Protection against high intravascular pressure in giraffe legs.

The high blood pressure in giraffe leg arteries renders giraffes vulnerable to edema. We investigated in 11 giraffes whether large and small arteries in the legs and the tight fascia protect leg capillaries. Ultrasound imaging of foreleg arteries in anesthetized giraffes and ex vivo examination revealed abrupt thickening of the arterial wall and a reduction of its internal diameter just below the elbow. At and distal to this narrowing, the artery constricted spontaneously and in response to norepinephrine and intravascular pressure recordings revealed a dynamic, viscous pressure drop along the artery. Histology of the isolated median artery confirmed dense sympathetic innervation at the narrowing. Structure and contractility of small arteries from muscular beds in the leg and neck were compared. The arteries from the legs demonstrated an increased media thickness-to-lumen diameter ratio, increased media volume, and increased numbers of smooth muscle cells per segment length and furthermore, they contracted more strongly than arteries from the neck (500 ± 49 vs. 318 ± 43 mmHg; n = 6 legs and neck, respectively). Finally, the transient increase in interstitial fluid pressure following injection of saline was 5.5 ± 1.7 times larger (n = 8) in the leg than in the neck. We conclude that 1) tissue compliance in the legs is low; 2) large arteries of the legs function as resistance arteries; and 3) structural adaptation of small muscle arteries allows them to develop an extraordinary tension. All three findings can contribute to protection of the capillaries in giraffe legs from a high arterial pressure.

Effect of hemostatic material on sternal healing after cardiac surgery.

BACKGROUND: Postoperative sternal infection and dehiscence cause increased morbidity, mortality, and socioeconomic costs as well as patient discomfort and pain. Some predisposing factors have been uncovered but others remain uninvestigated. Among these are the influence of topical hemostatic agents such as bone wax (BW) and Ostene (Ceremed Inc, Los Angeles, CA) a new, water-soluble polymer wax (WSW). The object of this study was to investigate the impact of topical hemostatic agents on sternal healing in patients. METHODS: In total, 50 patients subjected to elective cardiac surgery and requiring intraoperative hemostatic treatment were randomized to 1 of 2 treatment groups: BW or WSW. Twenty-five patients without need for sternal hemostasis constituted a control group. The doctors analyzing the endpoints were blinded to the treatment. Radiologic bone healing was assessed by a radiologist using computed tomography at 3 and 6 months postoperatively. Quality of life and bodily pain was assessed by questionnaires (Short Form-36 and Visual Analogue Scale). RESULTS: No patients displayed complete radiologic healing at 3 months. Bone healing (evaluated semi-quantitatively at a score from 0 to 10) was significantly impaired in the BW group compared with both the control and WSW groups at both 3 and 6 months postoperatively (p < 0.0001). Radiologic bone healing was positively correlated with physical functioning score (Short Form-36) (p < 0.001). Pain scores were generally low (<1) at both 3 and 6 months with no significant difference between study groups. CONCLUSIONS: The results from this study suggest that WSW provides a useful alternative to BW when topic hemostasis on the sternum is required.

Bone healing after median sternotomy: a comparison of two hemostatic devices.

BACKGROUND: Bone wax is traditionally used as part of surgical procedures to prevent bleeding from exposed spongy bone. It is an effective hemostatic device which creates a physical barrier. Unfortunately it interferes with subsequent bone healing and increases the risk of infection in experimental studies. Recently, a water-soluble, synthetic, hemostatic compound (Ostene®) was introduced to serve the same purpose as bone wax without hampering bone healing. This study aims to compare sternal healing after application of either bone wax or Ostene®. METHODS: Twenty-four pigs were randomized into one of three treatment groups: Ostene®, bone wax or no hemostatic treatment (control). Each animal was subjected to midline sternotomy. Either Ostene® or bone wax was applied to the spongy bone surfaces until local hemostasis was ensured. The control group received no hemostatic treatment. The wound was left open for 60 min before closing to simulate conditions alike those of cardiac surgery. All sterni were harvested 6 weeks after intervention.Bone density and the area of the bone defect were determined with peripheral quantitative CT-scanning; bone healing was displayed with plain X-ray and chronic inflammation was histologically assessed. RESULTS: Both CT-scanning and plain X-ray disclosed that bone healing was significantly impaired in the bone wax group (p < 0.01) compared with the other two groups, and the former group had significantly more chronic inflammation (p < 0.01) than the two latter. CONCLUSION: Bone wax inhibits bone healing and induces chronic inflammation in a porcine model. Ostene® treated animals displayed bone healing characteristics and inflammatory reactions similar to those of the control group without application of a hemostatic agent.