Cimetidine and the potential risk of postoperative sepsis

Effects of gastric acidity on peristomal infection after percutaneous endoscopic gastrostomy placement

Peristomal infection is a common complication following percutaneous endoscopic gastrostomy (PEG) placement. This study investigated the effect of gastric acidity on peristomal infection, including type of bacteria and the relationship between bacteria cultured from the oropharynx and PEG tube site. Sixty-seven patients with dysphagia underwent PEG placement at Otaki Hospital between 1998 and 2001. Gastric acidity was evaluated by 24h pH monitoring. Patients were observed for peristomal infection for two weeks after PEG placement, with specimens collected from the oropharynx and PEG tube site. Twenty-one (31.3%) of the patients who had undergone PEG insertion developed peristomal infections. Of 52 patients who were not colonised with meticillin-resistant Staphylococcus aureus (MRSA) in the oropharynx, 11 cases (21.2%) developed peristomal infection. The median gastric pH of infected patients (11 cases) was 5.05+/-2.55 (mean+/-SD) and in patients without infection (41 cases) it was 3.06+/-1.83 (P=0.019). Peristomal infection developed in 66.7% (10/15) of patients carrying MRSA compared with only 21.2% (11/52) of patients who were not colonised by MRSA (P<0.001). The incidence of peristomal infection was affected by gastric acidity and the presence of MRSA in the oropharynx.

Hydrogen and methane gases are frequently detected in the stomach

AIM: To investigate the incidence of bacterial overgrowth in the stomach by using a new endoscopic method in which intragastric hydrogen and methane gases are collected and analyzed.

METHODS: Studies were performed in 490 consecutive patients undergoing esophagogastroscopy. At endoscopy, we intubated the stomach without inflation by air, and 20 mL of intragastric gas was collected through the biopsy channel using a 30 mL syringe. Intragastric hydrogen and methane concentrations were immediately measured by gaschromatography. H pylori infection was also determined by serology.

RESULTS: Most of intragastric hydrogen and methane levels were less than 15 ppm (parts per million). The median hydrogen and methane values (interquartile range) were 3 (1-8) ppm and 2 (1-5) ppm, respectively. The high hydrogen and methane levels for indication of fermentation were decided if the patient had the values more than 90 percentile range in each sample. When a patient had a high level of hydrogen or methane in one or more samples, the patient was considered to have fermentation. The overall incidence of intragastric fermentation was 15.4% (73/473). Intragastric methane levels were higher in the postoperative group than in other groups. None of the mean hydrogen or methane values was related to H pylori infection.

CONCLUSION: Hydrogen and methane gases are more frequently detected in the stomach than expected, regardless of the presence of abdominal symptoms. Previous gastric surgery influences on the growth of methane-producing bacteria in the fasting stomach.

Gastric juice: a barrier against infectious diseases

All vertebrates produce gastric acid. Its main function is inactivation of ingested microorganisms. The majority of microbiological pathogens ingested never reaches the intestine because of the gastric barrier. Although gastric hypochlorhydria is fairly common due to atrophic gastritis, gastric surgery or use of inhibitors of gastric acid secretion, the resulting susceptibility to infection has not been studied extensively. Drug-induced blockade of acid secretion leads to gastrointestinal bacterial overgrowth; the clinical significance of this is still controversial. Gastric acidity is known to protect against non-typhoid salmonellosis and cholera and it is suspected that it protects against several parasitic diseases as giardiasis and strongyloides. There is a lack of studies focusing on the impact of the gastric acidic barrier on viral infections. Concerning prion infections only a single study has been performed, demonstrating a possible role of gastric acidity in the protection against foodborne prion disease in mice. The combination of malnutrition and hypochlorhydria may contribute to the high prevalence of gastrointestinal infections in developing countries. Further studies are needed to evaluate the clinical consequences of impaired gastric acidity with respect to susceptibility to infections.

The effects of cimetidine, ranitidine, and famotidine on human neutrophil functions

Neutrophil functions, which play an important role in the antibacterial host defense system, are inhibited by various anesthetics and surgical procedures. Histamine H2-receptor antagonists are perioperatively used as a prophylaxis against acid aspiration syndrome or stress ulceration. We examined the effect of cimetidine, ranitidine, and famotidine, at clinically relevant concentrations and at 10 and 100 times this concentration, on several aspects of human neutrophil function using an in vitro system. The three H2-receptor antagonists did not impair neutrophils' chemotaxis or phagocytosis. Cimetidine and famotidine inhibited superoxide (O2-) and hydrogen peroxide (H2O2) production of the neutrophils in a dose-dependent manner, although the inhibitory effects were minimal. In contrast, ranitidine failed to change O2- or H2O2 production of neutrophils. The three H2-receptor antagonists did not scavenge these reactive oxygen species generated by the xanthine-xanthine oxidase system. The increase in intracellular calcium concentrations in neutrophils by a stimulant were dose-dependently attenuated with cimetidine or famotidine. This decreasing effect of the drugs on [Ca2+]i in neutrophils may represent one of mechanisms responsible for inhibition of reactive oxygen species generation.

IMPLICATIONS

Neutrophils play a pivotal role in the antibacterial host defense system and tissue injury. We found that cimetidine and famotidine slightly reduced the O2- or H2O2 production of neutrophils in a dose-dependent manner, although ranitidine failed to do so. At least ranitidine does not seem to have any deleterious effect on neutrophil function, which is clearly an important consideration in its use in severely ill patients.

Gastric alkalinization, pneumonia, and systemic infections: the controversy

BACKGROUND

Gastric alkalinization has been suspected as a cause of pneumonia in critically ill patients. Although meta-analysis of the available data confirms an association between the administration of antacids/H2-antagonists and the risk of pneumonia, controversy remains whether stress ulcer prophylaxis with sucralfate reduces the risk of pneumonia. We hypothesized that the conflicting study results may be due to differences in patient population and general treatment regimens.

RISK FACTORS

Microbiological studies have shown that a gastric pH > 4 is crucial for overgrowth of gastric gram-negative but not gram-positive bacteria. Sucralfate mainly influences the growth of gram-negative bacteria. Thus, in patient groups with a high frequency of gram-positive pneumonia, preservation of gastric acidity does not influence the pneumonia rate. Since 40-60% of critically ill patients show gastric pH values > 4 even without administration of acid-neutralizing agents, an increased risk of nosocomial pneumonia with antacids/H2-antagonists can only be expected if these agents substantially increase the frequency of patients with gastric pH > 4. No influence of stress ulcer prophylaxis on the pneumonia rate can be expected in patients on enteral nutrition, especially if administered continuously. In non-ventilated patients or in those with a short duration of ventilation no significant influence of stress ulcer prophylaxis on nosocomial pneumonia rate can be expected. The same is true for patient groups where regurgitation of gastric content is prevented, e.g. head-up position in neurosurgical patients. Furthermore, in patient groups with primary lung injury nosocomial pneumonia occurs due to specific pathomechanisms, e.g. lung contusion or inhalation injury. Based on these factors we have developed a scoring system and have performed a regression analysis between the sum of the risk scores and the odds ratio of nosocomial pneumonia of all available stress ulcer studies dealing with nosocomial pneumonia.

RESULTS

A highly significant correlation (p < 0.0001) could be demonstrated between the sum of the risk score and the odds ratio for pneumonia. An increased risk of nosocomial pneumonia due to stress ulcer prophylaxis with antacids/H2-antagonists occurred in patient groups with a risk score of > or = 2.

CONCLUSIONS

This analysis supports the hypothesis that gastric alkalinization significantly increases the risk of nosocomial pneumonia in long-term ventilated patients. However, this analysis also shows that only specific subgroups of patients benefit from acid-independent stress ulcer prophylaxis relative to nosocomial pneumonia. Furthermore, recent experimental and clinical studies support the hypothesis that gastric alkalinization may increase the risk of systemic infections and that sucralfate may have significant protective effects.

[Antibiotic prophylaxis in gastroduodenal surgery]

The incidence of postoperative wound infections is increased up to 35% after gastroduodenal surgery, when gastric motility and acidity are decreased, as in case of gastric ulcer or cancer, obstruction, bleeding, antacid therapy. The endogenous flora contaminating the operative-site consists of organisms of the oropharynx and the jejunum and includes anaerobes like bacteroides, aerobes like streptococci, staphylococci, E. coli. Antimicrobial prophylaxis is therefore indicated in these high risk patients. All groups of antibiotics have been used, however 1st and 2nd generation cephalosporins are the most effective. A single dose given intravenously just before anaesthesia is recommended, a second dose is advisable intraoperatively when surgery is prolonged or massive blood loss occurs. Antibiotic prophylaxis is also recommended in gastric bypass surgery for obesity, but remains controversial for percutaneous endoscopic gastrotomy.

Nasogastric intubation and elective abdominal surgery

The use of nasogastric tubes after elective abdominal surgery remains standard practice for many surgeons. Such tubes, however, cause much discomfort and are associated with significant morbidity. This paper reviews the arguments for and against nasogastric intubation, and finds little evidence to support its continued routine use.

Cimetidine: an immunomodulator

Suppressor T lymphocytes possess histamine2 (H2) receptors and contribute significantly to the function of the immune system. Experimentally, cimetidine, an H2-receptor antagonist, has been shown to enhance a variety of immunologic functions both in vivo and in vitro because of its inhibitory effects on suppressor-cell function. Successful tumor immunotherapy, as well as some protection from infection, has been reported in experimental animals. Patients receiving cimetidine have been shown to exhibit enhanced cell-mediated immunity as evaluated by increased response to skin-test antigens, restoration of sensitivity following development of acquired tolerance, and increased responses of lymphocytes to mitogen stimulation. Preliminary reports also indicate that cimetidine may offer therapeutic benefits for patients with Varicella zoster and Herpes simplex infections, as well as those suffering from mucocutaneous candidiasis and common variable hypogammaglobulinemia. These immunoregulatory effects are dose-related but are not always consistent. Because of its inhibitory effect on suppressor function, cimetidine treatment may be deleterious in patients with organ transplant and autoimmune disorders. Cimetidine should be used as an immunomodulator on an experimental basis only.

Septic complications in relation to factors influencing the gastric microflora in patients undergoing gastric surgery

Postoperative septic complications and micro-organisms found in primary infections were studied in 750 gastric operations performed between 1972 and 1986. The overall rate of primary infections was 23%. The infection rates were related to the diagnosis and to factors that could influence the colonization of the stomach. No significant differences in the rates of postoperative infections were found between patients who had received preoperative antibiotic prophylaxis and those who had not. In all groups of patients, aerobic and anaerobic gram-positive and gram-negative bacteria and yeasts were isolated in primary infections. Enterobacteriaceae, enterococci and Bacteroides fragiis were more frequent in patients with gastric bleeding or carcinoma.

Cimetidine does not impair lung host defense in experimental pneumococcal pneumonia

Normal CD-1 mice were administered cimetidine (400 mg/kg/24 h) or control solution by subcutaneous injection and inoculated intratracheally with type S Streptococcus pneumoniae in order to evaluate the effect of the histamine H2-receptor antagonist on pulmonary antibacterial mechanisms. Therapy with cimetidine did not influence overall survival rates. After challenge with 1 X 10(6) colony-forming units (cfu), the eradication of viable pneumococci from the lungs (pulmonary clearance), the generation of a local inflammatory response, and the prevalence of bacteremia were similar in both study groups. Cimetidine also failed to influence pulmonary antimicrobial systems after challenge with lower bacterial inocula (5 X 10(4) and 5 X 10(3) cfu). Further, treatment with cimetidine had no effect on the in vivo phagocytic or bactericidal activity of resident murine alveolar macrophages. Thus, in this animal model, cimetidine does not disrupt host defenses of the lower respiratory tract.

The human intestinal microflora

The major host defense mechanisms against bacterial overgrowth in the small bowel are the normal propulsive activity of the bowel itself and gastric acid secretion. Microbial interactions are a major factor in regulating the indigenous bacterial flora. Studies of the bacterial enzymes of the gut suggest that changes in diet may lead to marked changes in the colonic flora. Antibiotics affect the composition of the colonic microflora. The microflora also influence the degradation of mucin, the conversion of urobilin to urobilinogen, of cholesterol to coprostanol, and the production of short chain fatty acids. Current interests are focused on the bacterial flora of tropical sprue, the role of bacteria in colorectal cancer, and the involvement of intestinal microflora in the enterohepatic circulation of sex steroid hormones.

Alteration of normal gastric flora in critical care patients receiving antacid and cimetidine therapy

One hundred fifty-three critical care patients with documented cimetidine and antacid use were prospectively studied with serial gastric pH determinations and semiquantitative gastric fluid cultures. This study documents the abnormal gastric colonization of patients with therapeutically altered gastric acidity by hospital acquired gram negative rods (GNR). Three hundred twenty-four gastric fluid cultures from 153 patients revealed 152 (47%) positive cultures for GNR, 78 (24%) sterile specimens, and 94 (29%) positive for mixed oropharyngeal flora. One hundred forty (59%) of the 236 cultures at a pH of 4 or greater were positive for GNR. In contrast, only 12 (14%) of the 88 cultures at a pH of less than 4 were positive for GNR (p less than .001). Forty-six (52%) of 88 cultures at a pH of less than 4 were sterile as compared to only 32 (14%) of 236 sterile cultures at a pH of 4 or greater (p less than .001). At low pH, cultures are predominantly sterile and at a pH of 4 or greater the flora dramatically changes to hospital acquired GNR. This artificially maintained reservoir of gram negative rods in the critically ill patient is a potential reservoir of organisms causing nosocomial bacteremia or pneumonia in this high risk population.

Potential hazards of hypochlorhydria in the treatment of peptic ulcer

The introduction of ulcer-healing drugs that do not induce hypochlorhydria--the main aim of therapy thus far--has led to the consideration of the possible disadvantages of acid secretion inhibition. Potential dangers are that micro-organisms destroyed by the normal stomach survive and proliferate in the stomach and small intestine. The incidence of gastric cancer is higher in pernicious anemia and after partial gastrectomy. It has been suggested that the intragastric bacteria may convert dietary nitrate into nitrite that may then be nitrosated to carcinogenic N-nitroso compounds. The third potential hazard is the development of stagnant loop syndrome in patients treated with H2 antagonists. In a double-blind randomised trial of colloidal bismuth subcitrate (CBS) versus cimetidine in duodenal ulcer, gastric juice was aspirated for pH measurement. There was a significant increase in the total number of bacteria isolated during cimetidine treatment (P less than 0.01) and an increase in nitrate-reducing organisms (P less than 0.05), but no change in the CBS group. It is concluded that there may be advantages in using ulcer-healing drugs that do not reduce H+ concentration.

Prophylactic postoperative nasogastric decompression. A prospective study of its requirement and the influence of cimetidine in 200 patients

To determine the need for prophylactic nasogastric decompression following laparotomy and the influence of cimetidine, 200 consecutive patients who underwent major abdominal procedures were prospectively randomized into one of four limbs: no tube-placebo; no tube-cimetidine; tube-placebo; and tube-cimetidine. Patients were evenly distributed among these groups with respect to age, sex, alcohol and tobacco use, previous operations, and types of operations. There was significantly longer time until passage of flatus, bowel movement, and cessation of intravenous fluids in the tube group (p less than 0.05). Duration of postoperative stay increased from 11.4 to 14.1 days in the intubated patients (p less than 0.05). There was also significantly more pain with and frequency of swallowing, and nose/throat discomfort in the tube group. Nasogastric tubes reduced the incidence of vomiting from 28 in the no-tube group to 10 in the tube group (p less than 0.05), but most had only one or two episodes. Cimetidine did not affect either the incidence of vomiting or the duration of intubation, but was associated with a significant increase in pneumonias (p less than 0.05). Five patients without tubes initially, and seven patients with tubes had to have them inserted or replaced for vomiting or abdominal distention, which occurred equally in the placebo and cimetidine limbs. There were no cases of aspiration pneumonia, gastric dilatation, or wound dehiscence in the trial, and the four anastomotic leaks were divided equally between the tube and no-tube groups. The results indicated that prophylactic decompression was unnecessary in most patients and associated with increased morbidity and delayed return of gastrointestinal function. Cimetidine lowered nasogastric output on the first postoperative day (p less than 0.05), but did not prevent vomiting.

Twice-daily cimetidine does not increase gastric bacterial flora

Thirty patients with peptic ulcer (20 duodenal, 10 gastric) underwent glucose-hydrogen (H2) breath tests before and after 6 weeks treatment with cimetidine, 400 mg twice daily. For the group as a whole, basal breath H2 and integrated H2 output over a 2.5 hr test period was unchanged by cimetidine treatment. We conclude that there was no evidence of significant gastric bacterial colonization following twice daily cimetidine treatment.

Effect of cimetidine and antacid on gastric microbial flora

The effect of a standard regimen of cimetidine on the gastric flora of 20 male volunteers was studied in a double-blind manner and compared with the effects of a standard antacid regimen. Postprandial microbial titers in gastric aspirates were significantly higher at 4, 8, and 16 weeks of therapy in subjects taking antacids and at 4 weeks in subjects taking cimetidine when compared with their pretreatment titers. Although not significant, there was a tendency for fasting microbial titers to be higher in subjects receiving cimetidine as compared with pretreatment titers. The higher titers were primarily related to increases in survival of mouth flora (viridans streptococci and Neisseria spp.); Enterobacteriaceae and other nitrate-reducing organisms were unusual isolates. There was no significant difference in the total titers or types of organisms isolated when subjects taking cimetidine were compared with those taking antacid.