Abdominal Aortic Aneurysm is the medical condition in which the abdominal aorta is enlarged in such as way that it becomes more than 3cm or 50% larger in comparison to the normal diameter (Di Achille et al.2017). This medical condition does not show any symptoms until the enlarged aorta is ruptured. In this assignment, the pathophysiology of the Abdominal Aortic Aneurysm is to be discussed along with two medical intervention are to be critically analysed that can be used for its treatment. The advantages and disadvantages along with limitation related to the medical interventions for treatment of the condition are also to be discussed.
In order to develop information regarding Abdominal aortic aneurysm (AAA), various journals and articles are to be identified, reviewed and analysed by searching databases such as MEDLINE, Google Scholar, CINCHL and others. These databases are to be used as they offer extensive and essential updated literature regarding nursing, health sciences, biomedical, complementary medicines and others (health.ebsco.com, 2018; scholar.google.com, 2018). The updated articles are essential to be used as it contains recent evidence regarding any topic that helps to develop knowledge regarding mechanism and limitations related to health disorder, medical intervention and others for the patients (Gorst et al. 2016). Thus, the articles within 8 years (2011-2019) are chosen to develop knowledge regarding AAA. Moreover, the articles written in English has been chosen as it is the preferred language to understand the meaning of the information.
The pathogenesis of abdominal aortic aneurysm (AAA) is seen to be multi-factorial in nature but in brief, it is the degradation of main structural proteins like collagen and elastin by homocysteine that results to weakness the wall of the aorta leading to subsequent dilation resulting to form aneurysm. The HyperHcy is seen to show enhanced involved in the process of development of Abdominal aortic aneurysm through various mechanisms (Han et al. 2016). As mentioned by Katsiki et al. (2017), homocysteine causes endothelial dysfunctioning through mechanisms that are closely attributed to oxidative stress. The event come before the manifestation of vascular disease and its involvement is made robust by the fact that improper functioning of endothelial vasodilator is induced by the action of hyperHcy (Liu et al. 2016).
One of the mechanisms being attributable to oxidative stress is the process in which the effect of hyperHyc causes lower production of nitric oxide (NO). This mainly occurs through increased levels of asymmetric dimethyl-arginine (ADMA) which acts as a strong inhibitor of endothelial nitric oxide synthase. The NO causes vessel homeostasis through inhibition of contraction and growth of vascular smooth muscle, aggregation of platelet and adhesion of leukocyte to the endothelium. This leads to over-production of oxidative free radicals, as a result, it is seen to induce injury in the intimal region, activate elastase as well as increases calcium deposition that leads to rupture of the aorta causing abdominal aortic aneurysm. Thus, these changes lead to show development of ulceration, thrombosis, calcification and ruptures around the layer of abdominal aorta (Bradley et al. 2016; Emeto et al. 2016).
The other mechanism informs that hyperHcy by enhancing proteolysis leads to develop abdominal aortic aneurysm. This is because in normal aorta the walls of the artery have properly structured elastin, collagen and smooth muscles which helps the aorta to bear most of the stress on their wall which acts as strong indispensable protection to limit expansion. However, the histological features of abdominal aortic aneurysm inform that the aneurismal wall of the aorta has no efficiency to ensure this protection due to degenerated and fragmented elastin along with degraded collagen. Thus, this condition leads to medical attenuation to show reduce tensile strength in case of the vascular disease Chan and Cheng, 2017; Toghill et al. 2015
The metalloproteinases (MMP) are seen to be widely related to the proteolytic system that is related to the pathogenesis of abdominal aortic aneurysm. This is evident as they cause degradation of collagen and elastin in the aorta. The degradation of elastin is connected with beginning and expansion of aneurysm and the destruction of collagen are seen to be responsible towards causing abdominal aortic aneurysm (AAA) by making the walls of the aorta lose elasticity making them prone to increased blood pressure leading them to rupture. The MMP-9 is widely considered metalloproteinases which cause initiation, expansion and rupture of aneurysm. The MMP-12 and MMP-2 which are known as macrophage elastase are seen to found at higher levels in the tissues of the aneurysmal aorta. The high concentration of MMP-2 is mainly found in the smaller AAA which suggests that it has the early role in formation of AAA whereas MMP-12 is seen to be expressed at increased level in the tissues that are present along the edge of the AAA indicating their role in the initiation of AAA (Tsai et al. 2016; Ciavarella et al. 2015).
The dynamic of blood flow is also seen to influence AAA as it has predilection towards the infranetal aorta. The mechanical characteristics and histological structure of the infranetal aorta is different from the thoracic aorta. Thus, the tension of the blood flow on the wall of the abdominal aorta is more than the wall of thoracic aorta. Further, distensibility and elasticity also decrease with age which results in gradual expansion of the mentioned segment. Therefore, patients who have arterial hypertension have increased intraluminal pressure which leads to the pathological process for initiation of AAA as a result of hemodynamics (Drewe et al. 2017; Di Achille et al. 2017; Tasso et al. 2018). (Refer to Appendix 1)
The EVAR and open surgery are the most prominent medical intervention chosen for resolving abdominal aortic aneurysm (AAA) in patients. As mentioned by Patel et al. (2016), EVAR is a form of endovascular surgery used for the treatment of pathology of the aorta in AAA patients. The EVAR process is executed through regional, general or local anaesthesia. The patient in EVAR process is mainly placed in supine position and the abdomen and both the groins are prepped and draped. The femoral artery is accessed bilaterally through cutdown of femoral artery. The closure device is seen to be introduced before insertion of the endograft. The access to the radial artery is made in case of body floss maneuver or difficulty is experienced in introducing the contralateral limb gate present in the endograft. The patients are provided heparin with the target to achieve clotting time more than or equal to 300 sec. The anticoagulation target is maintained until repair is done at the cutdown of the femoral artery and verification of the distal pulses is done (www.ctsnet.org, 2011).
The guidewires initiating bilateral access are advanced by using fluoroscopic guidance over the lesion present in the aorta. After this step, insertion of 9F introducer sheath is introduced over the primary access guidewire. Later, introduction of multipurpose catheter is done for facilitating guidewire exchange to stiff wire. Further, an IVUS catheter is used over stiff guidewire to inspect the abdominal aorta. The catheter is used by the surgeon for scanning the entire aorta in the abdominal region as well as helps to map out the iliac vessels (www.ctsnet.org, 2011). The pigtail catheter is used for performing an aortogram of the iliac arteries and abdominal aorta and after this; the proximal neck of the aorta is examined. The diameter and length of the distal and proximal neck of the aorta are measured by using CT scan, intraoperative IVUS and angiogram. The details are used for determining the length and diameter of the arteries of the trunk and iliac are chosen. On the side of the ipsilateral limb and endograft device’s main trunk an 18-24F sheath is inserted gradually and a 12-17F sheath on the contralateral side (www.ctsnet.org, 2011).
In the later stages, heparin solution is used to flush the main trunk which later advanced in the proximal neck just positioned below the lowest renal artery and it is aligned so that the contralateral limb gate is easily accessible. Later, the endograft’s contralateral limb is inserted over another stiff guidewire that is introduced from the extent of contralateral femoral artery. After deploying the contralateral limb, further evaluation is to be done to check for any more aortic cuffs or iliac limb extenders. This is because it is essential that it covers the entire length present between internal iliac artery and lowest renal artery. The grafts are then ballooned as recommended by manufacturer’s IFU. Later, an IVUS examination is performed for detecting any circumferential graft malposition to the proximal or distal landing zone as it leads to endoleak. Further, an angiogram is executed and after its completion, surgeon removes the introducer sheath while abandoning the wire in the aorta. In case the patients show no concern for further angiogram and are haemodynamically stable, the guidewires are removed and in a standard fashion repairs the femoral artery. The distal pulses are examined and the heparin is reversed along with the sterile catheter are later disposed (www.ctsnet.org, 2011).
In open surgery for treatment of abdominal aortic aneurysm (AAA), the doctor used an endograft tube for replacing the bulging and weak section of the aorta in the abdomen. In this surgery, general anaesthesia is done to the patient. The surgeon makes an incision in the side of the abdomen and then put clamps on the aorta present below and above the aneurysm. This is done to restrict the blood flow to area while the surgeon is executing the surgery. After this, the surgeon removes the part of the aneurysm and attaches the endograft to the aorta. However, in some cases, the aneurysm wall is kept and the graft is placed inside the wall of the aneurysm. The surgeon then ensures that the aorta is properly repaired and removes the clamps previously placed on the aorta to allow blood flow. After this, the surgeon stitches the site in traditional way to close the incision in the abdomen (Ultee et al. 2016; Phillips et al. 2017).
The EVAR and the open surgery are seen to the two interventions used to treat abdominal aortic aneurysm. However, there are different advantages and disadvantages related to both the intervention in the process. As mentioned by Sharifpour and Hemani (2018), the use of EVAR is beneficial in case of treatment of abdominal aortic aneurysm as it offers less physiological disturbance to the patient. This is evident as in EVAR local anaesthesia is done and minimally invasive surgical technique is used that includes smaller incision. As argued by Brinkmann et al. (2016), physiological disturbance as a result of surgery techniques often causes organ failure, neurodegeneration and other issues among the patients. This leads them to experience negative health conditions creating barriers for improved health outcome. As stated by Kalender et al. (2018), the advantage of EVAR is that causes less blood loss and reduced pain while treatment of abdominal aortic aneurysm in patients. This is because unlike open surgery in this technique minimal damage to the tissues are made for executing the treatment which causes less pain and blood. As criticised by Botu et al. (2018), increased blood loss and pain during surgery may make the patients avoid involving into the treatment as it may be fatal for them. This is evident as blood is the main component that carries oxygen and nutrients to different tissues and organs of the body for their proper functioning. Thus, loss of extensive amount of blood causes organ failure leading to death of the individuals.
The other advantage of EVAR is that it is cost-effective and causes less hospital stay as patients are often released after 2 days (Shaw et al. 2018). This is because in this process the patients heal faster and lead normal life with ease. As asserted by Törnqvist et al. (2015), EVAR is disadvantageous as it requires lifelong surveillance by duplex ultrasound or CT scan. This makes the process hectic for the patient to bear as they have to continuously undergo surveillance even after the EVAR treatment for ensuring proper health condition. As argued by Chung et al. (2015), EVAR causes long-term condition such as endoleak which is referred to the condition in which persistent blood flow is seen outside the lumen of any endoluminal graft in the vascular segment or the aneurysm sac caused as a result of use of device for EVAR. There are different types of endoleak caused as a result of EVAR in treatment of AAA which often leads to cause the cavity pressure close to the individual’s systematic pressure which results to create a stress on the wall of AAA leading to elevate the level of nonstented AAA. This leads to render the implants made in the EVAR for protection of AAA from rupture useless (Coelho et al. 2016). Thus, EVAR is disadvantageous from this aspect as the condition leads to create further reintervention for AAA patients along with increases their morbidity and mortality rate.
The advantage of open surgery over EVAR in case of abdominal aortic aneurysm (AAA) is that there is less incidence of presence of endoleak in this technique. This is because in open surgery the surgeon makes a detailed incision in the tummy for replacing the affected section of the aorta with the graft. Thus, the surgeon has proper and detailed practical view of the region surrounding the affecting part of the aorta which avoid them to miss any endoleaks remain being untreated condition (Samoila and Williams, 2018). However, in EVAR the surgeon has a virtual view of the area based on which the grafts are implanted making it difficult for them to properly identify any endoleak cause while using devices for EVAR (Coelho et al. 2016). The other advantage of open surgery for abdominal aortic aneurysm is that the patients do not require long-term surveillance as the implanted graft are seen to work well for the rest of their lives (Schechter et al. 2017).
The disadvantage of open surgery is that increased blood loss may happen due to increased invasion made during the surgery leading to be fatal for the patient (Mathur et al. 2016). Moreover, in open surgery for AAA, there is increased risk of causing erectile dysfunction in men (Majd et al. 2016). This is because the during surgery the incision along the anterior surface of the aorta that is placed above the left iliac artery is able to damage nerve bundles that initiate from the spinal cord results to diminished eliminated innervations. The diminished stimulation of the nerve is seen to impair vascular response as a result of arteriopathy of the distal branches of the hypogastric aorta and the aorta itself, in turn, resulting in impotency or erectile dysfunction (Murphy et al. 2018). The disadvantage is not seen in female because the sexual sensation is more dependent on the endo-fascially prudent nerve rather on the nerve plexus in the pre-aortic region (Murphy et al. 2018). The other disadvantage of open surgery for abdominal aortic aneurysm (AAA) is that it may cause increased physiological disturbances on the patient as a result of general anaesthesia. This is because in general anaesthesia the patient’s protective and vital senses are depressed which makes them unable to inform disturbances to be avoided for physiological relief during the surgery (Murphy et al. 2018).
In order to treat patients suffering from abdominal aortic aneurysm (AAA), often EVAR is preferred over open surgery. However, both the processes are seen to have certain limitations which make them risky for the patients to be used. As stated by Ultee et al. (2016), limitation of open surgery intervention is that it leads to create injury to the gastrointestinal system which may occur due to interruption of the hypogastric artery through occlusion during the open surgery process. This leads to hinder bowel movement in AAA patients. As argued by Antoniou et al. (2016), graft-migration is one of the major limitations of EVAR intervention. This is evident as in many cases it is been informed that the endoprosthetic device known as the stent-graft used in the process get displaced from its original site where it has been attached in AAA patients to protect the aorta from rupturing. (Refer to Appendix 2)
The other limitation of the EVAR intervention in AAA patients is that it causes renal injury leading to kidney damage in individuals suffering from AAA. This limitation mainly occurs in case of EVAR intervention for AAA patients when the stent-graft is fixed in suprarenal position of the body or as a result of use of improper contrast medium in the process (Jhaveri et al. 2017). However, temporary ischemia may occur due to clamping of vessel during the pararenal AAA surgery leading to acute renal failure in patients (Hoshina et al. 2017). Thus, it also acts as a limitation for the open surgery in AAA patients and it is found that this limitation is seen to be more prominent in case of open surgery intervention in comparison to EVAR for the AAA patients. It is evident from the study of Tang et al. (2017) where it is mentioned that from the total survey participants it is found that 42.8% AAA patients with open surgery intervention faced renal failure in comparison to 27.1% patients who had undergone EVAR intervention for AAA.
The limitation of EVAR intervention is that it may lead the AAA patients to develop limb ischemia after the intervention in which sudden reduction of blood flow to the limb is experienced. This condition leads the patients to experience pain, pallor and paralysis of the leg (Itoga et al. 2018). Moreover, various anatomical constraints such as inadequacy of proximal aneurysm neck in AAA patients and others act as a limitation for the success of the EVAR intervention in AAA patients. This is evident as it is found that patients with less than 10 mm aortic neck have 4-fold increased risk of experiencing proximal endoleak with EVAR intervention within one month of the surgery (Jackson et al. 2012). The limitation of open surgery for AAA patients is that it leads to heart attract or irregular heart rhythms. This is because during surgery high amount of catecholamine is produced that causes haemodynamic stress and vasoconstriction resulting in increased oxygen demand by the myocardium. It leads to preoperative myocardial damage when the increased demand for oxygen is not meet. Apart from the stress experienced during the open surgery haemodynamic fluctuations are also experienced leading to myocardial damage in AAA patients (Galyfos et al. 2014). The other limitation of open surgery for AAA patients is that it may lead to cause spinal cord injury to them during the surgical process (Arora and Hosn, 2019).
The above discussion informs that abdominal aortic aneurysm (AAA) is localised increase of the aorta in the abdomen. The pathophysiology of the AAA informs that homocysteine through proteolysis, matrix metalloprotease and others, haemodynamics and others are responsible for causing the disorder. The EVAR and open surgery are two intervention used in the treatment of the disorder. The advantage of using EVAR is that it offers less stress, lower hospital stay and others for the patients but it has disadvantages such as it gives rise of endoleak, require continuous surveillance of the patients and others. In open surgery, the advantage is that no endoleak are experienced and do not require surveillance after treatment but the disadvantage is that it causes increased physiological stress, wound infection and others. The limitation of EVAR is that it makes patients suffer from kidney damage, graft-migration, limb ischemia and others after the surgery. In case of open surgery, the limitations are that the patients suffer from heart complications, kidney damage and others.
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