The effect of continuous epidural infusion of ropivacaine (0.1%, 0.2% and 0.3%) on nerve conduction velocity and postural control in volunteers.

BACKGROUND: Continuous epidural infusions of local anaesthetics have become increasingly popular in postoperative pain treatment, especially as they permit early mobilisation. Ropivacaine is a promising new agent which induces more pronounced sensory than motor blockade. This study was focused on the influence of continuous epidural infusion of ropivacaine on impulse conduction in large nerves (by measurement of F and H latencies), and on the subjects' ability to maintain postural control during mobilisation. METHODS: Healthy male volunteers received 0.1%, 0.2% or 0.3% ropivacaine, and bupivacaine 0.25% was used as reference. A bolus epidural injection of 10 ml of the drug, at L2/3 level, was followed by continuous infusion at 10 ml/h for 21 h. Motor blockade was assessed by mechanical measurements of force during big toe flexion and by recording of F latency. Sensory blockade was monitored by pin-prick and Thermotest methods, and by H latency recording. The subjects' ability to perform a postural test was evaluated by posturography. RESULTS: The F and H latencies became prolonged/abolished dose-dependently. With ropivacaine, F latency recovered significantly later than motor function (P = 0.0002), and H latency recovered later than normal pin-prick perception (P = 0.0006). However, the duration of partial blockade of thermoperception was comparable to that of H latency prolongation. Posturographically, the subjects receiving 0.1% ropivacaine differed significantly from all others (P < 0.001) in that they were able to maintain postural control during the infusion. The recovery period after termination of infusion was significantly shorter with ropivacaine than with bupivacaine for all measured variables. CONCLUSION: Recovery of postural control with 0.2% and 0.3% ropivacaine is significantly faster than with bupivacaine 0.25%. H latency recording allows detection of epidural blockade intensity that does not prevent subjects from performing postural tests.

Postural compensation in children with congenital or early acquired bilateral vestibular loss.

The relative roles of different receptor systems in compensating for vestibular loss were studied in 18 children (12 to 16 years of age) with congenital or early acquired bilateral vestibular loss (BVL) and impaired hearing, and compared to that in 33 normal children (9 to 16 years of age). Postural stability was studied with posturography evaluating the velocity of anterior-posterior body sway. With closed eyes the increase of sway velocity did not differ between the groups, either with or without simultaneous proprioceptive disturbances when the subjects were standing on a bare surface. Body sway velocities were found to increase more in subjects with a BVL than in normal children when subjects were standing on foam rubber. When proprioceptive cues were disturbed, body sway velocities increased in both groups, but significantly more in children with BVL when subjects stood on foam rubber. This occurred both with and without open eyes.

Effect of proprioceptor stimulation on postural stability in patients with peripheral or central vestibular lesion.

Body sway in upright stance at rest and after inducing proprioceptor stimulation, elicited by vibration applied to the calf or neck muscles, was studied in 11 patients with peripheral lesion and in 17 patients with central vestibular lesion. The responses were compared with those of 20 normal subjects. Vibratory stimulus was applied at five different frequencies, ranging from 32 to 150 Hz, and at a constant amplitude of 2.1 mm. Postural stability was measured with a force platform in terms of average deviation of body position (ADBP) analyzed in relation to the individual maximum support distance in the anterio-posterior direction. In patients with peripheral vestibular lesion ADBP was moderately increased, compared to normal subjects, when the calf muscles were exposed to vibration under eyes closed conditions (i.e. no visual information available); stimulation of neck muscles both under eyes open and eyes closed conditions and stimulation of calf muscles with open eyes produced an ADBP of the same magnitude as in controls. In patients with central vestibular lesion, proprioceptor stimulation of calf and neck muscles caused increased ADBP whether with eyes open or closed. The ADBP induced by stimulation of neck muscles was significantly greater in patients with a central lesion than in those with a peripheral vestibular lesion. The results indicate that patients with peripheral lesion differ from those with central vestibular lesion in their reaction to proprioceptor stimulus; and that in patients with central vestibular lesion proprioceptor stimulation of the neck muscles produces disproportionately powerful cervico-collic reflexes.

Significance of pressor input from the human feet in lateral postural control. The effect of hypothermia on galvanically induced body-sway.

The significance to human postural control of pressor information from the feet was investigated during vestibular disturbance in seven normal subjects who were exposed to bipolar biaural galvanic stimulation of the vestibular nerves before and after their feet were anaesthetized with hypothermia. The increase in body sway in the lateral plane induced by the galvanic stimulus was enhanced when the feet were anaesthetized, and adaptation of postural control to the galvanic stimulus was delayed. It is concluded that pressor information from the feet contributes significantly to postural control in humans and is important in compensating for vestibular disturbance.

Significance of pressor input from the human feet in anterior-posterior postural control. The effect of hypothermia on vibration-induced body-sway.

The importance to postural control of the mechanoreceptors of the soles was investigated in thirteen healthy subjects. Body-sway velocity was evaluated before and after exposing the subject's feet to hypothermia, and when calf muscles were exposed to vibration at frequencies between 20 and 100 Hz. Subjects were tested both with eyes open and closed. Body-sway velocity was found to increase significantly during hypothermia of the feet. The difference in body-sway between hypothermal and normothermal conditions was less prominent when the subject's eyes were open though the difference was significant in both cases. The present results indicate the importance of the mechanoreceptors of the soles to postural control and elucidate their interaction with compensatory visual input in maintaining postural control. These findings also suggest, that factors affecting pressor input should be taken into consideration when assessing patients with complaints of dysequilibrium.

The effect of omeprazole or ranitidine treatment on 24-hour esophageal acidity in patients with reflux esophagitis.

Twenty-two consecutive patients with gastroesophageal reflux and erosive or ulcerative esophagitis entered a double-blind, randomized study comparing the effect of 20 mg omeprazole once daily with that of 150 mg ranitidine twice daily on esophageal acidity. Ambulatory 24-h esophageal pH measurements were performed within 1 month before inclusion and after 3 weeks of medication. Omeprazole significantly (p less than 0.05) reduced the number of reflux (pH less than 4) episodes, the number of refluxes lasting greater than 5 min, and the total reflux time. In contrast, ranitidine significantly reduced only the total reflux time. When the two treatment groups were compared, a significant difference in favor of omeprazole was found for daytime and total reflux values, except for the longest reflux and the number of reflux episodes lasting greater than 5 min. Substantial differences, also in favor of omeprazole, were found with regard to the effect on endoscopic healing of the esophagitis.

Clinical aspects of eye tracking test.

The eye tracking test is today a well established part of clinical otoneurological examination. In the present paper some applications of the test in evaluating of the level of lesion within the vestibular system are reviewed.

Clinical considerations concerning horizontal optokinetic nystagmus.

During recent decades a vast amount of literature concerning horizontal optokinetic nystagmus has emerged, regarding which--and especially as regards our own work--this report is intended to consider the clinical value of optokinetic nystagmus.

Presentation of a posturographic test with loading of the proprioceptive system.

Postural control is maintained by sensory feedback from visual, vestibular and somatosensory receptors. Recently several methods for evaluating postural control have been devised, utilizing an imposed perturbation. Most of these methods use stimuli which simultaneously affect more than one of the sensory feedback loops. In the present paper a posturographic technique is presented with specific loading of the proprioceptive system, using a computer controlled vibratory stimulus and computerized analysis of the results.

Pharmacological treatment of vertigo.

A review of the treatment of vestibular disorders with drugs is presented. In animal experiments, administration of certain drugs, e.g. alcohol, barbiturates and chlorpromazine, retards the vestibular compensation, while others, e.g. caffeine, amphetamine and ACTH, accelerate the compensation. In compensated animals, some drugs produce overcompensation and some decompensation. A double-blind, randomized trial of the effect of scopolamine and dimenhydrinate in patients with vertigo of varying origin showed, as compared with placebo, that these drugs did not significantly alleviate the vestibular imbalance. The reason for the poor efficacy of the treatment may have been overcompensation of vestibular function loss and adverse effects caused by the drugs. Care should be taken that the drugs used do not retard the vestibular compensation caused by the central nervous system.

Aspects on the lateral fistulae and cysts of the neck.

The usual opinion in the literature is that lateral neck fistulae originate from branchial arch remnants. According to current theories, lateral cervical cysts may either develop from the branchial apparatus or have other etiology. To examine this an investigation was carried out among the relatives of patients with complete fistulae, and 36 per cent fistulae were found among the kin. For lateral neck cysts it was not possible to detect any similar tendency. Histological review of the operation specimens showed that in half of the cases there was seromucus glandular tissue surrounding the fistulae but with regard to the cysts no such tissue was found. This supports the opinion that fistulae and cysts may have a different genesis.

Lateral fistulae and cysts of the neck. Heredity and diagnosis.

A family with congenital fistulae from the second cleft or pouch over four generations is described. In order to obtain some idea of how often anomalies are found in relatives of patients with this type of malformation a material embracing 114 patients has been examined. The investigation demonstrates that patients with a complete lateral fistula of the neck from the second cleft or pouch showed a heredity of 35%, whilst patients with lateral neck cysts did not show any recognizable familial tendency. Views on differential diagnosis are presented, including the value of fine-needle biopsy, where in 92% of the cases a diagnosis of branchial cysts of the neck was obtained.