Ultrasound-guided block of the axillary nerve: a volunteer study of a new method

BACKGROUND

Interscalene brachial plexus block (IBPB) is the gold standard for perioperative pain management in shoulder surgery. However, a more distal technique would be desirable to avoid the side effects and potential serious complications of IBPB. Therefore, the aim of the present study was to develop and describe a new method to perform an ultrasound-guided specific axillary nerve block.

METHODS

After initial investigations, 12 healthy volunteers were included. We performed an in-line ultrasound-guided specific axillary nerve block by injecting 8 ml local anesthetic (lidocaine 20 mg/ml) after placing the tip of a nerve stimulation needle cranial to the posterior circumflex humeral artery in the neurovascular space bordered by the teres minor muscle, the deltoid muscle, the triceps muscle and the shaft of the humerus. Needle placement was aided by simultaneous nerve stimulation. We assessed sensory (pinprick and cold stimulation) and motor (active resistive force) block of the axillary nerve before, 15, 30, 60, 90 and 120 min after performing the block and every 30 min until termination of the block.

RESULTS

All 12 volunteers demonstrated sensory block of the axillary nerve and 10 volunteers demonstrated complete motor block. Even though it was difficult to directly visualize the axillary nerve, the block was easy to perform with easily recognizable ultrasonographic landmarks. Block duration was approximately 120 min.

CONCLUSIONS

We describe a new ultrasound-guided technique to specifically block the axillary nerve. The potential clinical role of this new block remains to be determined.

Biomechanical properties of the anterior urethra of the male rabbitA study using impedance planimetry

OBJECTIVE

To evaluate the anterior urethra of the male rabbit regarding its luminal cross-sectional area (CSA), CSA distensibility, circumferential tension-strain relation, histology and the collagen content of the tissue. material and methods: Nineteen rabbits were examined with impedance planimetry by distending the urethra at the passage from the spongious to the bulbous part and 1 cm proximally in the bulbous part. Four weeks later, eight rabbits underwent a second examination. After the measurements the urethras were processed for either histology or determination of collagen content. The urethras from six additional rabbits served as controls for histology and collagen content.

RESULTS

The CSA and the CSA distensibility were smaller at the distal than the proximal distension site. At both sites the CSA distensibility was high at low luminal pressure loads and decreased with increasing pressure. The circumferential tension-strain plot displayed an exponential relation, with a steeper slope distally than proximally. Repeated biomechanical investigation revealed a significantly increased CSA and a decreased slope of the circumferential tension-strain relation at both distension sites. The biomechanical investigation induced abrasion of the epithelium, extravasation of erythrocytes and separation of the collagen fibres, suggesting oedema of the luminal part of the wall. After 4 weeks the epithelium had changed from transitional to stratified, squamous and often keratinized epithelium and the collagen beneath the epithelium formed a dense network instead of wavy lines as seen in the control urethras. The collagen content was larger at the distal than the proximal distension site. No change in collagen content could be demonstrated between the urethras investigated once or twice with impedance planimetry.

CONCLUSIONS

The non-linear pressure-CSA, pressure-CSA distensibility and circumferential tension-strain relations found at both distension sites demonstrate that the urethra yields readily at low pressures, thus facilitating flow. At higher pressure loads, the tissue becomes less distensible, a property that protects it against over-distension and damage. Impedance planimetry cannot be used to study before-and-after phenomena as the biomechanical investigation changed both the histology and the biomechanical properties of the rabbit urethra.

Fluorophotometric evaluation of ocular barriers and of the vitreous body in the aphakic eye

8 aphakic patients were studied with fluorophotometry and 3-mirror examination of the vitreous body one month after cataract extraction. 4 were extracapsular with posterior chamber pseudophakos (ECCE) and 4 were intracapsular with anterior chamber pseudophakos (ICCE). A mathematical model is used to calculate blood-ocular fluorescein permeability (P) and vitreous diffusion coefficient (D) from fluorophotometric scans. All 30-minutes scans in the ECCE group and 2 in the ICCE showed a profile resembling that in phakic eyes, and P- and D-values were calculated. In the remaining two patients from the ICCE group scans showed rapid filling of the vitreous cavity with fluoroscein and calculations could not be made. Clinical examination showed vitreous detachment in these two eyes whereas the others had a normal vitreous structure evaluated by 3-mirror examination. It is shown that fluorophotometric readings can be made in both intra- and extracapsularly operated eyes. Rapid mixing of the dye in the vitreous cavity is seen in relation to vitreous detachment.

An experimental model for stricture studies in the anterior urethra of the male rabbit

In this study, an animal model was developed for the examination of urethral strictures (US). Through a resectoscope, a resection was made in the urethras of 15 male rabbits. After 30 days, the rabbits were evaluated with urethrography, impedance planimetry and either histology or the determination of collagen content. Fifteen rabbits serving as controls were evaluated in the same way. Three rabbits in the resection group and one in the control group died before evaluation. Urethrography demonstrated a stricture in the remaining 12 animals in the resection group. The urethras of the control animals were all normal. Impedance planimetry confirmed that the luminal cross sectional area (CSA) of the strictures was significantly smaller than the CSA of the corresponding part of the urethra in the control group. No difference in CSA was found 1 cm proximal to the stricture. The strictures consisted of densely woven collagen which sent tongues into the adjacent normal parts of the urethra. No difference in collagen content was found between the two groups either at the stricture site or 1 cm proximally. The described method of producing US in the rabbit model was very consistent with all operated animals developing a stricture. The model might prove valuable in evaluating new methods for the treatment of US.

The effect of the somatostatin analogue lanreotide on the prevention of urethral strictures in a rabbit model

We evaluated the effect of the somatostatin analogue lanreotide on the development of surgically induced experimental strictures in the anterior urethra of the male rabbit. A total of 74 male rabbits were randomly allocated into four groups. Lanreotide was administered to the rabbits in groups 2 and 4 from day 0 to 14. To create a stricture, a resection was made in the urethra of the rabbits in groups 3 and 4 on day 2. On day 30, all rabbits were examined with urethrography, impedance planimetry and either histology or for collagen content. Urethrography and impedance planimetry demonstrated a urethral stricture in all operated animals. No difference was found between the two stricture groups, regardless of lanreotide administration, with respect to luminal cross-sectional area (CSA), circumferential tension-strain relation, histology or collagen content. The CSA of the urethra of the normal controls treated with lanreotide was smaller than the CSA of the normal controls not treated with lanreotide, however, no difference was found in histology or collagen content. Lanreotide had no measurable effect on the development of a surgically induced stricture in the male rabbit anterior urethra, however, lanreotide seems to exert an inhibitory effect on the normal growth of the urethra.

Innervation of congenitally hydronephrotic and normal porcine upper urinary tract

OBJECTIVE

To investigate the intrinsic innervation of the upper urinary tract in congenitally hydronephrotic and normal Goettingen minipigs, using the whole-mount preparation technique.

MATERIALS AND METHODS

Whole-mount preparations of hydronephrotic (two with bilateral ectopic ureters, one with left distal ureteric stenosis) and normal (three) porcine upper urinary tracts were examined by immunohistochemistry with tyrosine hydroxylase (TH) and neurofilament and by histochemical staining with NADPH-diaphorase and acetylcholinesterase. Staining results were evaluated using normal bright-field and confocal laser scanning microscopy.

RESULTS

Neurofilament-, TH-immunoreactive and acetylcholinesterase-positive nerve fibres and neuronal networks were identified in the adventitial, muscle and subepithelial layers of the whole upper urinary tract. An NADPH-diaphorase-positive network was expressed in the subepithelial layer and less densely in the muscle layer. The general distribution of the identified neuronal networks was similar in hydronephrotic and normal upper urinary tracts, but the density of these neuronal networks was less in the former. The most striking observation was the absence or marked reduction of neuronal networks in the stenotic part of the ureter in the pig with left distal ureteric stenosis.

CONCLUSION

Whole-mount preparations provide a method for assessing the three-dimensional topography of neuronal networks in the different layers of the porcine upper urinary tract. Although the macroscopic differences between the hydronephrotic and normal porcine upper urinary tracts were striking, changes in the innervation pattern were less obvious, except in distal ureteric stenosis.

Structural and mechanical remodelling of the common bile duct after obstruction

Biliary obstruction in man, most often caused by cholelithiasis, induces remodelling of the bile ducts. Obstruction-induced structural remodelling of the common bile duct (CBD) has been previously described. The mechanical changes that accompany the structural remodelling, however, have not been studied in detail. The aim of this study is to quantify the structural and mechanical changes in the CBD at different time intervals after acute obstruction. The CBD was ligated in the pig, near the duodenum, and studied after 3 h, 12 h, 2 days, 8 days and 32 days (n=5 in each group). One additional animal in each group was sham-operated. At each scheduled time, the CBD was mechanically tested in vitro with a computer-controlled volume infusion system to study the pressure-volume relationship of the CBD segment. A video camera provided simultaneous measurements of the outer dimensions of the CBD at the various pressures. The diameter and wall thickness of the CBD increased about three-fold in the 32-day group compared to the sham group (P < 0.001). The circumferential stress-strain relationship differed between groups (P < 0.001); it was shifted to the right, indicating softening, in the 3-h, 12-h, and 2-day groups and to the left, indicating stiffening, in the 8-day and 32-day group, compared to the sham group. The longitudinal stress-strain curves were all shifted to the left of the circumferential stress-strain curves (P < 0.05). The collagen area increased during obstruction (P < 0.001) but no correlation between the size of the collagen area and the biomechanical parameters was found. A practical implication of the present study serves as a warning to surgeons. A reduction in the wall stiffness in the first several days of obstruction along with an increased duct diameter and a decreased wall thickness suggest that operative procedures such as suturing, anastomosis and procedures related to ERCP must be performed with special care to avoid damage to the CBD.

Decompression sickness during construction of the Great Belt Tunnel, Denmark

Thirteen cases of decompression sickness (DCS) occurred during the construction of the 8-km long railway tunnel under the Great Belt in Denmark between January 1992 and February 1996. 320 compressed air workers were subjected to 9018 pressure exposures in four tunnel boring machines. Overall DCS incidence was 0.14%. Working pressures ranged between 0.25 bar (1.25 atm abs or 126.3 kPa) and 2.95 bar (3.91 atm abs or 396.3 kPa) and working times ranged between 2 minutes and 339 minutes. During the first 1798 pressure exposures 7 DCS cases occurred using French air decompression tables from 1974. The following 7220 exposures were then decompressed in accordance with the newly issued French air decompression tables of 1992. After changing schedules 6 DCS cases occurred and DCS incidence was reduced to 0.08%. Two of the first seven DCS cases had permanent residual symptoms after recompression treatment. All DCS cases, except one, occurred among the 30% of exposures that imposed the greatest decompression stress. DCS incidence among these exposures was 0.42%.

The direct antiatherogenic effect of estrogen is present, absent, or reversed, depending on the state of the arterial endothelium. A time course study in cholesterol-clamped rabbits

BACKGROUND

This study further investigated the relationship between estrogen, arterial endothelium, and nitric oxide (NO) in cholesterol-clamped rabbits.

METHODS AND RESULTS

Rabbits were ovariectomized, balloon-injured in the thoracic aorta, and grouped to receive cholesterol-enriched chow together with either 17beta-estradiol or vehicle for 1, 2, 4, or 8 weeks. In the undamaged aorta, cholesterol accumulation of the placebo rabbits was significantly increased from week 4 to 8 (P<0.001). This increase was almost completely inhibited by estrogen (P<0.001). In the balloon-injured aorta, the estrogen and placebo rabbits accumulated similar amounts of cholesterol in the reendothelialized areas. In the deendothelialized areas, the estrogen group surprisingly accumulated significantly more cholesterol than the placebo group. This difference was apparent from week 2 and became significant at week 8 (P<0.01). Circulating nitrite/nitrate were significantly increased by estrogen at weeks 1, 2, and 4 but not at week 8. Similarly, in additional experiments, basal NO release was significantly higher in estrogen-treated than in placebo-treated rabbits after 4 (P<0.05) but not after 8 weeks. Stimulated NO release and endothelial NO synthase activity did not differ between groups. Mononuclear-endothelial cell binding was reduced by 50% by estrogen after 4 weeks (P<0.05). This difference, however, was abolished by coadministration of N(G)-nitro-L-arginine methyl ester, an inhibitor of NO production.

CONCLUSIONS

The direct antiatherogenic effect of estrogen was present, absent, or reversed, depending on the state of the arterial endothelium, and preceded by a transient increase in NO production followed by a reduced mononuclear-endothelial cell binding.

Effect of acute and long-term treatment with 17-beta-estradiol on the vasomotor responses in the rat aorta

1. This study sought to evaluate whether the effects of acute and long-term treatment with 17-beta-estradiol on the vasomotor responses in rat aortic rings are mediated through the same mechanism. 2. Ovariectomized rats were treated daily with either 17-beta-estradiol-3-benzoate (100 microg kg(-1)) or vehicle for 1 week. 3. The effect of long-term 17-beta-estradiol treatment on the responses to cumulative doses of phenylephrine, 5-HT, calcium, potassium and 17-beta-estradiol was determined in aortic rings. In the same rings, the effect of acute exposure to 17-beta-estradiol (5 and 10 microM) on the dose response curves for phenylephrine, 5-HT, calcium, potassium and acetylcholine were estimated. The measurements were made in rings with and without intact endothelium. The tone-related basal release of nitric oxide (NO) was measured in rings with intact endothelium. 4. Long-term 17-beta-estradiol treatment reduced the maximum developed contraction to all contracting agents studied. This effect was abolished in endothelium denuded vessels. Acute 17-beta-estradiol treatment also reduced maximal contraction. This effect, however, was independent of the endothelium. 5. Long-term 17-beta-estradiol treatment significantly increased the ability of the rings to dilate in response to acetylcholine whereas acute exposure to 17-beta-estradiol had no effect. The tone-related release of NO was significantly increased after long-term exposure to 17-beta-estradiol. 6. In conclusion, this study indicate that the acute and long-term effects of 17-beta-estradiol in the rat aorta are mediated through different mechanisms. The long-term effect is mediated through the endothelium most likely by increasing NO release. In contrast, the acute effect of 17-beta-estradiol seems to be through an effect on the vascular smooth muscle cells.

Gender gap in aortic cholesterol accumulation in cholesterol-clamped rabbits: role of the endothelium and mononuclear-endothelial cell interaction

BACKGROUND

The purpose of the present study was to investigate plasma lipid-independent mechanisms for the sex difference in the development of atherosclerosis.

METHODS AND RESULTS

In the first experiment, 20 male and 20 female rabbits were balloon-injured in the middle thoracic aorta and maintained at the same plasma cholesterol level of approximately 25 mmol/L by use of individualized cholesterol feeding for 13 weeks. In the undamaged aorta, female rabbits had accumulated less than half the amount of cholesterol found in male rabbits (P<0.05). In the balloon-injured aorta, cholesterol accumulation was 3- to 4-fold higher than in the undamaged aorta, with no difference between groups. When cholesterol accumulation data for the balloon-injured aorta were separately assessed for blue (deendothelialized) and white (reendothelialized) tissue, blue tissue surprisingly revealed a reverse gender gap, ie, a significantly higher accumulation of cholesterol in females than in males (P<0.05). White tissue, which constituted the majority of the balloon-injured area, showed no difference in aortic cholesterol accumulation between groups. In the second experiment, 6 male and 6 female rabbits were fed standard rabbit pellets and 6 male and 6 female rabbits were fed a 0.5% cholesterol-enriched chow for 2 weeks. Mononuclear cell binding was 5-fold higher in aortic segments from hypercholesterolemic than from normocholesterolemic rabbits (P<0. 001). In hypercholesterolemic rabbits, cell binding was significantly lower in female than in male rabbits (P<0.05) and showed higher values in atherosclerosis-prone regions. These differences were not found in normocholesterolemic animals.

CONCLUSIONS

The present results suggest that female atheroprotection is independent of sex differences in plasma cholesterol but vitally dependent on the state of the arterial endothelium and involves mononuclear-endothelial cell adhesion as an early step.

Significant reduction of the antiatherogenic effect of estrogen by long-term inhibition of nitric oxide synthesis in cholesterol-clamped rabbits

The purpose of this study was to investigate whether endothelium-derived nitric oxide (NO) is involved in the plasma lipid-independent antiatherogenic effect of estrogen and levormeloxifene, a partial estrogen receptor agonist. 85 rabbits were ovariectomized and balloon-injured in the middle thoracic aorta. The rabbits were fed a cholesterol-enriched diet supplemented with 17beta-estradiol, levormeloxifene, or placebo, either alone, or together with 160 microg/ml NG-nitro- -arginine methyl ester (-NAME), an NO synthase inhibitor, in their drinking water for 12 wk. Plasma cholesterol was maintained at 25-30 mmol/liter by individualized cholesterol feeding. In the undamaged aorta, the extent of atherosclerosis in the estrogen group was only one-third that in the placebo group. Simultaneous administration of -NAME, however, significantly reduced the antiatherogenic effect of estrogen (P < 0.01). There was no significant difference between the placebo group given -NAME and the group treated with placebo alone. At the previously endothelium-denuded site, estrogen had no effect on atherosclerosis development, whereas -NAME combined with estrogen significantly increased atherogenesis (P < 0.05). The effects of levormeloxifene were almost similar to those of estrogen. Active vascular concentrations of -NAME were demonstrated in an additional study, in which maximal aortic/coronary endothelium-dependent relaxation was significantly inhibited in rabbits given -NAME. Thus, in this study a considerable part of the plasma lipid-independent antiatherogenic effect of estrogen was mediated through its effect on endothelial NO in cholesterol-fed rabbits. The results for levormeloxifene suggest a common mechanism of action for estrogen and partial estrogen receptor agonists on atherogenesis.

Prevention by (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin of both catalepsy and the rises in rat striatal dopamine metabolism caused by haloperidol

1. The influence of (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on haloperidol-induced increases in the dopamine metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 4-hydroxy-3-methoxyphenylacetic acid (HVA), was measured in three microdissected brain regions of the rat following a quantitative assessment of catalepsy. 2. Haloperidol alone (2.66 mumol kg-1, i.p.) caused a robust cataleptic response. Given 30 min after haloperidol, 8-OH-DPAT (76 or 760 nmol kg-1, s.c.) prevented catalepsy in 30% and 100% of rats, respectively. 3. Haloperidol significantly increased the DOPAC (by 2 to 4 fold) and HVA (by 3 to 7 fold) contents of the caudate-putamen, nucleus accumbens and medial prefrontal cortex. Given alone, only the lower dose of 8-OH-DPAT caused a significant biochemical change, a doubling of cortical DOPAC. 4. In the cases where catalepsy was prevented by either dose of 8-OH-DPAT, the haloperidol-induced increases in DOPAC and HVA were consistently lower in the caudate-putamen. This pattern was true for the rise in cortical HVA but only in response to the lower dose of 8-OH-DPAT. In contrast, neither dose of 8-OH-DPAT was able to influence the haloperidol-induced rises in cortical DOPAC. In the nucleus accumbens, 8-OH-DPAT did not affect the haloperidol-induced increases in the dopamine metabolites, irrespective of the dose employed or the resulting behaviour. When catalepsy was not prevented, 8-OH-DPAT did not alter the neurochemical responses to haloperidol in any region. 5. These results suggest that part of the mechanism by which 8-OH-DPAT prevents haloperidol-induced catalepsy is reflected by a reversal of the compensatory increase in meso-striatal and/or meso-cortical dopamine neuronal activity that normally accompanies postsynaptic dopamine receptor blockade with haloperidol.

[Presumed anaphylactic shock after infusion of Lipofundin]

A case of anaphylactic shock in a 45 year old man with Hodgkin's disease following Lipofundin infusion is described. Lipofundin is a soybean oil based preparation for parenteral nutrition. Allergic reactions to lipid infusions are only very seldom described, but it is important to be aware of the possibility of anaphylaxis, as this case-story demonstrates. Allergy to soy-proteins is well-known, whereas soybean oil is not allergenic in soybean-sensitive individuals. Soy-protein, in small quantities, can be detected in soy-oil. A possible connection between the patient's reaction and soy-allergy is discussed.

Localization of gastrointestinal deposition of mercuric chloride studied in vivo

During the last 5 years, the site of gastrointestinal absorption of inorganic mercury has been attempted identified mainly by experiments using perfused intestinal segments in vitro or in situ. The present investigation will discuss the localization of the absorption site for mercuric chloride based on a completely undisturbed in vivo experimental model in mice. As the mice were allowed to eat their normal diet during the experimental period, the present results would independently add to existing knowledge on intestinal absorption sites for inorganic mercury. The mice were given 203Hg labelled mercuric chloride orally, either through stomach tube or in the drinking water, and were killed after various time intervals. Mercury was localized and quantified in various segments of the gastrointestinal tract by gamma-counting. Time course analysis of the segmental deposition of mercury demonstrated that the deposition mainly takes place in the proximal jejunum and suggested that a larger part of the jejunum than previously reported is involved in absorption of mercury. Using this in vivo model, tetraethylthiuram disulfide was demonstrated to increase the intestinal deposition and absorption without changing the site of deposition.