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Unlabelled: Perceptions of the difficulty and outcome of unicompartmental knee arthroplasty revision (rev-UKA) vary. We analyzed differences in the complexity, cost, and survival of rev-UKAs compared with revision TKAs (rev-TKA). One hundred eighty knee arthroplasty revisions (68 rev-UKAs/112 rev-TKAs), defined as a minimum of tibial or femoral component revision, were identified from a community joint registry of 7587 knee implants performed between 1991 and 2005. Four of 68 rev-UKAs (5.9%) were revised a second time, whereas seven of 112 rev-TKAs (6.3%) were rerevised. Rev-TKA was predictably more complex than rev-UKA based on the proxies of operative time, use of modular augmentation and stems, and polyethylene liner thickness. Thirty-nine of 68 rev-UKAs (57%) had no form of augmentation and were revised as primary TKAs. There were more rev-TKAs than rev-UKAs with an implant cost greater than $5200 (42% versus 12%) and hospital charges greater than $33,000 (48% versus 25%). We found no difference in survival between the groups. Although rev-UKAs had less surgical complexity and bone loss at the time of revision compared with rev-TKAs, we were unable to show improved survival of rev-UKAs compared with rev-TKAs. Rev-UKAs were associated with lower implant costs and hospital charges compared with rev-TKAs., Level of Evidence: Level II, prognostic study.

Serotonin (5-HT) plays important regulatory roles in mammalian circadian timekeeping; however, little is known concerning the regulation of serotonergic activity in the circadian clock located in the suprachiasmatic nuclei (SCN). By using in vivo microdialysis to measure 5-HT release we demonstrated that electrical or pharmacological stimulations of the dorsal or median raphe nuclei (DRN and MRN, respectively) can alter basal release of 5-HT in the hamster SCN. There were similar increases in SCN 5-HT release after electrical stimulation of either the MRN or DRN, indicating that both could contribute to the serotonergic activity in the SCN. Systemic pretreatment with the 5-HT antagonist metergoline abolished DRN-induced SCN 5-HT release but had little effect on MRN-induced SCN 5-HT release, suggesting different pathways for these nuclei in regulating 5-HT output in the SCN. Microinjections of the 5-HT1A autoreceptor agonist 8-OH-DPAT or antagonist WAY 100635 into the MRN caused significant inhibition and stimulation of SCN 5-HT release, respectively. Both drugs had substantially less effect in the DRN. These differential drug actions indicate that somatodendritic 5-HT1A autoreceptors on MRN neurons provide the prominent raphe autoregulation of 5-HT output in the SCN. Collectively the current results are evidence that DRN as well as MRN neurons can contribute to the regulation of 5-HT release in the hamster SCN. On the basis of the current observations and those from recent anatomic tracing studies of serotonergic projections to SCN it is hypothesized that DRN input to the SCN could be mediated by a DRN --> MRN --> SCN pathway involving a 5-HT-sensitive multisynaptic interaction between the DRN and MRN neurons.

Serotonin (5-HT) has been strongly implicated in the regulation of the mammalian circadian clock located in the suprachiasmatic nuclei (SCN). However, little is known of the pattern of neuronal 5-HT release in the SCN or of the factors involved in regulating its release. Using in vivo microdialysis, we demonstrated the existence of a daily rhythm in the output of 5-HT in the SCN of freely behaving hamsters. This rhythm was characterized by a sharp increase in release from a nadir during late midday to peak levels at the light/dark transition. Output declined to basal levels throughout the remainder of the night. A similar pattern also was evident under constant darkness, with increased 5-HT output occurring at the onset of subjective night. Locomotor activity induced by exposure to a novel running wheel had a pronounced phase-dependent effect on 5-HT release in the SCN, with stimulation during the light phase and suppression during the late dark phase. Systemic application of the somatodendritic 5-HT1A agonist BMY 7378 had a significantly greater suppressive effect on 5-HT release in the SCN during the late dark phase compared with mid light phase, indicating that a variation in raphe autoreceptor response may underlie the time-dependent effects of wheel running on 5-HT release. Collectively, these results show that the daily rhythm in output of 5-HT in the SCN is generated endogenously, and that behavioral state can strongly influence serotonergic activity in the circadian clock in a phase-dependent manner.

Continuous arteriovenous hemofiltration with or without countercurrent dialysis (CAVH[D]) improved pulmonary gas exchange in eight children with concomitant renal and respiratory failure. Fluid accumulation had increased patient weight to 65.2 +/- 18.4 (SD) kg before therapy. After 48 h of CAVH(D), weight was reduced to 60.3 +/- 15.5 kg (p less than .02). Similarly, PaO2/FIO2 improved from 137 +/- 99 to 207 +/- 83 (p = .009) with PEEP unchanged or decreased. In patients with net negative fluid balance, pulmonary artery wedge pressure decreased (from 21.3 +/- 3.8 to 14.8 +/- 5.4 mm Hg; p less than .05). Colloid osmotic pressure increased (15.2 +/- 4.6 vs. 21.4 +/- 4.7 mm Hg; p less than .001). BUN and serum creatinine were unchanged. Parenteral nutrition infused was 212 +/- 427 ml/day before CAVH(D), and 1928 +/- 567 ml/day during its use (p less than .0001). CAVH(D) in children with multiple organ failure allowed better caloric intake, and led to improvement in pulmonary gas exchange. We speculate that CAVH(D) improves pulmonary gas exchange by removal of body and lung water, or by enhancing clearance of mediators associated with pulmonary dysfunction.