Subarachnoid clonidine reduces spinal cord blood flow and glucose utilization in conscious rats

The authors investigated the spinal blood flow and metabolic effects of subarachnoid clonidine in conscious rats prepared with chronically implanted subarachnoid catheters. For the blood flow experiments, rats received saline (n = 7) or clonidine 20 nmol (7 micrograms; n = 6), 100 nmol (27 micrograms; n = 5), or 400 nmol (107 micrograms; n = 7) intrathecally. Another group of rats received clonidine 400 nmol intravenously (n = 4). Spinal glucose utilization was measured in rats that received either saline (n = 5) or clonidine 100 nmol (n = 5) intrathecally. Spinal cord blood flow (SCBF) and glucose utilization were measured in five gray and three white matter areas of lumbar spinal cord 15 min after drug administration with the autoradiographic iodo-[14C]-antipyrine and 2-[14C]-deoxyglucose methods, respectively. Physiologic differences between the groups were minor. Rats in the blood flow experiments that received clonidine 100 nmol had a slightly lower arterial PO2 level (70 +/- 1 vs. 82 +/- 3 mmHg; P less than 0.05), whereas those in the glucose utilization group were mildly hypocarbic (PCO2 27 +/- 1 vs. 32 +/- 2 mmHg; P less than 0.01) relative to control animals. Only animals that received 400 nmol clonidine intrathecally had significant analgesia, as assessed by the tail-flick test. One control animal for the metabolism experiments was technically unsatisfactory and was excluded from data analysis. Subarachnoid clonidine reduced both SCBF and glucose utilization. In spinal gray matter, the largest decreases in flow (32-44%; P less than 0.01) occurred with 20 nmol clonidine, whereas flow decreased least (12-27%) with the 400-nmol dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epidural bupivacaine suppresses local glucose utilization in the spinal cord and brain of rats

Using the 2-[14C]deoxyglucose method, the effects of analgesic doses of epidural bupivacaine (300 micrograms) on local spinal cord glucose utilization (SP-LGU) of the cervical, thoracic, and lumbar regions and local cerebral glucose utilization (BR-LGU) in 38 brain structures were examined in conscious rats. In addition, the effects of intramuscular bupivacaine (300 micrograms) and the spinal cord transection (T2) were examined to determine whether the induced metabolic changes, if any, are related to the drug's systemic effect and/or deafferentation. Lumbar epidural bupivacaine sufficient to produce analgesia decreased SP-LGU in the thoracic (18-28%) and lumbar (21-29%) spinal cord but not in the cervical cord. Epidural bupivacaine decreased BR-LGU (15-26%) in 35 of 38 structures examined. With intramuscular bupivacaine, SP-LGU remained unchanged in almost all regions, while BR-LGU was significantly decreased (11-23%) in 23 structures. Plasma concentrations of bupivacaine in the epidural and intramuscular groups were comparable. With spinal cord transection alone, SP-LGU significantly decreased with varying degrees depending on the structure examined, but BR-LGU did not decrease in 36 of 38 structures examined. These results indicate that analgesic doses of epidural bupivacaine decrease SP-LGU, probably reflecting decreased neuronal activity of the spinal cord, and that reduced BR-LGU by epidural bupivacaine is most likely due to the drug's systemic effect rather than deafferentation.     

Local blood flow, oxygen tension, and oxygen consumption in the rat spinal cord. Part 1: Oxygen metabolism and neuronal function

A reliable and reproducible microelectrode technique provided consistent simultaneous measurements of local spinal cord blood flow (local SCBF), tissue oxygen tension (TO2), and tissue oxygen consumption (TO2C) in the rat. Local SCBF was measured by the hydrogen clearance technique, local TO2 was measured polarographically, and local TO2C was calculated from the declining slope of local TO2 following temporary arrest of local SCBF. Mean local TO2 values varied only slightly between gray and white matter, while local TO2C and SCBF maintained a 3 to 1 ratio between gray and white matter areas. Measurements were also made of these parameters in specific white matter tracts and laminae of Rexed. Local white matter SCBF was relatively homogeneous throughout the ventral, lateral, and dorsal funiculi. Gray matter blood flow was more variable with topography. The highest local SCBF was recorded in areas rich in internuncial neurons. The somatic motor regions had values slightly higher than recorded in sensory regions.     

Local spinal cord glucose utilization in conscious and halo-thane-anaesthetized rats

The authors used the 2-[14C]deoxyglucose method to study local spinal and cerebral glucose utilization simultaneously during 1.2 per cent halothane anaesthesia in adult Sprague-Dawley rats. In conscious animals (n = 5) the rate of glucose utilization in lumbar spinal gray matter was about 50 per cent lower than that of cerebral cortex. Halothane anaesthesia (n = 6) reduced spinal cord and cerebral metabolic rate. Spinal glucose utilization was reduced 12-35 per cent, but this was less than the 45-70 per cent decrease halothane produced in 8 of 16 cerebral structures examined and was independent of the hypotension produced. These results indicate that halothane is a spinal metabolic depressant but that its effects on this tissue are substantially less than those it has on many cerebral structures.     

The effects of subarachnoid lidocaine and phenylephrine on spinal cord and cerebral blood flow in dogs

To investigate the central nervous system circulation during spinal anesthesia, local spinal cord blood flow (SCBF) and cerebral blood flow (CBF) were measured simultaneously by the hydrogen clearance technique following subarachnoid lidocaine, phenylephrine, or a combination of both. The mean control values of SCBF and CBF were 22.4 +/- 7.9 ml X 100 g-1 X min-1 and 53.1 +/- 12.0 ml X 100 g-1 X min-1, respectively, in dogs lightly anesthetized with halothane. The subarachnoid administration of lidocaine solutions (1, 2, 3, and 5%), 1 ml, failed to produce statistically significant changes in SCBF (P greater than 0.05). Whereas, when phenylephrine (0.1, 0.2, 0.3, and 0.5%), 1 ml, was injected into the spinal subarachnoid space, SCBF decreased significantly with concentrations greater than 0.2% (P less than 0.05). When a mixture of lidocaine (24 mg) and phenylephrine (1 mg) was administered into the subarachnoid space, SCBF decreased significantly and returned to control within 60-90 min. CBF did not change significantly with any of the injections, remaining within less than +/- 12% of control. Dextrose solutions in water (5 and 7.5%), which were used for dilution of the drugs, did not affect either SCBF or CBF. These results indicate that local spinal cord blood flow can be affected significantly during spinal anesthesia when phenylephrine is added to the local anesthetic solution. However, the circulatory effects of drugs injected into the spinal subarachnoid space appear to be restricted to the local spinal cord per se and do not involve other parts of the CNS.     

Spinal cord blood flow during spinal anesthesia in dogs: the effects of tetracaine, epinephrine, acute blood loss, and hypercapnia

To examine the effects of subarachnoid tetracaine and epinephrine on spinal cord blood flow (SCBF), lumbar SCBF and cerebral blood flow (CBF) were measured simultaneously by the hydrogen clearance technique in dogs (n = 45) anesthetized with halothane. The lumbar subarachnoid administration of tetracaine, 5 mg dissolved in 1 ml of a 7.5% dextrose solution had no significant effect on either SCBF or CBF for 4 hr even though arterial blood pressure and heart rate decreased significantly. After subarachnoid epinephrine alone (100, 300, and 500 micrograms), SCBF varied widely but did not change significantly with any of the injections, nor did CBF. Responses of SCBF to hypercapnia and to acute blood loss during spinal anesthesia with tetracaine were also examined. Increased PaCO2 (from 35 to 57 mm Hg) increased both SCBF and CBF similarly before and after subarachnoid tetracaine; SCBF increased from 26.8 +/- 9.0 ml X 100 g-1 X min-1 (mean +/- SD) before to 34.2 +/- 13.6 ml X 100 g-1 X min-1 during hypercapnia during spinal anesthesia, which was almost identical to the increase (from 31.5 +/- 8.1 ml X 100 g-1 X min-1 to 39.9 +/- 6.0 ml X 100 g-1 X min-1) before spinal anesthesia. Whereas acute blood loss (approximately 20% of estimated blood volume) during spinal anesthesia with tetracaine caused a 23% reduction of SCBF (P less than 0.05), in the absence of tetracaine SCBF remained unchanged during hemorrhagic hypovolemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Spinal cord blood flow after intrathecal injection of ropivacaine and bupivacaine with or without epinephrine in rats

Background: Ropivacaine is a new local anaesthetic available for spinal and epidural anaesthesia. When new drugs are being introduced for spinal application, their effect on spinal cord blood flow (SCBF) should be studied for safety and toxicological aspects. In the present study, SCBF was studied after intrathecal (i. t.) application of ropivacaine and bupivacaine with and without epinephrine.
Method: SCBF was measured continuously in spontaneously breathing, enflurane/N₂O anaesthetized rats, using laser-Doppler flowmetry technique. The spinal cord was exposed by laminectomy at the L₁-L₂ level, and a laser-Doppler probe was placed over the dorsal horn, allowing on-line registration of SCBF in a tissue hemisphere of 1–2 mm. Relative changes in SCBF were then measured on-line after i. t. administration of increasing doses of ropivacaine, bupivacaine or bupivacaine with epinephrine.
Results: Ropivacaine and bupivacaine decreased SCBF in a dose-dependent manner. In contrast, the reduction in SCBF produced by bupivacaine + epinephrine (Bupi+Epi) was equal for all doses of bupivacaine. The order of magnitude of SCBF decreases was Bupi + Epi >ropivacaine>bupivacaine. The maximal decrease in SCBF at the highest concentration given (10 mg/ml) was 37±6% for ropivacaine, 27±7% for bupivacaine and 40 ±6% for bupivacaine + epinephrine.
Conclusion: Ropivacaine and bupivacaine produce a dose-related, transient decrease in SCBF following i. t. administration in anaesthetized rats. However, the decrease in SCBF produced by both ropivacaine and bupivacaine was less than that produced by bupivacaine, when epinephrine was added in a concentration of 5 μg/ml. These results suggest that ropivacaine, like bupivacaine, may be used for spinal anaesthesia without important effects on SCBF.     

Control of blood flow in the cat spinal cord

Spinal cord blood flow (SCBF) and the effect of end-tidal CO2 concentration (ETCO2) on SCBF (CO2 reactivity) were studied in the lumbar spinal cord of cats by means of the hydrogen-clearance technique Hydrogen gas was administered by inhalation, and its level in spinal cord tissue was estimated amperometrically with small (75 micrometers) platinum electrodes. The average SCBF's at normocapnia (ETCO2 = 4%) of the ventral horn gray matter and of the white matter at several locations were 43.2 and 16.2 ml . 100 gm-1 . min-1, respectively. For gray and white matter, the values of CO2 reactivity, estimated by the coefficient of the regression of SCBF (ml . 100 gm-1 . min-1) on ETCO2 (ml . 100 ml-1) were 11.6 and 2.1, respectively. No differences in SCBF or CO2 reactivity were observed between intact animals kept under N2O-O2 ventilation and decerebrated animals with no anesthesia. After an acute spinal section, ventral horn SCBF and CO2 reactivity (measured eight segments below the cordotomy) were not altered, in spite of the profound neural depression present (that is, spinal shock). Orthodromic (dorsal root) stimulation of the ventral horn neurons induced an average increase in blood flow of 128% above control values. Antidromic (ventral root) motoneuron activation failed to produce any significant changes in ventral horn blood flow.     

应用激光多普勒血流仪监测兔急性脊髓缺血损伤后腰髓血流动力学变化及病理学观察的研究

目的：应用激光多普勒血流仪监测兔脊髓缺血再灌流后腰髓血流的动态性变化，讨论腰髓血流的动力学特点。方法：通过阻断腹主动脉，造成脊髓腰尾段缺血。按缺血和再灌流各时间段分别连续测定腰髓血流变化。取缺血前、缺血４０分钟、再灌流４小时局部脊髓行组织病理和透射电镜检查。结果：在缺血４０分钟腰髓局部血灌流量迅速下降至基线值的－８１．５７％（Ｐ值＝２．０１Ｅ－１７）。再灌流时，局部血流迅速增高并超过基线水平。再灌流１０分钟，局部血灌流量与基线的百分比变化值为５７．９８％（Ｐ值＝３．３Ｅ－０７）。随后逐渐降低，再灌流１小时后，局部血灌流量基本恢复基线水平（３．９７％，Ｐ值＝０．５５７８９９）。以后血灌流量低于基线水平，出现缺血后延迟性低灌流。直至再灌流４小时（－２３．５％，Ｐ值＝１．８４Ｅ－０３）低灌流保持相对稳定，血流未见恢复。缺血４０分钟，有明确病理学改变；再灌流４小时后，病理学改变明显进一步加重。结论：上述结果对于脊髓缺血性损伤后继发性功能障碍提供了理论依据。     

The influence of spine distraction on cat spinal cord blood flow and evoked potentials

The changes of spinal cord blood flow (SCBF) and spinal cord evoked potential (SCEP) due to spine distraction were analyzed in 30 cats. Spine distraction was performed at L1/2 level at which spinal bodies were separated surgically. SCBF was measured by means of a microsphere technique before, during and after spine distraction and SCEP elicited by spinal cord electrical stimulation was recorded simultaneously. With slight spine distraction (SCEP amplitude 80-100%), SCBF was increased significantly over normal value. SCBF was decreased significantly by further distraction (SCEP 50-80%), but was recovered over normal value after the release of distraction. When severe distraction (SCEP less than 50%) was applied, decreased SCBF around L1 level was irreversible. These results suggested that the disorder of SCBF regulating system due to spine distraction could be expected by analyzing changes of the SCEP.     

内皮素受体拮抗剂对损伤脊髓早期保护作用

目的评价非选择性内皮素(ET)受体拮抗剂PD145065对损伤脊髓的保护作用,证实ET参与脊髓损伤(SCI)后继发损伤的假设并探讨其作用机制。方法压迫法致伤大鼠脊髓(50g,1min)。损伤前10min鞘内注射PD145065或生理盐水,观察脊髓血流(SCBF)、丙二醛(MDA)、细胞内钙(［Ca2+］i)、伊文思兰(EB)及水含量变化。结果伤区SCBF在伤后5min即有明显下降,为基线的(75.23±9.21)%,2h降为(57.06±7.35)%;伤区邻近血流下降较慢,伤后30min降为(79.82±7.98)%。伤区及邻近区伤后4h?SCBF都未恢复。伤段脊髓组织中MDA、［Ca2+］i、EB和水含量均高于假手术组(P＜0.05)。PD145065明显改善了伤区SCBF,消除了伤区邻近段SCBF的下降。PD145065预处理组脊髓中MDA、［Ca2+］i、EB和水含量均低于生理盐水组(P＜0.05)。结论PD145065对损伤脊髓早期有明显保护作用,ET及其受体可能通过多种途径参与SCI后的继发损伤。临床应用ET受体拮抗剂对SCI可能有治疗作用。     

Effects of a single large dose of methylprednisolone sodium succinate on experimental posttraumatic spinal cord ischemia. Dose-response and time-action analysis

The ability of a single large intravenous dose of methylprednisolone sodium succinate (MPSS: 15, 30, or 60 mg/kg) to modify the evolution of lumbar spinal cord ischemia in cats undergoing a contusion injury of 500 gm-cm is examined. Repeated measurements of spinal cord blood flow (SCBF) in the dorsolateral funiculus were made via the hydrogen clearance technique before and for 4 to 5 hours after injury. The mean preinjury SCBF for all animals was 12.29 +/- 0.77 ml/100 gm/min. Following injury, SCBF began to decrease progressively in vehicle-treated animals to a level of 7.71 ml/100 gm/min, a fall of 37.3%. In contrast, cats that received a 30-mg/kg intravenous dose of MPSS at 30 minutes after injury maintained SCBF within normal limits (p less than 0.05 at 3 and 4 hours after contusion). A 15-mg/kg MPSS dose was less effective at preventing posttraumatic white matter ischemia, and a 60-mg/kg dose was essentially ineffective. It was determined that the 30-mg/kg MPSS dose was optimal for supporting SCBF when the drug was given at 30 minutes after spinal trauma, and a second series of experiments was carried out to examine the ability of this dose, when given at longer latencies, to improve decreased flow. Methylprednisolone given at 1 1/2 hours after injury in four cats produced a slight (12.7%) but transient improvement in SCBF, and when administered at 4 1/2 hours in another three animals was totally ineffective. These results show that MPSS in a 30-mg/kg dose can prevent posttraumatic spinal cord ischemia. However, it would appear that the ability of the steroid to reverse the ischemia once it has developed is limited, and probably lost, within a few hours of onset. This further suggests that the ischemic process is irreversible and underscores the need for early treatment with a large MPSS dose in order to prevent full development of ischemia and to promote neurological recovery.     

Successful improvement of blood pressure, cardiac output, and spinal cord blood flow after experimental spinal cord injury

Thirty-seven rats were anesthetized and ventilated and had continuous monitoring of mean systemic arterial pressure (MSAP) and central venous pressure (CVP). The animals underwent a 60-g clip compression injury at T-1 for 1 minute. Fifteen minutes after injury, microspheres were used to measure cardiac output (CO) and spinal cord blood flow (SCBF). Each animal was then randomized into one of five groups. Four groups received intravenous infusions for 1 hour each of 5% albumin, autologous packed cells, low molecular weight dextran, or autologous whole blood to maintain the MSAP. The fifth group served as a control group and received an infusion of normal saline. Seventy-five minutes after injury, CO and SCBF were measured. The posttraumatic reduction in CO was significantly improved by all four treatment infusions. However, only autologous whole blood and dextran successfully reversed the posttraumatic hypotension. Dextran significantly elevated the CVP (P less than 0.01) and reduced the hematocrit (P less than 0.01). Whole blood improved SCBF in all segments of the spinal cord by nearly 100% (P less than 0.05), and dextran increased SCBF by 200% (P less than 0.01). Thus, the most marked improvements in MSAP, CO, and SCBF were produced by hypervolemia and hemodilution associated with dextran infusion. The therapeutic implications of this reversal of local and systemic changes in acute spinal cord injury are discussed.     

Effects of aortic occlusion on regional spinal cord blood flow and somatosensory evoked potentials in sheep

Somatosensory evoked potentials (SEPs) were recorded continuously during aortic occlusion in sheep, with simultaneous measurement of spinal cord blood flow (SCBF) by radiolabeled microspheres. Aortic occlusion was associated with disappearance of the SEPs in seven of nine sheep in 7.8 +/- 4.1 (SD) minutes. SCBF at the time of initial cross clamping and 30 minutes after the onset of ischemia revealed a severe reduction in white and gray matter flow in the thoracolumbar cord. Release of the aortic clamp was associated with reactive hyperemia in these ischemic regions. In two animals, the SEP persisted during aortic cross clamping. The total SCBF in the thoracic and lumbar regions of these two animals exceeded 20 ml/100 g/min after 30 minutes of ischemia and was significantly greater than the flow recorded in sheep whose evoked response disappeared. The relation between spinal cord ischemia and evoked potential alterations is discussed in detail.     

Effects of ethanol on spinal cord blood flow in the rat

This study examines the effects of low and high concentrations of ethanol on spinal cord blood flow (SCBF) in the rat. SCBF was measured in the following blood pressure ranges: (a) <60 mm Hg, (b) 60-90 mm Hg, (c) 90-120 mm Hg, (d) 120-150 mm Hg, and (e) >150 mm Hg. Rats were anesthetized with 1.4% isoflurane in air and randomly assigned to the following treatment groups: group 1 (n = 12), intraperitoneal (i.p.) saline injection; group 2 (n = 10), 1 g/kg of ethanol i.p.; and group 3 (n = 14), 4 g/kg of ethanol i.p. Blood pressure was increased by intravenous phenylephrine infusion or lowered by a combination of intravenous trimethaphan and blood withdrawal. The SCBF was measured in cervical, thoracic, and lumbar segments using radioactive microspheres. The plasma ethanol concentration was 0 mg/ml for group 1, 0.64 +/- 0.06 mg/ml (mean +/- SEM) in group 2, and 4.18 +/- 0.11 mg/ml in group 3. In control rats, the cervical SCBF was higher than the thoracic or lumbar SCBF, evaluated over the entire blood pressure range (analysis of variance, p <0.05). This difference in regional SCBF was abolished by ethanol. Ethanol produced a significant decrease in cervical and lumbar SCBF (p <0.05) but not thoracic SCBF (p = 0.07). This decrease in SCBF was most pronounced at high blood pressures. These results suggest that ethanol produces vasoconstriction in the spinal cord that is countered by autoregulatory vasodilation at low blood pressures.     

Spinal cord blood flow in the rat under normal physiological conditions

Regional spinal cord blood flow (SCBF) was measured in a group of rats under conditions of normothermia, normocarbia, normoxia, and normal blood pressure, using the hydrogen clearance technique. Regional SCBF in the cervical white matter was 26.8 +/- 1 (SE) ml/100 g/min and in the cervical gray matter 53.6 +/- 2.5; in the thoracic white matter it was 22.2 +/- 2.4 ml/100 g/min and in the thoracic gray matter 41.2 +/- 12/6 ml/100 g/min; and in the lumbar gray matter it was 52.3 +/- 1.9 ml/100 g/min. The effect of changes in blood pressure on SCBF (autoregulation) was investigated in nine rats. We have observed that SCBF remains relatively constant in the blood pressure range of 45 to 165 mm Hg and assumes a passive flow below or above this range.     

Relation between spinal cord blood flow and functional recovery after blocking weight-induced spinal cord injury in rats

Spinal cord blood flow (SCBF) and motor performance on the inclined plane were measured up to 9 days after a reversible spinal cord compression injury in 49 Sprague-Dawley rats. A load of 35 g on 11 mm2 of the thoracic spinal cord for 5 minutes caused transient paraparesis with a decrease in the capacity angle on the inclined plane from 62 +/- 1 degree (mean +/- SEM) before injury to 33 +/- 1 degree on Day 1, 45 +/- 2 degrees on Day 4, d and 54 +/- 3 degrees on Day 9. SCBF was measured by the [14C]iodoantipyrine method, and in gray matter there was a decrease from 78.4 +/- 2.3 ml/min/100 g of tissue in uninjured animals to 33.7 +/- 1.5 ml/min/100 g of tissue on Day 1 after injury, increasing to 50.1 +/- 2.0 on Day 4 and to 70.5 +/- 2.7 ml/min/100 g of tissue on Day 9. At the corresponding times, the SCBF values in white matter were 14.5 +/- 0.5, 6.7 +/- 0.5, 10.2 +/- 0.6, and 13.4 +/- 0.6 ml/min/100 g of tissue, respectively. The animals in another group were loaded with 25 g for 5 minutes and on Day 1 exhibited a capacity angle of 43 +/- 2 degrees while the SCBF values for gray and white matter were 55.1 +/- 2.0 and 11.1 +/- 0.4 ml/min/100 g of tissue, respectively; thus, the results in this group were similar to the values on Day 4 in the animals loaded with 35 g.(ABSTRACT TRUNCATED AT 250 WORDS)     

Levobupivacaine versus racemic bupivacaine in spinal anaesthesia for urological surgery

Racemic bupivacaine is the most common local anaesthetic used intrathecally. This prospective, randomized, double-blind study compared the clinical efficacy and motor block of 0.5% levobupivacaine with 0.5% racemic bupivacaine in spinal anaesthesia for urological surgery. The surgery required an upper level of sensory block of at least the tenth thoracic dermatome. Fifty patients were recruited (levobupivacaine group n = 24; bupivacaine group n = 26). Spinal anaesthesia was achieved with 2.6 ml of study solution injected in the subarachnoid space at the lumbar 3/4 interspace. One patient from the levobupivacaine group was excluded due to technical failure. There were no significant differences between the two groups in the quality of sensory and motor block or in haemodynamic change. Anaesthesia was adequate and patient satisfaction good in all cases. We conclude that 0.5% levobupivacaine can be used as an alternative to 0.5% racemic bupivacaine in spinal anaesthesia for surgery when a sensory block to at least T10 is required.     

Effect of Subarachnoid Bupivacaine Block on Anesthetic Requirements for Thiopental in Rats

Background: Subarachnoid bupivacaine blockade has been reported to reduce thiopental and midazolam hypnotic requirements in patients. The purpose of this study was to examine if local anesthetically induced lumbar intrathecal blockade would reduce thiopental requirements for blockade of motor responses to noxious and nonnoxious stimuli in rats.

Methods: After intrathecal and external jugular catheter placement, rats were assigned randomly to two groups in a crossover design study, with each rat to receive either 10 micro liter of 0.75% bupivacaine or 10 micro liter of normal saline intrathecally. The doses of intravenously administered thiopental required to ablate the eyelid reflex, to block the withdrawal reflex of a front limb digit, and to block the corneal reflex were compared. In two separate groups of animals, hemodynamic parameters and concentrations of thiopental in the brain were compared between intrathecally administered bupivacaine and saline.

Results: The thiopental dose required to block the described responses was decreased with intrathecally administered bupivacaine versus intrathecally administered saline from (mean +/- SD) 40 +/- 5 to 24 +/- 4 mg/kg (P < 0.001) for the eyelid reflex, from 51 +/- 6 to 29 +/- 6 mg/kg (P < 0.005) for front limb withdrawal, and from 67 +/- 8 to 46 +/- 8 mg/kg (P < 0.01) for the corneal reflex. The concentration of thiopental in the brain at the time of corneal reflex blockade for the group given bupivacaine was significantly lower than in the group given saline (24.1 vs. 35.8 micro gram/g, P = 0.02).     

缺血和再灌流对脊髓血流量及运动诱发电位的影响

本文采用家兔失血性休克模型，使血压下降至３０ｍｍＨｇ维持３０ｍｉｎ后再灌流，让血压回升到正常范围。观察缺血再灌流期 ＳＣＢＦ和 ＳＥＰ变化。缺血期平均动脉压 ３０～４０ｍｍＨｇ，脊髓 Ｔ１２及Ｌｌ节段灰质血流量减少５７％～６４％，白质血流量减少３２％～５０％；ＳＭＥＰ的潜伏期明显延长（Ｐ＜０．００１），各波的波幅降低并有２５％～６７％的波幅消失。再灌流期当血压回升到９０～１３０ｍｍＨｇ时，灰质血流量仍低于伤前（Ｐ＜０．０１），白质血流量无显著差异．ＳＭＥＰ潜伏期仍明显延长（Ｐ＜０．０５），除Ｐｌ波波幅下降有统计意义外，其它各波幅无差异，波幅消失占２５％～３３．３％。光镜下见脊髓存在损伤性病理变化，显示缺血再灌流后脊髓组织仍然存在继发缺血性病理损害和神经功能障碍。