Overview

From open surgery to minimally invasive procedures and even endourology, vascular complications truly span the spectrum of urologic interventions and can result in significant short- and long-term morbidity and mortality. This chapter will discuss techniques and approaches to preventing, identifying, and managing intraoperative and postoperative vascular complications in urology and is intended to be a broad overview of the topic. While the chapter will reference laparoscopic, robotic, and endourologic concepts and injuries, the majority of this discussion will focus on traditional open surgical techniques, and the reader is directed to the respective chapters focusing on these other modalities for further information.

Representing 40% of all major intraoperative and postoperative laparoscopic urologic complications, hemorrhage from vascular injury is the most common cause of morbidity and mortality in the perioperative period. While the exact nature of these injuries varies with the specific case and surgical approach, the incidence of hemorrhage requiring transfusion reported in the literature varies from 0.3% for percutaneous nephrolithomy to 52% in one cohort undergoing radical retropubic prostatectomy. As with any surgical procedure, complication rates vary with the nature of the procedure, patient comorbidities and anatomy, and surgeon experience. Interestingly, while intraoperative blood loss was strongly inversely correlated with surgeon experience, major vascular injuries appeared to occur with equal frequency in both novice and experienced surgeons. This finding underscores the need for all surgeons, even those with significant experience, to follow key surgical principles such as careful tissue handling and meticulous dissection.

If a catastrophic vascular injury does indeed occur, surgeons must be willing to act decisively and take appropriate steps to control the bleeding and prevent exsanguination. Often, this includes rapid conversion of minimally invasive procedures to open surgery for direct control and subsequent repair of bleeding. Furthermore, these situations require clear and constant communication with the anesthesia team should it be necessary to implement aggressive resuscitation measures with intravenous fluids, blood products, and vasoactive medications. Even if the senior urologic surgeon is experienced in vascular repair, emergent intraoperative consultation to vascular surgery is often prudent and warranted. Finally, if the surgeon is practicing in a clinical setting where extensive resources including ICU critical care medicine are unavailable, damage control surgery (e.g., rapid identification and temporization of bleeding, abdominal packing, and temporary abdominal closure) and emergent transfer to a tertiary care referral center may be warranted.

Instruments for Dissection

Dissection, particularly when conducted in close proximity to major vessels, is conducted bluntly using right angle clamps and/or sharply using vascular forceps with Metzenbaum or Church scissors. Vascular forceps are critical for active manipulation of vessels and surrounding tissue. These typically have small rows of interlocking serrations capable of atraumatically grasping even thin-walled veins if used appropriately. Right angle forceps provide a useful tool to encircle vessels and dissect a window for vessel loop or vascular clamp placement. Initial superficial dissection and/or rapid dissection away from critical structures can often be conducted using electrosurgical instruments. While traditional hemostatic surgical instruments such as electrocautery are still indispensable, newer devices that apply bipolar current (Ligasure, Covidien, Dublin, Ireland) or ultrasonic energy (Harmonic scalpel, Ethicon, Somerville, NJ) can also be used to rapidly dissect with good hemostasis. Caution must be used, however, as these devices are capable of significant vascular injury if used carelessly or inappropriately. Finally, next-generation devices that use radiofrequency (Aquamantys, Medtronic, Dublin, Ireland) or argon gas (ABC system, Conmed, Utica, NY) show promise in providing superficial hemostasis. It must be noted, however, that none of these devices are capable of controlling hemorrhage from a major blood vessel, and use of these devices in the setting of uncontrolled hemorrhage, while tempting, will likely worsen the injury and exacerbate the problem.

Instruments for Vascular Control and Repair

Vessel loops are brightly colored Silastic loops that can be placed proximally and distally and assist in rapid identification and, if necessary, atraumatic temporary occlusion of the vascular structure of interest until an appropriate vascular clamp can be applied. Vascular clamps are available in a wide variety of shapes and sizes for various applications and are designed to occlude vessel flow without traumatizing the vessel walls. These clamps can be categorized by their intended functionality; fully occlusive transverse clamps (Fogarty, Debakey, Wylie, Henly, etc.) are intended to occlude the entire vessel lumen, whereas partially occlusive side-biting clamps (Satinsky, Cooley, Lemole-Strong, etc.) are used to preserve partial flow while excluding a region of damage for repair. Bulldog clamps can also be useful in some settings, particularly where small vessels are involved and must be temporarily occluded. Potts scissors and aortic punches can then be used to create, modify, and/or prepare an arteriotomy or venotomy for subsequent repair. Needle holders are then used to grasp the appropriate suture/needle and conduct the repair. While the specific needle drivers used (Castroviejo, Jacobson, Cohan, etc.) vary widely according to surgeon preference, at a minimum they must be able to accurately control small-caliber sutures and place the needle accurately in the intended tissue.

The suture used for vascular repairs is typically nonresorbable to provide adequate tensile strength until the vessel heals. One exception to this rule is in pediatric applications, where a slowly absorbable suture such as PDS (polydiox­anone) can be used to facilitate future growth at the anastomotic site. Most commonly, these sutures are monofilament and composed of polypropylene (Prolene, Ethicon Inc, Somerville, NJ; Surgipro, Covidien Inc, Dublin, Ireland) or polytetrafluoroethylene (GORE-TEX, Newark, DE). Suture size varies with the specific application, but typically 2-0 to 3-0 suture is chosen for aortic reconstructions, 5-0 is used for renal and iliac repair, and 7-0 is appropriate for small vessel work. Sutures are usually double-armed with a tapered needle swaged at both ends of a continuous suture to allow for continuous suturing bidirectionally from the apex of the defect toward the opposite apex, where they can be tied to each other.

Endovascular Instruments

The Fogarty thromboembolectomy catheter is a key device with several useful features and applications in vascular surgery. Briefly, these catheters consist of a long catheter with a distal balloon that can be inflated and deflated manually to the proper diameter corresponding to the vessel of interest. In the setting of uncontrolled bleeding, these catheters can be placed directly into a bleeding vessel and inflated to the proper size to occlude the vessel until a more permanent solution can be employed. Standard Fogarty catheters range in size from 2F to 10F; for example, a 5F balloon is appropriate for iliac vessels. Following anastomosis, these catheters can also be used to remove any distal thrombus or emboli that may be present. To accomplish this, the catheter is inserted to a point far proximal or distal to possible thrombus, inflated with saline (or air for 2F balloons), and slowly withdrawn to expel the vessel contents into the operative field. Care must be taken to avoid over-pressurizing the balloon, however, and causing endothelial damage and further thrombosis.

It is also worth mentioning that Fogarty occlusion catheters are also available for situations where endovascular occlusion is necessary. These catheters are available in balloon diameters ranging from 5 mm to 45 mm. If used properly, these catheters are capable of temporarily occluding nearly any vessel (including the abdominal aorta) to facilitate diminished blood loss and subsequent vascular repair in a bloodless field.

Hemostatic Agents

A number of hemostatic agents are now available for rapid hemostasis in the setting of diffuse and/or uncontrolled bleeding ( Table 10.1 ). Gelatin-based (Gelfoam, Pfizer, New York, NY), oxidized cellulose-based products (Surgicel, Ethicon, Somerville, NJ), and polysaccharide spheres (Arista, Bard Davol, Warwick, RI) all provide a physical matrix for clot formation to occur, but each has potential drawbacks (e.g. gelatin can swell and cause tissue compression, polysaccharide spheres also swell and are relatively contraindicated in diabetics, and cellulose can cause localized tissue acidosis). Other agents such as thrombin (Evithrom, Ethicon) and fibrin (Tisseel, Baxter, Deerfield, IL; Evicel, Ethicon) achieve hemostasis via active participation in coagulation and may be useful in controlling venous or even small arterial bleeding vessels or in damage control settings. Newer products derived from chitin and chitosan (HemCon Patch, HemCon, Portland, OR) have now recently become available, though data on effectiveness remain limited. Unfortunately, none of these products are able to stem blood loss from a significant defect in a major artery. If more extensive bleeding is present, surgical clips, including titanium clips and/or Weck polymer clips (Teleflex, Limerick, PA), are often used to control small- to medium-sized vessels rapidly if the vessel can be visualized and accessed. These clips can subsequently be removed if necessary to allow for a more definitive repair. Studies have shown that both of these solutions offer satisfactory hemostasis, even on larger vessels such as the renal artery. It should be noted, however, that the use of Weck or Hem-o-lok clips is contraindicated in living donor nephrectomy because three deaths occurred from clip displacement and hemorrhage.

Causes of Vascular Complications

Surgical errors can occur preoperatively, intraoperatively, and postoperatively and can have devastating consequences on patient morbidity and/or mortality. While previous studies have invoked numerous specific causes for surgical errors including excessive workload, sleep deprivation, and poor communication, most intraoperative vascular complications can be fundamentally categorized within three domains ( Fig. 10.1 ): (1) technical errors, (2) cognitive factors, and (3) biologic characteristics. Within this framework, technical errors are most common and encompass incidents such as inadequate tissue dissection and exposure leading to inadvertent vessel damage, instrument failure causing hemorrhage (e.g., endovascular stapler malfunction ), or careless/aggressive dissection causing traumatic injuries to fragile structures. Isolated biologic factors including aberrant anatomy and/or advanced disease processes can also deceive even the most cautious and experienced surgeons. For example, a recent case report described the development of significant scrotal edema following left living donor nephrectomy and large gonadal vein ligation in a patient with a known duplicated infrarenal inferior vena cava. Bridging the domains of biologic and technical causes, patient characteristics such as morbid obesity or prior abdominal surgeries can make an otherwise straightforward case far more complicated. Gabr et al. showed that morbid obesity was associated with a 21-fold greater likelihood of conversion from laparoscopic to open radical nephrectomy, and a recent study by Seifman and colleagues demonstrated that abdominal operations in patients with a prior abdominal surgical history were associated with longer mean hospital stay and higher rate of complications but surprisingly no difference in mean operative time.

Domains of surgical error causes with examples listed within each category.

Perhaps the most insidious of these potential sources of complications is the cognitive domain and what can be best described as lapses in clinical judgment. These are likely the most difficult to accurately identify and minimize because of human nature and the difficulty in introspectively identifying and acknowledging these as a surgeon. Data from malpractice claims for surgical errors in Belgium showed that 57% of lawsuits with medical mistakes were directly attributable to errors in judgment. These errors can be clustered as oversights in situational awareness and/or poor decision making.

Central to all three of these domains, however, is surgeon experience. A recent case series of robotic-assisted radical cystectomies with intracorporeal neobladder highlighted the importance of experience in minimizing operative time and complication rate. The study showed that as the surgeons became more familiar with the operation over their first 67 cases, operative time dropped by nearly 40%, conversion to open surgery dropped by 30%, and complications fell by 40%. These data underscore the ability of experience to potentially mitigate some of the risk associated with aberrant biology and/or difficult judgment calls based upon limited information.

Anticoagulation

Following initial control of bleeding, definitive management of the injured vessel is critical to ensure re-bleeding does not occur. Prior to performing the vascular repair, the surgeon should confirm that adequate tissue dissection and mobilization has been completed. The surgeon should then determine the need for systemic anticoagulation and/or proximal and distal embolectomy. If efforts to restore flow will require greater than ~30 minutes, then the risk of thrombus formation increases and further efforts must be undertaken to prevent thrombosis and/or embolization. Unless contraindicated (e.g., prior episode of heparin-induced thrombocytopenia), heparin is the agent of choice for systemic anticoagulation. Heparin is a naturally occurring glycosaminoglycan that binds to and activates antithrombin III, which subsequently inactivates thrombin and factor Xa and prevents clot propagation. Heparin activity onset occurs within 1 minute of administration, and heparin clearance occurs through both rapid saturatable mechanisms (e.g., depolymerization) and slower first-order mechanisms (e.g., renal clearance); practically, this means that the half-life varies from 30 minutes for small IV boluses (25 U/kg) to 150 minutes for larger doses (400 U/kg). Heparin dosing can be titrated intraoperatively by frequent measurements of the activated clotting time (ACT) via point-of-care testing. Once the repair is completed, heparin can be rapidly reversed by administration of protamine sulfate, a cation that directly binds to and inactivates the anion heparin. Protamine should be administered at 1 milligram protamine to 100 IU heparin and should be given first as a test dose to assess for anaphylactoid reactions. Of note is that giving excessive protamine has been shown to paradoxically cause a hypocoagulable state.

Embolectomy

In addition to systemic anticoagulation, serious consideration should be given to arterial or venous embolectomy in situations where the definitive repair takes a significant amount of time (more than 30 minutes) and there is concern for thrombus formation. Failure to do so can result in flow impairment, clot propagation, and distal embolization causing ischemia. In order to perform proximal and distal embolectomy, a Fogarty catheter is inserted and advanced with the balloon deflated. The balloon is then inflated and the catheter withdrawn while using tactile feedback to maintain proper balloon tension on the vessel wall. The maneuver should be repeated until no further clot is obtained. Care must be taken not to denude the endothelium, which can exacerbate the situation and worsen the thrombosis.

General Principles of Vascular Repair

In general, vascular repair is considered one of the most technically challenging aspects of any surgery. The construction of a watertight tension-free anastomosis without luminal narrowing requires both knowledge and proper technique to perform correctly. When suturing vessels, the needle should be placed directly perpendicular to the vessel wall and across all layers of the vessel to minimize risk of pseudoaneurysm formation. This is particularly important in the setting of a possible intimal flap, which if left uncontrolled can result in occlusion and thrombosis of the vessel. Sutures should typically be placed at 1-mm intervals and with 1 mm of tissue purchase. If the vessel is atherosclerotic, the placement of these sutures can be challenging and will ultimately be dictated by the location that most easily allows the needle to pass. If the vessel is small in diameter (<4 mm), then the vessel ends should be spatulated on opposite sides and anastomosed to prevent anastomotic narrowing.

Approaches to Definitive Repair

Numerous repair or ligation techniques are available to surgeons depending on the nature and location of the injury. In most cases of venous injury, the vessel can simply be ligated and the venous drainage allowed to collateralize as needed. If, however, the injury is arterial in nature, then the surgeon must assess whether permanent ligation will result in ischemia of any critical tissues being perfused by the artery. If adequate collateral flow is present (e.g., in the pelvis) or the artery is small (<2 mm), then vessel ligation is the quickest and simplest approach. This can be accomplished using surgical clips, Hem-o-lok clips, a vascular stapler, or silk ligatures (2-0 or 3-0). The area can then be inspected for hemostasis and the operation continued. If the vessel is critical to end-tissue perfusion and the vessel is larger (>2 mm), then the defect should be repaired and blood flow restored.

Primary repair is often the most straightforward approach if the defect is small and the surrounding vessel wall tissue remains uncompromised. These repairs can be performed using running or interrupted suture of the appropriate size, and care must be taken not to narrow the lumen, which predisposes the vessel to further stenosis and thrombosis.

If primary repair is not feasible due to the size or complexity of the lesion, then onlay patch repair (patch angioplasty) is warranted. This technique is also indicated if primary closure of the defect would result in significant stenosis to the vessel. While data from iatrogenic injuries remain limited, a Cochrane review meta-analysis of data from the carotid endarterectomy literature suggests that, at least in the isolated setting of controlled arteriotomy, patch closure is far superior to primary closure with regard to stenosis rate, thrombosis, and stroke. The choice of patch material seems to be less critical than the decision itself to patch, and several options are routinely used.

Broadly speaking, these patch material choices can be categorized as biologic or synthetic. Biologic options include autologous vein, bovine pericardium, or parietal peritoneum, while synthetic alternatives include Dacron and Teflon grafts. Dacron is a polyester-based graft composed of polyethylene terephthalate. Modern grafts are either woven or knitted; woven grafts are stronger but less compliant, while knitted grafts are also widely used and often treated with collagen, gelatin, or albumin. Teflon or PTFE (polytetrafluoroethylene) grafts are also commonly used. There appears to be no strong data to support the use of autologous tissue (saphenous vein), synthetic (Dacron), cadaveric (bovine pericardium), or peritoneal peritoneum for vessel patches, and the decision seems entirely dependent on surgeon preference and access to these various options.

In some cases, the damage to the vessel is too severe or geometrically unsuitable for primary repair or patch repair; in these circumstances an excision and reanastomosis is often indicated. This approach, however, often requires further dissection either proximally or distally (or both) in order to mobilize adequate vessel length to ensure a tension-free anastomosis. If this approach appears to impart significant tension on the repair, then an interposition graft should be used. The material selection of this graft follows similar principles to patch repair as described above.

If open repair is not feasible or fails, then alternative approaches, including endovascular repair, should be considered. Two case reports from the literature describe patients with prior ureteroileal diversion complicated by strictures and treated with cutting balloon endoureterotomy complicated by common iliac artery damage and massive hemorrhage. Both cases were successfully treated with endovascular stent repair of the damage. Aortoureteric fistulas also appear to be amenable to endovascular management in select circumstances. A recent case series identified 20 ureteroarterial fistulas, 74% of which were associated with pelvic radiation and 84% of which occurred in the setting of chronic indwelling ureteral stents. While endovascular repair appeared to confer similar morbidity when compared to open surgical repair, the overall mortality still approached 50%. Further tempering enthusiasm for this approach is the concern for placement of a foreign body (e.g., covered stent) in a contaminated space in direct contact with urine. While the initial intervention may stem blood loss and temporarily alleviate concerns over exsanguination, there exists a long-term risk for graft infection and recurrent bacteremia/sepsis. In this setting, it may be prudent to consider acute endovascular stent placement followed by definitive open surgical management including stent graft removal at a later date when the patient is more stable.