Vacuum-assisted venous drainage versus gravitational venous drainage in patients undergoing cardiac surgery: A meta-analysis

Abstract

Introduction

Vacuum-assisted venous drainage (VAVD) has been proposed as a better alternative option than conventional gravitational venous drainage (GVD) in cardiac surgery. However, the literature reports conflicting results between both methods in terms of post-cardiac surgery complications. Therefore, we aimed to perform a meta-analysis to compare clinical outcomes between VAVD and GVD in patients undergoing cardiac surgery.

Methods

PubMed, Scopus, and Web of Science databases were searched for any randomized control trials or cohort studies that compared clinical outcomes between VAVD and GVD in patients undergoing cardiac surgery.

Results

Sixteen studies with 8426 patients were included in our study. The pooled effect estimate of the postoperative results showed a statistically significant association between VAVD and decreased blood loss/chest tube drainage (MD = −88.7, 95% CI = −154.71 to −22.69, p-value = 0.008), amount of packed red blood cells (pRBC) transfusion (MD = −0.25, 95% CI = −0.27 to −0.22, p < 0.00,001), re-exploration (RR = 0.6, 95% CI = 0.35 to 1, p = 0.05), and re-operation (RR = 0.47, 95% CI = 0.23 to 0.99, p-value = 0.05). However, our study revealed no significant difference between both groups in terms of postoperative mortality, hospital/ICU stay, other blood product transfusions, change of free hemoglobin at 24 h, and other clinical outcomes.

Conclusion

Our study revealed that VAVD is at least equivalent and may provide some benefits compared to GVD in patients undergoing cardiac surgery. While, VAVD requires specific expertise and training in order to optimize its outcomes, its ability to reduce blood loss and blood transfusion, support its use as a valuable alternative for GVD in high-risk groups.

Keywords

vacuum-assisted venous drainage gravitational venous drainage cardiopulmonary bypass cardiac surgery

Introduction

Cardiopulmonary bypass (CPB) is a valuable tool that is utilized in various types of cardiac-related surgeries, due to its ability to provide complete circulatory and end organ support during invasive cardiac surgical procedures.¹ A key component of any CPB circuit is efficient venous drainage, which enables sufficient blood flow to the extracorporeal circuit for oxygenation and perfusion.^2,3 The standard technique for venous drainage in CPB for cardiac surgeries has always been the gravitational venous drainage (GVD), which relies on gravitational power generated by the height difference between the patient body and the circuit reservoir.⁴ Notably, the additional length of tubing required to achieve the necessary elevation drop between the patient’s cannula and the reservoir in a gravitational system, together with larger-bore cannula and increased priming fluid volumes, can lead to vascular injury or hemodilution in some cases.⁵ However, with current volume-preservation techniques, such as venous autologous priming (VAP), longer circuits may no longer be indicated to achieve efficient GVD, and both GVD and VAVD techniques can be efficiently performed using same size tubing systems. In cases of inadequate drainage, vacuum-assisted venous drainage (VAVD) can be used as a supplementary tool to the standard GVD.^6,7 VAVD enhances venous return by exerting additional negative pressure to the venous reservoir. This technique may allow adequate venous drainage, while reducing the height difference between the patient and the machine, the need for large cannula, the need for large amount of priming volume and potentially the risk of hemodynamic instability.^8,9 Despite its potential benefits, VAVD has been linked to some possible adverse events, most importantly the high risk of hemolysis and air embolism, which can eventually result in organ dysfunction.^10–12 Moreover, several studies have investigated the clinical outcomes of VAVD with a direct comparison to GVD, however the majority of these studies are dependent on small sample size, while their findings are inconsistent and conflicting in some domains. To the best of our knowledge, there is a lack of comprehensive studies that provide an inclusive synthesis of all of the available evidence, which is mainly attributed to the significant heterogeneity between the published studies. Therefore, we conducted this systematic review and meta-analysis to evaluate existing data and investigate the efficacy and safety of VAVD compared to the standard GVD when utilized in patients undergoing cardiac surgeries, with aim of understanding the role of VAVD in current clinical practice.

Methods

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the Cochrane handbook for systematic reviews of intervention were followed to perform this meta-analysis.^13,14

Search strategy

Using these search terms ((vacuum assisted OR vacuum assisted venous drainage OR negative-pressure venous drainage OR single femoral venous drainage) AND (Cardiac surgery OR Heart surgery)), we searched for randomized control trials or cohort studies in PubMed, Web of Science, and Scopus databases from inception to 21 January 2025.

Inclusion and exclusion criteria

We included randomized control trials or cohort studies that compared vacuum assisted venous drainage versus conventional gravitational venous drainage in adult patients undergoing cardiac surgery. We excluded studies using kinetic-assisted venous drainage. We also excluded animal studies, case reports, case series, editorials, conference abstracts, non-English studies and reviews. So, the PICO (Population, Intervention, Comparison, Outcome) of our study is:

Population (P): Adult patients undergoing cardiac surgery

Intervention (I): Vacuum assisted venous drainage.

Control (C): Conventional gravitational venous drainage.

Outcomes (O): Post-operative clinical outcomes.

Study selection process

Two independent authors (A.G, T.K) screened the titles and/or abstracts of the searched papers to determine relevant studies. Then, the two authors reviewed the full texts of the retrieved reports independently. Any conflicts between authors were solved by the first author (K.R.M).

Data extraction and management

Two authors (M.I, T.K) extracted the following data: the first author’s last name, year of publication, age, gender, number of patients, body mass index (BMI), procedure performed, diabetes, hypertension, coronary artery disease, peripheral vascular disease, chronic kidney disease, mean cardiopulmonary bypass time, aortic cross clamp time, left ventricular ejection fraction (LVEF) and post-operative outcome measurements: mortality, hospital stay, intensive care unit (ICU) stay, extubation time, blood loss, blood/packed red blood cells (pRBCs) transfusion amount, blood/pRBC transfusion rate, platelet transfusion rate, fresh frozen plasma (FFP) transfusion rate, change of free hemoglobin at 24 h, acute kidney injury (AKI), cerebrovascular accident (CVA), liver failure, myocardial infarction (MI), arrhythmia, re-exploration, re-operation. Any conflicts between authors were solved by the first author.

Risk of bias and quality assessment

The Risk of Bias 2 (RoB 2) tool was used to assess the risk of bias of the included randomized control trials; each study was classified as: high risk, some concerns, or low risk of bias. Newcastle Ottawa Scale tool was used to perform quality assessment of the included cohort studies; each study was given a score and classified as: high, moderate, or low quality.

Data analysis

We used Review Manager (RevMan) software, version 5.4, which is provided by the Cochrane Collaboration to perform data analysis. Sensitivity analysis (leave-one-out test) was used. Dichotomous data were presented as Risk Ratio (RR) with 95% confidence interval (CI) and continuous data were presented as mean difference (MD) with 95% CI. We calculated the change between pre- and post-operative levels of free hemoglobin. If no heterogeneity was observed, results were presented in a fixed effect model, otherwise the random effect model was used. Results were considered significant if the p value was equal to or less than 0.05.

Results

Summary of studies

After searching the literature, 1558 studies were identified, and 1117 became eligible for title and abstract screening after removal of duplicates. Of the 1117 studies; 1040 were irrelevant and 77 studies were eligible for full-text screening. Finally, 16 studies were included in the meta-analysis as shown in the PRISMA diagram (Figure 1).^{8–12,15–25} The overall quality assessment of the included cohort studies was high in five studies, moderate in four studies and low in two studies, as shown in Table 1. The overall risk of bias of the included randomized control trials was low in three studies and some concerns in two studies, as shown in Table 2. The total number of patients included in the study is 8426 patients, 4352 patients in the vacuum-assisted group, and 4074 patients in the gravitational group, other baseline data are shown in Table 3.

Table 1.

Quality assessment.

	Selection				Comparability		Exposure			Total point	AHRQ standards
Study ID	(1) Representativeness	(2) Selection of the non- exposed cohort	(3) Ascertainment of exposure	(4) Demonstration that outcome of interest was not present at start of study	(1) Comparability of cohorts	(2) Additional comparability adjustment	(1) Assessment of outcome	(2) Was follow-up long enough for outcomes to occur	(3) Adequacy of follow up of cohorts	Total point	AHRQ standards
Aydin, 2020	0	1	1	1	1	0	1	1	0	6	Moderate
Banbury, 2003	0	1	1	1	1	0	1	1	0	6	Moderate
Carrier, 2002	0	1	1	1	1	1	1	1	0	7	High
Gaoa, 2019	0	1	1	1	1	0	1	1	0	7	High
Hayashi, 2001	1	1	1	1	1	0	1	0	0	6	Moderate
Marcheix, 2007	1	1	1	1	1	0	1	0	0	6	Moderate
Murai, 2005	0	1	1	1	0	0	1	0	0	4	Low
Peng, 2018	0	1	1	1	0	0	1	1	0	5	Low
Silvano, 2024	1	1	1	1	1	1	1	1	0	8	High
Ariyaratnam, 2013	1	1	1	1	1	1	1	1	1	9	High
Wang, 2023	1	1	1	1	1	1	1	1	0	8	High

AHQR: agency for healthcare research and quality.

Table 2.

Risk of bias.

Study ID	Bias
Study ID	Randomization process	Deviations from the intended interventions	Missing outcome data	Measurement of the outcome	Selection of the reported result	Overall bias
Bevilacqua, 2002	Some concerns	Low risk	Some concerns	Low risk	Some concerns	Some concerns
Goksedef, 2012	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk
Murakami, 1997	Some concerns	Some concerns	Some concerns	Some concerns	Some concerns	Some concerns
Nasso, 2010	Low risk	Low risk	Some concerns	Low risk	Low risk	Low risk
Pappalardo, 2007	Low risk	Low risk	Some concerns	Low risk	Low risk	Low risk

Table 3.

Baseline characteristics.

Study Id	Mean age		Gender (male)		Mean body surface area (BSA)		Number of patients		Type of procedure		Mean cardiopulmonary bypass time in minutes		Aortic cross clamp time in minutes		LVEF percentage
Study Id	VAVD	GVD	VAVD	GVD	VAVD	GVD	VAVD	GVD	VAVD	GVD	VAVD	GVD	VAVD	GVD	VAVD	GVD
Ariyaratnama, 2013	65.01	67.64	60	56	2.02	1.97	70	70	CABG	CABG	81.16	88.2	49.94	52.01
Aydin, 2020	60.75	61.1	29	16	1.84	1.91	40	20	CABG	CABG	117.35	111.5	73.35	69.1	56	55
Banbury, 2003	58	57	154	89	2	2	233	124	Valve	Valve	72.56	90
Bevilacqua, 2002	62	63	30	29	1.88	1.84	36	36	CABG	CABG	110.9	98.72	64.07	57.97	51.5	52.27
Carrier, 2002	65	63	413	381			822	723	265 CABG	177 CABG	117	108	83	79
Gao, 2019	56.9	55.8	563	583			1002	1002	359 CABG, 323 valve, 77 CABG + valve, 179 Congenital, 64 other	346 CABG, 329 valve, 53 CABG + valve, 132 Congenital, 142 other	90	90	59	62	61	60
Goksedef, 2012	63.48	60	66	38	1.82	1.83	102	55	CABG	CABG	99.5	101	70.03	69
Hayashi, 2001	55.2	58.9	13	18	1.56	1.56	30	30	Aortic valve disease 4	Aortic valve disease 5	157.7	165	109.8	112.6
									Mitral valve disease 10	Mitral valve disease 9
									Coronary artery disease 13	Coronary artery disease 14
									Congenital heart disease 3	Congenital heart disease 2
Marcheix, 2007	60.2	60	64	22			50	25	CABG	CABG	64.55	66.36	43.4	42.7
Murai, 2005	58.7	59.8			1.586	1.408	97	13			156	161.2	119.4	119
Murakami, 1997	64.9	59.6	13	11	1.63	1.64	17	13	CABG	CABG	141	163	83	94
Nasso, 2010	68.9	67			1.83	1.84	77	73	CABG 34	CABG 32	69.23	71.86	47	51
									AVR 11	AVR 10
									MVR 9	MVR 9
									Mitral valve repair 9	Mitral valve repair 8
									Ascending aortic replacement 5	Ascending aortic replacement 4
									CABG- valve replacement 9	CABG-valve replacement 10
Pappalardo, 2007	62.5	63	8	6	1.64	1.57	20	20	AVR 5	AVR 3	79	74	61	53	61	59
									MVR 5	MVR 5
									TVR 0	TVR 2
									MV repair 9	MV repair 8
									TV repair 9	TV repair 2
									MV commissurotomy 1	MV commissurotomy 0
									AF ablation 4	AF ablation 3
Peng, 2018	51.29	52.64	8	5			28	22	Tricuspid valve replacement 25	Tricuspid valve replacement 11	72.96	78.59	Not done	Not done	61.61	60.68
Peng, 2018	51.29	52.64	8	5			28	22	Tricuspid valvuloplasty 3	Tricuspid valvuloplasty 11	72.96	78.59	Not done	Not done	61.61	60.68
Silvano, 2024	75	75	67	62	1.79	1.79	129	129	AVR	AVR	71	73	55	57	60	60
Wang, 2023	56.7	56.8	745	746			1468	1468	Isolated CABG surgery 562	Isolated CABG surgery 556	117	118	82	82	60	60
									Isolated valve surgery 401	Isolated valve surgery 405
									CABG and valve surgery 150	CABG and valve surgery 152
									CHD repair	CHD repair
									VSD 65	VSD 68
									ASD 61	ASD 67
									Vascular surgery	Vascular surgery
									AAR 37	AAR 39, wheat procedure 55
									Wheat procedure 63	Bentall procedure 56
									Bentall procedure 59	Cardiovascular tumor
									Cardiovascular tumor	Benign 51
									Benign 45	Cancer 9
									Cancer 11	Other 10
									Other 14	Other 10

CABG: coronary artery bypass grafting; LVEF: left ventricular ejection fraction; AVR: aortic valve replacement; MVR: mitral valve replacement; TVR: tricuspid valve replacement; CHD: coronary heart disease; VSD: ventricular septal defect; ASD: atrial septal defect; AAR: aortic ascending replacement.

Postoperative outcomes

The pooled analysis showed no statistically significant difference between VAVD and GVD regarding mortality (10 studies) (Figure 2), hospital stay (5 studies), ICU stay (6 studies), extubation time (7 studies) (Figure 3(a)–(c)) (Table 4).

Table 4.

Outcomes and statistical results.

Outcome	Statistical results	Heterogeneity	figure
Mortality	RR = 1.08 [0.76,1.54], p-value = 0.67	p = 0.43, I² = 0%	Figure 2
Hospital stay	MD = −0.54 [−1.86,0.78], p-value = 0.42	p < 0.00001, I² = 98%	Figure 3(a)
Hospital stay	MD = −0.54 [−1.86,0.78], p-value = 0.42	Heterogeneity was not resolved by leave one out test	Figure 3(a)
ICU stay	MD = 0.18 [−0.09,0.45], p-value = 0.19	p = 0.28, I² = 20%	Figure 3(b)
Extubation time	MD = −0.12 [−0.28, 0.03], p-value = 0.12	p = 0.34, I² = 12%	Figure 3(c)
Rate of pRBC transfusion	RR = 0.93 [0.6,1.45], p-value <0.00001	p < 0.00001, I² = 85%	Figure 4(c)
Rate of pRBC transfusion	RR = 0.93 [0.6,1.45], p-value <0.00001	Heterogeneity was not solved by leave one out test	Figure 4(c)
Platelet transfusion	RR = 0.32 [0.01,12.08], p-value = 0.53	p = 0.02, I² = 82%	Figure 4(d)
Platelet transfusion	RR = 0.32 [0.01,12.08], p-value = 0.53	Significant heterogeneity between the 2 studies	Figure 4(d)
FFP transfusion	RR = 0.7 [0.36,1.38], p-value = 0.3	p = 0.77, I² = 0%	Figure 4(e)
Change of free hemoglobin level at 24 h	MD = 5.64 [−1.7,12.97], p-value = 0.13	p = 0.005, I² = 77	Figure 5
	After leave one out test:	Heterogeneity was resolved by leaving out Murakami, 1997
	MD = 2.01 [−2.99,7.01], p-value = 0.43	Heterogeneity was resolved by leaving out Murakami, 1997
AKI	RR = 0.9 [0.63,1.29], p-value = 0.57	p = 0.06, I² = 65%	Figure 6(a)
CVA	RR = 1.09 [0.65,1.82], p-value = 0.75	p = 0.31, I² = 23%	Figure 6(b)
Liver failure	RR = 0.64 [0.32,1.27], p-value = 0.2	p = 0.9, I² = 0%	Figure 6(c)
MI	RR = 2.29 [0.78,6.71], p-value = 0.13	p = 0.96, I² = 0%	Figure 6(d)
Arrhythmia/atrial fibrillation	RR = 1.63 [0.59,4.53], p-value = 0.35	p = 0.007, I² = 80%	Figure 6(e)
	After leave one out test:	Heterogeneity was resolved by leaving out Silvano, 2024
	RR = 2.66 [1.37,5.18], p-value = 0.004	Heterogeneity was resolved by leaving out Silvano, 2024

ICU: intensive care unit; pRBC: packed red blood cells; FFP: fresh frozen plasma; AKI: acute kidney injury; CVA: cerebrovascular accident; MI: myocardial infarction; RR: risk ratio; MD: mean difference; CI: confidence interval.

For blood loss/chest tube drainage outcome (9 studies), the pooled analysis showed a statistically significant association between VAVD and decreased blood loss/chest tube drainage (MD = −88.7, 95% CI = −154.71 to −22.69, p-value = 0.008). A statistically significant heterogeneity was observed among the studies (p < 0.00,001, I² = 91%) (Figure 4(a)) which was not solved by leave one out test.

A statistically significant association was noted between VAVD and a decreased amount of blood/pRBCs transfusion (6 studies) compared with GVD (MD = −0.25, 95% CI = −0.27 to −0.22, p < 0.00,001). We observed no statistically significant heterogeneity between studies in the amount of blood/pRBC transfusion outcome (p = 0.21, I² = 29%) (Figure 4(b)). However, there was no statistically significant difference regarding the rate of pRBC transfusion (12 studies), platelet transfusion (2 studies), FFP transfusion (2 studies), (Figures 4(c)–(e)), change of free hemoglobin level at 24 h (4 studies), (Figure 5), AKI (5 studies), CVA (9 studies), liver failure (3 studies), MI (4 studies), arrhythmia/atrial fibrillation (3 studies), (Figure 6(a)–(e)) (Table 4).

A marginally statistically significant association was noted between VAVD and decreased re-exploration (4 studies) compared with the gravitational group (RR = 0.6, 95% CI = 0.35 to 1, p = 0.05). We observed no statistically significant heterogeneity among studies (p = 0.18, I² = 38%) (Figure 6(f)).

Similarly, there was a marginally statistically significant association between VAVD and less re-operation (3 studies) (RR = 0.47, 95% CI = 0.23 to 0.99, p-value = 0.05) (Figure 6(G)). There was no significant heterogeneity (p = 0.11, I² = 55%).

Discussion

Our results are consistent with previous studies, which reported that VAVD improved the hematocrit values and reduced the required amount of total blood products transfusion.^8,19,26 Cardiac surgeries are usually associated with high risk of bleeding, that require transfusion, including packed red blood cells (PRBCs), platelets, FFP and whole blood. This high rate of blood transfusion is associated with elevated risk of transfusion-related complications, which includes infections and allergic reactions.^27–31 Our findings illustrate the fact that VAVD could have the potential to reduce the amount of transfusion required and eventually reduce its associated risks. Generally, the increased blood loss that is associated with GVD could be mainly linked to the utilization of large cannulas which increases the risk of traumatic vascular injury, as well as the use of higher amount of priming volume, which contributes to greater hemodilution, that can eventually translates to more blood loss.²³ In absence of techniques that reduce priming volumes, such as venous autologous priming, VAVD may offer an advantage in terms of requiring less priming volume. However, the application of such techniques may eliminate this advantage as less priming volume is required for both GVD and VAVD. On the other hand, the utilization of VAVD may enhance drainage and perfusion flow thus improving cardiac decompression and lowering central venous pressure.^24,25 Ultimately, this is reflected in the fewer cases requiring re-operation or re-exploration in the VAVD group compared to the GVD group.

In literature, the most common adverse events that are usually theoretically associated with VAVD are hemolysis and air embolism, which can result in CVA, hypoperfusion and potential organ damage.^32,33 Nevertheless, our analysis reported that VAVD did not increase the risk of hemolysis, evident by the non-significant difference in the change of free HB level. Hemolysis has been reported as an adverse event of CPB, due to its technical aspects as well as its effect on circulation.³⁴ The additional negative pressure exerted with VAVD further increases the risk of hemolysis in the patients. Collective evidence from the literature demonstrates that the risk of hemolysis in VAVD is associated with excessive negative pressure.^35,36 Notably, studies suggest that this risk can be reduced with more careful and controlled vacuum pressure, with some reports indicating that maintaining the pressure within the range of −20 to −40 mmHg effectively prevents the occurrence of hemolysis.^23,25

Additionally, in our analysis VAVD was not associated with an elevated risk of CVA. This is inconsistent with previous studies, which reported that VAVD was associated with air entrainment resulting in cerebral emboli and the occurrence of CVA.^37,38 However, a randomized prospective trial conducted by Bevilacqual and colleagues reported no significant difference between the VAVD and GVD regarding the incidence of CVA.¹⁸ The high risk of CVA is attributed to the ability of VAVD to absorb air from the liquid solution into the tube due to its excessive negative pressure, which in turn accumulates and results in the formation of air embolism.³⁹ However, the risk of air embolism could be reduced by limiting the vacuum pressure to ≤30 mmHg and continuously monitoring the venous return with ultrasonic probe.

Clinical implications

In clinical practice, VAVD is recognized as a valuable alternative to GVD in cardiac surgery, especially in cases requiring more effective venous drainage and in situations where minimizing the risk of blood loss and the need for blood transfusion is preferred. However, current clinical guidelines do not implement a strong recommendation for VAVD in conserving blood loss, while listing it as a class IIb recommendation with the emphasis on the idea that VAVD is not a universal replacement for GVD but a situational tool, that needs specialized training and vigilant monitoring.^39–41 An important limitation with VAVD is the relatively higher risk of hemolysis and air emboli, however as we previously discussed, this risk can be effectively reduced or even prevented with low vacuum pressure (−20 to −40 mmHg), as stated in the 2024 EACTS/EACTAIC/EBCP guidelines.^42–44 Notably, VAVD setup and maintaining safe vacuum pressure are encompassed in the standard training of all US and European perfusionists and embedded in the pre-bypass checklist that is published as part of the AMSECT guidelines, making its technical implementation straightforward. However, centers lacking these established protocols may need to develop their own guidelines and team training to ensure proper control. Ultimately, the choice between VAVD or GVD is mainly dependent on the preferences of the cardiac surgeon and the perfusionist. Thus, our findings help in the decision-making process by demonstrating the ability of VAVD to reduce the amount of blood loss, the need for blood transfusion and need for re-operation, which can eventually be beneficial in high-risk groups.

Strength, limitations and recommendations

This systematic review and meta-analysis provide a comprehensive comparison between VAVD and GVD in cardiac surgery, by combining and consolidating current evidence from multiple previous studies. We included a large number of studies, encompassing a relatively large number of participants compared to previous studies on this subject and analyzed various outcomes to fully investigate the efficacy and safety of VAVD compared to GVD. However, despite its strengths, our review still had some limitations that should be discussed. Also, we addressed some clinical outcomes that were not adequately addressed in the literature and guidelines such as mortality, hospital/ICU length of stay, extubation time, AKI, liver failure, cerebrovascular accidents, myocardial infarction, arrhythmia, and re-operation. We observed significant heterogeneity among the included studies, due to variations in the studies designs, baseline characteristics of the included populations, type of the procedures and lack of standardized protocols for VAVD implementation. Nearly half of the studies included in this review were not randomized clinical trials and lacked proper blinding process, which was technically difficult to implement due to the nature of the intervention. Furthermore, the observational and retrospective nature of the majority of the included studies might have introduced biases that could affect the validity and generalizability of the findings. Furthermore, more evidence is needed to further investigate the optimal vacuum pressure to achieve the maximum benefits while minimizing the risks.

Conclusion

In our meta-analysis, we found an association between the use of VAVD and the reduction in the risk of blood loss and the amount of blood transfusion compared to when standard GVD is used. The potential benefits of VAVD also included a reduction in the need for re-operation and re-exploration. Additionally, our findings confirm that VAVD does not increase the risk of hemolysis, air embolism or organ dysfunction, if applied within proper safety precautions. While, VAVD requires specific expertise and training in order to optimize its outcomes, its ability to reduce blood loss and blood transfusion, support its use as a valuable alternative for GVD in high-risk groups.

Footnotes

ORCID iD

Karam R. Motawea

Ethical consideration

Not Applicable as it is a systematic review and meta-analysis study.

Author contributions

K.R.M (Idea validation, Supervision, Methodology, Writing, editing and review), A.F.G (Screening, Writing, Review), M.M.I (Data Extraction, Analysis, Writing, Review), T.S (screening, Data Extraction, Review), Y.K (writing, editing, reviewing), A.T (writing, editing, reviewing), M.E (reviewing, editing), Y.A (reviewing, editing), M.P (Supervision, Idea Validation, Editing and reviewing).

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Data Availability Statement

The data are found within the manuscript and data extraction sheet is available upon request.*

Appendix

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