Lung perfusion,shunt fraction,and oxygenation during one-lung ventilation in pigs: the effects of desflurane,isoflurane, and propofol

OBJECTIVE: To study how desflurane, isoflurane, and propofol affect pulmonary perfusion, shunt fraction, and systemic oxygenation during one-lung ventilation (OLV) in vivo. DESIGN: Prospective animal study with a crossover design. SETTING: Animal laboratory of a university hospital. PARTICIPANTS: Twelve female pigs. INTERVENTIONS: The pigs were anesthetized, tracheally intubated, and mechanically ventilated. After placement of femoral arterial and thermodilution pulmonary artery catheters, a left-sided, double-lumen tube (DLT) was placed via tracheotomy. After DLT placement, F(I)O(2) was adjusted at 0.8, and anesthesia was continued in random order with 1 minimal alveolar concentration of desflurane, 1 minimal alveolar concentration of isoflurane, or propofol. MEASUREMENTS AND MAIN RESULTS: Measurements of respiratory and hemodynamic parameters were made after stabilization at each anesthetic. During OLV, perfusion of the nonventilated lung and shunt fraction were comparable during all 3 anesthetics. PaO(2) was lower during desflurane and isoflurane anesthesia as compared with propofol anesthesia. Mixed venous PO(2) and cardiac output were lower with desflurane and isoflurane as compared with propofol. CONCLUSIONS: In a clinically relevant model of OLV cardiac output, PaO(2) and mixed venous PO(2) decreased during desflurane and isoflurane as compared with propofol, whereas perfusion of the nonventilated lung and shunt fraction remained comparable.     

The cardiovascular changes associated with equipotent anaesthesia with either propofol or isoflurane

The differences in effects of anaesthetic agents on right ventricular function have not been studied. We have developed a cross–over study design to compare the effects of propofol and isoflurane on cardiac and specifically right ventricular function. Ten patients were anaesthetised with equivalent MAC of isoflurane to MIR of propofol. After measurements had been taken on the randomly assigned first agent the patients were crossed over to the other agent and measurements were repeated. Cardiac function was assessed using a pulmonary artery catheter with a fast response thermistor. There were no differences in heart rate or blood pressure between the two agents suggesting that equivalent anaesthetic doses had been given. There were significantly ( P < 0.05) higher cardiac output (4.0 to 4.5 1 min^-1), right ventricular ejection fraction (35.1 to 39.4%), stroke volume (35.4 to 39.6 ml) and right ventricular end–diastolic volume index (102 to 110 ml m^2–1) with propofol compared to isoflurane. We conclude that propofol results in improved right ventricular performance compared to isoflurane. We have also shown that anaesthetic agents can be compared using a cross–over study design, and have demonstrated that MAC of isoflurane and MIR of propofol can be directly compared. We suggest that propofol may be a more suitable agent than isoflurane for anaesthesia in patients who may already have impaired right ventricular function and in whom maintaining high cardiac output may be beneficial.     

Comparison of the effects of sub-hypnotic concentrations of propofol and halothane on the acute ventilatory response to hypoxia

To compare the effects of sub-anaesthetic concentrations of propofol and halothane on the respiratory control system, we have studied the acute ventilatory response to isocapnic hypoxia (AHVR) in 12 adults with and without three different concentrations of propofol and halothane. Target doses for propofol were 0, 0.05, 0.1 and 0.2 of the effective plasma concentration (EC50 = 8.1 micrograms ml-1). Target doses for halothane were 0, 0.05, 0.1 and 0.2 minimum alveolar concentration (MAC = 0.77%). The doses achieved experimentally were 0.01, 0.06, 0.13 and 0.26 of the EC50 for propofol and 0, 0.05, 0.11 and 0.20 MAC for halothane. During the experiment subjects breathed via a mouthpiece from an end-tidal forcing system. End-tidal PO2 (PE'O2) was held at 13.3 kPa for 5 min, and then at 6.7 kPa for 5 min. End- tidal PCO2 (PE'CO2) was held constant at 0.13-0.27 kPa greater than the subject's natural level throughout. The mean values for AHVR with propofol were: 12.8 (SEM 2.4) litre min-1 (0.01 EC50), 10.0 (1.9) litre min-1 (0.06 EC50), 9.8 (2.3) litre min-1 (0.13 EC50) and 4.9 (1.2) litre min-1 (0.26 EC50). The values for AHVR with halothane were: 11.9 (2.4) litre min-1 (0 MAC), 7.8 (1.6) litre min-1 (0.05 MAC), 5.9 (1.2) litre min-1 (0.11 MAC) and 3.2 (1.6) litre min-1 (0.2 MAC). The decline in AHVR with increasing dose for both drugs was statistically significant (ANOVA, P < 0.001); there was no significant difference between the two drugs with respect to this decline. Normoxic ventilation with propofol declined from 13.2 (1.6) litre min-1 (0.01 EC50) to 8.3 (0.9 litre min-1 (0.26 EC50), and with halothane declined from 13.5 (2.0) litre min-1 (0 MAC) to 11.8 (1.6) litre min-1 (0.2 MAC). This was significant for both drugs (ANOVA, P < 0.001).      

丙泊酚或异氟醚麻醉对单肺通气时氧化应激反应的影响

目的 观察丙泊酚或异氟醚麻醉对单肺通气(OLV)时氧化应激反应的影响.方法 48例择期行食管癌根治术患者,随机分为丙泊酚单肺通气组(Pro-OLV组)、异氟醚单肺通气组(Iso-OLV组)、丙泊酚双肺通气组(Pro-TLV组)和异氟醚双肺通气组(Iso-TLV组),每组12例.于开胸前(T0)、OLV后(TLV组于开胸后)30 min(T1)、90 min(T2)、150 min(T3)、手术结束时(T4)测定血清超氧化物歧化酶(SOD)、丙二醛(MDA)及NO浓度.结果 与T0时比较,OLV组T1～T4时的SOD活性降低,MDA浓度及NO浓度升高(P<0.01),而TLV组无明显变化.与TLV组比较,OLV组T1～T4时的SOD活性降低,MDA及NO浓度升高(P<0.01).结论 丙泊酚或异氟醚麻醉均不能减轻OLV时氧化应激反应.     

The effects of increasing concentrations of isoflurane and desflurane on pulmonary perfusion and systemic oxygenation during one-lung ventilation in pigs.

During one-lung ventilation (OLV), hypoxic pulmonary vasoconstriction (HPV) reduces venous admixture and attenuates the decrease in arterial oxygen tension by diverting blood from the nonventilated lung to the ventilated lung. In vitro, desflurane and isoflurane depress HPV in a dose-dependent manner. Accordingly, we studied the effects of increasing concentrations of desflurane and isoflurane on pulmonary perfusion, shunt fraction, and PaO(2) during OLV in vivo. Fourteen pigs (30-42 kg) were anesthetized, tracheally intubated, and mechanically ventilated. After placement of femoral arterial and thermodilution pulmonary artery catheters, a left-sided double-lumen tube (DLT) was placed via tracheotomy. After DLT placement, FIO(2) was adjusted at 0.8 and anesthesia was continued in random order with 3 concentrations (0.5, 1.0, and 1.5 minimal alveolar concentrations) of either desflurane or isoflurane. Differential lung perfusion was measured with colored microspheres. All measurements were made after stabilization at each concentration. Whereas mixed venous PO(2), mean arterial pressure, cardiac output, nonventilated lung perfusion, and shunt fraction decreased in a dose-dependent manner, PaO(2) remained unchanged with increasing concentrations of desflurane and isoflurane during OLV. In conclusion, increasing concentration of desflurane and isoflurane did not impair oxygenation during OLV in pigs. IMPLICATIONS: In an animal model of one-lung ventilation, increasing concentrations of desflurane and isoflurane dose-dependently decreased shunt fraction and perfusion of the nonventilated lung and did not impair oxygenation. The decreases in shunt fraction are likely the result of anesthetic-induced marked decreases in cardiac output and mixed venous saturation.     

Cardiovascular effects of 50% nitrous oxide in older adult patients anaesthetized with isoflurane or halothane

We have studied the cardiovascular effects of equipotent concentrations of halothane or isoflurane, with or without 50% nitrous oxide in oxygen, in 80 patients, aged 60 yr or more, during 20 min of stable equipotent anaesthesia. Non-invasive measurement techniques were used, with suprasternal Doppler ultrasonography for estimating cardiac output. Both isoflurane and halothane reduced heart rate and systemic arterial pressure. With isoflurane, mean rate decreased from 72 (SD 9.7) to 67 (10.4) beat min-1 and with halothane from 76 (10.1) to 65 (9.1) beat min-1 (P < 0.05). Mean diastolic arterial pressure decreased from 81 (11.3) to 58 (17.0) mm Hg with isoflurane and from 86 (14.7) to 70 (13.3) mm Hg with halothane (P < 0.05). Cardiac index decreased from 3.1 (1.03) to 2.7 (0.71) litre min-1 m-2 with isoflurane and from 3.1 (0.98) to 2.5 (0.57) litre min-1 m-2 with halothane (P < 0.05). Systemic vascular resistance decreased significantly in all groups except those receiving halothane with nitrous oxide. Nitrous oxide resulted in significantly less depression of cardiac index when given with isoflurane than when given with halothane. The mean percentage change in cardiac index during isoflurane anaesthesia without nitrous oxide was 16.7%; with nitrous oxide there was a 0.5% increase. Halothane, in combination with nitrous oxide, resulted in greater depression of cardiac index than isoflurane with nitrous oxide. The mean percentage change with halothane was 20.4% (22.2%); with isoflurane there was a 0.5% (27.1%) increase (P < 0.05). Hypotension was more pronounced in patients anaesthetized with isoflurane (n = 40) than those anaesthetized with halothane (n = 40), irrespective of the presence of nitrous oxide. The mean percentage decrease with isoflurane was 29.7% (21.10%) compared with 16.8% (16.78%) with halothane (P < 0.05).      

单肺通气前通气侧肺前列腺素E_1超声雾化对气体交换的影响

目的观察单肺通气(OLV)前右侧肺前列腺素E1(PGE1)超声雾化对OLV期间肺内分流率(Qs/Qt)及动脉氧合的影响。方法择期行左胸食管癌根治术患者60例,随机均分为两组:在OLV前对右侧肺雾化吸入PGE10.2μg/kg(P组)和等量生理盐水(C组)。记录雾化吸入前(T1)、OLV 10min(T2)、OLV 15 min(T3)、OLV 30 min(T4)、OLV 60 min(T5)和OLV 120 min(T6)时的氧合指数及血流动力学指标。结果两组患者PaO2在OLV开始后均呈直线下降,其中C组在T4时降至最低点;T2~T4时P组PaO2明显高于C组(P0.05),且PaO2的最低值延迟至T5时出现。T2~T4时P组Qs/Qt明显低于C组(P0.05)。两组不同时点血流动力学差异无统计学意义。结论 OLV前右侧肺雾化吸入0.2μg/kg PGE1能减少肺内分流,改善氧合。     

Comparison of the effects of sevoflurane and isoflurane on arterial oxygenation during one lung ventilation

We have compared the effects of sevoflurane and isoflurane on arterial oxygenation, heart rate and mean arterial pressure during one lung anaesthesia in a prospective, crossover study. We studied 28 patients undergoing oesophagogastrectomy, allocated alternatively to one of two groups. Patients in group I/S (n = 14) received 1 MAC (1.1%) of isoflurane in oxygen from induction until the end of 30 min of open chest one lung ventilation (OLV) in the lateral position. This was followed by 1 MAC (2.1%) of sevoflurane in oxygen for the next 30 min of OLV. Patients in group S/I (n = 14) received the two anaesthetic agents in the reverse order. We found no significant difference in arterial oxygenation, heart rate or mean arterial pressure between the two potent inhalation agents. In the subgroup of patients with pulmonary artery catheters (n = 12), we found a significant increase (P < 0.05) in derived shunt during sevoflurane anaesthesia. There was no significant difference in mixed venous saturation and cardiac output. We conclude that during one lung ventilation, the choice between sevoflurane and isoflurane did not significantly influence arterial oxygenation.      

General anesthesia with propofol and fentanyl for adult cardiac surgery

We employed propofol anesthesia with a restricted dose of fentanyl in adult cardiac surgery with the aim of early tracheal extubation and evaluated its effects on the intraoperative factors and postoperative recovery compared with those of a previous benzodiazepine-fentanyl regimen. During surgery, control group patients (n = 17) received intermittent bolus of benzodiazepines and fentanyl without restriction, whereas propofol group patients (n = 17) received continuous administration of propofol and the restricted dose of fentanyl (20 micrograms.kg-1). There were no significant differences in the times to eye opening (average 2.4 hr vs 1.6 hr, respectively, P = 0.30) and tracheal extubation (average 5.4 hr vs 4.0 hr, P = 0.25) between the groups. Both groups had similar postanesthetic circulatory status: cardiac index (average 3.6 l.min-1.m-2 vs 3.4 l.min-1.m-2, P = 0.46). The propofol group patients required smaller doses of vasodilators during cardiopulmonary bypass (average PGE1: 0.096 microgram.kg-1.min-1 vs 0.047 microgram.kg-1.min-1, P = 0.046, NTG: 0.69 microgram.kg-1.min-1 vs 0.31 microgram.kg-1.min-1, P = 0.009). It is suggested that propofol-based anesthesia could replace the previous regimen with no adverse hemodynamic effects and might have a potential to provide faster recovery and improve peripheral circulatory status in adult cardiac surgery.     

Effects of sevoflurane and propofol on pulmonary shunt fraction during one-lung ventilation for thoracic surgery

Forty patients requiring one-lung ventilation (OLV) for thoracicsurgery were randomly assigned to receive propofol (4-6 mg kg^–1h^–1) or sevoflurane (1 MAC) for maintenance of anaesthesia.Three sets of measurements were taken: (i) after 30 min of two-lungventilation (TLV), (ii) after 30 min of one-lung ventilation(OLV-1) in the supine position and (iii) during OLV in the lateralposition (OLV-2) with the chest open and before surgical manipulationof the lung. There were no differences between groups in patientcharacteristics or preoperative condition. Increases in shuntfraction during OLV-1 were 17.4% and 17.2% (P=0.94), those duringOLV-2 were 18.3% and 16.5% (P=0.59) for the propofol and sevofluranegroup, respectively. Cardiac index and other haemodynamic andrespiratory variables were similar for the two groups. We concludethat inhibition of hypoxic pulmonary vasoconstriction by sevofluranemay only account for small increases in shunt fraction and thatmuch of the overall shunt fraction during OLV has other causes. Br J Anaesth 2001; 86: 38–43     

Use of norepinephrine in the treatment of septic shock

The effects of noradrenaline were studied in 16 patients, with either a hyperkinetic septic shock syndrome or a septic shock resistant to dobutamine treatment. The study aimed to restore normal tissue perfusion pressure, assessed by a return to normal of urine output or blood pressure. An optimal left ventricular filling pressure, estimated by the pulmonary capillary wedge pressure, was obtained for each patient using a Swan-Ganz catheter. The administration of 10.6 +/- 0.5 micrograms.kg-1.min-1 dobutamine (starting dose: 6 micrograms.kg-1.min-1) was started when the cardiac index (CI) was less than 3.3 l.min-1.m-2 after vascular filling with plasma expanders. Patients became eligible for noradrenaline treatment when they fulfilled the following conditions: arterial systolic pressure (Pasys) less than or equal to 90 mmHg; systemic vascular resistances less than or equal to 600 dyn.s.cm-5; CI greater than 3.5 l.min-1.m-2; persistent oliguria (less than 30 ml.h-1). This drug was given at a constant rate with a starting dose of 0.5 micrograms.kg-1.min-1, increased every 10 min by 0.3 to 0.6 micrograms.kg-1.min-1 according to the effects on Pasys and hourly urine output. Eight patients received noradrenaline alone; the efficient dose was 0.9 +/- 0.2 micrograms.kg-1.min-1, and it was used for a mean 5.1 +/- 1 days. CI increased in those patients who were given both noradrenaline and dobutamine. Thirteen out of the 16 patients had a dramatic increase in urine output; only three patients remained oliguric. There were no effects on serum creatinine concentration, anion gap, intrapulmonary shunt and oxygen consumption.(ABSTRACT TRUNCATED AT 250 WORDS)     

Arterial Oxygenation during One-lung Ventilation: A Comparison of Enflurane and Isoflurane

Background: Because maintaining arterial oxygenation (PAO2) during one-lung ventilation (OLV) can be a clinical problem, it is useful to be aware of factors that influence PaO2 in this situation and are under the control of the anesthesiologist. It is unknown whether, among the commonly used volatile anesthetic agents, one is associated with higher PaO2 levels. Clinical studies suggest that isoflurane provides superior PaO2 during OLV than does halothane. These have not been compared to enflurane. The authors studied PaO2 and hemodynamics during OLV with 1 MAC enflurane versus 1 MAC isoflurane.

Methods: Twenty-eight adults who had prolonged periods of OLV anesthesia with minimal trauma to the nonventilated lung (thoracoscopic or esophageal surgery) were studied in a crossover design. Patients were randomized to two groups: Group 1 received 1 MAC enflurane in oxygen from induction until after the first 30 min of OLV, then were switched to 1 MAC isoflurane. In group 2, the order of the anesthetics was reversed.

Results: Isoflurane was associated with higher PaO2 values during OLV (P < 0.0001). Mean PaO2 (plus/minus SD) after 30 min OLV isoflurane was 231 (plus/minus 125) mmHg versus 184 (plus/minus 106) mmHg after 30 min OLV enflurane. The difference in Pa sub O2 between the two anesthetics was most marked in the patients with the highest PaO2 during OLV: PaO2 isoflurane - PaO2 enflurane alpha PaO2 isoflurane (r = 0.65, P < 0.001). There were no other significant differences between anesthetic gases in the measured hemodynamic or respiratory variables. In the subgroup of patients with pulmonary artery catheters (n = 7), PaO sub 2 correlated with cardiac output during OLV for both anesthetics (r = 0.81, P < 0.001).     

Comparison of breathing methods for inhalation induction of anaesthesia

We studied healthy female patients, allocated randomly to three breathing regimens for induction of anaesthesia using sevoflurane and oxygen from a co-axial Mapleson D breathing system and a mask, to test the hypothesis that rebreathing reduces the incidence of apnoea associated with loss of consciousness. The non-rebreathing group received sevoflurane in oxygen 6 litre min-1 from the start, doubling in concentration from 0.5% to 8% every 3 breaths. The second group received oxygen 6 litre min-1 for 1 min before sevoflurane was introduced, and the third group received oxygen 3 litre min-1 for 1 min before sevoflurane. The incidence and duration of apnoea were assessed using pneumotachograph and impedance pneumograph recordings, and time to induction of anaesthesia (weight drop) was measured from the time the breathing sequence was started. There was no difference in these times, which were mean 121 (95% confidence values 91-160) s, 117 (69- 201) s and 125 (76-192) s, respectively. There was a significant difference in the incidence of apnoea. No apnoea occurred during induction using oxygen 3 litre min-1. Apnoea occurred in five of 15 patients who did not receive oxygen before sevoflurane and in four of 13 who received oxygen 6 litre min-1 (P < 0.05). No patient showed a reduction in pulse oximeter saturation. We conclude that inhalation induction of anaesthesia can be performed reliably in approximately 3 min using sevoflurane in oxygen 3 litre min-1.      

The effects of shivering on oxygen consumption and carbon dioxide production in patients rewarming from hypothermic cardiopulmonary bypass

Oxygen consumption (VO2), carbon dioxide production (VCO2), end-tidal carbon dioxide partial pressure (PETCO2), mixed venous oxygen saturation (SvO2) and haemodynamic variables were recorded every 30 min for four hours in 15 patients recovering from hypothermic cardiopulmonary bypass (CPB). All patients had been anaesthetised with fentanyl 40 micrograms.kg-1, supplemented with isoflurane, and pancuronium 0.15 mg.kg-1 for muscle relaxation. Three of the 15 patients (20 per cent) shivered, defined as intermittent or continuous, vigorous movements of chest or limb muscles. Patients who shivered had a VO2 of 159 +/- 16.4 ml.min-1.m-2 on arrival in the ICU which rose to a maximum value of 254 +/- 28.3 ml.min-1.m-2 by 150 min post-CPB. In contrast, patients who did not shiver had a significantly lower VO2 of 93.1 +/- 6.9 ml.min-1.m-2 on arrival in the ICU which rose to a maximal value of only 168 +/- 11.5 ml.min-1.m-2 by 180 min post-CPB. Maximal VO2 in both groups was reached when the nasopharyngeal temperature (NPT) was approaching normal. VCO2 paralleled the increase in VO2 in both groups. By four hours there was no significant difference between the two groups; however, the VO2 in both groups (160.5 +/- 21.3 ml.min-1.m-2 and 173.9 +/- 12.3 ml.min-1.m-2 respectively) was approximately twice values commonly measured in anaesthetized patients. Patients who shivered had a significantly higher heart rate and cardiac index and significantly lower SvO2. We conclude that the high VO2 and VCO2 associated with shivering causing increased myocardial work may be detrimental to patients who have impaired cardiac function post-coronary artery surgery (CAS).     

Effects of sevoflurane compared with those of isoflurane on arterial oxygenation and hemodynamics during one-lung ventilation

Purpose. This study was designed to compare the effects of sevoflurane and isoflurane on Pao₂ and hemodynamic variables during one-lung ventilation (OLV) in surgical patients. Methods. Twelve patients undergoing an esophageal procedure with thoracotomy for which a long period of OLV was required were studied using a randomized crossover design. Group 1 received 1.2% isoflurane from the induction of anesthesia until 30 min after starting OLV, and then received 1.7% sevoflurane during the remaining period. In group 2, the order of the anesthetics was reversed. All experimental procedures were performed in the left lateral decubitus position with the chest opened. Arterial and mixed venous blood gases and cardiac outputs were analyzed immediately before OLV, during OLV, and after resumption of two-lung ventilation (TLV). Results. OLV produced lower Pao₂ and higher venous admixture (Q _s/Q _t) values than TLV. However, there was no significant difference between sevoflurane and isoflurane in Pao₂ or Q _s/Q _t during OLV. Other hemodynamic variables except for Pvˉo₂ showed no significant differences between the anesthetics. Conclusion. The effects of sevoflurane on Pao₂ and the hemodynamic variables were similar to those of isoflurane during TLV and OLV in the lateral decubitus position. Received for publication on January 29, 1999; accepted on August 6, 1999     

The effect of halothane, isoflurane, sevoflurane and propofol infusion on renal function after coronary artery bypass surgery

Renal insufficiency after cardiac surgery is associated with increased mortality, morbidity, and length of stay in the intensive care unit. We investigated the effect of isoflurane, halothane, sevoflurane and propofol anesthesia on perioperative renal function following elective coronary artery surgery. The medical records of 224 patients, in the Hacettepe University Medical Faculty Hospital who had undergone cardiac surgery in one year, were retrospectively reviewed. 65 (29%) patients received isoflurane, 68 (30%) patients received halothane, 64 (29%) patients received sevoflurane, and 27 (12%) patients received propofol infusion as part of maintenance anesthesia for coronary artery bypass surgery. Patient characteristics (age, sex, preoperative ejection fraction), operative data (duration of CPB, duration of operation, number of distal anastomoses, usage of diuretic, intraoperative crystalloid and blood transfusion), intraoperative urinary output, preoperative and postoperative (6th hours and 24th hours) BUN and plasma creatinine levels, were not statistically significant between and within groups. Intraoperative inotropic agent (dopamine) was used in 8 (12.3%) patients in the isoflurane group, in 10 (14.7%) patients in the halothane group, in 11 (17.2%) patients in sevoflurane group and in 9 (33.3%) patients in the propofol group. Postoperatively fluid and blood transfusion, postoperative drainage, urinary output, diuretic usage were smiliar between the four groups (p>0,05). Inotropic agent was used in 8 (12.3%) patients in the isoflurane group, in 9 (13.2%) patients in the halothane group, in 16 (25%) patients in the sevoflurane group and in 7 (25.9%) patients in the propofol group. It is concluded that, halothane, isoflurane, sevoflurane and propofol infusion anesthesia as part of anesthesia maintenance for elective coronary artery bypass surgery does not affect early postoperative renal functions.     

Effects of isoflurane on oxygenation during one-lung ventilation in pulmonary emphysema patients

Background: Hypoxic pulmonary vasoconstriction has an important role in human one-lung ventilation (OLV) in the lateral decubitus position under general anesthesia. During OLV, inhalational anesthesia may inhibit hypoxic pulmonary vasoconstriction and the decrease in arterial oxygenation. We studied the effect of isoflurane administration on arterial oxygen tension in chronic obstructive pulmonary disease patients.
Methods: Ten patients who had thoracoscopic laser ablation of bullous emphysema were studied. Patients received 2% isoflurane in oxygen from induction until the first 20 min of OLV in the lateral decubitus position, then were switched to 1% isoflurane lasting 20 min and next were switched to 0.5% isoflurane lasting 20 min. After each 20-min inhalation, pulmonary and hemodynamic parameters were measured. The given concentrations for isoflurane were merely vapor meter concentrations.
Results: PaO₂/FIO₂, Qs/Qt respiratory rate peak inspiratory pressure and PaCO₂ showed no significant changes at each point of isoflurane. Expiratory tidal volume significantly decreased (P<0.05) with 0.5% isoflurane compared to that with 2% isoflurane. Cardiac output, mean arterial pressure, mean pulmonary arterial pressure, systemic vascular resistance and pulmonary vascular resistance showed no significant changes at each point of isoflurane.
Conclusions: In patients with pulmonary emphysema, arterial oxygenation is not affected by low isoflurane concentration during OLV in the lateral decubitus position.     

Early and late recovery after major abdominal surgery. Comparison between propofol anaesthesia with and without nitrous oxide and isoflurane anaesthesia

A comparison was made between early and late recovery after major abdominal surgery under intravenous anaesthesia with propofol (with and without nitrous oxide) or inhalational anaesthesia with isoflurane. Sixty patients were randomly allocated to one of three forms of anaesthesia: propofol, propofol/nitrous oxide, or isoflurane/nitrous oxide anaesthesia. All received fentanyl and vecuronium. Recovery was monitored during the first 2 h after extubation and on days 1, 2, 3, 7 and 30 after surgery. Every 30 min during the first 2 postoperative hours, the Steward recovery scale, sedation, orientation, collaboration, and comprehension were assessed by a blinded observer. Psychomotor function was evaluated by computerised simple reaction time and finger tapping speed in 32 patients. A scale of symptoms and mood check list were filled in by 35 patients on days 1, 2, 3, 7 and 30. The preoperative values for all tests were collected 1–4 days before surgery. The time between end of surgery and extubation was longer in the propofol group, but early and late recovery of psychomotor function were similar in the three groups. Patients anaethetised with isoflurane reported more vegetative symptoms than those who received propofol (P < 0.03). The addition of nitrous oxide to propofol did not change the reported degree of symptoms. The difference in vegetative symptoms between groups was most obvious on day 7. Patients anaesthetised with propofol reported better subjective control (P < 0.02) and were more socially oriented (P < 0.05) than patients anaesthetised with isoflurane. We conclude that early recovery was similar in the three groups. Patients anaesthetised with propofol reported fewer late symptoms and better mood after operation than those anaesthetised with isoflurane. The addition of nitrous oxide did not affect the results.     

The effects of increasing concentrations of desflurane on systemic oxygenation during one-lung ventilation in pigs.

During one-lung ventilation (OLV), hypoxic pulmonary vasoconstriction reduces venous admixture and attenuates the decrease in arterial O2 tension by diverting blood from the nonventilated to the ventilated lung. In vitro, increasing concentrations of desflurane depresses hypoxic pulmonary vasoconstriction in a dose-dependent manner. Accordingly, we investigated the effects of increasing concentrations of desflurane on oxygenation during OLV in vivo. Thirteen pigs (25-30 kg) were anesthetized (induction: propofol 2-3 mg/kg IV; maintenance: N2O/O2 50%/50%, desflurane 3%, propofol 50 microg x kg(-1) min(-1), and vecuronium 0.2 mg x kg(-1) x h(-1) IV), orotracheally intubated, and mechanically ventilated. After placement of femoral arterial and thermodilution pulmonary artery catheters, a leftsided, 28F, double-lumen tube was placed via tracheotomy. After double-lumen tube placement, N2O and desflurane were discontinued, propofol was increased to 200 microg x kg(-1) x min(-1), and the fraction of inspired oxygen was adjusted at 0.8. Anesthesia was then continued in random order with desflurane 5%, 10%, or 15% end-tidal concentrations while propofol was discontinued. Whereas mixed venous PO2, mean arterial pressure, cardiac output, and shunt fraction decreased in a dose-dependent manner, PaO2 remained unchanged with increasing concentrations of desflurane during OLV. These findings indicate that, in vivo, increasing concentrations of desflurane do not necessarily worsen oxygenation during OLV. IMPLICATIONS: Oxygenation during one-lung ventilation depends on reflex vasoconstriction in the nonventilated lung. In vitro, desflurane inhibits this reflex dose-dependently. Our results indicate that, in vivo, this does not necessarily translate to dose-dependent decreases in oxygenation during one-lung ventilation.     

Arterial oxygenation during one-lung ventilation: combined versus general anesthesia

The optimal anesthetic management of patients undergoing thoracotomy for pulmonary resection has not been definitely determined. We evaluated whether general i.v. anesthesia (propofol-fentanyl) provides superior PaO2 during one-lung ventilation (OLV) compared with thoracic epidural anesthesia (TEA) with supplemental local and general anesthetics. We studied 60 patients who had prolonged periods of OLV for elective thoracic surgery for lung cancer and who were prospectively randomized into two groups. In 30 patients (GA group), fentanyl/propofol/rocuronium anesthesia was used. Another 30 patients (TEA group) were anesthetized with propofol/rocuronium/epidural thoracic bupivacaine 0.5%. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during the entire study. Arterial and venous blood gases were recorded before surgery in a lateral position with two-lung ventilation, 15 and 30 min after OLV (OLV + 15 and OLV + 30, respectively) in all patients. We measured PaO2, venous central oxygen tension, arterial and central venous oxygen saturation, venous admixture percentage (Qs/Qt%), and arterial and central venous oxygen content. The mean values for PaO2 during OLV in the GA group after 15 min (175 mm Hg) and 30 min (182 mm Hg) were significantly (P < 0.05) higher compared with the TEA group (120 and 118 mm Hg, respectively). Furthermore, Qs/Qt% was significantly (P < 0.05) increased in the TEA group during OLV. There were no other significant differences. We conclude that using the TEA regimen is associated with a lower PaO2 and a larger intrapulmonary shunt during OLV than with total i.v. anesthesia alone. IMPLICATIONS: Sixty patients undergoing elective lung surgery during a prolonged period of intraoperative one-lung ventilation were studied and randomized to receive general i.v. anesthesia or general i.v. anesthesia combined with thoracic epidural anesthesia. The arterial oxygenation in the first group was better than that in the second group during one-lung ventilation.