Pressure damage to respiratory mucosa from overinflation of bronchial cuffs has been implicated as a cause of bronchial rupture, a rare but devastating complication of double-lumen endobronchial tubes (DLTs). We compared the pressurelvolurne characteristics of the bronchial cufs of three different polyvinylchloride (PVC) DLTs and a equivalent sized red-rubber Robertshaw DLT. At the volume needed to seal effectively our bronchial model, two of the three PVC tube cuffs tested generated significantly less pressure than did that of the cuffs of the third PVC and the red-rubber Robertshaw tubes.
The global obesity epidemic is growing in severity, affecting people of every age and costing healthcare providers millions of dollars every year. Every day, anesthesiologists are presented with obese and morbidly obese patients undergoing every type of surgical procedure; the management of these patients differs significantly from that of normal weight patients undergoing the same procedure. Anesthetic Management of the Obese Surgical Patient discusses these specific management issues within each surgical specialty area. Initial chapters describe pre-operative assessment and pharmacology; these are followed by detailed chapters on the anesthetic management of a wide variety of surgical procedures, from joint replacement to open heart surgery. Essential reading for anesthesiologists and nurse anesthetists worldwide, Anesthetic Management of the Obese Surgical Patient and its companion work by the same authors, Morbid Obesity: Peri-operative Management, enable both trainees and practised professionals to manage this complex patient group effectively.
Obesity is a risk factor for increased difficulty in most modalities of airway management. It decreases ease and effectiveness of face mask ventilation, supraglottic airway device use and front of neck airway techniques and probably makes laryngoscopy more difficult. When difficulty occurs, airway rescue techniques are more likely to fail in the obese patient. Obesity also increases the risk of aspiration and difficulty in lung ventilation, both of which may necessitate changes in anaesthetic technique. Most importantly, obesity reduces the time available for airway management before hypoxia supervenes. To worsen matters, obesity reduces the efficacy of pre-oxygenation and safe apnoea time is less prolonged with apnoeic oxygenation techniques than in the non-obese population. To compound these factors obesity is associated with obesity-specific (e.g. obstructive sleep apnoea, obesity hypoventilation syndrome) and non-specific co-morbidities (diabetes, asthma, hypertension). With increasing numbers of obese patients and increasing degrees of obesity in the surgical population it is essential that all anaesthetists are familiar with the potential complications of airway management in the obese and the techniques that may mitigate or manage risk.
To the Editor: Amar et al.1 prospectively studied the impact of left double-lumen tube (DLT) size for patients undergoing thoracic surgery. The occurrence of hypoxemia during one-lung ventilation (defined as Spo2 <88%), failure to isolate the operative lung (attributed to DLT malposition), and/or the need for intraoperative DLT repositioning were the same whether a small or larger DLT was used. Based on these findings, the authors’ question a current practice of selecting the largest DLT that will safely fit that patient's bronchus. Half of the investigators in this study routinely select a small DLT for all patients, however many of the small DLTs may have actually been indicated had the patient's tracheal diameter been measured. Additionally, the authors cannot evaluate how a truly undersized DLT would have performed because patients with “undersized” DLTs and those with anatomically sized DLTs were analyzed together in groups according to height. What can be concluded, however, is that the composite end points occurred with equal frequency for all height groups (approximately 15%–20%). This is not surprising, considering that previous studies have demonstrated a poor correlation of left mainstem bronchial diameter with patient height and gender. Selection based only on height and gender results in an inappropriate sized DLT (either too large or too small) in the majority of patients.2 Even with a similar incidence of measured endpoints between groups, the claim that tube size is unimportant is not resolved by the results of this study. Airway injury from a DLT is devastating, but fortunately very rare. Almost all reports of airway rupture have been associated with small DLTs. A review of this complication found no published instances of tracheo-bronchial injury associated with larger (size 41 Fr) DLTs.3 Although the higher incidence of major complications with smaller DLTs may be due to their greater popularity, it could also relate to the need for relative cuff hyperinflation necessary with an undersized tube, or even to the natural angulation of the bronchial lumen.4 One of the end points of the present study, failure to isolate the lung, could have been due to tube size and not as attributed, to malposition. Even with an ideally positioned tube, which presumably was the norm because all DLTs were positioned with fiberoptic bronchoscopy, 4 mL of air in the bronchial cuff of an undersized DLT in a large bronchus may be insufficient to adequately seal the bronchus. This could result in “failure to isolate” and collapse the operated lung. It would have been useful had the authors compared the difference in bronchial cuff volume and pressure between undersized and anatomically sized DLTs. Finally, one very important potential disadvantage of an undersized DLT, not considered in this study, is the issue of airflow resistance. Because of their reduced internal luminal diameters and higher airflowresistance, small DLTs (35 and 37 Fr) are associated with significantly more auto-positive end-expiratory pressure (PEEP) than larger DLTs.5,6 Many patients undergoing thoracic procedures have obstructive lung disease and selection of a small DLT in these individuals can result in dangerously high levels of auto-PEEP and dynamic pulmonary hyperinflation.7 We continue to believe that anesthesiologists should always examine their patients’ preoperative chest radiographs or chest computed tomography scans before placing DLTs. Not only will this provide a measure of airway size, it will also alert the physician to distortion or obstruction of the airway that could present a problem with placement of a DLT of any size. Jens Lohser, MD, FRCPC Department of Anesthesia University of British Columbia Vancouver, British Columbia, Canada [email protected] Jay B. Brodsky, MD Department of Anesthesia Stanford University School of Medicine Stanford, California
T HE AUTHORS recently anesthetized a patient who experienced dyspnea caused by tracheal compression 50 years after surgical creation of an oleothorax. A Clagett procedure was performed to facilitate continuous drainage from the cavity. Because of the unique etiology of her problem, the management differed from that usually recommended for a variable intrathoracic airway obstruction, and the case is presented.
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