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Biomedical subjects

S O Heard

Publications and source records attributed to S O Heard.

At least 19 recordsLinked to original sources
PubMed2006

Report of a National Conference on Donation after cardiac death.

A national conference on organ donation after cardiac death (DCD) was convened to expand the practice of DCD in the continuum of quality end-of-life care. This national conference affirmed the ethical propriety of DCD as not violating the dead donor rule. Further, by new developments not previously reported, the conference resolved controversy regarding the period of circulatory cessation that determines death and allows administration of pre-recovery pharmacologic agents, it established conditions of DCD eligibility, it presented current data regarding the successful transplantation of organs from DCD, it proposed a new framework of data reporting regarding ischemic events, it made specific recommendations to agencies and organizations to remove barriers to DCD, it brought guidance regarding organ allocation and the process of informed consent and it set an action plan to address media issues. When a consensual decision is made to withdraw life support by the attending physician and patient or by the attending physician and a family member or surrogate (particularly in an intensive care unit), a routine opportunity for DCD should be available to honor the deceased donor's wishes in every donor service area (DSA) of the United States.

Adolescent↗
PubMed2001

Naloxone blocks transferred preconditioning in isolated rabbit hearts.

We have shown that the cardioprotective benefits of ischemic preconditioning (PC) can be transferred from PC to virgin acceptor hearts via coronary effluent transfusion, implicating the presence of hormonal preconditioning factor(s). Using isolated buffer-perfused rabbit hearts, our aims were to: (1) determine whether the protective factor(s) could be concentrated and recovered by reverse phase chromatography and (2) whether opioid receptor activation contributes to this transferred cardioprotection. Material released into the coronary effluent during PC ischemia/reperfusion or normoxic perfusion was concentrated by reverse phase chromatography. In phase one, hearts received no intervention (controls), PC ischemia, concentrate generated from normoxic hearts (normoxic acceptors) or concentrate from PC hearts (PC acceptors). All hearts underwent 40 min of global ischemia, and area of necrosis (AN) was delineated by tetrazolium staining. In phase two, three additional groups of hearts (control, PC and PC acceptors) received the opioid antagonist naloxone (2 microM) throughout the intervention phase. Treatment with normoxic concentrate had no effect on infarct size: (AN: normoxic acceptors 39+/-8%; control 42+/-8%). In contrast, treatment with PC concentrate evoked cardioprotection equivalent to that afforded by conventional PC (AN 19+/-5% and 21+/-6% respectively P<0.05 v control). Naloxone had no effect on infarct size in controls, and did not inhibit preconditioning. However, naloxone abrogated the protection achieved by transfer of PC concentrate (AN: 44+/-7%). These results indicate that PC concentrate evokes a cardioprotective effect via a mechanism requiring an intact opioid receptor system.

Animals↗
PubMed2001

Application of fiberoptic sensors for the study of hepatic dysoxia in swine hemorrhagic shock.

OBJECTIVES: To determine whether the simultaneous measurement of tissue pH, Pco2, and Po2 with a multiple-parameter fiberoptic sensor can be used to indicate the onset of hepatic dysoxia, to determine critical values, and to assess their use in predicting negative outcomes. DESIGN: Prospective animal study. SETTING: University research laboratory. SUBJECTS: Fourteen Yorkshire swine. INTERVENTIONS: Hemorrhagic shock (n = 11) was induced over 15 mins to lower systolic blood pressure to 40 mm Hg and was maintained for 30, 60, or 90 mins. Resuscitation was achieved with shed blood and warm saline to maintain mean pressure >60 mm Hg for 120 mins. Sham animals (n = 3) were subjected to 90 mins of sham shock, followed by a 120-min recovery period. MEASUREMENTS AND MAIN RESULTS: The multiple-parameter sensor continuously measured tissue pH, Pco2, and Po2. pH and Pco2, indicators of anaerobic metabolism, were plotted against tissue Po2. All shocked animals, but no sham animals, showed a biphasic relationship between Po2 and both pH and Pco2. Curves were fit to both an exponential and a dual-line linear function to determine critical values for Po2, pH, and Pco2. The length of time the animal was dysoxic was evaluated as a predictor of negative outcome. Critical values determined from the exponential models were more sensitive indicators of negative outcome than values determined from the linear model and more sensitive than arterial lactate and tonometric intramucosal pH and Pco2. CONCLUSIONS: The multiple-parameter sensor offers the unique opportunity to study solid as well as hollow organ dysoxia through the simultaneous measurement of interstitial pH, Pco2, and Po2 in a small tissue region. The gradual transition from sufficient oxygen availability to dysoxia as a result of hemorrhage was better described by an exponential equation. The length of time that pH was below or Pco2 was above the critical value determined from the exponential model was predictive of a negative outcome.

Animals↗
PubMed2001

Simultaneous measurement of hepatic tissue pH, venous oxygen saturation and hemoglobin by near infrared spectroscopy.

The purpose of this study was to investigate the feasibility of using near infrared (NIR) spectroscopy of the liver to simultaneously assess oxygen content in combination with tissue pH, an indicator of anaerobic metabolism. Six anesthetized swine were subjected to 45 min of hemorrhagic shock followed by resuscitation with blood and crystalloid. Calibration models between NIR spectra and reference measurements of tissue pH, hepatic venous oxygen saturation (S(V)O2), and blood hemoglobin concentration (Hb) were developed using partial least-squares regression. Model accuracy was assessed using cross validation. The average correlation (R2) between NIR and reference measurements was 0.87, 0.68, and 0.93, respectively for pH, Hb, and S(V)O2. Estimated accuracy, the root mean squared deviation between spectral, and reference measurements was 0.03 pH units, 0.3 g/dL, and 6%. NIR determination of hepatic oxygen content and tissue pH during shock and resuscitation demonstrated that there can be a variance between hepatic venous oxygenation and regional tissue acidosis. NIR spectroscopy provides a technique to explore the implications of post-shock depression of tissue pH and evaluate new methods of resuscitation.

Animals↗
PubMed2001

Core rewarming via warm lavage liquid ventilation in a swine model of hypothermia-associated ventricular fibrillation.

OBJECTIVES: To determine whether warm lavage liquid ventilation (LV) would provide rapid cardiopulmonary rewarming in swine with severe hypothermia and ventricular fibrillation. METHODS: Intubated common swine (n = 3; mean +/- SEM weight 26+/-1.2 kg) were cooled to a mean aortic temperature of 26.4+/-0.9 degrees C. Ventricular fibrillation was induced by transthoracic electrical shock. Rewarming was initiated by continuous endotracheal instillation of warm (44 degrees C) pre-oxygenated, perfluorocarbon liquid at 5 mL/kg/min. Endotracheal instillation of perfluorocarbon occurred while standard gas ventilation continued. Manual chest compressions were performed throughout the 30-minute rewarming process. Outcome measures were the absolute and relative rates of change of all temperatures. RESULTS: After 30 minutes of warm lavage LV, the mean aortic and pulmonary artery temperatures increased by 6.6+/-0.6 degrees C, respectively. Esophageal, nasal, and rectal temperatures did not change significantly. In one animal, normal sinus rhythm spontaneously returned after 16 minutes of rewarming. CONCLUSIONS: During cardiac arrest, warm lavage liquid ventilation may produce rapid cardiopulmonary rewarming.

Analysis of Variance↗
PubMed2001

Catheter-related infection: diagnosis, prevention and treatment.

INTRODUCTION: Catheter infection continues to be a serious problem in critically ill patients. This review will examine the incidence, epidemiology, microbiology, diagnosis, risk factors for and treatment of catheter-related bloodstream infections. METHODS: Relevant articles were culled from a Medline search and other review articles on catheter-related infection. Important abstracts presented within the past year were included in the review if the data had not been published in a peer-reviewed journal. RESULTS: Catheter-related bloodstream infections (CRBSI) increase morbidity and the cost of care of patients. The predominant organisms associated with CRBSI are coagulase negative staphylococci, enterococci and Staphylococcus aureus. Diagnosis usually requires catheter removal and culture but newer techniques such as "differential time to positivity" may permit diagnosis of CRBSI in situ. Reducing risk factors for infection are important: education of house staff, use of the subclavian insertion site, skin preparation with chlorhexidine solutions, use of maximum barrier precautions during catheter insertion and catheter maintenance with chlorhexidine sponges. If infection rates are still high after institution of these measures, use of antiseptic or antibiotic-impregnated catheters should be considered. Treatment of CRBSI in critically ill patients mandates catheter removal and treatment with systemic antibiotics. CONCLUSIONS: The best treatment for CRBSI is prevention. Ongoing studies are evaluating the effectiveness of newer antiseptic catheters, the risk of developing antibiotic resistance when using antibiotic-impregnated catheters and the contribution of multiple interventions on the development of CRBSI.

Algorithms↗
PubMed2000

Outpatient tympanomastoidectomy: factors affecting hospital admission.

BACKGROUND: Outpatient tympanomastoidectomy is common in many medical centers. However, failure of same-day discharge is often the result of postoperative nausea and vomiting (PONV). Many times this leads to hospital admission after tympanomastoidectomy, and it is often difficult to predict before surgery whether PONV will be an issue that impedes same-day discharge. OBJECTIVE: To determine the clinical factors correlated with the incidence of PONV requiring hospital admission after chronic ear surgery by hypothesizing that the complexity of a particular case, as measured using a 10-point scale, is predictive of surgical time or failure of same-day hospital discharge. STUDY DESIGN: Retrospective medical chart review of 103 patients having mastoidectomy with tympanoplasty for chronic otitis media over a 2-year period. METHODS: We recorded patient age, clinical data, surgical times, types of agents used for induction and maintenance of anesthesia, use of prophylactic antiemetic drugs, types and doses of analgesic agents, and PONV. Univariate and multivariate logistic regression analyses were performed to determine which variables were associated with PONV that required hospital admission. RESULTS: One third of patients studied were safely discharged from the hospital the day of surgery, and 92% were discharged within 23 hours. The most common cause for observation admission to the hospital was PONV. The only variable in multivariate analysis that significantly correlated with PONV mandating hospital admission after tympanomastoid surgery was a history of motion sickness or PONV (odds ratio, 5.21; P =.02). Although severity of disease did not correlate with length of hospital stay, it directly correlated with length of surgery. CONCLUSIONS: A history of PONV or motion sickness is predictive of PONV and length of hospital stay. Routine planning for a 23-hour overnight observation stay seems warranted for all patients undergoing tympanomastoidectomy, despite severity of disease.

Adolescent↗
PubMed2000

An evaluation of a new continuous blood pressure monitoring system in critically ill patients.

STUDY OBJECTIVE: To determine if the DxTek monitor, which is a device that measures blood pressure (BP) noninvasively and continuously by means of pulse velocity and wave shapes derived from the pulse oximeter optical plethysmograph and electrocardiogram is as accurate as an oscillometric cuff device when compared with intraarterial BP measurement. DESIGN: Prospective, comparative study. SETTING: University Medical Center. PATIENTS: 28 intensive care unit patients. INTERVENTIONS: Blood pressures were reported every minute by intraarterial catheters and DxTek and every 10 minutes by an oscillometric monitor for 2 to 5 hours. DxTek calibration was performed initially and when specified patient manipulations by caretakers were performed (on average, every 100 minutes). Comparisons with intraarterial pressure included: 1) DxTek calibrated with arterial catheter pressure, 2) DxTek calibrated with oscillometric pressure, and 3) oscillometric pressure. MEASUREMENTS AND MAIN RESULTS: When comparing oscillometric pressure to intraarterial pressure, the averages of the mean differences (bias) were -4.0 mmHg for systolic (SBP) and < 1.5 mmHg for diastolic (DBP) and mean (MAP) pressures. The averages of the standard deviation of the differences (precisions) were 9.6, 6.4, and 6.3 mmHg, respectively. With the DxTek device calibrated to intraarterial pressure, comparison of the DxTek pressure to intraarterial pressure resulted in a bias < OR = 0.5 mmHg for all three pressures and an average precision of 10.1 mmHg for SBP, 6.0 mmHg for DBP, and 6.7 mmHg for MAP. With the DxTek device calibrated to the oscillometric pressure, the DxTek pressure compared to the intraarterial pressure resulted in average biases of -5.1, -0.8, and -2.2 mmHg and average precisions of 11.1, 7.7, and 8.1 mmHg for SBP, DBP, and MAP, respectively. CONCLUSIONS: The DxTek monitor provides continuous, noninvasive BP measurements with an accuracy comparable to oscillometric devices.

Blood Pressure Determination↗
PubMed2000

Acceptance of an ABO-incompatible mismatched (AB(+) to O(+)) liver allograft with the use of daclizumab and mycophenolate mofetil.

Liver allograft survival rates of 50% to 60% are reported in blood group A, group B, group O (ABO)-incompatible mismatched grafts even when aggressive immunosuppressive protocols, including plasmapheresis, OKT(3), cyclophosphamide, cyclosporine, prostaglandin E(1), and steroids, are used. A 59-year-old woman, blood type O(+), required emergency retransplantation posttransplantation day 2 because of primary nonfunction of the liver allograft. A blood type AB(+) allograft was used. Induction immunosuppressive therapy included tacrolimus, mycophenolate mofetil, OKT(3) (muromonab-CD(3)), steroids, and prostaglandin E(1). In addition, plasmapheresis was performed daily for 9 days. OKT(3) and prostaglandin E(1) were also discontinued postoperative day 9. Biopsy-proven acute cellular rejection was diagnosed postoperative day 12 and was treated with double-dose OKT(3) (10 mg) for another 6 days. On the day OKT(3) was discontinued, daclizumab, 60 mg, was administered intravenously. This dose was repeated every 2 weeks for a total of 5 doses. At 1-year follow-up, the patient is doing very well with normal liver function. We are unaware of previous reports of the use of daclizumab and mycophenolate mofetil as part of an immunosuppressive protocol aimed to induce acceptance of ABO-incompatible mismatched liver allografts. Based on our experience with this case, it seems that mycophenolate mofetil is an adequate replacement for cyclophosphamide. We also believe daclizumab provided adequate protection at a critical time. Further experience with both these drugs is required to establish their role in ABO-incompatible mismatched liver allografts.

Antibodies, Monoclonal↗
PubMed2000

Directly measured tissue pH is an earlier indicator of splanchnic acidosis than tonometric parameters during hemorrhagic shock in swine.

OBJECTIVE: To compare tissue pH in the stomach, bowel, and abdominal wall muscle during hemorrhagic shock and recovery using tissue electrodes; also, to compare tissue electrode pH measurements to gastric intramucosal pH (pHi), gastric luminal PCO2, and PCO2 gap (gastric luminal CO2--arterial CO2) measured with an air-equilibrated tonometer. DESIGN: Prospective animal study. SETTING: University animal research laboratory. SUBJECTS: Eight anesthetized, mechanically ventilated Yorkshire swine. INTERVENTIONS: Hemorrhagic shock was initiated by withdrawing blood over a 15-min period to lower systolic blood pressure to 45 mm Hg. Shock was maintained for 45 mins and was followed by a 5-min resuscitation to normal blood pressure with a blood/lactated Ringer's (1:2) mixture. Recovery was monitored for 60 mins. MEASUREMENTS AND MAIN RESULTS: pH was measured with electrodes in the submucosa of the stomach, the submucosa of the small bowel, and the abdominal wall muscle. Gastric luminal PCO2 was measured with an air-equilibrated tonometer and pHi and PCO2 gap were calculated. Each organ showed a different sensitivity to shock and resuscitation. The bowel pH responded most rapidly to the onset of hemorrhagic shock and had the largest change in tissue pH. The bowel also showed the most rapid recovery during resuscitation. The submucosal pH of the stomach responded more slowly than the bowel, but faster than the abdominal wall muscle pH, gastric PCO2 gap, or pHi. The smallest changes in organ pH as a result of hemorrhagic shock were seen in the abdominal wall muscle and the stomach as assessed by gastric tonometry. CONCLUSIONS: Direct measurement of tissue pH indicates that intra-abdominal organ pH varies during hemorrhagic shock. The small bowel pH changes the most in magnitude and rapidity compared with stomach pH or abdominal wall muscle pH. Tonometrically derived parameters were not as sensitive in the detection of tissue acidosis during shock and resuscitation as pH measured directly in the submucosa of the stomach or small bowel.

Acidosis↗
PubMed2000

Management of the septic patient in the operating room.

Sepsis, severe sepsis, and septic shock represent the spectrum of physiological response to a variety of infecting pathogens. Multiple-organ dysfunction may result from widespread activation of inflammatory and antiinflammatory mechanisms. Intensive multiorgan support, effective antibiotic therapy, and eradication of the inciting source remain the cornerstones in the care of septic patients. Perioperative planning and management need to ensure the continuation of such care in addition to providing for the requirements of the given surgical procedure.

Disseminated Intravascular Coagulation↗
PubMed2000

"Preconditioning at a distance" in the isolated rabbit heart.

OBJECTIVE: Brief myocardial ischemia evokes a cardioprotective response, referred to as "ischemic preconditioning" (IP), that limits injury caused by a subsequent prolonged ischemic insult. The myocardial IP effect can be induced by ischemia of "distant" cardiac and noncardiac tissue, implicating the involvement of an as-yet-unidentified humoral trigger. If a preconditioning hormone exists, the authors hypothesize that the IP effect should be transferable, via administration of coronary effluent, from a preconditioned donor heart to a virgin non-preconditioned acceptor heart. METHODS: Isolated buffer-perfused rabbit hearts were assigned to one of four treatment groups in a donor/acceptor sequence. Donor hearts underwent either three IP cycles or a matched period of uninterrupted perfusion (control donors). Coronary perfusate collected from IP and control donor hearts was reoxygenated and transfused to virgin acceptor hearts. All hearts then underwent 30 minutes of global ischemia followed by 30 minutes of reperfusion. Left ventricular developed pressure (LVDP) (the authors' index of cardioprotection) was monitored throughout the protocol by a left ventricular (LV) balloon. RESULTS: In donor controls, LVDP assessed at 30 minutes post-reflow was restored to only 49 +/- 5% of baseline values. Recovery of LV function was significantly enhanced in both IP donor hearts (69 +/- 4%*) and IP acceptor hearts (70 +/- 6%*) vs donor controls (*p < 0.05), while, in acceptor controls, intermediate values of LVDP (62 +/- 7%) were obtained. CONCLUSION: The IP effect can be transferred between rabbit hearts, suggesting the presence of a humoral trigger signal for distant preconditioning. Isolating this hormone may have therapeutic and diagnostic implications in the management of acute myocardial ischemia.

Animals↗
PubMed1999

A comparison of two antimicrobial-impregnated central venous catheters. Catheter Study Group.

BACKGROUND: The use of central venous catheters impregnated with either minocycline and rifampin or chlorhexidine and silver sulfadiazine reduces the rates of catheter colonization and catheter-related bloodstream infection as compared with the use of unimpregnated catheters. We compared the rates of catheter colonization and catheter-related bloodstream infection associated with these two kinds of antiinfective catheters. METHODS: We conducted a prospective, randomized clinical trial in 12 university-affiliated hospitals. High-risk adult patients in whom central venous catheters were expected to remain in place for three or more days were randomly assigned to undergo insertion of polyurethane, triple-lumen catheters impregnated with either minocycline and rifampin (on both the luminal and external surfaces) or chlorhexidine and silver sulfadiazine (on only the external surface). After their removal, the tips and subcutaneous segments of the catheters were cultured by both the roll-plate and the sonication methods. Peripheral-blood cultures were obtained if clinically indicated. RESULTS: Of 865 catheters inserted, 738 (85 percent) produced culture results that could be evaluated. The clinical characteristics of the patients and the risk factors for infection were similar in the two groups. Catheters impregnated with minocycline and rifampin were 1/3 as likely to be colonized as catheters impregnated with chlorhexidine and silver sulfadiazine (28 of 356 catheters [7.9 percent] vs. 87 of 382 [22.8 percent], P<0.001), and catheter-related bloodstream infection was 1/12 as likely in catheters impregnated with minocycline and rifampin (1 of 356 [0.3 percent], vs. 13 of 382 [3.4 percent] for those impregnated with chlorhexidine and silver sulfadiazine; P<0.002). CONCLUSIONS: The use of central venous catheters impregnated with minocycline and rifampin is associated with a lower rate of infection than the use of catheters impregnated with chlorhexidine and silver sulfadiazine.

Analysis of Variance↗
PubMed1999

Ischemic preconditioning may be transferable via whole blood transfusion: preliminary evidence.

This research was designed to test the hypothesis that ischemic preconditioning can be transferred between animals via whole blood transfusion. Preconditioning at a distance refers to the reduction in myocardial infarct size seen when coronary artery occlusion is preceded by brief ischemic episodes of noncardiac tissue. Isolation of the trigger signal responsible for this effect may be useful in the diagnosis and treatment of acute coronary occlusive syndromes. Rabbits were paired by crossmatching blood samples prior to experimentation. Crossmatched pairs were placed into either preconditioned (P) or control sets. Rabbits in the preconditioned sets were further divided into donor (PD) and acceptor (PA) animals. PD animals underwent five episodes of circumflex and renal artery occlusion followed by reperfusion. Before and after each preconditioning episode, a whole blood exchange was performed between PD and PA animals. Alternatively, control rabbits underwent the same surgical procedures and time-sequenced transfusion without preconditioning. All animals then underwent prolonged circumflex occlusion (60 minutes) followed by reperfusion (30 minutes). The area of myocardium at risk (R) was determined by isotope-labeled microsphere injection. Infarct size (I) was determined by NBT staining. The percent infarct within the risk area (I/R) was then compared. The I/R was significantly lower in the PA (14.0% +/- 12.2) and PD (14.3% +/- 11.2) groups as compared with controls (61% +/- 20. 6). There was no significant difference between the tPA and TPD groups. In conclusion, the ischemic preconditioning effect can be transferred to nonpreconditioned animals via whole blood transfusion, suggesting a humoral mechanism for preconditioning at a distance.

Animals↗
PubMed1999

The influence of liposome-encapsulated prostaglandin E1 on hydrogen peroxide concentrations in the exhaled breath of patients with the acute respiratory distress syndrome.

UNLABELLED: Hydrogen peroxide (H2O2) levels are increased in the exhaled breath of patients with the acute respiratory distress syndrome (ARDS). Because liposome-encapsulated prostaglandin E1 (PGE1) downregulates the CD11/CD18 receptor of the neutrophil, thereby limiting endothelial adhesion, the use of this drug should decrease the excretion of H2O2 in the expiratory condensate of patients with ARDS. Patients > 11 yr of age with ARDS (diffuse, patchy infiltrates by chest radiograph; Pao2/fraction of inspired oxygen [P/F] ratio < or = 200 mm Hg; pulmonary capillary wedge pressure < or = 18 mm Hg; and the requirement for mechanical ventilation) were randomized to receive placebo (n = 14) or escalating doses (0.15-3.6 micrograms/kg) of liposomal PGE1 (n = 14) every 6 h for up to 7 days. Condensate was collected every morning from the expiratory tubing that was submerged in an ice saltwater bath (-5 degrees C). H2O2 levels were measured by using a horseradish peroxidase assay. Other data collected included white blood cell count and P/F ratios. There was no significant difference in the concentration of H2O2 in the expiratory condensate between the liposomal PGE1 group and the control group either before (0.99 +/- 0.52 vs 0.93 +/- 0.48 mumol/L) or during treatment (1.04 +/- 0.45 vs 0.76 +/- 0.25 mumol/L). Liposomal PGE1 treatment improved the P/F ratio and decreased the white blood cell count over time. Despite its ability to downregulate the CD11/CD18 neutrophil receptor, liposomal PGE1 did not reduce exhaled H2O2 excretion. IMPLICATIONS: White blood cells (WBC) are thought to be part of the cause of the acute respiratory distress syndrome, a lung disease. WBC in the lung produce hydrogen peroxide, which is exhaled. Liposomal PGE1 inhibits WBC function but was found to have no effect in decreasing exhaled hydrogen peroxide in patients with the acute respiratory distress syndrome.

Adult↗