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Biomedical subjects

N K Shah

Publications and source records attributed to N K Shah.

At least 37 records · Page 2Linked to original sources
PubMed1993

Isoflurane versus fentanyl: hemodynamic effects in cancer patients treated with anthracyclines.

Cancer patients treated with anthracycline derivatives are at risk for perioperative cardiovascular decompensation. The authors studied hemodynamic performance before, during, and after laparotomy in 14 anthracycline-treated patients with ovarian carcinoma. General anesthesia was maintained with 70% N2O in O2, and patients were randomized to receive supplementation with either isoflurane, 0.59% end-tidal +/- 0.04 (mean +/- SE), or fentanyl, 2.67 micrograms/kg +/- 0.49 as a loading dose, and a total dose of 7.16 micrograms/kg +/- 0.71. The degree of hemodynamic stability relative to the baseline was assessed. There was no obvious superiority of either technique prior to the skin incision. However, during and immediately after surgery, a clearer tendency for isoflurane-N2O to result in better hemodynamic stability was found. Isoflurane-N2O demonstrated significantly smaller change scores in systemic vascular resistance (SVR) and cardiac index (CI). At the start of surgery, the isoflurane-N2O change in SVR was 228.08 dyne.sec.cm-5 compared to 479.58 for the fentanyl patients, (P = 0.002); at the end of surgery the corresponding means were -12.09 and 703.14 dyne.sec.cm-5, respectively, (P = 0.002). Isoflurane-N2O was associated with significantly greater CI stability in the early postoperative period: the isoflurane-N2O mean change was -0.081 L/min/m2, versus -0.993 for the fentanyl-N2O patients, (P = 0.005). The authors conclude that anthracycline-treated patients who do not have overt evidence of cardiomyopathy can be safely anesthetized with either anesthetic technique. However, during surgery and in the early postoperative period, an isoflurane-N2O technique appears to offer better hemodynamic stability.

Acid-Base Imbalance↗
PubMed1993

The effect of sensor malpositioning on pulse oximeter accuracy during hypoxemia.

BACKGROUND: Previous studies have shown that pulse oximeters whose sensors are positioned improperly may yield erroneously low saturation (SpO2) values on normoxemic subjects. The behavior of oximeters with malpositioned sensors during hypoxemia has not been studied. The current study is aimed at determining the behavior of several different pulse oximeters over a wide range of arterial oxygen saturation (SaO2). METHODS: In each of 12 healthy volunteers, a radial artery cannula was inserted, and eight different pulse oximeters, five of which had malpositioned sensors, were applied. Subjects breathed controlled mixtures of nitrogen and oxygen to slowly vary their SaO2 from 100% to 70%. Arterial blood samples were analyzed and pulse oximeter data were recorded at five stable SaO2 values for each subject. RESULTS: The oximeters with malpositioned sensors vary greatly in their behavior, depending on both the actual SaO2 and the manufacturer and model. One oximeter underestimated saturation at all SaO2 values, while three others underestimated at high SaO2 and overestimated at low SaO2. Linear regression analysis shows a decrease in the slope of SpO2 versus SaO2 in most cases, indicating a loss of sensitivity to SaO2 changes. Between-subject variation in response curves was significant. CONCLUSIONS: The calibration curves of the pulse oximeters studied were changed greatly by sensor malpositioning. At low SaO2 values, these changes could cause the oximeter to indicate that a patient was only mildly hypoxemic when, in fact, hypoxemia was profound. It is recommended that sensor position be checked frequently and that inaccessible sensor locations be avoided whenever possible.

Adult↗
PubMed1993

Influence of hydration on the internal dynamics of hen egg white lysozyme in the dry state.

Proteins exist in a predominantly aqueous solvent environment. Hydration of the protein surface significantly affects many aspects of the protein's structure and function; these effects may be related to the molecular dynamics of the protein. We have examined the influence of hydration on the internal dynamics of hen egg white lysozyme using room-temperature phosphorescence from the intrinsic tryptophan residues. Powders of lyophilized lysozyme were hydrated in a phosphorimeter using a flow system that allowed for continuous manipulation of relative humidity over the range 0-92%; this system allowed us to directly compare intensity differences that result from changes in hydration. Lysozyme phosphorescence intensity decreased as a function of hydration over the entire relative humidity range; the decrease was not linear but appeared to occur in distinct phases. The phosphorescence intensity decays were multiexponential over the hydration range studied, and hydration had the largest influence on the long lifetime component. These data suggest that the protein exists in multiple, static conformations in the dry state and that water binding to polar (as opposed to charged) sites on the protein surface induces local and/or global softening of the protein structure.

Animals↗
PubMed1992

Karyotype at relapse following allogeneic bone marrow transplantation for chronic myelogenous leukemia.

Eighty-four patients underwent allogeneic or syngeneic bone marrow transplantation as therapy for chronic myelogenous leukemia (CML) during a 5-year period at The Johns Hopkins Oncology Center. We describe the karyotype at relapse in 19 patients who were Ph chromosome positive (Ph+) at diagnosis. Eighty-four percent of patients demonstrated clonal and/or nonclonal chromosome abnormalities in addition to the t(9;22)(q34;q11) at first detection of relapse or later during relapse. These abnormalities included: Ph plus additional clonal abnormalities (three patients), Ph plus nonclonal abnormalities (five patients), Ph plus additional clonal and nonclonal abnormalities (eight patients). Three patients had only the original Ph+ clone. The additional chromosome abnormalities were primarily structural, and entirely different from those most frequently observed during karyotypic evolution in conventionally treated CML. Chromosome 1 was most frequently involved, with 1q32 being the location of three clonal and two nonclonal abnormalities. Other sites included 6p21-22 (the site of two clonal abnormalities), 7p21-22, and 10q21 (the site of two clonal and one nonclonal abnormality each). Chromosomes 5 and 7q, regions of frequent involvement in acute nonlymphocytic leukemia that follows chemotherapy for other malignancies, were infrequently involved. The clinical significance of these additional abnormalities remains undetermined at this time.

Adult↗
PubMed1990

A clinical evaluation of pulse oximetry during thoracic surgery.

To evaluate the utility of pulse oximetry for monitoring oxygenation during thoracic surgery, pulse oximeter oxygen saturation (SpO2) values from the Nellcor N-100 (Nellcor Inc, Haywood, CA) and Novametrix model 500 (Medical Systems Inc, Wallingford, CT) were compared with simultaneous arterial saturation values (SaO2) in 20 patients. A total of 255 matched observations were recorded, and the data were divided for statistical analysis into preinduction of anesthesia and postinduction groups. The preinduction group showed a good correlation between SpO2 and SaO2 values, with both pulse oximeters consistently overestimating the SaO2. However, once anesthesia was induced, there was no longer any correlation for either of the pulse oximeters versus simultaneous SaO2 values, although on average, the SpO2 values were significantly higher than the corresponding SaO2 values. It was concluded that pulse oximetry is useful in following trends of oxygenation in patients with preexisting lung pathology undergoing thoracic surgery, but it cannot replace arterial blood gas sampling for the intraoperative management of respiratory function.

Anesthesia, General↗
PubMed1989

Comparison of the Bain and the ADE systems during controlled ventilation in adults.

It has been suggested that Humphrey's ADE system may be an improvement on the Bain system. To compare their efficiencies we have studied 20 anesthetized adults who had controlled ventilation established with a circle absorber system at a VE sufficient to maintain normocapnia. Patients were then randomly allocated to either a Bain or an ADE system. Fresh gas flow was sufficient to keep PE'CO2 constant for 30 min. The other circuit was then used for an additional 30 min. The required FGF was 54 ml kg-1 min-1 for the Bain system, compared with 67 ml kg-1 min-1 for the ADE system. We conclude that, during controlled ventilation, the ADE system is 25% less efficient than the Bain system.

Adult↗
PubMed1989

Intraoperative measurement of cerebral and tumor blood flow with laser-Doppler flowmetry.

A new technique, laser-Doppler flowmetry, has been used intraoperatively to measure blood flow responses in normal brain tissue and brain tumor to blood pressure and arterial blood gas alterations. We have observed that blood flow is reduced in most cerebral tumors, and that most tumors retain the normal response to changes in arterial blood gas; however, these responses are varied. One group of tumors in our study demonstrated an autoregulatory capacity; a second behaved passively--that is, blood flow changes followed blood pressure--while a third showed no response.

Animals↗
PubMed1989

A comparison of EEG determinants of near-awakening from isoflurane and fentanyl anesthesia. Spectral edge, median power frequency, and delta ratio.

To evaluate the efficacy of the computer-processed electro-encephalogram (EEG) for determining near-awakening from anesthesia, 14 patients were monitored during emergence from either isoflurane or fentanyl anesthesia at the termination of major surgical procedures. The raw EEG was obtained using bilateral frontomastoid electrodes. The compressed spectral array was digitized and recorded on disk in 4-s epochs using a Tractor Northern "Nomad" processor. The EEG information was displayed in four formats: 1) the frequency-power spectrum from 1-20 Hz, 2) the 95% power frequency, 3) the 50% power frequency, and 4) the ratio of power in the 8-20 Hz frequency range to the power in the 1-4 Hz frequency range (delta ratio). During emergence from isoflurane, there were obvious changes in the EEG frequency-power spectrum that occurred several minutes before patients opened their eyes in response to verbal stimuli. Although no one descriptor of EEG activity could be shown to be superior in anticipating when patients would respond by opening their eyes, awakening was always presaged by an abrupt decrease in power in the 1-4 Hz frequency range; this resulted in a marked increase in the delta ratio value. During emergence from fentanyl anesthesia, however, there was no obvious change in the overall EEG frequency-power spectrum. However, the same numeric EEG descriptors that were predictive of awakening from isoflurane also occurred during emergence from fentanyl, even though they usually occurred within 1 min of awakening. It is concluded that EEG criteria for identifying when patients will awaken from anesthesia are more reliable with isoflurane than with fentanyl.

Anesthesia Recovery Period↗
PubMed1978

Autonomic hyperreflexia during cystoscopy in patients with high spinal cord injuries.

Cystoscopic procedures were performed on 102 patients with histories of traumatic spinal cord lesion; 57 patients had sensorimotor levels above T7, and the remaining 45 patients had levels below T7. In 40 of the 57 patients (70 per cent) with levels above T7, signs and symptoms of autonomic hyperreflexia were seen during bladder distension and cystoscopy; the remaining 17 of these patients (30 per cent) did not have this response. No autonomic hyperreflexia was seen during cystoscopy in any of the 45 patients with sensorimotor levels below T7.

Adolescent↗