IJCS | Volume 33, Nº1, January / February 2019

26 Silva et al. Minimally invasive surgery–pain investigation Int J Cardiovasc Sci. 2020;33(1):24-33 Original Article were monitored by a transesophageal echocardiogram. Specific instruments for minimally invasive surgery were used. Management of postoperative thoracic pain The same protocol for induction and maintenance of anesthesia was followed in all patients. All of themwere intubated with a single lumen endotracheal tube that remained until extubation criteria weremet. In the first 48 hours, the patients received 1 g of dipyrone every 6 hours and 100 mg of tramadol every 8 hours for pain relief. According to each patient’s needs, 2 mg of morphine was administered. After this initial management, 500 mg of dipyrone were administered orally every 6 hours with or without 50 mg of tramadol, if necessary. Thoracic pain evaluation Thoracic pain was assessed using the Visual Numeric Scale (VNS). 15 Patients were instructed on the use of the VNS before the surgery. In the VNS, pain is rated from zero to 10, where zero indicates no pain and 10 the maximum pain level tolerated by the patient. Pain data were obtained on the third and seventh PO days. All patients were free of chest tubes at the moment of data collection. Patients were asked about the presence of pain, and for positive responses, pain location was registered, and PI rated on the scale. This was repeated for each pain site, if there was more than one. The pain drugs were then verified and registered. Statistical analysis Statistical analyses were performed using the Statistical Package for Social Science (SPSS) software for Windows TM , version 17.0 or the Statistica 12. A power of 80% was calculated for 34 patients (17 in each group). Normality of the data was determined using the Kolmogorov-Smirnov test, and homogeneity of the variance was assured by the Levene’s test. Results were expressed as mean and standard deviation (mean ± SD) for continuous variables; categorical data were summarized by frequencies and percentages and compared by a z test for two proportions. Data were parametric and compared using paired (within group comparisons) and unpaired (between group comparison) Student’s t test, with a confidence level of 95% (p < 0.05). Results Demographic and clinical data, including the presence of cardiovascular risks factors in the study groups are described in Table 1. Most patients were women, and age was not different between the groups. Weight and BMI were different between the groups, probably due to the non-inclusion of patients with BMI > 32 kg/m 2 in the MI group. The prevalence of comorbidities was not relevant, except for systemic arterial hypertension. Mitral valve insufficiency was the main diagnosis, followed by ostium secundum atrial septal defects, mitral valve stenosis, and ostium primum atrial septal defects. Patients were subjected to mitral valve surgical repair or replacement (MS n = 11 and MI n = 9) or surgical closure of an atrial septal defect (MS–n = 6 and MI-n = 8). Procedures for mitral correction included bioprosthetic replacement (7 in the MS group and 8 in the MI group) and mitral valve repair (4 in the MS group and 1 in the MI group). Valve resection, valve reconstruction, and semi-rigid ring annuloplasty were the main procedure for mitral repair. In the MS group, one patient required a Neochord placement, and no patient was subjected to pulmonary vein isolation. Regarding the procedures for atrial septal defect closure, there were one suture closure and five patch closures in the MS group and three suture closures and five patch closures in the MI group. Table 2 lists the POdata for theMS andMI groups. The MS procedure time was shorter than MI procedures. No difference was observed in mean aortic cross-clamping time or cardiopulmonary bypass time between the groups. Despite longer procedural times, MI patients needed less intensive care unit time for recovery in comparison with MS patients (Table 2). Mean hospital stay after the procedure was longer in the MS than in MI group. None of the patients hadmajor complications, stroke or death after the surgery. The PO pain evaluation indicated that most of the patients reported pain on the third PO day (MS = 94.1% and MI = 88.2%; p = 0.5410). On the seventh PO day, significantly more patients were free of pain in the MI group compared with the MS group (MS = 94.1% and MI = 64.7%; p = 0.0341). The patients in the MI group reported fewer pain sites than the patients in the MS group (Figure 1) on the third (MS = 3.2 ± 1.5; MI = 1.5 ± 1.2; p = 0.001) and seventh (MS = 3.1 ± 1.4; MI = 0.9 ± 0.9; p = 0.000) PO day.