The DVT occurs in the deep draining veins of the extremities with a propensity to appear in large veins of the lower extremities. More recently, the term Venous Thrombo-Embolism (VTE) has been used to refer both DVT and PE [1]. VTE is the third most common cardiovascular disorder after myocardial infarction and cerebro-vascular accident. The mortality rate known for thromboembolic events is significantly high and the 28-day fatality rates are reported to be 9% for DVT and 15% for PE [2].
This study was designed to assess the number of patients at risk for DVT in SICU and various forms of practices implemented for its prophylaxis.
Materials and Methods
This was a prospective, cross-sectional study that was carried out between February 2020 to April 2020 in Department of Anesthesiology and Critical care, Dr DY Patil Medical College, Hospital and Research Centre, Pimpri, Pune, Maharashtra, India. Prior ethical clearance was obtained from the Institutional Ethics Committee (Research Protocol No. IESC/FP/2020/19). Informed consent of the patients was obtained. In case the patients were unable to give informed consent due to altered sensorium, the same was sought from their attendees.
The aim of the study was to observe the DVT prophylaxis methods and to compare the incidence of DVT in the different methods used in SICU. A total of 62 patients were recruited. Twelve patients received mechanical prophylaxis alone, 20 patients received pharmacotherapy alone and 30 patients received both mechanical and pharmacological therapy.
Sample size calculation: The sample size was estimated to be 62 patients (incidence of 11%) based on a study by Major KM et al., [9]. The confidence interval was set at 95%, with a study precision of 7.5% using WinPepi statistical package. The patients were distributed in different groups based on discretion of treating intensivist and surgeon regarding need for pharmacotherapy or mechanical therapy or both leading to an uneven group size.
Inclusion criteria
Patients admitted in SICU aged between 18-70 years of age for ≥2 days.
Haemodynamically stable patients with all routine investigations within normal limits.
Patients who were not on drug altering the coagulation profile.
Availability of informed consent.
Exclusion criteria
Patients with major neurological, cardiac, respiratory, metabolic, renal, hepatic disease that can effect coagulation profile.
Patients with documented DVT/PE before or within 48 hours of ICU admission:
Study Procedure
Patients were assessed daily for the presence of DVT, form of prophylactic treatment received and complications, if any. All patients were followed-up closely until 28 days or ICU discharge (whichever was later). Method of DVT prophylaxis given (Mechanical/Pharmacological/Both) was noted. Mechanical prophylaxis included use of DVT stockings (inflation pressure ranging from 30-40 mmHg) or use of SCD (inflation pressure ranging from 50-120 mmHg for at least 18-20 hours a day). Pharmacological management included Low molecular weight heparin (LMWH) (30-40 mg subcutaneously 12 hourly). LMWH (enoxaparin) is the standard pharmaco-prophylactic measures practiced in most of the hospitals [10,11]. None of the patients were given unfractionated heparin in the study.
Statistical Analysis
The statistical analysis was done by evaluating the quantitative data that was analysed by using unpaired student’s t-test whereas qualitative data was analysed by Chi-square test. The p-value was considered as significant at a value of <0.05 set at 95% confidence intervals.
Results
The mean and SD of the age of patients was 50.36±6.8 years. Male participants were 42 (67.74%) and female participants were 20 (32.26%).
Mechanical prophylaxis had highest incidence of DVT but the difference was non-significant. Combined intervention was the most commonly used prophylactic measure [Table/Fig-1].
Type of intervention and incidence of DVT.
| Intervention | Type of prophylaxis n (%) | Incidence of DVT n (%) | p-value (chi-square test) |
|---|
| Mechanical prophylaxis alone | 12 (19.35%) | 2 (16.67%) | 0.332 |
| Pharmacotherapy alone | 20 (32.26%) | 2 (10%) |
| Both mechanical and pharmacotherapy | 30 (48.39%) | 1 (3.33%) |
The groups were comparable regarding incidence of haemorrhage with a non-significant p-value of >0.05 as depicted in [Table/Fig-2].
Type of intervention and incidence of haemorrhage.
| Type of prophylaxis | Incidence of haemorrhage |
|---|
| Mechanical prophylaxis alone | 0 of 12 (0%) |
| Pharmacotherapy alone | 3 of 20 (15%) |
| Both Mechanical and Pharmacotherapy | 1 of 30 (3.33%) |
| p-value (Chi-square test) | 0.136 |
The mean doses of enoxaparin used in pharmacotherapy alone and both mechanical therapy and pharmcotherapy groups were 63.69±15.2 and 42.33±7.85 mg/day, respectively and these were significantly (p<0.001) higher in pharmacotherapy alone group as depicted in [Table/Fig-3]. It should be noted that for mechanical prophylaxis in dual prophylaxis group, 15 patients used stockings and 15 used SCDs with mean doses of enoxaparin as 42±5.92 and 42.67±9.61 mg/day, respectively.
Mean dose/day of pharmacotherapy.
| Low molecular weight heparin (Enoxaparin) | Dose (mg/day) |
|---|
| Pharmacotherapy alone (n=20) | 63.69±15.2 |
| Both Mechanical and Pharmacotherapy (n=30) | 42.33±7.85 |
| Both mechanical and pharmacotherapy stockings (n=15) | 42±5.92 |
| Both mechanical and pharmacotherapy sequential compression devices (n=15) | 42.67±9.61 |
| p-value (Student’s t-test) | p<0.001 |
Fifteen patients (50%) used SCDs and 15 (50%) used DVT stockings in dual mechanical and pharmacotherapy prophylaxis group, whereas in mechanical therapy alone group, 8 (66.67%) used DVT stockings and 4 (33.33%) used SCDs as depicted in [Table/Fig-4].
Type of mechanical therapy.
| Type of mechanical therapy | Patients with mechanical and pharmacotherapy | Patients with mechanical therapy alone |
|---|
| DVT stockings | 15 (50%) | 8 (66.67%) |
| Sequential compression devices | 15 (50%) | 4 (33.33%) |
| Total | 30 (100%) | 12 (100%) |
Discussion
The DVT is the formation or presence of thrombus in deep veins, occurring most commonly in the lower extremities and rarely in upper extremities. Whereas, an obstruction of the pulmonary artery or its branches by a thrombus results in the development of PE; most likely source being an embolisation from deep veins of the legs and occurs approximately in one-third of patients with DVT. Hence, prevention of DVT significantly decreases the incidence of a serious and life-threatening condition called PE [12]. Hoyt DB and Swegle JR suggested that aggressive prophylaxis, a high index of suspicion, and definitive diagnosis and treatment are essential to decrease the morbidity and mortality rates from DVT in patients admitted in SICU [13].
Harris LM et al., noted that screening of SICU patients is indicated because of a high prevalence of asymptomatic disease which was found to be 7.5% in 294 patients admitted in SICU [14]. Normally, a balance between the procoagulant and anticoagulant factors present in the blood prevents the intravascular formation of thrombus. Presence of one or more factors constituting the triad of Virchow (venous stasis, endothelial injury and hypercoagulability) can contribute to the development of DVT. Hospitalised patients are at risk of venous stasis and with the presence of other factors, they are at increased risk of DVT and this increases the risk of PE. Prophylaxis of DVT constitute methods that target either the venous stasis (mechanical methods) or the hypercoagulability (pharmacological methods) of the vascular system.
The overall incidence of DVT was 3.33% (1 of 30 patients) for patients receiving both mechanical and pharmacotherapy whereas it was 10% (2 of 20) for patients receiving pharmacotherapy alone and 16.67% (2 of 12) for patients using mechanical interventions. In a study by Kumar A et al., it was noted that the incidence of DVT was 0.8% with prophylaxis in patients admitted in SICUs [15]. A study by Miri M et al., noted incidence of 3.5% in ICU patients [16].
Incidence of haemorrhage was highest in pharmacotherapy alone group (n=3 of 20; 15%), no patients in mechanical intervention had haemorrhagic episode whereas one patient in dual intervention group (n=1 of 30) had haemorrhage. The overall dose of drugs used as pharmacotherapy was lesser in those receiving dual interventions compared to that of patients receiving pharmacotherapy alone. This explains lesser incidence of haemorrhagic manifestations in combined group when compared to pharmacotherapy alone group. Fraisse F et al., noted higher incidence of bleeding in patients receiving pharmacotherapy for DVT prophylaxis than those not receiving any pharmacotherapy [17]. Cook DJ and Crowther MA suggested use of optimal DVT prophylaxis in order to prevent development of DVT in patients at risk and this should be balanced with risk of bleeding [18].
In a systematic review by Kakkos SK et al., in the IPC (Intermittent Pneumatic Compression) group, the incidence of DVT was noted to be 4.10% [19], whereas, in the combined group (IPC+ pharmacotherapy), it was 2.19%, showing a reduced occurrence of DVT in favour of the combined group. Moreover, anticoagulant addition to the IPC increased the risk of any bleeding as compared to IPC alone. Nevertheless, patients admitted in SICU need to be regularly evaluated for development of DVT. Dagadaki O et al., suggested periodical ultrasound assessment of the peripheral venous system in intensive care unit patients to screen for DVT [20].
Limitation(s)
The sample size was limited and the findings cannot be extrapolated to all the patient populations. Only American Society of Anesthesiologists (ASA) Grade III patients were included. The study evaluated adult patients and excluded elderly ones above 70 years and those with significant co-morbid conditions as these are potentially confounding factors and may be associated with increased risk for bleeding manifestations as well as thromboembolic complications; thereby leading to a bias in study findings.
Conclusion(s)
It was noted that a mix of mechanical and pharmacological measures are associated with reduced incidence of DVT. The overall dose of drugs used as pharmacotherapy was the lesser in those receiving dual interventions compared to that of patients receiving pharmacotherapy alone. Pharmacotherapy and pressure stockings together are an ideal therapy for DVT prophylaxis, as per this study. However, it is suggested that similar studies should be conducted with a higher patient participation and a long term follow-up.