Morphologic and mechanical characteristics of engineered bovine arteries

OBJECTIVE

The ideal small-caliber arterial graft remains elusive despite several decades of intense research. A novel approach to the development of small-caliber arterial prostheses with a biomimetic system for in vitro vessel culture has recently been described. In this study we examined the effects of culture time and tissue culture scaffolding on engineered vessel morphology and function and found that these parameters greatly influence the function of engineered vessels.

METHODS

This report describes the effects of culture time and scaffold type on vessel morphology, cellular differentiation, and vessel mechanical characteristics. Engineered vessels were cultured from bovine aortic smooth muscle cells (SMCs) and endothelial cells that were seeded onto biodegradable polymer scaffolds and cultured under physiologically pulsatile conditions. Engineered vessels were subjected to histologic, ultrastructural, immunocytochemical, and mechanical analyses.

RESULTS

Vessel morphology and mechanical characteristics improved as time in culture increased to 8 weeks. SMCs in the engineered vessel wall were organized into a highly lamellar structure, with cells separated by alternating layers of collagen fibrils. Polymer scaffold remnants were present in vessels cultured for 8 weeks, and SMCs that were in proximity to polymer remnants exhibited a dedifferentiated phenotype.

CONCLUSIONS

These findings aid in the systematic understanding of the effects of in vitro parameters on engineered vessels and will be useful for the translation of vessel culture techniques to human cells for the development of autologous human vascular grafts.

Some vagaries of neonatal lumbar epidural anaesthesia

Regional anaesthesia and analgesia offer unique advantages of reduction in general anaesthesia requirements and the demands on NICU resources while improving the general outcome. We assessed the feasibility of continuous lumbar epidural analgesia in 20 neonates for various major surgical procedures lasting from 60-260 min. The babies were aged 18 h to 34 days. They were born at a gestational age of 31-40 weeks. We had difficulty in passing the epidural catheter from the lumbar route in two patients, so we had to resort to the caudal route. The problems associated with the placement of the catheter from the lumbar route are discussed. The analgesia was provided for up to 72 h. Nineteen of the babies could be extubated in the operating theatre. They were awake but comfortable at the time of extubation. There were no complications due to the technique. Subsequent to this study, epidural analgesia either by lumbar or caudal route has become the routine in our hospital for all major thoraco-abdominal surgical procedures in neonates.

Tunnelling of caudal epidural catheters in infants

The working conditions in the developing world necessitate the development of many adaptations and improvizations of accepted anaesthetic techniques to improve patient care. Subcutaneous tunnelling of caudally placed epidural catheters is one such improvization to prevent the soiling of the catheter by urine and faeces. This study compares the duration of retention of catheter in a group with tunnelled catheters with an untunnelled group. The absence of a catheter emerging through skin at the site of catheter insertion hastens healing thus prolonging the retention of catheter in the tunnelled group and soiling ceases to be a major problem.

An unusual cause of tracheal stenosis

PURPOSE

To report a large chronic tracheal foreign body, causing tracheal stenosis in an 11-yr-old girl.

CLINICAL FEATURES

The history was suggestive of obstructive airways disease with secondary bronchiectasis. Physical findings were crepitations and rhonchi all over the chest. Blood gases were normal. Chest X-ray showed bronchiectasis and a ventilation perfusion scan identified a tracheo-esophageal fistula. During anesthesia to confirm this, intubation and ventilation were difficult because of tracheal stenosis. The hypoventilation resulted in severe hypercarbia and acidosis. A subsequent CT scan showed a stenosis of 2 mm diameter and 1 cm length in the middle third of trachea, bronchiectasis, and an air filled pocket between the trachea and esophagus. PFT showed a severe obstruction. Antitubercular treatment which was started on the presumptive diagnosis of tuberculous stenosis and tracheoesophageal fistula caused a delay with deterioration of patient from intermittent dyspnea to orthopnea with severe hypecarbia and acidosis. The anesthetic management of the tracheal reconstruction was difficult due to her moribund condition even after medical treatment, the short length of the trachea above the obstruction, its severity and lack of resources for alternative techniques. A large foreign body was found lying obliquely in the trachea dividing it into an anterior narrow airway mimicking a stenosed trachea, and a wider posterior blind passage.

CONCLUSION

The anesthetic consequences were peculiar to the unexpected etiology of the stenosis and poor general condition of the patient. Minor details like the tracheal tube bevel and ventilatory pattern became vitally important.