Mathematical modeling to define optimum operating room staffing needs for trauma centers.

BACKGROUND: Level II trauma centers may be verified (1999, American College of Surgeons Committee on Trauma) with an on-call operating room team if the performance-improvement program shows no adverse outcomes. Using queuing and simulation methodology, this study attempted to add a volume guideline. STUDY DESIGN: Data from 72 previously verified trauma centers identified multiple demographic factors, including specific information about the first trauma-related operation that was done between 11:00 PM and 7:00 AM each month for 12 consecutive months. RESULTS: The annual admissions averaged 1,477 for 37 Level I trauma centers, 802 for 28 Level II trauma centers, 481 for 4 Level III trauma centers, and 731 for 3 pediatric trauma centers. The annual admissions correlated with the number of operations done between 11:00 PM and 7:00 AM (p < 0.001). These 946 operations were performed by general surgery (39%), neurosurgery (8%), orthopaedic surgery (33%), another specialty (9%), or multiple services (10%). Admission to operation time was within 30 minutes for 12.1% of patients (2.6% for blunt and 24.1% for penetrating injuries). The probability of operation within 30 minutes of arrival varied with the number of admissions and with the percentage of penetrating versus blunt injuries. The likely number of operations from 11:00 PM to 7:00 AM would be 19 for 500 annual admissions, 26 for 750 annual admissions, and 34 for 1,000 annual admissions, with 5.83, 7.98, and 10.13 patients, respectively, going to operation within 30 min. The probability that two rooms would be occupied simultaneously was 0.14 and 0.24 for centers admitting 500 and 1,000 patients, respectively. CONCLUSIONS: Trauma centers performing fewer than six operations between 11:00 PM and 7:00 AM per year could conserve resources by using an immediately available on-call team, with responses monitored by the performance-improvement program.

Effects of physiologic albumin and hespan levels on hepatocytes in vitro.

BACKGROUND: Although albumin and hydroxyethyl starch (HES) are routinely used in critically ill, hypoalbuminemic patients, no studies have tested the effect of supplemental albumin and HES on hepatocyte function. METHODS: In this study, the effects of these agents were evaluated by using stable, rat hepatocyte cultures in a collagen sandwich configuration. Hepatocyte synthesis of albumin, urea, and intracellular triglycerides was monitored in Dulbecco's modified Eagle medium (supplemented with fetal bovine serum, hydrocortisone, L-proline, gentamycin, and insulin) without supplemental colloid (control cultures) and with supplemental 2% bovine serum albumin (BSA), 4% BSA, 2% HES, or 4% HES. RESULTS: The albumin secretion in control cultures rose from 31.03 microg/day per 10(6) cells on day 3 to 154.17 microg/day per 10(6) cells by day 12 and remained constant. In contrast, the level of albumin synthesis in the 2% and 4% BSA groups rose from significantly higher initial values (p < 0.05) of 71.25 microg/day per 10(6) cells and 73.27 microg/day per 10(6) cells, respectively, to 127.61 microg/day per 10(6) cells and 107.95 microg/day per 10(6) cells by day 7, then declined rapidly to 58.98 microg/day per 10(6) cells and 41.28 microg/day per 10(6) cells by day 12 when cell disruption was present. HES also reduced albumin synthesis. The urea genesis in the control groups and in the treatment groups was found to be comparable throughout the study. The BSA supplemented groups accumulated large amounts of intracellular lipid droplets during the experiment. The intracellular triglycerides analysis found the 4% BSA group to be significantly (p < 0.05) higher than the 4% HES. CONCLUSION: BSA, added to a collagen sandwich hepatocyte preparation, causes reduced hepatocyte synthesis by day 8, probably a result of intracellular triglyceride accumulation, whereas HES reduces synthesis through unidentified mechanisms.

Inhibition of alpha-smooth muscle actin expression in an in vitro wound healing model by certain antibiotics.

OBJECTIVE: This study assesses the effects of antimicrobials on wound healing in an in vitro model of chicken flexor tendons in a collagen gel matrix. Two equidistant tendons were bathed in a culture medium for 28 days as fibroblasts (fb) grew from the tendon ends into the collagen gel and migrated toward each other until gap closure. Five groups of 10 paired tendons each included the control and the study groups, which received oxacillin (Ox), clindamycin (Cl), chloramphenicol (Chl), or tetracycline (Tet) in the culture medium to assess their effects on gap closure rate, fb migration, and myofibroblast alpha-smooth muscle (alpha-SM) actin expression. RESULTS: Gap closure, by day 27, was 98.5% in the controls compared with 97%, 92%, 89.5%, 21.75% in the Tet, Cl, Ox, and Chl groups. Chl retarded gap closure (p < 0.05). Fb migration was similar for all groups. In the control and Ox groups, myofibroblast expressed actin at day 5. By day 7, fb cells were clearly visible in the control, Ox, and Cl groups, whereas, only light actin was present in the Chl and Tet groups. Actin band densities for the Cl, Ox, Tet, and Chl groups were 78.4%, 62.5%, 61.7% and 26.1%, respectively, of the control group. CONCLUSION: These studies suggest that one reason certain antimicrobials impair wound healing, is due to myofibroblast inhibition of alpha-SM actin.