Preoperative Malnutrition in Spine Surgery

With the increasing proportion of elderly individuals in the population and associated comorbidities, there has been increased awareness among spine surgeons in patient selection and perioperative management of modifiable risk factors. One such factor, preoperative malnutrition, has been estimated to have a prevalence as high as 50% in patients undergoing spine surgery.[1-4] Additionally, preoperative malnutrition has been associated with adverse outcomes including wound complications, surgical site infections, pseudoarthrosis, increased length of hospital stay and unplanned readmissions.[1,2,5-10] Standardized nutritional scoring systems and laboratory testing are essential to assess adequate nutritional status.[9,11-14] In patients with malnutrition, appropriate perioperative nutritional support and diet management should be employed to optimize surgical outcomes.

Pathophysiology and Etiology

According to the World Health Organization, malnutrition refers to deficiencies as well as excesses of nutrition related to obesity and diet-related noncommunicable diseases (heart disease, stroke, and diabetes).15 These conditions are associated with altered metabolism, chronic inflammation, gut dysfunction, and deficiencies of vital micronutrients.[16-18] Additionally, as immune cells do not possess significant energy stores, they are heavily reliant on uptake of nutrients from the environment to function appropriately.[19,20] As a result, malnutrition leads to the inhibition of regulatory T-cell proliferation leading to decreased cytokine production, therefore limiting the ability to mount an immune response and prevent infections.[19,20] Two conditions closely associated with malnutrition—diabetes and obesity—have rapidly risen in the Unites States, with an estimated prevalence >30%. [21,22] Consequently, there has been a corresponding increase in the number of these patients undergoing spine surgery, as both conditions are associated with the development of degenerative diseases.[22] Furthermore, many nutritional deficiencies are secondary to diseases related to decreased appetite, gut absorption, and metabolic imbalances including psychiatric disorders, inflammatory bowel disease, and neoplastic processes.[11,23] Often, the etiology of malnutrition is multifaceted in nature and requires a comprehensive evaluation by clinicians.

Diagnosis and Evaluation

Preoperative evaluation of a patient’s nutritional status should begin with an appropriate history and physical examination to assess any dramatic weight changes, muscle loss or gain, nutritional intake level, BMI, and associated acute or chronic diseases.[11,12,14] Anthropometric measurements are commonly used in the literature to indicate undernutrition. In men, a calf muscle circumference of less than 31 cm and an arm muscle circumference of less than 22 cm are considered signs of undernutrition. Additionally, a measurement below 60% of the standard circumference for a given sex suggests severe malnutrition.[24,25]

However, laboratory testing has been more substantiated in the literature to diagnose malnutrition, with the most common definitions as follows: serum total lymphocyte <1,500/mm3 and serum albumin concentration <3.5 g/dL.[26-28] Low serum prealbumin <20 mg/dL and serum transferrin levels <200 mg/dL have been similarly described.[5,14,29,30] Albumin, prealbumin and transferrin are visceral proteins that are sensitive indicators of any nutritional changes. Although albumin, with a half-life of 20 days, has traditionally been regarded as the standard for assessing nutritional status, its levels can fluctuate in patients with renal disease, leading to variability in its accuracy.[5] In contrast, prealbumin is produced predominantly in the liver and detects acute changes of protein/ caloric nutrition with a half-life of 1.9 days.[5] Additionally, vitamin levels in high-risk patients and hemoglobin A1c in diabetic patients should be obtained to assess the severity of the respective diseases. Lastly, standardized screening tools are used to define malnutrition. The Rainey-MacDonald Nutritional Index (RMNI) is often employed and calculated as follows:

RMNI = (1.2 x serum albumin) + (0.013 x serum transferrin) – 6.43

A zero or negative value suggests malnutrition.[31,32] Various additional scoring systems and questionnaires are available, including the Nutritional Risk Score and Mini Nutritional Assessment.[33,34]

Malnutrition Outcomes in Spine Surgery

Adverse outcomes in the setting of spine surgery in patients with malnutrition is well-reported in the literature. Bohl et al performed a retrospective review of data collected by the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP), which included 4,310 patients undergoing posterior lumbar spine fusion to investigate an association between preoperative hypoalbuminemia (as defined as <3.5 g/dL) and complications. The study found that patients with hypoalbuminemia have a higher risk of wound dehiscence (1.5% vs 0.2%, p = 0.006), surgical site infections (5.4% vs 1.7%, p = 0.010), urinary tract infections (5.4% vs 1.5%, p = 0.005), and 30-day unplanned admissions (11.7% vs 5.4%, p < 0.001).[7] Furthermore, the study noted that the prevalence of hypoalbuminemia was closely associated with increasing age, insulin-dependent diabetes, and BMI.[7]

Puvanesarajah et al conducted a retrospective review of Medicare data from 2005 to 2012, which included 148,238 patients undergoing elective 1- or 2-level posterior lumbar fusion.[8] The study noted similar results, as preoperative malnutrition was found to be predictive of increased infection rates, wound dehiscence, LOS, and 30-day readmissions.[8] Similar adverse outcomes have been noted in additional studies, including in patients undergoing other types of spine surgery, such as anterior cervical discectomy and fusions (ACDFs) and adult spinal deformity corrections.[1,2,5,6,9,10] These adverse events are associated with increased healthcare costs. Blumberg et al found that for every decrease in albumin by 1 g/dL, there was an approximately $8,081 increase in treatment cost and a 3.7 day increase in length of stay.[35]

Optimization and Treatment

In 2021, the Enhanced Recovery After Surgery (ERAS) Society provided a strong recommendation in favor of a preoperative nutritional assessment and supplementation in patients undergoing elective spine surgery.[13] While there remains a paucity of literature evaluating whether modifying or optimizing preoperative nutritional status results in improved clinical outcomes, recent studies have supported this claim. Saleh et al conducted a randomized controlled trial in 103 patients undergoing lumbar spine surgery.[36] The intervention group received nutritional supplementation (protein shake) twice daily from postoperative day 0 to 2 weeks postdischarge while the control group was instructed to continue regular diets. Subgroup analysis of malnourished patients (defined as preoperative albumin <3.5 g/dL) who received protein shakes had lower rates of minor complications during admission (0.0% vs. 34.4%, p = 0.01) and lower rates of return to the operating room within 90 days (0.0% vs. 12.4%, p = 0.04).[36]

Liquid oral nutritional supplements (ONS) are preferred to solids due to faster gastric emptying and therefore less impact on the caloric intake of actual meals.[14] In literature outside the realm of spine surgery, a meta-analysis of 24 trials, including 2,387 adults, showed that ONS reduced overall mortality, particularly in undernourished elderly patients.[37] Other studies have found positive effects of ONS on body weight, energy/protein intake, and functional status.[38,39]

Based on the current evidence, if a patient is found to be malnourished, an informed discussion with the patient regarding potentially delaying elective surgery until the nutritional status is optimized is warranted. While additional research is needed to assess whether improving nutritional status improves outcomes following spine surgery, addressing malnutrition preoperatively remains a reasonable approach to potentially reduce the risk of complications.

Conclusion

Given the high prevalence of malnutrition in our population, careful attention must be placed to assess patients’ nutritional status prior to surgery. Multiple tools, including laboratory tests and nutritional scoring systems, may be employed by spine surgeons in the diagnostic evaluation of these patients. In prioritizing nutrition in our patients, potential postoperative complications may be avoided. When malnutrition is detected, nutritional counseling should be administered, consisting of dietary advice, meal fortification and oral nutritional supplements in the preoperative setting.

References

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Contributor:

Gregory Lopez, MD

Neil Mohile, MD

From DISC Sports and Spine Center in Newport Beach, California.