Migrating motility complexes persist after severe traumatic shock in patients who tolerate enteral nutrition

[Gastrointestinal motility in critically ill patients]

Up to 80% of all critically ill patients develop gastrointestinal dysfunction, predominantly gastrointestinal motility disorder. In critically ill patients, gastrointestinal dysfunction or gastrointestinal failure is associated with increased morbidity and mortality. Correct diagnosis and early start of treatment are essential and can influence the outcome. Therapeutic options are normal potassium and magnesium levels, restrictive fluid balance, improved gastrointestinal microcirculation, individual sedoanalgetic concepts and early enteral nutrition. In addition, numerous target-oriented medical therapeutic options are available.

Defining and Assessing Tolerance in Enteral Nutrition

Nutrition support has become widely recognized as an essential component of optimal care for acutely ill patients. Enteral nutrition is preferred over parenteral routes when possible. However, prescribed enteral nutritional regimens are sometimes met with side effects and even complications. These adverse events have been collectively termed "intolerance," and forms of intolerance occur in a spectrum from bothersome at least to life threatening when most severe. Here we discuss nutritional access and its maintenance, introduce and define intolerance, and then review the current literature with regard to principal forms of enteral nutrition intolerance.

Continuous intra-abdominal pressure monitoring

BACKGROUND

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) can develop within 12 hours of ICU admission in high-risk patients. Until recently the intermittent intra-abdominal pressure (IAP) measurement via the urinary catheter was the clinical standard. This is a relatively labour intensive technique and its intermittent nature could prevent timely recognition of significant changes in IAP. The historical continuous IAP (CIAP) measurements were poorly reproducible (gastric route) or invasive/impractical (direct measurement). The aim of this paper is to review the current evidence on CIAP monitoring.

METHODS

A broad Medline search of the English literature was performed using the terms of "intra abdominal pressure" and "continuous". This result was analysed based on the title and abstract. Only original clinical studies with continuous IAP measurement were considered in this review. New techniques of CIAP monitoring evaluated in large animal models are discussed as potential future directions.

RESULTS

There is a growing evidence of measuring (monitoring) CIAP using several techniques (gastric, direct abdominal, inferior vena cava, and urinary bladder. The strongest evidence supports the direct abdominal, the gastric and the bladder route. From these three techniques the CIAP monitoring via the bladder has excellent agreement with the current standard of intermittent bladder pressure measurement. While the direct measurement could be very accurate it is an invasive method and feasible in patient who underwent laparotomy or laparoscopy.

CONCLUSIONS

Until a better technique is available the CIAP monitoring via the bladder or stomach should be considered as the standard for continuous monitoring of the IAP. It is a less labour intensive, safe, less invasive and reliable method.

Measurement of intra-abdominal pressure in dogs and cats

OBJECTIVE

To review and summarize the human and veterinary literature on intra-abdominal pressure measurement techniques.

DATA SOURCES

Human and veterinary clinical studies, research articles, reviews, and textbooks with no date restrictions with a focus on techniques for intra-abdominal pressure (IAP) measurement and their limitations.

HUMAN DATA SYNTHESIS

Human literature has established the intravesicular method as the gold standard for indirect measurement of IAP. However, current research has explored the intragastric method as a valid alternative. Recently, debate has focused on the shortcomings of the various measurement methods.

VETERINARY DATA SYNTHESIS

Early human literature using dogs as models contributed to the original data for IAP measurements in small animals. Since that time, a number of clinical studies and 1 case report have contributed to that original information. A reference interval for IAP measured by the intravesicular method has recently been determined in healthy cats.

CONCLUSIONS

Further studies investigating IAP in critically ill veterinary patients are required to establish the optimal technique for this measurement in veterinary medicine.

A multicenter, randomized controlled trial comparing early nasojejunal with nasogastric nutrition in critical illness

OBJECTIVE

Current guidelines recommend enteral nutrition in critically ill adults; however, poor gastric motility often prevents nutritional targets being met. We hypothesized that early nasojejunal nutrition would improve the delivery of enteral nutrition.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Seventeen multidisciplinary, closed, medical/surgical, intensive care units in Australia.

PATIENTS

One hundred and eighty-one mechanically ventilated adults who had elevated gastric residual volumes within 72 hrs of intensive care unit admission.

INTERVENTIONS

Patients were randomly assigned to receive early nasojejunal nutrition delivered via a spontaneously migrating frictional nasojejunal tube, or to continued nasogastric nutrition.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the proportion of the standardized estimated energy requirement that was delivered as enteral nutrition. Secondary outcomes included incidence of ventilator-associated pneumonia, gastrointestinal hemorrhage, and in-hospital mortality rate. There were 92 patients assigned to early nasojejunal nutrition and 89 to continued nasogastric nutrition. Baseline characteristics were similar. Nasojejunal tube placement into the small bowel was confirmed in 79 (87%) early nasojejunal nutrition patients after a median of 15 (interquartile range 7-32) hrs. The proportion of targeted energy delivered from enteral nutrition was 72% for the early nasojejunal nutrition and 71% for the nasogastric nutrition group (mean difference 1%, 95% confidence interval -3% to 5%, p=.66). Rates of ventilator-associated pneumonia (20% vs. 21%, p=.94), vomiting, witnessed aspiration, diarrhea, and mortality were similar. Minor, but not major, gastrointestinal hemorrhage was more common in the early nasojejunal nutrition group (12 [13%] vs. 3 [3%], p=.02).

CONCLUSIONS

In mechanically ventilated patients with mildly elevated gastric residual volumes and already receiving nasogastric nutrition, early nasojejunal nutrition did not increase energy delivery and did not appear to reduce the frequency of pneumonia. The rate of minor gastrointestinal hemorrhage was increased. Routine placement of a nasojejunal tube in such patients is not recommended.

Gastrointestinal dysmotility: clinical consequences and management of the critically ill patient

Gastrointestinal dysmotility is a common feature of critical illness, with a number of significant implications that include malnutrition secondary to reduced feed tolerance and absorption, reflux and aspiration resulting in reduced lung function and ventilator-associated pneumonia, bacterial overgrowth and possible translocation causing nosocomial sepsis. Prokinetic agent administration can improve gastric emptying and caloric delivery, but its effect on nutrient absorption and clinical outcomes is, as yet, unclear. Postpyloric delivery of nutrition has not yet been demonstrated to increase caloric intake or improve clinical outcomes.

Intestinal ischemic preconditioning after ischemia/reperfusion injury in rat intestine: profiling global gene expression patterns

OBJECTIVE

Intestinal ischemia/reperfusion (IR) injury involves activation of inflammatory mediators, mucosal necrosis, ileus, and alteration in a variety of gene products. Ischemic preconditioning (IPC) reduced all the effects of intestinal injury seen in IR. In an effort to investigate the molecular mechanisms responsible for the protective effects afforded by IPC, we sought to characterize the global gene expression pattern in rats subjected to IPC in the setting of IR injury.

METHODS

Rats were randomized into five groups: (1) Sham, (2) IPC only (3) IR, (4) Early IPC + IR (IPC --> IR), and (5) Late IPC + IR (IPC --> 24 h --> IR). At 6 h after reperfusion, ileum was harvested for total RNA isolation, pooled, and analyzed on complementary DNA (cDNA) microarrays with validation using real-time polymerase chain reaction (PCR). Significance Analysis of Microarray (SAM) software was used to determine statistically significant changes in gene expression.

RESULTS

Early IPC + IR had 5,167 induced and 4 repressed genes compared with the other groups. SAM analysis revealed 474 out of 10,000 genes differentially expressed among the groups. Early and Late IPC + IR had more genes involved in redox hemostasis, the immune/inflammatory response, and apoptosis than either the IPC only or IR alone groups.

CONCLUSION

The transcriptional profile suggests that IPC exerts its protective effects by regulating the gene response to injury in the intestine.

Pretreatment with bone morphogenetic protein-7 (BMP-7) mimics ischemia preconditioning following intestinal ischemia/reperfusion injury in the intestine and liver

Intestinal ischemia/reperfusion (I/R) injury has been shown to cause intestinal mucosal injury and adversely affect function. Ischemic preconditioning (IPC) has been shown to protect against intestinal I/R injury by reducing polymorphonuclear leukocyte infiltration, intestinal mucosal injury, and liver injury, and preserve intestinal transit. Bone morphogenetic protein 7 (BMP-7) has been shown to protect against I/R injury in the kidney and brain. Recently, microarray analysis has been used to examine the possible IPC candidate pathways. This work revealed that IPC may work through upregulation of BMP-7. The purpose of this study was to examine if pretreatment with BMP-7 would replicate the effects seen with IPC in the intestine and liver after intestinal I/R. Rats were randomized to six groups: sham, I/R (30 min of superior mesenteric artery occlusion and 6 h of R), IPC+R (three cycles of superior mesenteric artery occlusion for 4 min and R for 10 min), IPC+I/R, BMP-7+R (100 microm/kg recombinant human BMP-7), or BMP-7+I/R. A duodenal catheter was placed, and 30 min before sacrifice, fluorescein isothiocyanate-Dextran was injected. At sacrifice, dye concentrations were measured to determine intestinal transit. Ileal mucosal injury was determined by histology and myeloperoxidase activity was used as a marker of polymorphonuclear leukocyte infiltration. Serum levels of aspartate aminotransferase were measured at sacrifice to determine liver injury. Pretreatment with BMP-7 significantly improved intestinal transit and significantly decreased intestinal mucosal injury and serum aspartate aminotransferase levels, comparable to animals undergoing IPC. In conclusion, BMP-7 protected against intestinal I/R-induced intestinal and liver injury. Bone morphogenetic protein 7 may be a more logical surrogate to IPC in the prevention of injury in the setting of intestinal I/R.

Intestinal edema: effect of enteral feeding on motility and gene expression

OBJECTIVE

Edema formation, inflammation, and ileus in the intestine are commonly seen in conditions like gastroschisis, inflammatory bowel disease, and cirrhosis. We hypothesized that early enteral feeding would improve intestinal transit. We also wanted to study the impact of early enteral feeding on global gene expression in the intestine.

DESIGN

Rats were divided into Sham or Edema +/- immediate enteral nutrition (IEN). At 12 h, small intestinal transit via FITC-Dextran and tissue water were measured. Ileum was harvested for total RNA to analyze gene expression using cDNA microarray with validation using real-time PCR. Data are expressed as mean +/- SEM, n = 4-6 and (*), (**) = P < 0.05 versus all groups using ANOVA.

RESULTS

IEN markedly improved intestinal transit with minimal genetic alterations in Edema animals. Major alterations in gene expression were detected in primary, cellular and macromolecular metabolic activities. Edema also altered more genes involved with the regulation of the actin cytoskeleton.

CONCLUSIONS

Intestinal edema results in impaired small intestinal transit and globally increased gene expression. Early enteral nutrition improves edema-induced impaired transit and minimizes gene transcriptional activity.

Gastrointestinal motility in acute illness

Critical illness affects gastrointestinal motility - not only as a primary problem, which brings the patient to the intensive care unit (ICU), but also as a complication consecutive to the ICU stay. Motility disturbances may result from impaired function of gastrointestinal muscle, pacemaker cell function and nerve activity. The most important neural control system is the enteric nervous system that contains the largest collection of neurons (10(8) cells) outside the central nervous system. Through its organization it can operate independently of the brain and generate motility patterns according to need: a postprandial motility pattern starting after food intake, and an interdigestive motility pattern starting several hours after a meal. Undisturbed intestinal motility depends critically on a balanced interaction between inhibition and excitation, and a disturbance in this balance leads to severe derangements of intestinal motility. These motility disturbances differ in clinical appearance and location but can affect all parts of the gastrointestinal tract. This review focuses on select motility disturbances such as gastroparesis, postoperative ileus, and Ogilvie's syndrome. Generally effective methods to treat these conditions are given. Finally, we focus on special management options to prevent such motility disturbances or to reduce their severity.

Enteral glutamine during active shock resuscitation is safe and enhances tolerance of enteral feeding

BACKGROUND

Feeding the hemodynamically unstable patient is increasingly practiced, yet few data exist on its safety. Because enteral glutamine is protective to the gut in experimental models of shock and improves clinical outcomes, it may benefit trauma patients undergoing shock resuscitation and improve tolerance if administered early. This pilot study aimed to evaluate gastrointestinal tolerance and safety of enteral feeding with glutamine, beginning during shock resuscitation in severely injured patients.

METHODS

In a prospective randomized trial, 20 patients were randomly assigned to either an enteral glutamine group (n = 10) or a control group (n = 10). Patients with severe trauma meeting standardized shock resuscitation criteria received enteral glutamine 0.5 g/kg/d during the first 24 hours of resuscitation and 10 days thereafter. Immune-enhancing diet began on postinjury day 1, with a target of 25 kcal/kg/d. Control patients received isonitrogenous whey powder plus immune-enhancing diet. Tolerance (vomiting, nasogastric output, diarrhea, and distention) was assessed throughout the study.

RESULTS

Glutamine was well tolerated and no adverse events occurred. Treated patients had significantly fewer instances of high nasogastric output (5 vs 23; p = .010), abdominal distention (3 vs 12; p = .021), and total instances of intolerance (8 vs 42; p = .011). Intensive care unit (ICU) and hospital length of stay were comparable. Control patients required supplemental parenteral nutrition (PN) to meet goals at day 7.

CONCLUSIONS

Enteral glutamine administered during active shock resuscitation and through the early postinjury period is safe and enhances gastrointestinal tolerance. A large clinical trial is warranted to determine if enteral glutamine administered to the hemodynamically unstable patient can reduce infectious morbidity and mortality.

Postinjury abdominal compartment syndrome does not preclude early enteral feeding after definitive closure

BACKGROUND

Critically injured patients are susceptible to the abdominal compartment syndrome (ACS), which requires decompressive laparotomy with delayed abdominal closure. Previous work by the University of Texas Houston group showed impaired gut function after resuscitation-associated gut edema. The purpose of this study was to determine if enteral nutrition was precluded by the intra-abdominal hypertension and bowel edema of the ACS.

METHODS

Patients developing postinjury ACS from January 1996 to August 2003 at our level-I trauma center were reviewed. Patient demographics, time to definitive abdominal closure, and institution and tolerance of enteral nutrition were evaluated.

RESULTS

Thirty-seven patients developed postinjury ACS during the study period; 26 men and 11 women with a mean age of 36 +/- 4 and injury severity score of 33 +/- 4. Mean intra-abdominal pressure before decompression was 32 +/- 3 mm Hg, and concurrent mean peak airway pressure was 50 +/- 4 cm oxygen. Enteral feeding was never started in 12 patients; 4 died within 48 hours of admission, 7 required vasoactive agents until their death, and 1 developed an enterocutaneous fistula requiring parenteral nutrition. Enteral feeding was initiated in the remaining 25 patients: 13 had feeds started within 24 hours of abdominal closure; 5 were fed with open abdomens; and 7 had a delay because of vasopressors (n = 2), multiple trips to the operating room (n = 2), paralytics (n = 2), and increased intra-abdominal pressures (n = 1). Once advanced, enteral feeding was tolerated in 23 (92%) of the 25 patients with attainment of goal feeds in a mean of 3.1 +/- 1 days.

CONCLUSIONS

Despite the bowel edema and intra-abdominal hypertension related to the ACS, early enteral feeding is feasible after definitive abdominal closure.

Continuous intra-abdominal pressure measurement technique

BACKGROUND

Abdominal compartment syndrome can develop within 12 hours of intensive care unit (ICU) admission in high-risk (shock/trauma, burn, pancreatitis, postabdominal aortic surgery) patients. The current standard of intra-abdominal pressure (IAP) measurement via the urinary catheter is labor intensive, and its intermittent nature could prevent timely recognition of significant changes in IAP. We propose that continuous IAP (CIAP) can be accurately measured via the irrigation port of a three-way catheter and has good agreement with the standard intermittent IAP (IIAP).

METHODS

CIAP was prospectively validated by comparing it with IIAP measurement in general surgical and trauma patients admitted to the ICU with a three-way urinary catheter. CIAP was measured via the irrigation port of the three-way catheter transduced to the bedside monitor as a continuous trace without intermittent clamping of the catheter. The standard IIAP measurements were performed via the urine drainage port after clamping the catheter and filling the bladder with 50 mL of 0.9% saline. Each patient had three separate paired measurements performed in standardized manner to compare CIAP with IIAP. Patients' demographics, injury severity, type of surgery, body mass index (BMI), and the paired individual IAP measurements were recorded. The paired measurements were compared using the Bland-Altman (B-A) method for comparing a new clinical measurement with an established one. Data are presented as mean +/- standard error of the mean.

RESULTS

During a 6-month period (ending in July 2003), 25 patients were investigated. The mean age was 61.5 +/- 4 years, 66% were men, and BMI was 29.2 +/- 2 kg/m(2). Six patients had vascular surgical, four elective and three urgent general surgical interventions. There were 12 trauma patients with ISS of 23 +/- 2. The CIAP was 14.2 +/- 0.66 (range 2 to 24) mm Hg, and the IIAP was 14.0 +/- 0.68 (range 3 to 24) mm Hg. Seventy-five percent of the measured pairs were exactly the same; in 21%, there was 1 mm Hg difference and in 4% 2 mm Hg. There was no measurement difference greater than 2 mm Hg. The mean difference between the CIAP and IIAP was 0.019 +/- 0.05 mmHg. The B-A statistics revealed that the difference between the means of measurements in each individual patient was between +/-1.96 SD (95% confidence intervals). The B-A scatter plot did not follow any patterns of typical systematic bias.

CONCLUSION

CIAP measurement with a three-way urinary catheter is a simple and accurate method for monitoring IAP. It has an excellent agreement with the IIAP over wide pressure ranges and should replace the current labor-intensive intermittent technique.

Hypertonic saline prevents inflammation, injury, and impaired intestinal transit after gut ischemia/reperfusion by inducing heme oxygenase 1 enzyme

BACKGROUND

Hypertonic saline (HTS) has been shown to modulate the inflammatory response after shock. We have previously demonstrated that heme oygenase-1 (HO-1) induction is protective against gut dysfunction in models of shock-induced gut ischemia/reperfusion (I/R). We therefore hypothesized that HTS prevents gut inflammation, injury, and impaired transit by inducing HO-1 in a model of gut I/R.

METHODS

Rats underwent 60 minutes of superior mesenteric artery occlusion (SMAO) and then were resuscitated with 4 mL/kg of HTS, an equal volume of lactated Ringer's (LR) solution (4 mL/kg, low volume), or equal salt LR solution (32 mL/kg, high volume) and compared with SMAO alone or shams. A separate group was pretreated with the HO-1 blocker Sn protoporphyrin IX (SNP IX) before SMAO plus HTS. At 6 hours of reperfusion, transit was determined and ileum harvested for HO-1 (anti-inflammatory) and inducible nitric oxide synthase (proinflammatory) immunoreactivity, myeloperoxidase (MPO) activity, and histologic injury. Data are expressed as mean +/- SEM (analysis of variance).

RESULTS

Intestinal transit was severely impaired after SMAO (2.5 +/- 0.1), improved with low- and high-volume LR solution (3.2 +/- 0.2 and 3.1 +/- 0.1, not significant), but returned to sham (4.6 +/- 0.2) with HTS (4.8 +/- 0.2). Pretreatment with SNP abrogated this protective effect. Myeloperoxidase activity was significantly increased by SMAO (SMAO, 2.3 +/- 0.3; sham, 0.4 +/- 0.05), lessened by low- and high-volume LR solution (1.5 +/- 0.3 and 1.7 +/- 0.4), but returned to sham levels with HTS (1.0 +/- 0.01). Activity with SNP IX pretreatment was significantly increased (4.04 +/- 0.8). Mucosal injury followed a similar pattern. Inducible nitric oxide synthase was increased by SMAO and low- and high-volume LR solution (0.8 +/- 0.2, 0.8 +/- 0.03, and 0.8 +/- 0.02, respectively; sham, 0.5 +/- 0.02), but significantly reduced by HTS (0.7 +/- 0.02). HO-1 was induced by SMAO and low- and high-volume LR solution (0.33 +/- 0.02, 0.32 +/- 0.03, and 0.37 +/- 0.4, respectively; sham, 0.0 +/- 0.0), but was further increased with HTS (0.49 +/- 0.04).

CONCLUSION

HTS resuscitation protects against inflammation, injury, and impaired intestinal transit after gut I/R in part by inducing HO-1. This is a novel mechanism of HO-1 protection.

Heme oxygenase-1 induction by hemin protects against gut ischemia/reperfusion injury

BACKGROUND

We have shown that both intraischemic hypothermia and hypertonic saline resuscitation provide dramatic protection against gut ischemia/reperfusion (I/R) injury that is in part mediated by heme oxygenase-1 (HO-1). We therefore hypothesized that induction of HO-1 by hemin would lessen damage and improve function after gut I/R.

MATERIALS AND METHODS

Male Sprague-Dawley rats were treated with 50 micromol/kg hemin (HO-1 inducer ferric protoporphyrin IX chloride) sq or vehicle 2 h before superior mesenteric artery occlusion for 60 min or sham laparotomy. After 6 h of reperfusion, transit was determined by quantitation of percentage of tracer in 10 equal segments of small intestine 30 min following injection into the duodenum (expressed as mean geometric center). Ileum was harvested for assessment of mucosal histologic injury (Chiu score 0-5 by blinded observer), myeloperoxidase activity (MPO, index of inflammation), and HO-1 protein expression.

RESULTS

Hemin treatment was associated with increased HO-1 protein expression, lessened mucosal injury, decreased MPO activity, and improved intestinal transit following gut I/R.

CONCLUSION

These data corroborate that HO-1 plays an important role in protecting the gut against I/R-induced injury.

Postinjury enteral tolerance is reliably achieved by a standardized protocol

BACKGROUND

Postinjury enteral nutrition (EN) is beneficial. Unfortunately, severely injured patients who should benefit most are frequently intolerant. To assist in maximizing enteral tolerance in the critically injured, we first implemented a prospective analysis of the effectiveness of a standardized enteral protocol (EP) at a single institution followed by a prospective multi-institutional analysis of its implementation.

METHODS

Tolerance parameters were prospectively collected on severely injured patients at a single (Phase I) and then multiple (Phase II) institutions. EN was begun at 15 cc/h and advanced every 12 h to a patient specific targeted goal. Intolerance symptoms (high nasogastric output/emesis, abdominal distention, and diarrhea) were assessed and graded every 12 h and managed using a standardized protocol. Tolerance was characterized as early (during initial advancement of feeds) or late (after standard goal) and classified as good (EN advanced per EP), moderate (rate decreased per EP), poor (EN held per EP), or EN discontinued (and TPN begun).

RESULTS

In Phase I patients (ISS = 25 +/- 3) early tolerance was good in 82% (14/17) while late good tolerance decreased to 65% (11/17). In Phase II patients (ISS = 30 +/- 2), early tolerance was good in 85% (41/49) and late tolerance was good in 80% (39/49). Moderate intolerance was primarily seen in Phase II patients and due to high gastric output in patients fed proximal to the ligament of Treitz (13/16). Overall 88% (15/17) of Phase I and 100% (49/49) of Phase II patients were successfully maintained on EN.

CONCLUSIONS

Severely injured patients exhibited good tolerance to EN when managed using a standardized protocol at four Level I trauma centers. Moderate intolerance was associated with high gastric output and may be lessened by feeding distal to the ligament of Treitz.