Skeletal muscle oxygen pressure fields during controlled hypotension with adenosine and sodium nitroprusside A comparative study in the rabbit

The MDO (Mehrdraht Dortmund Oberfläche) multiwire oxygen electrode was used for studies of oxygen pressure fields in eight rabbit skeletal muscle preparations during controlled hypotension with adenosine and sodium nitroprusside (SNP). Tissue oxygen histograms were constructed from 120 simple tissue oxygen pressures (P_tO₂) samples that were collected during 5 min. Statistical analysis between histograms was performed with the two-sample Kolmogorov-Smirnov test. Mean arterial blood pressure was reduced to 60 mmHg with both drugs, corresponding to a 42–43% reduction during the 25-min hypotension period. SNP-induced hypotension caused significant reduction of muscle oxygenization (compared to normotensive controls) in six of the animals, while this occurred on three occasions during adenosine administration. When comparing the histograms during hypotension, the tissue oxygenation during adenosine infusion was higher than during SNP in five and equal to SNP in three animals. Low tissue oxygen pressure values (0-0.6 kPa) were four times more frequent during SNP than during adenosine hypotension, although systemic arterial oxygen pressures were unaffected. We conclude that controlled hypotension with adenosine preserves tissue oxygen pressures better than hypotension induced by SNP.     

瑞芬太尼复合异氟烷控制性降压对神经外科手术患者肾素-血管紧张素-醛固酮系统的影响

目的观察瑞芬太尼复合异氟烷在神经外科手术中行控制性降压的效果,比较瑞芬太尼和硝普钠对患者肾素-血管紧张素-醛固酮系统（RAAS）的影响。方法择期行控制性降压的手术患者40例,ASA Ⅰ～Ⅱ级,气管插管后,控制呼气末异氟烷浓度为1．2％±0．2％。按降压方法将患者随机分为两组,每组20例,均使平均动脉压（MAP）降低至基础值的60％～70％（目标血压）。Ⅰ组：从1．0μg·kg^-1·min^-1的速度开始给予硝普钠,每隔30s增加0．5μg·kg^-1·min^-1直至血压达到目标血压。Ⅱ组：从（0．15～0．2）μg·kg^-1·min^-1的速度开始给予瑞芬太尼,每隔30s增加0．05μg·kg^-1·min^-1直至达到目标血压。在麻醉前（T0）、控制性降压前（T1）、控制性降压后5min（T2）、控制性降压后30min（T3）及控制性降压结束后20min（T4）记录MAP、HR、CVP,同时测定血中肾素、血管紧张素Ⅱ、醛固酮含量。由术者在不知道控制性降压方式的情况下评估术野质量。结果Ⅰ组T2～4的HR较T0和T1增加;Ⅱ组T2～4的HR较T0和T1减慢,也较Ⅰ组T2-4的HR慢;Ⅰ组T4的MAP、CVP较T1高,也高于Ⅱ组T4的MAP、CVP（P〈0．05或0．01）。Ⅰ组T2～4肾素、血管紧张素Ⅱ、醛固酮含量高于T0和T1,也高于Ⅱ组相应时点三种激素的含量（P〈0．05）。而Ⅱ组三种激素的含量在T0～4未见明显变化（P〉0．05）。Ⅱ组的出血量较Ⅰ组少,6点刻度表和VAS评分均低于Ⅰ组（P〈0．05）。结论与硝普钠相比,瑞芬太尼复合异氟烷控制性降压降压过程平稳,为手术提供更清晰的术野,并在控制性降压期间抑制RAAS。     

Myocardial effects of adenosine- and sodium nitroprusside-induced hypotension: a comparative study in patients anaesthetized for abdominal aortic aneurysm surgery

The effects of adenosine and sodium-nitroprusside (SNP) on central and myocardial haemodynamics and metabolism were evaluated during fentanyl anaesthesia (100 micrograms.kg-1) in six patients with peripheral vascular disease. The investigation was performed during stable anaesthesia, before scheduled abdominal aortic graft surgery. Adenosine and SNP were infused intravenously in random order over 20 min, leaving a 30-min control period in between. The vasodilators were titrated in order to reduce mean arterial pressure by approximately 25%. Adenosine (90 +/- 20 micrograms.kg-1.min-1) reduced mean arterial pressure from 10.9 +/- 0.3 to 8.4 +/- 0.4 kPa (82 +/- 3 to 63 +/- 3 mmHg), and SNP (0.7 +/- 0.1 micrograms.kg-1.min-1) from 11.0 +/- 0.2 to 8.4 +/- 0.3 kPa (83 +/- 3 mmHg to 63 +/- 3 mmHg), during the hypotension period. Cardiac index remained unaffected during induced hypotension with both vasodilators, while heart rate increased during SNP infusion (8 +/- 3%) and remained unaffected with adenosine. Left ventricular stroke work index and myocardial oxygen consumption decreased during SNP infusion (33 +/- 3% and 17 +/- 5%, respectively), while these parameters were unchanged with adenosine. Adenosine hypotension increased coronary sinus flow 1-2 fold (128 +/- 26%), together with increased coronary sinus oxygen content (96 +/- 11%). In contrast, coronary sinus flow decreased during SNP hypotension (-15 +/- 4%) with unaffected coronary sinus oxygen content. It is concluded that adenosine, in contrast to SNP, is associated with a hyperkinetic myocardial circulation.     

Glyburide decreases myocardial oxygen pressure in dogs

BACKGROUND: Reports show that glyburide, an adenosine triphosphate sensitive potassium (K+ATP) channel blocker, will reverse the myocardial protective effect of inhalational anesthesia. We evaluated the effect of glyburide on myocardial tissue oxygen pressure (PmO2) in dogs anesthetized with desflurane. METHODS: Twelve dogs were anesthetized with 8% end-tidal desflurane for baseline anesthesia. A flow probe was placed on the left anterior descending (LAD) artery. A probe that measured PmO2 was inserted into the middle myocardium in the LAD region. After baseline measures, six dogs received i.v. 1 mg kg(-1) of glyburide and six dogs received sham vehicle treatment. After the glyburide or sham treatment, each dog received an i.v. infusion of adenosine 0.1 microg kg(-1) x min(-1), sodium nitroprusside (SNP) 2-4 microg kg(-1) x min(-1) and 14% end-tidal desflurane in random order. RESULTS: Glyburide decreased LAD artery flow from 59 +/- 9 ml min(-1) to 30 +/- 6 ml min(-1) (P < 0.05) and PmO2 from 44 +/- 16 mmHg to 30 +/- 9 mmHg (P < 0.05). Adenosine infusion increased LAD artery blood flow 180% in the sham-treated dogs but produced no change in the glyburide-treated dogs. Sodium nitroprusside infusion increased LAD artery flow and decreased PmO2 in both the glyburide- and sham-treated dogs. Desflurane (14%) did not reverse the glyburide-induced vasoconstriction but increased PmO2 to 38 +/- 20 mmHg (P < 0.05). CONCLUSION: Glyburide produced myocardial tissue hypoxia, which was not changed by adenosine, worsened by SNP and improved by 14% desflurane. The improvement in PmO2 with desflurane occurred without a change in myocardial blood flow.     

Comparison of adenosine,isoflurane, and desflurane on myocardial tissue oxygen pressure during coronary artery constriction in dogs

OBJECTIVE: To compare adenosine-, isoflurane-, or desflurane-induced hypotension with and without left anterior descending (LAD) coronary artery constriction for the effects on myocardial tissue oxygen pressure (PmO(2)) in dogs. DESIGN: Prospective, randomized, nonblinded. SETTING: University teaching hospital. PARTICIPANTS: Male nonpurpose-bred dogs (n = 18). INTERVENTIONS: Dogs were anesthetized with 1.5% isoflurane (n = 12) or 8% desflurane (n = 6). A flow probe and balloon occluder were placed on the LAD artery. A probe that measured myocardial oxygen pressure was inserted into the middle myocardium in the LAD region. Myocardial oxygen consumption (MVO(2)) was calculated as LAD flow x arterial minus coronary sinus oxygen content. MEASURES AND MAIN RESULTS: Measures were made during hypotension produced by adenosine infusion, 2.8% isoflurane, or 14% desflurane with and without LAD constriction to decrease blood flow 30%. Without LAD artery constriction, adenosine infusion increased LAD flow 90% and MVO(2) 70%, 2.8% isoflurane produced no change in MVO(2), and 14% desflurane decreased MVO(2) 25%, but no treatment changed PmO(2). LAD artery constriction decreased PmO(2) 50% by itself. Adenosine infusion during LAD constriction decreased tissue oxygen pressure an additional 60%, 2.8% isoflurane produced no change, and 14% desflurane increased PmO(2) 100%. CONCLUSION: There was an inverse relationship between the effect of adenosine, 2.8% isoflurane, and 14% desflurane on MVO(2) and PmO(2) during ischemia. This is consistent with reports that increasing oxygen demand worsens myocardial ischemia.     

硝普钠控制性降压对血液动力学及脑氧平衡的影响

目的 研究硝普钠控制性降压对颅内手术病人血液动力学及脑氧供需平衡的影响。方法 择期颅内手术病人12例，用硝普钠使平均动脉压(MAP)降至50～65mmHg，并维持30min。降压前后，自桡动脉和颈内静脉球部取血进行血气分析和血糖测定，并以CO2复吸人法无创心排血量监舅仪(NiCO2)连续监测心排血量(CO)。结果 (1)降压期间，HR明显加快，CO先下降后又回升至降压前水平;颈静脉血氧饱和度无明显下降；(2)动-颈内静脉球部氧含量差、脑氧摄取率、动-颈内静脉糖含量差和脑葡萄糖摄率麻醉后均显著下降，降压及停降压后均进一步下降，仅脑氧摄取率降压后稍增加。结论 硝普钠控制性降压时心率增快，CO无明显变化，脑氧供需可维持平衡，但对葡萄糖的利用减少。     

Continuous monitoring of oxygen tension with a transcutaneous sensor during hypotensive anesthesia

Transcutaneous oxygen tension (TCPO2) is a useful noninvasive technique for monitoring arterial oxygen tension under stable circulatory conditions. This study was undertaken to determine if TCPO2 is also reliable during sodium nitroprusside-induced hypotension under general anesthesia. Arterial blood gases and TCPO2 were measured prior to inducing hypotension (baseline), at 20-min intervals during hypotension, and when systemic arterial pressure had returned to within 10% of the control (pre-hypotension) value. With induced hypotension, PaO2 and TCPO2 decreased significantly (P less than 0.05), and were well correlated by linear regression (r greater than 0.85); however, regressions were strongly dependent on the individual patient. The mean regression line for all patients as a group was given by TCPO2 = 0.69 PaO2 + 20.7 mmHg (r = 0.93, P less than 0.01); significantly different regressions were obtained for each patient (P less than 0.0001). Comparing changes in TCPO2 versus those in PaO2 (relative change from baseline values) did not substantially reduce the variability among patients. It is concluded that TCPO2 reliably reflects changes in arterial oxygen tension during controlled hypotension under general anesthesia, but that a separate calibration of TCPO2 vs. PaO2, obtained prior to inducing hypotension, may be required for each individual patient.     

Effects on skeletal muscle oxygenation and capillary blood flow by adenosine-, sodium nitroprusside- and acetylcholine-induced hypotension

Background: Adenosine (ADO)-induced hypotension during diethyl ether anesthesia has been shown to increase skeletal muscle oxygenation. Whether this beneficial effect of ADO hypotension is present also during another anesthetic technique was tested in the present study using ketamine-xylazine anesthesia, and its actions were compared with sodium nitroprusside (SNP) and acetylcholine (ACh) induced hypotension in rabbits.
Methods: Local oxygen pressure and capillary blood flow were measured with a multiwire microelectrode which was placed on the surface of the left vastus medialis muscle. The experiments were performed in three groups, in which either ADO, SNP or ACh was infused into a central vein in a dose that produced a reduction of the mean arterial pressure by 20–25%, to approximately 60 mmHg.
Results: In the ADO group (60–170 μg kg^-1 min^-1) the tissue oxygen pressures increased by 23% while capillary blood flow decreased by 38%. During SNP administration (1–3 μg kg^-1 min^-1) the oxygen pressures decreased by 21% and an increase of 31% in capillary flows was seen. When ACh was infused (1–4 μg kg^-1 min^-1) the oxygen pressures decreased by 21% and, in parallel, capillary blood flow decreased by 50%. During hypotension no low tissue oxygen pressure values (<1.5 kPa) were found in the ADO group, whereas they were present in both the SNP and ACh group.
Conclusion: Compared to sodium nitroprusside and acetylcholine, adenosine appears to have an oxygen-sparing effect in the skeletal muscle during pharmacologically induced hypotension.     

Defining the impaction frequency and threshold force required for femoral impaction grafting in revision hip arthroplasty

Background and purpose The two most common complications of femoral impaction bone grafting are femoral fracture and massive implant subsidence. We investigated fracture forces and implant subsidence rates in embalmed human femurs undergoing impaction grafting. The study consisted of two arms, the first examining the force at which femoral fracture occurs in the embalmed human femur, and the second examining whether significant graft implant/subsidence occurs following impaction at a set force at two different impaction frequencies.

Methods Using a standardized impaction grafting technique with modifications, an initial group of 17 femurs underwent complete destructive impaction testing, allowing sequentially increased, controlled impaction forces to be applied until femoral fracture occurred. A second group of 8 femurs underwent impaction bone grafting at constant force, at an impaction frequency of 1 Hz or 10 Hz. An Exeter stem was cemented into the neomedullary canals. These constructs underwent subsidence testing simulating the first 2 months of postoperative weight bearing.

Results No femurs fractured below an impaction force of 0.5 kN. 15/17 of the femurs fractured at or above 1.6 kN of applied force. In the second group of 8 femurs, all of which underwent femoral impaction grafting at 1.6 kN, there was no correlation between implant subsidence and frequency of impaction. Average subsidence was 3.2 (1–9) mm.

Interpretation It is possible to calculate a force below which no fracture occurs in the embalmed human femur undergoing impaction grafting. Higher impaction frequency at constant force did not reduce rates of implant subsidence in this experiment.     

尼卡地平、硝普钠用于控制性降压对鼻内镜手术脑氧代谢的影响

目的比较鼻内镜手术中应用尼卡地平、硝普钠行控制性降压对脑氧代谢的影响。方法选择鼻息肉行内镜手术者30例,随机分为两组,分别采用尼卡地平(A组,n=15)和硝普钠(B组,n=15)行控制性降压。于不同时段降压前(T0)、降压后10 min(T1)、降压后30 min(T2)及停止降压后10 min(T3)行动静脉血气分析。结果①T1、T2时,B组HR明显快于T0时,且在此两时点HR明显快于A组(P<0.05)。②A组D(a-jv)O2、CERO2在T1、T2时较T0时明显下降,且在此两时点上明显低于B组(P<0.05)。结论尼卡地平、硝普钠均可安全用于鼻内镜手术中的控制性降压,都能降低脑氧代谢,但在降低脑氧代谢、改善脑氧合方面,尼卡地平优于硝普钠,有较好的脑保护作用。     

Spinal anesthesia attenuates myocardial ischemia during coronary artery spasm induced by intraaortic methacholine in rats

Coronary artery spasm is not rare in patients with coronary artery disease, but the influence of regional anesthesia on spasm-induced myocardial ischemia is not known. We investigated the effects of spinal anesthesia on myocardial ischemia during coronary artery spasm in rats, and compared these with the effects of an alpha- and beta-adrenergic antagonist, and an alpha-adrenergic agonist.
An intraaortic catheter was inserted via the right internal carotid artery so that the tip of the catheter was placed near the coronary ostium. An intrathecal catheter was placed at lumbar level. Coronary spasm was induced by the intraaortic injection of methacholine, and we identified the thresholds of myocardial ischemia, defined as the dose of methacholine that induced ST-segment elevation. Subsequently, the thresholds were determined after spinal anesthesia, and after the intraaortic injection of phentolamine and propranolol.
The thresholds of myocardial ischemia increased significantly after intrathecal bupivacaine. In contrast, the threshold did not change after the injection of phentolamine. The thresholds increased significantly after the injection of propranolol. Methoxamine significantly decreased the threshold of ischemia.
These results demonstrated that spinal anesthesia attenuated myocardial ischemia during methacholine-induced coronary spasm. This effect was equivalent to that of propranolol.     

右美托咪啶在全麻鼻内镜手术控制性低血压中的应用

目的 探讨右美托咪啶在全麻鼻内镜手术控制性低血压中应用的安全性及有效性.方法 对60例择期全麻下行鼻内镜手术患者按随机数字表法随机分为两组(每组30例),采用硝普钠(N组)、右美托咪啶(D组)行控制性低血压,维持平均动脉压( MAP)在60 mm Hg～70 mm Hg(1 mm Hg=0.133 kPa).记录诱导前5min(T0)、手术开始后30 min(T1及拔管即刻(T2)时的心率(HR)、MAP及达标时间、手术时间、降压持续时间、拔管时间、出血量及尿量,对术野质量和苏醒期清醒镇静程度进行平定并观察有无副作用.结果 两 组患者年龄、体重、性别比、手术时间、控制降压持续时间组间比较,差异无统计学意义(P＞0.05).所有患者术中MAP均能维持在目标范围.两组患者T0时点MAP、HR组间比较,差异无统计学意义(P ＞.05);降压达标时间D组(16.7±3.7) min较N组(10.1±1.8) min慢(P＜0.05);T2、T1时点与T0时点比较,N组HR(105+7)、(82±5)次/min较(78±6)次/min明显增快(P＜0.05),D组HR(74±7)、(69±8)次/min较(79±8)次/min明显减慢(P＜0.05);组间比较,T2、T1时点N组HR(105±7)、(82±5)次/min明显高于D组(74±7) 、(69±8)J/min(P＜0.05).N组拔管时出现反跳性高血压,D组拔管时MAP(84+10) mm Hg仍低于诱导前水平(95±8) mm Hg(P＜0.05).D组术野质量评定(scores of surgical field quality,SSFQ)(1.2±0.4)分优于N组的(1.9±0.5)分(P＜0.05);N组的拔管时间(14.5±1.8) min要短于D组的(16.5±2.7)min(P＜0.05);N组苏醒期清醒镇静评分(1.5±A5)分优于D组的(2.0±0.3)分(P＜0.05),但N组有6例出现术后躁动;D组出血量(111±45) ml较N组的(191±43)ml少(P＜0.05),D组尿量(390±105) ml较N组的(230±83) ml多(P＜0.05).所有患者术后随访无术中知晓、呼吸抑制等麻醉并发症发生.结论在全麻鼻内镜手术中应用右美托咪啶行控制性低血压安全可行,能提供更好的术野质量,同时副作用更少,值得推广应用.     

Changes in jugular bulb oxygen saturation during off-pump coronary artery bypass graft surgery

BACKGROUND: The effect of haemodynamic derangement during coronary artery anastomosis in off-pump coronary artery bypass surgery on cerebral blood flow has not been elucidated. Jugular bulb oxygen saturation is a useful indicator of cerebral blood flow provided that the cerebral metabolic rate is constant. This study was designed to evaluate the changes in jugular bulb oxygen saturation during off-pump coronary artery bypass surgery. METHODS: With IRB approval, 48 patients were included. After anaesthesia, an 18-G catheter was introduced into the jugular bulb. Haemodynamic variables and oxygen profiles from gas analysis of jugular bulb blood and arterial blood were obtained: after sternotomy (baseline); at 5 min after the beginning of the anastomosis of the left anterior descending artery, obtuse marginal artery, and right coronary artery; and after sternal closure. RESULTS: Cardiac index and mixed venous oxygen saturation decreased significantly during anastomosis of all three arteries compared to the baseline value. Although the changes in jugular bulb oxygen saturation during anastomosis were statistically significant compared to its baseline value, jugular bulb oxygen saturation remained within normal limit throughout the study. CONCLUSIONS: Jugular bulb oxygen saturation, which represents the global cerebral oxygenation, was well maintained during the anastomosis of all coronary arteries despite significant haemodynamic changes during off-pump coronary artery bypass (OPCAB).     

Acute phase response to nitroprusside-induced controlled hypotension in patients undergoing radical prostatectomy

This study evaluated the effects of sodium nitroprusside-induced controlled hypotension on the acute phase response in patients undergoing radical prostatectomy. Thirty patients were randomly allocated to two groups, a hypotension group (mean arterial blood pressure was adjusted to 50 mmHg) and a control group (mean arterial blood pressure > 70 mmHg). C-reactive protein increased significantly in the hypotension group from 0.13 (0.23) to 9.85 (2.84) microg x ml-1 and in the control group from 0.15 (0.27) to 7.38 (3.02) microg x ml-1. In both groups, serum amyloid A increased significantly, but levels were higher in the hypotension group [585 (125) microg x l-1] than in the control group [460 (187) microg x l-1]. Interleukin-6 increased significantly in both groups, but was higher in the hypotension group [139 (124) pg x ml-1] than the control group [56 (27) pg x ml-1]. Elastase showed no significant changes in the control group but in the hypotension group there was a significant increase from 65 (51) to 122 (75) ng x ml-1. Sodium nitroprusside-induced hypotension was associated with a more pronounced acute phase reaction.     

Fenoldopam for controlled hypotension during spinal fusion in children and adolescents

Fenoldopam is a dopamine1 agonist whose pharmacological effects include vasodilation of the vascular beds of the kidney, mesentery, skeletal muscle, and coronary systems, resulting in a decrease in systemic vascular resistance and mean arterial pressure. The current retrospective review outlines the use of fenoldopam for controlled hypotension during anterior or posterior spinal fusion in 10 children and adolescents, aged 8-14 years and weighing 22-61 kg. Fenoldopam was infused at a starting dose of 0.3-0.5 microg.kg-1. min-1 and increased incrementally to achieve a mean arterial pressure (MAP) of 50-65 mmHg. The desired MAP was achieved in 4-11 min (7+/-2.5 min). The fenoldopam infusion was administered for 135-225 min (160+/-25 min) in doses ranging from 0.2 to 2.5 microg. kg-1.min-1. The mean fenoldopam infusion rate for the 10 cases varied from 0.5 to 1.4 microg.kg-1.min-1 (1.0+/-0.3 microg.kg-1. min-1). No excessive hypotension or clinically significant adverse effects were noted. Statistically significant, but clinically insignificant, increases in heart rate and decreases in PaO2 were noted during the fenoldopam infusion. The baseline heart rate increased from 87+/-13 b.min-1 to a maximum of 114+/-16 b.min-1 (P < 0.0001) during the fenoldopam infusion. In the six patients undergoing posterior spinal fusion, the baseline PaO2 decreased from 232+/-7 mmHg to a low of 199+/-11 mmHg (P=0.0004) during the fenoldopam infusion. Fenoldopam can be used to provide controlled hypotension during spinal surgery in children and adolescents. Future studies, with direct comparison to other commonly used agents, are needed to better define its advantages and disadvantages as well as its effects on estimated blood loss.     

Effects of desflurane and isoflurane on intestinal tissue oxygen pressure during colorectal surgery

Volatile anaesthetics differ in the effects they have on splanchnic haemodynamics and oxygenation. The aim of this study was to evaluate the effects of desflurane and isoflurane as part of a balanced anaesthetic technique on intestinal tissue oxygenation during colorectal surgery. Data were analysed from 44 patients randomly assigned to receive either desflurane (desflurane group, n = 20), or isoflurane (isoflurane group, n = 24) for inhalational anaesthesia. Tissue oxygen pressure (P(tiss)O2) was measured on the serosal side of the large intestine prior to colonic resection (T1) and following the completion of the bowel anastomosis (T2). In addition, haemodynamic and oxygenation parameters were assessed. No difference in mean P(tiss)O2 was observed between the groups at T1 [desflurane group: 8.1 (2.9) kPa vs. isoflurane group: 7.7 (2.7) kPa]. Following completion of the anastomosis (T2) mean P(tiss)O2 was higher in the isoflurane group [9.6 (2.9) kPa] than the desflurane group [7.7 (2.4) kPa, p = 0.025]. During surgery no difference between the groups could be observed with regard to haemodynamics and global oxygenation parameters. The lack of a difference between the groups in P(tiss)O2 before resection of the colon suggests that, under normal conditions, desflurane and isoflurane have comparable effects on intestinal blood flow and oxygenation. However, following local ischaemia, the reactive hyperaemia seems to be better preserved during isoflurane anaesthesia indicated by a local increase in P(tiss)O2blank(p = 0.013) following completion of the bowel anastomosis.     

Sevoflurane preserves endocardial blood flow during coronary ligation in dogs: comparison with adenosine

Background : Sevoflurane has been reported to attenuate ischaemia-induced changes of myocardial metabolism, but the mechanism is still unclear. We examined the effect of sevoflurane on regional myocardial blood flow (RMBF) in the ischaemic area and compared the flow with that in the presence of adenosine.
Method : Twenty-seven mongrel dogs were anaesthetized with fentanyl infused at the rate of 1μg.kg^-1.min^-1 throughout the experiment. Then they were divided into 4 groups; 0, 1, 2 MAC sevoflurane groups and adenosine group. Adenosine was infused into the left ventricle at a rate of 14.5 mg.kg^-1.h^-1. The left anterior descending coronary artery (LAD) was ligated for 3 min. RMBF in the endo- and epicardial layers were measured using coloured microspheres.
Results : Sevoflurane decreased both systolic and diastolic blood pressures and LV dp/dt max. Adenosine increased heart rate and coronary flow. The endocardial blood flow in 2 MAC sevoflurane was almost the same as that in the 0 MAC group. Adenosine significantly increased the myocardial blood flow. During 3-min ischaemia, endocardial blood flow in the ischaemic area under 2 MAC sevoflurane was essentially the same as those in 0 MAC and adenosine groups, though myocardial work in 2 MAC sevoflurane was lower compared with that of the other groups.
Conclusion : Preservation of endocardial blood flow related to the myocardial work during ischaemia occurred during 2 MAC sevoflurane. The decrease in LV dp/dt max induced by 2 MAC sevoflurane is one of the factors responsible for the preservation of the endocardial blood flow during ischaemia.     

不同剂量瑞芬太尼复合七氟醚控制性降压对神经外科手术患者脑氧代谢的影响

目的观察瑞芬太尼复合七氟醚控制性降压对神经外科手术患者脑氧代谢的影响。方法选择拟行控制性降压的神经外科手术患者60例,随机均分为三组:R1组为瑞芬太尼3ng/ml复合七氟醚组,瑞芬太尼效应室靶浓度设定为3ng/ml;R2组为瑞芬太尼6ng/ml复合七氟醚组,瑞芬太尼效应室靶浓度设定为6ng/ml;N组为硝普钠组。R1、R2组同时吸入七氟醚,控制七氟醚呼出气浓度为1MAC,N组泵注硝普钠的速率为1～3μg·kg-1·min-1。记录麻醉前10min(T0)、降压后10min(T1)、30min(T2)、停止降压10min(T3)、30min(T4)时的MAP和HR,采集相应时点的颈内静脉血和动脉血作血气分析,计算动脉血氧含量(CaO2)、颈内静脉球部血氧含量(CjvO2)、脑动-静脉血氧含量差(Da-jvO2)、脑氧摄取率(CERO2)。结果 T1～T4时R1、R2组,T1、T2时N组MAP明显低于T0时(P<0.01),T2时R2组MAP明显低于N组和R1组(P<0.05或P<0.01)。T1～T4时N组HR明显快于T0时和R1、R2组(P<0.01),T1～T3时R1、R2组HR明显慢于T0时,而T2时R2组HR明显慢于R1组(P<0.05或P<0.01)。T1～T4时三组CjvO2明显高于T0时(P<0.01),而Da-jvO2与CERO2明显低于T0时(P<0.01),T1、T2时R1、R2组CjvO2高于N组(P<0.05),而Da-jvO2与CERO2低于N组(P<0.05)。结论瑞芬太尼复合七氟醚控制性降压可降低神经外科手术患者的脑氧代谢,降压平稳迅速,HR缓慢,停止降压后无BP反跳现象,有利于围术期脑保护。     

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.