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Biomedical subjects

L R Smith

Publications and source records attributed to L R Smith.

At least 37 records · Page 2Linked to original sources
PubMed1995

In-hospital and long-term outcome after porcine tricuspid valve replacement.

Porcine bioprostheses are often used for tricuspid valve replacement, yet the long-term outcome after this procedure is not well documented. Therefore, the records of 129 patients undergoing tricuspid valve replacement with Carpentier-Edwards (n = 88) or Hancock (n = 41) prostheses between 1975 and 1993 were reviewed. The operation required a repeat median sternotomy in 66 of 129 (51%) patients, whereas 67 of 129 (52%) underwent double or triple valve replacement. Operative mortality was 14% (2/14) in patients undergoing first-time isolated tricuspid valve replacement and 27% (35/129) overall. Survival at 5, 10, and 14 years was 56% +/- 5%, 48% +/- 5%, and 31% +/- 9%, and freedom from tricuspid reoperation at 5, 10, and 14 years was 96% +/- 3%, 93% +/- 4%, and 49% +/- 17%. No valve thrombosis was observed. In this largest reported series of porcine bioprostheses in the tricuspid position, long-term freedom from valve-related events was excellent because of a low incidence of valve thrombosis and a valve durability of 13 to 15 years in a population with limited life expectancy.

Bioprosthesis↗
PubMed1995

A comparison of amrinone with sodium nitroprusside for control of hemodynamics during infrarenal abdominal aortic surgery.

OBJECTIVES: The control of hemodynamic changes during surgical resection of abdominal aortic aneurysms (AAA) remains a challenge to anesthesiologists. In the past, hypertensive episodes have been treated with sodium nitroprusside (SNP). However, amrinone may provide some benefits when compared with SNP because of its positive inotropic and vasodilatory properties. Therefore, the purpose of this study was to compare amrinone with SNP for hemodynamic control during AAA surgery. DESIGN: This study was a prospective, randomized investigation. SETTING: This study was performed at a single university hospital. PARTICIPANTS: This study included 20 patients undergoing AAA resection. INTERVENTIONS: After institutional review board approval, participants were randomized to receive either SNP (group N = 10) or amrinone (group A = 10). Both agents were started 10 minutes before aortic cross-clamping and discontinued 10 minutes before unclamping. Anesthesia was induced with thiopental or etomidate and maintained with oxygen, nitrous oxide, isoflurane, fentanyl, and vecuronium. Hemodynamic measurements included heart rate, systolic and diastolic blood pressure, cardiac output, systolic and diastolic pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure, mixed venous oxygen saturation, electrocardiogram, and ST-T wave trend analysis. MEASUREMENTS AND MAIN RESULTS: Demographic and clinical characteristics for the two groups were similar. Mixed venous oxygen saturation was significantly lower (p < 0.05) in group N immediately after unclamping. There were no differences between groups for the other measurements studied. There were no episodes of myocardial ischemia in either group. CONCLUSIONS: This study demonstrates that amrinone provides equivalent hemodynamic control to SNP during abdominal aortic aneurysm surgery because it allows moderate reductions in blood pressure without affecting other hemodynamic measurements. Further studies are needed to assess whether patients with poor preoperative left ventricular function would benefit from amrinone management during AAA resection.

Aged↗
PubMed1995

Aging increases pharmacodynamic sensitivity to the hypnotic effects of midazolam.

The effect of aging on the pharmacodynamics of midazolam was investigated in a double-blinded study involving 39 consenting patients ranging in age from 39 to 77 yr. Midazolam was infused intravenously (i.v.) using a pharmacokinetic model-driven drug infusion device to achieve a plasma midazolam concentration that was held constant for the 10-min duration of the study. Blood samples were obtained from the radial artery at 5 and 10 min for subsequent measurement of the plasma midazolam concentrations. With the 10-min sample, the patients were also assessed for the presence or absence of responsiveness to verbal command. To ensure that the pharmacodynamic end-point was assessed under the condition of a relative steady-state effect-site midazolam concentration, only those patients (n = 33) in whom the plasma midazolam concentration at 10 min was within 30% of the measured concentration at 5 min were included in the subsequent data analyses. Logistic regression was used to fit the verbal command response/no response data to a mathematical model that included patient age and the plasma midazolam concentration measured at 10 min. Cp50, the steady-state plasma midazolam concentration at which 50% of patients would be expected not to respond to a specific stimulus (e.g., verbal command), was calculated as a function of age from the parameterized logistic model. The midazolam Cp50 for response to verbal command decreased significantly (P = 0.034) with increasing patient age, demonstrating that aging increases pharmacodynamic sensitivity to the hypnotic effects of midazolam independent of pharmacokinetic factors.

Adult↗
PubMed1995

Differential age effects of mean arterial pressure and rewarming on cognitive dysfunction after cardiac surgery.

Central nervous system dysfunction is a common consequence of otherwise uncomplicated cardiac surgery. Many mechanisms have been postulated for the cognitive dysfunction that is part of these neurologic sequelae. The purpose of our investigation was to evaluate the effects of mean arterial pressure (MAP) during cardiopulmonary bypass (CPB) and the rate of rewarming on cognitive decline after cardiac surgery. Two hundred thirty-seven patients completed preoperative and predischarge neuropsychologic testing. MAP and temperature were recorded at 1-min intervals using an automated anesthesia record keeper. MAP area less than 50 mm Hg (time and degree of hypotension), as well as the maximal rewarming rate, were determined for each patient. Multivariable linear regression revealed that the rate of rewarming and MAP were unrelated to cognitive decline. However, interactions significantly associated with cognitive decline were found between age and MAP area less than 50 mm Hg on one measure, and between age and rewarming rate in another, identifying susceptibility of the elderly to these factors. Although MAP and rewarming were not the primary determinates of cognitive decline in this surgical population, hypotension and rapid rewarming contributed significantly to cognitive dysfunction in the elderly.

Aged↗
PubMed1995

Are modern imaging techniques over diagnosing ureteropelvic junction obstruction?

Since the widespread use of real-time ultrasonography in the early 1980s, ureteropelvic junction obstruction has been diagnosed at earlier ages and prenatally on a presumptive basis. However, substantial controversy exists over the diagnosis and treatment of ureteropelvic junction obstruction. We conducted an epidemiological study to determine if modern imaging techniques are leading to the over diagnosis of ureteropelvic junction obstruction. Records were collected retrospectively from 3 hospitals serving 2 adjacent counties to determine the number of pyeloplasties performed in 1970 to 1992. The 2 university hospitals and 1 large private hospital provide a wide variety of services and choice of urologists, and so it was assumed that most patients requiring pyeloplasty in the area would be captured. Of the 555 pyeloplasties 240 (43%) were performed on children 12 years old or younger. Logistic regression analysis revealed an overall increase of pyeloplasties per year of 56.8% in 23 years, which was not markedly different from the population growth in the area in the same period (49.3%). A statistically significant increase in the number of pyeloplasties performed in the first year of life was noted. This trend appeared to begin in 1981: 8 pyeloplasties were performed in the first year of life between 1970 and 1980 compared to 91 between 1981 and 1992. Pyeloplasties in children 1 to 6 years old increased with time at a much lower rate that was not statistically significant and the number of pyeloplasties decreased in those 7 to 12 years old. Therefore, it appears that modern imaging techniques are not leading to an over diagnosis of ureteropelvic junction obstruction but to detection of the disease at an earlier age.

Adolescent↗
PubMed1995

Jugular bulb saturation and mixed venous saturation during cardiopulmonary bypass.

Systemic venous oxygen saturation is clinically used as an indicator of a satisfactory oxygen supply demand balance on cardiopulmonary bypass (CBP). Cerebral desaturation has been associated with postoperative cognitive dysfunction and has an incidence of 17% to 23% on bypass. We tested the hypothesis that systemic venous saturation did not correlate with jugular bulb venous saturation. Blood was drawn from the radial artery, jugular bulb catheter, and venous return line for determination of pH, oxygen tension and saturation, and carbon dioxide tension at four times during bypass: warm 1 (following initiation of CPB); cold 1 (stable hypothermia); cold 2 (hypothermia prior to rewarm); and warm 2 (nasopharyngeal temperature 36 degrees C to 37 degrees C). Correlations of jugular bulb and systemic venous saturation at cold 1 were r = 0.29, r2 = 0.08, and p = 0.0005, and at warm 2 were r = 0.22, r2 = 0.05, and p = 0.007. We conclude that systemic saturation is a poor indicator of cerebral saturation. The poor association of jugular and systemic pump venous saturations underscores our inability to evaluate adequacy of cerebral perfusion. Jugular saturation is lower than pump venous return blood, especially at times of lower oxygen delivery, thus either continuous invasive or noninvasive evaluation of cerebral oxygenation is required to evaluate the adequacy of cerebral perfusion.

Aged↗
PubMed1995

Depression in male and female patients undergoing cardiac surgery.

The present longitudinal study was designed to determine the prevalence of depression in male and female patients undergoing cardiac surgery, and to examine what factors are associated with depression before and after surgery. One day prior to surgery (T1), and one day prior to discharge from the hospital (T2), 141 patients completed a psychometric test battery including the Center for Epidemiological Studies Depression Scale (CES-D), the State-Trait Anxiety Inventory (STAI), and the Perceived Social Support Scale (PSSS). Data were also collected on 13 physiological measures. Forty-seven per cent of patients were depressed (defined as a score of 16 or above on the CES-D) at T1. Scores on the CES-D significantly increased from T1 (M = 15) to T2 (M = 20), with 61 per cent of patients classified as depressed at T2. Factors associated with depression at T1 were female gender, higher state anxiety, and less social support. Depressed patients at T2 were characterized by higher scores on the STAI at T2 and higher scores on the CES-D at T1. The prevalence of depression in cardiac surgery patients, particularly women, may be underrecognized and warrants increased attention.

Adult↗
PubMed1995

The Mini Mental State Exam as a predictor of neuropsychological functioning after cardiac surgery.

OBJECTIVE: The present longitudinal study was designed to: 1) determine the ability of the Mini Mental State Exam (MMSE) to predict neuropsychologic impairment based on neuropsychologic testing five to seven days and six weeks after cardiac surgery; and 2) to determine whether the traditional or the education-related MMSE norms are more appropriate to use for this purpose. METHOD: The day before surgery (T1), before hospital discharge (T2), and six weeks after surgery (T3), 247 subjects completed a battery of five neuropsychologic tests. Subjects also completed the Center for Epidemiological Studies Depression Scale and the Speilberger State-Trait Anxiety Inventory. Subjects completed the MMSE two to three days after surgery. RESULTS: Stepwise regression analyses revealed that the MMSE significantly predicted only a small portion of the variance in neuropsychologic test performance at T2, and to an even lesser extent at T3, over and above the demographic variables. In assessing the association between an impairment score (derived from the neuropsychologic test battery) and the MMSE, we found that the traditional MMSE cut-off score maximized specificity (number of true negatives) while the education-adjusted MMSE cut-off scores maximized sensitivity (number of true positives). CONCLUSIONS: These results suggest that although the MMSE is widely used to assess cognitive mental status, it may have limited value in identifying patients with cognitive impairment post-cardiac surgery, and special attention must be paid to the cut-off scores used in interpreting the MMSE.

Adult↗
PubMed1995

Clinical use of a frameless stereotactic arm: results of 325 cases.

The viewing wand is a frameless stereotactic arm that can be used in conjunction with computerized tomography (CT) or magnetic resonance (MR) imaging to provide image-based intraoperative navigation. The authors report a series of 325 cases in which the viewing wand was used and evaluated for its utility, ease of integration into the standard surgical setup, reliability, and real-world accuracy. The use of the system was associated with minimal additional effort or time spent in setting up the procedure as long as a trained technician performed the data transfer and reconstruction. The viewing wand was used in 165 cases in conjunction with CT and 145 cases with MR imaging. The system was reliable, achieving a useful registration in 310 of 325 cases (95.4%). Fiducial-based registration was more accurate than an anatomical landmark-surface fit algorithm method of registration (mean 2.8 vs. 5.6 mm error, respectively, for CT; and mean 3.0 vs. 6.2 mm for MR imaging). The actual error of the system in estimating the position of the probe tip just after registration was judged by the operating surgeon to be less than 2 mm in 92% of MR imaging cases and in 82% of CT cases, between 2 and 5 mm in 7% of MR imaging and 17% of CT cases, and greater than 5 mm in less than 1% of MR imaging and 1.2% of CT cases. The accuracy of the system degraded during the operation, so that by the third evaluation the error was estimated to be less than 2 mm in 77% of MR imaging and 62% of CT cases. Overall, the viewing wand was found to be reliable and accurate. This real-world accuracy was sufficient for a broad range of applications including glioma resection, cerebrospinal fluid shunting procedures, resection of small subcortical masses, and temporal lobe resection. The system is a useful navigational aid that allows a direct approach to intracranial pathology without the drawbacks of application and the limitations of a stereotactic frame.

Adolescent↗
PubMed1995

Ascent rate, post-dive exercise, and decompression sickness in the rat.

The effects of ascent rate and post-dive exercise on the incidence of decompression sickness (DCS) were investigated in six groups of 20 rats exposed for 2 h at a pressure equivalent to 240 feet of sea water (fsw; 735 kPa). Ascent rates were 30, 45, and 60 fsw/min (92, 138, 184 kPa/min), and the rats either rested after the exposure or exercised by walking for 30 min on a treadmill at 1.6 m/min. Post-dive signs included respiratory distress, difficulty walking, paralysis, and death. DCS was scored as non-fatal at 30-min post-dive or fatal at any time. Analysis by ordinal logistic regression indicated more DCS with post-dive exercise (P = 0.0112) and at 45 (P = 0.0011) and 60 fsw/min (P = 0.0001) compared to 30 fsw/min. Survival analysis suggested earlier death at 60 fsw/min compared to 30 fsw/min (P = 0.0006). Similar effects have been reported for the less severe DCS that occurs in humans.

Animals↗
PubMed1994

CD8+ T cells in psoriatic lesions preferentially use T-cell receptor V beta 3 and/or V beta 13.1 genes.

Psoriasis is an inflammatory skin disorder characterized by epidermal keratinocyte hyperproliferation in association with a cellular infiltrate. There is evidence that activated T cells play a role in psoriatic plaque formation. We examined the T-cell receptor beta-chain variable gene segment (V beta) use of epidermal T cells in shave biopsies of psoriatic lesions. Our results show increased expression of V beta 3 and/or V beta 13.1 messages in the CD8+, but not CD4+, T cells in the lesions of a majority of patients studied. Sequence analysis of complementarity-determining region 3 (CDR3) of these two V beta genes from the skin demonstrated monoclonality or marked oligoclonality. A second biopsy from the same or different lesions, performed 3.5-8 months later in four patients, again revealed increased V beta 3 and/or V beta 13.1 expression and clonality. Moreover, in three of the four patients, the same V beta CDR3 rearrangement was found in both biopsies, although there was no V beta CDR3 homology between patients. In two patients in which V beta 3 and/or V beta 13.1 was not increased, an increase in V beta 17 gene use and clonality was found. The clonality of V beta sequence data indicates these cells are recruited and expanded in situ. The persistence of V beta 3-and/or V beta 13.1-bearing CD8+ T cells in lesions that did not undergo resolution suggests their role as effector cells rather than as regulatory cells.

Adult↗
PubMed1994

T cell receptor V beta 15 dominates the antiacetylcholine receptor response in Lewis rat T cell lines.

Ten Lewis rat T cell lines responsive to Torpedo californica acetylcholine receptor (AChR) were assayed for TCR V beta usage. All lines were CD4+, OX-22-, and exhibited reactivity to one or more AChR chains. Several different V beta s were expressed by these lines, but V beta 15 was dominant in 5 of 10 lines. Unique CDR3 sequences were observed among the 10 lines, although three of the V beta 15 rearrangements used J beta 1.4. These data suggest that V beta 15+ T cells are selected in the in vitro response to the antigenically complex AChR in the Lewis rat.

Amino Acid Sequence↗
PubMed1994

Jugular bulb saturation and cognitive dysfunction after cardiopulmonary bypass.

Inadequate cerebral oxygenation during cardiopulmonary bypass may lead to postoperative cognitive dysfunction in patients undergoing cardiac operations. A psychological test battery was administered to 255 patients before cardiac operation and just before hospital discharge. Postoperative impairment was defined as a decline of more than one standard deviation in 20% of tests. Variables significantly (p < 0.05) associated with postoperative cognitive impairment are baseline psychometric scores, largest arterial-venous oxygen difference, and years of education. Jugular bulb hemoglobin saturation is significant if it replaces arterial-venous oxygen difference in the model. Factors correlated with jugular bulb saturation at normothermia were cerebral metabolic rate of oxygen consumption (r = -0.6; p < 0.0005), cerebral blood flow (r = 0.4; p < 0.0005), oxygen delivery (r = 0.4; p < 0.0005), and mean arterial pressure (r = 0.15; p < 0.05). Three measures were significantly related to desaturation at normothermia and at hypothermia as well: greater cerebral oxygen extraction, greater arterial-venous oxygen difference, and lower ratio of cerebral blood flow to arterial-venous oxygen difference. We conclude that cerebral venous desaturation occurs during cardiopulmonary bypass in 17% to 23% of people and is associated with impaired postoperative cognitive test performance.

Aged↗
PubMed1994

Cultured epidermal autografts and allodermis combination for permanent burn wound coverage.

Cultured epidermal autografts (CEA) have been shown to be an effective permanent skin replacement for major burn injuries, but are more sensitive to adverse conditions than split thickness grafts (Clarke et al., 1988). Cuono et al. (1986, 1987) have described the successful use of engrafted allodermis as a wound bed for cultured grafts. We report on a method of preparing allodermis and grafting CEA in five patients with major burns (48-70 per cent TBSA, average 59.6 per cent). The average age was 38.8 years (20-60 years). All full thickness wounds were excised down to fat within 7 days of admission, and covered with meshed split thickness cryopreserved homograft. Over the ensuing 2-3 weeks, the homograft became engrafted. At surgery, the allo-epidermis was removed, leaving the dermal components as a viable bed for the CEA. Keratinocytes derived from a full thickness biopsy were grown to confluence by the method of Rheinwald and Green (1975), and 25 cm2 sheets were stapled to Vaseline gauze backings and applied to freshly excised wounds. Seven to 10 days after surgery, the gauze backings were removed. The average take ranged from 87-100 per cent (average 93.6 per cent). Follow-up for up to 4 years shows supple skin that has been durable, and resistant to trauma and infection.

Adult↗
PubMed1994

MAC reduction of isoflurane by sufentanil.

We have shown previously that a plasma fentanyl concentration of 1.67 ng ml-1 reduced the MAC of isoflurane by 50%. By comparing equal degrees of MAC reduction by sufentanil, we may determine the potency ratio of these opioids. Seventy-six patients were allocated randomly to receive predetermined infusions of sufentanil, and end-tidal concentrations of isoflurane in oxygen. Blood samples were obtained 10 min after the start of the infusion, and just before and after skin incision. Any purposeful movement by the patient was recorded. The MAC reduction of isoflurane produced by sufentanil was obtained using a logistic regression model. A sufentanil plasma concentration of 0.145 ng ml-1 (95% confidence limits 0.04, 0.26 ng ml-1) resulted in a 50% reduction in the MAC of isoflurane. At a plasma concentration greater than 0.5 ng ml-1, sufentanil exhibited a ceiling effect.

Adult↗
PubMed1994

Comfort measures in breastfeeding, primiparous women.

OBJECTIVE: To examine various comfort measures and evaluate their effects in alleviating nipple soreness. DESIGN: Prospectively randomized, experimental study. SETTING: Postpartum unit of a community teaching hospital. PATIENTS: Seventy-three primiparous, postpartum, breastfeeding women. INTERVENTIONS: Subjects were randomly assigned to four groups, with all women receiving instruction about breastfeeding and using one of the following treatments: warm moist tea bag compress, warm water compress, expressed milk massaged into the nipple and areola and air dried, instruction only (control group). The subjects completed a questionnaire each morning for 7 days regarding nipple soreness. MAIN OUTCOME MEASURE: Effect of treatments on postpartum nipple pain. RESULTS: Subjects in the warm water compress group demonstrated significantly less pain on Day 3 than did the tea or breast milk group. CONCLUSIONS: Anticipatory guidance by obstetric nurses may assist breastfeeding women in treating their pain nonpharmacologically.

Adult↗
PubMed1994

Continuing evolution of therapy for coronary artery disease. Initial results from the era of coronary angioplasty.

BACKGROUND: Survival after coronary artery bypass graft surgery (CABG) and medical therapy in patients with coronary artery disease (CAD) has been studied in both randomized trials and observational treatment comparisons. Over the past decade, the use of coronary angioplasty (PTCA) has increased dramatically, without guidance from either randomized trials or prospective observational comparisons. The purpose of this study was to describe the survival experience of a large prospective cohort of CAD patients treated with medicine, PTCA, or CABG. METHODS AND RESULTS: The study was designed as a prospective nonrandomized treatment comparison in the setting of an academic medical center (tertiary care). Subjects were 9263 patients with symptomatic CAD referred for cardiac catheterization (1984 through 1990). Patients with prior PTCA or CABG, valvular or congenital disease, nonischemic cardiomyopathy, or significant (> or = 75%) left main disease were excluded. Baseline clinical, laboratory, and catheterization data were collected prospectively in the Duke Cardiovascular Disease Databank. All patients were contacted at 6 months, 1 year, and annually thereafter (follow-up 97% complete). Cardiovascular death was the primary end point. Of this cohort, 2788 patients were treated with PTCA (2626 within 60 days) and 3422 with CABG (3080 within 60 days). Repeat or crossover revascularization procedures were counted as part of the initial treatment strategy. Kaplan-Meier survival curves (both unadjusted and adjusted for all known imbalances in baseline prognostic factors) were used to examine absolute survival differences, and treatment pair hazard ratios from the Cox model were used to summarize average relative survival benefits. For the latter, a 13-level CAD prognostic index was used to examine the relation between survival and revascularization as a function of CAD severity. The effects of revascularization on survival depended on the extent of CAD. For the least severe forms of CAD (ie, one-vessel disease), there were no survival advantages out to 5 years for revascularization over medical therapy. For intermediate levels of CAD (ie, two-vessel disease), revascularization was associated with higher survival rates than medical therapy. For less severe forms of two-vessel disease, PTCA had a small advantage over CABG, whereas for the most severe form of two-vessel disease (with a critical lesion of the proximal left anterior descending artery), CABG was superior. For the most severe forms of CAD (ie, three-vessel disease), CABG provided a consistent survival advantage over medicine. PTCA appeared prognostically equivalent to medicine in these patients, but the number of PTCA patients in this subgroup was low. CONCLUSIONS: In this first large-scale, prospective observational treatment comparison of PTCA, CABG, and medicine, we confirmed the previously reported survival advantages for CABG over medical therapy for three-vessel disease and severe two-vessel disease. For less severe CAD, the primary treatment choices are between medicine and PTCA. In these patients, there is a trend for a relative survival advantage with PTCA, although absolute survival differences were modest. In this setting, treatment decisions should be based not only on survival differences but also on symptom relief, quality of life outcomes, and patient preferences.

Angioplasty, Balloon, Coronary↗