RESULTS
During the research period 71 patients were admitted, and fifteen were excluded due to physical limitations. Thus, 56 patients were evaluated, of these 38 (63%) were male, mean age 61 ± 9 years, with an average BMI of 27 ± 5 km/m2, with the most prevalent comorbidity being sedentary with 19 (63%). The other data are shown in table 1.
The average walking speed in the slow group was 0.6 m/s, while in the non-slow group it was 1.2 m/s. Twenty patients (40%) were readmitted to the hospital during the observation period of 6 months. Of those, 14 (70%) were slow walkers, as defined by a gait speed of less than 1.0 m/s, and 6 (30%) were non-slow walkers. The 6 months rate of readmission was 58% (14/24; 95% CI 49% to 80%) among slow walkers and 17% (6/36; 95% CI 13% to 46%) among non-slow walkers (p = 0.002).In univariate analysis, gait speed, treated as a continuous variable, was associated with the primary outcome (HR 0.6; 95%CI 0.2 to 0.9), while age, gender, BMI, MV and CPB time were not (table 2). In the multivariate model including age, gender, BMI, MV and CPB time, gait speed remained the only variable associated with readmission (multivariate HR: 0.5, 95% CI 0.1 to 0.7 p=0.02; table 2).
DISCUSSION
Based on the results of this prospective cohort study, gait speed was associated with hospital readmission of patients undergoing to coronary artery bypass grafting. Walking more slowly (<1 m/s) was associated with hospital readmission, but variables such as age, male gender, BMI, MV and CPB team were not related to the outcome in six months.
Previous studies suggest that gait speed is an independent variable for mortality and hospital readmission in survivors of acute hypercapnic respiratory failure and heart failure11,12. Being an extremely simple and feasible test for the application of the practice, we suggest its adoption by hospital services aiming at reducing hospital readmissions, thus minimizing costs, improving the survival and quality of life of these patients.
Afilalo et al. demonstrated that patients with low gait speed in the preoperative period have a higher rate of morbidity and mortality during the ICU stay13. They also found that factors such as female gender and diabetics made up the slow speed group. In our study, we did not find any difference regarding gender, age or comorbidities, which may be associated with a smaller sample size in the present study. This result only reinforces the need to stratify patients with a higher risk of complications or hospital readmission, and gait speed is a useful tool.
In this rationale Sawatzky et al.14 found that the application of a program in the preoperative period can increase gait speed, with this effect remaining for up to three months after the procedure. On the other hand, Cerqueira et al.15 did not demonstrate any impact when applied to neuromuscular electrical stimulation in the postoperative period.
A possible explanation for reducing gait speed and increasing the risk of hospital readmission is fragility. It is considered a multidimensional syndrome resulting from the reduction of physiological reserves and an increase in physical and functional decline when exposed to external stressors16. After cardiac surgery, factors such as cardiopulmonary bypass, surgical incision, pleurotomy and duration of mechanical ventilation generate pulmonary dysfunction and decrease in physiological reserves17.
Bed restriction time and contributes to physical and functional decline18,19. Our group demonstrated that after myocardial revascularization it generates a decrease in functional capacity, observed through the six-minute walk test20. We found that performing inspiratory muscle training helps to minimize this decline and improve clinical outcomes such as length of hospital stay20,21.
Lal et al.22 demonstrated that the frailty assessed using the Edmonton scale is a predictor for the length of hospital stay and risk of readmission up to twelve months in elderly patients undergoing cardiac surgery. The combination of frailty assessment with gait speed will give the therapist fundamental information for the organization of an intervention protocol.
In Castro et al.23, it was evidenced that the greater distance covered in the 6MWT was associated with a shorter hospital stay, as a quick recovery after the surgical procedure allows walking autonomy that allows the transfer of this patient earlier for rehabilitation, and consequently reduce hospitalization time. In the study by Aikawa et al.24, they say that immediate post-surgical rehabilitation can be a means that enables the more agile development and recovery of these patients and found in the 6MWT that there was a significant increase in the distance covered and gait speed of these patients. Thus, comparing the studies presented, it can be understood that an early rehabilitation of patients after CABG is linked to a shorter hospital stay, consequently generating an improvement in gait speed when evaluated by the 6MWT.
According to Oliveira et al.25, it was evaluated that the CPB time has minimal influence on the patient’s ability to walk, the research shows that despite the occurrence of muscle inefficiency, generating a loss of postoperative strength, it does not interfere in the gait of patients themselves. Reinforcing with the results of this study, we analyzed that the CPB time had no correlation with the patients’ gait, as it statistically had no influence.
Borges et al.26 showed that patients undergoing cardiac surgery suffer adverse risks during hospitalization in the postoperative period, where they become more fragile due to some physiological changes that occur during the intervention, such as: motor disabilities and physical limitations that can be prolonged, and consequently, which may lead to future readmissions, the author also identified a vicious cycle of slow gait after surgery. The results of this study were similar to ours, in which it showed that patients undergoing CABG showed a decrease in gait speed due to several associated and already mentioned factors, and that it may possibly be associated with the risk of a hospital readmission.
The limitations of this study include the sample calculation, limiting the extent of its findings, absence of information on pulmonary function, which may have an influence on the performance of the gait speed test and the lack of a spirometric test.