Kinetics and extravascular retention of acetated ringer's solution during isoflurane or propofol anesthesia for thyroid surgery

BACKGROUND: In sheep, isoflurane causes extravascular accumulation of infused crystalloid fluid. The current study evaluates whether isoflurane has a greater tendency than propofol to cause extravascular retention in surgical patients. METHODS: Thirty patients undergoing thyroid surgery lasting for 143 +/- 32 min (mean +/- SD) received an intravenous infusion of 25 ml/kg acetated Ringer's solution over 30 min. Anesthesia was randomized to consist of isoflurane or propofol supplemented by fentanyl. The distribution and elimination of the infused fluid was estimated using volume kinetics based on the fractional dilution of blood hemoglobin over 150 min. Extravascular retention of infused fluid was taken as the difference between the model-predicted elimination and the urinary excretion. The sodium and fluid balances were measured. RESULTS: The fractional plasma dilution increased gradually to approximately 30% during the infusion and thereafter remained at 15-20%. Urinary excretion averaged 11% of the infused volume. Mean arterial pressure was 10 mmHg lower in the isoflurane group (P < 0.001). The excess fluid volumes in the central and peripheral functional body fluid spaces were virtually identical in the groups. The sum of water losses by evaporation and extravascular fluid retention amounted to 2.0 +/- 2.5 ml/min for isoflurane and 2.2 +/- 2.1 ml/min for propofol. The sodium balance refuted that major fluid shifts occurred between the extracellular and intracellular spaces. CONCLUSIONS: The amount of evaporation and extravascular retention of fluid was small during thyroid surgery, irrespective of whether anesthesia was maintained by isoflurane or propofol.     

Kinetics and Extravascular Retention of Acetated Ringer's Solution during Isoflurane or Propofol Anesthesia for Thyroid Surgery

Background: In sheep, isoflurane causes extravascular accumulation of infused crystalloid fluid. The current study evaluates whether isoflurane has a greater tendency than propofol to cause extravascular retention in surgical patients.

Methods: Thirty patients undergoing thyroid surgery lasting for 143 +/- 32 min (mean +/- SD) received an intravenous infusion of 25 ml/kg acetated Ringer's solution over 30 min. Anesthesia was randomized to consist of isoflurane or propofol supplemented by fentanyl. The distribution and elimination of the infused fluid was estimated using volume kinetics based on the fractional dilution of blood hemoglobin over 150 min. Extravascular retention of infused fluid was taken as the difference between the model-predicted elimination and the urinary excretion. The sodium and fluid balances were measured.

Results: The fractional plasma dilution increased gradually to approximately 30% during the infusion and thereafter remained at 15-20%. Urinary excretion averaged 11% of the infused volume. Mean arterial pressure was 10 mmHg lower in the isoflurane group (P < 0.001). The excess fluid volumes in the central and peripheral functional body fluid spaces were virtually identical in the groups. The sum of water losses by evaporation and extravascular fluid retention amounted to 2.0 +/- 2.5 ml/min for isoflurane and 2.2 +/- 2.1 ml/min for propofol. The sodium balance refuted that major fluid shifts occurred between the extracellular and intracellular spaces.     

Elimination rate constant describing clearance of infused fluid from plasma is independent of large infusion volumes of 0.9% saline in sheep

BACKGROUND: The purpose of this study was to determine the influence of varying large crystalloid infusion volumes, ranging from a volume that has been safely administered to volunteers to a volume that greatly exceeds a practical volume for studies in normovolemic humans, of rapidly infused 0.9% saline on the elimination rate constant in sheep. METHODS: Six sheep underwent three randomly ordered, 20 min, intravenous infusions of 0.9% saline in volumes of 25 ml/kg, 50 ml/kg and 100 ml/kg. Repeated measurements of arterial plasma dilution were analyzed using the volume kinetic approach to determine the apparent volumes of the central (V1) and peripheral (V2) body fluid spaces, the elimination rate constant (kr) describing clearance from the central fluid space and the rate constant (kt) for the diffusion of fluid between the central and the peripheral fluid spaces. The latter constant was split in to two constants, one describing flow out from the central fluid space and one describing flow into the central fluid space. Urinary output was measured in all sheep. RESULTS: kr was comparable at each infused volume (38.3 +/- 4.5, 32.2 +/- 4.2, and 36.7 +/- 7.0 ml/min, respectively, in the 25 ml/kg, 50 ml/kg, and 100 ml/kg protocols). However, for the largest infusion, other kinetic parameters were influenced by the magnitude of the infusion. V2 was significantly increased (P < 0.05) and the area under the dilution-time curve divided by the infused volume was 20% lower for the largest infusion (P < 0.03). Although urinary output increased as the infusion volume increased, only 59% of the administered volume had been excreted at 180 min after the 100 ml/kg infusion as compared with approximately 90% after the other two infusions (P < 0.01). CONCLUSIONS: Elimination from the central fluid space of large, rapidly infused volumes of saline solution is independent of infused volume. Larger volumes are apparently cleared from the central fluid space (V1) by expansion of a peripheral volume (V2) as renal excretion fails to increase in proportion to the volume of infused fluid.     

Elimination Rate Constant Describing Clearance of Infused Fluid from Plasma Is Independent of Large Infusion Volumes of 0.9% Saline in Sheep

Background: The purpose of this study was to determine the influence of varying large crystalloid infusion volumes, ranging from a volume that has been safely administered to volunteers to a volume that greatly exceeds a practical volume for studies in normovolemic humans, of rapidly infused 0.9% saline on the elimination rate constant in sheep.

Methods: Six sheep underwent three randomly ordered, 20 min, intravenous infusions of 0.9% saline in volumes of 25 ml/kg, 50 ml/kg and 100 ml/kg. Repeated measurements of arterial plasma dilution were analyzed using the volume kinetic approach to determine the apparent volumes of the central (V1) and peripheral (V2) body fluid spaces, the elimination rate constant (kr) describing clearance from the central fluid space and the rate constant (kt) for the diffusion of fluid between the central and the peripheral fluid spaces. The latter constant was split in to two constants, one describing flow out from the central fluid space and one describing flow into the central fluid space. Urinary output was measured in all sheep.

Results: kr was comparable at each infused volume (38.3 +/- 4.5, 32.2 +/- 4.2, and 36.7 +/- 7.0 ml/min, respectively, in the 25 ml/kg, 50 ml/kg, and 100 ml/kg protocols). However, for the largest infusion, other kinetic parameters were influenced by the magnitude of the infusion. V2 was significantly increased (P < 0.05) and the area under the dilution-time curve divided by the infused volume was 20% lower for the largest infusion (P < 0.03). Although urinary output increased as the infusion volume increased, only 59% of the administered volume had been excreted at 180 min after the 100 ml/kg infusion as compared with approximately 90% after the other two infusions (P < 0.01).     

Volume Kinetics of Ringer Solution, Dextran 70, and Hypertonic Saline in Male Volunteers

Background: A knowledge of the distribution of different fluids given by intravenous infusion is basic to the understanding of the effects of fluid therapy. Therefore, a mathematical model was tested to analyze the volume kinetics of three types of fluids.

Methods: The authors infused 25 ml/kg of Ringer acetate solution, 5 ml/kg of 6% dextran 70 in 0.9% NaCl, and 3 ml/kg of 7.5% NaCl over 30 min in 8 male volunteers aged from 25 to 36 years (mean, 31 years) and measured the changes in total hemoglobin, serum albumin, and total blood water over time. The changes were expressed as fractioned dilution and then plotted against time. The curves were fitted to a one-volume and a two-volume model, which allowed an estimation of the size of the body fluid space expanded by the fluid (V) and the elimination rate constant (kr) to be made.

Results: The changes in blood water concentration indicated a mean size of V of 5.9 l (+/- 0.8, SEM) for Ringer's solution, 2.6 (+/- 0.3) l for dextran, and 1.2 (+/- 0.1) l for hypertonic saline. The corresponding values of kr were 94 (+/- 42), 12 (+/- 6), and 30 (+/- 4) ml/min, respectively. Blood hemoglobin indicated a degree of dilution similar to that indicated by blood water. Serum albumin indicated a more pronounced dilution, which resulted in a larger expandable volume and a greater mean square error for the curvefitting. The larger volume obtained for serum albumin can probably be explained by a loss of intravascular albumin into the tissues along with the infused fluid.     

Urinary excretion as an input variable in volume kinetic analysis of Ringer's solution

The disposition of fluid given by i.v. infusion can be studied by fitting one-volume and two-volume kinetic models to the fractioned dilution of blood haemoglobin and serum albumin concentrations over time. However, the two-volume model is sometimes associated with a high standard error in estimating the size of the secondary (peripheral) body fluid space, V2. To examine if a fixed elimination rate constant (kr) determined by urinary excretion can be used to make the model more stable, we infused Ringer's acetate 25 ml kg-1 over 30 min in 15 male volunteers (mean age 35 yr). A fixed kr increased the total residual error when curve-fitting was applied according to the one-volume model. The two-volume model was improved when there was a strong within- patient covariance between kr and V2 (r2 < or = -0.98). The size of V2 was 10 litre when the fixed and model-generated values of kr agreed fully.      

A single-model solution for volume kinetic analysis of isotonic fluid infusions

BACKGROUND: Volume kinetics was developed to analyze the distribution and elimination of intravenously given fluid. However, when groups of patients are being compared, the current approach is limited by the need for several models, which yield parameters that cannot be compared. To meet the requirement to handle all patients in a group individually and without pooling, a new all-encompassing model was designed. The aim of this paper was to test whether the new model could be used to analyze all patients in a group. METHODS: The new model consists of 'rate' and 'amount' parameters instead of 'clearance' and 'dilution' parameters. With this change, a redundant parameter can be taken out, but the biexponential nature is retained. The new parameters are the volume of distribution V1 (ml), the intercompartmental rate constant kt/min and the elimination rate constant kr/min. The success rates of the new and original models in producing results within a set of pre-determined quality requirements were compared using blood dilution data from 10 volunteers challenged with intravenous lactated Ringer's solution. RESULTS: The new model could be used to analyze all 10 cases within the pre-determined criteria, but the original biexponential model failed in 70% of cases. The residuals improved with the new model. The medians (interquartile ranges) were as follows: V1, 4931 ml (4239-6149 ml); kt), 0.0384/min (0.0024-0.1140/min); kr, 0.0140/min (0.0015-0.0043/min). CONCLUSION: The new model was suited to the analysis of all cases, and is therefore a better approach to study how clinical conditions change the distribution and elimination of infused fluid.     

Volume Kinetics of Ringer's Solution in Hypovolemic Volunteers

Background: The amount of Ringer's solution needed to restore normal blood volumes is thought to be three to five times the volume of blood lost. This therapy can be optimized by using a kinetic model that takes accounts for the rates of distribution and elimination of the infused fluid.

Methods: The authors infused 25 ml/kg Ringer's acetate solution into 10 male volunteers who were 23 to 33 yr old (mean, 28 yr) when they were normovolemic and after 450 ml and 900 ml blood had been withdrawn. One-volume and two-volume kinetic models were fitted to the dilution of the total venous hemoglobin and plasma albumin concentrations.

Results: Withdrawal of blood resulted in a progressive upward shift of the dilution-time curves of both markers. The two-volume model was statistically justified in 56 of the 60 analyzed data sets. The hemoglobin changes indicated that the body fluid space expanded by the infused fluid had a mean total volume of 10.7 l (+/- 0.9 SEM). The elimination rate constant (k (r)) decreased with the degree of hypovolemia and was 133 ml/min (22 ml/min [SEM]), 100 ml/min (39 ml/min [SEM]), and 34 ml/min (7 ml/min [SEM]), respectively (P < 0.01). Plasma albumin indicated a slightly larger body fluid space expanded by the infused fluid, but kr was less (P < 0.02). Hypovolemia reduced the systolic and diastolic blood pressures by approximately 10 mmHg (P < 0.05).     

Volume Kinetic Analysis of the Distribution of 0.9% Saline in Conscious versus Isoflurane-anesthetized Sheep

Background: The distribution and elimination of 0.9% saline given by intravenous infusion has not been compared between the conscious state and during inhalational anesthesia.

Methods: Six adult sheep received an intravenous infusion of 25 ml/kg of 0.9% saline over 20 min in the conscious state and also during isoflurane anesthesia and mechanical ventilation. The distribution and elimination of infused fluid were studied by volume kinetics based on serial analysis of hemoglobin dilution in arterial blood and by mass balance that incorporated volume calculations derived from volume kinetic analysis and measurements of urinary volumes.

Results: The mass balance calculations indicated only minor differences in the time course of plasma volume expansion between the conscious and anesthetized states. However, isoflurane anesthesia markedly reduced urinary volume (median, 9 vs. 863 ml;P < 0.03). In conscious sheep, the central and peripheral volume expansion predicted by volume kinetics agreed well with the calculations based on mass balance. However, during isoflurane anesthesia and mechanical ventilation, calculation using volume kinetic analysis of the variable kr, an elimination factor that, in conscious humans and sheep, is closely related to urinary excretion, represented both urinary excretion and peripheral accumulation of fluid. This suggests that the previous assumption that kr approximates urinary excretion of infused fluid requires modification, i.e., kr simply reflects net fluid movement out of plasma.     

Volume kinetic analysis of the distribution of 0.9% saline in conscious versus isoflurane-anesthetized sheep

BACKGROUND: The distribution and elimination of 0.9% saline given by intravenous infusion has not been compared between the conscious state and during inhalational anesthesia. METHODS: Six adult sheep received an intravenous infusion of 25 ml/kg of 0.9% saline over 20 min in the conscious state and also during isoflurane anesthesia and mechanical ventilation. The distribution and elimination of infused fluid were studied by volume kinetics based on serial analysis of hemoglobin dilution in arterial blood and by mass balance that incorporated volume calculations derived from volume kinetic analysis and measurements of urinary volumes. RESULTS: The mass balance calculations indicated only minor differences in the time course of plasma volume expansion between the conscious and anesthetized states. However, isoflurane anesthesia markedly reduced urinary volume (median, 9 vs. 863 ml; P < 0.03). In conscious sheep, the central and peripheral volume expansion predicted by volume kinetics agreed well with the calculations based on mass balance. However, during isoflurane anesthesia and mechanical ventilation, calculation using volume kinetic analysis of the variable kr, an elimination factor that, in conscious humans and sheep, is closely related to urinary excretion, represented both urinary excretion and peripheral accumulation of fluid. This suggests that the previous assumption that kr approximates urinary excretion of infused fluid requires modification, i.e., kr simply reflects net fluid movement out of plasma. CONCLUSIONS: In both conscious and anesthetized, mechanically ventilated sheep, infusion of 0.9% saline resulted in minimal expansion of plasma volume over a 3-h interval. In conscious sheep, infused 0.9% saline was rapidly eliminated from the plasma volume by urinary excretion; in contrast, the combination of isoflurane anesthesia and mechanical ventilation reduced urinary excretion and promoted peripheral accumulation of fluid.     

Stability of the interstitial matrix after crystalloid fluid loading studied by volume kinetic analysis

To investigate if fluid therapy changes the prerequisites for the development of oedema, four i.v. infusions of Ringer's solution 25 ml kg-1 were given over 15 or 30 min in a randomized crossover study to 10 healthy male volunteers, aged 28-40 (mean 31) yr. Blood haemoglobin concentration, measured every 5 min for 90 min, and urinary excretion were used as input data for volume kinetic analysis. The results showed that the elimination rate constant (kr) was higher when another infusion had been given earlier on the same day (208 vs 140 ml min-1; P < 0.002) and the size of V1 was larger during the 15-min infusions (4.7 vs 3.2 litre; P < 0.02). However, the size of V2 and the rate constant for the exchange of fluid between V1 and V2 were similar during all infusions. We conclude that a fluid challenge makes elimination of further infused fluid more effective but does not change compliance with volume expansion in healthy volunteers.      

The effect of acetate ringer solution, 6% hydroxyethyl starch saline and 20% mannitol solution on the serum concentration of propofol continuously infused

Changes in serum concentrations of propofol after administration of three different fluids were investigated in 42 scheduled surgical patients. Anesthesia was induced with propofol 2 mg.kg-1 and maintained with constant rate infusion of propofol 6 mg.kg-1.hr-1. After achieving a stable depth of anesthesia, 5 ml.kg-1 of acetate Ringer's solution, 6% hydroxyethyl starch saline solution or 20% mannitol solution was infused in 15 minutes. Blood samples each 2 ml were taken before and 0, 5, 15, 30 and 60 minutes after fluid treatment. We measured hemoglobin and hematocrit of the samples for calculating the dilution rate of the plasma with infusion treatment, and determined the serum concentration of propofol by HPLC-spectrofluorometry. After administration of each fluid, the serum concentrations of propofol decreased significantly to 17 +/- 15, 25 +/- 10 and 35 +/- 8%, respectively (mean +/- SEM). The dilution rate of the plasma from the fractional change in blood hemoglobin increased to 0.08 +/- 0.02, 0.24 +/- 0.03, and 0.36 +/- 0.03, respectively. Administration of mannitol might markedly increase distribution volume of propofol, and this can be attributed to osmotic action of mannitol and resultant expansion of extracellular fluid volume. The results of the present investigation suggest that this pharmacokinetic change decreased the concentration of propofol more significantly in mannitol treatment patients than in Ringer's solution or 6% hydroxyethyl starch saline treatment patients.     

Influence of Liberal versus Restrictive Intraoperative Fluid Administration on Elimination of a Postoperative Fluid Load

Background: Previously, the authors found "liberal" fluid administration (approximately 3 l Ringer's lactate [RL]) to improve early rehabilitation after laparoscopic cholecystectomy, suggesting functional hypovolemia to be present in patients receiving "restrictive" fluid administration (approximately 1 l RL). Because volume kinetic analysis after a volume load may distinguish between hypovolemic versus normovolemic states, the authors applied volume kinetic analysis after laparoscopic cholecystectomy to explain the difference in outcome between 3 and 1 l RL.

Methods: In a prospective, nonrandomized trial, the authors studied 20 patients undergoing laparoscopic cholecystectomy. Ten patients received 15 ml/kg RL (group 1) and 10 patients received 40 ml/kg RL (group 2) intraoperatively. All other aspects of perioperative management were standardized. A 12.5-ml/kg RL volume load was infused preoperatively and 4 h postoperatively. The distribution and elimination of the fluid load was estimated using volume kinetic analysis.

Results: Patient baseline demographics and intraoperative data did not differ between groups, except for intraoperative RL, having a median of 1,118 ml (range, 900-1,400 ml) in group 1 compared with a median of 2,960 ml (range, 2,000-3,960 ml) in group 2 (P < 0.01). There were no significant preoperative versus postoperative differences in the size of the body fluid space expanded by infused fluid (V), whereas the clearance constant kr was higher postoperatively versus preoperatively (P = 0.03). The preoperative versus postoperative changes in volume kinetics including V were not different between the two groups.     

Volume kinetics of Ringer's solution in female volunteers

The kinetics of crystalloid solutions in humans have not been adequately described previously. Therefore, we measured blood haemoglobin concentration during and for 120 min after i.v. infusion of 25 ml kg-1 of Ringer's acetate solution over 15, 30, 45 and 80 min, and 12.5 ml kg-1 over 30 min in six adult female volunteers. The dilution- time profiles were analysed according to a new kinetic model adapted for fluid spaces. Volume expansion produced by Ringer's solution approached steady state in an exponentially decaying manner when plasma volume had increased by approximately 550 ml. The size of the fluid space expanded by Ringer's solution was only 4.8 litre (95% confidence interval 3.8-5.8 litre) except for the fastest infusion, where it averaged 9.0 litre. The rate of fluid elimination could be predicted as the product of plasma dilution and a constant averaging 95 (95% confidence interval 68-122) ml min-1.      

Vascular endothelial growth factor (VEGF) in plasma increases after hip surgery

STUDY OBJECTIVE: To determine whether the plasma concentration of vascular endothelial growth factor (VEGF) is elevated after a common surgical procedure, and if any increase is followed by a reduction in the amount of infused crystalloid fluid in the blood. DESIGN: Nonrandomized study. Experimental group age-matched to control group. SETTING: Operating room of a large medical research center. PATIENTS: 10 ASA physical status I, II, and III patients, aged 51 to 94 years, scheduled for hip surgery; and 10 ASA physical status I and II volunteers, aged 53 to 71 years, comprising a control group. INTERVENTIONS: Patients and control subjects were given an intravenous volume load of Ringer's acetate solution (12.5 mL/kg for 30 min). MEASUREMENTS: The plasma concentrations of C-reactive protein, interleukin-6, interleukin-8 (inflammatory parameters used as biochemical evidence of trauma), and VEGF were measured in patients the morning after the day of the surgery. The area under the curve (AUC) for the plasma dilution was calculated in response to the intravenous fluid. MAIN RESULTS: VEGF concentration was tripled in the hip group (100.7 +/- 18.5 pg/L vs. 31.9 +/- 7.2 pg/L; p < 0.001) as a consequence of the trauma of surgery. The other inflammatory parameters were also significantly increased. There was no difference in AUC between the two groups during infusion, but after infusion AUC was significantly increased in the hip group versus controls (4.88 vs. 2.8; p = 0.025), suggesting persistence of the infused fluid to remain in the vasculature. AUC was not highly correlated with any of the inflammatory parameters regardless of group during or after infusion. CONCLUSIONS: Intravascular persistence of infused crystalloid is increased after hip surgery despite elevated VEGF levels in plasma.     

不同麻醉下老年患者静脉输注乳酸钠林格氏液的容量动力学

目的 比较不同麻醉下老年患者静脉输注乳酸钠林格氏液容量动力学的差异.方法 择期行上腹部手术老年患者30例,年龄65～79岁,ASA Ⅰ或Ⅱ级,随机分为2组(n=15):单纯全麻组(GA组)和硬膜外复合全麻组(GE组).GE组经T8.9硬膜外穿刺置管,注入2%利多卡因4 ml使阻滞平面达T4,然后硬膜外给予0.25%布比卡因8～10 ml.2组静脉注射咪达唑仑2 mg、芬太尼3μg/kg、异丙酚1.5 mg,kg和琥珀胆碱1.5 mg/kg麻醉诱导,气管内插管后行机械通气.麻醉诱导后2组经30min静脉输注乳酸钠林格氏液30 ml/kg,随后以0.1 ml·kg-1·min-1的速率继续输注60 min.连续监测心率、平均动脉压、中心静脉压、心脏指数、每搏量指数、胸内血容量指数及血管外肺水容量指数;桡动脉采血测定血红蛋白浓度和红细胞压积;记录试验过程中的尿量;应用容量动力学理论和物质守恒定律,计算中央容量稀释率、血浆容量增加、容量扩张效率、外周容量增加和清除率(K).尿量与Kr进行直线相关分析.结果 GA组和GE组乳酸钠林格氏液分布均符合容量动力学二室模型.与GA组比较,GE组中央容量稀释率、血浆容量增加和容量扩张效率升高,尿量和Kr减少(P<0.05),外周容量增加差异无统计学意义(P>0.05).GA组尿量与Kr呈正相关(r=0.551,P<0.05);GE组尿量与K呈正相关(r=0.531,P<0.05).结论 与单纯全麻比较,老年患者硬膜外复合全麻下静脉输注乳酸钠林格氏液的容量扩张效率增强.     

Influence of "liberal" versus "restrictive" intraoperative fluid administration on elimination of a postoperative fluid load

BACKGROUND: Previously, the authors found "liberal" fluid administration (approximately 3 l Ringer's lactate [RL]) to improve early rehabilitation after laparoscopic cholecystectomy, suggesting functional hypovolemia to be present in patients receiving "restrictive" fluid administration (approximately 1 l RL). Because volume kinetic analysis after a volume load may distinguish between hypovolemic versus normovolemic states, the authors applied volume kinetic analysis after laparoscopic cholecystectomy to explain the difference in outcome between 3 and 1 l RL. METHODS: In a prospective, nonrandomized trial, the authors studied 20 patients undergoing laparoscopic cholecystectomy. Ten patients received 15 ml/kg RL (group 1) and 10 patients received 40 ml/kg RL (group 2) intraoperatively. All other aspects of perioperative management were standardized. A 12.5-ml/kg RL volume load was infused preoperatively and 4 h postoperatively. The distribution and elimination of the fluid load was estimated using volume kinetic analysis. RESULTS: Patient baseline demographics and intraoperative data did not differ between groups, except for intraoperative RL, having a median of 1,118 ml (range, 900-1,400 ml) in group 1 compared with a median of 2,960 ml (range, 2,000-3,960 ml) in group 2 (P<0.01). There were no significant preoperative versus postoperative differences in the size of the body fluid space expanded by infused fluid (V), whereas the clearance constant kr was higher postoperatively versus preoperatively (P=0.03). The preoperative versus postoperative changes in volume kinetics including V were not different between the two groups. CONCLUSIONS: Elimination of an intravenous fluid load was increased after laparoscopic cholecystectomy per se but not influenced by the amount of intraoperative fluid administration.     

Oxygen-lactated Ringer's solution for surgical patients]

The effects of intravenous infusion of the lactated Ringer's solution inflated with oxygen (Oxygen-LR) and lactated Ringer's solution (LR) on oxygenation of blood were studied in 23 patients undergoing abdominal surgery under epidural anesthesia. LR 1000 ml was infused with inflated oxygen at 1L/min in 30 minutes in the oxygen-LR group (n = 12). The partial pressure of oxygen-LR was increased to 600.45 +/- 78.78 from 129.4 +/- 9.69 mmHg. LR 1000 ml was infused in 30 minutes in the control group (n = 11). There was no significant difference in PaO2, PaCO2, SatO2, A-aDO2 during and 30 minutes after infusion between the oxygen-LR and control groups. We believe that oxygen-LR is of no clinical value because of its low ability is of no carrying oxygen.     

Bolus injection of Ringer's solution and dextran 1 kDa during induction of spinal anesthesia

BACKGROUND: Arterial hypotension following induction of spinal anesthesia is difficult to prevent with infusion fluids. In a randomized, unblinded and controlled study we evaluated whether a rapid fluid administration planned according to volume kinetic analysis is followed by a more stable blood pressure. METHODS: Spinal anesthesia was induced in 75 surgical patients, using one of three different fluid regimens: intravenous 'bolus injection' of 5 ml kg(-1) of Ringer's acetate over 3 min, 2 ml kg(-1) of low-molecular weight (1 kDa) dextran over 3 min, or a constant-rate infusion of 15 ml kg(-1) of Ringer's acetate over 40 min (controls). The kinetics of the fluid was studied in five patients in each group and also in eight volunteers. RESULTS: The decrease in mean arterial pressure averaged 28%, 27% and 26%, respectively, and was fully developed 16 min after the induction. The height of the block, but not the fluid programme, correlated with the hypotension. Nausea or near-fainting associated with marked hypotension or bradycardia was recorded in none, five (20%) and two (8%) of the patients, respectively. Both bolus injections were followed by translocation of fluid from the peripheral tissues to the bloodstream, which maintained the plasma dilution at about 10% for at least 30 min until surgery began. CONCLUSION: A brisk infusion of Ringer's solution or dextran 1 kDa over 3 min was followed by the same decrease in arterial pressure as a longer and 3-5-times larger infusion of Ringer's solution over 40 min during induction of spinal anesthesia.