Efficacy of a heat and moisture exchanger in inhalation anesthesia at two different flow rates

In general anesthesia with endotracheal intubation, a circle system with a heat and moisture exchanger (HME) and a low total flow is often used to prevent hypothermia and to maintain inspired gas humidity. The purpose of the present study was to compare the inspired gas humidity and body temperature, in general anesthesia with or without an HME at two different total flow rates. Eighty patients (American Society of Anesthesiologists [ASA] I or II) scheduled to undergo either orthopedic or head and neck surgery were studied. They were divided into four groups, of 20 patients each: total flow of 2 l·min⁻¹ with (group HME2L) or without (group 2L) HME, and a total flow of 4 l·min⁻¹ with (group HME4L) or without (group 4L) HME. The relative and absolute humidity and pharyngeal and inspired gas temperatures were measured for 2 h after endotracheal intubation. The relative humidity was not significantly different among groups 2L, HME2L, and HME4L. Group 4L had significantly lower absolute humidity than group 2L. The pharyngeal temperature did not decrease significantly for 2 h in any of the groups. During general anesthesia with a total flow of 2 l·min⁻¹ in 2 h, HME might not be necessary, while with a total flow of 4 l·min⁻¹, HME could be useful to maintain inspired gas humidity.     

Clinical evaluation of low-flow sevoflurane anaesthesia for paediatric patients

Background: Sevoflurane expenditure, inspired gas humidity, temperature, soda lime temperature, and compounds A and B were measured during high and low fresh gas flow anaesthesia in paediatric patients. Methods: Sixty ASA 1 or 2 paediatric patients were randomly allocated to two groups: low-flow circle anaesthesia (LFA) patient group (n=30) and high-flow circle anaesthesia (HFA) patient group (n=30). Initial fresh gas flow (FGF) was 4 l · min^?1 of nitrous oxide and 2 l · min^?1 of oxygen in both groups. This FGF of 6 l · min^?1 was maintained in the HFA group. After 10 min of HFA, the FGF was reduced to 600 ml · min^?1 (nitrous oxide and oxygen 300 ml · min^?1 each) in the LFA group. Results: Sevoflurane expenditure during LFA was about 1/7 of that during HFA (3.3±0.2 ml · h^?1 · vol.%^?1 compared to 22.8±0.6 ml · h^?1 · vol.%^?1, mean±SEM, respectively). Absolute humidity in the LFA patients was 4 times higher than that in the HFA patients (22.8±2.4 g · m^?3, 5.6±3.4 g · m^?3 respectively). There was no significant difference in the inspiratory gas temperature between the LFA (28.5±0.6°C) and HFA (26.9±1.3°C) groups. There was significant difference in the mean highest soda lime temperature between the LFA (35.5±1.2°C) and HFA (28.7±1.2°C) groups. The mean highest concentration of compound A was 12.2±3.8 ppm in the LFA group. The mean highest concentration of compound B was less than 1 ppm. Compounds A and B were below detectable level in the HFA group. Conclusion: In conclusion, sevoflurane used for paediatric patients in a circle system with a fresh gas flow of 0.6 l · min^?1 resulted in a significantly reduced sevoflurane expenditure, higher inspired absolute humidity, but not temperature, compared to a fresh gas flow of 6 l · min^?1. Low levels of compounds A and B were detected.     

The effect of heat-moisture exchanger and closed-circuit technique on airway climate during desflurane anesthesia

Purpose We assessed whether closed-circuit anesthesia (CCA) could provide a more favorable airway climate than semiclosed anesthesia (SCA), and we also determined the beneficial effect of heat moisture exchangers (HMEs) on the preservation of airway climate during desflurane anesthesia. Methods Forty patients scheduled for colorectal surgery (n = 10 for each group) were randomized to receive a fresh gas flow of 250 or 3000 ml·min⁻¹ with or without HMEs. Anesthesia was maintained by adjusting the inspired concentration of 6% desflurane. Absolute moisture and temperature of inspired gases were measured as the baseline value first at 5 min after tracheal intubation, and then at 10, 20, 45, 60, 90, and 120 min after the induction of anesthesia. Results At 120 min, the inspiratory humidity and temperature were higher in CCA than in SCA. The HME led to major improvements of the humidity (from 22.1 to 35.7 mg H₂O·l⁻¹) and temperature (from 23.6°C to 31.5°C) of anesthetic gases in the CCA group. Conclusion CCA was much more advantageous than SCA for maintaing the patient’s airway climate during the 2-h study. The beneficial effect of HME on the airway climate should be emphasized, especially in patients undergoing general anesthesia.     

A comparison between low-flow leak test and oxygen flush leak test

Purpose. The clinical efficacy of two methods of preanesthetic leak test,namely the oxygen flush leak test (OFLT) and the low-flow leak test (LFLT), was compared regarding their ability to detect leakage in the anesthesia circuit and their accuracy. Methods. Examinees comprised 16 staff anesthesiologists and 7 physicians undergoing anesthesia training at our institution. They performed the two leak tests on anesthesia machines with some intentional leaks (0.1–1.0 l·min⁻¹). The leakage detection rates (LDR) were analyzed by the χ²-test. The ability to detect leaks was measured by recording how many leaks were detected by 50% (LDR₅₀) and 95% (LDR₉₅) of the examinees. Results. The LDRs in the two tests were significantly different (χ²- analysis, P < 0.0001). Both LDR₅₀ and LDR₉₅ for the LFLT (0.23 and 0.41 l·min⁻¹, respectively) were smaller than the values for the OFLT (0.37 and 0.82 l·min⁻¹, respectively). The sensitivity and specificity of the LFLT (0.97 and 0.84, respectively) were higher than those of the OFLT (0.78 and 0.80, respectively). Conclusion. The LFLT was found to be superior to the OFLT regarding leak detection and reliability. We therefore recommend the LFLT for preanesthetic leak testing. Received: June 23, 1999 / Accepted: July 5, 2000     

Effect of peak inspiratory flow on gas exchange, pulmonary mechanics, and lung histology in rabbits with injured lungs

Purpose The aim of this study was to evaluate, using a rabbit model, the little-known effect of different levels of peak inspiratory flow on acutely injured lungs. Methods Fourteen male rabbits (body weight, 2711 ± 146 g) were anesthetized and their lungs were injured by alveolar overstretch with mechanical ventilation until Pa_O2 was reduced below 300 mmHg. Injured animals were randomly assigned to: the P group—to receive pressure-regulated volume-control ventilation (PRVCV; n = 7); and the V group—to receive volume-control ventilation (VCV; n = 7). Other ventilator settings were: fraction of inspired oxygen (FI_O2), 1.0; tidal volume, 20 ml·kg⁻¹; positive end-expiratory pressure (PEEP) 5 cmH₂O; and respiratory rate, 20 min⁻¹. The animals were thus ventilated for 4 h. Throughout the protocol, ventilatory parameters and blood gas were measured every 30 min. After the protocol, the lung wet-to-dry ratio and histological lung injury score were evaluated in the excised lungs. Results Throughout the protocol, peak inspiratory flow and mean inspiratory flow values in the P group were significantly higher than those in the V group (26.7 ± 5.0 l·min⁻¹ vs 1.2 ± 0.2 l·min⁻¹, and 4.3 ± 0.3 l·min⁻¹ vs 1.1 ± 0.1 l·min⁻¹; P < 0.05). The wet-to-dry ratio in the P group was also significantly higher than that in the V group (7.7 ± 0.9 vs 6.3 ± 0.5; P < 0.05). More animals in the P group than in the V group had end-of-protocol Pa_O2/FI_O2 ratios below 200 mmHg (43% vs 0%; P = 0.06). Conclusion In rabbits with injured lungs, high peak inspiratory flow with high tidal volume (V_T) reduces the Pa_O2/FI_O2 ratio and increases the lung wet-to-dry ratio.     

Effect of infraorbital nerve block under general anesthesia on consumption of isoflurane and postoperative pain in endoscopic endonasal maxillary sinus surgery

Purpose. The efficacy of infraorbital nerve block in reducing isoflurane consumption and postoperative pain was evaluated in patients undergoing endoscopic endonasal maxillary sinus surgery (ESS) under general anesthesia. Methods. Fifty patients were randomly allocated to either the block group (n = 15) or the nonblock group (n = 25). After the establishment of general anesthesia with isoflurane, nitrous oxide, and oxygen, the patients received infraorbital nerve block with 1.0 ml of either 0.5% bupivacaine (block group) or normal saline (nonblock group) administered into the soft tissue in front of the infraorbital foramen. Systolic blood pressure during anesthesia and surgery was maintained at 85–90 mmHg by adjusting the inspiratory concentration of isoflurane, and its consumption was evaluated in both groups. Pain intensity at 15 min after the end of anesthesia was also evaluated on a five-point pain scale. Results. The consumption of isoflurane under a fresh gas flow of 6 l·min⁻¹ was 17.3 ± 6.5 ml·kg⁻¹·h⁻¹ (mean ± SD) in the block group and 27.4 ± 9.4 ml·kg⁻¹·h⁻¹ in the nonblock group during surgery (P < 0.001). Nicardipine was required during surgery less frequently in the block group than in the nonblock group (P < 0.01). Postoperative pain intensity was lower in the block group than in the nonblock group (P < 0.01). Conclusion. General anesthesia combined with infraorbital nerve block is effective in reducing the consumption of isoflurane and postoperative pain intensity in ESS. Received: April 4, 2000 / Accepted: February 13, 2001     

Comparison of heart rate changes after neostigmine-atropine administration during recovery from propofol-N2O and isoflurane-2O anesthesia

Purpose. Propofol augments the reduction of heart rate (HR) in combination with cholinergic agents and attenuates the HR response to atropine. We examined whether propofol anesthesia was associated with an increased incidence and extent of bradycardia after neostigmine-atropine administration compared with the effects of isoflurane anesthesia. Methods. Thirty-six adult patients were randomly assigned to two groups (n = 18 each): the propofol group patients were anesthetized with propofol (5–10 mg·kg⁻¹·h⁻¹)-₂O-fentanyl, and the isoflurane group patients were anesthetized with isoflurane (0.5%–1.0%)-₂O-fentanyl. When surgery was completed, anesthetics were discontinued, and then a mixture of neostigmine 0.05 mg·kg⁻¹ and atropine 0.02 mg·kg⁻¹ was injected intravenously over 20 s. Blood pressure (BP) and HR were measured noninvasively at 1-min intervals for 10 min. Results. At the completion of the surgery, the average infusion rate of propofol was 6.2 ± 1.7 mg·kg⁻¹·h⁻¹, and the average inspired concentration of isoflurane was 0.73 ± 0.15%. Immediately before the neostigmine-atropine injections, HR and mean BP were similar in the two groups. The maximum increase in HR after the neostigmine-atropine injections was significantly less in the propofol group than in the isoflurane group (16 ± 9 and 34 ± 6 beats·min⁻¹, respectively, P < 0.01). The subsequent maximum decrease in HR was greater in the propofol group than in the isoflurane group (−9 ± 4 and −5 ± 4 beats·min⁻¹, respectively; P < 0.01). The incidence of bradycardia (HR < 50 beats·min⁻¹) after neostigmine-atropine injection was greater in the propofol group than in the isoflurane group (61% and 28%, respectively; P < 0.01). Conclusion. We conclude that propofol anesthesia attenuates the initial increases in HR, enhances the subsequent decreases in HR, and increases the incidence of bradycardia after neostigmine-atropine injections compared with the effects of isoflurane anesthesia. Received: May 21, 2001 / Accepted: August 29, 2001     

Comparison between in vivo and in vitro pharmacokinetics of succinylcholine in humans

Purpose. To compare the in vivo and in vitro pharma-cokinetics of succinylcholine (SCh) in humans. Methods. A bolus of SCh 1 mg·kg⁻¹ (n = 7) or 2 mg·kg⁻¹ (n = 11) was given to 18 patients anesthetized with thiopental. Arterial blood samples for determination of in vivo SCh concentrations were collected every 30 s for 5 min. Another 20-ml blood sample was obtained before induction of anes-thesia for determination of in vitro SCh. Concentrations of SCh were measured by high-performance liquid chromato-graphy. In vivo and in vitro concentrations of SCh vs time data were analyzed by the one-compartment model. Results. The respective in vivo and in vitro pharmacokinetic parameters (SCh 1 mg·kg⁻¹ vs SCh 2 mg·kg⁻¹) were as follows: Plasma clearance was 4.17 ± 2.37 and 1.85 ± 0.28 l·min⁻¹, P < 0.05, vs 2.91 ± 2.01 and 1.27 ± 0.43 l·min⁻¹, P < 0.05. Elimination half-life was 25.4 ± 10.6 and 47.4 ± 5.4 s, P < 0.002 vs 26.3 ± 10.0 and 75.2 ± 21.8 s, P < 0.00005. Conclusion. These results suggest that the rapid disap-pearance of SCh from the circulation is due to diffusion out of the blood vessels rather than to enzymatic hydrolysis. Received for publication on August 31, 1998; accepted on May 11, 1999     

Fresh gas flow changes during controlled mechanical ventilation with the circle breathing system have significantly greater effects on the ventilatory parameters of toddlers compared with children*

Fresh gas flow into a circle system can affect the delivered minute ventilation because fresh gas flow augments the flow delivered by the ventilator bellows during inspiration. After establishing a stable ventilatory pattern with 3.0 l·min^-1 fresh gas flow into a circle system, changes in peak inflation pressure, minute ventilation and end-tidal carbon dioxide were measured at 1.5 l·min^-1 and 6.0 l·min^-1 in 10 toddlers (10–20 kg) and 10 children (30–60 kg). Changes in all variables were observed but these changes were greater in toddlers compared with children (P < 0.001). Some toddlers were noted to have as much as a 37% change in ventilatory parameters when fresh gas flow was altered between 1.5 and 6.0 l·min^-1. Whenever changes are made in fresh gas flow, compensatory changes in minute ventilation should be considered to avoid unintended hyperventilation or hypoventilation. This is especially important during anaesthesia for toddlers.     

Renal function in surgical patients after administration of low-flow sevoflurane and amikacin

Purpose. Compound A, a degradation product of sevoflurane, is nephrotoxic in rats, while aminoglycosides induce nephrotoxic injury in humans. Combining an aminoglycoside with a known nephrotoxin can enhance nephrotoxicity. We investigated the effects of aminoglycosides on renal function in surgical patients anesthetized with low-flow sevoflurane. Methods. We compared the urinary excretion of several biochemical markers (such as total protein, albumin, β₂-microglobulin, glucose, and N-acetyl-β-glucosaminidase [NAG]) in an amikacin group (n = 18) and a control group (n = 19) of surgical patients anesthetized with low-flow anesthesia (1 l·min⁻¹) with sevoflurane. All patients received cefotiam as an antibiotic perioperatively. In addition, the amikacin group received amikacin, an aminoglycoside, given intravenously twice a day (400 mg per day) from immediately after the induction of anesthesia to day 2 after anesthesia. Results. Duration of anesthesia and mean compound A concentration were 5.2 ± 1.4 h and 27.2 ± 8.7 ppm (mean ± SD) in the amikacin group, and 5.1 ± 1.7 h and 27.1 ± 7.8 ppm in the control group respectively (P > 0.05). The two groups did not differ in clinical laboratory baseline values (blood urea nitrogen and serum creatinine concentration). There were no significant differences between the groups in either the maximum or the average values for the urinary excretion of biochemical markers after anesthesia. Conclusion. Our study demonstrates that there is no synergic effect of compound A and amikacin on nephrotoxicity in humans. Received: February 14, 2001 / Accepted: August 10, 2001     

Effect of external high-frequency oscillation on severe cardiogenic pulmonary edema

Effective gas exchange can be maintained in animals without endotracheal intubation using external high-frequency oscillation (EHFO). The aim of this study was to evaluate the effect of EHFO in patients with respiratory failure due to severe cardiogenic pulmonary edema. Seven patients were ventilated with EHFO for 2h at 60 oscillations·min⁻¹, with a cuiras pressure of 36 cmH₂O (−26 to +10) and an inspiratory to expiratory ratio of 1:1, with EHFO. Blood gas values and hemodynamic parameters were measured. Significant increases were noted in cardiac index (2.3±0.5 to 2.5±0.5 l·m⁻²;P<0.05), stroke volume index (24±7 to 28±8 ml·m⁻²;P<0.05), and arterial O₂ pressure (Pao₂) (70±4 to 95±23 mmHg;P<0.01) without a change in pulmonary artery wedge pressure at 1 h after EHFO. The respiratory rate decreased from 28±3 to 22 ±3 breaths·min⁻¹ at 5 min after the termination of EHFO (P <0.01). Arterial CO₂ pressure (Paco₂) did not, however, decrease. Increased stroke volume without a change in pulmonary artery wedge pressure (preload) suggests either improved inotropic function of the left ventricle or reduced left ventricular afterload with EHFO. The use of EHFO may be effective not only for gas exchange but also for left ventricular function in patients with severe cardiogenic pulmonary edema.     

Intravenous famotidine does not always change core temperature during general anesthesia

It has been reported that oral premedication with the H₂ receptor antagonist famotidine augmented intraoperative hypothermia. We again investigated whether the H₂ receptor antagonist famotidine significantly affected body temperature during open abdominal surgery under general anesthesia. We studied 20 female patients undergoing elective gynecological surgery. Participating patients were assigned randomly to one of two regimens: (1) 10 ml saline given intravenously just before induction of general anesthesia or (2) 20 mg famotidine in 10 ml saline given just before induction of general anesthesia. General anesthesia was induced by 2 mg·kg⁻¹ propofol and 0.1 mg·kg⁻¹ vecuronium. After tracheal intubation, anesthesia was maintained with sevoflurane (1%–2%) in nitrous oxide (2 l·min⁻¹) and oxygen (1 l·min⁻¹) along with 1–2 μg·kg⁻¹ fentanyl as needed. Tympanic temperature (T_Tym) was measured as the core temperature, and arteriovenous perfusion of the fingertip was evaluated using the forearmminus-fingertip skin-surface temperature gradient (Grad_a–f). T_Tym gradually and significantly decreased in both groups during anesthesia, and no significant differences in these values were observed between the two groups. Grad_a–f did not differ significantly between the two groups during anesthesia. We conclude that intravenous famotidine does not always change the core temperature during general anesthesia.     

Hemodynamic effects of KRN2391 (potassium channel opener) in halothane-anesthetized dogs

The cardiovascular responses to an infusion of KRN2391, a potassium channel opener, was studied in halothane-anesthetized dogs. Intravenous administration of KRN2391 at 1.0 and 5.0 μg·kg⁻¹·min⁻¹ for 60 min produced dose-dependent decreases in mean arterial pressure (MAP) and systemic vascular resistance (SVR) associated with dose-dependent increases in the cardiac index (CI) and stroke volume index (SVI) but was not accompanied by an increase in heart rate (HR). The maximum decrease in MAP during the infusion of KRN2391 at 1.0 and 5.0 μg·kg⁻¹·min⁻¹ was −13±7% (P<0.01) and −37±10% (P<0.01), respectively. The maximum reduction in SVR after 1.0 and 5.0 μg·kg⁻¹·min⁻¹ was −20±11% (P<0.01) and −60±16% (P<0.01), respectively. A KRN2391 infusion of 1.0 and 5.0 μg·kg⁻¹·min⁻¹ increased Cl a maximum of 11±13% (P<0.05) and 65±33% (P<0.01), respectively. KRN2391 1.0 μg·kg⁻¹·min⁻¹ showed a tendency to increase SVI but this change was not significant, KRN2391 5.0 μg·kg⁻¹·min⁻¹, however, produced a significant increase in SVI. The present results demonstrate that the decrease in MAP and the increases in CI and SVI caused by KRN2391 are due to a reduction in the afterload. Therefore, we conclude that these cardiovascular profiles of KRN2391 may be benificial in perioperative uses including the control of systemic blood pressure and the treatment of hypertension during halothane anesthesia in clinical practice.     

The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system

The heat and humidity in a low-flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 2 l.min⁻¹) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (5 l.min⁻¹) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 5 l.min⁻¹ fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. Thirty minutes after the start of anaesthesia a control measurement was performed, after which a heat and moisture exchanger was inserted into the breathing system of the three groups randomly allocated to have one. Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low-flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l⁻¹) but at a fresh gas flow of 5 l.min⁻¹ there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.     

Comparison of cuffed, uncuffed tracheal tubes and laryngeal mask airways in low flow pressure controlled ventilation in children

Background : The use of low flow circle systems necessitates a ‘leak free’ breathing system which is commonly achieved by using a cuffed tracheal tube (TT). We hypothesized that low flow circle system anesthesia can equally effectively be achieved by using the LMA in pediatric anesthesia. Methods : Following local ethics committee approval we randomly recruited 45 patients scheduled for elective surgery and requiring mechanical ventilation into three groups (cuffed TT, uncuffed TT and LMA group, n = 15). The size of the TT was determined by means of the formula (age/4) + 4.5 for uncuffed and (age/4) + 4 for cuffed TT whereas the size of the LMA size was dependent on weight. Following induction of anesthesia and muscle paralysis patients were ventilated with pressure controlled ventilation through a pediatric circle system and the lowest fresh gas flow (FGF) determined. Results : The FGF achieved were (median and range) 0.20 (0.2–0.25) l·min^?1 for the LMA group, 0.20 (0.2–0.4) l·min^?1 for the cuffed TT group and 1.15 (0.2–4.75) l·min^?1 for the uncuffed group. The differences between the LMA and cuffed TT compared with the uncuffed TT were significant (P < 0.0001 and P = 0.0002, respectively). The difference in FGF between LMA and cuffed TT was not significant. Conclusion : We conclude that pressure controlled ventilation using an LMA is an alternative to a cuffed TT during low flow circle system anesthesia in children. Low FGF is unlikely to be achieved consistently using an uncuffed TT because of a substantial leak.     

Preservation of humidity and heat of respiratory gases in spontaneously breathing, tracheostomized patients

Background : Ventilation with endotracheal intubation bypasses the upper airway and the normal heat and moisture exchanging process of inspired gases. A continuous loss of moisture and heat occurs and predisposes patients to serious airway damage. We therefore prospectively studied one heated humidifier system, one cold humidifier system and one heat and moisture exchanger in spontaneously breathing, tracheostomized intensive care unit patients to determine the ability to preserve patients' heat and water. Methods : Following a randomized order, 10 patients were spontaneously ventilated for 24-h periods with the Nam 35r? humidifier (Europe Medical, France, a cold water humidifier), the heat and moisture exchanger Trach-Ventr? (Gibeck, Sweden), and the Aerodyner? humidifer (Kendall, USA). In each patient, during the inspiration phase, the following measurements were performed: mean values of temperature and relative humidity of inspired gases. The absolute humidity was calculated. Values were obtained in each patients after 40 min and 24 h. Results : The Trach-Ventr? filter and the Aerodyner? humidifier had better humidification and thermic capacities than the Nam 35r? humidifier (P<0.001). With the Nam 35r? humidifier, no patient had temperature of inspired gas >29°C. Concerning absolute humidity of inspired gases, the Nam 35r? humidifier achieved a lower performance than the other two tested systems (P<0.001). Conclusion : In spontaneously breathing, tracheostomized intensive care unit patients, the Trach-Ventr? heat and moisture exchanger and the Aerodyner? heated system achieved satisfactorily preservation of heat and humidity of inspired gases.     

Effects of olprinone on hepatosplanchnic circulation and mitochondrial oxidation in a porcine model of endotoxemia

Purpose This study was performed in order to assess the effects of olprinone, a phosphodiesterase III inhibitor, on hepatic oxygen delivery (DO₂H), oxygen consumption (VO₂H), and mitochondrial oxidation in the liver of a porcine endotoxemia model. Methods Fourteen pigs received continuous infusion of endotoxin via the portal vein for 240 min. From t = 150 to t = 240 min, animals were randomly divided into two groups to receive saline (control [CONT]; n = 7), or olprinone (OLP; n = 7) via the central vein. Results In the OLP group, prior to olprinone treatment at 150 min, endotoxin induced significant decreases in the cardiac index (CI; from 120 ± 31 to 65 ± 13 ml·kg⁻¹·min⁻¹; P < 0.01) and DO₂H (from 3.58 ± 0.81 to 1.55 ± 0.49 ml·kg⁻¹·min⁻¹; P < 0.01), while VO₂H was maintained. After administration of olprinone (from t = 150 to t = 240 min), CI was unchanged, while DO₂H increased from 1.55 ± 0.49 to 1.93 ± 0.38 ml·kg⁻¹·min⁻¹ (P < 0.01) and VO₂H increased from 0.42 ± 0.28 to 0.69 ± 0.38 ml·kg⁻¹·min⁻¹ (P < 0.01). At t = 240 min, the oxidation level of cytochrome aa3 was significantly higher in the OLP group than in the CONT group (OLP, 66.2 ± 19.3% vs CONT, 26.4 ± 17.3%; P < 0.01). Conclusion Our data for this porcine endotoxemia model suggest that olprinone may have beneficial therapeutic effects in restoring not only systemic and hepatic circulation but also mitochondrial oxidation in the liver.     

Comparison of renal function under deliberate hypotension during epidural plus light-enflurane anesthesia and during enflurane anesthesia

We compared the effects of deliberate hypotension induced with trimethaphan on renal function and renal tubular damage under combined epidural and light-enflurane anesthesia (epidural group) and enflurane anesthesia alone (enflurane group). The mean arterial blood pressure was maintained at 50–55 mm Hg for 2.5 h in both groups using continuous infusion of trimethaphan. The urine volume and free water clearance were significantly greater in the epidural group than in the enflurane group [1.8±1.8 (SD)vs 0.4±0.3 ml·kg⁻¹·h⁻¹ and 0.81±1.30vs −0.15±0.22 ml·min⁻¹, respectively] (P<0.05). The creatinine clearance and fractional sodium excretion rate did not differ significantly between the two groups. Urinary excretion of norepinephrine was significantly less in the epidural group than in the enflurane group (P<0.05); however, epinephrine excretion did not differ. Urinary excretion ofN-acetyl-β-d-glucosaminidase was significantly less in the epidural group than in the enflurane, group (4.2±2.5vs 12.2±4.6 U·g⁻¹ CR) (P<0.01). The plasma antidiuretic hormone concentration was significantly lower in the epidural group compared to the enflurene group (13±23vs 57±42 pg·ml⁻¹) (P<0.05). No significant difference in plasma atrial natriuretic peptide concentration was found between the groups. We conclude that renal function during trimethaphan-induced hypotension is better maintained under epidural plus light-enflurane anesthesia than under enflurane anesthesia alone.     

Effects of Low-flow Sevoflurane Anesthesia on Renal Function: Comparison with High-flow Sevoflurane Anesthesia and Low-flow Isoflurane Anesthesia

Background: The safety of low-flow sevoflurane anesthesia, during which CF2 = C(CF3)-O-CH2 F (compound A) is formed by sevoflurane degradation, in humans has been questioned because compound A is nephrotoxic in rats. Several reports have evaluated renal function after closed-circuit or low-flow sevoflurane anesthesia, using blood urea nitrogen (BUN) and serum creatinine as markers. However, these are not the more sensitive tests for detecting renal damage. This study assessed the effects of low-flow sevoflurane anesthesia on renal function using not only BUN and serum creatinine but also creatinine clearance and urinary excretion of kidney-specific enzymes, and it compared these values with those obtained in high-flow sevoflurane anesthesia and low-flow isoflurane anesthesia.

Methods: Forty-eight patients with gastric cancer undergoing gastrectomy were studied. Patients were randomized to receive sevoflurane anesthesia with fresh gas flow of 1 l/min (low-flow sevoflurane group; n = 16) or 6-10 l/min (high-flow sevoflurane group; n = 16) or isoflurane anesthesia with a fresh gas flow of 1 l/min (low-flow isoflurane group; n = 16). In all groups, the carrier gas was oxygen/nitrous oxide in the ratio adjusted to ensure a fractional concentration of oxygen in inspired gas (FiO2) of more than 0.3. Fresh Baralyme was used in the low-flow sevoflurane and low-flow isoflurane groups. Glass balls were used instead in the high-flow sevoflurane group, with the fresh gas flow rate adjusted to eliminate rebreathing. The compound A concentration was measured by gas chromatography. Gas samples taken from the inspiratory limb of the circle system at 1-h intervals were analyzed. Blood samples were obtained before and on days 1, 2, and 3 after anesthesia to measure BUN and serum creatinine. Twenty-four-hour urine samples were collected before anesthesia and for each 24-h period from 0 to 72 h after anesthesia to measure creatinine, N-acetyl-beta-D-glucosaminidase, and alanine aminopeptidase.

Results: The average inspired concentration of compound A was 20 +/- 7.8 ppm (mean +/- SD), and the average duration of exposure to this concentration was 6.11 +/- 1.77 h in the low-flow sevoflurane group. Postanesthesia BUN and serum creatinine concentrations decreased, creatinine clearance increased, and urinary N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase excretion increased in all groups compared with preanesthesia values, but there were no significant differences between the low-flow sevoflurane, high-flow sevoflurane, and low-flow isoflurane groups for any renal function parameter at any time after anesthesia.     

Pharmacokinetic profile of propofol after a single-dose injection during general anesthesia in Japanese adults

Purpose. To determine the pharmacokinetic parameters of propofol after a single-dose injection in Japanese adults. Methods. This study was carried out in adult patients who underwent minor surgery under general anesthesia with sevoflurane. We injected 1.0, 1.5, or 2.0 mg·kg⁻¹ of propofol at a constant rate using a syringe pump. Arterial blood samples were taken for 480 min after the administration of propofol. The whole-blood concentration of propofol was determined with gas chromatography, and a time–blood concentration curve was analyzed by a two-compartment open-model analysis and a model-independent analysis. Results. The half-lives of the central and peripheral compartment (t _1/2α and t _1/2β) were 2.26 ± 0.69 and 47.9 ± 22.1 min, respectively. The volume of the central compartment (V_c) was 0.582 ± 0.170 l·kg⁻¹, and the apparent volume of distribution at a steady state (V_dss) was 2.62 ± 1.06 l·kg⁻¹. The total body clearance (Cl) and mean residence time (MRT) were 53.7 ± 11.9 ml·min⁻¹·kg⁻¹ and 98.1 ± 16.4 min, respectively. Conclusions. Among the pharmacokinetic parameters determined in Japanese adults, t _1/2α, t _1/2β, and Vc were similar, V_dss was smaller, and Cl was larger, as compared with values in Caucasians. These findings suggest that propofol could be eliminated well during minor surgery in Japanese adults. Received: January 27, 1999 / Accepted: March 31, 2000