Objective During primary total knee arthroplasty (TKA), anticoagulant drugs are used for prevention of major venous thrombosis of lower limbs, and this often leads to the increase of perioperative blood loss. To retrospectively analyse the impact of low molecular weight heparin on hidden blood loss and transfusion rate after primary TKA by comparing with the use of aspirin. Methods Between October 2007 and August 2009, the clinical data from 286 patients undergoing primary TKA surgery were retrospectively analyzed. In accordance with different anticoagulation methods, the cases were divided into 2 groups, the trial group (n=166) and the control group (n=120). In the trial group, the patients received low molecular weight heparin (4 000-6 000 U/day) from 8-12 hours after TKA for 14 days; there were 27 males and 139 females with an average age of 66.1 years (range, 22-82 years); the body mass index (BMI) was 26.79 ± 3.87; and the locations were the left knee in 99 cases and the right knee in 67 cases with an average disease duration of 4.1 years (range, 1.8-8.6 years). In the control group, the patients received aspirin (150 mg/day) for 14 days; there were 21 males and 99 females with an average age of 64.9 years (range, 40-84 years); the BMI was 27.87 ± 3.62; and the locations were the left knee in 78 cases and the right knee in 42 cases with an average disease duration of 4.9 years (range, 1.5-8.2 years). There was no significant difference in the general data between 2 groups (P gt; 0.05). Results The incisions healed by first intention in all patients. Postoperative deep venous thrombosis occurred in 37 patients of the trial group and in 28 cases of the control group. All the patients were followed up 12-34 months (mean, 21.6 months). There were significant differences in the United States Hospital for Special Surgery (HSS) score of 2 groups between before surgery and after surgery (P lt; 0.05). The hidden blood loss was (40.55 ± 37.75) g/L in the trial group and (32.52 ± 40.13) g/L in the control group, showing significant difference (t=3.387, P=0.001); the dominant blood loss was (24.08 ± 14.63) g/L and (27.91 ± 18.47) g/L respectively, showing no significant difference (t= —1.899, P=0.059). The blood transfusion rates were 40.4% (67/166) in the trial group and 30.0% (36/120) in the control group, showing no significant difference (χ2=2.771, P=0.081); the transfusion volumes were (1.44 ± 4.03) U and (0.97 ± 3.50) U respectively, showing significant difference (t=2.071, P=0.039). Conclusion The low molecular weight heparin has effect on the hidden blood loss after primary TKA, which may increase postoperative blood loss and blood transfusion rate. The changes in hemoglobin should be monitored during the anticoagulant therapy, and the blood volume should be added promptly.
The implantation of biventricular assist device (BiVAD) is more challenging than that of left ventricular assist device for the interaction in the process of multiple input and output. Besides, ventricular assist device (VAD) often runs in constant speed (CS) mode in clinical use and thus BiVAD also faces the problems of low pulsation and imbalance of blood volume between systemic circulation and pulmonary circulation. In this paper, a delay assist mode for a VAD by shortening the support time of VAD was put forward. Then, the effect of the delay mode on cardiac output, pulsation and the function of the aortic valve was observed by numerical method and the rules of hemodynamics were revealed. The research showed that compared with VAD supported in CS mode, the VAD using delay mode in systolic and diastolic period proposed in this paper could meet the demand of cardiac output perfusion and restore the function of the arterial valves. The open ratio of aortic valve (AV) and pulmonary valve (PV) increased with the time set in delay mode, and the blood through the AV/PV helped to balance the left and the right cardiac volume. Besides, delay mode also improved the pulsation index of arterial blood flow, which is conducive to the recovery of the ventricular pulse function of patients.