CORRELATION BETWEEN NUTRITIONAL STATUS AND CLINICAL RESULTS IN PATIENTS UNDERGOING SPINAL SURGERY

Objetivo: Investigar a relacao entre os niveis de vitamina D e albumina pre-operatorios e qualidade de vida pos-operatoria em pacientes submetidos a cirurgia de coluna. Metodos: Pacientes submetidos a cirurgia de coluna nos niveis toracico e lombar foram avaliados por meio deste estudo prospectivo. Eles tiveram os niveis de vitamina D e albumina avaliado antes da cirurgia e a qualidade de vida medida atraves de dois questionarios: Oswestry Disability Index (ODI) e Scoliosis Research Society - 22 (SRS-22), um ano apos o procedimento. A ocorrencia de infeccao e o tempo de cicatrizacao foram coletados. Os valores nutricionais pre-operatorios e qualidade de vida dos pacientes foram analisados usando o teste de qui-quadrado e ANOVA para albumina e vitamina D, respectivamente. A relacao entre o status nutricional e o tempo de cicatrizacao e a ocorrencia de infeccao foram avaliados pelo coeficiente de Pearson. Resultados: 46 pacientes foram incluidos e seus valores nutricionais medios foram 19,1(6,6) ng/mL para vitamina D e 3,9(0,6) g/dL para albumina [media(desvio-padrao)]. Nao foi encontrada associacao entre os niveis de vitamina D e qualidade de vida dos pacientes medida pelos questionarios ODI (p=0,534) e SRS-22 (p=0,739). Tambem nao foi observada associacao entre niveis de albumina e qualidade de vida quando medida pelo questionario ODI (p=0,259) e SRS-22 (p=0,076). Nao foi encontrada correlacao entre o tempo de cicatrizacao ou ocorrencia de infeccao e valores nutricionais. Conclusao: Nao foi encontrada associacao entre os niveis de vitamina D e albumina e resultado cirurgico, interpretado pelos proprios pacientes, alem da ocorrencia de complicacoes com a ferida operatoria.


INTRODUCTION
The preoperative nutritional status of the individual is an important predictor of morbidity, complications, and overall surgical success. 1,2Albumin is the most abundant serum protein and preoperative hypoalbuminemia is a factor that is intimately related to perioperative morbidity and mortality since it affects the vascular diffusion of nutrients, which impacts the immunological system and the maintenance of homeostasis. 3,4itamin D is another important nutrient, fundamental to mineral homeostasis and bone metabolism.It regulates bone remodeling by stimulating formation and reabsorption. 5,6The active metabolite of vitamin D (1,25-(OH)2D) binds to an intracellular receptor called "vitamin D receptor" (VDR) that is distributed in various tissues of the human body.[10] However, to date there have been no studies conducted in Brazil that seek to confirm whether there is a relationship between the levels of serum albumin and vitamin D and the postoperative characteristics of patients who undergo surgical orthopedic procedures.Therefore, the objectives of this study were to confirm whether there is a relationship between the preoperative levels of serum albumin and vitamin D and the complication rates of healing, infection, and the quality of life of patients submitted to orthopedic spine surgery.

METHODS
This prospective study was approved by the Institutional Review Board (opinion no.1.283.577).
Subject Selection Patients who underwent spine surgery for different pathologies, including deformities, degenerative cervical and lumbar diseases, trauma, tumors, and infection between March 2014 and July 2015 were invited to participate in the study.It is, therefore, a study with a convenience sample.
To be included, the subject had to have serum albumin and vitamin D measured preoperatively, in addition to having consented to their participation by signing the Informed Consent Form.Patients with incomplete medical records and/or missing data were excluded.

Clinical Examination
Pre-and post-operative patient data were collected from an analysis of medical records and in medical consultations, respectively.
Preoperative Data: On the day of admission, a patient blood profile was collected, including serum albumin and vitamin D levels.The concentration of 25-hydroxyvitamin D (25OH-vitamin D) was measured using the Architect i2000SR instrument (Abbot Diagnostics, Lake Forest, IL, USA).Serum albumin was measured by photometric assay using the AU5800 system (Beckman Coulter Inc., Brea, CA, USA).
Using these values, the nutritional state of the patients was classified as follows: Vitamin D: 25OH-vitamin D levels below 30 ng/mL were considered insufficient and levels below 20 ng/mL were considered to be significantly deficient.
Albumin: albumin concentrations lower than 3.5 g/dL were considered hypoalbuminemia.
Postoperative Data: The surgical outcome was evaluated by the Oswestry Disability Index (ODI) 11 and Scoliosis Research Society-22 (SRS-22) 12 questionnaires, both validated in the Portuguese language, and pain intensity by the Visual Analog Scale (VAS). 13The presence of infection and the occurrence of complications of the surgical wound, such as delayed healing, were also considered.All the information was collected 12 months after surgery.

Statistical Analysis
The information collected was tabulated and analyzed using Stata 11 for Windows (StataCorp LP, College Station, TX, USA).
The normality of the data was tested using the Shapiro Wilk test.The correlation between the vitamin D and serum albumin levels and the quality of life following surgery, as well as the pain intensity reported by the patient and the occurrence of infection and surgical complications were confirmed by the Pearson correlation test.
In addition, the average differences between the variables were calculated by means of the unpaired Student's t-test and the associations by means of the Chi-Square test.A significance level of 5% was considered for all analyses.

RESULTS
Forty-six patients with an average age of 50 years (standard deviation 19 years) were included, 17 (37%) of whom were men and 29 (63%) of whom were women.Of the total, 58.7% underwent spine surgery for degenerative pathology, 19.6% for deformity, 8.7% for infection, 8.7% for fracture, and 4.4% for tumor.
The average preoperative level of vitamin D was 19.1 ± 6.6 ng/mL (average value ± standard deviation) and of albumin was 3.9 ± 0.6 ng/mL.
Table 1 shows the average values reported by the subjects included in the study for postoperative pain intensity and quality of life.The correlation between these variables and the level of vitamin D as measured by the ODI and SRS-22 questionnaires are shown in Table 2.The same is described for albumin in Table 3.
The average healing time was 18 days (standard deviation 14 days).The Pearson test showed no correlation between this variable and the albumin measurement (r=-1; p=0.359).
The rate of postoperative infection was 19.6%, corresponding to 9 patients.Deep infection was confirmed in 5 of them and superficial infection in the other 4. No correlation between postoperative infection and the quality of life was confirmed as measured by the ODI and SRS-22 questionnaires (Table 4).

DISCUSSION
The serum albumin level is one of the simplest and most used markers for evaluating the nutritional status of patients who will undergo surgery. 14Klein et al. 1 observed a significant increase in the rate of complications in malnourished patients (serum albumin <3.5 g/dL or total lymphocyte count <1500/mm 3 ) as compared to patients with results for these exams within the normal range.][17] Micronutrients also participate in the wound healing process.Amino acids and proteins, including albumin, are essential to tissue repair through neovascularization, fibroblast and collagen deposition, and the production of lymphocytes. 18,19Therefore, patients with preoperative hypoalbuminemia have a higher risk of complications related to the healing of the surgical wound. 1,3,15,20his study, however, found no significant correlation between preoperative hypoalbuminemia and the rates of postoperative infection or of complications in the wound-healing process.Some authors affirm that albumin should not be used as a standalone criterion for the nutritional assessment of patients, and that it should be associated with other nutritional indicators, such as anthropometry and body composition. 21,22This is due to their possible influence on the serum concentration of albumin, especially of changes in vascular permeability caused by the inflammatory process.Said situation generates a loss of albumin from the intravascular to the extravascular space and reduces their serum levels.Other factors that influence serum albumin concentration are prolonged half-life and the dilution effect caused by intravenous soultions. 21,23imilarly, no correlation was found between the vitamin D level and the quality of life and pain reported by patients submitted to spine surgery.In fact, the influence of vitamin D on these factors is not clear and needs more prospective studies, mainly due to the heterogeneity of the studies already conducted in terms of population, sample size, and result definition. 7pecifically in relation to quality of life, several recent studies have made their evaluations using the Short-Form 36 (SF-36) questionnaire and observed results similar to those described here. 24,25itham et al. 8 conducted a similar study in patients with heart failure with a questionnaire specific to the pathology and found that there was an improvement in the quality of life reported by patients who took vitamin D supplements.This study used the ODI and SRS-22 specific to patients with spine pathologies and validated for the Portuguese language.
The effect of vitamin D on pain reported by patients was evaluated in the elderly, post-menopausal women, and patients with diffuse musculoskeletal pain and osteoarthritis with concentrations of this hormone less than 20 ng/dL. 24,26These studies did not show any   difference in the intensity of pain in relation to the patient levels of vitamin D, which corroborates the findings in our study.Several limitations in the design of this study should be discussed, particularly regarding the sample characteristics.Because we used a small convenience sample, our results should be interpreted with caution and generalizations should be avoided.Additionally, the heterogeneity of the pathologies of the subjects included, even though all of them were operated on by the same medical team, is a limitation.On the other hand, this is the first study conducted with the Brazilian population.

CONCLUSION
In view of the above, we concluded that there was no relationship found between the preoperative levels of serum albumin and vitamin D and the rate of surgical wound complications or the surgical outcomes of patients submitted to orthopedic spine surgery.

Table 1 .
Average values for pain and quality of life from the questionnaires.

Table 2 .
Average values and correlation between the level of vitamin D and the intensity of postoperative pain and quality of life.

Table 3 .
Average values and correlation between the albumin level and the intensity of postoperative pain and quality of life.
VAS = visual analog scale for pain; r = Pearson correlation coefficient; SD = Standard deviation.

Table 4 .
Correlation values between the rate of infection and the intensity of postoperative pain and quality of life.