This study is the first to establish national trends for the incidence of PSIs over the last decade. The NIS is the largest public database of hospitalized patient discharges. PSIs have become a standard method for screening administrative data for adverse events in an inexpensive and universally replicable manner which may be employed as diagnostic exam to prioritize areas for quality improvement. Our study sought to determine whether there has been an improvement for PSI rates from 1998 to 2007. The major findings are the statistically significant increasing and decreasing trends in PSIs.
Joinpoint analysis was chosen as a method of analysis due to its ability to identify changing trends over time. Originally applied to detect changes in cancer incidence (Kim et al. 2000
), the joinpoint method has more recently been used to detect changes in cohort mortality (Jemal et al. 2005
). Our analysis is the first to apply this method to detect changes in trends for PSIs.
Seven PSIs showed statistically significant increasing trends (postoperative pulmonary embolism or deep vein thrombosis, postoperative physiological or metabolic derangement, postoperative sepsis, selected infections due to medical care, decubitus ulcer, accidental puncture or laceration, and postoperative respiratory failure). While these seven PSIs differ in etiology and incidence, they are all bound by three general influences: severity of illness, surveillance
, and surgery
. The acuity of the patient's illness at presentation, including the number of comorbid conditions present, likely contributes to the increased rates of many of these PSIs. Despite adjusting for patient age and comorbid conditions, comorbid status may influence these rates by indirect means. Given the increase in life expectancy and subsequent rise in chronic medical conditions, there has been a general increase in the severity of illness in patients (Fry et al. 2005
). For example, sicker patients with extensive past surgical history who may have been excluded for surgery in the past could now be receiving surgery, which may account for increasing PSI rates. This study underscores the possibility of increasing surgical acuity with the rising PSI of accidental puncture or laceration acting as a surrogate marker for re-operative surgery. In addition, patients with more comorbidities are frequently subjected to the effects of polypharmacy (Hajjar, Cafiero, and Hanlon 2007
), which may contribute to increased rates of PSI postoperative respiratory failure and PSI postoperative metabolic and physiologic derangements. In addition to polypharmacy, increased drug-resistance (Diekema, BootsMiller, and Vaughn 2004
) has become more prevalent in acute care hospitals and may contribute to the increasing rates of infections and thus of PSI selected infections due to medical care and PSI postoperative sepsis. The number of admissions in U.S. hospitals increased each year (National Center for Health Statistics 2007
) and, despite the adjustment for admission rates, the increased rate of admission could contribute to these increased PSI rates by other means such as increased patient/provider ratios. Although length of stay per patient has decreased (National Center for Health Statistics 2007
), there has been an increase in patient turnover and a decrease in hospital staffing (American Hospital Association 2007
). High patient turnover, increasing hospital patient volume, and decreased staffing may contribute to all of the increasing PSI rates due to less medical attention per patient by health care staff. The effect of surveillance must also be taken into account. Unless a condition is documented, it does not exist in this surveillance system. While accuracy is paramount in quality reporting, the assiduity of surveillance may have the perverse effect of increasing PSI rates. For example, one study found a 10-fold increase in DVT rates based on a differing surveillance technique (Haut, Noll, and Efron 2007
Finally, it should be mentioned that of the seven significantly increasing PSIs, five are directly associated with surgery: accidental puncture/laceration, post-op physiologic and metabolic derangement, post-op sepsis, post-op pulmonary embolus or deep vein thrombosis, and post-op respiratory failure. While post-op physiologic and metabolic derangement and accidental puncture/laceration are relatively rare, the remaining three significantly increasing PSIs are unfortunately high frequency. These high-frequency, significantly increasing surgically related PSIs (post-op sepsis, post-op pulmonary embolus or deep vein thrombosis, and post-op respiratory failure) are also three areas with readily identifiable means of improvement (Encinosa and Hellinger 2008
). The remaining two significantly increasing PSIs not directly related to surgery are selected infections due to medical care, which is relatively rare, and decubitus ulcer, which may be influenced by the present on admission status.
Seven of the PSIs showed statistically significant decreasing trends: birth trauma injury to neonate (−17.79), failure to rescue (−6.05), postoperative hip fracture (−5.86), obstetric trauma–vaginal without instrument (−5.69), obstetric trauma–vaginal with instrument (−4.11), iatrogenic pneumothorax (−2.5), and postoperative wound dehiscence (−1.8). All of the obstetric complications have shown decreases in rates with the greatest drop in incidence for PSI birth trauma–injury to neonate, with an annual decrease of nearly 18 percent. These rates may be influenced by the increased use of both elective cesarean section and c-section for difficult labor as well as decline in the use of VBAC (Ford, Bateman, and Simpson 2006
). Regarding PSI postoperative hip fracture, increased fall precautions during hospitalization as well as increases in availability of in-house physical therapy may have helped lower the rate (von Renteln-Kruse and Krause 2007
). Use of ultrasound for placement of central lines and thoracentesis may have reduced rates of PSI iatrogenic pneumothorax (Karakitsos, Labropoulos, and De Groot 2006
). The impact of resident work rules upon the decline of iatrogenic pneumothorax and other PSIs is not conclusive (Poulose, Ray, and Arbogast 2005
). The decrease in failure to rescue may be due to increased solicitation of DNR/DNI status from patients upon admission, thus leading to better selection of candidates for resuscitation. Another potential contributor is better training of code teams, more rested resident physicians, and perhaps the implementation of rapid response teams (Dacey, Mirza, and Wilcox 2007