Gastric secretory response to head injury

Gastrointestinal prophylaxis in neurocritical care

The aim of this study is to review and summarize the relevant literature regarding pharmacologic and non-pharmacologic methods of prophylaxis against gastrointestinal (GI) stress ulceration, and upper gastrointestinal bleeding in critically ill patients. Stress ulcers are a known complication of a variety of critical illnesses. The literature regarding epidemiology and management of stress ulcers and complications thereof, is vast and mostly encompasses patients in medical and surgical intensive care units. This article aims to extrapolate meaningful data for use with a population of critically ill neurologic and neurosurgical patients in the neurological intensive care unit setting. Studies were identified from the Cochrane Central Register of controlled trials and NLM PubMed for English articles dealing with an adult population. We also scanned bibliographies of relevant studies. The results show that H(2)A, sucralfate, and PPI all reduce the incidence of UGIB in neurocritically ill patients, but H(2)A blockers may cause encephalopathy and interact with anticonvulsant drugs, and have been associated with higher rates of nosocomial pneumonias, but causation remains unproven and controversial. For these reasons, we advocate against routine use of H(2)A for GI prophylaxis in neurocritical patients. There is a paucity of high-level evidence studies that apply to the neurocritical care population. From this study, it is concluded that stress ulcer prophylaxis among critically ill neurologic and neurosurgical patients is important in preventing ulcer-related GI hemorrhage that contributes to both morbidity and mortality. Further, prospective trials are needed to elucidate which methods of prophylaxis are most appropriate and efficacious for specific illnesses in this population.

Prospective, randomized comparison of lansoprazole suspension, and intermittent intravenous famotidine on gastric pH and acid production in critically ill neurosurgical patients

BACKGROUND

There is a paucity of studies comparing stress ulcer prophylaxis (SUP) agents in high-risk neurosurgical patients.

METHODS

In this prospective, randomized study, critically ill neurosurgical patients received lansoprazole 30 mg suspension via NG/NJ tube daily or famotidine 20 mg IV q12 h for SUP. Gastric pH and residual volumes were recorded for 3 days and adverse events for 7 days after admission.

RESULTS

There were 51 patients randomized to lansoprazole (n = 28) or famotidine (n = 23) who received SUP for ≥ 3 days. All patients had at least two risk factors for SRMD, and 75% had a baseline GCS < 9. On day 1 of therapy, more famotidine patients had a gastric pH ≥ 4 at least 80% of the time as compared to lansoprazole patients (74 vs. 36%, P = 0.01, respectively); however, there was no difference on days 2 and 3. Enteral feedings on day 1 predicted a pH ≥ 4 (P = 0.01). There were no significant differences in the percentages of time gastric residual volumes < 28 ml (P = NS). Heme-positive aspirates were present in 18-39% of patients (P = NS); one patient receiving famotidine met the criteria for overt bleeding. Thrombocytopenia occurred in 17% in the famotidine group and 4% in the lansoprazole group (P = NS).

CONCLUSIONS

Neurosurgery ICU patients receiving famotidine for SUP achieved a gastric pH ≥ 4 more often than lansoprazole-treated patients, but only on day 1 of the 3-day study period. Both agents were equally effective in reducing gastric acid production. There was no difference in the incidence of mucosal damage and thrombocytopenia.

Stress ulceration in the intensive care unit: use of H2-receptor antagonists

H2-receptor antagonist drug therapy is the mainstay of peptic ulcer treatment in the USA. About 75% of patients in intensive care units receive parenteral H2-antagonists. The rationale for their use is that parenteral H2-antagonists offer about a four-fold protective effect compared with placebo against significant upper gastrointestinal haemorrhage. Parenteral administration of H2-receptor antagonists appears to be preferred to oral antacid or sucralfate regimens because of ease of administration and, perhaps, lower treatment costs. Recommended dosage schedules for intravenously administered H2-receptor antagonists are at fixed intervals, 6- to 8-h intervals for cimetidine and ranitidine and 12-h intervals for famotidine. These dosage schedules assume a fixed dose-response relationship (i.e. a given dose of H2-antagonist results in equivalent acid suppression throughout the circadian, or 24-h, period). However, human basal gastric acid secretion exhibits circadian variation, with peak rates occurring during the evening hours. Recent evidence from 24-h continuous intragastric pH studies in fasting patients with healed duodenal ulcer suggests that larger doses of intravenous H2-antagonists are required in the evening than in the morning to achieve equivalent acid suppression. These findings are consistent with a changing H2-antagonist dose/acid-inhibiting response over the circadian period. Continuous infusion has the advantage of providing consistent and sustained suppression of gastric acid secretion in patients at risk for stress ulceration. Results of a double-blind, randomized, crossover study indicated that equally effective suppression of acidity and time-to-onset of pharmacological effect can be achieved with and without priming bolus doses of ranitidine, and presumably other H2-receptor antagonists as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress Ulceration Requiring Definitive Surgery after Severe Trauma

Despite antiulcer prophylaxis 19 severely injured patients at our institution developed stress ulceration (SU) between 1989 and 1999 requiring surgery for perforation (n = 4) or bleeding (n = 15). A herald bleed (HB) 10.7 ± 1.2 days after admission, 7.2 ± 1.2 days before definitive operative therapy, and requiring 7.1 ± 0.9 units of blood occurred in 93 per cent of patients operated on for bleeding. Bleeding preceded perforation in one patient. Central nervous system damage was part of the injury pattern in 68 per cent of the patients including spinal cord (42%), severe head injury (16%), or both (10%). Forty-two per cent had acalculous cholecystitis found at surgery. Eight patients had vagotomy and antrectomy (VA), and 11 patients had vagotomy and pyloroplasty (VP). VA required more time than VP (255 ± 41 vs 158 ± 13 minutes; P = 0.02). One patient (12.5%) rebled after VA versus two (18%) after VP; one patient in each group required reoperation. There was no difference in mortality, length of stay, or intensive care unit stay. A herald bleed preceded recurrent hemorrhage of SU by one week. Spinal cord or head injury increase the risk of SU. More than 40 per cent of patients with SU had acalculous cholecystitis found at operation. VA provides no benefit on rebleeding or reoperation over VP, so anatomical considerations and not rebleed rates should determine the surgical procedure.

The nutritional management of patients with head injuries

Severe head injuries tend to be associated with hypermetabolism and hypercatabolism resulting in negative nitrogen balances which may exceed 30 grams day-1. Enteral feeding should begin as soon as the patient is hemodynamically stable, attempting to reach a non-protein caloric intake of at least 30-35 kcal kg-1 day-1 and a protein intake of 2.0-2.5 g kg-1 day-1 as soon as possible. With severe head injuries (Glasgow Coma Scale < 8), there is an increased tendency for gastric feeding to regurgitate into the upper airway. Keeping the patient upright and checking residuals is important in such patients. Jejunal feedings are less apt to be aspirated. If it is apparent that the gastro-intestinal tract cannot be used to reach the nutritional goals within three days, total parental nutrition is begun within 24-48 h so as to reach these nutrition goals by either one or both routes by the third or fourth day. Blood glucose levels exceeding 150-200 mg dl-1 tend to increase the severity of the neurologic problems and efforts should be made to prevent hyperglycemia by carefully regulating the glucose and insulin intake. Indirect calorimetry to determine the respiratory quotient and resting energy expenditure should be determined twice weekly. To determine N2 balance, urinary urea nitrogen should be measured in 24-h specimens. These tests should be performed once or twice weekly until it is clear that the nutrition is adequate.

Acute gastrointestinal bleeding in the intensive care unit. The gastroenterologist's perspective

Although SRES-associated hemorrhage previously constituted a significant cause of bleeding in the ICU, improvements in ICU management and the institution of prophylactic measures in high-risk patients have significantly reduced SRES-associated hemorrhage since the 1980s. Antacids, H2-receptor antagonists, and sucralfate have been shown to be effective in preventing clinically significant bleeding resulting from SRES, particularly when the intragastric pH is maintained at greater than 4. A selective approach should be adopted in SRES prophylaxis: Patients on mechanical ventilation, with coagulopathy, or with two of the other known risk factors should receive prophylaxis. Although the drug of choice depends to some extent on local preferences, an H2-receptor antagonist by continuous intravenous infusion may represent the best option. No pharmacologic therapy is of proven value once hemorrhage begins, but the current interventional techniques are effective in controlling hemorrhage. Gastrointestinal bleeding from NOMV has become less common with improvements in the hemodynamic monitoring of critically ill patients, but this disease must always be considered when lower gastrointestinal bleeding occurs in the context of relative hypoperfusion. For SRES and NOMV, treatment of the underlying disease or diseases is the optimal route to prevention.

Impact of trauma stress ulcer prophylaxis guidelines on drug cost and frequency of major gastrointestinal bleeding

Trauma patients are routinely prescribed stress ulcer prophylaxis despite evidence suggesting such therapy be limited to patients with identifiable risk factors for bleeding. With surgeons' consensus, we developed and implemented trauma stress ulcer prophylaxis guidelines, and measured the impact of clinical pharmacists on implementing the guidelines and the effect of the guidelines on drug cost and frequency of major gastrointestinal bleeding. Two groups of 150 consecutive patients admitted with multiple trauma were evaluated before and after guideline implementation and stratified by Injury Severity Score (ISS) to minor (ISS < 9) or moderate to severe (ISS > or = 9) trauma groups. The number of patients prescribed stress ulcer prophylaxis, length and cost of this therapy, and number of patients experiencing major gastrointestinal bleeding (decrease in consecutive hemoglobin > or = 2 g/dl in conjunction with coffee-ground emesis, hematemesis, melena, or hematochezia) were measured. All pharmacist interventions pertaining to stress prophylaxis were collected. Fewer patients were prescribed stress ulcer prophylaxis after guideline implementation (105/150, 70% vs 39/150, 26%, p<0.0001), leading to a decrease in total drug cost of $4558. Use decreased more in patients with minor (40/54, 74% vs 9/59, 15%, p<0.0001) than moderate to severe (65/96, 68% vs 30/91, 33%, p<0.0001) trauma. Neither length of therapy nor agent of choice (> 95% cimetidine) differed between groups. Fifteen (38%) of 38 postguideline prophylaxis orders were determined by the pharmacist not to meet guideline criteria. Recommendations to discontinue therapy were accepted in 9 (60%) of 15 instances. The frequency of major gastrointestinal bleeding remained unchanged between groups (1/150 vs 0/150, p=1.0). Implementation of trauma stress ulcer prophylaxis guidelines limiting therapy to patients with risk factors for bleeding led to a 80% decrease in drug cost and did not affect the frequency of major gastrointestinal bleeding.

A review of stress ulcer prophylaxis in the neurosurgical intensive care unit

STRESS ULCERS OCCUR frequently in intensive care unit patients who have intracranial disease. After major physiological stress, endoscopic evidence of mucosal lesions of the gastrointestinal tract appears within 24 hours of injury; 17% of these erosions progress to clinically significant bleeding. Gastrointestinal hemorrhage has been associated with mortality rates of up to 50%. The pathogenesis of stress ulcers may not be completely understood, but gastric acid and pepsin appear to play significant roles. Antacids, H2 antagonists, and sucralfate are effective prophylactic agents in the medical/surgical intensive care unit. Appropriate therapy for neurosurgical patients remains unclear, however. This review summarizes the current literature regarding the pathogenesis and therapy of stress ulcers in neurosurgical patients.

A risk analysis of stress ulceration after trauma

Prophylaxis for stress ulceration is considered standard care for most critically ill patients, but may be overutilized. We determined the incidence of stress ulceration in 33,637 major trauma patients treated in a regionalized trauma system from 1985 to 1991 using trauma registry data and chart review. Injury-related risk factors for stress ulceration and other associated infectious and organ failure complications were identified by regression analysis. Clinical stress ulceration developed in 57 patients (0.17%) despite prophylaxis. Eighteen patients (0.05%) developed severe ulceration with either gastroduodenal perforation (3 patients) or a > 2 U blood transfusion requirement (16 patients). Independent risk factors with odds ratios (OR) were identified as follows: Injury Severity Score (ISS) > or = 16, OR = 12.6; spinal cord injury, OR = 2.0; and age > 55, OR = 2.4. Other serious complications, including pneumonia, sepsis, and organ failure (adult respiratory distress syndrome and renal and hepatic failure), were significantly associated with the development of stress ulceration. Clinically significant stress ulceration after trauma is uncommon, but occurs despite prophylaxis. Severe injury (ISS > 16) and spinal cord injury were identified as independent injury-related risk factors. All patients with severe ulceration had either one of these injury-related risk factors or a significant infectious complication or organ failure. Standard prophylaxis may be inadequate in high-risk patients, who should be targeted for increased surveillance and aggressive prophylaxis. On the other hand, routine prophylaxis in low-risk patients may be overutilized.

Effect of ranitidine on intragastric pH and stress-related upper gastrointestinal bleeding in patients with severe head injury

We conducted a double-blind, placebo-controlled study to evaluate the effects of ranitidine on intragastric pH and upper gastrointestinal tract bleeding in severe head injury patients. Within 24 hr of the precipitating trauma, 34 adults with Glasgow coma scale scores < or = 10 were randomized to a 6.25 mg/hr ranitidine continuous infusion or placebo for a maximum of 72 hr. Intragastric pH was recorded via an intragastric pH electrode. Patients with hematemesis, hematochezia, bright red blood, or "coffee ground" nasogastric tube aspirates plus a 5% decrease from baseline in hematocrit were considered to have gastrointestinal bleeding. Ranitidine patients maintained a significantly greater mean pH than placebo patients (placebo 2.2, ranitidine 4.1; P < 0.01). All patients had at least two bleeding risk factors at study entry. No ranitidine patients (0/16) developed bleeding compared with five (5/18) placebo patients (P < 0.05). Ranitidine continuous infusion provided consistent intragastric pH control and significant protection from stress-related upper gastrointestinal tract bleeding in a high-risk patient population.

Twenty-four-hour intragastric pH patterns in ICU patients on ranitidine

Thirty critically ill patients with mixed diagnoses underwent continuous intragastric pH monitoring for 72 hr while confined to a shock/trauma intensive care unit. The first 24 hr were monitored under no specific acid-suppressing therapy (placebo control). During the second and third consecutive 24-hr periods, patients received continuous infusion of intravenous ranitidine in the dose of 6.25 mg/hr and 12.5 mg/hr, respectively. Results of the placebo-control 24-hr study revealed that one third (N = 10) of the patients were gastric acid hyposecretors (24-hr median intragastric pH values above pH 4.0). In the normosecreting group (N = 20), both ranitidine schedules significantly elevated 24-hr median pH values, when compared to placebo (placebo 24-hr median intragastric pH 1.75; ranitidine 6.25 mg/hr 24-hr median intragastric pH 4.625, P < 0.0001; ranitidine 12.5 mg/hr 24-hr median intragastric pH 6.29, P = 0.0099). Five patients (18%) failed to adequately respond to the ranitidine 12.5 mg/hr dose (24-hr median intragastric pH < 4.0). These findings suggest that a significant percentage of intensive care unit patients are not in need of acid-suppressing therapy as prophylaxis against stress-induced ulceration. Conversely, other patients may require more intensive acid-suppressing regimens because of failure to respond to high dose H2-antagonist therapy.

Stress erosive gastritis

Bleeding from stress erosive gastritis continues to be a potential problem in critically ill and injured patients, but fortunately its incidence has decreased dramatically over the last decade. The explanation for this circumstance is probably multifactorial, but clearly relates to our increased knowledge of its pathophysiology. This understanding has led to the routine use of measures to reduce intragastric acidity (luminal acid being a prerequisite for stress ulcer to occur), coupled with improved techniques for the treatment of shock and the accompanying gastric mucosal hypoperfusion (another prerequisite for the formation of stress ulcers). A number of measures have been used to lower intragastric acidity with H2 receptor blockers emerging as the agents of choice to accomplish this goal. In the unlikely event that bleeding occurs despite these prophylactic measures, aggressive medical management will result in cessation of hemorrhage in over 80% of patients. In those few individuals requiring surgery to control bleeding, no operation has emerged as the recognized procedure of choice. Thus, we believe that a conservative operative approach is indicated in this setting and recommend vagotomy and pyloroplasty with oversewing of the bleeding erosions as appropriate therapy for most patients requiring surgical intervention.

Elevated intracranial pressure stimulates gastric contractility in the rat

The gastric contractile response to elevated intracranial pressure (ICP) was studied in conscious rats. Elevation of intracranial pressure to 20 mm Hg was associated with a marked increase in the amplitude of gastric contractions (70-90% over baseline) without any change in contractile frequency (5.2 +/- .5 contractions per min). The increase in contractility continued for 45 min following release of the pressure. Vagotomy completely blocked the increase in gastric contractility seen with elevation in ICP. We conclude that acute elevation of intracranial pressure in rats results in increased force of gastric contractions. The forceful contractions persist despite release of the pressure and the increased contractile force is vagally mediated.

Neurogenic stress ulceration caused by laparotomy under anesthesia plus restraint. The device of a new rat model

We report herein, a new method devised of producing neurogenic stress ulceration in rats. An experimental subarachnoid hemorrhage (SAH) was produced in rats by injecting 0.2 ml of arterial blood from other rats into the cisterna magna. Three days later, the rats were laparotomized for 1 hour under ether anesthesia, followed by restraint for 3 hours in wakefulness. The SAH rats were found to develop stress ulcers (UL-I) in the glandular stomach, which were significantly (p less than 0.001) more marked than those in non-SAH rats. Measurements were performed on gastric acid secretion, an important aggressive factor. It was found that the SAH rats undergoing the laparotomy-restraint stress showed a more marked increase in gastric acid secretion and a more marked reduction in MBF, than the non-SAH rats. The effects of bilateral vagotomy, upper abdominal sympathectomy and bilateral adrenalectomy were examined, and it was revealed that the SAH rats were under the condition of hyperreactivity both in the sympathetic and parasympathetic systems and, on this basis, the laparotomy-restraint stress caused the stress gastric ulceration. In this rat model, the laparotomy stress was applied under anesthesia and any exposure to low temperatures which may have interfered with blood circulation was avoided.

Stress ulcers

Gastric stress ulceration occurs rapidly in patients after severe trauma. However, bleeding from stress ulceration is a rare but very serious complication after trauma and major surgery. Important risk factors for stress ulcer bleeding are shock, especially septic shock, and the development of other components of the multiple system organ failure syndrome. The pathophysiology and treatment of stress ulceration is reviewed in this paper. Prophylaxis is the best form of treatment, and the most effective prophylaxis is optimal resuscitation and intensive care. In addition, pharmacologic prophylaxis, including antacids, sucralfate, or acid secretory inhibitors, has been advocated. Once profuse bleeding has started, measures other than aggressive treatment of shock and sepsis are usually unsuccessful.

[Digestive stress hemorrhage. Physiopathology and prevention]

Lesions of the gastroduodenal mucosa are seen very early on in virtually 100% of patients suffering from organ failure. Bleeding, even if it is only occult, defines acute stress-induced gastrointestinal tract bleeding (SGIB). The rates of SGIB vary according to the inclusion criteria: 13 to 100% microscopic SGIB, 2.3 to 9.5% haemorrhage with blood transfusion and/or shock. Gastrointestinal bleeding does not really influence the death rate of patients with SGIB (0 to 5% increase). Damage to the gastric mucosa may be due to an intraluminal aggression, and/or decreased mucosal and mural defence mechanisms. H+ ions and bile salts are mostly responsible for the former. Physiological quantities of H+ ions may be sufficient, as their abnormal diffusion into the gastric mucosa will reduce the mucosal pH (pHm), which is itself sensitive to microcirculatory modifications and systemic acidosis. There is a good correlation between bleeding and pHm. Bile salts are involved because of the usual increase in frequency and volume of gastric biliary reflux due to stress. Surfactant, mucosal alkaline layer and the microcirculation are all involved in gastric protection. The PGE2 synthetized by the gastric mucosa have a favourable influence on these 3 mechanisms. Changes in microcirculation and hypoxia are the predominant factors involved in stress-induced mucosal damage. The prevention of SGIB relies on the treatment of risk factors, a reduction of intraluminal aggression, and the support and/or stimulation of gastric defence mechanisms. Antacids and anti-H2 drugs aim to neutralize most of the H+ ions, being more efficient than placebo in increasing gastric pH greater than 4, although anti-H2 agents are responsible of a greater number of failures. The non-homogenous character of the patient groups studied and the diagnostic methods, as well as the increasing lack of placebo groups in the published studies make the interpretation of the results rather risky. Antacids and anti-H2 drugs are more efficient than placebo, and equally efficient, in preventing overt SGIB. Efficiency is increased by giving anti-H2 drugs continuously, and antacids hourly. Other agents are thought to protect mucosal cells, probably increasing mucosal defences. Amongst them are the prostaglandins, the most interesting of which are still being investigated, and sucralfate. The latter molecule is as efficient as antacids and anti-H2 drugs, and does not alter gastric pH, so reducing the number of nosocomial pneumonias. Its reduced cost and easy administration make it, at the present time, the treatment of choice of SGIB. The few rare contraindications of sucralfate will justify the infusion of anti-H2 drugs in those patients at risk.

Role of thyrotropin-releasing hormone in stress ulcer formation in the rat

The role of the hypothalamic peptide thyrotropin-releasing hormone in stress ulcer formation was investigated. In experiment 1, TRH was peripherally administered (10 micrograms/kg) to rats subjected to cold-restraint stress and compared to an inactive peptide; in experiment 2, TRH was administered intracerebroventricularly (0.02, 0.1, and 0.5 microgram/kg) to rats with no adjunctive experimental stress; in experiment 3, TRH antiserum was given intracerebroventricularly to rats subjected to stress and compared to normal rabbit serum. When TRH was administered subcutaneously in rats subjected to stress, it significantly aggravated ulcer formation, and this effect was inhibited by atropine and vagotomy. When administered intracerebroventricularly, TRH alone induced, in a dose-dependent fashion, the formation of gastric ulcers. TRH antiserum infused intracerebroventricularly inhibited ulcer formation induced by cold-restraint stress. In conclusion, TRH seems to play a role in stress ulcer formation, possibly by a cholinergic mediated mechanism.

Mechanisms of stress-related mucosal damage

During the last 15 years, there has been a dramatic decline in the incidence of bleeding from stress-related mucosal damage. This decrease probably relates to an increased understanding of those mechanisms responsible for the pathogenesis of stress-related mucosal damage and the application of this knowledge to prophylaxis and treatment. Stress-related bleeding has become less of a clinical problem, in part, because of the development of improved techniques for the treatment of shock and its accompanying gastric mucosal hypoperfusion. The nearly routine use of prophylactic antacid and/or histamine (H2)-receptor antagonist therapy to adequately buffer intragastric acidity is another factor that has minimized the development of stress-related damage. As continued understanding of the mechanisms responsible for stress damage is obtained and therapy applied appropriately, this disease should become a disorder of only historical interest in years to come.

Effect of increased intracranial pressure on gastric acid secretion

The effects of intracranial pressure on gastric acid secretion were studied in 30 rabbits. Intracranial pressure was increased in a graded and controlled fashion using a barostat connected to a cannula in the lateral cerebral ventricle. Eighteen rabbits were studied under urethane anesthesia with a background subthreshold intravenous infusion of bethanechol. Twelve rabbits were studied in the conscious state. Increases in intracranial pressure led to immediate and significant increases in gastric acid output in a dose-related manner in both conscious and anesthetized animals. Serum gastrin levels did not increase in either group of animals. Vagotomy only partially abolished the increase in acid outputs seen with increased intracranial pressure, whereas atropine completely blocked the response. We conclude that increased intracranial pressure causes stimulation of acid secretion by a gastrin-independent cholinergic mechanism that is only partially mediated by the vagus.

Gastric response to severe head injury

We studied the gastric response to severe head injury and multiple trauma in 53 patients admitted to the surgical intensive care unit at the University of Louisville. Twenty-two of the 32 patients with severe head injury could have endoscopy. Each patient had gastritis or duodenitis. Patients with severe head injury had a slightly higher rate of gastric acid secretion than did the other trauma patients without severe head injury, but the difference was not significant. Serum gastrin levels were normal in both groups and did not correlate with intracranial pressure. Pancreatic polypeptide levels were significantly higher in patients with severe head injury compared with the control trauma patients without head injury. Elevations in pancreatic polypeptide may be linked to increases in intracranial pressure. We conclude that erosive gastritis occurs commonly in patients with severe head injury and that severe head injury is associated with a marked increase in pancreatic polypeptide levels in the fasted, nongut-stimulated state. Gastrin levels are within normal limits. Head injury appears to specifically increase pancreatic polypeptide release, probably by influencing autonomic centers in the mid brain. Because the cephalic phase of pancreatic polypeptide release is vagalcholinergic, the data are consistent with the hypothesis that severe head injury increases vagal activity. Participation of vagal adrenergic fibers in this process cannot be excluded.

Gastric blood flow, mast cell degranulation and micromorphology of gastric mucosa following experimental haemorrhagic shock in dogs

Ischaemia of the gastric mucosa in haemorrhagic shock appears to be one of the principal factors underlying acute bleeding from the upper gastrointestinal tract. In the present experimental study on dogs the changes of blood flow in the upper gastrointestinal tract were recorded by direct flow measurement in the pertinent vessels. Fourteen mongrel dogs were subjected to haemorrhagic shock lasting for 3 and 4 h. A decline of 46 per cent cardiac output was observed while coeliac artery blood flow decreased by 40 per cent and gastric artery blood flow by 60 per cent. All stages of stress ulcers were documented by light and electron microscopy. In addition, pronounced degranulation of mast cells preceding major tissue damage was observed. In the light of these findings a cascade of events is thought to be present resulting in the development of stress ulcer.

Effects of antacids, cimetidine, and 16,16-dimethyl prostaglandin E2 on acute gastric erosions in a spinal rat

Acute erosions of the stomach may occur in association with human spinal cord injuries. Erosion of the glandular portion of the stomach also occurs after cervical cord transection in the rat. Reports on the effects of antacids and cimetidine in the prevention of acute "stress" erosions in animals and humans have shown conflicting results. A prostaglandin analog, 16,16-dimethyl prostaglandin E2 (16,16-dmPGE2) has been shown to prevent gastric erosions in rats produced by nonsteroid antiinflammatory compounds. Cimetidine 50 mg/kg (intraperitoneal), 16,16-dmPGE2 10 micrograms/kg (intraperitoneal), and antacid 2 ml (intragastric) were individually given to groups of spinal rats at 0 and 4 hr. 16,16-dmPGE2 and antacid both resulted in significant reduction in mean ulcer length compared to controls after 8 hr (P less than 0.05) whereas cimetidine showed no significant effect, even though cimetidine caused a significant decrease in gastric acid output compared to both 16,16-dmPGE2 and controls (P less than 0.01). It is concluded that cimetidine on this dosage schedule is not effective in the prevention of gastric erosions in a cervical cord section rat model, whereas the ulceroprotective effects of 16,16-dmPGE2 and antacids are significant. It is suggested that the gastric mucosal cells remain vulnerable to injury in the cimetidine-treated spinal rat due to secretory inhibition, but are protected by buffering action of antacids or by "cytoprotective" effects of prostaglandin.

The surgical management of bleeding stress ulcers

The series included 52 patients with acute bleeding stress ulcers of the stomach and duodenum seen at the Mayo Clinic during a 25-year period. All patients underwent operation for control of massive bleeding that was unresponsive to intensive medical therapy. All ulcers were superficial and occurred during clinically stressful circumstances. No patient had a history or findings suggestive of pre-existing peptic ulcer disease or imbibation of ulcerogenic substances. Overall operative mortality was 54%, and this rate seemed to be related to multiple factors acting together; patients with multiple predisposing stress factors and those requiring large transfusion volumes (greater than 17 total units) were at greatest risk of death. Fifty-two patients underwent 60 operative procedures for control of hemorrhage. Of the 60 procedures, 23 (38%) failed to prevent rebleeding. Of the 28 patients who died, six (21%) died of hemorrhage and five (18%) died of hemorrhage as one of many contributing factors. Of eight different procedures performed, near-total to total gastrectomy was the single procedure that was most effective in controlling hemorrhage. The authors support the selection of rapid intervention and generous extirpative surgery once intensive medical measures fail to control hemorrhage.

Prevention of acute gastrointestinal complications after severe head injury: a controlled trial of cimetidine prophylaxis

Cimetidine prophylaxis significantly reduced the risk of gastrointestinal bleeding after severe head injury in this prospective, double-blind clinical trial. Cimetidine effectively reduced both the volume and the acidity of gastric secretions after brain injury without producing adverse side effects. The most common endoscopic finding was superficial, erosive, mucosal lesions in the proximal stomach. Cimetidine prophylaxis was not shown to reduce the incidence of these lesions in this study but did diminish their severity and the likelihood that they would complicate the management of these patients.

Acute gastro-intestinal bleeding in the critically ill patient

Endoscopic studies have shown that all critically ill patients are liable to a degree of stress ulceration. Diffuse erosions appear first in the fundus and then spread to the corpus and antrum within 48 h. Duodenal disease is particularly common in burns patients. Discrete ulceration occurs in most severely injured patients. Mucosal damage is probably initiated by ischaemia but only develops in the presence of acid. Although related to the severity of underlying illness, haemorrhage is unpredictable. Mortality is high and largely unaffected by treatment. Emphasis should therefore be made on prophylaxis. Improved intensive reducing intra-luminal acid by antacid or H2 receptor antagonists appears to be the most effective measure, but controlled studies are required.