5 Perioperative Optimization in the Aging Population



10.1055/b-0040-177387

5 Perioperative Optimization in the Aging Population

Ade Olasunkanmi


Abstract


The aging patient is more likely to have a higher burden of comorbidities/multiorgan system disease, thereby presenting a unique challenge in achieving balance with therapies and intervention while maintaining functional independence. As a result, there is growing utilization of health care resources by this segment of the population, challenging the health care delivery system. While there is a higher morbidity in elderly patients, there is no proven significant difference in postoperative mortality or long-term survival between the aging patient and the other surgical groups. Important are new approaches to management, such as comprehensive preoperative assessment and optimization. This allows for maintenance of functional status (less likelihood of loss of functional independence), quality of life (less time in the hospital), and reduction of medical and surgical complications in older adults. 2





Key Points




  • Surgery can be safely performed in the aging patient



  • Comprehensive preoperative assessment is important for morbidity and mortality counseling



  • Frailty does not equal age, although it is common with aging



  • There are no strict criteria for withholding surgery in the aging patient



  • Modifiable risk factors can be anticipated and managed perioperatively to decrease perioperative complications




5.1 Background


People over 65 years of age are the fastest growing segment of the population due to increased life expectancy and decreased birth rates1, and there is a corresponding increase in the number of surgical procedures in this population of adults. 2 , 3 , 4 Older adults comprise over 40% of all surgical patients in the United States and account for a large proportion of health care costs. 5 Despite advances in surgical, anesthetic and medical management, the effects of aging places the older adult at risk of adverse postoperative outcomes 6 and prolonged recovery. 3 The high prevalence of comorbidities and decreased physiologic reserve have been implicated in poor postoperative outcomes. As a result, healthcare for older adults is a prominent concern as the aging population grows in number and complexity. Aging is associated with overall decline in reserves, making it more difficult to recover from a major stress. A poor functional recovery following a successful surgery may be even more devastating to an older patient. The propensity toward complications in the aging surgical population, coupled with the continued growth of the aging population requiring surgery has led to greater attention to perioperative identification of pre-existing comorbidities and other risk factors. 1 , 5


The aging patient is more likely to have a higher burden of comorbidities/multiorgan system disease, thereby presenting a unique challenge in achieving balance with therapies and intervention while maintaining functional independence. 1 Age bias is still evident in clinical practice because of the presumed higher mortality and morbidity rates associated with the older adult. However, several studies have suggested that medical comorbidities, which are more prevalent with age, are primarily responsible for the observed perioperative complications seen in this population. In addition, while there is a higher morbidity in aging patients, there is no proven significant difference in postoperative mortality or long-term survival between the population and the other surgical groups. 1 , 7 , 8 , 9 , 10 , 11 Emerging data increasingly suggests that preoperative comprehensive assessment and optimization reduce medical and surgical complications in older adults, such as reduction in the length of hospital stay and the likelihood of a loss of functional independence. 2 The following chapter will discuss elements of the comprehensive perioperative assessment of the aging patient and provide thresholds and interventions to consider for optimization.



5.2 Frailty


Frailty is a decrease in physiological reserves, resulting in diminished resiliency, loss of adaptive capacity, and increased vulnerability to stressors. 12 , 13 Frailty is the consequence of age-related defects that have accumulated in different physiological systems. 14 The concept of frailty denotes gradual loss of physical and mental function as well as vitality, regardless of coexisting disease. 13 It has been identified as an independent risk factor for mortality, morbidity, and increased length of stay and discharge to institutions other than the home in different surgical populations. 6 , 13 The prevalence of frailty in older adults is estimated at 9.9% and the prevalence of prefrailty of 44.2%. Frailty is also more common in women compared to men and increases with age. In aging patients undergoing surgery, the prevalence of frailty is higher, at 25 to 56%. 5


While there are competing models of frailty, its role as a predictor of postoperative adverse events following surgery is being recognized. 6 , 12 , 13 The two most accepted models of frailty are the frailty phenotype and frailty index (FI) (Table 5‑1). 6 In the frailty phenotype model, frailty is measured across a set of five criteria or domains; unintentional weight loss (> 10 pounds in the past year), self-reported exhaustion, gait speed, low physical activity level and grip strength. 6 , 12 A point is awarded for each criterion met by the patient and the total is computed. Patients identified as frail (3 or more points) should be considered for possible geriatric consult for further assessment and identification of needed interventions. The FI or deficit accumulation model is based on the number of accumulated deficits a patient accrues across a number of different domains: current illnesses/comorbidities, cognitive status, emotional, motivation, communication, strength, mobility, balance, elimination, nutrition, activities of daily living, sleep and social. 6 , 12 The index is the ratio of the number of deficits divided by the number of variables measured. The derived index can be compared to the frailty phenotype classification to determine frailty: FI </= 0.10 is considered “non-frail”, 0.1 < FI </= 0.2 is considered “vulnerable”, 0.21 < FI </= 0.45 is frail and FI > 0.45 is “most frail”. 15 While the frailty index allows for the identification of domains needing intervention during the perioperative period, the process can be very time-consuming and often requires a geriatric consult. 12













































Table 5.1 Frailty measurement according to the “Fried” criteria (Adapted from Alvarez-Nebreda et. al. 12 )

Characteristic of fragility


Measurement


Shrinking


>10 pounds unintentional weight loss in last year


Weakness


Grip strength: lowest 20%


By gender/BMI, using a hand dynamometer


Exhaustion


Self-report exhaustion during last week


Identified by two questions from the CES-D scale


Slowness


Walking time for 15 feet: slowest 20%


By gender/height


Low activity


Kcal/week: lowest 20%


By gender: men < 383 kcal/week; women < 270 kcal/week, using the Minnesota Leisure Time Physical Activity Questionnaire


BMI: Body Mass Index


CES-D: Center for Epidemiological Studies- Depression scale


Scoring: ≥ 3 criteria = positive for fragility phenotype; 1–2 criteria = intermediate or prefrail


Fatigue


Are you fatigued? (yes = 1 point)


Resistance


Can you walk up one flight of stairs? (no = 1 point)


Aerobic


Can you walk more than a block? (no = 1 point)


Illnesses


Do you have more than five illnesses? (yes = 1 point)


Loss of weight


Have you lost more than 5% of your weight in the past 6 months? (yes= 1 point)


Scoring > 3 points = frail, 1–2 points = prefrail, 0 points= robust



Frailty screening should be undertaken only if it will influence the management of the patient, with the goal of preoperative risk stratification and identifying potentially modifiable factors that can be optimized prior to surgery. There are several tools that can be used for the measurement of frailty. The FRAIL scale, proposed by The Geriatric Advisory Panel of the International Academy of Nutrition and Aging, 16 is used for the screening of frailty; it is based on the frailty phenotype model and includes five features, each worth one point (described above). Other tools include the Risk Analysis Index (RAI), the Edmonton Frail Scale, the modified Frailty Index, and the Clinical Frailty Scale, all based on the FI model. The choice of tool selected for screening should take into consideration the clinical/health care setting, the demands and limitations of the institution, the composition of the multidisciplinary team, the patient population seen, and the goal of the intervention. 12



5.3 Diabetes


Diabetes mellitus (DM) is a very common chronic disease with a long course and serious systemic implications. 17 The incidence of DM has been increasing rapidly, and it is estimated that over 29 million Americans have a confirmed diagnosis of DM. 18 There are many factors contributing to the rise of this epidemic, including a high prevalence of obesity, unhealthy diet, a sedentary lifestyle, improved or changes to diagnostic criteria, and increase in life expectancy resulting in an aging population. 17 Diabetes is a significant risk factor for complications following surgery, including pneumonia, surgical site infection, 30-day postoperative mortality and morbidity, cardiovascular adverse events, delayed discharge, and hospital readmission. 17 , 18 , 19 , 20 The long-term mortality and high incidence of surgical site infections and cardiovascular complications in the diabetic population represent an increasing medical and socio-economic burden on the health delivery system and society. 21 The poorer outcomes observed in patients with DM are partly due to the higher rates of comorbidities, such as silent ischemic heart disease, renal impairment, and hypertension. 19 The risk of mortality in diabetic patients is related to the length of time the patient has had DM, optimal glycemic control at the time of hospital admission, and the glycosylated hemoglobin (HbA1c). The presence of poorly controlled diabetes and elevated levels of HbA1c have been implicated in the risk of worse perioperative outcomes. 22 The negative consequence of poor glycemic control is due to the production of advanced glycation end products (AGEs), which results from glycosylation of proteins. Higher levels of AGEs have been linked to development of both fatal and nonfatal cardiovascular disease from rapidly progressive atherosclerosis, resulting from accumulation of glycosylated proteins in the vessel walls. Dysglycemia, encompassing hypoglycemia, hyperglycemia, stress-induced hyperglycemia, and excessive glucose variability (all of which can be associated with poorly controlled blood glucose) has been associated with even poorer postoperative outcomes. 19 Several studies have linked poor glycemic control to impaired function of lymphocytes, decreased phagocytosis, impaired bacterial killing, and impaired chemotaxis, leading to the observed increased risk of postoperative surgical site infection seen in diabetics. 22 Furthermore, surgery and anesthetics have profound effects on glucose level and in the setting of pre-existing poorly controlled diabetes can lead to postoperative complications. Surgery and anesthetics lead to the release of a host of hormones, such as glucagon, growth hormone, adrenaline and noradrenaline. The combination of cytokine release and increased counter-regulatory hormones raises glucose levels and increases insulin resistance. This combination can lead to dangerous and significant hyperglycemia in diabetic patients with poorly controlled glucose, contributing to poor postoperative outcomes. 19


Long-term glycemic control is monitored using HbA1c. HbA1c reflects an individual’s mean blood glucose level over the previous 2 to 3 months and represents the amount of glucose that sticks to the red blood cells. The International Expert Committee Report recommends glycemic control with a goal of HbA1c < 7.0%, and this has been associated with reduced micro- and macrovascular risk. However, it is very difficult to apply the same goal to a broad group of patients. 22 In the 2008 study by Walid et. al 17 , HbA1c greater than 6.1% was associated with increased length of stay and overall cost, from health care resource utilization perspective, among patients undergoing anterior cervical discectomy and fusion and lumbar decompression and fusion. Hikata et. al 23 evaluated postoperative surgical site infection in diabetic patients following posterior thoracolumbar surgery and reported increased or high risk, with HbA1c > 7.0%. They recommended lowering HbA1c to < 7.0% prior to surgery to decrease the risk of postoperative surgical site infection. However, the study was insufficiently powered to support the conclusion. A subsequent study by Canciennne et. al 24 looked at 5,000 patients undergoing single-level lumbar decompression with the goal of identifying the HbA1c threshold level above which the postoperative risk of infection increased significantly. Patients were divided into groups based on their HbA1c level by increments of 0.5 mg/dL. The risk of deep postoperative surgical site infection increased with increase in perioperative HbA1c level. Using a receiver operating characteristic (ROC) curve and multivariate analyses, it determined that perioperative HbA1c above 7.5 mg/dL could serve as the threshold correlating with significantly increased risk of surgical site infection following surgery, with odds ratio 2.9, compared to patients with HbA1c < 7.5 mg/dL (95% CI, p < 0.0001). 8



5.4 Osteoporosis


Osteoporosis presents a unique challenge because it may be associated with fusion failure, iatrogenic instability and fracture following surgery. It is more common with advancing age due to progressive bone loss throughout the adult life. The prevalence of osteoporosis is expected to increase with increasing life expectancy. 25 Older adults are rarely assessed and treated for osteoporosis and low bone mineral density (BMD) despite the high prevalence of this chronic disease and the serious consequences. 26 , 27 Osteoporosis leads to reduced bone mass and deterioration in the bone microarchitecture, predisposing older adults to fragility fractures and debilitating spinal deformities. 27 The yearly incidence of osteoporotic fractures in the United States exceeds that of new-onset diabetes, coronary artery disease, stroke, heart failure, and breast cancer. 26 Fractures among older adults have been linked to greater mortality, increased requirement for long-term care and significant deterioration in quality of life. Given the high prevalence of osteoporosis in older adults, the clinical problem it presents and the significant impact it has on the quality of life and mortality, it is essential to identify osteoporosis (or osteopenia) prior to elective surgery and to initiate treatment to reduce the risk of postoperative complications and to ensure successful surgical outcome. 26 , 27 According to the World Health Organization (WHO), all perimenopausal and postmenopausal women as well as patients with known metabolic bone disease or a high number of risk factors should undergo BMD screening with dual-energy X-ray absorptiometry (DEXA) and metabolic laboratory evaluation. 27 The FRAX fracture-risk assessment tool, developed by the WHO, can help identify patients who would benefit from therapy despite not being classified as having osteoporosis. 27 , 28 FRAX weighs the influence of several risk factors to quantify fracture risk. Measurement of Hounsfield units (HU) on CT of the lumbar spine has been shown to correlate with BMD and can therefore be used as a screening and diagnostic tool for osteoporosis. 29 Using the neck of the femur for the measurement of HU is more reliable than using a degenerative segment in the lumbar spine, which could yield a false negative measurement. Identification or recognition of osteoporosis or risk factors is important so that appropriate referral for preventative strategies can be undertaken. Medical therapy can include pharmacologic agents such as antiresorptive agents that reduce bone loss or anabolic agents that increase bone formation. FDA approved antiresorptive agents include bisphosphonate (alendronate, risedronate, ibandronate and zoledronic acid), calcitonin, and raloxifene. Teriparatide is the only anabolic agent that is FDA approved for the treatment of osteoporosis. It is effective in treating vertebral fractures and is well tolerated. Ohtori et. al 30 in 2013 compared teriparatide and bisphosphonate for treatment of osteoporosis in postmenopausal women undergoing spinal fusion and reported both faster and greater rates of fusion in the teriparatide group. Inoue et. al 31 reported increase in the insertional torque of pedicle screws during spinal fusion with at least 1 month of treatment prior to surgery. Ohtori et al(2015) 32 reported a more effective bony fusion with more than 6 months of treatment with teriparatide, compared to shorter duration of teriparatide or treatment with bisphosphonate.



5.5 Cardiovascular


Cardiovascular disease in older Americans represents a huge burden in terms of health care costs, functional decline, functional disability and morbidity and mortality. 33 High-risk surgical procedures in patients with active cardiac conditions, who have poor exercise tolerance, are associated with very poor perioperative outcomes. It is therefore critical to identify pre-existing cardiac disease, and if present, have it evaluated and treated prior to nonemergent noncardiac procedures. 25


Perioperative mortality and morbidity from coronary artery disease are common complications following noncardiac surgery, especially in the aging patient. The incidence of cardiac morbidity after surgery depends on the definition and ranges used to measure the morbidity; this can range from elevated cardiac biomarkers (e.g., troponin) to more serious complications such as myocardial infarction, cardiac arrest/serious arrhythmias, and acute heart failure. 34 , 35 Devereaux et. al 36 reported a 1.9% 30-day mortality in a cohort of patients >= 50 years of age who underwent noncardiac surgery and had elevated troponin levels. In addition to the mortality risk, postoperative cardiac complications lead to prolonged hospital stay, increase in illness burden, and reduction in long-term survival. 34 Age is an important consideration in the risk of major adverse cardiac event after a noncardiac surgery, due to the growing prevalence of cardiovascular disease in adults age 55 or older. 33 , 37


The American College of Cardiology/American Heart Association (ACC/AHA) Practice Guidelines 38 recommend the use of a validated risk-prediction tool to predict the risk of perioperative major adverse cardiac event in patients undergoing nonemergent noncardiac surgery. Risk assessment of patients should include integration of clinical risk factors, functional capacity assessment, and the type of surgery. More complex patients may need a formal detailed assessment by a cardiologist or hospitalist. 34 The American Society of Anaesthesiologists (ASA) and the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) Surgical Risk Calculator (described below) are useful tools for preoperative assessment and risk stratification. The Revised Cardiac Risk Index (RCRI) is a simple, validated and accepted multivariate predictive tool for assessing perioperative risk of major cardiac complications, such as myocardial infarction, pulmonary edema, ventricular fibrillation, or primary cardiac arrest or complete heart block. 34 , 38 Each of the clinical variables contributes 1 point, with scores of 0, 1, 2 and >= 3 points, corresponding to estimated risks of major cardiac complications of 0.4%, 0.9%, 7%, and 11%, respectively. An RCRI score of 0 implies the patient is low risk, a score of 1 or 2 suggests intermediate risk, and high-risk patients have a score of 3 or higher. The RCRI discriminates well between high- and low-risk patients, but it does not account for age or hypertension, both of which are important factors in perioperative risk assessment. 34 Exercise tolerance or functional status is another important factor that can be an important predictor of perioperative outcome. Poor or low exercise tolerance is associated with poor perioperative outcomes. 25 , 39 Older adults with poor exercise intolerance have been shown to have more cardiovascular and pulmonary complications. 39 A useful tool for assessing exercise tolerance is the Duke Activity Status Index (DASI). It is a structured questionnaire that grades exercise ability on the basis of questions that are related to exercise equivalences. 25 The 12-item scale was developed to correlate with peak oxygen uptake, and the response to each question in the questionnaire is weighted, with higher scores indicating higher functional status (Max score 58.2). 40 The ACC/AHA guidelines recommend using the metabolic equivalent of task (MET), which is a derivative of the DASI questionnaire, with 4 METs given as the cut-off value for acceptable functional capacity (Table 5‑2). 25 , 38









































Table 5.2 Metabolic Equivalent of Task (MET) (Adapted from Fleisher LA et. al 38 )

Physical activity


Light intensity activities (<3 METs)


Sleeping


Watching television


Writing, desk work, typing


Walking, level ground, strolling, very slow


Moderate intensity activities (3–6 METs)


Bicycling, stationary, very light effort


Walking, briskly


Mowing lawn


Sexual activity


Vigorous intensity activities (>6 METs)


Jogging (6 mph), hiking


Soccer, basketball game


Running, in place


Rope jumping


Swimming




5.6 Pulmonary


Postoperative pulmonary complications due to pulmonary disease, such as obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD), are increasingly being recognized as important causes of medical morbidity and mortality. Both OSA and COPD are independent risk factors for major cardiopulmonary events that can complicate functional capacity. The reported incidence of postoperative pulmonary complications varies widely in the literature, from 2% to 19%, and approximately 10% to 30% of patients who undergo general anesthesia experience postoperative pulmonary event, ranging from minor to major complications. In addition, up to 90% of patients experience some degree of atelectasis during anesthesia due to positioning and loss of functional residual capacity. 41 OSA is a common chronic condition characterized by frequent episodes of upper airway collapse during sleep. It can lead to derangements in gas exchange and can affect nocturnal sleep quality and lead to daytime fatigue. OSA is being recognized as an independent risk factor for the development of systemic hypertension, cardiovascular disease, stroke and abnormal glucose metabolism. 42 , 43 The prevalence of OSA is estimated at between 3% to 7%, variably affecting the population with some subgroups at higher risk. Age (>= 60), among several other factors, increase the vulnerability for the disorder and postoperative pulmonary complication. 41 The majority of people affected remain undiagnosed, despite the increasingly apparent clinical consequences. 42 OSA and COPD are primarily diseases of middle- and older aged adults, who are the most likely to require surgical procedures. Due to the potentially serious complications associated with untreated OSA, it is important to screen for and recognize the disorder and plan appropriate therapy prior to nonemergent/elective surgery to reduce postoperative cardiorespiratory events, which can be twice as common in this population. 34 Smoking cessation and pulmonary rehabilitation are important preoperative strategies that can help improve both short- and long-term outcomes. 41


A number of screening tests have been developed to identify high risk patients, but the STOP and STOP-Bang questionnaires are convenient and easy to use and can be helpful in this regard. These questionnaires are acronyms: thesnoring, tiredness, observed apnea, high BP (STOP) and snoring, tiredness, observed apnea, high BPBMI, age, neck circumference and gender (STOP-Bang) are concise, user-friendly screening tools for OSA that can be used in the outpatient setting. 41 , 43 The STOP questionnaire has moderate sensitivity (65.6%) and specificity (60%) in detecting OSA. It has a higher sensitivity but lower specificity in detecting moderate and severe OSA (74% and 53%; 80% and 49%, respectively). 43 Because of the relative ease of use, efficiency and high sensitivity, the STOP-Bang questionnaire is currently widely used and has been well validated. It has additional four questions (body mass index – BMI > 35, age > 50, neck circumference > 40 cm, gender = male) in addition to the STOP questions. Each question counts for one point with a “yes” response, for a possible total score of 8 points. The STOP-Bang questionnaire has very high sensitivity (100% for detecting severe OSA and 93% for moderate OSA). 41 , 43 Patients with a score of 0 to 2 on the questionnaire are considered to be at low risk of OSA. Several studies have shown that patients identified as being at high risk of OSA have higher rates of postoperative complications, such as unplanned reintubation and myocardial infarction. 43 Patients at high risk for OSA on the STOP or STOP-Bang questionnaire should be considered for further evaluation for OSA and interventions such as CPAP prior to proceeding with elective surgical interventions.



5.7 Kidney Disease


Kidney disease is a spectrum of diseases, including acute kidney disease (AKI, chronic kidney disease (CKD) and end-stage renal disease (ESRD), and is a chronic and progressive process with far-ranging consequences on postoperative outcome. 44 , 45 CKD is a public health problem, with a rising incidence and prevalence of kidney failure. 46 The U.S. Renal Data System estimates that a patient with CKD is 3 times more likely to be hospitalized. 44 The life expectancy of patients with kidney disease has been increasing, with an increasing number undergoing spine surgery 47 and there has been several studies evaluating the impact of the disease on the postoperative outcome. Patients with CKD have higher rates of myocardial infarction, pneumonia, bleeding, septicemia, morbidity, and mortality 44 , 45 , 48 as well as a higher rate of 30-day readmission. 49 , 50 Also, CKD is important to the spine surgeon because of the osseous manifestations of severe renal dysfunction, such as bone loss, anemia, hypertension, and atherosclerotic disease. 44 , 46 In addition, CKD patients have poorer quality of life, with a higher burden of pre-existing comorbidities, including diabetes, hypertension, dyslipidemia, bone loss, neuropathy cardiovascular disease, and poor quality of life. 44 The goal of preoperative evaluation is to reduce the morbidity and mortality in renal disease patients undergoing surgery. Renal function is assessed by the glomerular filtration rate (GFR) or serum creatinine levels, and several studies have shown an increase in 30-day complications as the GFR decreases below 80 ml/min/1.73 m2. Consistent with the recommendation from the National Kidney Foundation, Purvis et. al 46 noted an estimated GFR of 60 ml/min/1.73 m2 to be the threshold value of a significant increase in morbidity. Serum creatinine levels can also be used as a complimentary test to assess preoperative kidney function and predict perioperative complications. 46 A creatinine level of greater than 1 ml/dL has been identified as an independent risk factor for postoperative myocardial infarction, 51 while levels greater than 2.0 mg/dL are associated with development of deep venous thrombosis. 52 Although preoperative kidney disease cannot be alleviated prior to surgery, understanding the increased postoperative complication risks and increased morbidity and mortality can inform the surgeon’s conversation with the patient. 46 Importantly, in order to decrease the postoperative complications, intraoperative and postoperative management strategies can be developed to manage fluid status/fluid shifts and blood pressure. 44 , 45 , 46



5.8 Nutrition


Nutritional deficiency in older adults can be due to a decrease in appetite, nutritional intake, and/or decreased gut absorption. 53 Malnutrition leads to lower immune response. Muscle atrophy and decreased wound healing then occurs 54 ; therefore, optimization of nutritional status in older adults undergoing surgery is important to decrease complications and improve surgical outcomes. 53 Poor nutritional status has an adverse effect on postoperative outcome and is very prevalent with many disease processes as well as other comorbidities. It is an independent risk factor for postoperative complications and increased hospital stay and cost. 53 , 55 Elective spine surgery is risky in the older adult, given the overall burden of comorbid diseases, and the presence of nutritional deficiency/malnutrition greatly increases overall adverse outcomes. Patients should be screened with adequate history of weight loss/weight gain, muscle gain or loss, oral intake, and BMI, as well as for chronic or acute disease states. 53


Various scoring and assessment tools exist for screening for nutritional deficiency. The Mini Nutritional Assessment (MNA) tool is the most widely used validated tool for nutritional screening and assessment because of how easy it is to use and its feasibility in a clinical setting. 56 The MNA has four parts: anthropometric measurements, general status, diet information, and subjective assessment, with a maximum score of 30 points. A score of < 17 points is regarded as an indication of malnutrition, 17 to 23.5 points indicate a risk for malnutrition, and a score > 23.5 points indicates that the patient is well nourished. 56 Albumin could be used to determine a patient’s nutritional health status prior to surgery, and the role of prealbumin is still being evaluated as a predictor of surgical outcome. Normal values of prealbumin are in the range 16 to 40 mg/dL, and values less than 16 mg/dL are considered to indicate malnutrition. 53 Laboratory tests, such as a lymphocyte count, serum albumin, and prealbumin could offer a high predictive value when combined with a nutrition screening tool such as the MNA. A total lymphocyte count of less than 1,500 cells/mm3, transferring levels less than 200 mg/dL, body mass index (BMI) less than 18.5 Kg/m2, and albumin levels less than 3.5 g/dL are all indicators of malnutrition. 53 , 57


In malnourished patients, a referral to a nutritionist prior to proceeding with elective surgery should be considered. Various Enhanced Recovery After Surgery (ERAS) pathways have also proposed several steps aimed at reducing postoperative complications related to malnutrition, including permitting solid intake up to 6 hours before surgery and clear intake up to 2 hours before surgery; oral carbohydrate loading to reduce the body’s catabolic effect from the stress response to surgery; early postoperative nutrition/feeding; and optimizing social circumstances. 53 , 55 , 58



5.9 Body Mass Index (BMI)


The worldwide population is gaining weight. This trend is expected to grow, with four out of 10 adults already classified as overweight or obese in 2013. 59 Obesity is particularly prevalent in the United States, with 31.7% of adult men and 33.9% of adult women classified as obese. It is an independent risk factor for comorbidities such as hypertension, diabetes and cardiovascular disease, as well as a contributor to the development of low back pain and increased rates of degenerative spine pathologies. 60 Complications correlated to obesity include longer incision, increased blood loss, increased surgery duration, SSI, and venous/pulmonary thromboembolisms. 59 , 61 , 62 , 63 Adult spinal deformity is very common, and the incidence increases with age, with reported prevalence of up to 68% in patients over the age of 65 years. Surgery for the treatment of adult spinal deformity to relieve pain and disability is complicated by the high rates of postoperative complications due to several factors, including obesity. 59 , 60 , 61 Several studies have investigated the role of obesity on postoperative complications following surgery with varying findings, partly due to the discrepancy in inclusion criteria, type of procedure and the obesity threshold used. 59 , 61 Primarily, the disparities arise from nonstratification of the patients based on obesity class. 60 The Centers for Disease Control defined obesity as BMI greater than or equal to 30 Kg/m2. 64 Based on several studies, when all other covariates are held constant and healthy weight patients (BMI < 25 Kg/m2) are compared to other BMI groupings (overweight – 25–29, class 1 obese – 30–34, class 2 obese – 35–39 and class 3 obese – 40+), the BMI threshold for significantly increased risk of postoperative complications was found to be BMI > 40 Kg/m2. The patients with BMI > 40 Kg/m2, were found to be at significantly higher risk for longer operative time, increased blood loss, higher risk of readmission/reoperation, higher rates of SSI, and greater odds of DVT, 60 , 61 , 62 , 63 suggesting that this subgroup of obese patients may bear the burden of the increased medical costs and poor outcomes following surgery. 61

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