Anesthesia and analgesia
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Anesthesia and analgesia · Feb 2000
Randomized Controlled Trial Clinical TrialPropofol/sufentanil anesthesia suppresses the metabolic and endocrine response during, not after, lower abdominal surgery.
We investigated the influence of propofol/sufentanil anesthesia on metabolic and endocrine responses during, and immediately after, lower abdominal surgery. Twenty otherwise healthy patients undergoing abdominal hysterectomy for benign myoma received either continuous infusions of propofol supplemented with sufentanil (0.01 microg. kg(-1). min(-1), n = 10) or enflurane anesthesia (enflurane, n = 10). Plasma concentrations of glucose, lactate, free fatty acids, triglycerides, insulin, glucagon, cortisol, epinephrine, and norepinephrine were measured before, during, and 2 h after surgery. Pre- and postoperative endogenous glucose production (R(a) glucose) was analyzed by an isotope dilution technique by using [6,6-(2)H(2)] glucose. Propofol/sufentanil anesthesia prevented the increase in plasma cortisol and catecholamine concentrations and attenuated the hyperglycemic response during surgery without showing any difference after the operation. Mediated through a higher glucagon/insulin quotient (propofol/sufentanil 15 +/- 7 versus enflurane 8 +/- 4 pg/microU, P < 0.05), the R(a) glucose postoperatively increased more in the propofol/sufentanil than in the enflurane group (propofol/sufentanil 15.6 +/- 2.0 versus enflurane 13.4 +/- 2.2 micromol. kg(-1). min(-1), P < 0.05). ⋯ The concept of stress-free anesthesia using propofol combined with sufentanil is valid only during surgery. The metabolic endocrine stress response 2 h after the operation is more pronounced than after inhaled anesthesia.
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Anesthesia and analgesia · Feb 2000
Clinical TrialInterference of cerebral near-infrared oximetry in patients with icterus.
Near-infrared spectrophotometry assesses cerebral oxygen saturation (ScO(2)) based on the absorption spectra of oxygenated and deoxygenated hemoglobin and the translucency of biological tissue in the near-infrared band. In patients with icterus, however, bilirubin can potentially hinder cerebral oximetry. In 48 patients undergoing orthotopic liver transplantation, we related total plasma bilirubin to ScO(2) as determined from spectrophotometry with wavelengths of 733 and 809 nm. Before surgery, ScO(2) was 59% (15%-78%) (median with range) and bilirubin was 71 (6-619) micromol/L with a negative correlation (r = -0.72; P < 0.05). The 95% prediction interval included the lowest measurable ScO(2) of 15% at a bilirubin level of 370 micromol/L. During reperfusion of the grafted liver, the ScO(2) increased by 7% (-8% to 17%) (P < 0.05), and bilirubin did not influence this increase. In one patient, the ScO(2) remained below 15% despite a decrease in bilirubin from 619 to 125 micromol/L, suggesting that tissue pigmentation deposits also absorb light. In conclusion, bilirubin dampens the spectrophotometry-determined cerebral oxygen saturation at 733 and 809 nm. A bilirubin level of 370 micromol/L, tissue pigment deposits, or both, may render determination of cerebral oxygen saturation impossible. Even at high bilirubin values, changes in cerebral perfusion may be visible. ⋯ In 48 patients undergoing liver transplantation, the interference of icterus on cerebral oximetry by near-infrared light was investigated. Bilirubin absorbed the near-infrared light and lowered the measured cerebral oxygen saturation. Even at high bilirubin values, changes in cerebral oxygenation, as seen during reperfusion of the grafted liver, may be visible.
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Inhaled nitric oxide (NO) is a selective pulmonary vasodilator used to treat intraoperative pulmonary hypertension and hypoxemia. In contrast to NO delivered by critical care ventilators, NO delivered by anesthesia machines can be complicated by rebreathing. We evaluated two methods of administering NO intraoperatively: via the nitrous oxide (N(2)O) flowmeter and via the INOvent (Datex-Ohmeda, Madison, WI). We hypothesized that both systems would deliver NO accurately when the fresh gas flow (FGF) rate was higher than the minute ventilation (VE). Each system was set to deliver NO to a lung model. Rebreathing of NO was obtained by decreasing FGF and by simulating partial NO uptake by the lung. At FGF > or = VE (6 L/min), both systems delivered an inspired NO concentration ([NO]) within approximately 10% of the [NO] set. At FGF < VE and complete NO uptake, the N(2)O flowmeter delivered a lower [NO] (70 and 40% of the [NO] set at 4 and 2 L/min, respectively) and the INOvent delivered a higher [NO] (10 and 23% higher than the [NO] set at 4 and 2 L/min, respectively). Decreasing the NO uptake increased the inspired [NO] similarly with both systems. At 4 L/min FGF, [NO] increased by 10%-20% with 60% uptake and by 18%-23% with 30% uptake. At 2 L/min, [NO] increased by 30%-33% with 60% uptake and by 60%-69% with 30% uptake. We conclude that intraoperative NO inhalation is accurate when administered either by the N(2)O flowmeter of an anesthesia machine or by the INOvent when FGF > or = VE. ⋯ Inhaled nitric oxide (NO) is a selective pulmonary vasodilator. In a lung model, we demonstrated that NO can be delivered accurately by a N(2)O flowmeter or by a commercial device. We provide guidelines for intraoperative NO delivery.
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Anesthesia and analgesia · Feb 2000
Comparative StudyComparison of NAD 6000 and servo 900C ventilators in an infant lung model.
We compared the ability of the NAD 6000 (North American Dräger, Telford, PA) and the Servo 900C (Siemens-Elema AB, Solna, Sweden) anesthesia ventilators to maintain precise delivery of small tidal volumes (V(t)) and positive end-expiratory pressure using an infant test lung model. A variety of ventilator and lung model settings were selected to test clinical conditions simulating normal and extremely compromised lung function. Differences in ventilator output were analyzed by using an independent t-test with P <0.05 considered significant. With the ventilators set to deliver a V(t) of 30 mL, the actual delivered V(t) was significantly better for the NAD 6000 (25 +/- 2 mL) compared with the Servo 900C (18 +/- 3 mL), P <0.001. When the ventilators were set to deliver 100 mL V(t), their delivered V(t) were not significantly different, NAD 6000 (66 +/- 19 mL) and Servo 900C (60 +/- 12 mL), P = 0.09. The exhaled V(t) read by the anesthesia machines was significantly closer to the delivered V(t) for the NAD 6000 (11 +/- 9 mL) compared with the Servo 900C (37 +/- 11 mL), P < 0.001. Both ventilators maintained the end expiratory pressure delivered to the test lung within 2 cm H(2)O of the set positive end-expiratory pressure on average. As the conditions changed requiring the ventilator to develop a higher peak inflating pressure, both ventilators showed a decrease in V(t) delivered, which was proportionate to the tubing compression volume loss. ⋯ The NAD 6000 (North American Dräger, Telford, PA) and Servo 900C (Siemens-Elema AB, Solna, Sweden) are able to precisely deliver small Tidal Volumes. They both decreased in performance when tested under extreme conditions. Earlier studies of traditional anesthesia ventilators suggest that the NAD 6000 and Servo 900C are superior pediatric ventilators.