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Biomedical subjects

S O Heard

Publications and source records attributed to S O Heard.

At least 37 records · Page 2Linked to original sources
PubMed1999

Continuous measurement of gut pH with near-infrared spectroscopy during hemorrhagic shock.

BACKGROUND: The rate and magnitude of pH changes in the bowel during hemorrhagic shock are greater than those in the stomach, implying that gastric intramucosal pH may not be a reliable indicator of gut perfusion. Here, we evaluate near-infrared spectroscopy (NIRS) to assess bowel pH in a swine shock model. METHODS: Laparotomy was performed to place flow probes, pH microelectrodes, and NIRS probes. Shock was maintained for 45 minutes at a blood pressure of 45 mm Hg, and resuscitation was achieved with shed blood and lactated Ringer's solution to baseline over 60 minutes. RESULTS: Hemodynamic measurements were significantly reduced during shock. Lactic acid peaked during resuscitation and remained elevated. NIRS-measured pH was correlated to electrode-measured pH (R2 = 0.903 [ischemia] and R2 = 0.889 [reperfusion]). Estimated measurement accuracy after subject-specific offset correction was 0.083 pH units during ischemia and 0.076 pH units during reperfusion. CONCLUSION: NIRS determination of small-bowel pH may be a good tool to monitor the adequacy of resuscitation.

Animals↗
PubMed1998

Influence of triple-lumen central venous catheters coated with chlorhexidine and silver sulfadiazine on the incidence of catheter-related bacteremia.

OBJECTIVE: To evaluate the efficacy of triple-lumen central venous catheters coated with a combination product of chlorhexidine and silver sulfadiazine (CSS) in reducing the incidence of local catheter infection and catheter-related bacteremia. DESIGN: Randomized, controlled trial. SETTING: The surgical intensive care units in a university hospital. PATIENTS: All patients who needed central venous catheterization were randomized to receive either an uncoated triple-lumen catheter (n = 157) or a catheter coated with CSS (n = 151). MAIN OUTCOME MEASURE: Catheters were removed when no longer needed or suspected as a cause of infection. The tip and a 5-cm segment of the intradermal portion of the catheter were cultured semiquantitatively. Blood cultures were obtained when clinically indicated. The remaining segment of catheters coated with CSS were cut and incubated on an agar plate with strains of Staphylococcus aureus and Enterococcus. Zone of inhibition was determined 24 hours later. Data were analyzed by survival and logistic multivariate regression methods. RESULTS: Catheters coated with CSS were effective in reducing the rate of significant bacterial growth on either the tip or intradermal segment (40%) compared with control catheters (52%; P = .04). However, there was no difference in the incidence of catheter-related bacteremia (3.8% [uncoated] vs 3.3% [coated]; P = .81). In vitro activity of catheters with CSS against S aureus was evident up to 25 days but activity against Enterococcus dissipated more quickly over time and was absent by day 4. The most common colonizing organisms were coagulase-negative staphylococcus and enterococcus. Variables that were associated with a significant amount of growth on the tip or intradermal segment were a duration of catheterization of longer than 7 days, jugular insertion site, and the absence of a CSS coating. The use of a guidewire when the catheter was removed was associated with a lower risk of significant bacterial growth. CONCLUSIONS: The use of CSS reduces the incidence of significant bacterial growth on either the tip or intradermal segments of coated triple-lumen catheters but has no effect on the incidence of catheter-related bacteremia. In this patient population, catheters coated with CSS provide no additional benefit over uncoated catheters.

Anti-Infective Agents, Local↗
PubMed1998

The use of neuromuscular blocking agents in the emergency department to facilitate tracheal intubation in the trauma patient: help or hindrance?

PURPOSE: The purpose of this study is to examine the relationship between the occurrence of a difficult intubation and (1) the use of neuromuscular blocking agents (NMB) and (2) the presence of airway injuries. It is a retrospective analysis of data from a trauma registry. MATERIALS AND METHODS: Registry records of patients (n = 160) who required emergent endotracheal intubation or establishment of a surgical airway over a 3.5-year period in the emergency department were reviewed. Risk factors for difficult intubations were identified and analyzed using multivariate logistic regression analysis. RESULTS: NMB were used in 75% of patients requiring intubation. Fifteen percent of the intubations were considered difficult. No association was found between the presence of airway injuries and difficult intubations; however, the use of succinylcholine was associated with a lower risk of difficult intubations compared with intubations where a nondepolarizing NMB was used. CONCLUSIONS: The use of succinylcholine may result in fewer difficult intubations in the trauma patient than when a nondepolarizing NMB is used. The presence of airway injuries did not appear to predispose to difficult intubations.

Adult↗
PubMed1998

Endoscopic placement of nasoenteric feeding tubes in critically ill patients: a reliable alternative.

Spontaneous transpyloric passage of nasoenteric feeding tubes is often unsuccessful in critically ill patients due to gastric ileus. The purpose of this study was to evaluate the success rate of endoscopic placement of postpyloric nasoenteric tubes and the time required to achieve goal enteral nutritional support in critically ill patients with gastric ileus. Surgical ICU patients with gastric ileus, documented by recorded high gastric residual volumes via a nasogastric tube, were identified for placement of a nasoenteric postpyloric tube via esophagogastroduodenoscopy (EGD). EGD was performed bedside in the ICU, using intravenous sedation, for placement of a 43-inch (109 cm) 8 French tungsten-weighted nasoenteric tube with an inner stylet into the duodenum, and the tube was advanced as far distally as possible. Abdominal radiograph was obtained to confirm final tube position postprocedure. Enteral feedings were initiated immediately with a full-strength formula and increased to the goal enteral feeding rate as tolerated. Thirty-four patients underwent successful placement of postpyloric nasoenteric tubes by EGD. One procedure was aborted in a patient with adult respiratory distress syndrome (ARDS) who developed hypoxemia with gastric insufflation during the EGD. The mean time to achievement of goal enteral nutritional support was 20.8 hours. Tubes remained in place for a range of 6 to 37 days. Endoscopic placement of postpyloric enteral feeding tubes is highly successful, and allows for prompt achievement of goal enteral nutritional requirements. It has two main advantages: it eliminates the risk of patient travel to radiology for fluoroscopic placement, and allows for earlier initiation of enteral feedings because spontaneous passage of weighted nasoenteric tubes into the duodenum in critically ill patients is often unsuccessful.

Adult↗
PubMed1998

Partial liquid ventilation with perfluorocarbon in the treatment of rats with lethal pneumococcal pneumonia.

BACKGROUND: Partial liquid ventilation with perfluorocarbon is a new therapeutic strategy to treat various lung disorders. The current study was undertaken to determine the efficacy of partial liquid ventilation with a perfluorocarbon (FC-77) in the treatment of pneumococcal pneumonia in rats. METHODS: Male Wistar rats (weight, 275-300 g; n, 75) were infected via direct intratracheal inoculation with ca 10(9) colony-forming units of viable Streptococcus pneumoniae, serotype 3, and 24 h after infection were placed into one of five groups, each containing 15 rats. The groups were (1) no treatment, (2) one intramuscular injection of penicillin G benzathine (200,000 U), (3) partial liquid ventilation with FC-77, (4) partial liquid ventilation with FC-77 and a single intramuscular dose of penicillin G benzathine (200,000 U), and (5) gas ventilation. Animals were observed every 24 h for survival. RESULTS: All untreated or gas-ventilated animals or animals that received only partial liquid ventilation were dead by 7 days. Those receiving only partial liquid ventilation survived longer than untreated controls, but ultimately all succumbed by day 7. Survival was 40% for penicillin-treated rats compared with controls (P < 0.05) and 80% for animals treated with both partial liquid ventilation and penicillin versus antibiotic alone (P < 0.05). CONCLUSIONS: These observations suggest that partial liquid ventilation with perfluorocarbon in combination with antibiotic administration may be an effective therapeutic modality in pneumococcal pneumonia.

Animals↗
PubMed1998

Effect of prophylactic administration of recombinant human granulocyte colony-stimulating factor (filgrastim) on the frequency of nosocomial infections in patients with acute traumatic brain injury or cerebral hemorrhage. The Filgrastim Study Group.

OBJECTIVE: To determine whether the use of prophylactic recombinant human granulocyte colony-stimulating factor (filgrastim) reduces the frequency of nosocomial infections in patients with either acute traumatic brain injury or cerebral hemorrhage. DESIGN: Randomized, placebo-controlled, double-blind, multicenter phase II study. SETTING: Intensive care units of seven medical centers. PATIENTS: Patients with either acute traumatic brain injury or cerebral hemorrhage who were intubated within 6 hrs of admission and who were expected to be ventilated for >72 hrs. INTERVENTIONS: Patients were randomized to receive daily subcutaneous injections of placebo (n = 21) or one of two doses of filgrastim (75 microg [n = 20] or 300 microg [n = 20]) for 10 days or until the absolute neutrophil count was >75,000 cells/mm3 or until extubation. MEASUREMENTS AND MAIN RESULTS: End points included increase in absolute neutrophil count, safety of filgrastim, and frequency of nosocomial infections (pneumonia, bacteremia, and urinary tract infection). Filgrastim caused a dose-dependent increase in absolute neutrophil count. There were no differences in the frequency of pneumonia or urinary tract infection; however, there was a dose-dependent decrease in the frequency of bacteremias (p < .05). Adverse events were similar among the three groups. There was one case of acute respiratory distress syndrome in the placebo group. CONCLUSION: In this patient population, use of filgrastim was safe and the agent appeared to reduce the risk of primary bacteremias but had no beneficial effects on mortality, length of stay, or other nosocomial infections.

APACHE↗
PubMed1997

Nitric oxide does not mediate lipopolysaccharide-induced myocardial depression in guinea pigs.

OBJECTIVE: To determine the role of nitric oxide as a mediator of lipopolysaccharide-induced myocardial depression. DESIGN: Prospective, controlled study. SETTING: University research laboratory. SUBJECTS: Male and female Hartley guinea pigs. INTERVENTIONS: Animals (n = 97) received intraperitoneal injections of either saline or Escherichia coli lipopolysaccharide (2 mg/kg). Some (n = 5) animals received two injections of dexamethasone before lipopolysaccharide. Left atria were harvested 6 hrs (n = 20) or 16 hrs (n = 77) later and placed in a tissue bath with Krebs-Henseleit buffer. Contractile tension was measured in the presence or absence of two inhibitors of nitric oxide synthase (NG-nitroarginine [NNA] or aminoguanidine). Atrial and serum nitrite/ nitrate and atrial cyclic guanosine monophosphate (cGMP) concentrations were assayed. MEASUREMENTS AND MAIN RESULTS: Lipopolysaccharide caused significant atrial contractile depression at 16 hrs but not 6 hrs compared with control animals. Neither NNA nor aminoguanidine reversed the depression in atrial function. In contrast, exposure of control atria to NNA worsened contractile function. There were no significant differences between control and lipopolysaccharide-treated animals in atrial and serum nitrite/nitrate and atrial cGMP concentrations. CONCLUSIONS: Nitric oxide does not mediate lipopolysaccharide-induced myocardial depression in this animal model. Basal concentrations of nitric oxide may be important since NNA worsened contractile function in control atria.

Animals↗
PubMed1997

Diagnosis of triple-lumen catheter infection: comparison of roll plate, sonication, and flushing methodologies.

In a recent clinical trial, 248 triple-lumen catheters were removed from patients in an intensive care unit, and their tip and subcutaneous segments were cultured by both the sonication and roll plate methods; for 191 of these catheters, flush cultures of all three catheter lumens were also performed. Previously published quantitative endpoints were used to define significant catheter colonization. By using a composite index as a definition of colonization (any of the seven types of cultures meeting quantitative criteria), sonication of the subcutaneous segment was the most sensitive at detecting colonization (58%), followed by sonication of the catheter tip (53%). Sonication of both the subcutaneous and tip segments was 20% more sensitive than sonication of an adjacent catheter segment by the roll plate method (P < 0.05). The greater sensitivity of the sonication method could be attributed to its greater ability than the roll plate method to detect catheter lumen colonization (82 versus 57%, respectively; P = 0.01). A greater number of positive catheter segment cultures were found for colonized catheters from patients with associated bacteremia than for colonized catheters from patients without bacteremia (57 versus 37%; P = 0.004), making any culture method more likely to identify them. For catheters with significant colonization of only one site, the localization was as follows: 36.7% subcutaneous segment, 36.7% catheter lumen, and 26.6% tip segment. These findings suggest that the current practice of culturing a single segment of a central vascular catheter is inadequate and needs to be reexamined. They further suggest that initial colonization of the catheter lumen and tip segments may be more important than previously thought and may require a change in thinking of strategies designed to prevent catheter infection.

Bacteremia↗
PubMed1997

Spontaneous splenic rupture following administration of granulocyte colony-stimulating factor (G-CSF): occurrence in an allogeneic donor of peripheral blood stem cells.

Granulocyte colony-stimulating factor (G-CSF) has been used to improve granulocyte count in chronic neutropenia and myelodysplasia, to minimize the incidence and duration of neutropenia during conventional chemotherapy, and to mobilize peripheral blood stem cells prior to leukapheresis for use in autologous and allogeneic marrow transplantation. The most common toxicity is bone pain, and other reactions such as inflammation at the site of injection have also occurred. In patients with chronic neutropenia, splenomegaly has been described with long-term use, and extramedullary hematopoiesis has also been reported. However, thus far, no life-threatening sequelae of these effects are found in the literature. We now describe a case of spontaneous splenic rupture four days following a six-day course of G-CSF therapy in an allogeneic donor of peripheral blood stem cells.

Acute Disease↗
PubMed1996

A phase III, multicenter, open-label, randomized, comparative study evaluating the effect of sevoflurane versus isoflurane on the maintenance of anesthesia in adult ASA class I, II, and III inpatients.

STUDY OBJECTIVE: To compare the clinical efficacy and safety of sevoflurane and isoflurane when used for the maintenance of anesthesia in adult ASA I, II, and III inpatients undergoing surgical procedures of at least 1 hour's duration. DESIGN: Phase III, randomized, open-label clinical trial. SETTING: 12 international surgical units. PATIENTS: 555 consenting inpatients undergoing surgeries of intermediate duration. INTERVENTIONS: Subjects received either sevoflurane (n = 272) or isoflurane (n = 283) as their primary anesthetic drug, each administered in nitrous oxide (N2O) (up to 70%) and oxygen (O2) after an intravenous induction using thiopental and low-dose fentanyl. The concentration of volatile drug was kept relatively constant but some titration in response to clinical variable was permitted. Comparison of efficacy was based on observations made of the rapidly and ease of recovery from anesthesia and the frequency of untoward effects for the duration of anesthesia in the return of orientation. Safety was evaluated by monitoring adverse experiences, hematologic and non-laboratory testing, and physical assessments. In 25% of patients (all patients 171 both treatment groups at selected investigational sites), plasma inorganic fluoride concentrations were determined preoperatively, every 2 hours during maintenance, at the end of anesthesia, and at 1, 2, 4, 8, 12, 24, 48, and 72 hours postoperatively. MEASUREMENTS AND MAIN RESULTS: Emergence, response to commands, orientation, and the first request for postoperative analgesia were all more rapid following discontinuation of sevoflurane than following discontinuation of isoflurane (sevoflurane, 11.0 +/- 0.6, 12.8 +/- 0.7, 17.2 +/- 0.9, 46.1 +/- 3.0 minutes, respectively, versus isoflurane, 16.4 +/- 0.6, 18.4 +/- 0.7, 24.7 +/- 0.9, 55.4 +/- 3.2 minutes). The incidence of adverse experiences was similar for sevoflurane and isoflurane patients. Forty-eight percent of patients on the sevoflurane group had no untoward effect versus 39% in the isoflurane group. Three patients who received sevoflurane had serum inorganic fluoride levels 50 microM/I. or greater though standard tests indicated no evidence of associated renal dysfunction. CONCLUSION: Sevoflurane anesthesia, as compared with isoflurane, may be advantageous in providing a smoother clinical course with a more rapid recover.

Adult↗
PubMed1996

Transnasal insertion of percutaneous endoscopic gastrostomy in a patient with intermaxillary fixation: case report.

We describe successful placement of a percutaneous endoscopic gastrostomy via the transnasal approach in a patient who required intermaxillary fixation for an open mandible fracture, and required enteral nutrition for chronic respiratory failure and traumatic brain injury. This method may be useful in other cases where the transoral route is not available for endoscopic insertion of enterostomy tubes.

Adult↗
PubMed1996

Gamma radiation-sterilized, triple-lumen catheters coated with a low concentration of chlorhexidine were not efficacious at preventing catheter infections in intensive care unit patients.

In a randomized, double-blind trial, gamma radiation-sterilized, chlorhexidine-coated triple-lumen catheters were compared with uncoated control catheters for their ability to prevent catheter infection in 254 intensive care unit patients. The chlorhexidine coating was not efficacious, and a rabbit model demonstrated that reduction of chlorhexidine activity by gamma radiation sterilization was the likely explanation for the failure.

Bacteremia↗
PubMed1995

The role of platelet-activating factor in lipopolysaccharide-induced myocardial depression in guinea pigs.

PURPOSE: To determine if platelet-activating factor (PAF) is a key mediator of lipopolysaccharide (LPS)-induced myocardial depression in guinea pigs. METHODS: Hartley guinea pigs of either sex received intraperitoneal (IP) injections of either vehicle (n = 45) or one of three chemically dissimilar PAF receptor antagonists (n = 38) followed 30 to 60 minutes later by IP injections of either saline (0.8 mL, n = 33) or LPS (2 to 4 mg/kg, n = 50). Left atria (LA) were harvested 16 hours later, suspended in Krebs-Henseleit buffer and attached to force-displacement transducers. Starling and force-frequency curves, contractile function in the potentiated and resting states, and inotropic response to either isoproterenol or phenylephrine were measured. RESULTS: LPS caused a significant reduction in LA contractile function. Two of the three PAF receptor antagonists failed to ameliorate LPS-induced alterations in cardiac function. The third antagonist, SR27417, was approximately 50% effective in preventing LA contractile dysfunction. However, this beneficial response appeared to be caused by a primary inotropic effect of SR27417 because LA from animals treated with SR27417 and saline showed significantly higher contractile function compared with LA from animals treated with vehicle and saline. In vitro tests confirmed this. Some LA from LPS-treated animals exhibited reduced contractile responses when in the potentiated state, a sign of impaired calcium release from the sarcoplasmic reticulum (SR). The response of LA from endotoxic animals to isoproterenol was unchanged compared with controls whereas it was markedly impaired to phenylephrine. Use of SR27417 failed to improve this abnormal response. CONCLUSIONS: PAF does not appear to be a primary mediator of LPS-induced myocardial depression in guinea pigs. LPS may impair SR calcium release thereby causing cardiac dysfunction.

Animals↗
PubMed1995

Asymptomatic deep venous thrombosis in the trauma patient: is an aggressive screening protocol justified?

The incidence and sequelae of deep venous thrombosis (DVT) in trauma patients are unclear because the majority of patients who develop DVT are asymptomatic. This study evaluated the incidence, risk factors, and efficacy of prophylaxis for DVT in trauma patients over a 5-year period. Trauma patients at high risk for DVT were evaluated biweekly with lower extremity venous duplex scans. The DVT prophylaxis was instituted on admission with low-dose heparin therapy and pneumatic compression. The incidence of asymptomatic DVT identified by duplex screening was 10% (45 of 458); one pulmonary embolus occurred. Five variables were significant from bivariate and multiple logistic regression analysis: age (p = 0.005), Injury Severity Score (p = 0.005), length of stay (p = 0.004), Trauma and Injury Severity Score (p = 0.01), and spinal injury (p = 0.014). This analysis documents that trauma patients with these risk factors are at increased risk for the development of asymptomatic DVT, despite prophylaxis, and warrant surveillance with venous duplex sonography.

Adult↗
PubMed1994

An evaluation of the hemodynamic effects of HA-1A human monoclonal antibody.

OBJECTIVES: We sought to determine whether there might be acute changes in hemodynamics attributable to HA-1A, a monoclonal antibody to endotoxin, in patients with presumed Gram-negative sepsis. DESIGN: Post hoc analysis of a multicenter, randomized, double-blind, placebo-controlled study. PATIENTS: A total of 543 patients with severe sepsis presumed to be caused by Gram-negative bacteria who were enrolled in a clinical trial to evaluate the efficacy and safety of HA-1A human monoclonal antibody. INTERVENTIONS: Patients were randomly assigned to receive either 100 mg of HA-1A or placebo. MEASUREMENT AND MAIN RESULTS: Patients were grouped by the study drug, HA-1A, or placebo, and the presence or absence of Gram-negative bacteremia. Hemodynamic variables were monitored from before, until 72 hrs after infusion of the study drug. For the entire study population (n = 543), no changes over time attributable to study drug were noted in the mean arterial pressure (p > .19), heart rate (p > .53) or the need for vasopressor administration (p > .62). One hundred ninety-seven patients underwent pulmonary artery catheterization and had hemodynamic data available from before the infusion of HA-1A or placebo until at least 12 hrs after infusion. Evaluating all 197 patients on an intent to treat basis demonstrated no significant differences over time in cardiac index (p > .15), oxygen delivery index (p > .43), or left ventricular stroke work index (p > .48) between patients who received HA-1A and those patients receiving placebo. Grouping patients by the presence of Gram-negative bacteremia and study drug received also failed to demonstrate any significant difference attributable to HA-1A in mean arterial pressure (p > .54), heart rate (p > .84), cardiac index (p > .13), oxygen delivery index (p > .05), or left ventricular stroke work index (p > .48) between populations. CONCLUSION: There is no apparent relationship between the administration of HA-1A, the presence of Gram-negative bacteremia, and hemodynamic profiles over the 72-hr study period.

Antibodies, Monoclonal↗