Test Your Airway IQ - EMERGENCY QUESTIONS

1. You are about to paralyze a 240 kg man for emergency RSI. Which dose of succinylcholine is the best choice?

1. 120 mg
2. 180 mg
3. 240 mg
4. 360 mg

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2. You are preparing to intubate a 4 year old with status asthmaticus. Which of the following induction agents would NOT be an appropriate choice?

1. Ketamine
2. Etomidate
3. Versed
4. Thiopental

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3. A 36-week pregnant woman requires emergency RSI for severe pneumonia. Which of the following is the best approach, considering her advanced pregnancy? 

1. Plan to use a smaller than usual endotracheal tube
2. Increase drug doses by 40% to account for her increased intravascular volume
3. Avoid succinylcholine to minimize the likelihood that the baby will be paralyzed
4. Anticipate delayed oxyhemoglobin desaturation compared to the nonpregnant patient

See the answer

Question 1

1. You are about to paralyze a 240 kg man for emergency RSI. Which dose of succinylcholine is the best choice?

1. 120 mg
2. 180 mg
3. 240 mg
4. 360 mg

Answer: D. 360 mg (1.5 mg/kg TBW)
This one is straight out of the book! Succinylcholine is dosed by total body weight, so the dose here is 1.5 mg/kg of TBW or 360 mg!! The manual says: “In the morbidly obese patient, increased extracellular volume is often associated with increased levels of plasma pseudocholinesterase, both factors playing a role in the duration of action of succinlycholine. Lemmen and Brodsky found that obese patients receiving IBW and LBW doses of succinylcholine had significantly less blockade, with 33% and 27% having poor intubating conditions, respectively. All patients receiving total body weight (TBW) dosing displayed adequate intubating conditions, although recovery time was prolonged. Of note, even the IBW had a recovery time of 5 minutes, which is still inadequate for resuming spontaneous ventilation before hypoxemia develops in the obese patient (typically 2-3 minutes). Despite the relatively long recovery time with succinylcholine, even with IBW dosing, it is wise to achieve the best intubating conditions possible, hence the recommendation for TBW dosing.” (1)

— RM Walls, MD

1.  Wiser SH and Zane RD: Neuromuscular Blocking Agents.  In:  Walls RM and Murphy MF, Manual of Emergency Airway Management, 3rd Edition.  Philadelphia, Lippincott, Williams and Wilkins, 2008 ; p 408.

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Question 2

2. You are preparing to intubate a 4 year old with status asthmaticus.  Which of the following induction agents would NOT be an appropriate choice?

1. Ketamine
2. Etomidate
3. Versed
4. Thiopental

Answer: D. Thiopental. 
All other agents listed could be used for induction in severe asthma, with ketamine providing the best profile of safety and efficacy.  Thiopental is a potent releaser of histamine and may make bronchospasm worse.  It is also a potent vasodilator and may cause hypotension in a sick, volume depleted child. (1)

— Nathan Mick, MD

1.  Caro DA and Tyler K:  Sedative Induction Agents.  In Walls RM and Murphy MF, Manual of Emergency Airway Management, 3rd Edition.  Philadelphia, Lippincott, Williams and Wilkins, 2008 ; p 408.

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Question 3

3. A 36-week pregnant woman requires emergency RSI for severe pneumonia. Which of the following is the best approach, considering her advanced pregnancy?

1. Plan to use a smaller than usual endotracheal tube
2. Increase drug doses by 40% to account for her increased intravascular volume
3. Avoid succinylcholine to minimize the likelihood that the baby will be paralyzed
4. Anticipate delayed oxyhemoglobin desaturation compared to the nonpregnant patient

Answer: A. Plan to use a smaller than usual endotracheal tube.
This is a tough one, but the answer lies in examining all 4 of the offered choices.  Let’s begin with D, which is false, as described in the following excerpt from the Manual of Emergency Airway Management, 3rd edition:  “Preoxygenate using at least eight vital capacity breaths or 3 minutes of breathing 100% oxygen; as FRC is reduced, oxygen consumption is increased and apnea leads to desaturation more rapidly.”  (1)   So, desaturation is actually accelerated, not delayed.

C is not correct, because the succinylcholine will not cross the placental barrier.  Although the baby may “share” the induction agent, or opioids, it is protected from neuromuscular blocking agents.  

When considering B, it is true that the plasma volume increases by about 33% in pregnancy, but induction agents and succinylcholine are both dosed as for the non-pregnant patient.  This is because of three considerations.  Firstly, increased doses of induction agent have a greater potential for adverse effects on the baby after birth.  Secondly, all of the induction agents reduce blood flow to the uterus and placenta, so it is desirable to avoid excessive doses.  Thirdly, succinylcholine is dosed by total body weight, without adjustment for body habitus.  This is discussed in the manual on pp 404 and 405. 

So, that leaves A.   The relevant chapter (chapter 32) in the manual says:  “Pregnancy also can affect laryngoscopy and bag-mask ventilation (BMV).  Weight gain and increased breast size may make direct laryngoscopy difficult, while mucosal venous engorgement of the nasal passages and pharynx cause airway tissues to become friable and prone to bleeding.  This mucosal edema can also lead to distortion of the airway structures, leading to difficulty both in identifying structures and in passing the endotracheal tube through the larynx and trachea.  This upper airway distortion can be worsened by pre-eclampsia, active labor with pushing, and the infusion of large volumes of crystalloid fluids.  Vascular engorgement also leads to a decrease in luminal size in the trachea requiring a smaller than expected endotracheal tube (6.5 – 7.0 on average).  (2)

In any case, of these 4, A it is the clear winner, although I understand why you were tempted by B.    

— RM Walls, MD  

1. Muir HA and Zane RD: The Pregnant Patient. In Walls RM and Murphy MF, Manual of Emergency Airway Management, 3rd Edition. Philadelphia, Lippincott, Williams and Wilkins, 2008 ; p 381.

2. Muir HA and Zane RD: The Pregnant Patient. In Walls RM and Murphy MF, Manual of Emergency Airway Management, 3rd Edition. Philadelphia, Lippincott, Williams and Wilkins, 2008 ; p 380.

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