To the Editor:

We read with interest the case scenario regarding acute postoperative negative-pressure pulmonary edema (NPPE).1The authors elegantly discussed the diagnosis, differential diagnosis, epidemiological features, pathogenesis, and clinical management of NPPE. We are concerned that anesthetic management may have inadvertently contributed to the cause of this complication. The patient described was given opioid doses equivalent to 27.5 mg iv morphine (0.25 mg fentanyl = 25 mg + 0.5 mg hydromorphone = 2.5 mg)2and a nondepolarizing muscle relaxant. The fact that the patient (with a normal airway) developed laryngospasm after extubation suggests that the patient was not ready for extubation. In addition, it is possible that reduced pharyngeal muscle tone due to residual neuromuscular blockade resulted in upper airway obstruction.3,4A patient with a “train-of-four” ratio of 0.9 or greater may still develop postoperative hypoxemia5and may require the administration of reversal drugs.

The initial difficulty in mask ventilation after extubation implies that the inspiratory stridor had progressed to a ball–valve obstruction.6Applying positive airway pressure under these circumstances may actually worsen ball–valve closure.6Inflation of the pharynx distends the piriform fossae, pressing the aryepiglottic folds more firmly against each other and reinforcing the closure.6 

We suggest that the complication presented could have been prevented by delaying extubation.

*Advocate Illinois Masonic Medical Center, Chicago, Illinois. mrsalem@sbcglobal.net

References

1.
Krodel DJ, Bittner EA, Abdulnour R, Brown R, Eikermann M: Case scenario: Acute postoperative negative pressure pulmonary edema. Anesthesiology 2010; 113:200–7
2.
Jaffe JH, Martin WR: Opioid analgesics and antagonists, Goodman and Gilman's the Pharmacological Basis of Therapeutics, 8thedition. Edited by Gillman AG, Rall TW, Nies AS, Taylor P. New York, McGraw–Hill, 1990, pp 485–521Gillman AG, Rall TW, Nies AS, Taylor P
New York
,
McGraw–Hill
3.
Eikerman M, Vogt FM, Herbstreit F, Vahid-Dastgerdi M, Zenge MO, Ochterbeck C, de Greiff A, Peters J: The predisposition to inspiratory upper airway collapse during partial neuromuscular blockade. Am J Respir Crit Care Med 2007; 175:9–15
4.
Debaene B, Plaud B, Dilly MP, Donati F: Residual paralysis in the PACU after a single intubating dose of nondepolarizing muscle relaxant with an intermediate duration of action. Anesthesiology 2003; 98:1042–8
5.
Murphy GS, Szokol JW, Franklin M, Marymont JH, Avram MJ, Vender JS: Postanesthesia care unit recovery times and neuromuscular blocking drugs: A prospective study of orthopedic surgical patients randomized to receive pancuronium or rocuronium. Anesth Analg 2004; 98:193–200
6.
Salem MR, Ovassapian A: Difficult mask ventilation: What needs improvement [editorial]? Anesth Analg 2009; 109:1720–2