There are multiple indications for open abdominal management (OAM), such as damage control surgery for severe trauma, abdominal compartment syndrome, severe peritonitis, and bowel ischemia [1,2]. In the International Register of Open Abdomen report in 2017, of the enrolled patients who underwent OAM, over 75% were non-trauma patients [3], and the approach is gaining popularity worldwide.

However, past reports have warned about the overuse and specific complications of delayed primary fascial closure [4,5]. The World Society for Emergency Surgery in 2018 recommended that the fascia should be definitively closed as soon as possible [6]. Several indications for OAM may be associated with the overuse of the second-look laparotomy partly because there is no specific standard timing for closing the fascia after abdominal surgery.

The IROA study found a linear correlation between the duration of OAM and the incidence of complications (e.g., patients with 9 days of OAM have a complication rate of > 80%); the morbidity rate would therefore increase with longer durations of OAM [3]. Moreover, in the follow up analysis in 2019 of the International Register of Open Abdomen report, complication rates after definitive closure differed significantly between age groups (16–40 years group: 48.5%, 41–60 years group: 55.0%, 61–80 years group: 69.5%, and over 80 years group: 55.4%) [7].

Thus, surgeons should be aware of the threshold number of OAM days at the first operation in each case, and consider the patient’s age. However, there are no reports analyzing the three-dimensional relationship between the complication rate after definitive closure, the patient’s age, and the duration of OAM.

In countries with aging populations, the average age of individuals who are likely to undergo emergency abdominal surgery, including OAM, has increased. In some reports, age was revealed as an independent predictor of complications including surgical site infections (SSIs) and postoperative pulmonary complications [8,9]. Therefore, clinicians should use caution when employing this treatment strategy in elderly individuals.

There is little evidence supporting indications for OAM for elderly non-trauma patients. Elderly patients tend to have reduced physical strength, which may complicate the option of OAM. O’Meara et al [10] reported that older non-trauma patients were at higher risk for fascial complications after OAM and primary fascial closure.

Little is known about the association between the duration of OAM and patient age, and there is no threshold for the duration of OAM. In the present study, the association between patient age and the duration of OAM was evaluated. The utility of the “Index for the duration of open abdominal management” (IDOM) for preventing the incidence of OAM-related complications after definitive closure was assessed in its capacity to predict postoperative OAM-related complications.

This was a retrospective chart review study, therefore, the requirement for informed consent was waived. Ethical approval was obtained from the hospital institutional review board (no. 108) and the study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

Data from 65 patients who underwent OAM from August 2015 to August 2018 at our hospital were analyzed in this retrospective, observational study. Exclusion criteria were as follows: age < 20 years (considered minors), duration of OAM < 24 hours, death before definitive closure, and existence of pneumonia before OAM. Duration of OAM was defined as the period from the day of the first operation to the day of fascial closure. OAM of all patients was performed by an acute care surgery team using an established protocol for managing peritonitis [11]. This team decided the timing to close the fascia safely without contamination of the abdominal cavity and to prevent edema of the bowel and retroperitoneum.

For all patients undergoing OAM, the intra-abdominal condition (i.e., the nature of fluid in the peritoneal cavity and edema of the bowels) was assessed daily. At every assessment, the decision to continue with OAM was re-evaluated and multiple (second, third, fourth, etc.) looks were performed at short intervals, especially when the surgeon elected to leave the abdomen open to reassess bowel viability and hemorrhage at a later stage. During OAM in the present study, surgeons employed negative-pressure wound therapy (RENASYS TOUCH, Smith and Nephew plc., London, UK; or ABTHERA, KCI Licensing, Inc., Mississauga, Ontario, Canada) for temporary abdominal closure. Patients were extubated after fascial closure.

Medical records were reviewed to obtain demographic data, clinical variables, complications, duration of the first operation, number of days on a ventilator, and length of stay in the intensive care unit. In particular, the relationship between OAM-related complications, including postoperative respiratory failure (PRF) or wound complications, and OAM duration was examined. PRF was defined as, “pneumonia, unplanned ventilation, or failure of ventilator weaning without tracheotomy,” as previously described [12]. Wound complications included superficial and deep SSIs, enteroatmospheric fistulae, and wound dehiscence.

Over the three-year study period, 65 non-trauma patients underwent OAM (Figure 2). The demographic data of the patients, was stratified into above- and below-IDOM groups (Table 1). The median age of patients was 73 years (IQR: 65–80), and 41.5% were male.

The relationship among overall complications, OAM-related complications, and duration of OAM was assessed (Figure 3). When OAM lasted five days or more, overall complications inevitably developed; in contrast, OAM-related complications did not necessarily occur even with an OAM duration of 9-days.

No statistically significant differences in the duration of the first operation or in-hospital mortality were observed between the two groups (Table 2). OAM duration, OAM-related complications, overall morbidity, length of intensive care unit stay, and ventilation duration were significantly different between the two groups. Among patients with wound complications, nine had partial dehiscence of the fascia, while five and seven patients had superficial and deep SSIs, respectively. No enteric fistulae were observed in any of the patients. The overall mortality was 14.3% and 8.1% in the above-and below-IDOM groups, respectively (Figure 4).

Patients in the above- and below-IDOM groups had 21, and 8 OAM-related complications, respectively. Therefore, the IDOM had a 72.4% sensitivity, 80.6% specificity, 75.0% positive-predictive value, 78.4% negative predictive value, a positive likelihood ratio of 3.72, and a negative likelihood ratio of 0.34, for predicting postoperative OAM-related complications.

In this study, a new and simple benchmark was developed to estimate the duration of OAM with respect to patient age, and its efficacy in OAM patients was examined. The findings suggest that to prevent postoperative complications, fascial closure should be performed preferably within the time indicated using the IDOM.

OAM yields multiple benefits in emergency abdominal surgery. It decreases the duration of the first operation and facilitates drainage of peritoneal effluents containing cytokines. However, occasionally, OAM can be detrimental to patients receiving critical care. Negative pressure in the abdominal cavity causes excessive loss of body fluids and increases the risk of developing gastrointestinal fistulas.

Miller et al [13] reported a statistically significant increase in complications among a cohort of trauma patients (mean age of 35 years) when the duration between the initial operation and fascial closure exceeded 8 days. Fox et al [14] also reported shorter hospital and intensive care unit stays among a cohort of trauma patients, (mean age of 36 years) that underwent abdominal closure within 7 days after damage control laparotomy compared with patients who underwent late closure.

It has been reported that postoperative complications in OAM are independent of patient age [15,16], whereas other studies have indicated that advanced age is independently related to mortality in emergency abdominal procedures [17,18]. In a study of non-trauma patients, age was reported as an independent risk factor for postoperative complications [11]. Furthermore, there has been inadequate research on OAM in patients older than 80 years; thus, the utility of OAM for elderly patients remains largely unknown [19]. It has been reported that, regardless of age, 16–20% of non-trauma OAM patients develop PRF, 24–27% develop wound complications, and the mortality rate is 19–30%; however, the mortality rate remains highest among octogenarians (37–45%) [11,19,20,21].

Kahn et al [21] reported that the two major complications of OAM were respiratory failure and deep SSIs. PRF is considered an OAM-related complication; however, the precise mechanism underlying this condition remains unknown. Ventilator-associated pneumonia, atelectasis due to high intra-abdominal pressure, and pleural effusion are suspected causes of respiratory failure in patients undergoing OAM. Age has been identified to be independently associated with an increased risk of pulmonary complications after emergency abdominal surgery [9,22]. There is an important relationship between OAM and PRF.

This is the first study to focus on the association between patient age, OAM duration, and morbidity spontaneously. The strength of this study is the wide range of patient ages (20–92 years; median age 73 years: IQR: 65–80), which allowed the identification of the relationship between the IDOM and morbidity. This research can form the basis for clinicians to plan OAM duration from the outset, according to patient age. Closing abdominal fascia within the time indicated by the IDOM may reduce the incidence of severe complications in patients undergoing OAM.

One limitation of this study is that the cut-off value calculated using the IDOM is arbitrary, because we sought an index that is simple to use. The cutoff value was set using the data shown in the Figure 1. Sensitive analysis was performed using another number (IDOM: 9 - the tens digit of each age had a sensitivity of 0.862, specificity of 0.5. IDOM: 10 - the tens digit of each age had a sensitivity of 0.724, specificity of 0.806. IDOM: 11 - the tens digit of each age had a sensitivity of 0.448, specificity of 0.861.) Thus, IDOM: “10 - the tens digit of each age” is most optimal.

This new index has a relatively high sensitivity and specificity for the prediction of OAM-related complications. As an example, the Mannheim Peritonitis Index score, used to predict morbidity in patients with secondary peritonitis, has a sensitivity of 80.65% and a specificity of 57.89% [23]. Compared to Mannheim Peritonitis Index, the IDOM index has a lower sensitivity (72.4%), and a higher specificity (80.6%).

Another limitation of this study is its retrospective design. Therefore, causal relationships between the duration of OAM and patient characteristics could not be inferred. In addition, this prediction model could not be validated owing to an inadequate number of cases with data pertaining to patients’ age and OAM duration.

Therefore, future prospective studies with larger sample sizes should be conducted to validate the predictive value of this simple index in terms of OAM-related complications, and to verify whether the incidence of such complications can be reduced using an IDOM-guided management strategy.

OAM has a wide range of indications and a widespread use. Although OAM is a valuable complementary procedure that can be used to improve the survival rates of critically ill patients undergoing surgery, a longer OAM duration than the IDOM is associated with an increase in the incidence of complications. IDOM may have the potential for predicting postoperative complications at the outset of OAM. In the future, studies in a larger cohort addressing the effectiveness of OAM strategy will be performed using the IDOM.