Michael Y. Wang, Andrew A. Sama and Juan S. Uribe (eds.)Lateral Access Minimally Invasive Spine Surgery10.1007/978-3-319-28320-3_35

35. Ileus and Gastrointestinal Complications

Evan D. Sheha¹, Grant D. Shifflett¹ and Russel C. Huang²

(1)

Department of Orthopaedic Surgery, Hospital for Special Surgery/Weill-Cornell Medical Center, New York, NY 10021, USA

(2)

Hospital for Special Surgery, Spinal Surgery Clinic, New York, NY, USA

Russel C. Huang

Email: huangr@hss.edu

35.1 Definition of Ileus

Postoperative ileus (POI) is a pattern of bowel dysmotility following surgery characterized by delayed transit and the accumulation of stool, gas, and fluid secondary to a decrease in coordinated peristalsis. Historically, the term has been used to describe both the mechanical and functional loss of peristalsis, though in more recent parlance, the word is used to describe an expected physiologic response of the GI tract leading to accumulation of normal secretions in the postsurgical patient [1]. It should be stressed that decreased gastrointestinal motility is a normal and expected physiologic consequence of major surgery, especially surgery involving bowel manipulation and/or general anesthesia. Typically, intestinal motility returns within hours of surgery and colonic motility within 1–2 days postoperatively [2]. While the exact timing and clinical parameters which define a true ileus are ill-defined, postoperative ileus is considered pathologic when prolonged and in the opinion of the authors may be defined as a failure of return of bowel function by postoperative day 3 [3].

35.2 Mechanisms of Postoperative Ileus

The vast majority of literature investigating postoperative ileus has been performed in the patient population undergoing intra-abdominal surgery as the effects of ileus are most profound following bowel manipulation. However, centrally mediated mechanisms and the effects of postoperative opioids on bowel motility can, in part, help to explain the incidence of ileus following posterior spinal surgery and lateral lumbar fusion – as well as other orthopedic procedures that do not involve significant bowel manipulation such as total joint arthroplasty [4].

35.2.1 Neural

Manipulation of the bowel following abdominal surgery or the approach to the anterior lumbar spine results in the activation of splanchnic nerves, an increase in sympathetic tone, and a resultant bowel hypomotility [5]. In addition to contributions from the sympathetic visceral nerves, abdominal skin incision and bowel manipulation have been shown to stimulate adrenergic inhibition in the gut [6]. Central mechanisms inhibiting gastric motility are moderated by corticotrophin-releasing factor (CRH) which is released from central structures – the hypothalamus, pons, and medulla – after bowel manipulation where it serves in turn to stimulate sympathetic preganglionic neurons [7]. Additional neuromuscular inhibitors have been investigated as possible contributors to POI including norepinephrine, nitric oxide, the secretin family of peptide hormones, and endogenous opioids [8]. It is accepted that no single mechanism is causative in the development of POI, and the overlap between these causes complicates the treatment and understanding of POI; however, the neurogenic mechanism is generally recognized as the greatest contributor to early postoperative ileus. Moreover, as demonstrated by the effect of adrenergic inhibition, the neurogenic mechanism of POI does not require bowel manipulation as simple skin incision can lead to bowel hypomotility and predispose the patient to ileus, as would be the case in XLIF. As Bauer and Boeckxstaens note in their review of mechanisms of POI, studies examining the neural contributions to bowel hypomotility are by and large performed immediately after surgery in animal models, supporting the notion that POI, which often lasts several days and may not be evident immediately postoperatively, has equally large contributions from the inflammatory and pharmacologic mechanisms [5].

35.2.2 Inflammatory

A number of studies examining immune cells in the muscularis externa of the bowel have shown that intestinal manipulation causes macrophages to release nitric oxide, cyclooxygenase 2, and prostaglandins as well as causes degranulation of mast cells in the muscularis externa in turn promoting inflammation and bowel wall edema and decreasing the contractility of bowel wall circular muscle [9, 10]. There is additional evidence supporting the synergistic interaction between the inflammatory and neuronal mechanisms of ileus, i.e., kinetically active substances released by the inflammatory cells in the bowel wall activate primary afferents to the gut and serve to perpetuate the neuronal contribution to POI [11].

35.2.3 Pharmacologic

While the abovementioned mechanisms of POI are dependent to some degree on manipulation of the bowel or activation of splanchnics through an abdominal incision, the pharmacologic mechanism of ileus is more broadly applicable to spinal surgery. It is well understood that activation of δ- and μ-opioid receptors decreases peristalsis, likely by stimulating the release of inhibitory neurotransmitters, and morphine is known to delay gastric emptying [12]. Similar to the interaction between inflammatory cells and neural mechanisms of ileus, activation of opioid receptors appears to stimulate NO release from immune cells in the bowel wall, further propagating the inflammatory mechanism of POI [13].

While the mechanism of POI following ALIF may be to some degree explained by the manipulation of the bowel associated with the approach [14, 15], mechanisms of POI following XLIF are less clear. Ileus following XLIF is likely mediated by neural pathways, and the increased incidence of ileus after surgeries performed at the L1–L2 level suggests that manipulation of the celiac plexus and resultant decrease in parasympathetic input to the GI smooth muscle may be a contributor.

35.3 Incidence of Ileus and GI Complications in Spinal Surgery

To date, there has been only one published study examining the incidence of and risk factors for POI following XLIF. However, with the increase in rates of lumbar fusion in the US population, there has been a burgeoning interest in defining the perioperative risk profile for developing ileus following spinal surgery [16, 17]. One of the first studies to report specifically on ileus rates in ALIF was performed to examine the perioperative complications of ALIF when using a vascular “exposure” surgeon in a cohort of 405 patients over an 8-year period from 2000 to 2008. While the primary outcome was a major and minor vascular injury necessitating repair, the authors mention that six patients had “prolonged” ileus (1.5 %) though they neglected to define what was considered prolonged. Of note, they state that the mean duration of postoperative ileus was 0.77 days, which, based on the working definition of prolonged postoperative ileus, would be considered physiologic and expected POI rather than a complication [14].

A similar retrospective cohort analysis from 2012 by Asha et al. examining perioperative complication rates when using a vascular access surgeon during ALIF and anterior lumbar disc replacement (ALDR) reported an incidence of POI in 18 of 121 patients (14.8 %). In this study, all patients with POI were treated conservatively – i.e., made NPO and underwent nasogastric tube placement – and resolved within 2–6 days [15]. While the above studies do provide insight into the incidence of POI following spinal surgery, they also highlight the difficulties inherent in analyzing the literature and attempting to determine risk factors given that pathologic versus physiologic postoperative ileus has historically been poorly defined.

In 2013, Fineberg et al. examined rates of ileus in postoperative spine patients through query of the National Inpatient Sample database which represents approximately 20 % of all hospital discharges. The study identified 220,552 posterior, anterior, and combined circumferential lumbar fusions over an 8-year period from 2002 to 2009 with associated rates of ileus of 2.6 %, 7.49 %, and 8.41 %, respectively, as identified by the admission’s association with the ICD-9 code for paralytic ileus (again, the duration of POI is not strictly defined in this study). Furthermore, patients with ileus had a significantly greater mean length of stay (LOS) than the non-ileus cohort regardless of the surgical approach and incurred significantly larger costs ranging from an average difference of $6,758 in patients undergoing PLF up to $7,857 in the combined anterior-posterior fusion cohort [17].

One study from 1995 looking at complications of ALIF in the thoracic and lumbar spine in adults at a single center from 1969 to 1992 reported on a number of complications common to anterior and posterior spine surgery. Their combined rate of ileus of 3.44 % (42 patients) is slightly lower than that reported in the current literature, which is understandable given their definition of POI as requiring a nasogastric tube for decompression for greater than 4 days postoperatively. In their sample of 1,223 anterior spine procedures performed in 1,152 adult patients, they also reported a number of additional GI complications they felt were common to anterior and posterior spine surgery, among them gastritis (four patients, 0.33 %), esophagitis (two patients, 0.16 %), duodenal ulcer (one patient, 0.08 %), and small bowel obstruction (one patient, 0.08 %). However, given the low incidence rates, these may or may not have been attributable to the procedure itself and may instead have been complication of hospitalization or the physiologic stress of surgery [18].

To the authors’ knowledge, there is only one paper to report on the incidence of prolonged postoperative ileus following XLIF. In a study published in 2014, Al Maaieh et al. observed POI, defined as ileus for greater than 3 days postoperatively, in 42 patients of a cohort of 596 (7.0 %) who underwent XLIF at a single institution over a 6-year period, which is similar to the rate reported in the ALIF literature. Also similar to previously reported literature of POI after spine surgery was the increase in postoperative length of stay (9.9 ± 4.3 days in the POI cohort, 5.6 ± 4.1 days in the control group).

35.4 Risk Factors for Gastrointestinal Complications After Interbody Fusion

In order to control for bias introduced by a surgeon’s learning curve, the aforementioned study of ileus in XLIF analyzed a matched cohort of patients undergoing interbody fusion based on the month of surgery. By doing so, they were able to employ uni- and multivariate analyses to look for risk factors for ileus following XLIF. Among the risk factors identified were gastroesophageal reflux disease, combined lateral and posterior instrumentation, and XLIF at the L1–L2 level. Notably, in addition to GERD, the use of a proton pump inhibitor was also found to be a risk factor for POI after surgery. Shindo et al. have reported decreased levels of ghrelin in patients with nonerosive reflux. Moreover, there is an emerging body of evidence supporting the notion that ghrelin is a bowel promotilic [19–21]. While intriguing, this correlation merits further examination.

Additional risk factors for complications after anterior and posterior spine surgery have been identified based on a multivariate analysis of nearly 1,600 patients from the National Inpatient Sample. The study, which looked at complications in six organ systems, identified several GI complications including ascites, colitis, GI bleed, ileus defined by abdominal distension and no passage of stool or flatus (at a rate of 2.26 %), obstruction, pancreatitis, and perforation with a total adverse event rate of 3.9 %. Risk factors for developing a GI complication included age >40, specifically age >65, previous cardiac incident, hypertension, anemia, revision surgery, combined anterior and posterior approach, and larger surgery based on the surgical invasiveness index which accounts for the number of levels involved and the approach. Of these, age greater than 65 and elevated surgical invasiveness were significant risk factors for complications in all organ systems [22].

Fineberg et al. list several independent risk factors for POI following anterior or posterior lumbar spine surgery including male sex, African-American ethnicity, greater than three level fusion, preoperative vitamin deficiency, use of BMP, and chronic anemia. The risk factors with the highest odds ratios were preexisting fluid and electrolyte disorders (OR 3.1) and a recent history of weight loss (OR 3.1). While electrolyte disorders are a known risk factor for developing ileus, the association with weight loss is less clear [17].

The scope of risk factors contributing to GI complications and ileus in posterior spinal fusion and anterior and lateral interbody fusion is presented here primarily due to the dearth of research investigating the incidence of and risk factors contributing to POI and GI complications following XLIF. It is likely that these various procedures share many of the same risk factors. However, given their differences, namely, avoidance of direct bowel manipulation with the lateral approach and promise of improved pain scores after XLIF possibly leading to faster mobilization and decreased opioid requirement, it is possible that there are differences in risk factors and outcomes that may be elucidated with further study.

35.5 Management of Postoperative Ileus

Unfortunately, there are no proven standardized regimens for addressing POI in patients undergoing spine surgery, which is related in some degree to the lack of data describing incidence rates and a limited understanding of risk factors in this patient population. Methods of addressing postoperative ileus naturally aim to combat the known causes of ileus, namely, the neurogenic, inflammatory, and pharmacologic mechanisms outlined above. While the bulk of the literature evaluating the management of POI has been performed in patients undergoing intra-abdominal surgery, there are a number of methods that may be applicable to those undergoing spinal surgery.

Traditional, non-pharmacologic supportive care has involved keeping the patient NPO until return of bowel function, encouraging early ambulation, and occasional placing of nasogastric tubes for decompression. While early ambulation has not been shown to increase time to return of bowel function, it is recommended for its additional postoperative benefits including decreasing the risk of venous thromboembolism [23]. Similarly, the placement of nasogastric tubes for the treatment of POI is not supported based on a Cochrane review from 2005 which found increased risk of pulmonary complications, decreased patient comfort, and increased length of stay in patients treated with NG tubes for POI after abdominal operations [24]. Limiting perioperative intravenous fluid to prevent bowel edema and using nonsteroidal anti-inflammatories, intravenous Tylenol, and atypical opioids such as tapentadol to reduce traditional opioid use have been shown to be effective means of decreasing the risk of developing POI [25–28]. However, treatment options are largely limited once a patient has developed prolonged ileus.

Opioids are commonly used after orthopedic surgery to combat postoperative pain, but the large doses administered via PCA, oral analgesics, and frequently via breakthrough injections have well-known gastrointestinal side effects [4, 29]. Complicating the use of opioids and their association with POI is the fact that while opioids achieve their analgesic effect in the CNS through their action on mu-opioid receptors, these same receptors exist in the gut, and their stimulation is the cause of the adverse GI side effects seen in opioid use [29].

Alvimopan

, a peripherally acting mu-opioid receptor blocker which does not cross the blood-brain barrier, was created to theoretically block the adverse effects of opioids on the GI tract while still allowing for their use as a postoperative analgesic. In a meta-analysis of five studies comparing the drug to placebo, it was shown to decrease the time to bowel movement and toleration of solid food and ultimately decreased time to discharge when used in patients following abdominal surgery [30]. The drug, however, is approved only in the USA for GI recovery in patients undergoing upper or lower GI bowel resection surgery with primary anastomosis (need FDA reference). While it may be used off label in some centers, no such data exists to support its use in patients with POI following spinal surgery.

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