Use of Vicryl (polyglactin 910) mesh to limit epidural scar formation after laminectomy

A variety of substances have been used at laminectomy sites to prevent postoperative epidural scarring. Free grafts of autologous subcutaneous fat are commonly used both clinically and experimentally. The free fat grafts usually survive, but decrease in size by about 50%. Postoperatively, subcutaneous seroma has been observed with the use of fat grafts, as well as recurrent symptoms of neural compression by the graft that required additional operations. When compared to the use of free grafts after laminectomy in dogs, Vicryl mesh produced slightly more scarring, but consistently less than that observed in control animals. The Vicryl mesh was resorbed by a minimal chronic inflammatory response over about 45 days. Seven of 11 fat-grafted zones showed signs of necrosis, at times with a greater collection of inflammatory cells than that associated with the Vicryl mesh. Of the 4 fat-grafted zones that showed good survival, 2 had gross evidence of neural compression. No surgical zone treated with Vicryl mesh exhibited evidence of neural compression. In view of these results, the use of Vicryl mesh at laminectomy sites may be a safer method of limiting postoperative epidural scar formation.     

Prevention of precipitation of phenytoin in an infusion fluid by hydroxypropyl β-cyclodextrin

Injection of phenytoin is often diluted with infusion fluids before administration, which may lead to precipitation of the drug due to changes in pH and/or vehicle. It is not possible to add cyclodextrins to the original injections to prevent precipitation of the drug, because the quantities required would be impractical (>100% w/v). However, from a knowledge of the solubility of phenytoin in cyclodextrin solutions, it is possible to add sufficient amounts of a soluble cyclodextrin to infusion fluids to maintain the solubility of phenytoin after the original injection is diluted to clinical concentrations in the fluid. From solubility measurements, theoretical amounts of hydroxypropyl β-cyclodextrin (HPCD), sufficient to prevent precipitation of phenytoin, were added to 0·9% w/v sodium chloride solution, adjusted to pH 7·0. Phenytoin injection was diluted to clinical concentrations in the cyclodextrin/NaCl solutions. The mixtures, together with analogous mixtures containing phenytoin, but no HPCD, were stored at 25 °C for 3 days. In the presence of the cyclodextrin no precipitates of phenytoin were observed, but in its absence an immediate massive precipitation of phenytoin occurred. This is a flexible method for using soluble cyclodextrins to prevent precipitates of drugs in infusion fluids, provided the cyclodextrin used is not toxic.     

Effect of age and diet on glucose tolerance in Sprague-Dawley rats

Male Sprague-Dawley rats ages 12 and 27 mo were used to evaluate intravenous glucose tolerance. Rats were fed ad libitum a purified diet containing either 33% sucrose and 33% starch or 66% starch, 17.5% casein and 7% fat (g/100 g) for 4 mo. Each animal was fitted with a cannula in the left carotid artery while anesthetized with methoxyflurane and was allowed to recover without food for 10-12 h. A resting blood sample was withdrawn, and then each rat received 1 mL of 50% glucose in saline per kilogram body weight throughout the carotid cannula. The cannula was washed with the rat's blood to remove any excess glucose, and blood samples were taken at 5, 10, 15, 30, 45 and 60 min after infusion. The 12-mo-old rats in both the high sucrose and sucrose-free diet groups had significantly greater resting plasma glucose and insulin concentrations than did their 27-mo-old counterparts. Diet had no effect on resting glucose or insulin levels. Neither age nor diet had a significant effect on plasma glucose or insulin concentrations following the glucose infusion. These data suggest that the pancreatic response to a glucose load is not altered by age or high sucrose diets.