Advanced Cardiac Life Support (ACLS): Rapid Sequence Induction

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Advanced Cardiac Life Support (ACLS): Rapid Sequence Induction and Intubation

Rapid sequence induction and intubation (RSII) protocol

The RSII protocol is as follows:

1. Obtain brief medical history and perform focused physical examination.

2. Prepare equipment, monitors, personnel, and medications.

3. If neck injury is not suspected, place the patient in the sniffing position. If neck injury is suspected, stabilize the cervical spine.

4. Preoxygenate with FiO2 via 100% mask (nonrebreather preferred). If ventilatory assistance is necessary, ventilate gently.

5. Premedicate as appropriate; wait briefly to allow adequate drug effect after administration.

6. Administer sedation/anesthesia via IV push.

7. Give neuromuscular blocking agent via IV push.

8. Apply cricoid pressure.

9. Assess for apnea, jaw relaxation, and absence of movement (patient sufficiently relaxed to proceed with intubation).

10. Perform endotracheal intubation. If, during intubation, oxygen saturation is inadequate, stop laryngoscopy and start ventilation with bag-mask. Monitor pulse oximetry and ensure adequate oxygen saturation. Reattempt intubation. Once intubated, inflate the cuff to minimal occlusive volume. Be prepared to place rescue airway if intubation attempts are unsuccessful.

11. Confirm placement of endotracheal tube, as follows:

Direct visualization of ETT passing through vocal cords
Chest rise/fall with each ventilation (bilateral)
Five-point auscultation: Anterior chest L and R, midaxillary line L and R, and over epigastrium (no breath sounds over epigastrium); look for tube condensation
Use end-tidal CO2 measured via quantitative continuous waveform capnography; if waveform capnography is not available, use qualitative exhaled CO2 detector or esophageal detector device (aspiration technique).
Monitor O2 saturation (indirect evidence of adequate oxygenation).

12. Prevent dislodgement, as follows:

Secure ETT with adhesive/cloth tape or commercial ETT holder.
Continue cervical spine immobilization.
Continue sedation; add paralytics, if necessary.
Check cuff inflation pressure.

RSII Pre-Event Equipment Checklist

The RSII pre-event equipment checklist is as follows:

Universal precautions (gloves, mask, eye protection)
Cardiac monitor, pulse oximeter, and blood pressure monitoring device
Continuous waveform capnography device or, if not available, exhaled CO2 detector (qualitative) or esophageal detector device (aspiration technique)
Intravenous and intraosseous infusion equipment
Oxygen supply, bag-mask (appropriate size)
Oral/tracheal suction equipment (appropriate size); confirm that it is working
Oral and nasopharyngeal airways (appropriate size)
Endotracheal tubes with stylets (all sizes) and sizes 0.5 mm (in diameter) above and below anticipated size for patient
Laryngoscope (curved and straight blades) and/or video laryngoscope; backup laryngoscope available
Ten-mL syringes to test inflate endotracheal tube balloon
Adhesive/cloth tape or commercial endotracheal tube holder to secure tube
Towels, sheets, or pad to align airway by placing under head or torso
Rescue equipment as needed for difficult airway management or anticipated complications (eg, supraglottic airway, transtracheal ventilation, and/or cricothyrotomy equipment)

Medications

Induction agents are as follows:

Etomidate 0.2-0.4 mg/kg; limit to one dose
- Onset, < 1 minute; duration, 5-10 minutes
- Side effects: myoclonic activity, inhibition of cortisol synthesis for up to 12 hours
Ketamine 1-2 mg/kg
- Onset, < 1 minute; duration, 10-20 minutes
- Side effects: hypertension, tachycardia, increased secretions, emergence reactions, hallucinations
Midazolam 0.1-0.3 mg/kg; max single dose, 10 mg
- Onset, 2-5 minutes; duration, 15-30 minutes
- Side effect: hypotension
Propofol 1-2 mg/kg
- Onset, < 1 minute; duration, 5-10 minutes
- Side effects: pain upon infusion; hypotension, especially in patients with inadequate intravascular volume

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Muscle relaxants are as follows:

Cisatracurium 0.4 mg/kg
- Onset, 2-3 minutes; duration, 90-120 minutes
Rocuronium 0.6-1.2 mg/kg
- Onset, 60-90 seconds; duration, 45-120 minutes
Succinylcholine 1-1.5 mg/kg
- Onset, 45-60 seconds; duration, 5-10 minutes
- Multiple contraindications and precautions
Vecuronium 0.1-0.2 mg/kg
- Onset, 1-3 minutes; duration, 45-90 minutes

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Adjuncts are as follows:

Atropine 0.01-0.02 mg/kg; maximum single dose, 0.5 mg
- Onset, 1-2 minutes; duration, 2-4 hours
- Side effects: tachycardia, inhibition of bradycardic response to hypoxia
Fentanyl 2-5 mcg/kg
- Onset, 1-3 minutes; duration, 30-60 minutes
- Side effects: hypotension in high doses, especially when combined with sedatives
Glycopyrrolate 0.005-0.01 mg/kg; maximum single dose, 0.2 mg
- Onset, 1-2 minutes; duration, 4-6 hours
- Side effects: tachycardia, inhibition of bradycardic response to hypoxia
Lidocaine 1-2 mg/kg; maximum single dose, 100 mg
- Onset, 1-2 minutes; duration, 10-20 minutes
- Side effects: myocardial depression, CNS depression, seizures in high doses

Additional Information

The above American Heart Association (AHA) protocol^�covers the basic steps for rapid sequence induction and intubation (RSII). Prior guidelines releases covered more details for specific steps; however, some steps are considered controversial (eg, the use of premedication and appropriate cricoid pressure). Some information is also outdated (eg, the use of propofol in egg/soy allergy^�and the use of a minimum dose for atropine). For completeness, further details on these topics are included below.

Preparation Tip

Mnemonic:SOAP ME, used for initial equipment check prior to administering medications, as follows:

S: Suction, turned on and working
O: Oxygen, including backup supply
A: Airway equipment, including laryngoscopes, handles, endotracheal tubes, stylets, supraglottic airways
P: Pharmaceuticals, including induction agent, muscle relaxant, adjuvants, emergency medications
M: Monitors, with audible SpO ₂ tone and blood pressure at least every 5 minutes
E: Emergency equipment, including defibrillator and invasive airway equipment

General RSII Tips

When significant difficulty is anticipated, neuromuscular blockade should be used with caution, and airway rescue devices, including surgical airway equipment, should be immediately available.

The key features of RSII are adequate preoxygenation and avoidance of positive pressure ventilation with the goal of reducing the risk of pulmonary aspiration.

For patients who are able to follow commands, consider oral sodium citrate/citric acid 30 mL prior to RSII to reduce the risk of aspiration pneumonitis.

Cricoid pressure is controversial but may be considered in individuals adequately trained in performing this procedure, and pressure should be released if it obstructs the laryngeal view during endotracheal intubation.

The hemodynamic and physiologic consequences of the administered sedative, analgesic, and muscle relaxant medications, as well as the airway management procedure itself, need to be anticipated and managed in all patients who require airway intervention. Hypotension can occur with any induction agent due to positive pressure ventilation and reduction of sympathetic activity.

Priorities in descending order include (1) avoidance of hemodynamic collapse, (2) reducing the risk of pulmonary aspiration, (3) analgesia, and (4) amnesia. RSII is an emergency procedure; ensuring analgesia and/or unconsciousness is not required if typical induction dosing could result in hemodynamic collapse.

Preoxygenation Tips

These are as follows:

Administer 100% FiO2 via non-rebreather if the patient is conscious
If apneic, 100% FiO2 may be delivered via bag valve mask (BVM)
- Spontaneous ventilation using a BVM is not recommended as this increases work of breathing and may not deliver a consistent FiO2
Preoxygenation typically takes 3-5 minutes with normal respiration, however, 8 large tidal volume breaths can substitute in urgent situations
Consider 20-degree head-elevated position for preoxygenation
- In spine precaution patients, consider 30-degree reverse Trendelenburg
Consider the apneic oxygenation technique via nasal cannula with 15 LPM oxygen during after induction and throughout laryngoscopy

Premedication Tips

Lidocaine is not recommended for routine use before RSII. Lidocaine pretreatment does not effectively blunt increases in intracranial pressure (ICP). Lidocaine 1.5 mg/kg IV may be considered if there is a specific need to suppress the cough reflex and/or reduce anesthetic requirements.

Fentanyl may not achieve the desired response in time during RSII. Typically, more than 6 minutes are needed, and 2 mcg/kg IV only partially blunts the hemodynamic response.

Atropine is not recommended for routine use prior to intubation, with the exception of infants (children younger than 1 year). Atropine 0.02 mg/kg IV may be considered in children prior to receiving succinylcholine, particularly a second dose of succinylcholine.

Defasciculation with a nondepolarizing relaxant prior to succinylcholine is not recommended for RSII, and expertise is needed for use in elective settings.

Induction Agent Tips for Use in Trauma Patients

Ketamine (1-2 mg/kg IV) is appropriate in nearly all circumstances owing to its hemodynamic stability and ability to provide analgesia with amnesia. Use caution in patients who cannot tolerate hypertension or tachycardia.

Etomidate (0.2-0.3 mg/kg IV) is another option, although some studies show negative outcomes in trauma patients. No dose reduction is needed in patients with shock or elderly patients, and 0.3 mg/kg IV should be the minimal dose for patients in hemorrhagic shock. Use of etomidate alone without a muscle relaxant can result in trismus.

Propofol should be used with caution owing to a narrow therapeutic index and the possibility of potentiating hemodynamic instability. Dosing should be greatly decreased in patients with hemorrhagic shock, with appropriate doses being 20% normal (ie, 0.4 mg/kg IV). Propofol should be considered in patients with isolated brain injury.

Benzodiazepines (eg, midazolam 0.1-0.3 mg/kg IV) are considered second-line agents, as their onset time is slower than that of the muscle relaxants.

Muscle Relaxant Tips for Use in Trauma Patients

Rocuronium (1.2 mg/kg IV) or succinylcholine (1 mg/kg IV) are the agents of choice owing to their rapid onset of action.

The muscle relaxant should be given immediately after administration of an anesthetic induction agent or may be administered alone if the patient is unconscious and hemodynamically unstable.

Succinylcholine has multiple adverse side effects and contraindications, which may be undesirable in critically ill patients. Succinylcholine is associated with increased mortality in patients with traumatic brain injury.

If reversal of neuromuscular blockade is needed after rocuronium, sugammadex should be considered.

Additional Information: Cricoid Pressure

The use of cricoid pressure is controversial and is not currently considered a standard of care during RSII despite common usage.

Several studies have shown conflicting results, and some criticize the use of cricoid pressure, but the overall evidence is poor.^�

Some studies suggest cricoid pressure worsened laryngeal view, which delayed intubation and increased the risk of pulmonary aspiration.

A provider trained in the performance of cricoid pressure should administer the procedure, as too little pressure causes incomplete occlusion and too much pressure compresses the airway and limits laryngeal view.^�As one article puts it, cricoid pressure is not a “simple maneuver that can be taught to an assistant in a few seconds.”^�The appropriate force is 10 N (1 kg) in an awake patient and 30 N (3 kg) upon loss of consciousness.^�If the glottic view is obstructed or mask ventilation or tracheal intubation suboptimal, the release of cricoid pressure is justified.

Many advocates of cricoid pressure suggest incorrect application is the reason for problems and complications seen; thus, a trained provider is important. Examples of cricoid pressure misuse include incorrect timing, use of excessive force, and compression of the thyroid cartilage instead of the cricoid cartilage.

If mask ventilation is needed between intubation attempts, cricoid pressure may limit the efficacy of ventilation.^�

Minor complications of cricoid pressure application include discomfort, retching, and nausea in the awake patient.

Major complications include esophageal rupture, esophageal injuries due to the presence of sharp objects, fracture of the cricoid cartilage, and potential worsening of cervical spine injuries.

Additional Information: Preoxygenation

Preoxygenation is generally considered the most important part of RSII, as it extends the period of safe apnea time while mask ventilation is being avoided.

For spontaneously breathing patients, a standard reservoir face-mask (“non-rebreather”) is appropriate for preoxygenation. Flow rates higher than 15 LPM may be needed, which can often be achieved by continually opening the oxygen valve on the regulator even though they are calibrated to 15 LPM.^�

Spontaneous ventilation using a BVM is not recommended, as this increases work of breathing and may not deliver a consistent FiO2. Some of these devices deliver near room-air in patients who are spontaneously breathing.^�

Preoxygenation typically takes 3-5 minutes with normal respiration; however, 4-8 large tidal volume breaths can substitute in urgent situations.^�

The head-elevated (back-up) position of 20° has been shown in several studies to improve preoxygenation^�and should be considered. This position has also been shown to improve laryngeal view during intubation.^�For patients with spinal injury, a reverse Trendelenburg position of 30° can be used.^�

Apneic oxygenation technique (15 LPM nasal cannula during laryngoscopy) is safe and has been shown in many studies to prolong apnea time during intubation.

Additional Information: Nonparticulate antacids

Sodium citrate/citric acid 30 mL is used in conscious patients to rapidly increase gastric pH prior to induction of anesthesia.

In patients at an increased risk for aspiration (ie, trauma patients), nonparticulate antacids may be considered in accordance with the American Society of Anesthesiologists’ guidelines.^�

Preprocedural use has been shown to reduce the risk of aspiration pneumonitis, particularly in the obstetrical population.

Additional Information: LOAD Mnemonic

LOAD (lidocaine, opioid, atropine, defasciculating agent) is a commonly used mnemonic device for premedication prior to RSII.

The idea is to prevent side effects that are associated with succinylcholine, laryngoscopy, and endotracheal intubation. These undesired effects include bradycardia, tachycardia, hypertension, and increased ICP.

Fortunately, several studies have been done on these medications and their ability to reduce the side effects.

Unfortunately, many of them do not work, but this mnemonic continues to be taught. Some of the studies that have shown these drugs ineffective are decades old, yet the mnemonic still persists.

Additional Information: Lidocaine Pretreatment

Lidocaine can be used during rapid sequence induction and intubation (RSII) specifically to blunt the cough reflex and to reduce anesthetic requirements.

However, there is controversy given the lack of evidence for benefit and because of the risk of hypotension with administration.^�

A systemic review of the literature has not been able to show any evidence of reduced ICP with lidocaine prior to RSII and also showed no positive effect on neurologic outcomes.^�

In addition, the optimal time for lidocaine premedication effect is 3 minutes, which may not be practical in an emergency situation.^�

The most appropriate dose prior to intubation is 1.5 mg/kg.^�This dose has been shown to decrease anesthetic requirements during intubation.^�However, this dose is ineffective at reducing the hemodynamic response to laryngoscopy and intubation.^�A dose of 3 mg/kg can blunt the hemodynamic response^�; however, 3 mg/kg is higher than what is typically recommended for RSII.

Additional Information: Opioid Pretreatment

Fentanyl and its derivatives are the most commonly used to blunt hemodynamic effects during laryngoscopy and intubation. Alfentanil and remifentanil have rapid onset but are not commonly used outside of the operating room.

The typical time needed for fentanyl effect before intubation is 6.4 minutes^�at a dose of 2 mcg/kg, which is generally not practical for emergency indication and intubation. Up to 10 minutes may be needed.^�

Fentanyl 2 mcg/kg only partially blocks hypertension and tachycardia. A dose of 6 mcg/kg is much more effective;^�however, this is a much higher dose than is typically recommended for RSII. Even higher doses, between 11 and 75 mcg/kg, have been described to prevent most responses to intubation, although side effects may be serious. Dosing for fentanyl can be reduced by 50% in patients with severe blood loss.

Additional Information: Atropine Pretreatment

Atropine has been proposed for preventing bradycardia in children due to laryngoscopy and for preventing bradycardia associated with succinylcholine.

It is reasonable to use atropine routinely before intubation in infants,^�and this may reduce the risk of new arrhythmias.^�

The use of atropine pretreatment in adults is not recommended.

Although controversial,^�atropine may be considered in children before intubation if they will be receiving succinylcholine.^�In children older than 1 year, the sympathetic nervous system has matured and bradycardia due to laryngoscopy is less likely. Several studies have shown no benefit in using atropine in children older than 1 year.^�

Sinus bradycardia with succinylcholine is more common after a second dose,^�so administration of atropine in this setting is not unreasonable.

Additional Information: Defasciculation

Defasciculation with a nondepolarizing muscle relaxant has been proposed to prevent side effects associated with succinylcholine, mostly myalgias. There is debate about whether succinylcholine increases ICP,^�with most studies showing no association. For elective neurosurgery, succinylcholine may increase ICP, which can be blunted with a defasciculating dose.^�

The appropriate defasciculating dose for a nondepolarizing muscle relaxant is 10% of the ED95. Unfortunately, this has been incorrectly interpreted as 10% of the intubating dose in several textbooks. A typical intubating dose is about 2 times ED95, so the appropriate defasciculating dose is 5% (1/20th) of the intubating dose. An unacceptably high incidence of symptoms is seen when the incorrect dose is used.^�

The defasciculating dose for rocuronium is 0.03 mg/kg given 3-5 minutes before induction and succinylcholine administration. Note that this would be 3 mg for a 100-kg patient.

Succinylcholine dosing should be increased to 1.5-2 mg/kg after defasciculation owing to antagonism between these medications.

Additional Information: Etomidate

Dosing is 0.2-0.3mg/kg IV bolus, and up to 0.6mg/kg is safe. Dosing adjustments do not need to be made for infants, elderly patients, or debilitated patients.

Etomidate should not be underdosed in patients in hemorrhagic shock, with 0.3 mg/kg IV being the low end for dose choice.^�Despite generally maintaining hemodynamic stability, hypotension can occur in patients with shock who are receiving etomidate.^�

Negative outcomes have been seen with etomidate use for intubation in trauma patients;^�prospective data was used in this study. Retrospective studies^�have also shown an increase in mortality, though this may have resulted from patient selection.

Owing to the adrenal suppressing effects, etomidate is not recommended in patients with sepsis.^�Patients do not appear to benefit from steroids given after etomidate in an attempt to overcome the adrenal suppression.

If muscle relaxants are not used, trismus (lockjaw) can be seen with etomidate injection.^�

Etomidate can provoke seizures in patients with a history of seizures or with head injury.

Additional Information: Ketamine

Ketamine has a good therapeutic index, so there is no reason to underdose, even in patients with major blood loss.^�

Ketamine increases sympathetic tone and has analgesic effects, which are both beneficial for patients who are hemodynamically unstable.

Multiple studies have shown ketamine to have good cardiovascular stability with induction, even in very sick patients.^�

The cardio-depressant effects of ketamine are postulated to lead to hypotension in catecholamine-depleted patients (eg, ICU patients); however, the sympathomimetic effects usually overshadow this.

Most of the recent studies and meta-analyses show that ketamine does not increase ICP.^�

Maintaining normocapnia (normal ETCO2) blunts the ICP effect.^�

There is no evidence that ketamine causes harm in patients with traumatic brain injury; in fact, it may be helpful in these patients.^�

Intramuscular (IM) induction dosing is 4-10 mg/kg IM (4 mg/kg typical); however, this is not an appropriate route for administration for RSII.

Sympathomimetics such as ketamine are best avoided when resultant tachycardia and hypertension would be detrimental. Alternatively, large-dose opioids (eg, fentanyl 2-5 mcg/kg) may be given to blunt this response.

Additional Information: Propofol

Propofol is a useful induction agent, particularly in the elective setting, as it has multiple beneficial properties, as follows:

It rapidly causes loss of consciousness and amnesia.
It blunts airway reflexes better than ketamine or etomidate, facilitating intubation, even if muscle relaxants are not given.
It causes bronchodilation, making it useful for severe asthma attacks and other forms of bronchospasm.
It has antiemetic properties, has anticonvulsant properties, and decreases ICP, making it useful in most neurologic injuries.
It rapidly clears from the plasma, making for less of a “hangover” effect when compared with other agents.

Propofol is useful in hypertensive patients and in patients with traumatic brain injury, as long as cerebral perfusion pressure is maintained.

Propofol should be used with caution in trauma patients owing to a narrow therapeutic index and the possibility of potentiating hemodynamic instability. Hypotension due to significant vasodilation occurs in up to 1 in 4 adults and 1 in 6 children. The effect on systemic blood pressure is more prominent in hypovolemic patients and elderly patients. Propofol also blunts the baroreceptor reflex, which would normally lead to an increased heart rate with hypotension.

Dosing should be greatly decreased in patients with hemorrhagic shock, with an appropriate dose being 0.4 mg/kg. Expertise is needed for propofol dosing given the narrow therapeutic index and wide variation in dosing, depending on the severity of shock. Furthermore, the use of vasopressors early in trauma resuscitation has been shown to increase mortality.^�

Propofol seems to be the best induction agent for patients with increased ICP. For patients with traumatic brain injury, a single episode of hypotension can double mortality the mortality risk.^[66]This should be kept in mind when using propofol, which can decrease blood pressure significantly if overdosed or used in hypovolemic patients; use caution.

Additional Information: Midazolam

Dosing is 0.1-0.3 mg/kg IV, with a typical maximum single dose of 10 mg. Dosing should be toward the lower end (eg, 0.15 mg/kg IV) in elderly patients.

Onset can take 2-5 minutes, which makes midazolam less desirable for RSII.

Compared with the other induction agents discussed, the duration of action of midazolam is significantly longer and may last up to 1 hour.

The dose needed to cause anesthesia can be reduced in the presence of fentanyl, as the drugs are additive and slightly synergistic.^�In healthy adults, midazolam 0.15 mg/kg IV (half dose) is all that is required if fentanyl 2 mcg/kg IV is also administered.

Additional Information: Succinylcholine

Dosing is 1 mg/kg IV for rapid sequence induction and intubation.

In the non-RSII setting, dosing is typically around 0.6 mg/kg IV, and the effective dose for intubation is 0.3 mg/kg.^�

Dosing related side effects increase with doses >1 mg/kg.

Succinylcholine 1 mg/kg IV for RSII is associated with excellent intubating conditions in 100% of cases.^�

Although not advocated here, succinylcholine 0.6 mg/kg IV for RSII provides excellent intubating conditions in most cases.^�

A dose of 1.5 mg/kg IV is appropriate after a defasciculating dose of a nondepolarizing relaxant is given, but not for routine RSII.

Succinylcholine 2 mg/kg IV is appropriate only for infants since infants have an increased volume of distribution.

Giving a 70-kg patient 200 mg (10 mL syringe of 20 mg/mL) would be nearly 3 mg/kg, higher than any intubating dose described in the literature.

Studies have shown no advantage for doses >1.5 mg/kg.^�

Intramuscular dosing in children is 4-6 mg/kg IM with a typical maximum dose of 150 mg IM, although this is not appropriate for RSII.

Using succinylcholine instead of rocuronium in case return of spontaneous respiration is needed (eg, difficult airway) is not a practical approach. Critical desaturation will occur before the patient returns to an unparalyzed state, even with adequate preoxygenation. Most patients who require RSII in emergency settings are unlikely to return to consciousness or have adequate respirations after receiving sedatives and/or induction agents.

Contraindications include malignant hyperthermia (MH), hyperkalemia, conditions predisposing to exaggerated potassium release, intracranial hypertension, and penetrating eye injuries.

There is an FDA Black Box warning for succinylcholine use in boys owing to cases of hyperkalemia-induced cardiac arrest in patients who were later found to have undiagnosed neuromuscular disorders. Succinylcholine is one of the few triggers of malignant hyperthermia. Masseter muscle rigidity (MMR), also known as trismus or “jaws of steel,” can occur with succinylcholine administration and may last up to 30 minutes.

Adverse effects include tachycardia, bradycardia, arrhythmias, hyperkalemia, fasciculations, myalgia, sustained muscle contractions, malignant hyperthermia, masseter muscle rigidity, increased intraocular pressure, increased ICP, histamine release, increased intragastric pressure, anaphylaxis, and cardiac arrest.

Hyperkalemic cardiac arrest can occur after succinylcholine administration in patients who are predisposed to exaggerated potassium release.^�See the table below.

Succinylcholine is also associated with histamine release, which can cause hypotension and tachycardia.

Neuromuscular blocking agents, succinylcholine in particular, are the most common causes of drug-induced anaphylaxis after RSII.^�

Repeated dosing of succinylcholine can result in bradycardia, as well as prolonged duration of action, known as a phase II block.

Succinylcholine is associated with increased mortality in patients with severe brain injury.

Additional Information: Rocuronium

Rocuronium avoids many of the adverse effects and contraindications associated with succinylcholine.

There are no FDA Black Box warnings or major contraindications to the use of rocuronium.

The onset of action for rocuronium (RSII dose) and succinylcholine are comparable (both less than 1 minute).^[82]The onset for rocuronium 0.6 mg/kg IV is approximately 89 seconds; note that this is the non-RSII (elective intubation) dose. Onset for rocuronium 1.2 mg/kg IV is 55 ± 14 seconds. Onset for succinylcholine is 50 ± 17 seconds.

Rocuronium has a much longer duration of action than succinylcholine, which typically mandates the use of a sedative infusion after intubation.^�Emergence occurs within 10 minutes for the commonly used induction agents, except for midazolam; this is the period in which awareness typically occurs. However, awareness can occur during intubation if a slow-onset induction agent (eg, midazolam) is used or if poor techniques are used.

Although not typically used, 2 mg/kg IV results in perfect intubating conditions in more than 90% of cases.^�

Two techniques that are not recommended are the “priming” and the “timing” techniques. The priming technique involves giving a small dose of a nondepolarizing muscle relaxant, waiting about 5 minutes, and then giving the full dose along with an induction agent. The timing technique involves giving the full dose of a non-depolarizing muscle relaxant, waiting for the onset of symptoms, and then giving the induction agent.

Table 1. Conditions That Increase the Risk of Severe Hyperkalemia With Succinylcholine

Condition	Timing (When Risk Starts)
Thermal injury (burns) Crush injury	Risk increases after 24 hours Risk remains up to 1-2 years after initial burn
Traumatic injury Massive trauma Closed head injury	Risk increases after 1 week
Severe intra-abdominal infection	Risk increases after 1 week
Neurologic disease Spinal cord trauma Hemiparesis Multiple sclerosis Stroke Guillain-Barre disease Encephalitis	Immediate risk if chronic denervating condition For acute conditions (eg, stroke), risk increases after 24 hours
Myopathy Duchenne muscular dystrophy Becker muscular dystrophy Mitochondrial myopathy	Immediate risk (eg, muscular myopathy)
Disuse atrophy/immobility	After several days (≥16 days increases risk)
Prolonged relaxant use	After several days of mechanical ventilation