Sedation and Neuromuscular Blockade
A 25-ycar-old woman with a history of acute severe asthma is admitted to the ED. She is confused, lethargic, and experiencing extreme respiratory distress with wheezing. Her pulse oximetry reading is 86%, heart rate 170 (sinus tachycardia}, blood pressure 175/97 mm Hg, and respiratory rate 24/min and labored. The team quickly intubates her after induction with IV boluses of fentanyl, midazolam, and succinylcholine. She is ventilated on the assist-control mode: oxygen-100%, rate of 15 breaths/min, tidal volume of 500 mL, and no PEEP. A continuous albuterol and ipratropium aerosol is delivered via the ventilator. Steroids are initiated and a normal saline (NS) infusion is started at 200/h. She is transferred to the MICU for continued management.
In the MICU, the patient begins to awaken and is very dyssynchronous with the ventilator despite additional IV boluses of midazolam and fentanyl Her BP decreases to 50/30. The NS infusion is increased to wide-open and a single bolus dose of pancuronium is given. The nurse then starts continuous infusions of fentanyl and midazolam and when the patient begins to initiate breaths, a vecuronium infusion is started. The nurse monitors the airway pressure waveform to assure patient spontaneous breathing ceases and tests the train of four with the peripheral nerve stimulator. After a liter of fiuid is infused, the patient's BP is 110/60. The NS infusion is decreased to 175/h.
Once the NMB is effective, the respiratory therapist performs an end-expiratory hold maneuver and detects 15 cm/ H 20 auto-PEEP. The team decides to decrease the ventilator rate, increase the expiratory time, and decrease the tidal volume. They recognize that this will result in hypcrcarbia and a drop in pH but will allow it {called permissive hypercarbia} with careful monitoring in order to decrease her lung hyperinflation. The team's plan includes the continuation ofNMB as well as fentanyl and midazolam. Bronchodilatoill, steroids, and fluids are also continued.
Two days later, auto-PEEP is no longer detected and the lungs arc clear with minimal wheezing. The NMB is discontinued, the patient awakened (by titrating the sedation and narcotics off) and the patient is successfully cxtubated.
Why did the patient's BP drop so precipitously following intubation and mechanical ftntilation?
(A) Sedatives and narcotics potentiatc the actions of each other and in some cases may result in hypotension.
(B) While experiencing severe shortness of breath, the patient is in a fight-or-flight mode and intrinsic stores of epinephrine arc released, constricting the peripheral vasculature and devating BP. Once relaxed, the vessels dilate resulting in a lower BP.
(C) Often asthmatics that arc in an acute severe asthmatic crisis arc dehydrated.
(D) Dynamic hyperinflation and/or auto-PEEP results in transmission of elevated intrathoracic pressure to the capillary bed (especially if the patient is dehydrated} causing decreased venous return and subsequent hypotension.
(E) All the above.
Why is the use ofNMB agents of concern, e1pecially in acute sevue asthma?
(A) The agents arc associated with myopathies and ncuropathies, especially when combined with steroids.
(B) NMB takes away the patient's inherent protective reflexes.
(C) There is no concern with their use as they make it much more easy to control ventilation and other aspects of care.
(D) Aonly
(E) AandB
(F) Band C
When con1idering the choice of sedatives for this patient, which of the following apply?
(A) Use a long acting sedative since she will require sedation for a long time.
(B) If she is paralyzed she will not feel any pain or remember anything, so analgesics and sedatives aren't necessary.
(C) Train of four is a helpful measurement when NMB is being used because it tests the depth of sedation.
(D) While NMB is maintained, sedatives are used for their amnesic properties in addition to concomitant analgesics for potential pain.