Global tissue oxygenation during normovolaemic haemodilution in young children

Sixteen patients (1–8 years) scheduled for major general surgery were chosen for the study. They were divided into two groups according to the replacement solution used for haemodilution (HD); whether 6% middle molecular weight hydroxyethyl starch (HES) or 6% dextran 60 (DEX). After induction of general anaesthesia and pulmonary artery catheterization, a precalculated amount of autologous blood was withdrawn while the patient's autologous blood was simultaneously replaced by either HES or DEX. Autologous blood was retransfused at a minimum haematocrit (Hct.) of 17% or at the end of surgery. The following parameters were measured and/or calculated before and after HD, every 20 min intraoperatively and hourly for 6 h postoperatively: heart rate (HR), mean arterial pressure (MAP), Cardiac index (CI), Hct., arterial and mixed venous oxygen content (CaO₂, CvO₂) and arterio-venous difference of oxygen content (avDO₂), oxygen delivery index (DO₂I), oxygen consumption index (VO₂I). The cardiovascular system remained stable. There was no significant difference as regards SvO₂, despite a significant decrease in CaO₂ to 10.8 and 10.0 ml·dl^?1 (median values) due to reduction of haemoglobin concentration in the HES and DEX groups respectively. In spite of the low hct. values during surgery DO₂I remained in normal range (median value 602 and 710 ml·min^?1·m^?2) in HEX and DEX group respectively. There was no significant change in VO₂I after haemodilution (median value 212 and 243 ml.min^?1·m^?2) in either group. No statistically significant difference was noticed between either groups regarding: CaO₂, CvO₂, DO₂I, VO₂I, and no side effects of the colloids were observed. Isovolaemic haemodilution (Hct. approx;17%) is well tolerated by young children undergoing major elective surgery; global tissue oxygenation was preserved throughout the procedure and both solutions used for haemodilution were equally effective.     

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.     

Combined nitric oxide inhalation, prone positioning and almitrine infusion improve oxygenation in severe ARDS

Purpose

To determine the efficacy and side effects of prone positioning (PP) and nitric oxide (NO) inhalation, alone, associated, or combined withiv almitrine for the treatment of hypoxaemia in severe acute respiratory distress syndrome (ARDS).

Methods

Over a period of 20 months, 27 consecutive critically ill patients with severe ARDS (Murray score > 2.5, PaO₂/FiO₂ < 170 after alveolar recruitment) were prospectively and randomly included. They inhaled NO for two hours at concentrations of 5 and 10 ppm for one hour each (H0–H2). One hour later, they were returned to the prone position for four hours (H3–H7). During the last two hours in this position (H5–H7), they were assigned to further inhalation of 10 ppm NO (Group B, n = 9) or to no further inhalation (Group A, n = 9). In group C (n = 9), the procedure for group B was combined with perfusion of 16 mg · kg^?1 · min^?1 almitrine throughout the study.

Results

Compared with control values, two hours NO inhalation improves PaO₂/FiO₂ and shunt effect by +28% and ?9%, PP by +88% and ?27%, PP + almitrine by + 132% and ?28%, NO + almitrine by + 153 and ?28%, PP + NO by +94% and ?29%, NO + PP + almitrine by +327 and ?48%. NO inhalation reduces pulmonary vascular resistance. Other haemodynamic parameters remain unchanged, whatever the treatment. NO inhalation improves PaO₂/FiO₂ by over 20% in 50% of the patients and PP is effective in 78% of the cases.

Conclusion

Prone Position improves PaO₂/FiO₂ significantly more than NO alone but less than PP+ almitrine or NO+ almitrine. The best results are obtained with the association of NO + Prone position + Almitrine.     

Ventilatory effects of laparoscopic cholecystectomy under general anesthesia

Purpose To investigate the ventilatory effect of laparoscopic cholecystectomy in patients under general anesthesia with epidural block. Methods We measured arterial blood gas, pulmonary carbon dioxide elimination (0000126;_ECO₂), the dead space/tidal volume ratio (V_D/V_T), and the alveolar-arterial PO₂ difference [(a−a)DO₂] just before and 5, 10, 20, 40, and 80 min after peritoneal insufflation in eight patients who underwent laparoscopic cholecystectomy under general anesthesia with epidural block. The effect of laparoscopic cholecystectomy on these values was evaluated. The patients were ventilated on the controlled mode by Servo 900C with a constant tidal volume (V_T 10ml·kg⁻¹) and frequency (respiratory rate 12 breaths·min⁻¹) throughout the study. Results After starting peritoneal insufflation the PaCO₂ showed a sudden increase during the initial 10 min of about 4 mmHg followed by a gradual increase thereafter. The increase in000123;_ECO₂ was about 30ml·min⁻¹ (20%) on average during the initial 20 min, and a plateau was reached within 20–40 min after peritoneal insufflation. Neither V_D/V_T nor (a−a)DO₂ showed significant changes during the study. Conclusion These results suggest that (1) transperitoneal absorption of CO₂ may be the main cause of hypercarbia, and the hypercarbia is not attributed to the increase in V_D/V_T; and (2) oxygenation is not impaired during pneumoperitoneum.     

Hypertonic saline for intraoperative fluid therapy in transurethral resection of the prostate

We tested hypertonic saline solution (HS) to determine its effectiveness in surgical procedures for prostatic hypertrophy. We randomly selected 40 patients undergoing elective transurethral resection of the prostate for either infusion of HS (3% NaCl) at 4ml·kg⁻¹·min⁻¹ (HS group) or lactated Ringer's solution (LR) at 8 ml·kg⁻¹·min⁻¹ (LR group). Anesthesiologists regulated the intraoperative infusion rate as needed to maintain blood pressure. There were no differences in systolic blood pressure, heart rate, central venous pressure, or arterial blood oxygenation between the two groups. In the HS group, plasma sodium, chloride, and osmolality, measured in the recovery room, were significantly increased; however, they returned to preanesthetic levels the day after surgery. In the LR group, in contrast, plasma sodium decreased significantly and this lower value persisted for 1 day. An osmolar gap exceeding 10mOsm·kg⁻¹ was observed in 2 patients in the HS group, but plasma sodium remained at normal values. However, in the 1 patient in the LR group whose osmolar gap exceeded 10mOsm·kg⁻¹, plasma sodium was 115 mEq·I⁻¹. HS, at a low dose, is useful in the intraoperative management of transurethral resection of the prostate.     

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.     

Continuous measurement of oxygen consumption using the reversed fick method

We developed a continuous oxygen consumption (Vo₂) measurement system employed the reversed Fick method, in which Vo₂ in computed from continuously measured sured arterial and mixed venous oxygen saturation assed by pulse oximetry and mixed venous oximetry, respectively, and cardiac output by the heat deprivation technique. This system was compared with the conventional intermittent reversed fick method in 7 patients during surgery and with indirect calorimetry in 4 intensive care unit (ICU) patients. The Vo₂ measured by the continuous reversed Fick method showed a high correlation with those simultaneously measured by the intermittent Fick method (r=0.97,P<0.01) and by indirect calorimetry (r=0.74,P<0.01). The 95% confidence limits (bias±2 SD) of the continuous reversed Fick method were −0.6±45 ml·min⁻¹ with the intermittent Fick method and −31±56 ml·min⁻¹ with indirect calorimetry. The continuous Fick method is in satisfactory agreement with the conventional methods for the measured of Vo₂ and potentially allows for convenient assessment of Vo₂ in critically ill patients. This study was supported in part by Grants-in-Aid for the Encouragement of Young Scientists 01771185 and 04857171 from the Ministry of Education, Science and Culture of Japan     

Effect of ONO-1101, a novel short-acting β-blocker on hemodynamic responses to isoflurane inhalation and tracheal intubation

Purpose We investigated the effect of a new ultrashort-acting β-blocker, ONO-1101, on hemodynamic responses to isoflurane inhalation and tracheal intubation. Methods Fifty-four ASA PS 1 or 2 patients were randomly allocated to receive either ONO-1101, 0.04 mg·kg⁻¹·min⁻¹, or saline prior to tracheal intubation. Anesthesia was induced with thiamylal, 4 mg·kg⁻¹, and vecuronium, 0.15 mg·kg⁻¹. Tracheal intubation was carried out after 3 min controlled mask ventilation with 66% N₂O and 3% inspired isoflurane in oxygen. Heart rate and blood pressure were continuously recorded from the start of induction until 5 min after intubation. Plasma concentrations of catecholamines were measured before induction, 3 min after initiating inhalation of isoflurane, and 1 min after tracheal intubation. Results Significant increases in heart rate occurred in both groups in response to isoflurane inhalation and tracheal intubation, but the magnitude of the increase was significantly less in the ONO-1101 group. Blood pressure increased after tracheal intubation in the saline group but remained unchanged in the ONO-1101 group. Plasma concentrations of norepinephrine increased after induction and intubation in both groups, with no significant difference between the groups. Conclusion ONO-1101 infusion is effective for the attenuation of hemodynamic responses to isoflurane inhalation and tracheal intubation.     

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.     

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     

Effect of low-dose infusion of prostaglandin E1 on vecuronium-induced neuromuscular blockade

The effect of low-dose (20 ng·kg⁻¹·min⁻¹) infusion of prostaglandin E₁ (PGE₁) on vecuronium-induced neuromuscular blockade was studied. The study population consisted of 24 elderly patients (65–75 years old) and 24 younger adult patients (25–56 years old). They were randomly assigned to the control and PGE₁ groups. The steady-state dose requirement (SSDR) of vecuronium was derived from ondemand infusion of the drug which produced a stable twitch height of 20% of its baseline reading, and recovery time after steady-state infusion was defined as the time for recovery from twitch height from 25% to 75%. The patients in the PGE₁ group received an infusion of PGE₁ 20 ng·kg⁻¹·min⁻¹, while those in the control group received an infusion of normal saline. The SSDR (23.2±9.1 and 34.2±5.9 μg·kg⁻¹. hr⁻¹, respectively;P=0.02) was significantly less and the recovery time (35.0±9.5 and 19.9±4.2 min, respectively;P=0.01) was significantly longer in the elderly than in the younger patients. However, low-dose infusion of PGE₁ significantly increased the SSDR (23.2±9.1 to 37.4±3.7 μg· kg⁻¹·hr⁻¹;P=0.01) and shortened the recovery time (35.0±9.5 to 23.5±4.0 min;P=0.02) in elderly patients. We concluded that low-dose infusion of PGE₁ is effective in preventing the prolonged action of vecuronium in elderly patients.     

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     

Landiolol has a less potent negative inotropic effect than esmolol in isolated rabbit hearts

Purpose  We compared the negative chronotropic and inotropic effects of landiolol and esmolol, two clinically available short-acting β1-blockers with high β1-selectivity, using whole isolated rabbit heart preparations. Methods  Tachycardia was induced by continuous perfusion of 10⁻⁷ M isoproterenol, and we used concentrations of landiolol or esmolol in ascending steps (1 · 10⁻⁶, 3 · 10⁻⁶, 1 · 10⁻⁵, 3 · 10⁻⁵, and 1 · 10⁻⁴ M). Heart rate (HR), left ventricular developed pressure (LVDP), the maximal rates of left ventricular force development (LVdP/dt_max), and myocardial oxygen consumption (MVO₂) were measured and compared. Results  Both landiolol and esmolol produced dosedependent decreases in HR, LVDP, LVdP/dt_max, and MVO₂. The HR lowering effects of the two agents were comparable. At concentrations of 3 · 10⁻⁵ and 1 · 10⁻⁴ M, esmolol produced more profound depression of LVDP (47 ± 26 and 12 ± 11 mmHg, respectively; mean ± SD) and reduction of LVdP/dt_max (650 ± 287 and 120 ± 103 mmHg·s⁻¹) than landiolol (68 ± 20 and 64 ± 20 mmHg, and 897 ± 236 and 852 ± 240 mmHg·s⁻¹, respectively). At the same concentrations, esmolol caused more profound reduction in MVO₂ (40 ± 11 and 35 ± 10 μl·min⁻¹ · g⁻¹) than landiolol (50 ± 8 and 48 ± 8 μl·min⁻¹ · g⁻¹), respectively. Conclusion  Our results indicate that in the isolated rabbit heart, landiolol and esmolol had equipotent negative chronotropic effects, however, landiolol had a less potent negative inotropic effect than esmolol.     

Significance of the Initial Arterial Lactate Level and Transpulmonary Arteriovenous Lactate Difference After Open-Heart Surgery

Purpose. This study was conducted to determine the clinical significance of the initial lactate level and its transpulmonary difference after open-heart surgery in adult patients. Methods. The initial postoperative lactate levels were obtained from both radial and pulmonary arteries (La, Lv) in 65 consecutive patients undergoing coronary (n = 46), valve (n = 8), and aortic (n = 11) surgery. We analyzed the relationships between the perioperative factors and La and transpulmonary arteriovenous lactate difference (%La-v = 100(La − Lv)/Lv). Results. La and %La-v were not correlated with the preoperative factors of age, pulmonary function, or emergency surgery. La significantly correlated with the cardiopulmonary bypass time, initial arterial pH, initial PaO₂/FiO₂, SvO₂, O₂ consumption, O₂ extraction rate, and the peak value of creatine phosphokinase. The %La-v significantly correlated with the aortic cross-clamp time, the lowest rectal temperature, the duration of intubation, and PaO₂/FiO₂ after extubation. Conclusion. La may be an indicator of the invasiveness of the surgery, while %La-v may be a predictor of postoperative pulmonary function. Both La and %La-v, as an initial value in the intensive care unit, may play an important role in planning the postoperative management of patients undergoing open-heart surgery. Received: May 4, 2001 / Accepted: September 11, 2001     

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.     

Recovery from Fontan circulation failure by application of continuous negative extrathoracic pressure

A 2-year-old girl developed lethal circulatory failure, general edema, and hepatic dysfunction in an acute phase after total cavopulmonary connection, a Fontan-type operation. Application of continuous negative extrathoracic pressure (CNEP) with a cuirass ventilator at −4 cmH₂O under spontaneous respiration dramatically improved hemodynamics, with systolic arterial pressure increasing from 82 mmHg to 90 mmHg, and central venous pressure decreasing from 15 mmHg to 13 mmHg; also, urine output increased, from 1.6 ml·kg⁻¹·h⁻¹ to 6.4 ml·kg⁻¹·h⁻¹. Improvements in hepatic function and fluid retention (reduction of pleural fluid and ascites) were also observed. The patient was successfully weaned from CNEP after 5 days. CNEP is an easily applicable, noninvasive tool to reduce pulmonary impedance, and is specifically useful to improve hemodynamics in patients after a Fontan-type operation. Our result suggests that CNEP may represent a first-line option to save patients from critical circulatory failure after a Fontan-type operation.     

Does general anesthesia with inhalation anesthetics worsen hypoxemia in patients with end-stage liver disease and an intrapulmonary shunt?

Hepatopulmonary syndrome (HPS) is common among patients with end-stage liver disease (ESLD); however, the effects of general anesthesia on oxygenation capacity have not been studied in these patients. The aim of this study was to evaluate the effects of general anesthesia with inhalation anesthetics on oxygenation parameters according to intrapulmonary shunt grade in patients undergoing liver transplantation. Fifty-eight liver transplant recipients were divided into 2 groups according to the intrapulmonary shunt grade as determined using preoperative echocardiography using the microbubble-syringe technique. Patients in the ‘no shunt’ group (n = 44) had either no detectable or a mild shunt, whereas those in the “shunt” group (n = 14) displayed moderate to severe changes. Arterial blood gas analysis was performed twice for each patient: preoperatively and 30 minutes after induction of general anesthesia. We calculated arterial oxygen partial pressure-to-FiO₂ ratio (PaO₂/FiO₂), alveolar-arterial oxygen difference (A-aDO₂), age-corrected A-aDO₂, A-aDO₂-to-inspiratory oxygen fraction ratio (AaDO₂/FiO₂), and alveolar oxygen partial pressure-to-PaO₂ ratio (PAO₂/PaO₂). In the preoperative period, the PaO₂ was lower in the shunt compared with the no shunt group (77.8 ± 24.3 vs 92.9 ± 14.5, respectively; P = .016), as was the PaO₂/FiO₂. A-aDO₂, age-corrected A-aDO₂, A-aDO₂/FiO₂, and PAO₂/PaO₂ were all greater in the shunt group preoperatively. After induction of general anesthesia, all parameters increased in both groups, but the differences between the 2 groups were no longer significant. Patients with ESLD who underwent liver transplantation with a moderate to severe intrapulmonary shunt showed lower preoperative oxygenation capacities than those without a shunt or with a mild shunt. General anesthesia decreased oxygenation capacity in all patients, but the differences between the 2 groups were no longer significant after induction.     

Evaluation of cerebrovascular carbon dioxide reactivity in patients with diabetes mellitus under sedative doses of propofol

The present study compared cerebrovascular CO₂ reactivity in diabetic patients on different treatment modalities under sedative doses of propofol. Fifteen patients with diabetes mellitus (on three different antidiabetic treatment modalities) who required mechanical ventilation during intensive care therapy were studied, sedation during mechanical ventilation being maintained using propofol. As controls, 6 patients without diabetes were monitored. A 2.5-MHz pulsed transcranial Doppler probe was attached to the head of the patient at the right temporal window for continuous measurement of mean blood flow velocity in the middle cerebral artery (Vmca). After establishing baseline values of Vmca and cardiovascular hemodynamics, end-tidal CO₂ was decreased by increasing ventilatory frequency by 5–8 breaths·min⁻¹. Values for absolute and relative CO₂ reactivity in insulintreated patients were lower than those in the other three groups (absolute CO₂ reactivity [means ± SD]: control, 3.1 ± 0.6 cm·s⁻¹·mmHg⁻¹, diet, 3.8 ± 1.4 cm·s⁻¹·mmHg⁻¹; oral antidiabetic drug 3.2 ± 0.9 cm·s⁻¹·mmHg⁻¹; insulin, 1.1 ± 0.6 cm·s⁻¹·mmHg⁻¹; P = 0.002). The present study shows that insulin-treated diabetic patients probably have lower cerebrovascular CO₂ reactivity under propofol anesthesia than control patients or diabetics treated with dietary therapy or oral hypoglycemics.     

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     

Auswirkungen von Dopexamin Transpulmonales Shuntvolumen bei thorax- chirurgischen Eingriffen mit Ein-Lungen-Beatmung

Objective: To study the influence of dopexamine on pulmonary shunt and hypoxic pulmonary vasoconstriction during major thoracic surgery with one-lung ventilation (OLV). Design: Prospective, randomised, placebo-controlled study. Setting: University hospital. Patients: Twenty adult patients undergoing elective pulmonary resection. Anaesthesia: General anaesthesia was performed using propofol, fentanyl, N₂O and vecuronium.Volume-controlled ventilation was performed to maintain normocapnia over the whole investigation period. During OLV, the tidal volume was reduced and the respiratory rate was increased to avoid a peak airway pressure exceeding 40 cm H₂O. Furthermore the FiO₂ was increased to 1,0 and the external PEEP was removed during OLV. Interventions: The patients received either dopexamine at 2 µg/kg/min (group A, n=10) or 0,9% saline as control (group B, n=10) after assessing the baseline values. Measurement and results: The following cardiorespiratory variables were recorded: Heart rate, mean arterial pressure and mean pulmonary arterial pressure. Cardiac output was measured by thermodilution using a continuous cardiac output thermodilution catheter. Arterial and mixed venous blood gas analysis were measured from simultaneously drawn samples. Cardiac index (CI), systemic vascular resistance index, pulmonary vascular resistance index, oxygen delivery index (DO₂I), oxygen consumption index and the venous admixture were calculated using standard formula. Furthermore, pressure-flow-curves were constructed to analyse flow independent changes in the pulmonary vascular resistance. Data were recorded at the following times: After induction of anaesthesia in stable haemodynamics during two-lung ventilation (baseline values, T0), intraoperatively during one-lung ventilation (T1) and postoperatively after re-establishing two-lung ventilation (T2). Patients characteristics, data from the preoperative lung function testing and surgical procedures did not differ significantly between the groups. CI increased in the dopexamine group from 2,5±1,2 l·min^?1·m^?2 (T0) to 3,6±0,9 l·min^?1·m^?2 (T1) and 4,0±1,3 l·min^?1· m^?2 (T2). The course of the intrapulmonary right-to-left shunting did not differ between the groups. In the dopexamine-treated group the DO₂I increased from 430±143 ml·min·m^?2 (T0) to 652±255 ml·min·m^?2 (T1) and 653±207 ml·min·m^?2 (T2). Regarding the pressure-flow-curves there was no difference during OLV between the two groups indicating no major blocking effect of dopexamine on hypoxic pulmonary vasoconstriction. Conclusion: It is concluded that dopexamine can be used to improve haemodynamics and oxygen delivery during thoracic surgery without increasing venous admixture during one-lung ventilation.