Late surgical complications after hospital discharge incur significant disability and cost,22, 23
and are proposed by some researchers and policy-makers as metrics of health care quality and safety.24, 25
Among general surgery operations, colon and rectal resections account for a disproportionately large share of complications and their resulting costs,3
and many post-colectomy complications arise only after uncomplicated discharges.4, 5
As a result, there is significant interest in understanding key risk factors for post-discharge complications and readmission after colectomy, and targeting high-risk patients for early prevention and management of adverse events. We have found here that the simple 10-point intraoperative Surgical Apgar Score remains a useful measure of these patients' risk of major complications, not only in the immediate postoperative period, but well beyond the index hospitalization.
Among patients discharged from the hospital without an adverse event, those with the worst intraoperative scores—4 or less—were four times more likely than average-risk patients to experience a subsequent complication within 30 days of surgery. About one in four of these lowest-scoring patients suffered late complications, compared with just 3% of those with the highest scores (9 or 10). Despite the relatively low prevalence of scores ≤4 (6% overall), the consistent trend toward worse outcomes, even at the extremes of the scale suggests that the score has good discriminative ability across the full point spectrum.21
If the Surgical Apgar Score were routinely recorded in the operating room, therefore, surgeons could use it as a quantitative adjunct to their subjective impressions of the operative course, to scale their expectations for both early and late complications after colectomy. Patients thereby identified as highest-risk for post-discharge complications, could be targeted for stricter discharge criteria, earlier follow-up appointments or phone contacts, and/or ancillary care such as home care visitation, with a goal of early detection and mitigation of late adverse events.26–28
Since we and others6, 9
have found that most post-discharge complications are infectious in nature, we could imagine interventions such as scheduled temperature surveillance, wound examinations, and/or white blood cell analyses as means of early diagnosis and treatment for patients considered high risk. Any such interventions would require careful development and testing to determine whether they actually reduce the severity and/or incidence of adverse events.
The association of an intraoperative metric like the Surgical Apgar Score with the incidence of post-discharge complications suggests that perhaps even these late postoperative outcomes are related to condition and events in the operating room. Still, its components are not necessarily independent predictors of patient outcomes. In our previous work,14
we found that the Surgical Apgar Score was closely correlated with a variety of other important patient- or procedure-related risk factors. Yet, even after detailed adjustment for comorbidity and procedure-specific risk factors, the amount of blood loss, lowest heart rate and lowest blood pressure were still important predictors of the risk of a major complication.
In accordance with our findings, Kariv et al.9
observed that blood loss was nearly doubled among patients who later required unplanned admissions after, but this difference did not reach statistical significance among their sample of 300 colectomy patients. Further, these results are consistent with previous observations that most surgical complications originate in the operating room,29, 30
and that intraoperative hemodynamics are powerful predictors of surgical outcome,31–35
even up to a year after the operation.36
And unlike complex multivariable algorithms that depend on the availability and interpretation of complex comorbidity and laboratory data, the Surgical Apgar Score can be available in real time, immediately usable for clinical decision-support and easily and inexpensively collected for any patient in any hospital.12, 13
Previous studies have failed to identify a consistent set of predictors for post-discharge complications among colectomy patients—some authors have gone so far as to conclude that these events might simply be unpredictable.4, 7, 8
The only predictors that have appeared in more than one study are perioperative steroid use,7, 9, 37
pulmonary comorbidity,9, 37
inflammatory bowel disease or ulcerative colitis as the indication for surgery,8, 37
and subtotal or total colectomy as the procedure.7, 8
And even this limited set of factors did not reach statistical significance in every study, often due to sample size limitations. We likewise found that steroids, inflammatory bowel disease and total/subtotal colectomy were significantly more prevalent among the post-discharge complication group, but these factors accounted for only a small share of the complications. Perhaps previous studies' difficulties in identifying consistent risk factors results from the lack of detailed metrics of operative performance and success in those analyses. Interestingly, despite trends toward short hospital stay after colectomy,10
we found no evidence that post-discharge complications were associated with premature discharge from the hospital—postoperative length of stay for patients with post-discharge complications was no different from that of patients free from complications altogether.
There remain several limitations to our study. First, NSQIP outcomes are not procedure-specific, so complications particular to alimentary tract surgery, such as anastomotic leaks or small bowel obstruction, may not be properly captured in all cases. The patient follow-up is, however, comprehensive and validated. Second, we are limited to a 30-day postoperative surveillance period, and do not capture later events beyond that timeframe, but longer-term studies have found that the great majority of events occur within this interval.5, 8
It is important to note that timing of complications is not a validated data point in the NSQIP. Yet the similarity in length of stay between patients without complications and those with only post-discharge complications suggests that misclassification is probably uncommon. Third, the sensitivity of low scores for detecting post-discharge complications is only moderate—even average- and high-scoring patients remain at some risk. Still, the overall discrimination for post-discharge complications (c-statistic of 0.68) is no worse than that of a risk-adjustment algorithm promoted elsewhere for benchmarking NSQIP outcomes in colorectal surgery.38, 39
Fourth, like the obstetrical Apgar score, this surgical score does not allow comparison of quality between institutions or surgeons, as its three variables are influenced not only by intraoperative performance, but also by patients' prior condition and the magnitude of the operations they undergo. Finally, this study evaluated only colectomy—not the full range of general and vascular surgery included in the NSQIP—so we do not know whether the score's predictive value would generalize as consistently for post-discharge complications as it does for complications overall.12, 13
And even among patients undergoing colon and rectal resections, their inherent risk varies widely, depending on particular procedure, indication, preoperative therapy, and other factors, so there may be subsets of patients among whom the score is more or less clinically useful.
We find here that a simple clinically-derived surgical outcome score, computed from intraoperative data alone, can provide useful measure of surgical risk after colon and rectal resection, even beyond the initial postoperative hospitalization. A more complex model, with more input variables might achieve better discrimination, but the Surgical Apgar Score could provide immediate and inexpensive information, derived from routine intraoperative data available in any hospital, regardless of resource availability. As a prognostic measure and a clinical decision-support tool, the Surgical Apgar Score might thus allow surgeons to effectively target patients for post-discharge monitoring and mitigation of late postoperative adverse events.