The High-Risk Bariatric Patient

Class

No. of points

Mortality rate (%)

0–1

0.31

2–3

1.90

4–5

7.56

One point assigned for each of the following: BMI > 50 kg/m², male gender, HTN, PE risk, Age >45 years

That same year, Buchwald and colleagues conducted a meta-analysis to evaluate a 30-day mortality based on type (gastric banding, gastroplasty, gastric bypass, or BPD/DS, or revisional surgery) and approach (laparoscopic vs open) of weight loss surgery [4]. They found significant differences in mortality between the various types and approaches to weight loss surgery (Table 2).

Table 2.

Thirty-day mortality for bariatric surgery by procedure

Surgery type	Death ≤30 days, mean (95 % CI)
Gastric banding
Open	0.18 (0.00–0.49)
Laparoscopic	0.06 (0.01–0.11)
Gastroplasty
Open	0.33 (0.15–0.51)
Laparoscopic	021 (0.00–0.48)
Gastric bypass
Open	0.44 (0.25–0.64)
Laparoscopic	0.16 (0.09–0.23)
Biliopancreatic diversion/duodenal switch
Open	0.76 (0.29–1.23)
Laparoscopic	1.11 (0.00–2.70)
Revisional surgery
Open	0.96 (0.09–1.82)
Laparoscopic	0.00 (0.00–1.47)

Adapted from Buchwald et al.

Given the evolving definition of the high-risk patient within the bariatric population, the American Heart Association sought to clarify at least the clinical work-up for such patients, thus giving further definition to the high-risk bariatric patient. The 2009 Science advisory from the American Heart Association delineated numerous obesity-related comorbidities that influence the preoperative cardiac assessment and ultimately the management of the severely obese patient. These risk factors included atherosclerotic cardiovascular disease, heart failure, systemic hypertension, pulmonary hypertension related to sleep apnea and obesity hypoventilation, cardiac arrhythmias, deep vein thrombosis, history of pulmonary embolism, and poor exercise capacity [1]. In addition to these factors, the AHA included data from the Women’s Health Initiative Observational Study suggesting that diabetes mellitus, elevated serum triglyceride levels, reduced serum high-density lipoprotein cholesterol levels, chronic inflammation, and prothrombotic state associated with obesity contribute to these patients’ overall cardiovascular risk. This science advisory also incorporated the Buchwald data in the discussion of assessing preoperative risk.

Additional studies have sought to evaluate other independent risk factors for morbidity and mortality after weight loss surgery. One of the more surprising significant risk factors for increased morbidity and mortality was published in Archives of Surgery in 2006 by Livingston [6]. He evaluated 25,428 patients having undergone bariatric surgery and found several factors that increased mortality with bariatric surgery: increasing age, male gender, electrolyte abnormalities, and congestive heart failure. He also found that the patients that had Medicare had greater disease burden and thus had higher morbidity.

Finally in 2011, Nguyen proposed a revised bariatric mortality risk classification system for patients undergoing bariatric surgery [7]. This updated, but more complicated, classification system encompassed those factors in DeMaria’s classification system and added other risk factors such as presence of diabetes, Medicare status, and type of operation and approach. The significance of this system is the acknowledgement of the differences in the risk profiles of the different types and approaches (open vs laparoscopic) to weight loss surgery.

By using these classification systems and the considerations presented by the American Heart Association, patients that have multiple risk factors can be identified early in the preparation period. They can then be medically optimized for a risk-appropriate weight loss surgery. These patients can more appropriately be counseled as to their increased risk for complications after surgery. However, using a multidisciplinary approach, the perioperative management can help effectively decrease overall morbidity and mortality.

Risk Factors

Age

It has been well demonstrated that advanced age increases postoperative morbidity and mortality for any surgery. Specifically in a study by Livingston in 2006 published in the Archives of Surgery, advanced age (≥65 years) was seen as an independent risk factor for adverse outcomes as defined as length of hospital stay >95th percentile, being discharged to a long-term care facility or having died during the hospital admission for weight loss surgery [6]. Interestingly, they found that there was steady increase in rate of adverse events as age increased. However, there was a sharp increase in rate of adverse events at age 60. Beyond the age of 65, there was a 32 % rate of adverse events and a 3.2 % mortality rate.

Nguyen et al. evaluated more than 105,000 patients between 2002 and 2009. They found that age greater than 60 was a significant factor for in-hospital mortality from the multiple logistic regression analysis [7].

Gender

There are several well-performed studies that demonstrate that male gender is an independent risk factor for perioperative complications after weight loss surgery. In fact when DeMaria was developing the Obesity Surgery Mortality Risk Score, his evaluation of the >2,000 gastric bypass patients demonstrated that male gender was an independent risk factor for mortality [2]. Livingston came to similar conclusions in his study in 2006 [6]. However, more recently (2011), Nguyen et al. suggested that even more than advanced age, male gender was associated with greater mortality after bariatric surgery [7]. Because of this, he gave male gender a greater contribution to his bariatric mortality risk classification.

Body Mass Index

Elevated weight or body mass index has been evaluated in many studies [8–10]. It seems intuitive that there would be a direct relationship between increasing BMI and risk of perioperative morbidity. Frequently as BMI increases, the physiology of the patient deteriorates. Patients with elevated BMIs typically have a higher incidence of cardiopulmonary insufficiency including right heart failure, pulmonary hypertension, obstructive sleep apnea, and obesity-related hypoventilation syndrome [8–10]. In addition to the physiologic consequences of morbid obesity, there are also mechanical challenges that these patients present. Their thickened abdominal wall, large liver, increased intraperitoneal fat, and limited working space after insufflation add to the technical difficulty of the procedure and may lengthen the duration of surgery [11, 12]. Acute presurgical weight loss may help ameliorate some of these technical difficulties and possibly decrease overall complications [13, 14]. All of these factors probably contribute to the fact that elevated BMI has been found in multiple studies, such as DeMaria’s evaluation of 2,075 gastric bypass patients, to be an independent risk factor for perioperative mortality especially in BMI >50 [2].

Thromboembolic Disease

Darvall et al. did an extensive review of the relationship between obesity and venous thrombosis [15]. Within this review which included a medline review and Cochrane data base search from 1966 to 2005, a number of mechanisms were identified which connected obesity and venous thrombotic events.

In fact, the adipose tissue itself acts as an endocrine, paracrine, and autocrine organ, regulating among other processes, vascular homeostasis. The substances that are secreted by the adipose tissue that are potentially involved with venous thrombosis include leptin, adiponectin, resistin, plasminogen activator inhibitor-1 (PAI-1), tissue factor, angiotensin II, and other substances of the renin-angiotensin system, non-esterified free fatty acids (NEFAs), tumor necrosis factor-a (TNF-a), transforming growth factor-b (TGF-b), and interleukin-6 (IL-6) [15].

Leptin has been found to potentiate the aggregation of platelets by enhancing ADP’s and thrombin’s pro-aggretory effect on platelets. It also increases the synthesis of C-reactive protein contributing to the chronic inflammatory state of obesity. Tissue factor, also secreted from adipose tissue, initiates the coagulation cascade when exposed to blood and bound to factor VIIa. Obese individuals demonstrate higher levels of TF-mediated coagulation. Finally IL-6, a proinflammatory cytokine, secreted from adipose tissue has direct effect on inflammation in the human body. IL-6 overproduction has been implicated in the pathogenesis for inflammatory conditions such as rheumatoid arthritis, Crohn’s disease, and juvenile idiopathic arthritis. Approximately one third of circulating IL-6 is produced from adipose tissue, and patients that are morbidly obese have higher circulating levels of IL-6. IL-6 inhibits gene expression and secretion of adiponectin, a powerful anti-inflammatory mediator. This may contribute to increased platelet aggregation and endothelial adhesion.

Furthermore, obese individuals have chronically elevated intra-abdominal pressure and decreased blood velocity in the common femoral vein resulting in venous stasis and ultimately contributing to increased risk for deep venous thrombus formation.

DeMaria recognized the elevated risk of these patients and included “PE risk” in his mortality risk score [2]. He found that the combination or presence of any of the following findings—previous VTE event, previous IVC filter placement, a history of right heart failure or pulmonary hypertension, history of physical findings of venous stasis including brawny edema or typical ulcerations—was highly statistically significant as a predictor of postoperative mortality. As such, he included “PE risk” in his mortality risk score system, underscoring the fact that pulmonary embolism is the leading cause of mortality in bariatric surgery centers, where the incidence of pulmonary embolism in patients who have undergone surgical procedures has been reported as high as 2 % [16].

Risk reduction strategies for decreasing thromboembolic events in patients that are at high risk include preoperative placement of vena cava filters, heparin windows, preoperative subcutaneous heparin administration, postoperative home administration of Lovenox, etc. In an analysis of the BOLD data base by Li, it was found that surgeons more typically put vena cava filters in patients with higher BMIs, that are African-American, who have had previous surgeries, who have prior history of venous thromboembolism, impaired functional status, lower extremity edema, obstructive sleep apnea, and pulmonary hypertension [17]. Interestingly, the patients that had the vena cava filters placed also had a higher incidence of DVTs and higher mortality rate. It is presumed that selection bias is responsible for the association between the filters and higher DVT/mortality rate. However, any decision to place a filter should consider the technical difficulty in placement and retrieval in the super-obese.

At our institution, Lovenox is typically given the day of surgery and a prophylaxis dose is given based on BMI. (BMI > 60 = 60 mg Lovenox BID; BMI <60 = Lovenox 40 mg BID). Also patients with a BMI >55 are given a prescription for home Lovenox for 2 weeks after hospital discharge for extended prophylaxis. Patients with previous DVT/PE, known hypercoagulable state, or other risk factors (immobility) are also given 2–4 weeks of extended prophylaxis after hospital discharge. However, the optimal strategy for prevention of venous thromboembolism in the setting of bariatric surgery is uncertain [18].

Obstructive Sleep Apnea

Obstructive sleep apnea is discussed in detail in Chap. 51. However, in relationship to risk assessment in the high-risk patient, many studies have demonstrated the association with obstructive sleep apnea and perioperative complications. Memtsoudis et al. performed a case control study that evaluated 58,358 orthopedic patients and 45,547 general surgery patients in the journal Anesthesia and Analgesia in 2011. They found that patients undergoing orthopedic and general surgeries were at statistically significant higher risk for aspiration pneumonia, reintubation, ARDS, and mechanical ventilation [19]. That same year in the journal CHEST, Kaw et al. performed a cohort study evaluating 471 patients undergoing noncardiac surgery within 3 years of polysomnography and found that these patients had higher risks of hypoxemia, transfer to the ICU, and an increased length of hospital stay [20].

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