ABSTRACT
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.
Subject(s)
Patient Care Team , Spinal Fusion/methods , Adolescent , Adult , Child , Child, Preschool , Evaluation Studies as Topic , Female , Humans , Male , Postoperative Complications/etiology , Reoperation , Respiratory Tract Diseases/etiology , Retrospective StudiesABSTRACT
Pigeons' short-term memory for fixed-ratio requirements was assessed using a delayed symbolic matching-to-sample procedure. Different choices were reinforced after fixed-ratio 10 and fixed-ratio 40 requirements, and delays of 0, 5, or 20 s were sometimes placed between sample ratios and choice. All birds made disproportionate numbers of responses to the small-ratio choice alternative when delays were interposed between ratios and choice, and this bias increased as a function of delay. Preference for the small fixed-ratio alternative was also observed on "no-sample" trials, during which the choice alternatives were presented without a prior sample ratio. This "choose-small" bias is analogous to results obtained by Spetch and Wilkie (1983) with event duration as the discriminative stimulus. The choose-small bias was attenuated when the houselight was turned on during delays, but overall accuracy was not influenced systematically by the houselight manipulation.
Subject(s)
Choice Behavior , Concept Formation , Memory, Short-Term , Time Perception , Animals , Attention , Columbidae , Discrimination Learning , Reinforcement Schedule , Retention, PsychologyABSTRACT
Previous work using variable-interval schedules in the terminal links of concurrent chained schedules suggested that relative choice proportion in the initial links equalled relative rate of reinforcement in the terminal links. With fixed-interval terminal-link schedules, however, matching was not obtained. The present study held pairs of fixed-interval terminal-link schedules in a constant ratio but varied absolute sizes. Relative choice for the smaller terminal-link fixed-interval schedule was a negatively accelerated, increasing function of absolute size of the fixed-interval pairs. Matching was found only with the fixed-interval pair of 5 and 10 sec. When pairs of variable-interval schedules were arranged so that the harmonic mean of the intervals equalled the fixed-interval parameter values, relative choice functions were like those for fixed-interval schedules.
