Browsing by Author "MENESES, G"

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    EFFECTS OF EXTRACORPOREAL-CIRCULATION ON RENAL-FUNCTION IN CORONARY SURGICAL PATIENTS
    (WILLIAMS & WILKINS, 1995) LEMA, G; MENESES, G; URZUA, J; JALIL, R; CANESSA, R; MORAN, S; IRARRAZAVAL, MJ; ZALAQUETT, R; ORELLANA, P
    We prospectively studied perioperative changes of renal function in 12 previously normal patients (plasma creatinine <1.5 mg/dL) scheduled for elective coronary surgery. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured with inulin and I-125-hippuran clearances before induction of anesthesia, before cardiopulmonary bypass (CPB), during hypo- and normothermic CPB, after sternal closure, and 1 h postoperatively. Renal and systemic vascular resistances were calculated. Urinary N-acetyl-beta-D-glucosaminidase (NAG) and plasma and urine electrolytes were measured, and free water, osmolal, and (creatinine clearances, and fractional excretion of sodium and potassium were calculated before and after surgery. I-125-hippuran clearance was lower than normal in all patients before surgery. During hypothermic CPB, ERPF increased significantly (from 261 +/- 107 to 413 +/- 261 mL/min) and returned toward baseline values during normothermia. GFR was normal before and after surgery and decreased nonsignificantly during CPB. Filtration fraction was above normal before surgery and decreased significantly during CPB (038 +/- 0.09 to 0.18 +/- 0.06). Renal vascular resistance (RVR) was high before surgery and further increased after sternotomy (from 18,086 +/- 6849 to 30,070 +/- 24,427 dynes . s . cm(-5)), decreasing during CPB to 13,9647 +/- 14,662 dynes . s . cm(-5). Urine NAG, creatinine, and free water clearances were normal in all patients both pre- and postoperatively. Osmolal clearance and fractional excretion of sodium increased postoperatively from 1.54 +/- 0.06 to 12.47 +/- 11.37 mL/min, and from 0.44 +/- 0.3 to 6.07 +/- 6.27, respectively. We conclude that renal function does not seem to be adversely affected by CPB. Significant functional alterations, such as decreased ERPF and increased RVR, were found before and during surgery, preceding CPB. These periods could contribute to postoperative renal dysfunction.
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    THERMOREGULATORY VASOCONSTRICTION INCREASES THE DIFFERENCE BETWEEN FEMORAL AND RADIAL ARTERIAL PRESSURES
    (1994) URZUA, J; SESSLER, DI; MENESES, G; SACCO, CM; CANESSA, R; LEMA, G
    Objective. Thermoregulatory vasoconstriction locally increases arterial wall tension and arteriolar resistance thereby altering physical properties of the arteries. The arterial pressure waveform is an oscillatory phenomenon related to those physical characteristics; accordingly, we studied the effects of thermoregulatory vasomotion on central and distal arterial pressures, using three hydraulic coupling systems having different dynamic responses. Methods. We studied 7 healthy volunteers. Central arterial pressure was measured from the femoral artery and distal pressure was measured from the radial artery, using 10.8-cm long, 20-gauge catheters. Three hydraulic coupling systems were used: (1) a 10-cm-long, 2-mm internal diameter connector; (2) a 150-cm-long, 1-mm internal diameter connector (Combidyn 520-5689, B. Braun, Melsungen, Germany); (3) a 180-cm long, 2-mm internal diameter connector(Medex MX564 and MX562, Medex Inc., Hillard, OH). Brachial artery pressure was measured oscillometrically. Core temperature was measured at the tympanic membrane. The vasomotor index, defined as finger temperature minus room temperature, divided by core temperature minus room temperature, was used to estimate the degree of vasoconstriction. Constriction was considered near maximal when the index was less than 0. 1, and minimal when it exceeded 0.75. Measurements were taken every 3 min. Baseline readings were obtained when subjects were warm. They then were cooled by exposure to 20-degrees-C to 22-degrees-C room air and a circulating-water mattress set at 4-degrees-C until index was less than 0.1. They then were rewarmed by increasing water temperature to 42-degrees-C and adding a forced-air warmer until the vasomotor index exceeded 0.75. Data were analyzed by ANOVA and linear regression. Results. Thermoregulatory vasoconstriction was associated with marked arterial pressure waveform changes. Radial pressure showed, in lieu of a dicrotic notch, large oscillations of decreasing amplitude. Femoral pressure showed a single diastolic oscillation of smaller amplitude. The waveforms appeared different, depending on the hydraulic coupling system used, artifact being more marked with the longer connectors. On the average, radial systolic pressure exceeded femoral systolic pressure during vasoconstriction; however, during vasodilatation, femoral systolic pressure exceeded radial systolic pressure (p < 0.05). Oscillometric measurements underestimated systolic pressure, and did so more markedly during vasoconstriction. There were no differences in the values of mean and diastolic pressures. Conclusion. Thermoregulatory vasoconstriction alters radial arterial pressure waveform, artifactually increasing its peak systolic pressure compared with the femoral artery. Poor dynamic responses of recording systems further distort the waveforms. Consequently, radial artery pressure may be misleading in vasoconstricted patients.