Association between hypertension and deep vein thrombosis after orthopedic surgery: a meta-analysis

Hypertension is one of the major causes of disease burden all over the world [1]. In 2000, it was estimated that approximately 1 billion cases suffered hypertension and by 2025, the number is predicted to increase to 1.56 billion [2]. It is one of the most important risk factors for heart disease, stroke, coronary artery disease, and premature death [3]. Obesity, smoking, alcohol consumption, age, and education have been reported to play important roles in the risk of untreated and uncontrolled hypertension [4‐6].

Deep vein thrombosis (DVT) is a systemic disease with a incidence of 67 per 100,000 of cases every year [7]. DVT could lead to postphlebitic syndrome, pulmonary embolism, and even death. In spite of adequate treatment, 1–8 % of patients developing pulmonary embolization will die [8, 9] and others will undergo long-term complications including chronic thromboembolic pulmonary hypertension and postphlebitic syndrome [10]. DVT is commonly associated with several co-morbidities. Over the past several years, studies on the association between DVT and hypertension have been reported, but the results are inconsistent. Some studies verified that hypertension could increase the development of DVT [11, 12]. However, Wang et al. [13] and Song et al. [14] reported that there was no statistically significant correlation between DVT and hypertension. Therefore, the controversial issue remains to be investigated.

Thus, in the current study, we performed a meta-analysis of available eligible studies to better elucidate the association between hypertension and DVT after orthopedic surgery.

The paper did not involve any human or animal study, so the ethical approval was not required.

In spite of the inherent risk of developing DVT for patients with orthopedic surgery, researches on risks of developing DVT were limited. Red blood cell storage has been found to be associated with increased incidence of DVT [35]. A previous report has indicated that patients with increased concentrations of factor VIII and von Willebrand’s factor have increased risk of DVT [36]. Compared with healthy controls, levels of red cell distribution width were higher in pre-hypertensive and hypertensive patients independently of age, inflammatory status, and anemia, suggesting the correlations between red cell distribution width and hypertension [37]. All of these may hint a potential relationship between DVT and hypertension.

The only risk factor of DVT in accordance with the conclusion from this meta-analysis is hypertension, which has already been verified previously. Several prospective studies have addressed the associations between hypertension and DVT. Patients with hypertension have been found with 2-fold increased likelihood of developing DVT [38]. In the current study, the results of meta-analysis in each subgroup have showed that hypertension may promote the formation of DVT after orthopedic surgery. In addition, hypertension has been found as an independent predictor of venous thromboembolism (VTE) in the general population [39]. In another study, after a prospective registry of 5451 patients with DVT, Goldhaber et al. [40] have found that 50 % patients have co-morbidities with hypertension. Kaisorn et al. [41] have also reported that hypertension may independently increase the risk of developing operative DVT (OR 1.785; 95 % CI 1.180–2.699; P = 0.006).

Age is a high prevalence of asymptomatic DVT event which has been identified in patients over 80 years [42]. A previous study with 102 consecutive patients of follow-up found that age greater than 65 years, body mass index (BMI) > 30 kg/m², and smoking were risk factors for DVT [43]. In a recent study comprising 87 574 individuals found that obesity was a causal risk factor for DVT [44]. Examining on VTE, Chamberlain et al. [45] found that low-density lipoprotein cholesterol was not an risk factor of VTE. Another study with 855 men (65 VTE events) identified that smoking and waist circumference were risk factors for VTE, whereas high cholesterol and hypertension were not [46]. In addition, a Copenhagen City Heart Study pointed out that hypertension, smoking, and obesity were important risk factors for VTE, whereas total/high-density lipoprotein/low-density lipoprotein cholesterol, triglyceride, and diabetes mellitus were not [47].

Some limitations of this study should be addressed. First, only published studies were included and publication bias might exist, although no significant bias was detected by Egger’s test. Second, significant heterogeneity across studies was presented in overall and subgroup analysis, which might influence the pooled results. Third, although there was no limitation for language, only Chinese population was included, which might lead to bias. Fourth, as limited researches included in this meta-analysis, association between DVT and age, BMI, or gender was not analyzed. Finally, the small sample size was still insufficient to obtain a conclusive result. However, larger and well-designed studies based on different populations are warranted to validate our results.

In conclusion, this study showed that hypertension might promote DVT after orthopedic surgery, and it might be an important risk factor of DVT occurrence.