Effects of lumbar spinal fusion on the other lumbar intervertebral levels (three-dimensional finite element analysis)

The risk of accelerating the degeneration of adjacent disc levels after lumbar spinal fusion is a controversial issue. A finite element model consisting of L1 to L5 lumbar spines was used to assess the effect on adjacent disc level after lumbar spinal fusion. We compared intact, L4/5 posterior interbody fusion (PLF), and L4/5 posterior lumbar interbody fusion (PLIF) models. The loading conditions applied were compressive force, compressive force plus flexion moment, and compressive force plus extension moment. Evaluations were made for von Mises stress on each vertebral end-plate, Tresca stress of all the annulus fibrosus, and Tresca stress of the annulus fibrosus from the posterior surface of the disc to the neural foramen. As the result, the von Mises stress adjacent to the fusion level was higher than the other nonfusion levels; it was higher under conditions of flexion moment loading plus compression loading [112% (2.59PMa) in the PLF model and 117% (2.72Mpa) in the PLIF model] than in the intact model. The Tresca stress of all the annulus fibrosus adjacent to the fusion level was higher than that on other nonfusion intervertebral levels; it was higher under conditions of flexion moment loading plus compression loading [127% (0.57PMa) in the PLF model and 209% (0.89Mpa) in the PLIF model] than in the intact model. The Tresca stress of the annulus fibrosus from the posterior surface of the disc to the neural foramen adjacent to the fusion level was higher than that on other nonfusion intervertebral levels; and it was higher under conditions of flexion moment loading plus compression loading [107% (1.48PMa) in the PLF model and 112% (1.54Mpa) in the PLIF model] than in the intact model. These findings demonstrate that with lumbar fusion, stresses on the vertebral end-plate and the annulus fibrosus were high adjacent to the fusion level; furthermore, stresses were higher in the PLIF model than in the PLF model. These results suggested that lumbar spinal fusion might bring with it a risk of damage to the annulus fibrosus and the vertebral end-plate adjacent to the fusion level.     

Efficacy of extracorporal shock-wave treatment for calcific tendinitis of the shoulder: experimental and clinical results

The effects of various extracorporal shock wave energy levels and impulse rates were investigated using an in vitro model. In addition, we performed a controlled, randomized study to examine the clinical outcome after treatment for calcific tendinitis of the shoulder. Two groups of 40 patients each received 2000 impulses twice with an energy flux density of 0.23mJ/mm² and then 0.42mJ/mm². The results were evaluated by the Constant and Murley score. Disintegration of the implanted deposits requires an energy of at least 0.42mJ/mm² and 2000 impulses. The clinical trial showed resorption of calcific deposits in 37.5% (0.23mJ/mm²) and 55.0% (0.42mJ/mm²). After 1 year the Constant and Murley score increased from 46 to 68 at 0.23mJ/mm² and from 48 to 73 points at 0.42mJ/mm². Based on our experimental and clinical results it is evident that disintegration of calcific deposits is dose-dependent. Because of the time that elapses until changes became evident on the radiographs, an instant and sole mechanical effect on the calcific deposits is unlikely. Therefore, a combined mechanical and cellular mechanism for absorption of the calcific deposits must be presumed.     

Addition of epinephrine to intrathecal tetracaine augments depression of the bispectral index during intraoperative propofol sedation

Purpose Epinephrine added to local anesthetic agents for spinal anesthesia is frequently used to prolong the duration of anesthesia. Epinephrine stimulates the -adrenoceptor, and it is known that the 2-adrenoceptor agonists have a central inhibitory effect. We investigated the effect of intrathecal epinephrine during propofol sedation with spinal anesthesia, using a bispectral index (BIS) monitor.Methods Twenty adult patients, scheduled for spinal anesthesia, were allocated to the control group (n = 10) or epinephrine group (n = 10). Patients in the control group received 14mg of tetracaine, whereas the epinephrine group received 14mg of tetracaine and 0.2mg of epinephrine. Immediately after the pinprick test, propofol was administered at 0.5mg·kg^–1 by infusion for the initial dose, then continuously at 2mg·kg^–1·h^–1 in both groups. BIS scores were recorded before subarachnoid block, and then every 5min for 90min after subarachnoid block.Results There were significant differences in the BIS score between the two groups at 45–55min and at 60–70min after subarachnoid block.Conclusion Intrathecal epinephrine augments the sedative effect of propofol during spinal anesthesia.     

Secondary growth of a cortical necrosis: effect of NOS inhibition by aminoguanidine post insult

Summary ¶Background. A cortical tissue necrosis from a focal freezing injury expands to 140% of its initial volume within 24hrs in rats. Previous studies of our laboratory have shown that administration of the NOS inhibitor aminoguanidine (AG) prior to trauma attenuates this process of secondary brain damage. Objective of the present study was to analyse whether this agent is also protective when treatment commences after the insult. Method. A highly standardized freezing lesion was induced in the brain cortex of 30 anaesthetized rats. The animals were divided into three experimental groups. Animals of group I (sham-5min, n=10) were sacrificed 5min after trauma for quantitative histomorphometric assessment of the primary cortical lesion. Animals of group II (sham-24h, n=10) received isotonic saline (16.7ml/kg b.w., i.p.) at 15min and 8hrs after trauma. In the treatment group (group III, AG-24h, n=10), AG was administered (100mg/kg b.w.) also at 15min and 8hrs after trauma. 24hrs later – the time point of maximal lesion spread – the animals of group II and III were sacrificed for quantification of the secondary lesion growth. Findings. The focal freezing injury produced a cortical necrosis volume of 6.07±1.04mm³ immediately after trauma (group I). After sham treatment, the necrosis expanded to 8.39±1.57mm³ within 24hrs (group II) corresponding to a lesion growth of 138% compared to the primary necrosis (p<0.01 vs. group I). In animals treated with AG after the trauma (group III), the volume of necrosis was significantly attenuated at 24hrs to 6.77±0.87mm³ representing an expansion of the lesion to only 112% (p<0.05 vs. group II). Thus, AG was inhibiting the secondary growth of necrosis by no less than 69%. Interpretation. The findings demonstrate that AG retains its neuroprotective potential against secondary brain damage from trauma even when administration begins after trauma.Published online October 20, 2003     

Prostaglandin E1 reduces blood loss during and after resection of lumbar herniated disc

Controlled hypotension was employed during resection of lumbar herniated disc on 10 patients. Prostaglandin E₁ (PG) was used as a hypotensive agent. The systolic blood pressure was lowered less than 100mmHg in the hypotensive group. The average blood loss during surgery was 95 ± 41ml for the hypotensive group compared with 154 ± 81ml for the normotensive group (P 0.05). The blood loss after surgery was also significantly less in the hypotensive group than in the normotensive group (P 0.05). We conclude that PG is an effective hypotensive agent on blood loss during and after surgery.(Kashimoto S, Nakamura T, Yamaguchi T: Prostaglandin E₁ reduces blood loss during and after resection of lumbar herniated disc. J Anesth 6: 294–296, 1992)     

The intrathecal spread of hyperbaric dibucaine in adolescents

We investigated the spread of spinal anesthesia with hyperbaric dibucaine in 20 adolescents aged 9–18yr and 20 adults aged 23–53yr. No significant difference was found between the two groups with regard to height, whereas a statistical significant was found between the two groups with regard to weight. Spinal anesthesia was conducted with Neo-Percamin S^® injected at the L3–L4 interspace through a 25-gauge spinal needle. Injected volumes of the anesthetic solution were calculated from the patients height at 0.01ml·cm^–1. In adolescents, 1.6 ± 0.1ml (mean ± SD) of the anesthetic solution produced 19.4 ± 1.5 spinal segments blocked. In adults, 1.6 ± 0.1ml of the solution produced 13.4 ± 1.6 spinal segments blocked. A high spinal anesthesia above T5 was achieved in 17 (85%) patients in adolescents, whereas such a high level of spinal anesthesia was not experienced in adults. These results suggest that the hyperbaric dibucaine solution for spinal anesthesia in adolescents may have a tendency to produce an unexpectedly extensive spread of anesthesia.(Hirabayashi Y, Shimizu R: The intrathecal spread of hyperbaric dibucaine in adolescents. J Anesth 7: 167–172, 1993)     

Epidural administration and analgesic spread: Comparison of injection with catheters and needles

This study was designed to investigate differences in epidural analgesic spread between catheter and needle injections in 48 patients with comparable physical characteristics. The spread of analgesia in the catheter injection group with a 0.24ml·sec^–1 injection rate (n = 16) was 16.8 ± 1.5 spinal segments and that in the needle injection group at the same injection rate (n = 16) was 12.5 ± 1.8 spinal segments (P 0.01). Needle injection at the faster rate of 1.2ml*237sec^–1 (n = 16) produced a significantly greater spread of analgesia than with the 0.24ml·sec^–1 rate through the needle (16.2 ± 1.6 vs 12.5 ± 1.8 spinal segments, P 0.01). Thirteen of 16 patients receiving the fast needle injection complained of back compression or discomfort during the injection.The injection through an epidural catheter and the fast (1.2ml·sec^–1) injection through a needle produced extensive and equivalent epidural analgesic spread. However, because of patients discomfort with fast injection through the needle, the authors conclude that when using continuous epidural anesthesia, the initial injection of local anesthetic should be administered through the epidural catheter not the needle.(Omote K, Namiki A, Iwasaki H: Epidural administration and analgesic spread: comparison of injection with catheters and needles. J Anesth 6: 289–293, 1992)     

Analgesic dose-response relation in cervical epidural block

The relationship between the age and the spread of analgesia from different epidural anesthetic doses was examined by studying analgesic dose responses in cervical epidural analgesia. Two different anesthetic doses (5ml or 10ml) of 2% mepivacaine were injected into the cervical epidural space at a constant pressure (80mmHg) using an intravenous apparatus, and the spread of analgesia to pinprick was assessed. The significant correlation was found between the patients age and the number of spinal segments blocked (5ml:r = 0.8498, P < 0.01, 10ml:r = 0.5988, P < 0.01). The inverse linear relationship was found between the patients age and the segmental dose requirement (5ml:r = –0.6754, P < 0.01, 10ml:r = –0.5784, P < 0.01). Patients under 39 years of age showed a direct relationship between the dose injected and the number of spinal segments blocked, enabling prediction of the number of segments blocked with a given dose of local anesthetic. Doubling the epidural dose approximately doubled the number of spinal segments blocked. The analgesic dose-response relation in patients over 60 years of age differed from that in patients under 39 years of age and doubling the epidural dose did not double the number of spinal segments blocked. Progressively more extensive analgesia was obtained from a given dose of local anesthetic with advancing age. It was difficult to limit the extent of analgesia by injecting a smaller dose of local anaesthetic in the elderly.(Hirabayashi Y, Matsuda I, Inoue S et al.: Analgesic dose-response relation in cervical epidural block. J Anesth 2: 22–27, 1988)     

Bench test assessment of the new Raumedic Neurovent-P ICP sensor: a technical report by the BrainIT group

Summary. Background. In clinical practice, fiberberoptic and piezo-electric ICP probes are often used for measuring intracranial pressure (ICP). A number of similar technologies, although performing well in bench test studies, have been shown to exhibit unacceptable zero drift, fragility or both during trials conducted under clinical conditions. Recently, a new technology has become available, the Neurovent-P (Raumedic AG+CO, Raumedic, Germany). As a pre-requisite for a clinical trial, we have conducted and report on bench test studies to confirm the manufacturers long term zero-drift performance for this technology.Method. In a test rig static tests (recording of 20mmHg pressure) and dynamic tests, ranging from 5 to 50mmHg have been performed.Findings. 10 ICP probes have been tested for a total of 60 days. All the catheters, after the connection with the ICU monitor displayed a static pressure of 0±1mmHg and did not required pre-insertion alteration. At five days, mean zero drift was 0.6±0.9mmHg. Overall, zero drift ranged from 0 to 2mmHg. At a fixed static pressure of 20mmHg, the mean recorded value was 20.6±0.8mmHg, ranging from 19 to 23mmHg. A regression analysis of the relationship between the applied pressure and the recorded pressure during the dynamic tests of the 10 catheters yielded a correlation coefficient R² of 0.997. Applying the Altman and Bland method to assess the bias and confidence limits for the Raumedic catheter responses during the dynamic tests against the applied gold-standard hydrostatic column pressures, the average bias of –0.66±0.85mmHg, with 95% CLs of –2mmHg and 1mmHg.Conclusions. Mean zero drift, after five days, was very small and long-term continuous recording of a stable pressure was very precise. The response at dynamic tests, i.e. the changes of pressure in a wide range, was excellent. The average bias of the Raumedic catheter compared with the hydrostatic column is very small. After this bench test, the next and most critical step will be to conduct a trial of this promising technology under more demanding clinical environment.     

Bone mineral density in women with sarcoidosis

Sarcoidosis is a multisystem granulomatous disease of unknown etiology. Almost any organs of the body, but mostly the lungs, are involved. Bone mineral density (BMD) can be affected directly or indirectly in chronic granulomatous systemic diseases such as sarcoidosis. The aim of our study was to evaluate BMD in premenopausal and postmenopausal sarcoidosis patients with or without prednisone treatment and to compare their BMD values with those of a control group having the same menopausal status. Thirty-five premenopausal women (18 untreated, 8 treated, and 9 controls) and 21 postmenopausal women (5 untreated, 5 treated, and 11 controls) were included in the study. All of the patients had a histologically proven diagnosis and were being followed-up at the Sarcoidosis Outpatient Clinic of our unit. BMD of the lumbar (L) spine and femoral neck was measured by dual-energy absorptiometry (DEXA). The subgroups of premenopausals and postmenopausals were compared separately. Comparison among the groups was performed by using analysis of variance. Age, duration of the disease, and body mass index were comparable in treated, untreated, and control subgroups of the pre- and postmenopausal groups, and the subgroups of postmenopausals had comparable durations since menopause. For premenopausals, BMD values at L1–4 were not significantly different among the subgroups (0.920 ± 0.08g/cm², 0.801 ± 0.09g/cm², and 0.910 ± 0.05g/cm², for untreated, treated, and controls, respectively). However, the BMD value at the femoral neck in treated patients (0.921 ± 0.1g/cm²) was significantly lower than the values in untreated patients (1.080 ± 0.2g/cm²; P 0.01) and in controls (1.028 ± 0.17g/cm²; P 0.05). For postmenopausals, the BMD value at L1–4 in controls (1.019 ± 0.07g/cm²) was significantly higher than the values in untreated patients (0.783 ± 0.01g/cm²) and in treated patients (0.751 ± 0.08g/cm²; P 0.001 for both). The BMD value at the femoral neck in controls (0.890 ± 0.1g/cm²) was higher than the values in untreated patients (0.745 ± 0.08g/cm²) and treated patients (0.747 ± 0.1g/cm²), but the difference was not statistically significant (P = 0.06). We concluded that sarcoidosis patients, especially postmenopausal patients with corticosteroid treatment, may have an increased risk of bone mineral loss. Large-scale studies are warranted in order to delineate the exact roles of the disease itself, menopausal status, and corticosteroid treatment in this bone mineral loss.     

Comparison of anesthetic effects of epidural and intravenous administration of buprenorphine during operation

Thirty six patients were received epidural anesthesia with or without buprenorphine (BPN) during upper abdominal surgery. They were divided into three groups of 12 patients as follows; G-I received 20ml of 1% lidocaine epidurally, G-II received 20ml of 1% lidocaine epidurally and 0.6mg BPN intravenously, G-III received 20ml of 1% lidocaine with 0.6mg BPN epidurally. Additional 5ml of 1% lidocaine was given to any patient if systolic blood pressure or heart rate increased 10% compared to control value. Trachea was intubated following anesthetic induction with thiopental. The lungs were ventilated with a mixture of N₂O/O₂ (33%) and pancuronium was used for muscle relaxation. The total required doses of lidocaine in G-II and G-III were decreased 60% compared to control group (G-I) (P 0.05). The mean period of time until the first administration of pentazocine for postoperative pain was 13 ± 10hr (mean ± SD) in G-II and 19 ± 24hr in G-III compared to 5 ± 4hr in G-I (P 0.001). The dose of the administration of pentazocine that was required for pain relief during the first 48 postoperative hr in G-III was 54 ± 10mg (mean ± SD) compared to 150 ± 21mg in G-I (P 0.02) and 106 ± 28mg in G-II (P 0.05). Recovery from anesthesia in G-III was more rapid than that in G-I (P 0.05). The Pa_{CO 2} values in G-II and G-III increased 15% compared to control group at about 4hr and 8hr after administration of BPN, but any clinical treatment was not needed for them. Nonrespiratory side effects, e.g., nausea, vomiting, fatigue and headache, were comparably common in all groups. Mild hematuria associated with acute hypotension occurred in two patients in G-II (17%) immediately after the intravenous injection of 0.6mg of BPN. The results showed that 0.6mg of BPN given epidurally demonstrated better anesthetic and more potent postoperative analgesic effects and lesser side effects than 0.6mg of BPN given intravenously in patients undergoing upper abdominal surgery.(Yonemura E, Fukushima K.: Comparison of anesthetic effects of epidural and intravenous administration of buprenorphine during operation. J Anesth 4: 242–248, 1990)     

Hospital Readmissions Following Abdominal Aortic Aneurysm Repair

In-hospital outcomes associated with abdominal aortic aneurysm (AAA) repair are well described. However, little is known about post-discharge readmission rates, lengths of stay, associated mortality, and costs. We examined 206 consecutive patients who underwent AAA repair at two American hospitals between 1998 and 2000. Index hospitalization and 6-month readmission data were extracted from a resource and cost accounting system used by both hospitals. Among the 206 patients, 183 survived until discharge (mortality rate 11.2%). Among the surviving patients, 38 (21.0%) were readmitted within 6 months. Half of the readmissions occurred within two weeks of discharge, with patients presenting with a diverse array of complications. Nonelective repair and diabetes mellitus were independent predictors of hospital readmission (OR=2.83, 95% CI=1.25-6.40, p=0.01; OR=6.60, 95% CI=1.02-42.4, p=0.047, respectively). For each readmission, the mean length of stay was 10.7±2.5 days and the mean cost was $13,397±3,381. The cumulative number of hospital days during the 6 months post-discharge was 17.7±3.5 days for each readmitted patient and the mean per-patient total cost was $23,262±5,478. The mortality rate among readmitted patients was 13.2%. Overall, readmissions following AAA repair accounted for a cost >50% over and above the cost of the readmitted patients index hospitalization. Hospital readmissions are common during the 6 months following AAA repair. Patients who are readmitted experience long lengths of stay and high mortality rates, and their care incurs high costs.Dr. Eisenberg is a Physician-Scientist of the Quebec Foundation for Health Research. Dr. Pilote is a Physician-Scientist of the Canadian Institutes for Health Research.     

Effects of Cilostazol on Human Venous Smooth Muscle

In this study, we evaluated the effect of therapeutic doses of cilostazol on human venous smooth muscle. Saphenous vein rings (two to four per patient sample) were suspended in tissue baths for isometric tension recordings. At the beginning of the experiment, optimal tension for isometric contraction was achieved for each ring in a stepwise fashion in the presence of norepinephrine (10^–2 M). Norepinepherine was then added cumulatively in half-molar increments and isometric tension developed by the rings was measured, thereby obtaining a dose-response curve. Following washout and reequilibration, the rings were precontracted with a 30-50% submaximal dose of norepinepherine determined from the dose-response curve and allowed to contract until a stable plateau was reached. Cilostazol was then added in a cumulative manner (680-2,720 g/L), and the tension generated was recorded. A total of 76 venous rings were tested, and all relaxed in the presence of cilostazol. The amount of relaxation increased as the concentration of cilostazol increased. Relaxation of 15±1.9% (mean±SEM) at low cilostazol doses (680 g/L) to 37±3% at high cilostazol doses (2,720 g/L) was demonstrated. A second finding of this study was demonstrated when the patient samples were divided according to the presence or absence of risk factors for arteriosclerosis. The specific risk factors examined included diabetes mellitus, smoking, hypercholesterolemia, and hypertension. The presence or absence of hypertension (n=52) or hypercholesterolemia (n=18) did not affect the amount of relaxation of the venous rings. Smokers (n=46) had less relaxation 16±2.4% (680 g/L) to 41±3.6% (2,720 g/L) compared to nonsmokers (n=53) who relaxed 22±3.5% (680 g/L) to 48±5.7% (2720 g/L). This did not reach statistical significance at any concentration cilostazol (p=0.11-0.18). Diabetics (n=53) did have statistically significantly less relaxation at every concentration of cilostazol compared to nondiabetics (n=11, p < 0.05). All venous rings relaxed in the presence of cilostazol. Veins of nondiabetics relaxed statistically significantly more than those of diabetics. Smokers had less relaxation than non-smokers, but this was not statistically significant. We are the first to demonstrate that human venous smooth muscle cells undergo relaxation when exposed to therapeutic concentrations of cilostazol.     

Combined effects of Inversed Ratio Ventilation (IRV) with positive end-expiratory pressure ventilation (PEEP) on cardiorespiratory function in acute respiratory failure

Combined effects of inversed ratio ventilation (IRV) with positive end-expiratory pressure (PEEP) on cardiorespiratory function were examined in 24 patients with acute respiratory failure. Patients were divided into two groups: the IRV group (n = 12) who showed no significant increase in Pa_{O 2} with a 6cmH₂O of PEEP and PEEP group (n = 12) who were ventilated mechanically with PEEP only at maximum level of 10cmH₂O. In IRV group step-wise prolongation of the I:E ratio from 1:1.9 to 2.6:1 or 4:1 was applied as a Pa_{O 2} was improved and in PEEP group also level of PEEP was increased from 0, 5 to 10cmH₂O after one hour period irrespective of Pa_{O 2}. Inversed ratio ventilation and PEEP increased significantly Pa_{O 2}/Fi _{O 2}, the increase being observed 6hrs (I:E = 2:1) and 2hrs (10cmH₂O) after starting IRV or PEEP. Further improvement of oxygenation was not observed in IRV even if I:E ratio was prolonged up to 2.6:1 or 4:1. These results suggested that combinations of IRV with PEEP were effective and an I:E ratio of 2:1 may be optimal, and IRV is advantageous compared to PEEP, but will take more long time to improve oxygenation than PEEP.(Sari A, Toriumi T, Yamashita S, et al.: Combined effects of inversed ratio ventilation (IRV) with positive end-expiratory pressure ventilation (PEEP) on cardiorespiratory function in acute respiratory failure. J Anesth 5: 105–113, 1991)     

Treatment outcomes and mortality of 94 patients with acromegaly

Summary Background. Due to new therapeutic modalities and modified therapeutic goals outcome of patients with acromegaly may change over time and differ by centre. We analysed treatment outcomes and mortality of our patients with acromegaly seen between 1971 and 2003.Method. The cohort consisted of 94 patients who had been followed for 0.3–31 years (mean 10.6 years). Remission criteria were a normalized IGF-I concentration, a nadir GH level during oral glucose load of <1.0µg/l and a random GH value of <2.5µg/l.Findings. Transsphenoidal surgery achieved remission in 80% of patients with micro-adenomas (<1cm), 65% with meso-adenomas (1cm to <2cm) and 27% with macro-adenomas (2cm). Patients with meso-adenomas operated on after 1995 tended to have a better outcome compared to those operated on before 1995 (Remission in 83% vs. 38%). Radiotherapy resulted in disease control in 22 of 47 patients (47%). Intramuscular depot formulation of octreotide (Sandostatin^® LAR^®) led to disease control in 17 of 26 patients (65%). After multimodal therapy persistent acromegalic activity remained in 18% of the patients; only one of them had an adenoma of <2cm. The standardized mortality ratio was 1.30 (95% CI 0.52–2.67) for patients in remission and 1.38 (95% CI 0.51–3.00) for patients with persistent acromegalic activity.Conclusions. Most patients with adenomas of <2cm can be expected to achieve remission by transsphenoidal surgery alone. Furthermore, virtually all patients with adenomas of <2cm and more than 80% of patients with adenomas of 2cm can be expected to achieve remission by adjuvant treatment. Aggressive multimodal therapy is critical in the management of acromegaly reducing mortality risk close to that of the general population.     

Naloxone and flumazenil fail to antagonize the isoflurane-induced suppression of dorsal horn neurons in cats

Effects of naloxone and flumazenil on isoflurane activities were examined on dorsal horn neurons in cats. Isoflurane suppressed bradykinin-induced nociceptive responses in transected feline spinal cords. The bradykinin-induced neuronal firing rates were significantly suppressed by 60.0%, 35.3% and 32.2% at 10, 20 and 30min after isoflurane administration, respectively. The 32.3% suppression on bradykinin-induced neuronal responses at 30min after isoflurane administration was not reversed 5min after administration of naloxone (36.4% suppression). The suppressive effects of isoflurane were not reversed by naloxone (0.2mg·kg^–1, i.v.). Similarly, the benzodiazepine antagonist, flumazenil (0.2mg·kg^–1, i.v.), did not affect the suppressive effects of isoflurane. Failure of naloxone and flumazenil to reverse the suppressive effects of isoflurane suggests that isoflurane interacts with neither opioid nor benzodiazepine receptors in producing its suppressive action on nociceptive responses in dorsal horn neurons of the feline spinal cord.(Okuda T, Wakita K, Tsuchiya N, et al.: Naloxone and flumazenil fail to antagonize the isoflurane-induced suppression of dorsal horn neurons in cats. J Anesth 7: 462–467, 1993)     

Recombinant human-type SOD attenuates circulatory disorders after reperfusion of splanchnic organs in rats

Oxygen free radicals (OFRs) have been reported to play pivotal roles in the pathogenesis of cell damage induced by ischemia and reperfusion. The efficacy of recombinant human superoxide dismutase (rh-SOD) in the treatment of circulatory disorders after reperfusion of the splanchnic area was investigated in rats. All rats died within 3 hours after release of 60-min superior mesenteric artery occlusion (SMAO) when no treatment was given. Animals which received rh-SOD, 2mg·100g^–1BW, at reperfusion followed by a continuous infusion of rh-SOD 0.67mg·100g^–1BW·hr^–1, exhibited prolonged survival times compared with no treatment rats (231 ± 35min and 149 ± 43min, respectively). Mean blood pressure in rats treated with rh-SOD was higher than in controls after reperfusion, and was concomitant with improvement in splanchnic perfusion. The results suggest excessive activity of OFRs in reperfused organs and a possible scavenging effect of rh-SOD as a means of eliminating them.(Bitoh H: Recombinant human-type SOD attenuates circulatory disorders after reperfusion of splanchnic organs in rats. J Anesth 6: 247–254, 1992)     

AneuRx Device Migration: Incidence, Risk Factors, and Consequences

Success after endovascular abdominal aortic aneurysm repair (EVAR) is dependent on device positional stability. The quest for such stability has motivated different endograft designs, and the risk factors entailed remain the subject of debate. This study aims at defining the incidence, risk factors, and clinical implications of device migration after EVAR with the AneuRx® endograft. In this study we included all consecutive 109 patients submitted to primary AneuRx placement for infrarenal aortic or aortoiliac aneurysms. Preoperative computed tomography (CT) scans were reviewed for the following anatomic characteristics: neck length, diameter, angulation, calcification, and thrombus load; and sac diameter and thrombus load. Percentage of device oversizing relative to the proximal neck diameter was determined. All postoperative CT scans were reviewed, and the distance between the lowest renal artery and the craniad end of the device was measured. A 5-mm increase in such distance was considered indicative of device migration. Migration cumulative incidence was estimated by the Kaplan-Meier method, and its association with any of the preoperative anatomical characteristics was tested using Cox proportional hazards models. Median follow-up time was 9 (range, 1-31) months. Migration occurred in nine patients, corresponding to a 15.6% estimated probability of migration at 30 months (SE=5.1%). Migration was associated with the risk of proximal type I endoleak (hazard ratio=3.39, 95% confidence interval=1.46-7.87; p=0.007). This type of endoleak occurred in three of the migration-affected patients (33.3%); all of them were resolved by additional cuff placement at the proximal landing zone. No other migration-related reinterventions were performed. The only significant associations between anatomic factors and device migration probability were the protective effects of longer necks (odds ratio [OR]=0.71 for each additional 5 mm, p=0.045) and longer overlapped portions of neck and device (OR=0.56 for each additional 5 mm, p=0.003). There was a trend toward higher probability of migration among reverse-tapered necks (OR=1.75, p=0.109). Percentage of device oversizing correlated with early neck dilation (between preoperative and first postoperative diameters, correlation coefficient=0.4, p < 0.0001), but not with late neck dilatation (between first postoperative and 1.5-year scan diameters, correlation coefficient=0.29, p=0.112). There was a trend toward higher mean percentage of late dilation among migrators (11.4%, standard error of the mean [SEM] 2.6) than nonmigrators (5.7%, SEM=1) (p=0.08), but both groups had similar mean percentages of early dilation (3%, SEM=1.6%, vs. 5.5%, SEM=0.6%; p=0.365). This result indicates that device migration is not a rare event after AneuRx implantation. This phenomenon is associated with proximal type I endoleaks. Deployment of the endograft immediately below the renal arteries might help to prevent migration, since use of greater lengths of overlapped device relative to the proximal neck has a protective effect. Migration seems to be independent of the degree of device oversizing.Presented at the 29th Annual Meeting of the Peripheral Vascular Surgery Society, Anaheim, CA, June 4-5, Sergio M. Sampaio is a recipient of the Edward S. Rogers Clinical Research Fellowship in Vascular Surgery.     

Blockade of sodium channels by phenytoin protects ultrastructure and attenuates lipid peroxidation in experimental spinal cord injury

Summary Spinal cord injury (SCI) involves a series of pathological events. Abnormal sodium influx has been implicated as one of the key events in the pathophysiology of the SCI. Pharmacological blockade of sodium channels can reduce secondary injury and increase recovery from trauma. The aim of the present study was to show the neuroprotective effect of phenytoin, a sodium channel blocker, after experimental SCI.Control and laminectomy-only groups were not injured. 50g-cm weight drop injury was produced in the trauma group. In the treatment groups, methylprednisolone (30mg/kg) and phenytoin (1mg/kg, 10mg/kg, or 30mg/kg) were given intraperitoneally immediately after injury. Malondialdehyde (MDA) levels in the spinal cord samples were examined for lipid peroxidation. Spinal cord ultrastructure was evaluated and grading system was used for quantitative evaluation.Trauma increased tissue MDA levels. Treatment with methylprednisolone and phenytoin decreased MDA levels compared to trauma in all doses. Significant ultrastructural neuroprotection was observed with 30mg/kg of phenytoin treatment according to general neural score. This ultrastructural neuroprotection of phenytoin was not different from methylprednisolone. Phenytoin appears to protect spinal cord against injury by decreasing lipid peroxidation and lessening neuronal damage associated with SCI in rats.     

Efficacy of landiolol in attenuating hemodynamic responses to local epinephrine infiltration in patients undergoing vaginal total hysterectomy

Purpose Local epinephrine infiltration often causes ₁-adrenoceptor-mediated tachycardia, hypertension, and arrhythmia. Landiolol, a short acting ₁-adrenoceptor blocker, may represent the most ideal agent to attenuate these adverse effects. In this study, we examined the effects of landiolol on the hemodynamic changes resulting from local infiltration of epinephrine.Methods Thirty-six patients undergoing vaginal total hysterectomy under general anesthesia were randomly assigned to one of three groups: control group (n = 12), L5 group (n = 12), and L10 group (n = 12). In the control, L5, and L10 groups, the patients were given saline, landiolol 5mg, and 10mg, respectively, just before infiltration of epinephrine(1:300000; total dose, about 100µg) into the surgical field. Blood pressure and heart rate was assessed before and 5, 10, 15, 20, 25, 30min after the initiation of epinephrine infiltration. If systolic blood pressure and heart rate exceeded 160mmHg and 120 beats·min^–1, respectively, Ca blockers of either diltiazem 5mg or nicardipine 1mg and/or 2% sevoflurane were given.Results Epinephrine infiltration significantly increased systolic blood pressure from 122 ± 15 to 170 ± 29mmHg and heart rate from 63 ± 8 to 106 ± 10 beats·min^–1. In both the L5 and L10 groups, the increase in heart rate (from 69 ± 16 to 87 ± 16 beats·min^–1, P < 0.01, and from 70 ± 18 to 76 ± 9 beats·min^–1, P < 0.01, respectively) was significantly smaller compared to the control group, but the increase in systolic blood pressure was significantly attenuated in the L10 group (from 116 ± 18 to 140 ± 27mmHg, P < 0.01). The number of patients given either Ca blockers or sevoflurane in the control group was significantly higher than that in the landiolol groups (P < 0.01).Conclusion The present study suggests that landiolol 10mg may be a more suitable dose than landiolol 5mg to antagonize hyperdynamic states induced by local administration of epinephrine.