ORIGINAL ARTICLE – VASCULAR
Interactive CardioVascular and Thoracic Surgery 22 (2016) 813–816 doi:10.1093/icvts/ivw042 Advance Access publication 25 February 2016
Cite this article as: Sergeant P, Kocharian R, Patel B, Pfefferkorn M, Matonick J. Needle-to-suture ratio, as well as suture material, impacts needle-hole bleeding in vascular anastomoses. Interact CardioVasc Thorac Surg 2016;22:813–16.
Needle-to-suture ratio, as well as suture material, impacts needle-hole bleeding in vascular anastomoses Paul Sergeanta,*, Richard Kocharianb, Bababhai Patelc, Matthew Pfefferkornd and John Matonickd a b c d
Serrey Consulting, Sint Joris Winge, Belgium Medical Affairs, Ethicon, Inc., Somerville, NJ, USA Clinical Development, Ethicon, Inc., Somerville, NJ, USA Advanced Modeling Group, Preclinical Research, Ethicon, Inc., Somerville, NJ, USA
* Corresponding author. Serrey Consulting, Reigersweide 16, 3390 Sint Joris Winge, Belgium. Tel: +32-475742771; e-mail: [email protected] (P. Sergeant).
Abstract OBJECTIVES: The purpose of this study was to examine the influence of material variables on needle-hole bleeding in vascular anastomoses. Material variables include suture size, needle-tip geometry and diameter, needle coating, suture material and coating and swage area. We attempted to determine whether particular suture material and a reduced needle-to-suture ratio (N:S ratio) could reduce the vessel wall defect and reduce needle-hole bleeding, without changing the suture diameter used for the anastomosis. METHODS: A comparative analysis was made of the needle-hole leak rate in end-to-end anastomoses of an ePTFE®-ePTFE® vascular graft with a PROLENE® polypropylene suture with HEMO-SEAL™ technology (HS, 1.84:1 N:S ratio), standard PROLENE® polypropylene suture ( polypropylene 1, 2.41:1 N:S ratio), an alternate standard PROLENE® polypropylene suture ( polypropylene 2, 2.06:1 N:S ratio) and a GORE-TEX™ ePTFE® suture (ePTFE® suture, 1.4:1 N:S ratio) in an ex vivo cardiopulmonary bypass pulsatile flow loop model using heparinized porcine blood. Testing was completed within the model with an activated clotting time between 250 and 500 s, at near normothermia (33–35°C) and at normotensive pressure levels (120/80 mmHg). A sample size of n = 20 was completed for each group. RESULTS: The average total sample leak rate was 19.8 ± 4.5 ml/min for the HS suture, 57.2 ± 7.2 ml/min for polypropylene 1, 33.8 ± 4.1 ml/min for polypropylene 2 and 46.5 ± 10.3 ml/min for the ePTFE suture. The average needle-hole leak rates were 0.63 ± 0.13 ml/min for the HS suture, 1.94 ± 0.23 ml/min for polypropylene 1, 1.14 ± 0.14 ml/min for polypropylene 2 and 1.56 ± 0.34 ml/min for the ePTFE® suture. A two-sided 95% confidence interval for the difference in leak rates showed that there were significant differences (44–67% reduction) in favour of the HS suture when compared with the alternative needles with the same suture material and different N:S ratios, and also a reduction (59%) compared with the sample with smaller N:S ratios but different suture material. CONCLUSIONS: The N:S ratio as well as the physical characteristics of the suture material are important factors in reducing needle-hole bleeding in vascular anastomoses. Keywords: Needle technology • Swage area • Bleeding • Needle-to-suture ratio
INTRODUCTION Each time a needle penetrates a blood vessel, trauma is created in the wall, often only visible decades later when intimal proliferation has occurred. Bleeding through the suture holes is a more quantifiable early surrogate for trauma, visible in real time. Bleeding that results in the need for transfusion may have immunological and infectious consequences, which may be significant and are known to increase the risk of the procedure and the cost of hospitalization. The most frequently cited immunological reactions after blood transfusions are acute and delayed haemolytic reactions [1, 2], febrile non-haemolytic reactions, allergic reactions, post-transfusion purpura and transfusion-associated acute lung injury. Additionally,
the need for blood transfusion is a risk factor for surgical-site and general infection [3, 4]. The trauma and bleeding of the blood vessel are influenced by patient, surgeon, needle and suture material variables. Patient variables include the level of anticoagulation or antiaggregation, blood pressure, vessel wall and stability of the anastomotic site. Surgeon variables include the stability of posture, hand, needle holder and needle, rotational capacity of the needle holder by the surgeon, motion when unlocking the needle holder, the needle angle and entry/exit pathway curve and control and anastomotic technique. Suture variables include the needle diameter and length, needle curvature, suture size, the needle and suture coating,
© The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ORIGINAL ARTICLE
Received 12 November 2015; received in revised form 5 January 2016; accepted 18 January 2016
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P. Sergeant et al. / Interactive CardioVascular and Thoracic Surgery
needle-tip geometry and the swage area and needle:suture ratio (N:S ratio). Needle diameter is the width of the wire of the finished needle in combination with the thickness of the coating. Needle curvature is expressed in degrees of the subtended arc. Needle length is the arc length of the needle measured at the centre of the wire’s cross section. N:S ratio is the relationship between the diameter of the needle and the diameter of the suture at its region of largest diameter. Theoretically, the closer the N:S ratio approaches 1:1, lower rates of bleeding should be obtained because the suture fills the hole made by the needle.
METHODS Testing method and materials used The suture-hole leak rate of the HEMO-SEAL™ technology (HS) suture, which has a reduced N:S ratio (Fig. 1), was compared with suture-hole leak rate of three commercially available sutures of similar size, but with various N:S ratios ( polypropylene 1 and polypropylene 2) and suture material (ePTFE) (see Table 1). The suturehole leak rate was measured after completing an end-to-end ePTFE to ePTFE® vascular graft anastomoses in an ex vivo cardiopulmonary bypass pulsatile flow loop with heparinized porcine blood. The HS suture has been engineered to include a suture with a tapered region at the needle attachment point with a smaller diameter than that of the rest of the suture, allowing it to be swaged to smaller diameter needles. The ePTFE® suture is a monofilament suture with a porous microstructure that is 50% air by volume. Polypropylene 1 is a 5-0 PROLENE polypropylene suture with a C-1 needle. Polypropylene 2 is a CE-marked 5-0 PROLENE polypropylene suture with the C-1
Figure 1: The different swage areas: A for a standard PROLENE® suture with stainless steel C-1 needle (14 mil diameter, B for a HEMO SEAL® Prolene suture, Everpoint® C-1 needle (10.5 mil diameter).
needle, and the ePTFE® suture is a CV-6 Gore-Tex ePTFE suture with a TTc-13 needle. An ePTFE graft was cut to a length of 8 cm. The graft was then mounted to a plastic fitting on both ends, secured in place with tubing clamps and then transected at its mid-point. A complete end-to-end anastomosis was created using a simple continuous suture pattern with one of the test sutures described above. All anastomoses were performed by the same surgeon. The surgeon’s hands were stabilized, as appropriate in modern surgery, and a new needle holder with rounded handle and open latch (Scanlan® 6006–129), and new forceps (KLS Martin 12-254-17-07) were used for this experiment. The number of needle holes used in each anastomosis was recorded in the data sheets. It was attempted to have a 1 mm space between each needle hole [5]. The number of needle holes was used to calculate the needle-hole leak rate for each anastomosis. The total sample size of each study group was 20. The sequence of each anastomosis for this assessment was based on a randomization schedule and the surgeon was blinded from the suture choice except where (as with ePTFE®) the difference was visible with the naked eye. Prior to the acceptance of each anastomosis into the study, the anastomosis was pressure tested with saline at a static pressure of 120 mmHg to ensure that the leakage present along the suture line was from the suture holes only and not from the inter-suture spacing. Only one sample required an additional interrupted suture. A pulsatile ex vivo cardiopulmonary bypass model used a series of pumps and chambers to create, control and maintain blood pressure throughout the system. The model consists of a reservoir to filter blood returning from the test article, a computerintegrated data acquisition system, oxygenator and heat exchanger. Flow impedance and volume partitioning adjustments are present to allow for fine adjustment of blood volume flow and pressure control. To represent clinical conditions, a difference of 40 mmHg between the systolic and diastolic pressure was generated, resulting in a pulse pattern of 120/80 mmHg. The blood used within the model was donor porcine blood (Lampire Biological Laboratories, Pipersville, PA, USA). This blood was received heparinized, with 10 000 units of heparin per litre of blood, added upon removal from the donor animal. The blood was stored per the supplier’s recommendations and was used prior to expiration. The heparin level within the heparinized porcine blood was reversed to a target activated clotting time (ACT) of 250–500 s, consistent with clinical, non-experimental, levels when performing anastomoses with similar materials and similar clinical settings. Protamine sulphate (10 mg/ml) was slowly added to the circulating blood to reverse the effects of the heparin. An ACT measurement was performed at regular intervals to ensure the ACT level was within the acceptable range. The ACT was measured with a VetScan i-STAT Portable Handheld Unit (Abbott Point of Care) and an i-STAT ACT Celite Cartridge (Abbott Point of Care, Part 600-9006-10). The blood temperature was maintained between 33 and 35°C during the testing. For each test sample, a leak rate was measured at a normotensive pressure (120/80 mmHg) with a pulsatile rate of 72 pulses per minute. The needle-hole leak rate was measured as the blood loss over a 2-min period. For one sample, blood collection was terminated after a 1 min collection period due to a high blood loss rate for that sample.
P. Sergeant et al. / Interactive CardioVascular and Thoracic Surgery
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Table 1: Descriptive variables of the HS suture and the three study alternatives Material company code
Needle length (mm)
Suture size
Point shape
Needle curve
Needle diameter size (mil)
Needle type
N:S ratio
Suture material
HS suture EP8725H Polypropylene 1 8720H Polypropylene 2 XN8720H ePTFE suture 6N04B
13 13 13 13
5-0 5-0 5-0 CV-6
Taper Taper Taper Taper
3/8c 3/8c 3/8c 3/8c
10.4 13.7 11.8 13.8
C-1 C-1 C-1 TTc-13
1.84:1 2.41:1 2.06:1 1.4:1
Monofilament polypropylene Monofilament polypropylene Monofilament polypropylene Monofilament ePTFE
The needle diameters are in mil. 1 mil equals to 0.001 inch or 0.0254 mm. The N:S ratios can differ from other sources due to differences in measuring environments and conditions. N:S ratio: needle-to-suture ratio.
Table 2: sample
The data summary of the total leak rates by study
Study sample (n = 20)
Mean (ml/min)
SD (ml/min)
Max (ml/min)
Min (ml/min)
HS suture Polypropylene 1 Polypropylene 2 ePTFE suture
19.8 57.2 33.8 46.5
4.5 7.2 4.1 10.3
30.6 74.9 40.0 59.7
11.5 47.9 23.3 25.9
SD: standard deviation.
Statistical methods A one-way ANOVA (F-test) was used to compare the four test groups based on needle-hole leak rate. A two-sided 95% confidence interval for the difference in leak rates (ml/min) between each suture code was determined. A parametric analysis method was used to compute the confidence intervals. Each data set was determined to be normal using the Kolmogorov–Smirnov test.
Table 3: The data summary of the needle-hole leak rates by study sample Study sample (n = 20)
Mean (ml/min)
SD (ml/min)
Max (ml/min)
Min (ml/min)
HS suture Polypropylene 1 Polypropylene 2 ePTFE suture
0.63 1.94 1.14 1.56
0.13 0.23 0.14 0.34
0.96 2.50 1.42 2.09
0.38 1.60 0.83 0.81
Equipment calibration SD: standard deviation.
All test equipment used for this study had been calibrated and the calibration information has been recorded.
RESULTS The total leak rate (Table 2) of the HS suture was 19.8 ± 4.5 ml/min, versus 57.2 ± 7.2 ml/min for polypropylene 1, 33.8 ± 4.1 ml/min for polypropylene 2 and 46.5 ± 10.3 mil/min for the ePTFE suture. The needle-hole leak rate (Table 3) of the HS suture sample was 0.63 ± 0.13 ml/min compared with 1.94 ± 0.23 mil/min for polypropylene 1, 1.14 ± 0.14 mil/min for polypropylene 2 and 1.56 ± 0.34 mil/min for the ePTFE® suture. The HS suture showed a 67% reduction versus polypropylene 1, a 44% reduction versus polypropylene 2 and a 59% reduction versus ePTFE suture in the needle-hole leak rate. A one-way ANOVA (F-test) was used to compare the four test groups based on the needle-hole leak rate. This analysis shows that the needle-hole leak rate is significantly affected by the choice of suture (P < 0.001).
Table 4: The parametric two-sided 95% confidence intervals for the difference in suture-hole leak rates between the HS suture and polypropylene 1, polypropylene 2 and ePTFE suture Comparison groups
Results
HS suture versus polypropylene 1 HS suture versus polypropylene 2 HS suture versus ePTFE suture
1.19–1.42 0.45–0.56 0.79–1.06
A two-sided 95% confidence interval for the difference in leak rates (ml/min) between the HS suture and each test group shows that the difference in needle-hole leak rates when compared with
ORIGINAL ARTICLE
The blood loss was collected and weighed to establish a leak rate. The leak rate was calculated as the volume of blood collected over a period of time and recorded in millilitres per minute [i.e. Leak rate (ml/min) = weight of blood per minute (grams)/ blood density (grams/ml), assuming a blood density of 1.06 g of blood = 1 millilitre of blood]. Three replicates were tested for each test sample and the average of the three replicates was reported for the statistical analysis. Three samples were excluded from the study. This was due to the ACT measuring out of the acceptable range at the start of the sample. As a result, three extra samples were tested when the ACT was within range (one sample from the HS group and two samples from the ePTFE suture group).
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the HS suture are significantly different in favour of the HS suture for comparison with each suture group (Table 4).
COMMENT The primary goal of an anastomosis is to connect two vessels, without causing early or late complications. Some of these complications can be caused by the trauma of the needle perforation through the graft and the host. This trauma can be surgeon-, technique- or material-induced. Typical surgeon-induced criteria are the stabilization of the posture and obviously the hand during the anastomosis; but also the ability to rotate the needle holder with the fingers without any drift of the tip, just as the capacity to optimize needle–needle holder angle, to penetrate and exit the graft/host walls with an unlocked needle holder and in perpendicular fashion versus the wall but with a pathway respecting the curve of the needle. The parachute technique has the benefit of being less demanding on the surgeon’s technique but can increase the graft/host trauma through the ‘cheesewiring’ or ‘Gigli-saw’ effect when the two components are approximated. Another important technical criterion is the number of times the needle is grasped by forceps and needle holder, since each contact damages the coating. Damaging the coating can increase the needle drag as it passes through the wall. Finally, the suture/ needle combination will influence the trauma on the wall as a function of suture size, suture material, needle alloy, needle length, point geometry and the –N:S ratio or swage area. As early as 1984 [6] and 1987 [7], a 1:1 N:S ratio was considered an innovative improvement of suture configuration. Vessel wall trauma can have late effects by creating endothelial reaction. While postanastomotic bleeding is an issue in every anastomosis, it can become problematic in very long suture lines, in very calcified or fragile vessels, in situations of very high pressure, as when an extracorporeal membrane oxygenation is perfused through such an anastomosis, when intraoperative anticoagulation cannot be reversed, or when the comorbidity or the faith of the patient does not allow blood transfusion. Tissue adhesives and sealants are capable of addressing these issues, but at a financial and sometimes clinical cost. The introduction and implementation of polytetrafluoroethylene grafts has increased the focus on this issue [8]. Due to the absence of elasticity of the ePTFE graft, the needle-hole defect remains the same size of the needle after it is passed through. Several haemostats [9], sealants and adhesives have been proposed to solve this issue containing either porcine (gelatine), bovine (collagen, thrombin [10], albumin) or human [11] (serum albumin, pooled plasma) components or combinations thereof. In addition to cost, risks [12], such as allergic reactions, immunemediated coagulopathy and transmissions of viral infections, have prevented approval of some of them in some countries. The total leak rate of the HS suture was 19.8 ± 4.5 vs 57.2 ± 7.2 ml/min ( polypropylene 1), 33.8 ± 4.1 ml/min ( polypropylene 2) and 46.5 ± 10.3 mil/min (ePTFE® suture). An interesting observation on the total leak rates as observed in this study were the very small standard deviations, indicating the possibility of obtaining stable results, even in the presence of possible human, technical and material variability. They ranged from 12% to a maximum of 22% of the mean values. The largest standard deviations were observed with the ePTFE suture.
It was also observed that a considerable needle-hole leak rate difference was present between the different sutures, ranging from 45 to 68%. These differences are statistically significant, but more importantly they represent 14–37 ml less blood loss per minute, indicating that the possibilities of clinical benefit of the use of the HS suture for ePTFE graft anastomoses become apparent, even for a single anastomosis. Patients with an ePTFE graft interposition obviously have two such anastomoses. The use of the HS suture could avoid or reduce the need for blood transfusion and/or the application of sealants, adhesives or haemostats, thereby potentially reducing the likelihood of early or late infection, viral transmission or immunological reaction, shorten the operating-suite time, and possibly reduce the duration of intensive care unit and hospital stay.
Funding Serrey Consulting was compensated for the services performed in making the anastomoses and in writing the manuscript. Conflict of interest: Richard Kocharian, Babahai Patel, Matthew Pfefferkorn and John Matonick are employess of Ethicon, NJ, USA. Paul Sergeant is unpaid collaborator of Serrey Consulting.
REFERENCES [1] Choat JD, Maitta RW, Tormey CA, Wu YY, Snyder EL. Transfusion reactions to blood and cell therapy products. In: Hoffman R, Benz EJ Jr, Silberstein LE, Heslop HE, Weitz JI, Anastasi J (eds). Hematology: Basic Principles and Practice. 6th edn. Philadelphia, PA: Elsevier Saunders, 2013:chap 120. [2] Cata JP, Wang H, Gottumukkala V, Rueben J, Sessler DI. Inflammatory response, immunosuppression, and cancer recurrence after perioperative blood transfusions. Br J Anaesth 2013;110:690–701. [3] Blajchman M. Incidence and significance of the bacterial contamination of blood components. Dev Biol 2002;108:59–67. [4] Rohde JM, Dimcheff DE, Blumberg N, Saint S, Langa KM, Kuhn L et al. Health care-associated infection after red blood cell transfusion. JAMA 2014;311:doi:10.1001/jama.2014.2726. [5] Yoshida WB, Naresse LE, Angeleli Aparecida YO, Lastoria S, Defaveri J, Curi PR et al. The relationship between suture number and the healing process of end-to-end arterial anastomosis. Acta Cirurgica Brasileira 1997;12: 89–93. [6] Lourie GM, Seaber AV, Urbaniak JR. Microanastomotic response to needle and suture size. J Reconstr Microsurg 1984;1:135–8. [7] Miller CM, Sangiolo P, Jacobson JH. Reduced anastomotic bleeding using new sutures with a needle-suture diameter of one. Surgery 1987;101: 156–60. [8] Towler MA, Tribble CG, Pavlovich LJ, Milam JT, Morgan R, Edlich RF. Biomechanical Performance of new vascular sutures and needles for use in polytetrafluoroethylene grafts. J Appl Biomater 1993;4:87–95. [9] Spotnitz W. Fibrin sealant: the only approved hemostat, sealant and adhesive—a laboratory and clinical perspective. ISRN Surg 2014, Article ID 203943 http://dx.doi.org/10.1155/2014/203943. [10] Taylor LM, Mueller-Velten G, Koslow A, Hunter G, Naslund T, Kline R. Prospective randomized multicenter trial of fibrin sealant versus thrombin-soaked gelating sponge for suture- or needle-hole bleeding from polytetrafluoroethylene femoral artery grafts. J Vasc Surg 2003;38: 766–71. [11] Schenk WG, Burks SG, Gagne PJ, Kagan SA, Lawson JH, Spotnitz WD. Fibrin sealant improves hemostasis in peripheral vascular surgery: a randomized prospective trial. Ann Surg 2003;237:871–6. [12] Hino M, Ishiko O, Honda KI, Yamane T, Ohta K, Takubo T et al. Transmission of symptomatic parvovirus B19 infection by fibrin sealant used during surgery. Br J Haematol 2000;108:194–5.
Interactive CardioVascular and Thoracic Surgery 22 (2016) 813–816 doi:10.1093/icvts/ivw042 Advance Access publication 25 February 2016
Cite this article as: Sergeant P, Kocharian R, Patel B, Pfefferkorn M, Matonick J. Needle-to-suture ratio, as well as suture material, impacts needle-hole bleeding in vascular anastomoses. Interact CardioVasc Thorac Surg 2016;22:813–16.
Needle-to-suture ratio, as well as suture material, impacts needle-hole bleeding in vascular anastomoses Paul Sergeanta,*, Richard Kocharianb, Bababhai Patelc, Matthew Pfefferkornd and John Matonickd a b c d
Serrey Consulting, Sint Joris Winge, Belgium Medical Affairs, Ethicon, Inc., Somerville, NJ, USA Clinical Development, Ethicon, Inc., Somerville, NJ, USA Advanced Modeling Group, Preclinical Research, Ethicon, Inc., Somerville, NJ, USA
* Corresponding author. Serrey Consulting, Reigersweide 16, 3390 Sint Joris Winge, Belgium. Tel: +32-475742771; e-mail: [email protected] (P. Sergeant).
Abstract OBJECTIVES: The purpose of this study was to examine the influence of material variables on needle-hole bleeding in vascular anastomoses. Material variables include suture size, needle-tip geometry and diameter, needle coating, suture material and coating and swage area. We attempted to determine whether particular suture material and a reduced needle-to-suture ratio (N:S ratio) could reduce the vessel wall defect and reduce needle-hole bleeding, without changing the suture diameter used for the anastomosis. METHODS: A comparative analysis was made of the needle-hole leak rate in end-to-end anastomoses of an ePTFE®-ePTFE® vascular graft with a PROLENE® polypropylene suture with HEMO-SEAL™ technology (HS, 1.84:1 N:S ratio), standard PROLENE® polypropylene suture ( polypropylene 1, 2.41:1 N:S ratio), an alternate standard PROLENE® polypropylene suture ( polypropylene 2, 2.06:1 N:S ratio) and a GORE-TEX™ ePTFE® suture (ePTFE® suture, 1.4:1 N:S ratio) in an ex vivo cardiopulmonary bypass pulsatile flow loop model using heparinized porcine blood. Testing was completed within the model with an activated clotting time between 250 and 500 s, at near normothermia (33–35°C) and at normotensive pressure levels (120/80 mmHg). A sample size of n = 20 was completed for each group. RESULTS: The average total sample leak rate was 19.8 ± 4.5 ml/min for the HS suture, 57.2 ± 7.2 ml/min for polypropylene 1, 33.8 ± 4.1 ml/min for polypropylene 2 and 46.5 ± 10.3 ml/min for the ePTFE suture. The average needle-hole leak rates were 0.63 ± 0.13 ml/min for the HS suture, 1.94 ± 0.23 ml/min for polypropylene 1, 1.14 ± 0.14 ml/min for polypropylene 2 and 1.56 ± 0.34 ml/min for the ePTFE® suture. A two-sided 95% confidence interval for the difference in leak rates showed that there were significant differences (44–67% reduction) in favour of the HS suture when compared with the alternative needles with the same suture material and different N:S ratios, and also a reduction (59%) compared with the sample with smaller N:S ratios but different suture material. CONCLUSIONS: The N:S ratio as well as the physical characteristics of the suture material are important factors in reducing needle-hole bleeding in vascular anastomoses. Keywords: Needle technology • Swage area • Bleeding • Needle-to-suture ratio
INTRODUCTION Each time a needle penetrates a blood vessel, trauma is created in the wall, often only visible decades later when intimal proliferation has occurred. Bleeding through the suture holes is a more quantifiable early surrogate for trauma, visible in real time. Bleeding that results in the need for transfusion may have immunological and infectious consequences, which may be significant and are known to increase the risk of the procedure and the cost of hospitalization. The most frequently cited immunological reactions after blood transfusions are acute and delayed haemolytic reactions [1, 2], febrile non-haemolytic reactions, allergic reactions, post-transfusion purpura and transfusion-associated acute lung injury. Additionally,
the need for blood transfusion is a risk factor for surgical-site and general infection [3, 4]. The trauma and bleeding of the blood vessel are influenced by patient, surgeon, needle and suture material variables. Patient variables include the level of anticoagulation or antiaggregation, blood pressure, vessel wall and stability of the anastomotic site. Surgeon variables include the stability of posture, hand, needle holder and needle, rotational capacity of the needle holder by the surgeon, motion when unlocking the needle holder, the needle angle and entry/exit pathway curve and control and anastomotic technique. Suture variables include the needle diameter and length, needle curvature, suture size, the needle and suture coating,
© The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ORIGINAL ARTICLE
Received 12 November 2015; received in revised form 5 January 2016; accepted 18 January 2016
814
P. Sergeant et al. / Interactive CardioVascular and Thoracic Surgery
needle-tip geometry and the swage area and needle:suture ratio (N:S ratio). Needle diameter is the width of the wire of the finished needle in combination with the thickness of the coating. Needle curvature is expressed in degrees of the subtended arc. Needle length is the arc length of the needle measured at the centre of the wire’s cross section. N:S ratio is the relationship between the diameter of the needle and the diameter of the suture at its region of largest diameter. Theoretically, the closer the N:S ratio approaches 1:1, lower rates of bleeding should be obtained because the suture fills the hole made by the needle.
METHODS Testing method and materials used The suture-hole leak rate of the HEMO-SEAL™ technology (HS) suture, which has a reduced N:S ratio (Fig. 1), was compared with suture-hole leak rate of three commercially available sutures of similar size, but with various N:S ratios ( polypropylene 1 and polypropylene 2) and suture material (ePTFE) (see Table 1). The suturehole leak rate was measured after completing an end-to-end ePTFE to ePTFE® vascular graft anastomoses in an ex vivo cardiopulmonary bypass pulsatile flow loop with heparinized porcine blood. The HS suture has been engineered to include a suture with a tapered region at the needle attachment point with a smaller diameter than that of the rest of the suture, allowing it to be swaged to smaller diameter needles. The ePTFE® suture is a monofilament suture with a porous microstructure that is 50% air by volume. Polypropylene 1 is a 5-0 PROLENE polypropylene suture with a C-1 needle. Polypropylene 2 is a CE-marked 5-0 PROLENE polypropylene suture with the C-1
Figure 1: The different swage areas: A for a standard PROLENE® suture with stainless steel C-1 needle (14 mil diameter, B for a HEMO SEAL® Prolene suture, Everpoint® C-1 needle (10.5 mil diameter).
needle, and the ePTFE® suture is a CV-6 Gore-Tex ePTFE suture with a TTc-13 needle. An ePTFE graft was cut to a length of 8 cm. The graft was then mounted to a plastic fitting on both ends, secured in place with tubing clamps and then transected at its mid-point. A complete end-to-end anastomosis was created using a simple continuous suture pattern with one of the test sutures described above. All anastomoses were performed by the same surgeon. The surgeon’s hands were stabilized, as appropriate in modern surgery, and a new needle holder with rounded handle and open latch (Scanlan® 6006–129), and new forceps (KLS Martin 12-254-17-07) were used for this experiment. The number of needle holes used in each anastomosis was recorded in the data sheets. It was attempted to have a 1 mm space between each needle hole [5]. The number of needle holes was used to calculate the needle-hole leak rate for each anastomosis. The total sample size of each study group was 20. The sequence of each anastomosis for this assessment was based on a randomization schedule and the surgeon was blinded from the suture choice except where (as with ePTFE®) the difference was visible with the naked eye. Prior to the acceptance of each anastomosis into the study, the anastomosis was pressure tested with saline at a static pressure of 120 mmHg to ensure that the leakage present along the suture line was from the suture holes only and not from the inter-suture spacing. Only one sample required an additional interrupted suture. A pulsatile ex vivo cardiopulmonary bypass model used a series of pumps and chambers to create, control and maintain blood pressure throughout the system. The model consists of a reservoir to filter blood returning from the test article, a computerintegrated data acquisition system, oxygenator and heat exchanger. Flow impedance and volume partitioning adjustments are present to allow for fine adjustment of blood volume flow and pressure control. To represent clinical conditions, a difference of 40 mmHg between the systolic and diastolic pressure was generated, resulting in a pulse pattern of 120/80 mmHg. The blood used within the model was donor porcine blood (Lampire Biological Laboratories, Pipersville, PA, USA). This blood was received heparinized, with 10 000 units of heparin per litre of blood, added upon removal from the donor animal. The blood was stored per the supplier’s recommendations and was used prior to expiration. The heparin level within the heparinized porcine blood was reversed to a target activated clotting time (ACT) of 250–500 s, consistent with clinical, non-experimental, levels when performing anastomoses with similar materials and similar clinical settings. Protamine sulphate (10 mg/ml) was slowly added to the circulating blood to reverse the effects of the heparin. An ACT measurement was performed at regular intervals to ensure the ACT level was within the acceptable range. The ACT was measured with a VetScan i-STAT Portable Handheld Unit (Abbott Point of Care) and an i-STAT ACT Celite Cartridge (Abbott Point of Care, Part 600-9006-10). The blood temperature was maintained between 33 and 35°C during the testing. For each test sample, a leak rate was measured at a normotensive pressure (120/80 mmHg) with a pulsatile rate of 72 pulses per minute. The needle-hole leak rate was measured as the blood loss over a 2-min period. For one sample, blood collection was terminated after a 1 min collection period due to a high blood loss rate for that sample.
P. Sergeant et al. / Interactive CardioVascular and Thoracic Surgery
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Table 1: Descriptive variables of the HS suture and the three study alternatives Material company code
Needle length (mm)
Suture size
Point shape
Needle curve
Needle diameter size (mil)
Needle type
N:S ratio
Suture material
HS suture EP8725H Polypropylene 1 8720H Polypropylene 2 XN8720H ePTFE suture 6N04B
13 13 13 13
5-0 5-0 5-0 CV-6
Taper Taper Taper Taper
3/8c 3/8c 3/8c 3/8c
10.4 13.7 11.8 13.8
C-1 C-1 C-1 TTc-13
1.84:1 2.41:1 2.06:1 1.4:1
Monofilament polypropylene Monofilament polypropylene Monofilament polypropylene Monofilament ePTFE
The needle diameters are in mil. 1 mil equals to 0.001 inch or 0.0254 mm. The N:S ratios can differ from other sources due to differences in measuring environments and conditions. N:S ratio: needle-to-suture ratio.
Table 2: sample
The data summary of the total leak rates by study
Study sample (n = 20)
Mean (ml/min)
SD (ml/min)
Max (ml/min)
Min (ml/min)
HS suture Polypropylene 1 Polypropylene 2 ePTFE suture
19.8 57.2 33.8 46.5
4.5 7.2 4.1 10.3
30.6 74.9 40.0 59.7
11.5 47.9 23.3 25.9
SD: standard deviation.
Statistical methods A one-way ANOVA (F-test) was used to compare the four test groups based on needle-hole leak rate. A two-sided 95% confidence interval for the difference in leak rates (ml/min) between each suture code was determined. A parametric analysis method was used to compute the confidence intervals. Each data set was determined to be normal using the Kolmogorov–Smirnov test.
Table 3: The data summary of the needle-hole leak rates by study sample Study sample (n = 20)
Mean (ml/min)
SD (ml/min)
Max (ml/min)
Min (ml/min)
HS suture Polypropylene 1 Polypropylene 2 ePTFE suture
0.63 1.94 1.14 1.56
0.13 0.23 0.14 0.34
0.96 2.50 1.42 2.09
0.38 1.60 0.83 0.81
Equipment calibration SD: standard deviation.
All test equipment used for this study had been calibrated and the calibration information has been recorded.
RESULTS The total leak rate (Table 2) of the HS suture was 19.8 ± 4.5 ml/min, versus 57.2 ± 7.2 ml/min for polypropylene 1, 33.8 ± 4.1 ml/min for polypropylene 2 and 46.5 ± 10.3 mil/min for the ePTFE suture. The needle-hole leak rate (Table 3) of the HS suture sample was 0.63 ± 0.13 ml/min compared with 1.94 ± 0.23 mil/min for polypropylene 1, 1.14 ± 0.14 mil/min for polypropylene 2 and 1.56 ± 0.34 mil/min for the ePTFE® suture. The HS suture showed a 67% reduction versus polypropylene 1, a 44% reduction versus polypropylene 2 and a 59% reduction versus ePTFE suture in the needle-hole leak rate. A one-way ANOVA (F-test) was used to compare the four test groups based on the needle-hole leak rate. This analysis shows that the needle-hole leak rate is significantly affected by the choice of suture (P < 0.001).
Table 4: The parametric two-sided 95% confidence intervals for the difference in suture-hole leak rates between the HS suture and polypropylene 1, polypropylene 2 and ePTFE suture Comparison groups
Results
HS suture versus polypropylene 1 HS suture versus polypropylene 2 HS suture versus ePTFE suture
1.19–1.42 0.45–0.56 0.79–1.06
A two-sided 95% confidence interval for the difference in leak rates (ml/min) between the HS suture and each test group shows that the difference in needle-hole leak rates when compared with
ORIGINAL ARTICLE
The blood loss was collected and weighed to establish a leak rate. The leak rate was calculated as the volume of blood collected over a period of time and recorded in millilitres per minute [i.e. Leak rate (ml/min) = weight of blood per minute (grams)/ blood density (grams/ml), assuming a blood density of 1.06 g of blood = 1 millilitre of blood]. Three replicates were tested for each test sample and the average of the three replicates was reported for the statistical analysis. Three samples were excluded from the study. This was due to the ACT measuring out of the acceptable range at the start of the sample. As a result, three extra samples were tested when the ACT was within range (one sample from the HS group and two samples from the ePTFE suture group).
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the HS suture are significantly different in favour of the HS suture for comparison with each suture group (Table 4).
COMMENT The primary goal of an anastomosis is to connect two vessels, without causing early or late complications. Some of these complications can be caused by the trauma of the needle perforation through the graft and the host. This trauma can be surgeon-, technique- or material-induced. Typical surgeon-induced criteria are the stabilization of the posture and obviously the hand during the anastomosis; but also the ability to rotate the needle holder with the fingers without any drift of the tip, just as the capacity to optimize needle–needle holder angle, to penetrate and exit the graft/host walls with an unlocked needle holder and in perpendicular fashion versus the wall but with a pathway respecting the curve of the needle. The parachute technique has the benefit of being less demanding on the surgeon’s technique but can increase the graft/host trauma through the ‘cheesewiring’ or ‘Gigli-saw’ effect when the two components are approximated. Another important technical criterion is the number of times the needle is grasped by forceps and needle holder, since each contact damages the coating. Damaging the coating can increase the needle drag as it passes through the wall. Finally, the suture/ needle combination will influence the trauma on the wall as a function of suture size, suture material, needle alloy, needle length, point geometry and the –N:S ratio or swage area. As early as 1984 [6] and 1987 [7], a 1:1 N:S ratio was considered an innovative improvement of suture configuration. Vessel wall trauma can have late effects by creating endothelial reaction. While postanastomotic bleeding is an issue in every anastomosis, it can become problematic in very long suture lines, in very calcified or fragile vessels, in situations of very high pressure, as when an extracorporeal membrane oxygenation is perfused through such an anastomosis, when intraoperative anticoagulation cannot be reversed, or when the comorbidity or the faith of the patient does not allow blood transfusion. Tissue adhesives and sealants are capable of addressing these issues, but at a financial and sometimes clinical cost. The introduction and implementation of polytetrafluoroethylene grafts has increased the focus on this issue [8]. Due to the absence of elasticity of the ePTFE graft, the needle-hole defect remains the same size of the needle after it is passed through. Several haemostats [9], sealants and adhesives have been proposed to solve this issue containing either porcine (gelatine), bovine (collagen, thrombin [10], albumin) or human [11] (serum albumin, pooled plasma) components or combinations thereof. In addition to cost, risks [12], such as allergic reactions, immunemediated coagulopathy and transmissions of viral infections, have prevented approval of some of them in some countries. The total leak rate of the HS suture was 19.8 ± 4.5 vs 57.2 ± 7.2 ml/min ( polypropylene 1), 33.8 ± 4.1 ml/min ( polypropylene 2) and 46.5 ± 10.3 mil/min (ePTFE® suture). An interesting observation on the total leak rates as observed in this study were the very small standard deviations, indicating the possibility of obtaining stable results, even in the presence of possible human, technical and material variability. They ranged from 12% to a maximum of 22% of the mean values. The largest standard deviations were observed with the ePTFE suture.
It was also observed that a considerable needle-hole leak rate difference was present between the different sutures, ranging from 45 to 68%. These differences are statistically significant, but more importantly they represent 14–37 ml less blood loss per minute, indicating that the possibilities of clinical benefit of the use of the HS suture for ePTFE graft anastomoses become apparent, even for a single anastomosis. Patients with an ePTFE graft interposition obviously have two such anastomoses. The use of the HS suture could avoid or reduce the need for blood transfusion and/or the application of sealants, adhesives or haemostats, thereby potentially reducing the likelihood of early or late infection, viral transmission or immunological reaction, shorten the operating-suite time, and possibly reduce the duration of intensive care unit and hospital stay.
Funding Serrey Consulting was compensated for the services performed in making the anastomoses and in writing the manuscript. Conflict of interest: Richard Kocharian, Babahai Patel, Matthew Pfefferkorn and John Matonick are employess of Ethicon, NJ, USA. Paul Sergeant is unpaid collaborator of Serrey Consulting.
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