Development of a Novel CaP-Containing Mesoporous Silica-Based Xerogels Used as Hemostatic Material with Good Biodegradability and Low Heat Generation

A novel Ca/P-containing mesoporous silica-based xerogels (CaMSX) with good degradability and low heat generation were synthesized for hemorrhage control by a modified sol-gel process and physicochemically characterized. The mesoporous silica-based xerogels without Ca/P (MSX) was also prepared as comparison. The in vitro whole blood coagulation time, activated partial thromboplastin time (APTT) and prothrombin time (PT) of the CaMSX were measured with MSX, Chinese traditional medicin-Yunnan medical powder (YM) and traditional zeolite. In vivo bleeding model was tested with rabbit’ ear side veins. The results illustrated that the CaMSX could remarkably promote the intrinsic and extrinsic blood coagulation processes which greatly depend on the dosage and the content of Ca in the CaMSX. The CaMSX had better efficiency in promoting coagulation process than that of MSX, YM and zeolite.

Investigations of the Dose of Heparin and Whole Blood Coagulation Time during Endovascular Surgery

We chronologically determined whole blood coagulation time during continuous heparin administration, and investigated optimal doses of heparin in thirty-seven vascular surgery cases. ACT was determined with Hemochron 401. Heparin (2000 IU) was administered by bolus injection at the beginning of intravascular surgery, which was followed by continuous injection of 20 to 160 IU/kg/h. ACT determined before and 30 minutes after heparin administration were compared. There were no complications. ACT was maintained at a nearly constant level by continuous heparin administration. The dose of heparin required to maintain ACT at a level 1.5 to 2 times the initial level was 20 to 60 IU/kg/h. ACT was prolonged by more than three times in two of the ten subjects who were given heparin at a dose of 70 IU/kg/h or more. Continuous administration of heparin allowed maintenance of ACT at a nearly constant level during intravascular surgery. ACT was maintained within the range which is believed to be effective for prevention of thrombus formation (approximately 1.5 to 2.0 times larger than the initial level) by continuous administration of 20 to 60 IU/kg/h of heparin. ACT was, however, prolonged to more than three times the initial level in some subjects who were given 70 IU/kg/h or higher doses, suggesting the risk of a bleeding tendency. Accordingly, it is ideal to continue heparin administration at appropriate doses, while measuring ACT. The results of our study should serve as a useful standard for meeting this goal.

HOW DOES CALCIUM ALGINATE ACHIEVE HAEMOSTASIS IN SURGERY?

Calcium alginate (Kaltostat, Cair Ltd) is a new absorbable material for topical haemostasis in surgery. The possible mode of action, release of calcium ions in exchange for sodium was investigated in human blood.Calcium release was measured in 15 mg samples of calcium alginate placed in 20 ml of 0.9% saline, for intervals of 1, 3 or 10 minutes. To assess the effect on platelets, 3 mg of calcium alginate or surgical gauze were added to 5 ml of Heparinised (100 units) fresh blood for 2 minutes and platelet counts then made using plain blood as a control. Finally using a thrombelastograph, the activation of whole blood coagulation was assessed after a 2 minute contact with 3 mg of calcium alginate, surgical gauze or no additive as control.When calcium alginate was placed in saline, 26% of calcium ions were released in 1 minute giving a calcium ion concentration of 4.62 t 0.02 mmol/L, with only slight further release after 10 minutes to 4.82 ± 0.004 mmol/L. There was a corresponding decrease in sodium ion concentration. Adding calcium alginate to whole blood reduced the platelet count from a control value of 248 i 16 × 109/L to 222 f 15 × 109/L (p< 0.05) compared to 241 ± 15 × 109/L for surgical gauze. Similarly calcium alginate shortened whole blood coagulation time from 17-7 i 1.0 minutes control, to 12.9 ± 1-32 mins (p< 0.001) compared to 15.0 ± 1.5 mins (p< 0.02) for surgical gauze.Calcium alginate rapidly releases calcium ions in exchange for sodium on contact with blood stimulating both platelet activation and whole blood coagulation, significantly more than simple contact activation by surgical gauze.