Fermentor temperature as a tool for control of high-density perfusion cultures of mammalian cells

Temperature is a key environmental variable whose potential in animal cell fermentor optimization is not yet fully utilized. The scarce literature data suggests that reduced fermentor temperature results in an improved viability and shear resistance, higher cell density and titer in batch cultures, and reduction in glucose/lactate metabolism. Due to the arrest of the cells in the G1 phase, the specific growth rate was found to decrease at temperatures below 37.0 degrees C. The response of the specific production rate was cell line dependent: in some cases it increased 2-to-3-fold, but decreased in other cases. The controlable slowdown of cell metabolism at lower temperature can be used in optimization of perfusion mammalian cell cultures with several potential advantages, including higher cell density in oxygen limited reactors, lower perfusion rate, improved product quality, simplified pH control, and others. To evaluate this strategy, a series of long-term experiments in 15 L perfusion bioreactors culturing recombinant hamster cells at 20.0 x 10(6) cells/mL were conducted. The temperature was changed over a range of set points, and maintained at each of these for a long period of time. Steady state process data was collected and analyzed. The effect of temperature on the following characteristics of the perfusion process was studied: cell growth, glucose/lactate metabolism, glutamine/ammonia metabolism, cell respiration, cell density at constant oxygen transfer rate, proteolytic activity, and product quality (glycosylation and molecule fragmentation). The results suggest that temperature is a variable with a significant potential in optimization of perfusion cultures. Properly selected temperature set point will contribute to the overall improvement of process performance. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 328-338, 1997.

Long-term results of lower-extremity venous injuries

OBJECTIVES

To compare the long-term venous function of ligated, simple, and complex repairs and to assess long-term patency in repaired veins.

DESIGN

A cohort study of patients with lower-extremity venous injuries treated during a 7-year period.

SETTING

A level I urban trauma center.

PATIENTS

Twenty-one of the 79 patients with a history of lower-extremity venous injury identified via the trauma registry consented to outpatient evaluation.

INTERVENTION

Participating patients underwent a through vascular examination that included color flow duplex venous imaging and air plethysmographic assessment.

MAIN OUTCOME MEASURES

The patency of venous repairs, the incidence of chronic deep venous thrombosis, and evidence of chronic venous insufficiency.

RESULTS

The venous injuries included 5 iliac, 10 femoral, and 6 popliteal. Six of these injuries were ligated, 11 injuries were simply repaired (lateral venorrhaphy or end-to-end), and 4 were repaired with complex interposition grafts. All repairs were patent, with no evidence of deep venous thrombosis by color flow duplex venous imaging. Seventeen of the 21 patients had symptoms, color flow duplex venous imaging findings, and air plethysmographic data consistent with chronic venous insufficiency, including significant mean differences (P < .03) in outflow fraction, outflow fraction with compression, venous filling index, and residual volume fraction, when compared with the uninjured extremity. The most profound changes followed complex repairs and perioperative fasciotomies.

CONCLUSIONS

While the long-term patency of venous repairs is excellent, most patients demonstrate evidence of chronic venous insufficiency after either ligation or repair. Complex venous repairs and fasciotomy are associated with the most severe functional changes.

Use of low molecular weight heparin in preventing thromboembolism in trauma patients

OBJECTIVE

To investigate the safety and effectiveness of low molecular weight heparin (LMWH) in preventing deep venous thrombosis (DVT) in high-risk trauma patients, compared with mechanical methods of prophylaxis.

DESIGN

A prospective randomized trial conducted over a 19-month period in an urban, academic trauma center.

METHODS

All trauma patients with the following risk factors for the development of DVT were considered for enrollment in this study: any injury with an Abbreviated Injury Scale score > or = 3; major head injury (Glasgow Coma Scale score < or = 8); spine, pelvic, or lower extremity fractures; acute venous injury; or age > 50 years. After a screening venous duplex examination, the patients were assigned to a Heparin versus No-Heparin group, depending upon the presence of injuries precluding the use of heparin. In the Heparin group, the patients were then randomized to receive either LMWH or optimal mechanical compression (defined as bilateral sequential gradient pneumatic compression (SCD) or, in the presence of lower extremity injuries precluding the use of the SCD, the arteriovenous impulse (AVI) compression system). All the patients in the No-Heparin group received optimal compression. Enrolled patients underwent sequential duplex examinations every 5 to 7 days until discharge.

RESULTS

Of the 487 consecutive patients initially enrolled in this study, 372 were available for at least the first two duplex examinations and comprise the study population. Only nine (2.4%) patients developed DVT, compared with the predicted 9.1% rate in high-risk trauma patients receiving no prophylaxis (p = 0.037). Of the 120 patients who were randomized to receive LMWH, only one (0.8%) developed DVT. In the SCD group, there were 5 of 199 patients (2.5%) with DVT, and 3 of 53 (5.7%) in the AVI group. One patient with DVT also had clinical symptoms of pulmonary embolism, but there were no deaths secondary to pulmonary embolism. There was one major bleeding complication potentially associated with the use of LMWH.

CONCLUSIONS

The administration of LMWH is a safe and extremely effective method of preventing DVT in high-risk trauma patients. When heparin is contraindicated, aggressive attempts at mechanical compression are warranted.

Total abdominal colectomy for control of massive lower gastrointestinal bleeding

From 1957-1990 four patients underwent total abdominal colectomy with primary ileoproctostomy for control of massive lower gastrointestinal hemorrhage at Field Memorial Community Hospital in the rural community of Centreville, Mississippi. Surgery was performed emergently in two cases, and urgent/electively in the two remaining cases. Bleeding was controlled in each case. Upper Gastrointestinal and rectal bleeding were excluded, but further attempts to localize bleeding were not performed due to the difficulty of obtaining these studies at our hospital and the questionable likelihood of localizing the bleeding site. Many authors recommend an aggressive diagnostic workup including radio-labeled RBC scintigraphy and mesenteric angiography to localize colonic bleeding. Their aim is to perform a directed colonic resection for control of bleeding. However, most authors support total abdominal colectomy in cases where 1) hemodynamic instability does not allow extensive preoperative evaluation 2) there is a recurrent bleeding 3) more than one site is visualized as bleeding 4) there is widespread diverticulosis in a good-risk patient or 5) diagnostic procedures are unavailable. The low morbidity and good bowel function achieved following total abdominal colectomy, combined with the unavailability of diagnostic radiographic studies leads us to recommend total abdominal colectomy for control of massive lower gastrointestinal bleeding. The mortality of the procedure can be minimized by operating in a timely manner, prior to 10 units transfusion or 4 units within 24 hours, or operating in cases of recurrent bleeding.