J Trauma
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The pin-bone interface is the weakest link in the mechanical stability of external skeletal fixation. In this investigation, a canine model was used to characterize the nature of cortical bone reactions at the pin-bone interface. Unilateral external fixators were applied to the tibiae of 61 dogs using six tapered cortical half-pins. ⋯ In inherently unstable oblique osteotomies, and less in stable rigidly fixed transverse osteotomies, immediate postoperative weight bearing caused bone thread resorption and adverse cortical bone remodeling at the entry cortex of external fixation half-pins. The unicortical loosening of half-pins that became evident during the first month of fixation obviously represents a consequence of micromotion and local bone yielding failure caused by high dynamic stresses of the pin-bone interface. Effective precautions should be taken to reduce such stresses.
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Prolonged hemorrhagic shock is characterized by the progression from hyperglycemia to hypoglycemia and failure to respond to standard methods of resuscitation. Previous studies have shown that the transition to irreversible shock is accompanied by attenuation of hepatic gluconeogenic capacity and a rising level of intracellular calcium. Additionally, it has been observed that diltiazem improves survival following prolonged hemorrhagic shock in rats. ⋯ In group A, hepatic glucose production was significantly elevated in DZ animals when compared with controls (p < 0.05). A similar significant improvement in gluconeogenesis was observed following 120 minutes of hemorrhagic shock in group B (p < 0.05). Additionally, treated rats (DZ, both groups A and B) demonstrated improved gluconeogenic response to substrate when compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)
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Cerebral blood flow (CBF) varies unpredictably in patients after head injury and hemorrhagic shock. Proper treatment requires knowledge of ischemic versus hyperemic flow. The degree to which the size or severity of the injury may contribute to CBF abnormalities is unknown. ⋯ In the small lesion group traumatic brain injury, followed by shock and resuscitation, produced a significant and sustained elevation in bihemispheric regional CBF and cerebral oxygen delivery that was significantly greater than that observed in either the large lesion group or the controls (p < 0.05). There were no significant differences between the experimental groups in volume of hemorrhage, intracranial pressure, cerebral perfusion pressure, arterial oxygen content, or PaCO2. These data suggest that the volume of injured tissue may determine post-resuscitation CBF, and that interventions to reduce cerebral blood volume (i.e., hyperventilation) may not be universally applicable in all head injured patients.