The ethical committee of the medical association of the State of Rhineland-Palatinate approved the study and the committee waived the need for specific written informed consent. The study was performed in a 21-bed anesthetist-lead adult surgical ICU of a tertiary-care university teaching hospital.
This prospective, comparative, before-after study evaluated the endotracheal intubations of critically ill patients over a 2-year period in the ICU. Participating physicians completed a standardized evaluation form immediately after performing an endotracheal intubation.
Predictors of potentially difficult tracheal intubation were recorded for each patient on the standardized evaluation form: short neck with large circumference, obesity, limited mouth opening (< 3 cm), limited neck movement, presence of a large tongue and a short thyromental distance.
The laryngoscopic view was evaluated using the Cormack & Lehane (C&L) classification scale [11] and the Percentage of Glottic Opening scale (POGO) [12]. The number of intubation attempts, intubation success, the indication for the intubation and possible complications were documented. The lowest oxygen saturation during intubation was measured using pulse oximetry. Age, gender, physical status, the Simplified Acute Physiology Score and the Sequential Organ Failure Assessment II score were collected for all patients in this study at admission into the ICU. The clinical experience of the laryngoscopist was also noted. Junior physician was defined with up to 3 years clinical experience, senior physician with more than 3 years of training, and specialists were board-certified anesthesiologists.
Over a 12-month evaluation period (January 2009 to January 2010), the standard procedures for tracheal intubation remained unchanged. Restrictions concerning the selection of airway management tools for endotracheal intubation did not exist (baseline). Direct laryngoscopy (ML) was performed using a size 3 or size 4 regular Macintosh blade. Alternative airway devices (for example, intubation endoscope, laryngeal mask airway, and cricothyrotomy set) were always available in an airway cart at the bedside. After three failed attempts at endotracheal intubation, alternative devices (for example, endoscopic intubation) were used according to the in-house difficult airway algorithm.
The presence of at least two healthcare professionals, with at least one senior physician, was standard for all intubations. If possible, pre-oxygenation for 3 minutes at a high constant flow or non-invasive positive-pressure ventilation was administered to the patients. The medication for the induction of anesthesia was sufentanil (0.3 to 1.0 μg/kg) in every patient, with either propofol (1.5 to 2.0 mg/kg), ketamine (1.5 to 3 mg/kg) or etomidate (0.2 to 0.3 mg/kg). Rocuronium (0.4 to 0.9 mg/kg) was always used for neuromuscular blockade. In cardiac arrest patients, intubations were performed without medication. A malleable stylet in a hockey-stick shape was always used for tube placement. If visualization of the glottis or the placement of the endotracheal tube was difficult, the manipulation of the larynx was performed according to the instructions of the laryngoscopist. The successful placement of the endotracheal tube was confirmed using capnography.
We then evaluated endotracheal intubations over a second 12-month period (February 2010 to February 2011) after implementing two C-MAC® video laryngoscopes (Karl Storz GmbH & Co. KG) in the ICU (intervention phase). Video laryngoscopy was performed using the Karl Storz Macintosh shaped blades for C-MAC® size 3 or size 4 (Figure 1). ICU physicians were given didactic instruction on the proper use of the C-MAC® along with training on manikins. The ICU staff were advised to perform endotracheal intubations using the C-MAC® instead of ML when appropriate. The procedures for intubation, the medication for anesthesia and the in-house difficult airway algorithm were identical to the first evaluation period. Documentation was identical to the previous study period of 2009 to 2010.
Patients who presented with predictors of potentially difficult tracheal intubations were identified and analyzed in a subgroup for first-attempt intubation success and visualization of the glottis.
After use, the C-MAC® blades and cable with the electronic module were manually cleaned and immersed in a cleaning solution (Teralin®; Schülke & Mayr, Norderstedt, Germany). Automated processing using an endoscope cleaning and disinfection unit was then used for disinfection (BHT 2000®; BHT Hygiene Technik, Gersthofen, Germany). The monitor unit was cleaned manually using disinfection cloths (Mikrobac®; Bode, Hamburg, Germany).
Data were analyzed using GraphPad Prism (version 5a for MAC; GraphPad Software, San Diego, CA, USA). Data are expressed as the mean ± standard deviation and the median (interquartile range) for non-Gaussian variables. The comparison of the two proportions was performed with the use of the chi-square test or Fischer's exact test when appropriate. The comparison of means was performed using Student's t test, and comparison of the medians was performed with the Mann-Whitney test. One-way analysis of variance with Dunn's post-hoc test was used for multiple comparisons. The differences were considered statistically significant if P < 0.05.