During the study period, 455 patients underwent tracheostomy during their stay in the ICU. Twenty-eight patients were excluded because of previous history of tracheostomy (n = 15), neck surgery (n = 9), and cervical irradiation (n = 4). Of the 427 tracheostomies, 89 were performed in morbidly obese patients. Table 2 displays the characteristics of the study population. The two cohorts differed in age, BMI, and burden of comorbidity but were similar in gender and severity of illness on admission to the ICU. The most frequent underlying diagnoses for the need of critical care for the study population included pneumonia (21%), obstructive lung diseases (asthma and chronic obstructive pulmonary disease) (14%), postoperative non-vascular surgery (14%), and trauma and burn (13%). Only hypercapnic respiratory failure was reported more frequently in the morbidly obese group than in the control group (p < 0.001). Similarly, prolonged mechanical ventilation was more likely to be listed as the indication for tracheostomy in the morbidly obese group and failure to wean was more likely to be listed as the indication for tracheostomy in the control group. Nine tracheostomies were performed on an emergent basis, and two of these were in the morbidly obese group. The duration of mechanical ventilation prior to tracheostomy as well as the number of endotracheal intubations were comparable between the two groups.
A total of 27 complications were recorded in 22 patients (25%) of the morbidly obese group compared to 65 complications in 49 patients (14%) of the control group (p = 0.03). Five morbidly obese patients had two complications, whereas 15 controls had two complications and one control had three. The severity and time period of complications for both study groups are detailed in Table 3.
Minor bleeding was the most frequently reported complication in both groups (11% versus 7%; p = 0.24). Ninety-four percent of the cases (31 out of 33 cases) occurred during the first seven days postoperatively. In all of these instances, bleeding was controlled with light packing. Cuff leak represented the second most common complication in the study population (3% in the morbidly obese and 7% in the control group; p = 0.26), but unlike minor bleeding, these events were noted primarily after seven days of tracheostomy placement. Whereas cuff malfunctioning was responsible for early failure, loss of tracheal wall rigidity secondary to prolonged mechanical ventilation was responsible for the late complication in both cohorts.
Morbidly obese patients were particularly at higher risk for serious life-threatening complications. Overall, nine serious events were responsible for two deaths compared to seven cases and two deaths in the control group (p = 0.001 for serious events). Tube obstruction was the culprit in four of the nine morbidly obese cases. An early case was attributed to a blood clot after the patient had evidence of minor bleeding. The patient developed severe hypoxemia but the event was detected early while the patient was still in the ICU. In contrast, the other three cases occurred outside the critical care unit between 7 and 18 days after liberation from mechanical ventilation. Despite delivery of high humidity, two patients were found to have a mucous plug that led to severe hypoxemia and severe bradycardia. Anoxic encephalopathy ensued in both patients; in one case, the family requested termination of life support, whereas the other patient required transfer to a long-term care facility. Of interest, all three cases had non-fenestrated cuffed synthetic tubes in place. In the control group, one patient with reduced consciousness secondary to head trauma sustained a respiratory arrest after a mucous plug and did not survive resuscitation.
Accidental decannulation followed by extratracheal tube placement (false lumen) was the next most serious complication reported in the critically ill morbidly obese patients. Whereas none of the control group was identified with this complication, three morbidly obese patients had serious consequences from attempting to reinstate the tracheostomy tube. One complication occurred five days postoperatively after the patient removed the tube while on mechanical ventilation. The patient developed massive subcutaneous emphysema that resulted in bilateral tension pneumothorax and cardiorespiratory arrest. The other two complications developed 11 and 28 days after surgery when attempting to replace or downsize the tracheostomy tube. In both instances, orotracheal intubation was performed after both patients went into respiratory distress. A revision of the tracheostomy was performed subsequently without further complications.
The incidence of major bleeding was not significantly different between the two groups. One morbidly obese and four control patients had a decrease of hematocrit of more than 2 g/dl in the first 48 hours postoperatively, which was attributed to extensive oozing around the site of the wound. Bedside hemostasis was achieved by local packing and application of thrombin. Two control patients who had significant bleeding at 16 and 38 days after surgery were suspected of developing a tracheoinnominate artery fistula. One patient had a massive aspiration and could not be resuscitated. The other patient was transferred to the operating room, where an immediate exploration was performed and ligation of the bleeding vessel was conducted.
The rate and timing of stoma infection were also comparable between the two groups. Thirteen patients had local wound infection that was reported between days 2 and 10 of mechanical ventilation. Cultures of the wound showed predominance of gram-negative bacilli, notably Serratia marcescens (n = 1), Escherichia coli (n = 5), and Pseudomonas aeruginosa (n = 6). Apart from local antibiotic application, none of these patients required systemic antimicrobial therapy to treat the infection. Only one morbidly obese patient was found to have a paratracheal abscess after persistent fever that was unresponsive to systemic antimicrobial therapy. A computer tomography was diagnostic of the abscess, and the patient required prompt drainage followed by four weeks of therapy targeted toward gram-negative and anaerobic pathogens. None of our study population had tracheoesophageal fistula or injury to a nerve, artery, or vein during the postoperative period. Finally, no incidence of tracheal stenosis was observed during the length of hospitalization in either group.
Three factors (age, BMI, and Charlson index) found to be significant in univariate analysis were entered into multivariate analysis. Only BMI (odds ratio 4.4, 95% confidence interval 2.1 to 11.7) was independently associated with increased risk of tracheostomy-related complications.