Search

Ten exclusively gastrostomy-fed, neurologically impaired children (4.5-14.5 years old) with gastroesophageal reflux were randomly assigned to receive feedings with either a casein- or a whey-based formula for 48 h each and then crossed over to the other formula. One 24-h pH probe study each was performed while being fed casein- and whey-based formula, respectively. There was a significant reduction in episodes and duration of gastroesophageal reflux while consuming the whey-based formula (p < 0.05). Whey-based feedings should be considered an additional tool in conjunction with other antireflux measures to treat gastroesophageal reflux more effectively in children with severe neurological impairment. A similar study was also conducted involving 14 infants (3-12 months old) with documented gastroesophageal reflux using 24-h pH probe monitoring while consuming a casein-based formula. The formula was changed to a whey-based formula and the pH probe study repeated within 3-5 days. Four infants showed improvement and the rest showed either deterioration (1/14) or comparable results (9/14). The reduction in the mean number of episodes or duration of gastroesophageal reflux with the whey-formula was not significantly different from that with the casein-based formula (p > 0.05). Based on these findings, generalized recommendations for the use of whey-based formula in infants with gastroesophageal reflux cannot be made.

The relationship between maximal velocity and load was studied in nine muscles of the cat's hind limb using a technique in which the initial and final muscle lengths are determined by equilibrium of a suspended mass and the muscle's passive and active forces elicited by tetanic stimulation. The maximal velocities of shortening during contraction under each of various loads was used to fit a Hill model using the least-squares method. It was shown that different muscles varied significantly in their ability to generate maximal velocity over a range of loads. The tibialis anterior muscle generate the highest velocity (28.4 cms-1), whereas the tibialis posterior generated the lowest maximal velocity (4.2 cms-1). In general, muscles with predominantly fast twitch fibres and with the largest elongation/shortening range displaced the load at the highest velocities, as compared with muscles with predominantly slow twitch and short excursion range which respond with low velocities. The a/P0 ratio of Hill's equation, which defines the curvature of the force velocity, also varied widely, being most monotonic (0.927) for the soleus and the steepest (0.067) for the extensor digitorum longus, further suggesting that fibre composition is also highly influential on the force-velocity relations of the muscle.

A predictive model of muscle force-velocity relationships is presented based on functional architectural variables. The parameters of Hill's equation describing muscle force-velocity relationship of nine muscles were estimated by their relationships with variables extracted from the whole-muscle length-force relationship and the percentage of slow-twitch fibres. Specifically, the maximal unloaded velocity (Vo) was estimated through multiple linear regression, from each muscle's fibre composition and the shortening range through which each muscle could produce active force. The maximal isometric force (Po) was also extracted from each muscle's length-force relationship. The ratio of Hill's dynamic constanta to Po and b to Vo, which determines the degree of curvature of the relation, was determined solely by the percent of slow-twitch fibres. This model was verified by fitting it to experimental force-velocity curves of nine different muscles in the cat's hindlimb. It was found that reasonable fits of force-velocity curves would be obtained with correlation coefficient in the range of 0.61 to 0.92, with an average of 0.82. The model predicted that muscles with relatively long shortening ranges would achieve higher maximal velocity, and that muscles with higher percentage of slow-twitch fibres had less pronounced curvature and lower maximal velocity in their force-velocity relationships. RELEVANCE: The results have direct implications in the design of neuroprosthetic limb control systems, which use electrical stimulation to restore function to muscles paralysed from spinal cord injury. The designer is enabled to optimally calibrate the controller according to the predicted individual force-velocity curves of different muscles by using the length-tension curves and fibre composition data available in the literature.

The length-tension relations of two bicompartmental muscles, including parallel and pennated fibers, were experimentally determined for isometric and load moving contractions. Comparison of the isometric and constant mass load length-tension curves obtained from the same preparations demonstrated significant reductions in force, a shift of the optimal length and increased elongation range for shortening contractions under constant mass load. Pennated muscle demonstrated a larger reduction in force and greater shift in the optimal length relative to the changes in a muscle with parallel fibers. A bicompartmental model was fitted to the experimental data to provide quantitative insight to the changes described above, and for use in mathematical models of other bicompartmental muscles, and for design of optimal electrical stimulation system for restoration of function in spinal cord injury patients.

An anterior approach to the spine via a thoracoabdominal incision offers the surgeon many advantages. The major vascular structures are visualized, stabilization of a long segment of the spine is strong, and recovery is speedy. Nevertheless, this is a major operation and one with potential morbidity and mortality. At Children's Hospital of New Orleans, the Pediatric Surgery and Pediatric Orthopedic Surgery Services work together to reduce these risks and in so doing maintain an acceptable morbidity. With this two-team approach; we operated on the spines of 39 patients between 1978 and 1988. The most common indications for operation included idiopathic scoliosis, neuromuscular disease, and congenital abnormalities. A thoracoabdominal approach was used in 32 patients, a thoracic approach in four patients, and an abdominal approach in three patients. Twenty-nine patients experienced 65 complications; 45 of these complications were respiratory in nature. There were no postoperative deaths. Factors unrelated to the incidence of postoperative complications included age, volume of crystalloid infused during operation, volume of blood replacement, and length of anesthesia.

A retrospective study of the initial lateral cervical spine radiographs (read as normal) of five multiply traumatized quadriplegic children showed a subtle widening between the spinous processes of C1 and C2. To verify the accuracy of this widening, five distances, two calculations, and four angles were defined and measured in the pathologic group and in a control group of 12 normal children. There was a significant difference (p less than 0.05) between the two groups. A widening of greater than 10 mm between the spinous processes of C1-C2 on a neutral lateral radiograph should alert the physician to an underlying spinal cord injury. The other measurements could then confine the pathology at that level.