title: Hyperparathyroidism, hypercalcemia and difficult laryngoscopy: a retrospective review.
abstract: BACKGROUND
  The incidence of difficulty with intubation in the general population depends upon the definition used but results as high as 37% have been published. Endocrine disorders such as diabetes and hyperthyroidism have been linked to an increased incidence of difficult intubation via laryngoscopy. Hypercalcemia with resulting calcification has been demonstrated to result in neck pain, decreased cervical range of motion, and loss of skin and tendon compliance. We speculated that patients with hyperparathyroidism and resulting hypercalcemia would have an increased incidence of intubation difficulty via laryngoscopy.
  
  
  METHODS
  We studied 382 patients presenting for parathyroidectomy in whom direct laryngoscopy was initially attempted compared to 262 patients presenting for abdominal surgery in whom laryngoscopy was initially attempted via retrospective chart review. Difficult laryngoscopy was defined as 3 or greater attempts at direct laryngoscopy or 2 attempts and the use of airway adjunct (Eschmann stylet), flexible fiberoptics, or an indirect laryngoscope (Pentax AWS or Airtraq). Awkward intubation was defined as requiring > 1 attempt at laryngoscopy, intubation requiring a change in laryngoscope blade, the use of an airway adjunct (Eschmann stylet), or a Cormack and Lehane's view on initial laryngoscopy > 2. Hypercalcemia was defined as serum [Ca2+] > 10.2 mg/ dl. Propensity score matching was done to create 88 matched patient sets. McNemar's test was used to evaluate intubation difficulties in patients presenting for parathyroidectomy. The relationship between difficult laryngoscopy and hypercalcemia in parathyroidectomy patients was assessed by simple logistic regression (unadjusted) and multiple logistic regression.
  
  
  RESULTS
  There is no difference in the rate of difficult or awkward laryngoscopy or the rate at which laryngoscopy was abandoned in favor of another means of intubation between parathryoidectomy and abdominal surgery patients. Hypercalcemia also does not impact laryngoscopy difficulty.
  
  
  CONCLUSIONS
  To our knowledge, this is the first manuscript evaluating the impact of parathryoidectomy surgery and hypercalcemia on ease of intubation via laryngoscopy. Despite the fact that patients presenting for parathyroidecomy have many potential etiologies of increased difficulty with laryngoscopy, they do not appear to be at increased risk of laryngoscopy problems. The same is true of those patients presenting with hypercalcemia. Source(s) of support: There was no source of funding for this study. Presentation at a meeting: Society for Airway Management Annual Meeting 2009 Las Vegas NV and American Society of Anesthesiologists Annual Meeting 2010 San Diego, CA. Conflicting Interest (If present, give more details): With regard to conflict of interest, Dr. Arndt is a paid consultant for Cook Medical and receives royalties based on the sale of products that he invented.
authors.affiliation: Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA. kmschro1@wisc.edu
authors.forename: Kristopher Michael
authors.initials: KM
authors.lastname: Schroeder
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Joffe
authors.forename: Adin-Cristian
authors.initials: AC
authors.lastname: Andrei
authors.forename: Kisha D
authors.initials: KD
authors.lastname: Thomas
authors.forename: George A
authors.initials: GA
authors.lastname: Arndt
mesh_terms: D000328:Adult; D000368:Aged; D006801:Humans; D006934:Hypercalcemia / Q000150:complications*; D006961:Hyperparathyroidism / Q000150:complications / Q000601:surgery*; D007442:Intubation, Intratracheal / Q000379:methods*; D017214:Laryngeal Masks; D007828:Laryngoscopy / Q000379:methods*; D016015:Logistic Models; D008875:Middle Aged; D016105:Parathyroidectomy / Q000379:methods*; D012189:Retrospective Studies