rigid walled structures (trachea) will hold their shape in comparison to structures with no support (esophagus) which collapse, may be used. A 30 cc syringe can be attached to the ET tube and the plunger quickly withdrawn. If there is easy flow of air, you are in the trachea, if there is resistance, you are probably in the esophagus. Chest x-ray can not confirm tube placement in the trachea as the esophagus lies directly behind the trachea- placement in either structure will appear the same on the AP chest film.
Absence of breath sounds over the epigastrium, the presence of breath sounds in the lungs and observation of the rising and falling of the chest with ventilation are unreliable signs of endotracheal intubation and should not be relied upon. Pulse oximetry should be used throughout the intubation. Desaturation may suggest esophageal intubation, but desaturation may be delayed several minutes if the patient was properly pre-oxygenated. Desaturation may also occur precipitously when precious little time is available to correct the problem. Therefore, oxygen saturation should not be the only basis used to confirm tube placement. After tube placement is confirmed, attention must be turned to the long term care of the patient on the ventilator. Remember that succinylcholine will last only about 6 minutes and a long acting nondepolorizer such as vecuronium should be administered in full paralyzing doses before the succinylcholine effects subside. Also, since paralysis does not afford sedation or analgesia, a long acting sedative and or analgesia should also be administered to make the patient comfortable.

Reference
Advanced Emergency Airway Management Walls RM, Luten RC, Murphy ME, Schneider RE. 1997


1 comments:

Janak India - Surveying Instrument on December 7, 2010 at 1:42 PM said...

Very nice information post by this blog owenr I want to say thanks for it. I would be like to come again and again on this blog. Good job dear ! Total Station Survey Equipment


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