Effect of Motivational Interview as a Strategy in the Reduction of Blood Pressure.

The lead researcher is a cardiovascular nurse specialist with 10 years of experience in the care of patients with heart disease and she will be responsible for the application of the Motivational Interviewing (MI) technique in the appointments for the intervention group. She also participated in an intensive workshop about MI, which followed the recommendations of the Motivational Interviewing Network of Trainers19 in 2013, and more recently, in 2015 and 2016, she participated in two workshops on advanced MI techniques. During the study there will be monthly supervision with another specialist. The training and the supervision will be the responsibility of a PhD researcher in Psychiatry with consistent experience on Motivational Interviewing and training conducted in the United States with Miller and Rollnick.

The sample size was calculated with WinPepi 11.20 software. Sample size was estimated in 100 patients, 50 in the intervention group (IG) and 50 in the control group (CG), considering a difference of 8 mmHg between groups, standard deviation of 14 mmHg, 80% power, and alpha of 0.05. Adding 20% of losses the sample will have 120 patients, 60 for each group.

Hypertension outpatients of Hospital de Clínicas de Porto Alegre (HCPA) will be identified by the appointment book and invited to participate in the study through telephone calls. The first appointment will consist in obtaining the ICF and confirmation of eligibility. After ICF's signing and confirmation of eligibility, the patient will be randomized to one of the groups. Participants of both groups will attend monthly appointments: first appointment (D0), appointment of 30, 60, 90, 120, and 150 days, totaling six individual encounters, previously arranged in the Clinical Research Center (CRC) of HCPA, with an average duration of 30 minutes.

The randomization list was generated through the website www.randomization.com. The list will be in possession of a professional of the research group, however non-participant of this project. The allocation group of each patient will be hidden by opaque envelopes of identical appearance.

The researcher responsible for the application of the MI technique and the one responsible for the conduct of conventional appointments will be blinded to the outcomes of the study; therefore, the application of structured questionnaires, scales, and assessment of other variables of the study will be carried out by a researcher unblinded to the outcomes.

Statistical analysis:

Continuous variables will be expressed as mean standard deviation or median and interquartile range (25 and 75 percentile). Categorical variables will be expressed in absolute and percentage numbers. Chi-square will be used for associations between sociodemographic and clinical variables with the scores of the Self-Care Scale. The comparison of the quantitative variables between groups will be conducted by the Student's t-test or Mann-Whitney test, according to data's distribution. The values of systolic blood pressure (SBP) and diastolic blood pressure (DBP) during the study, as well as the scores of the Self-Care Scale will be analyzed by the Generalized Estimating Equations (GEE) with Bonferroni correction. The pressure differences between both groups during the treatment will be analyzed by ANOVA test for repeated measurements. Analysis of Covariance will be conducted to adjust possible differences regarding the basal pressure. The 5% level of significance will be adopted and the data will be analyzed in the Statistical Package for the Social Sciences (SPSS) v.20 (Chicago, Illinois, USA).

Inclusion criteria

• Regular monitored in the hypertension outpatient clinic of HCPA for more than six months

Exclusion criteria

• Evident change in cognitive function, such as intellectual disability and dementia.