SCM is an sepsis-related acute cardiac insufficiency syndrome unrelated to ischemia (5). SCM has a high incidence rate and is associated with a long length of hospital stay and high mortality (14). Importantly, it is a crucial factor affecting the prognosis of perioperative sepsis patients. Sato et al. (14) was the first to report the epidemiological characteristics of SCM, with the hospitalization and ICU duration of SCM patients being significantly longer than in patients without SCM (median, 43 days vs. 26 days, P=0.04; 9 days vs. 5 days, P<0.01, respectively). The in-hospital and 30-day mortality of SCM patients were 24.1% and 20.7%, respectively. Song et al. (15) also reported an ICU mortality rate of 24.5% for SCM patients.
In the current study, the 30-day mortality in the SCM group was as high as 32.4%, and this was significantly higher than in the NSCM group (24.1%). This is also higher than the in-hospital mortality reported in previous studies. Further, the results also showed that SCM significantly increased the utilization rate of mechanical ventilation during ICU hospitalization and the duration of mechanical ventilation, the incidence of tracheotomy, the utilization of CRRT, and the mortality during hospitalization. In addition, SCM significantly increased the length of ICU admission and the total cost of hospitalization. To our best knowledge, this study is the first to report the epidemiological data of postoperative SCM in patients with perioperative sepsis, providing a basis for its early prevention and treatment.
With the introduction of minimally invasive surgery, endoscopic surgery has become widely used in various clinical specialties (16). However, we found that most cases of postoperative SCM occurred after endoscopic surgery. Therefore, we conducted this study to determine whether endoscopic surgery is a risk factor for postoperative SCM in patients with sepsis. Multivariate logistic regression analysis confirmed that endoscopic surgery is a risk factor for postoperative SCM in sepsis patients. This could be because of the need to build artificial pneumoperitoneum endoscopy surgery (17) that in turn leads to increased abdominal pressure, increased intra-abdominal infection lesions by factors such as blood flow to the risk of further proliferation. The increased systemic inflammatory response causes enhances the release of inflammatory factors, and these factors can inhibit myocardial function and cause heart failure (3). Another cause is patient positioning during endoscopic surgery, which results in the decrease of functional residual capacity. The pneumoperitoneum pressure also increases the airway peak pressure increase and reduces respiratory compliance, leading to inadequate ventilation. Moreover, oxygenation after abdominal surgery might further aggravate the acid-base imbalance (18). Overall, several factors possibly influence the higher risk of SCM in endoscopic surgery than in open surgery. However, research on the specific mechanism of SCM from endoscopic surgery is still lacking, and further experimental studies are needed to establish the relevant factors or mechanisms.
Our results showed that a SOFA score ≥7 is a risk factor for postoperative SCM in patients with sepsis. Patients with a SOFA score ≥7 had a 46.831-fold higher risk of SCM than those with a score of <7. A SOFA score of ≥7 indicates significant dysfunction of at least one organ, which indirectly reflects the severity of sepsis at the systemic level. Bergenzaun et al. first demonstrated in a prospective, observational, cohort study that the SOFA score (OR: 1.6 (95% CI: 1.1-2.3), P=0.018) is an independent predictor of mortality in patients with septic shock (19). A subsequent prospective study involving 48 sepsis patients confirmed that the SOFA score is a good predictor of mortality in sepsis patients (20). Similar findings were obtained in this study, but we further showed that a SOFA score ≥7 increased the risk of SCM, providing more accurate data for the early prevention and treatment of SCM. However, compared with these two previous studies, this is only a retrospective study, and further prospective studies are needed to validate our findings.
Previous studies have shown that hyperlactic acid is a risk factor for SCM (14). An elevated lactic acid level is a manifestation of impaired systemic microcirculation and tissue insufficiency. A serum lactic acid value of >4 mmol/L at admission is associated with a high mortality rate, and patients with persistently high lactic acid levels for more than 24h have poor prognosis (21). In this study, there was a significant difference in the proportion of patients with high lactic acid value (≥4 mmol/L) between the SCM group and the NSCM group during the screening process, but there was no significant correlation between the lactic acid level and postoperative SCM in the multivariate logistic regression.
The differences in the results between studies may be due to the differences in the included population, and the results of previous studies cannot be generalized in the patient population targeted in this study. Meanwhile, we found that a high SOFA score is an independent risk factor for SCM in patients with sepsis, suggesting that multi-organ failure and lactic acidosis may be the result of systemic dysfunction, rather than the direct cause of SCM.
Age is considered to be an independent risk factor for SCM (9). Aging-related physiological changes lead to decreased organ function and immune function, and these are usually accompanied by various chronic diseases. Resistance to systemic inflammatory response in sepsis is weakened, leading to an increased risk of SCM (20). However, the influence of age is still controversial. Sato et al. (9) reported a significant increase in the incidence of SCM in young and male patients in their study. In the current study, multivariate logistic regression analysis showed that the incidence of SCM was correlated with younger age (OR, 0.96; 95% CI: 0.94-0.99), but the mechanism is still unclear and needs further analysis. Further, unlike previous studies, although the SCM group in our study was older than the NSCM group (median age: 70 years vs. 66 years), the difference was not significant. This conflicting findings between the current and previous studies may be due to the retrospective nature of the study and the limitation of the overall sample size. Further investigations are needed to confirm that age as a risk factor for SCM after sepsis.
We also found that the maximum dose of norepinephrine was significantly higher in the SCM group than in the NSCM group, while the minimum platelet value was significantly lower (P<0.05). The proportion of patients with high initial lactic acid value, maximum lactic acid value, maximum PCT value, and maximum body temperature was significantly higher in the SCM group than in the NSCM group (P<0.05). However, multivariate logistic regression analysis showed that these indicators were not independent risk factors for perioperative SCM. This could be due to the limitations of this study. First, this was a retrospective study. Although the results indicate a correlation between the risk factors and outcome, the relationship is not causal. Second, because this was a retrospective study, cardiac function was measured using different methods including echocardiography and Picco hemodynamic monitoring. This difference can lead to biases in the population that may affect the study results. However, studies have shown the consistency between cardiac ultrasound and Picco for cardiac function assessment (13). Third, a unified diagnostic standard for SCM is yet to be established. At present, SCM is diagnosed according to the following clinical characteristics: (1) decreased ventricular systolic force; (2) left ventricular dilation under normal or low filling pressure; and (3) right ventricular dysfunction and/or left ventricular dysfunction with reduced infusion response. However, we used a more stringent diagnostic criteria for SCM, and required the identification of reduced cardiac systolic function to exclude patients with primary cardiac dysfunction. Fourth, because most of our patients had decreased cardiac function on admission, some patients who might have abnormal basic cardiac function combined with sepsis were included in the SCM group. To reduce the influence of this limitation, we included improvement of cardiac function after sepsis treatment in the diagnostic criteria for SCM. Finally, only 269 patients were included in this study. From the perspective of risk factors, a larger sample size is needed to obtain more reliable results. Further prospective studies are needed to verify the results in this study.