ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundPerioperative myocardial ischemia occurs in 20–40% of patients at risk for cardiac complications and is associated with a ninefold increase in risk for perioperative cardiac death, myocardial infarction, or unstable angina, and a twofold long‐term risk. Perioperative atenolol administration reduces the risk of death for as long as 2 yr after surgery. This randomized, placebo‐controlled, double‐blinded trial tested the hypothesis that perioperative atenolol administration reduces the incidence and severity of perioperative myocardial ischemia, potentially explaining the observed reduction in the risk for death.MethodsTwo‐hundred patients with, or at risk for, coronary artery disease were randomized to two study groups (atenolol and placebo). Monitoring included a preoperative history and physical examination and daily assessment of any adverse events. Twelve‐lead electrocardiography (ECG), three‐lead Holter ECG, and creatinine phosphokinase with myocardial banding (CPK with MB) data were collected 24 h before until 7 days after surgery. Atenolol (0, 5, or 10 mg) or placebo was administered intravenously before induction of anesthesia and every 12 h after operation until the patient could take oral medications. Atenolol (0, 50, or 100 mg) was administered orally once a day as specified by blood pressure and heart rate.ResultsDuring the postoperative period, the incidence of myocardial ischemia was significantly reduced in the atenolol group: days 0–2 (atenolol, 17 of 99 patients; placebo, 34 of 101 patients; P = 0.008) and days 0–7 (atenolol, 24 of 99 patients; placebo, 39 of 101 patients; P = 0.029). Patients with episodes of myocardial ischemia were more likely to die in the next 2 yr (P = 0.025).ConclusionsPerioperative administration of atenolol for 1 week to patients at high risk for coronary artery disease significantly reduces the incidence of postoperative myocardial ischemia. Reductions in perioperative myocardial ischemia are associated with reductions in the risk for death at 2 yr.

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundFentanyl produces a minimal reduction in the minimum alveolar concentration of sevoflurane to prevent response to a verbal command in 50% of patients (MACawake) at low but analgesic plasma concentrations. The reduction in MACawake, however, is still unknown at higher fentanyl concentrations. The reduction in the MAC of sevoflurane by fentanyl has not been described accurately. The purpose of this study was to determine the MACawakeand MAC reduction of sevoflurane by fentanyl.MethodsNinety‐two patients were randomly allocated to seven fentanyl concentration groups (target plasma concentrations of 0, 1, 1.5, 3, 6, 10, and 14 ng/ml). Responses to verbal command were observed for MACawakeassessment at predetermined sevoflurane concentrations. Thereafter, in patients whose target fentanyl concentration was 0 to 10 ng/ml, responses to skin incision were observed for MAC assessment at new steady‐state sevoflurane concentrations. The reduction in the MACawakeand MAC of sevoflurane by the measured fentanyl concentration was calculated.ResultsThere was an initial steep reduction in the MAC of sevoflurane by fentanyl, with 3 ng/ml resulting in a 59% MAC reduction. A ceiling effect was observed, with 10 ng/ml providing only a further 17% reduction in MAC. The initial reduction in MACawakewas not as steep as that in MAC. Fentanyl reduced MACawakeby approximately 24% at a plasma concentration of 3 ng/ml. Although the reduction curve of MACawakewas parabolic, no manifest ceiling effect was observed at concentrations administered in the present study.ConclusionsThe reduction in sevoflurane requirements for loss of consciousness and skin incision by fentanyl was determined. Fentanyl reduced both requirements, but the mode of the reduction was not comparable.

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundThe bispectral index (BIS) measures changes in the interfrequency coupling of the electroencephalogram (EEG). The purposes of this study were (1) to determine whether BIS correlates with responses to command during sedation and hypnosis induced by propofol or propofol and nitrous oxide, and (2) to compare BIS to targeted and measured concentrations of propofol in predicting participants' responses to commands.MethodsTwenty volunteers (15 men and 5 women, aged 22–50 yr) were given propofol by computer‐controlled infusion, and EEG was recorded for off‐line analysis of BIS. Responses to randomly ordered verbal commands or voice plus touch were measured with two categorical scales (CS1 and CS2, respectively). All subjects received a propofol infusion targeted to achieve effect site concentrations of 1, 2, 4, 2, 1, and 0 micro gram/ml. Ten participants had repeated infusion, whereas 10 others breathed 30% nitrous oxide and oxygen and received a propofol infusion targeted for 0.5, 1, 2, 4, 2, 1, 0.5, and 0 micro gram/ml. Five minutes after each targeted concentration had been reached, CS1, CS2, and arterial propofol concentration were determined. The area under the receiver operating characteristic curve was used to compare the accuracy of (1) BIS, (2) targeted propofol concentration, (3) measured concentration, and (4) treatment history as predictors of response.ResultsBispectral index was a strong predictor of CS1 and CS2 (P < 0.0001) and significantly more accurate than targeted or measured propofol concentrations (P < 0.0003 and P < 0.003, respectively). It also provided additional predictive power when combined with treatment history (P < 0.02). Nitrous oxide slightly decreased the probability of response at a given value of BIS (P < 0.05), but accuracy was unaffected.ConclusionsBispectral index accurately predicts response to verbal commands during sedation and hypnosis with propofol or propofol plus nitrous oxide. Accuracy is maintained in situations likely to be encountered during clinical use: when propofol concentrations are increasing or decreasing and when repeated measurements are made over time.

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundIt is not known whether inverse I:E ratio ventilation (IRV) offers any real benefit over conventional mechanical ventilation with positive end‐expiratory pressure (CMV‐PEEP) at similar levels of end‐expiratory pressure.MethodsThe effects of volume‐controlled and pressure‐controlled IRV (VC‐IRV and PC‐IRV, respectively) on V with dotA/Q with dot inequality were compared with those of CMV‐PEEP at a similar level of end‐expiratory pressure and with CMV without PEEP (CMV) in eight patients in the early stages of acute respiratory distress syndrome (ARDS). Respiratory blood gases, inert gases, lung mechanics, and hemodynamics were measured 30 min after the onset of each ventilatory mode.ResultsRecruitment of nonventilated, poorly ventilated (or both) but well‐perfused alveoli increased the partial pressure of oxygen (PaO sub 2) during CMV‐PEEP (+13 mmHg) and IRV‐VC (+10 mmHg; P < 0.05) compared with CMV. In contrast, PC‐IRV did not affect PaO2but caused a decrease in PaCO2(‐7 mmHg; P < 0.05). The latter was due to a concomitant decrease in dead space (P < 0.01) and shift to the right of V with dotA/Q with dot distributions. During PC‐IRV, the increase in the mean of blood flow distribution (mean Q; P < 0.01) without a change in the dispersion (log SD Q) did not result in an increase in PaO2, probably because it reflected redistribution of blood flow within well‐ventilated areas.ConclusionsShort‐term PC‐IRV improved carbon dioxide clearance, but the lung became less efficient as an oxygen exchanger. Furthermore, based on mean airway and plateau pressures, the risk of barotrauma was not reduced with this type of ventilation.

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundHeart rate (HR) or mean arterial blood pressure (MAP) may increase in response to incision despite the absence of a motor response. The authors hypothesized that the MAC‐BAR (minimum alveolar concentration of an anesthetic that blocks adrenergic response to incision) for isoflurane would exceed that for desflurane, and that fentanyl would decrease the MAC‐BAR for each anesthetic in a dose‐dependent manner.MethodsSeventy‐one patients were randomly allocated to one of six groups: desflurane or isoflurane without fentanyl or with 1.5 or 3 micro gram/kg fentanyl given intravenously 5 min before surgical incision. Anesthesia was induced with 2 mg/kg propofol given intravenously, and tracheal intubation facilitated with 0.1 mg/kg given intravenously. The first patient in each group received 1 MAC (end‐tidal) of the inhaled anesthetic in 60% nitrous oxide (0.55 MAC), balance oxygen, maintained for at least 10 min before incision. The response was considered positive if the HR or MAP increased 15% or more. If the response was positive, the end‐tidal concentration given to the next patient was 0.3 MAC greater; if the response was negative, the end‐tidal concentration was 0.3 MAC less. The MAC‐BAR level was calculated as the mean of four independent cross‐over responses in each group.ResultsDesflurane and isoflurane anesthesia with 60% nitrous oxide did not change HR (P > 0.05) and decreased MAP (P < 0.05) before incision. Plasma epinephrine and norepinephrine concentrations after anesthesia and before incision were normal in all groups. The MAC‐BAR level, without fentanyl, did not differ (P > 0.05) between desflurane (1.30 +/‐ 0.34 MAC [mean +/‐ SD]) and isoflurane (1.30 +/‐ 0.18 MAC). Fentanyl given at 1.5 micro gram/kg intravenously equivalently (P > 0.05) reduced the MAC‐BAR for desflurane (to 0.40 +/‐ 0.18 MAC; P <0.05) and isoflurane (to 0.55 +/‐ 0.00 MAC; P < 0.05), but a further increase in fentanyl to 3 micro gram/kg caused no greater decrease in the MAC‐BAR for desflurane (0.48 +/‐ 0.16 MAC) and isoflurane (0.40 +/‐ 0.30 MAC).ConclusionsClinically attainable doses of desflurane and isoflurane, in 60% nitrous oxide (0.55 MAC), block the cardiovascular response to surgical incision at 1.3 MAC. Fentanyl given at 1.5 micro gram/kg decreases the MAC‐BAR for each agent with no further decrease produced by 3 micro gram/kg fentanyl.

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundMajor orthopedic surgery can be associated with dramatic blood loss, thereby requiring high‐volume homologous transfusions in patients unable to benefit from blood salvage techniques. The effect of aprotinin on blood loss and transfusion requirements during orthopedic surgery for either the resection of malignancies of the removal of infected hardware was prospectively studied.MethodsTwenty‐three patients scheduled for orthopedic surgery of the hip, femur, or pelvis for sepsis or malignant tumors, all under general anesthesia, were randomly allocated to receive during operation, in a blinded manner, either aprotinin administered as a bolus of 1.10 sup 6 kallikrein inactivation units (KIU) followed by an infusion of 5 x 105KIU/h, or the equivalent volume of saline. The anesthesia and perioperative management, as well as the designated transfusion criteria, were standardized. The total blood loss of each patient was evaluated using intraoperative suction losses, sponge weights, and postoperative volumetric drainage. Homologous transfusion requirements were noted. Hemoglobin and hematocrit measures, as well as coagulation and fibrinolytic pathway explorations, were performed before and after surgery. Deep venous thrombosis prophylaxis was applied, and the incidence of this complication was assessed.ResultsTwelve patients received aprotinin. Aprotinin reduced the total blood loss from a median of 5,305 ml (range, 3,000–9,770 ml) to a median of 1,783 ml (range, 1,140–4,955 ml; P < 0.05). A blood loss reduction of 56% during surgery and 68% on discharge from the postanesthesia care unit was observed. Seven units (range, 4–16) of packed erythrocytes were transfused per patient in the placebo group, and 3 (range, 2–5) were transfused in the aprotinin group (P < 0.05). In the aprotinin group, platelet counts were higher, and postoperative prothrombin times and D. Dimer values were lower. The activated partial thromboplastin time values showed no significant difference between the two groups. No side effects were observed in the aprotinin group. A deep venous thrombosis developed in one patient in the placebo group.ConclusionAprotinin treatment during major orthopedic surgery significantly reduces both blood loss and consequent homologous blood transfusion requirements.

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundA cerebral oximeter measures oxygen saturation of brain tissue noninvasively by near infrared spectroscopy. The accuracy of a commercially available oximeter was tested in healthy volunteers by precisely controlling end‐tidal oxygen (PETO2) and carbon dioxide (PETCO2) tensions to alter global cerebral oxygen saturation.MethodsIn 30 healthy volunteers, dynamic end‐tidal forcing was used to produce step changes in PETO2resulting in arterial saturation ranging from [approximately] 70% to 100% under conditions of controlled normocapnia (each person's resting PETCO2) or hypercapnia (resting plus 7–10 mmHg). Blood arterial (SaO2) and jugular bulb venous (Sjvwith bar O2) saturations during each PETO2interval were determined by co‐oximetry. The cerebral oximeter reading (rSO2) and an estimated jugular venous saturation (Sjvwith bar O2), derived from a combination of SaO2and rSO2, were compared with the measured Sjvwith bar O2.ResultsThe Sjvwith bar O2was significantly higher with hypercapnia than with normocapnia for the same SaO2. The rSO sub 2 and Sjvwith bar O2were both highly correlated with S sub jv with bar O2for individual volunteers (mean r2= 0.91 for each relation); however, the slopes and intercepts varied widely among volunteers. In three of them, the cerebral oximeter substantially underestimated the measured SjvO2.ConclusionsDuring isocapnic hypoxia in healthy persons, cerebral oxygenation as estimated by near infrared spectroscopy precisely tracks changes in measured SjvO2within individuals, but the relation exhibits a wide range of slopes and intercepts. Therefore the clinical utility of the device is limited to situations in which tracking trends in cerebral oxygenation would be acceptable.

ISSN:0003-3022    

出版商:OVID    

年代:1998

数据来源: OVID