Biomedical subjects

N Polissar

Publications and source records attributed to N Polissar.

10 recordsLinked to original sources

PubMed2005

Regional hypoxic pulmonary vasoconstriction in prone pigs.

Hypoxic pulmonary vasoconstriction (HPV) is known to affect regional pulmonary blood flow distribution. It is unknown whether lungs with well-matched ventilation (V)/perfusion (Q) have regional differences in the HPV response. Five prone pigs were anesthetized and mechanically ventilated (positive end-expiratory pressure = 2 cmH2O). Two hypoxic preconditions [inspired oxygen fraction (FI(O2)) = 0.13] were completed to stabilize the animal's hypoxic response. Regional pulmonary blood Q and V distribution was determined at various FI(O2) (0.21, 0.15, 0.13, 0.11, 0.09) using the fluorescent microsphere technique. Q and V in the lungs were quantified within 2-cm3 lung pieces. Pieces were grouped, or clustered, based on the changes in blood flow when subjected to increasing hypoxia. Unique patterns of Q response to hypoxia were seen within and across animals. The three main patterns (clusters) showed little initial difference in V/Q matching at room air where the mean V/Q range was 0.92-1.06. The clusters were spatially located in cranial, central, and caudal portions of the lung. With decreasing FI(O2), blood flow shifted from the cranial to caudal regions. We determined that pulmonary blood flow changes, caused by HPV, produced distinct response patterns that were seen in similar regions across our prone porcine model.

Animals↗

PubMed2005

Livers transplanted from donors after cardiac death occurring in the ICU or the operating room have excellent outcomes.

BACKGROUND: Increasing donor hospital cooperation with donation after cardiac death (DCD) requires the organ procurement organization (OPO) to use current withdrawal of life support (WLS) protocols. Hospital ICU nurses/physicians are comfortable performing the emotionally draining procedure of WLS in the ICU while OPOs are reluctant to accept these donors due to increased warm ischemia (WI). In our area, several hospitals will only allow WLS to occur in the ICU. This study compares liver outcomes from DCD donors where death occurred in the ICU (DCDICU) vs the OR (DCDOR). METHODS: From March 2003 to June 2004, 34 DCD donors were recovered by our OPO. WLS occurred in the ICU for 26 donors (76%) and in the OR for 8 donors (24%). Thirteen of 26 DCDICU and 5 of 8 DCDOR livers were transplanted. Donor demographics, warm ischemic time, cold ischemic time, distance shipped, and recipient functions were analyzed. RESULTS: Eighteen livers were transplanted both locally and at distant transplant centers. Results are outlined in the . CONCLUSIONS: Although DCDICU donors averaged approximately 4 minutes longer WI than DCDOR donors, short-term results for both groups were equivalent. These findings support using DCDICU livers. DCDICU donors have the potential to significantly improve donor hospital cooperation.

Adult↗

PubMed2000

Sedation during spinal anesthesia.

BACKGROUND: Central neuraxial anesthesia has been reported to decrease the dose of both intravenous and inhalational anesthetics needed to reach a defined level of sedation. The mechanism behind this phenomenon is speculated to be decreased afferent stimulation of the reticular activating system. The authors performed a two-part study (nonrandomized pilot study and a subsequent randomized, double-blind, placebo-controlled study) using the Bispectral Index (BIS) monitor to quantify the degree of sedation in unmedicated volunteers undergoing spinal anesthesia. METHODS: Twelve volunteers underwent BIS monitoring and observer sedation scoring (Observer's Assessment of Alertness/Sedation Scale [OAA/S]) before and after spinal anesthesia with 50 mg hyperbaric lidocaine, 5%. Subsequently, 16 volunteers blinded to the study were randomized to receive spinal anesthesia with 50 mg hyperbaric lidocaine, 5% (n = 10) or placebo (n = 6) and underwent BIS and OAA/S monitoring. RESULTS: In part I, significant changes in BIS scores of the volunteers occurred progressively (P = 0.003). The greatest variations from baseline BIS measurement occurred at 30 and 70 min. In part II, there were significant decreases in OAA/S and self-sedation scores for patients receiving spinal anesthesia versuscontrol patients (P = 0.04 and 0. 01, respectively). The greatest decrease in OAA/S scores occurred at 60 min. BIS scores were similar between groups (P = 0.4). CONCLUSIONS: Spinal anesthesia is accompanied by significant sedation progressively when compared with controls as measured by OAA/S and self-sedation scores. This effect was not related to block height. The late sedation observed by OAA/S at 60 min may indicate a second mechanism of sedation, such as delayed rostral spread of local anesthetics. BIS was not a sensitive measure of the sedation associated with spinal anesthesia in the randomized, blinded portion of this study.

Adult↗

PubMed1999

Blood pressure, antihypertensive medication, and atherosclerotic renal artery stenosis.

The relationship between atherosclerotic renal artery stenosis (ARAS) and blood pressure control remains poorly understood. Duplex ultrasonography is a noninvasive method for detecting and grading ARAS. The purpose of this study was to characterize the relationship between the degree of ARAS, levels of blood pressure, and control of blood pressure with antihypertensive medication. A cross-sectional analysis was performed on 139 patients with ARAS. All patients had at least one diseased renal artery by duplex ultrasound. Renal arteries were classified as normal, less than 60% stenosis, or 60% or greater (high-grade) stenosis. Data regarding blood pressure, coexisting risk factors, and medications were collected. The extent of ARAS was significantly associated with progressive elevation of the systolic blood pressure, whereas the diastolic component was elevated in the case of unilateral high-grade stenosis: no high-grade stenoses, 153 +/- 22/81 +/- 10 mm Hg; unilateral high-grade stenosis, 162 +/- 22/86 +/- 9 mm Hg; and bilateral high-grade stenoses, 174 +/- 27/82 +/- 9 mm Hg (P = 0.002 systolic; P = 0.02 diastolic). Eighty-two percent of the patients were taking known antihypertensive medications. Angiotensin-converting enzyme inhibitor (ACEI) usage versus nonusage was associated with a significantly lower systolic (157 +/- 27 v 169 +/- 22 mm Hg; P = 0.03) and diastolic (79 +/- 9 v 85 +/- 9 mm Hg; P = 0.001) blood pressure. The effect of ACEI usage was observed in patients with high-grade ARAS. None of the other classes of antihypertensive medications were associated with significantly lower blood pressure. In patients with ARAS, blood pressure levels were correlated with the severity of renal artery disease. Patients taking ACEIs had significantly lower blood pressures, and the effect of ACEI usage was strongest among patients with unilateral ARAS.

Aged↗

PubMed1999

Implementing guidelines for cancer pain management: results of a randomized controlled clinical trial.

PURPOSE: Pain and symptom management is an integral part of the clinical practice of oncology. A number of guidelines have been developed to assist the clinician in optimizing comfort care. We implemented clinical guidelines for cancer pain management in the community setting and evaluated whether these guidelines improved care. PATIENTS AND METHODS: Eighty-one cancer patients, aged 37 to 76 years, were enrolled onto a prospective, longitudinal, randomized controlled study from the outpatient clinic settings of 26 western Washington-area medical oncologists. A multilevel treatment algorithm based on the Agency for Health Care Policy and Research Guidelines for Cancer Pain Management was compared with standard-practice (control) pain and symptom management therapies used by community oncologists. The primary outcome of interest was pain (Brief Pain Inventory); secondary outcomes of interest were all other symptoms (Memorial Symptom Assessment Scale) and quality of life (Functional Assessment of Cancer Therapy Scale). RESULTS: Patients randomized to the pain algorithm group achieved a statistically significant reduction in usual pain intensity, measured as slope scores, when compared with standard community practice (P < .02). Concurrent chemotherapy and patient adherence to treatment were significant mediators of worst pain. There were no significant differences in other symptoms or quality of life between the two treatment groups. CONCLUSION: This guideline implementation study supports the use of algorithmic decision making in the management of cancer pain. These findings suggest that comprehensive pain assessment and evidence-based analgesic decision-making processes do enhance usual pain outcomes.

Adult↗

PubMed1998

Determinants of chronic venous disease after acute deep venous thrombosis.

PURPOSE: The purpose of this investigation was to evaluate the relationship between the presenting features of an acute deep venous thrombosis (DVT), the subsequent natural history of the thrombus, and the ultimate outcome as defined according to the Society for Vascular Surgery and the North American Chapter of the International Society for Cardiovascular Surgery reporting standards in venous disease. METHODS: Patients with an acute DVT were followed with serial clinical and ultrasound examinations. Thrombus extent within 7 venous segments was scored retrospectively according to the reporting standards (scores ranged from 0 to 3), and segmental reflux was scored as present (1) or not present (0). The initial and final thrombus scores, the rates of recanalization and rethrombosis, and the total reflux scores were then calculated from these grading scales and related to ultimate chronic venous disease (CVD) classification. RESULTS: Sixty-eight patients with an acute DVT in 73 limbs were followed for 18 to 110 months (mean, 55 +/- 26 months). At the completion of the follow-up period, 20 extremities (27%) were asymptomatic (class 0), 13 (18%) had pain or prominent superficial veins (class 1), 25 (34%) had manifested edema (class 3), 13 (18%) had developed hyperpigmentation (class 4), and 2 (3%) had developed ulceration (class 5). In a univariate analysis, CVD classification was correlated with the reflux score (P =.003) but not with the initial or final thrombus score or with the rate of recanalization or rethrombosis. In a multivariate model of features documented at presentation, only the tibial thrombosis score was a significant predictor of CVD classification (R2 =.06). Outcome was better predicted (R2 =.29) with a model that included variables defined during follow-up the final reflux score, the final popliteal score, and the rate of recanalization. CONCLUSION: The ability to predict the severity of CVD after an acute DVT is currently limited, although the natural history appears more important than the presenting features of the event. The extent of reflux, the presence of persistent popliteal obstruction, and the rate of recanalization are related to ultimate CVD classification, but other determinants remain to be identified.

Acute Disease↗

PubMed1997

A scientific plan for the evaluation of alternative medicine in the treatment of HIV/AIDS.

The Bastyr University AIDS Research Center was established in October 1994 through a 3-year cooperative grant with the Office of Alternative Medicine, National Institutes of Health. The mission of the Center is to (1) describe forms and patterns of use of alternative medical therapies for HIV infection and AIDS prescribed by practitioners and self-administered by HIV-positive patients in the United States, (2) screen and evaluate therapies for HIV/AIDS from five program areas of alternative medicine, and (3) provide consultation and support in the scientific evaluation of alternative therapies. To meet these goals, the Center has established a network of cooperating alternative medicine clinics and is recruiting HIV-positive men and women who are using alternative medicine to participate in the study. It is collecting data every 6 months from 1500 HIV-positive patients throughout the United States and has created a centralized database to compare outcomes (CD4+ lymphocytes, HIV RNA, CDC class progression, weight, quality of life, and survival) for a variety of alternative therapies. The Center will determine whether patients who use both conventional medicine and alternative medicine have different outcomes from patients who use only conventional medicine. The occurrence of AIDS-related opportunistic infections and neoplasms in HIV-positive patients who are using specific alternative therapies will be compared with the incidence in those who use other medical treatment. This article describes the scientific plan for the study.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Pulmonary blood flow distribution in standing horses is not dominated by gravity.

Recent studies using microspheres in dogs, pigs and goats have demonstrated considerable heterogeneity of pulmonary perfusion within isogravitational planes. These studies demonstrate a minimal role of gravity in determining pulmonary blood flow distribution. To test whether a gravitational gradient would be more apparent in an animal with large vertical lung height, we measured perfusion heterogeneity in horses (vertical lung height = approximately 55 cm). Four unanesthetized Thoroughbred geldings (422-500 kg) were studied awake in the standing position with fluorescent microspheres injected into a central vein. Between 1,621 and 2,503 pieces (1.3 cm3 in volume) were obtained from the lungs of each horse with spatial coordinates, and blood flow was determined for each piece. The coefficient of variation of blood flow throughout the lungs ranged between 22 and 57% among the horses. Considerable heterogeneity was seen in each isogravitational plane. The relationship between blood flow and vertical height up the lung was characterized by the slope and correlation coefficient of a least squares regression analysis. The slopes within each horse ranged from -0.052 to +0.021 relative flow units/cm height up the lung, and the correlation coefficients varied from 0.12 to 0.75. A positive slope, indicating that flow increased with vertical distance up the lung (opposite to gravity), was observed in three of the four horses. In addition, blood flow was uniformly low in three of the four horses in the most cranial portions of the lungs. We conclude that in lungs of resting unanesthetized horses, animals with a large lung height, there is no consistent vertical gradient to pulmonary blood flow and there is a considerable degree of perfusion heterogeneity, indicating that gravity alone does not play the major role in determining blood flow distribution.

Animals↗

PubMed1996

Minimal redistribution of pulmonary blood flow with exercise in racehorses.

We determined the spatial distribution of pulmonary blood flow at rest and during increasing levels of exercise (34, 59, and 90% of maximal oxygen consumption) in Thoroughbred racehorses (n = 4) using 15-microns fluorescent microspheres. After the horses were killed, the lungs were flushed free of blood, removed, air-dried at total lung capacity, and sliced into isogravitational planes, which were sampled in a systematic fashion for three-dimensional reconstruction. The fluorescence was measured for quantification of blood flow. Mean pulmonary blood flow heterogeneity (expressed as a coefficient of variation) did not change with increasing exercise levels [36.2 +/- 16.4 (rest) to 26.9 +/- 6.8% (gallop); P = not significant]. Greater than 70% of pulmonary blood flow variation across rest to high-exercise states is determined by a fixed spatial pattern. Thirty percent of the variation in pulmonary blood flow seen in horses over rest and exercising states is due to redistribution. The majority of flow redistribution was due to flow increasing to the dorsal region of the lung during exercise at 90% of maximal oxygen consumption (a flow gradient of 0.20 ml. min-1.cm-1 up the lung; P = 0.04).

Animals↗

PubMed1996

Explaining reduced cancer survival among the disadvantaged.

The fact that socially disadvantaged cancer patients face a greater risk of mortality than the advantaged is well recognized but poorly understood. Existing research and a newly completed 10-year survival study suggest that complex interrelations among biological factors, medical interventions, and specific dimensions of social differentiation determine survival differences. Patterns of interrelations among determinants of survival appear compatible with an "economic" model in some forms of cancer and a "cognitive-behavioral" model in others. Findings presented here suggest that improved access to health care will reduce mortality risk among the disadvantaged in at least some malignancies, but will not alone make their survival chances equal to those of the advantaged.

Adult↗