This study complements existing literature by reporting important findings regarding patient characteristics that are associated with in-hospital mortality following tracheotomy in children. In both bivariate and partition regression analyses, prematurity, congenital heart disease and age less than 1 year were associated with higher mortality. The presence of an upper airway anomaly was consistently associated with lower mortality. Up to 30-fold differences in mortality were observed among children with different combinations of these characteristics.
We are grateful for the large tracheotomy sample size available from the KID that permitted the analysis of mortality by different patient demographic and clinical characteristics. Even when aggregating patient data across multiple decades, most single institutional studies achieve a sample size of a few hundred patients at best, and these studies do not report mortality differences by underlying diagnosis.10,17,19
Previous studies that utilised large administrative hospital databases reported mortality during the hospitalisation when tracheotomy was performed for all children, children with NI and infants age less than 1 year of age that are congruent with the present study.1–3
The present study adds to this previous work by presenting mortality based on combinations of different patient characteristics within these three cohorts. Combinations of co-morbid illnesses are often contemplated when evaluating prognosis and mortality in both paediatric and adult critically ill patients.30–32
Over or underestimating mortality following tracheotomy may occur if multiple conditions are not considered. For instance, in 2006 the overall mortality for children with NI undergoing tracheotomy was 7.6%. However, mortality for these children ranged from 1.4% to 40.0%, depending on which additional characteristics were present or absent.
One interesting finding from this study was that in-hospital mortality following tracheotomy remained statistically constant over time, despite an increasing prevalence of patient characteristics associated with higher mortality (). Additional changes in demographics may have counterbalanced the impact of these characteristics and stabilised mortality over time. For example, there was a non-significant trend (p=0.1) of decreasing mortality in children undergoing tracheotomy with chronic lung disease and the ‘other’ category from 1997 to 2006 (). Similar to previous studies, a trend towards younger age at tracheotomy was observed.33,34
This trend may have kept mortality constant over time owing to the simultaneous increase in prevalence of infants age less than 1 year and children ages 1–4 years undergoing tracheotomy. These age cohorts were associated with the highest and lowest mortality, respectively, of all age groups following tracheotomy.
Lower mortality in children with an upper airway anomaly following tracheotomy is reported previously.3
It is possible that the risks associated with tracheotomy in children with an upper airway anomaly may be outweighed by lowering the mortality risk conferred by alleviating the upper airway obstruction.3
Under certain circumstances, the anomaly itself may be alleviated by medical or surgical intervention following tracheotomy, which may further decrease its mortality risk. The mortality risk may be even lower when there are no additional co-morbidities likely to compromise the child’s health. For instance, we observed the lowest mortality in children following tracheotomy with upper airway anomaly when both prematurity and congenital heart disease were absent ().
Tracheotomy in the absence of an upper airway anomaly may indicate situations where the underlying aetiology of respiratory insufficiency may remain following tracheotomy and contribute substantially to the risk of mortality. This situation may be especially relevant in children with congenital heart disease. The absence of an upper airway anomaly was the characteristic most significantly associated with higher mortality in children with congenital heart disease (). Upper airway anomaly and congenital heart disease were consistently found to be arranged side-by-side within each mortality partition model, suggesting that the pairing of these characteristics is important to consider when projecting mortality following tracheotomy. It is possible that congenital heart disease and an upper airway anomaly together are manifestations of an underlying genetic disorder or other congenital syndrome.35
Increased prevalence of children undergoing tracheotomy with congenital heart disease, and higher mortality in these children has not been described previously. Children with congenital heart disease may be predisposed to upper airway abnormalities from frequent intubation, prolonged ventilation support and recurrent laryngeal nerve injury.36
Improved survival of children with congenital heart disease may have permitted the development of longer-term restrictive or obstructive lower respiratory tract insufficiency requiring tracheotomy in some children.37,38
This may help explain the observed increase in tracheotomy performed in children with both congenital heart disease and chronic lung disease. These factors along with the intrinsic risk of morbidity associated with the congenital heart disease itself, may help explain the high mortality following tracheotomy experienced by these children.39
The association of prematurity with higher in-hospital mortality following tracheotomy has not been reported in previous studies. There are several potential reasons to explain this finding. Premature infants with very low birth weight or complex underlying conditions are at higher risk for mortality even without tracheotomy.40,41
Some infants may encounter acute life-threatening respiratory events and require tracheotomy to avoid immediate death.40,42,43
Care may be subsequently withdrawn or redirected following tracheotomy in these infants due to poor prognosis, failure of improved health status or other reasons.44–47
Care withdrawal may be occurring more frequently in premature infants following tracheotomy than in children with other chronic conditions when facing similar situations.48
We could not determine the true reason for mortality from the administrative data available in KID. Important clinical data such as the number of failed extubations, total number of ventilator days, degree of long-term oxygenation or ventilation support and haemodynamic instability were unavailable.31,49
We were unable to follow patients over time after hospital discharge. Therefore, the in-hospital mortality we observed may underestimate longer-term death in these children.
We could not determine the primary indication for tracheotomy or the true reason for death from the administrative data. The clinical characteristics evaluated do not include all of the underlying clinical conditions that children with tracheotomy may possess. The characteristics were ascertained from administrative diagnosis codes which may be associated with coding error and bias.50
For instance, premature children may be more likely to receive a prematurity code during a newborn admission compared with an admission later in life.
The trends observed in the co-morbid conditions may have been influenced by ICD-9-CM coding changes.51
We evaluated each individual ICD-9-CM code in the present study for changes in description, coding number, new additions or discontinuation during the study period.51
We accounted for these changes to minimise their impact on the results. For example, ICD-9-CM code 438.50 (other paralytic syndrome including ‘locked-in state’ or ‘quadriplegia’) was used as a NI code. In 1998, the number of this code changed from 438.50 to 438.53. Therefore, for the 1997 analysis, we used 438.50 to capture this code. For the 2000, 2003 and 2006 analyses, we used 438.53.
Heterogeneity of severity of illness and underlying disease pathology exists within the clinical characteristics evaluated in the present study which likely influences mortality. For example, severe forms of congenital heart disease may be associated with higher mortality following tracheotomy than milder forms.39
The clinical course may be different in a child requiring tracheotomy with cystic fibrosis compared with bronchopulmonary dysplasia. Further investigation within each clinical characteristic is required to better understand these associations.
Implications and conclusions
Tracheotomy may be a critical intervention to maintain immediate survival in a child with a chronic medical condition who is experiencing life-threatening respiratory compromise. However, many of these children will not survive the hospitalisation, especially those children with multiple co-morbid conditions that are associated with an increased mortality risk.
The mortality information presented in this study complements a growing body of literature describing the health outcomes that children and their families experience following tracheotomy. Some studies report favourable outcomes,17,19,52–54
whereas others report that children experience repeated, lengthy hospitalisations following tracheotomy,3,18
and their parents experience an immense care giving burden that is associated with impaired quality of life, marital discord and loss of employment.55–57
The outpatient and community healthcare providers of a child under consideration for tracheotomy may be in an ideal position to collaborate with inpatient clinicians and augment patient and family counselling of risks and benefits. When a longitudinal, established relationship with the child exists, outpatient primary and specialty care clinicians, in particular, may offer an important comprehensive assessment of the child’s underlying chronic health conditions, long-term health trajectory and family’s projected ability to cope with the child having a tracheotomy. We hope the findings from the present study encourage paediatric providers of all types to better understand, inform and advise families regarding the factors that influence child health outcomes following tracheotomy.