The new guidelines for intensive care unit (ICU) admission, discharge, and triage published in 2016 recommend that patients with a heightened risk for postoperative instability or decompensation should be closely monitored and managed in a higher-level care unit rather than in the ward during the immediate postoperative period.1 Patients with comorbidities may even become critical during the perioperative phases of general surgeries. In fact, mortality at postoperative days 30 and 90 in patients with an American Society of Anesthesiologists physical status (ASA PS) classification III—i.e., with severe systemic disease—and ASA PS classification IV—i.e., with severe systemic disease that is a constant threat to the patient's life—went up to 0.5–30% after miscellaneous operations.2–4 Therefore, high-risk surgical patients, such as those with ASA PS III and IV, will have better outcomes when they remain in the ICU rather than in regular surgical wards, even during the immediate postoperative period. In daily hospital settings, immediate postoperative care for high-risk patients is frequently provided in an ICU environment. However, elective surgical patients with severe comorbidities are generally noncritical before surgery. They are electively admitted to the ICU when there is a concern that they might become critical postoperatively. This ICU admission monitors their postoperative status rather than providing care or continuing surgical intervention as in cardiac surgery, for which specific risk-adjustment models after ICU admission have been developed, validated, and reported.5,6 However, for other general surgeries that usually do not require a postoperative ICU stay, it remains uncertain whether postoperative ICU admission is beneficial for high-risk surgical patients. This issue should be addressed considering the generally limited intensive care resources.

Our institute has arranged and determined absolute indications for the ICU admission of elective surgical patients. For example, intermediate- to high-risk surgeries7 in comorbid patients (ASA PS≥III) are absolute indications for ICU admission. However, the postoperative ICU admission of these patients is sometimes canceled because of a shortage of ICU resources. Thus, we can investigate whether postoperative vigilance in the ICU contributes to better patient outcomes by comparing the outcomes of postoperative ICU-admitted and non-ICU-admitted surgical patients with comorbidities who underwent intermediate- to high-risk surgeries. This retrospective clinical chart review study aimed to determine whether a short postoperative ICU stay could improve outcomes in surgical patients with a high level of comorbidity, classified as ASA PS III or IV. To reduce selection bias, we compared the outcomes of propensity-matched patient pairs with or without intensive care. Using this technique, we analyzed patients who were equally eligible to be treated postoperatively in the ICU or in general surgical ward. Additionally, we excluded patients if there was a high likelihood of admission to only one of the postoperative care environments.

The Ethics Committee of the Nara Medical University Hospital approved this observational cohort study (Kashihara, Japan; study number 1094). The Institutional Review Board waived the need for written informed consent. This study case–control study was performed in accordance with the recommendations of the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) consensus statement.8 We reviewed elective miscellaneous surgical cases performed at Nara Medical University between January 2007 and December 2015 and extracted the records of 1218 consecutive surgical patients with ASA PS III or IV. We investigated the patients’ statuses at postoperative days 30 and 90.

Data handling

Data from 36,880 patients who underwent surgery between January 2007 and December 2015 were reviewed. The present study included the following exclusion criteria (Fig. 1): (1) emergency patients; (2) intraoperative death; (3) patients who absolutely required ICU admission for surgical reasons according to our institutional protocol except for the last clause (Table 1); (4) low-risk patients not requiring ICU admission in our institute, such as electronic convulsive therapy, breast surgery, dental surgery, ophthalmic surgery, and bone marrow harvesting; (5) patients aged <20 years; (6) patients who did not undergo general anesthesia; and (7) patients classified as ASA PS I—i.e., normal health—or ASA PS II—i.e., mild systemic disease.2 These were used as one of the exclusion criteria to identify adult intermediate- to high-risk surgical patients with comorbidities, i.e., “borderline” patients who require a postoperative intensive environment. Regarding exclusion criterion (4), other minor risk surgeries, such as those described previously (minor gynecological or orthopedic surgeries, etc.),7 were not excluded because these surgical patients with severe comorbidities were sometimes managed on demand in the ICU after surgery. Consequently, non-major neurological surgeries, including supine surgery, head and neck surgeries, non-major thoracic surgeries, laparotomies, orthopedic surgeries, and superficial surgeries, were included.

Figure 1.

Flowchart of the study population. ASA PS: American Society of Anesthesiologists physical status classification.

(0.15MB).

Table 1.

Absolute indication for the ICU in elective surgical patient at Nara Medical University Hospital.

•Post-cardiovascular surgery

•Post-major lung surgery

•Post-esophageal surgery

•Post-microvascular anastomosis requiring immobilization

•Post-long surgery (preoperative estimated duration of surgery >10h)

•Post-major neurosurgery

•Post-intermediate to high risk surgeries in the comorbid patients (ASA PS≧3)

ASA PS: American Society of Anesthesiologists physical status classification.

The clinical characteristics of the unmatched groups (n=273 for ICU admission and n=945 for non-ICU admission) and the two propensity-matched groups (n=248 each) are presented in Table 2. Before matching, the covariates were not statistically different between groups; however, several variables, including age, ASA PS, surgical risk, surgical site, transfusion requirement, massive bleeding, and duration of surgery, were not balanced adequately, as judged by the absolute standardized difference of >0.1. After matching, the covariates were balanced adequately. Records of intraoperative adverse events assumed to be correlated with poor outcomes showed that four patients in the non-ICU admission group developed transient severe bradycardia close to cardiac arrest, which was easily treated using atropine, but recoded as intraoperative adverse events. These events were not related to poor outcomes.

Patient outcomes are summarized in Table 3. There was no difference in poor outcomes on postoperative day 90 between groups, regardless of whether they were matched (ICU group vs. non-ICU group: 13% vs. 14% before matching, 13% vs. 11% after matching, respectively). Similarly, no group differences in mortality were found at postoperative days 30 and 90, regardless of whether the matching procedure had been performed. Before matching, no group differences were found in the rate of emergency ICU admission or readmission; however, the value combined with the rate of postoperative prolonged ICU stay was significantly higher in the ICU group than in the non-ICU group. Conversely, after matching, the rate of emergency ICU admission or readmission was higher in the non-ICU group than in the ICU group. However, the value combined with the rate of postoperative prolonged ICU stay was not statistically different between the groups.

A multivariable logistic regression analysis by forced-entry methods was performed with the following candidate factors: age, height, weight, duration of surgery, patient posture during surgery, combination of regional anesthesia, emergency ICU admission or readmission, and postoperative prolonged ICU stay (emergency ICU admission or readmission was excluded because ρ=0.806, although this item showed a significant value), and ICU admission. ICU admission was included to assess whether ICU admission was associated with patient outcomes. The results showed that body weight, the provision of regional analgesia combined with general anesthesia, emergency ICU admission or readmission, and postoperative prolonged ICU stay were independently associated with poor outcomes (Table 4). However, ICU admission was not associated with patient outcomes. Using the likelihood ratio test, the discrimination of the final model was significant (p<0.0001). Furthermore, the Hosmer–Lemeshow statistic did not reject a logistic regression model fit (p=0.6473). The explanatory model based on these variables had an area under the receiver operating characteristic curve of 0.654 (95% CI, 0.627–0.681). Post hoc power calculations were performed for this forced-entry multivariate logistic regression model using eight variables. Standard methods were used to estimate the sample size for the multivariate logistic regression analysis, indicating a requirement of at least 10 outcomes for each independent variable.15 With a 13.9% (169/1218) rate of poor outcomes in the study population, 576 patients were required to appropriately perform the multivariate logistic regression analysis. Therefore, the sample sizes used were of sufficiently size to build the multivariate models.

The present study investigated whether a brief ICU stay could improve outcomes in patients with severe comorbidities after miscellaneous elective surgeries. Based on the retrospective analysis of patient data, postoperative ICU admission failed to affect any meaningful outcomes. The rate of emergency ICU admission or readmission was significantly higher in the non-ICU group than in the ICU group after matching. However, this difference disappeared when the rate of postoperative prolonged ICU stay in the ICU group was combined with the rate of readmission. This study was conducted retrospectively. Therefore, it is difficult to judge whether prolonged ICU stay prevented ICU readmission or whether some of the elective ICU patients deteriorated during the first ICU day as much as non-ICU patients who would be emergently admitted to the ICU. Interestingly, the additional multivariate logistic regression analysis of the entire cohort confirmed that postoperative ICU admission was not associated with improved patient outcomes; however, this analysis showed that low preoperative body weight was negatively associated with patient outcomes, while the provision of regional analgesia combined with general anesthesia was positively associated with patient outcomes. In addition, emergency ICU admission, readmission, or postoperative prolonged ICU stay was also strongly associated with poor outcomes.

As noted earlier, apart from postcardiac surgery, ICUs that are staffed with critical care caregivers are known to improve patient outcomes. For example, Dimick et al. have shown that intensive care provided by ICU physicians was associated with shorter durations of stay, lower hospital costs, and a decreased frequency of postoperative complications following esophageal resection.16 Varelas et al. reported that a neurointensivist-led team model showed a relative reduction in in-hospital mortality and improved Glasgow Coma Scale scores in head injury patients.17 Additionally, Tang et al. observed a worse-than-predicted survival in the absence of ICUs for critically ill patients who received mechanical ventilation in general wards.18 Overall, ICUs that are staffed with critical care caregivers are considered beneficial for patients in specific situations and for the critically ill. Conversely, it has been suggested that specific procedures in elective surgical patients, such as a craniotomy, do not require postoperative intensive care.19,20 Moreover, among ICU admissions monitored only on their first ICU day, more than 90% of low-risk patients did not receive subsequent active life-supporting treatment.21 Recently, Kahan et al. conducted an international cohort study and reported that they did not identify any survival benefits from critical care admission following elective surgery.22 Although they provided several critical care treatments for a wide range of postoperative patients, post hoc sensitivity analyses exploring the effect of postoperative critical care admission within a high-risk subgroup of patients and according to university hospital status also failed to show a protective effect of critical care in either of these analyses.

Because surgical patients with severe comorbidities are generally not in critical condition before elective surgery, they may be too healthy to benefit from ICU admission for mere monitoring to prevent them from becoming critical postoperatively. The increasing use of less invasive techniques in modern surgery and advances in anesthesia contribute to improved patient outcomes, which may mask the benefits of ICU admission for miscellaneous elective surgical patients with severe comorbidities. As stated previously, the postoperative ICU admission of these patients is sometimes canceled even though they display an absolute indication for the ICU as elective surgical patients in our institute because of a shortage of ICU resources. The occasional cancelation may be due to the underlying argument that it remains uncertain whether postoperative ICU admission is beneficial for such high-risk surgical patients. We believe that this study helps answer this clinical question. However, it remains unknown whether postoperative ICU would be beneficial in patients with a high likelihood of ICU admission because of missing comparison targets.

Moreover, the results showed that a low preoperative body weight was negatively associated with patient outcomes, the provision of regional analgesia combined with general anesthesia was positively associated with patient outcomes, and emergency ICU admission, readmission, or postoperative prolonged ICU stay was also strongly associated with poor outcomes. We would like to comment on these findings. Preoperative frailty has displayed an association with significant morbidity and mortality.23 Low body weight is an important marker of frailty.24 Therefore, it is plausible that a low preoperative body weight was associated with poor outcomes in our population. Although it remains unclear whether regional analgesia combined with general anesthesia reduces mortality, it may have contributed to improved postoperative pain management and enhanced postoperative mobility, rehabilitation, and discharge destination.25,26 Therefore, it is also reasonable to conclude that regional analgesia combined with general anesthesia was associated with better outcomes in the present study. A preoperative exercise and nutritional support program may help reduce sarcopenia and improve postoperative outcomes in elderly sarcopenic patients with gastric cancer.27 These reports imply that rather than strict ICU vigilance for patients such as those in our study, the preoperative treatment of frailty and early postoperative mobilization might contribute to better patient outcomes. Interestingly, Levy et al.’s study demonstrating the negative effect of intensivists suggested that some of the routine practices and procedures in critical care may not be optimally beneficial and that the cumulative use of additional interventions may negatively affect patient outcome.28 This suggestion is relevant for the present study because our ICU patients wore extra-monitoring devices, such as an invasive arterial blood pressure monitor, which may have limited patient mobilization. However, recently, early mobilization has been observed in the ICU even in patients with mechanical ventilation or other devices such as ECMO.29 Therefore, this concern might be overcome in the future. Furthermore, emergency ICU admission and readmission and prolonged ICU stay may be indications poor clinical progress. Therefore, it is not unusual that poor progress was directly associated with poor outcomes.

The present study contains several limitations. To minimize the effect of selection bias on outcomes, propensity score matching for clinical characteristics was used to reduce distortion by confounding factors. However, in this retrospective study, several unmeasured or irretrievable variables might still have confounded patient outcomes. Second, mortality was not used as a primary outcome because the mortalities at postoperative days 30 and 90 were too small to perform meaningful analyses. Therefore, using mortality as a primary outcome measure would have required us to recruit many more patients to increase the statistical power. Another limitation was the study location of Japan, where the length of hospitalization is relatively long.30 Therefore, “not discharged to home” as an index of patient outcome cannot be adequately used for a direct comparison with other countries. The Japanese universal public insurance system is relatively generous in its support of hospitalization. Therefore, both a patient's medical status and his or her social background usually determine hospitalization in Japan. However, even in Japan, more than 90 days of hospitalization is considered quite long. Therefore, it is not unreasonable that “not discharged to home” at postoperative day 90 was taken as an outcome indicator, although the results cannot be generalized to countries with generally shorter hospitalizations. However, similarly, it is unlikely that “not discharged to home” after 30 days can serve as an appropriate outcome indicator. In addition, it is not possible to extrapolate the Japanese postoperative surgical ward setting to other countries and environments. The current findings might be irrelevant in much lower quality settings. Finally, many patients were excluded from this study based on the exclusion criteria. However, the exclusion procedures were necessary to appropriately select high-risk surgical patients who underwent elective miscellaneous surgeries that usually do not require a postoperative intensive care environment.

In conclusion, we investigated whether a brief ICU stay following miscellaneous elective surgeries could improve outcomes in patients with severe comorbidities. However, postoperative ICU admission failed to demonstrate any meaningful benefits. Because a low preoperative body weight was associated with poor outcomes and the provision of regional analgesia combined with general anesthesia was associated with better outcomes, other preoperative and postoperative interventions rather than intensive care monitoring might contribute to better patient outcomes in elective surgical patients with severe comorbidities.

Teppei Ogawa collected and analyzed all data. Satoki Inoue designed the study, collected and analyzed all data, interpreted the results, and wrote the manuscript. Michiyo Inada helped to collect and analyze the data. Masahiko Kawaguchi reviewed and helped modify the design of the study. All authors have read and approved the final manuscript.

This work was supported by departmental sources.

The authors declare that they have no conflict of interests.