Anesth Analg 2004;99:956
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000131702.14060.DD
LETTERS TO THE EDITOR
Standard Clinical Tests for Predicting Difficult Intubation Are Not Useful Among Morbidly Obese Patients
Tomasz Gaszynski, MD PhD
Department of Anesthesiology and Intensive Therapy, Medical University of Lodz/Barlicki University Hospital, Kopcinskiego, Poland
To the Editor:
Juvin et al. (1,2) described difficulties with endotracheal intubation (ET) and peripheral line placement in obese patients. Preoperative clinical test predicting difficult intubation (DI) are performed as a standard. In recently published work in The Polish Medical Journal (3), we evaluated 87 morbidly obese (MO) BMI 43.4 ± 6.7 kg/m2 (range, 35–68) to identify factors complicating direct laryngoscopy and ET. Preoperative measurements (neck circumference, mobility of the articulations of the cervical spine, the temporomandibular joints mobility, and width of mouth opening, sternomental distance, presence of edema of throat, crowding of the pharynx by the tongue, proceeding teeth) and Mallampati score were recorded. The direct laryngoscopy (Cormack scale) and the intubation conditions (Krieg scale) were estimated.
The results of our work were quite similar to Juvin et al.’s. Neither absolute obesity nor BMI were associated with intubation difficulties: DI predicting factors were present in 19 (21.8%) patients; Cormack Class 3 and 4, 17 (19.5%) patients. Actual DI occurred in 4 (4.6%) patients, BMI 41.9–46.2 kg/m2; in 2 of 4 patients, DI was expected; 2 others had no factors for DI. The Mallampati score in all 4 patients was 1 and 2. The only common predicting factor was large neck circumference in 2 patients.
To define DI, we used criteria of the ASA: ET attempts lasting more than 10 min, or more than two attempts (4). The number of difficult laryngoscopies was 5 (5.7%) defined by Krieg scale score >8 points. All MO patients with BMI > 50 kg/m2 were intubated by first attempt. DI occurred in patients with not high BMI—as in Juvin et al.’s work.
We concluded that standard clinical tests for evaluation of intubation conditions and predicting DI are not useful among MO; the number of DI in MO did not differ significantly from general population.
The main reason for differences in DI between our work and Juvin et al. (4.6% and 15.5%, respectively) is probably "the lack of consensus on the definition of the term "difficult intubation"; Juvin et al. used Intubation Difficult Scale (1). Studies were conducted on a comparable number of patients (87 and 138, respectively). Every ET was performed by an experienced anesthesiologist working in busy bariatric center, so the lack of experience is not a reason. In the case of ET performed by a resident or anesthesiologist not experienced with MO, the ratio of DI may increase dramatically, especially in emergency settings. Therefore, we recommend the use of alternative airway management methods for temporary ventilation in MO (5,6).
Only in one patient did we record difficulties with placement peripheral line (IV catheter) in upper limb. We agree that "recommendation that central venous line should be inserted in every MO patient is not valid" (2). It should depend on type of surgery and the patient’s condition. Exposing patients to an additional risk of complications connected with placement of central venous access is neither necessary nor ethical.
References
- Juvin P, Lavaut E, Dupont H, et al. Difficult tracheal intubation is more common in obese than in lean patients. Anesth Analg 2003; 97: 595–600.[Abstract/Free Full Text]
- Juvin P, Blarel A, Bruno F. Is peripheral line placement more difficult in obese than in lean patients? Anesth Analg 2003; 96: 1218.[Abstract/Free Full Text]
- Gaszynski T, Strzelczyk J, Gaszynski W. Evaluation of clinical test for predicting difficult intubation among obese patients [in Polish]. Twoj Magazyn Medyczny-Chirurgia 2003; 3: 50–4.
- Janssens M, Hartstein G. Management of difficult intubation. Eur J Anaesthesiol 2001; 18: 3–12.[Web of Science][Medline]
- Gaszynski T, Strzelczyk J, Gaszynski W. The laryngeal tube for airway management in morbidly obese. Eur J Anaesthesiol 2003; 20 (Suppl 30): 37.[Web of Science][Medline]
- Keller C, Brimacombe J, Kleinsasser A, et al. The laryngeal mask airway ProSealTM as a temporary ventilatory device in grossly and morbidly obese patients before laryngoscope-guided tracheal intubation. Anesth Analg 2002; 94: 737–40.[Abstract/Free Full Text]
Response
Philippe Juvin, MD PhD
Department of Anesthesia and Intensive Care, Beaujon Hospital, Clichy, France
In Response:
The incidence of difficult intubation in morbidly obese (MO) patients was more important in our work (1) than in Dr. Gaszynski’s work. The main reason is that we have studied difficult intubation using the Intubation Difficult Scale (IDS) while Dr Gaszynski has used other parameters (2). The IDS score uses several parameters known to be associated with difficult intubation. In our study, for example, intubation was more difficult in the MO patients whereas the incidence of difficult laryngoscopy was similar in MO and lean patients. We think that the IDS is more objective and reliable than the definition of difficult intubation used by the American Society of Anesthesiologists. For example, the duration of the intubation procedure is, in practice, difficult to measure. In addition, we have included more patients than Dr. Gaszynski did. We have calculated that a sample size of at least 115 patients per group (obese and lean) was necessary to demonstrate a difference between the two groups, with  = 0.05 and ß = 0.20 (1). In other words, what was the ß risk used by Dr. Gaszynski ? Under these conditions, is the conclusion of Dr. Gaszynski still valid ?
Dr. Gaszynski said that the "only common predicting factors was large neck circumference." We did not measure neck circumference. However, only two patients had a large neck circumference in the Dr. Gaszynski’s study. This small sample size is an important methodological limitation regarding risk factors. In our study (1), a multivariable analysis restricted to the MO group was conducted. In keeping with the result reported by Brodsky et al. (3), we have found that a high Mallampati score was a risk factor for difficult intubation in MO patients. However, the predictive value of the Mallampati score was poor, calling into question the validity of this statistical predictive factor in clinical practice. For this reason, we agree with Dr. Gaszynski regarding Mallampati score in MO patients.
Concerning the question of difficulties of placement with peripheral line, Dr. Gaszynski stated that peripheral line was difficult in only one patient in his study. However, he did not report which method he used to measure difficulties of insertion. In our own study, we have used a single objective method and we confirm that peripheral line placement is more difficult in obese than in lean patient. Nevertheless, we agree with him that "recommendation that central venous line should be inserted in every MO patient" is not valid (4).
References
- Juvin P, Lavaut E, Dupont H, et al. Difficult tracheal intubation is more common in obese than in lean patients. Anesth Analg 2003; 95: 595–600.
- Adnet F, Borron SW, Racine SX, et al. The intubation difficulty scale (IDS): proposal and evaluation of a new score characterizing the complexity of endotracheal intubation. Anesthesiology 1997; 87: 1290–7.[Web of Science][Medline]
- Brodsky JB, Lemmens HJ, Brock-Utne JG, et al. Morbid obesity and tracheal intubation. Anesth Analg 2002; 94: 732–6.[Abstract/Free Full Text]
- Juvin P, Blarel A, Bruno F, Desmonts JM. Is peripheral line placement more difficult in obese than in lean patients? Anesth Analg. 2003; 96: 1218.
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