Visceral and Renal Tissue Oxygenation During Supraceliac Aortic Crossclamping and Left Heart Bypass with Selective Organ Perfusion

Selective renal blood perfusion induces renal tubules injury in a porcine model

OBJECTIVE

Extracorporeal circulation is routinely used in thoracoabdominal aortic aneurysm repair to preserve blood perfusion. Despite this protective measure, acute and chronic kidney disorders can develop. Therefore, the aim of this study was to establish a new large-animal model to assess the efficacy of selective renal perfusion (SRP) with extracorporeal circulation in a setting of thoracoabdominal aortic aneurysm repair.

METHODS

Eighteen pigs underwent a thoracolaparotomy, during with the aorta and renal arteries were exposed. The animals were divided into three cohorts of six pigs each: cohort I--control; cohort II--thoracic aortic clamping with distal aortic perfusion (DAP) using a roller pump; and cohort III--thoracic aortic clamping with DAP plus SRP. Kidney metabolism, kidney injury, and red blood cell damage were measured by oxygen extraction ratio (O2ER), neutrophil gelatinase-associated lipocalin, a marker for acute kidney damage, and serum free hemoglobin.

RESULTS

With normal mean arterial blood pressures, flow rates in the renal arteries during perfusion decreased to 75% (group II) with DAP and to 50% (group III) with SRP compared with the control animals (group I; P = .0279 for I vs II; P = .0002 for I vs III). Microcirculation, measured by microspheres, did not differ significantly among the groups. In contrast, O2ER (P = .0021 for I vs III) and neutrophil gelatinase-associated lipocalin (P = .0083 for I vs III) levels were significantly increased in group III, whereas free hemoglobin was increased in groups II and III (P = .0406 for I vs II; P = .0018 for I vs III).

CONCLUSIONS

SRP with a roller pump induces kidney tubule injury. Thus, distal aortic and SRP in our model does not provide adequate kidney protection. Furthermore, the perfusion system provokes red blood cell damage with increased free hemoglobin. Hence, the SRP perfusion technique should be revised and tested.

Microcirculatory perfusion shift in the gut wall layers induced by extracorporeal circulation

OBJECTIVE

Extracorporeal circulation (ECC) is regularly applied to maintain organ perfusion during major aortic and cardiovascular surgery. During thoracoabdominal aortic repair, ECC-driven selective visceral arterial perfusion (SVP) results in changed microcirculatory perfusion (shift from the muscularis toward the mucosal small intestinal layer) in conjunction with macrohemodynamic hypoperfusion. The underlying mechanism, however, is unclear. Therefore, the aim of this study was to assess in a porcine model whether ECC itself or the hypoperfusion induced by SVP is responsible for the mucosal/muscular shift in the small intestinal wall.

METHODS

A thoracoabdominal aortic approach was performed in 15 healthy pigs divided equally into three groups: group I, control; group II, thoracic aortic cross-clamping with distal aortic perfusion; and group III, thoracic aortic cross-clamping with distal aortic perfusion and SVP. Macrocirculatory and microcirculatory blood flow was assessed by transit time ultrasound volume flow measurement and fluorescent microspheres. In addition, markers for metabolism and intestinal ischemia-reperfusion injury were determined.

RESULTS

ECC with a roller pump induced a significant switch from the muscularis and mucosal layer of the small intestine, even with adequate macrocirculation (mucosal/muscular perfusion ratio: group I vs II, P = .005; group I vs III, P = .0018). Furthermore, the oxygen extraction ratio increased significantly in groups II (>30%) and III (>40%) in the beginning of the ECC compared with the control (group I vs II, P = .0037; group I vs III, P = .0062). Lactate concentrations and pH values did not differ between groups I and II; but group III demonstrated a significant shifting toward a lactate-associated acidosis (lactate: group I vs III, P = .0031; pH: group I vs III, P = .0001).

CONCLUSIONS

We demonstrated a significant shifting between the small intestinal gut wall layers induced by roller pump-driven ECC. The shift occurs independently of macrohemodynamics, with a significant effect on aerobic metabolism in the gut wall. Consequently, an optimal intestinal perfusion cannot be guaranteed by a roller pump; therefore, perfusion techniques need to be optimized.

Circulating intestinal fatty acid-binding protein as an early marker of intestinal necrosis after aortic surgery: a prospective observational cohort study

OBJECTIVE

This study evaluated the usefulness of plasma intestinal fatty-acid binding protein (IFABP) levels in the early identification of intestinal necrosis (IN) in patients undergoing different types of aortic surgery.

BACKGROUND

Intestinal compromise greatly contributes to postoperative adverse outcome. IN is the most detrimental form of intestinal compromise and is notoriously difficult to diagnose. IFABP is a small protein exclusively expressed by mature enterocytes and a promising marker of intestinal damage.

METHODS

Plasma IFABP concentrations were measured in blood samples taken perioperatively from 55 patients undergoing open thoracic or thoracoabdominal aneurysm repair [OR-TAA(A)], 25 patients undergoing conventional open abdominal aneurysm repair (OR-abdominal aortic aneurysm [AAA]), and 16 patients undergoing endovascular aneurysm repair (EVAR). Data were compared with perioperative changes in arterial pH and serum lactate levels.

RESULTS

IFABP levels increased in all patients undergoing OR-TAA(A) and OR-AAA reaching peak levels shortly after surgery; 281 ± 33 to 2,298 ± 490 pg/mL (P < 0.001) and 187 ± 31 to 641 ± 176 pg/mL (P < 0.05) respectively. IFABP levels were significantly higher in patients undergoing OR-TAA(A) (P < 0.001). IFABP levels in EVAR patients remained at baseline concentrations throughout the study. Four patients [2 OR-AAA, 2 OR-TAA(A)] developed fatal postoperative intestinal ischemia on day 2 or 3. High levels of plasma IFABP at the end of surgery had 100% sensitivity and 98.1% specificity for the identification of patients developing IN. In OR-AAA patients, arterial pH and lactate levels were of additional discriminating value. Complete discrimination between patients with and without IN using plasma IFABP could be made on the first postoperative day.

CONCLUSIONS

Analysis of plasma IFABP levels is of additional value to other current plasma markers in the diagnosis of IN, and it enables early identification of patients with IN after aortic surgery days before clinical diagnosis.

PANCREATIC INJURY AFTER THORACOABDOMINAL AORTIC OCCLUSION IN A PORCINE MODEL

BACKGROUND

The aim of this study was to investigate pancreatic injury after 45 min of thoracoabdominal aortic occlusion in a porcine model.

METHODS

Twenty-four pigs were used. Six pigs underwent sham operation and 18 intravascular balloon thoracoabdominal aortic occlusions for 45 min. The animals were randomly killed at 12, 48 and 120 h after reperfusion. After killing, all pancreata were examined macroscopically for any signs of acute pancreatitis, whereas gland specimens were harvested for histological study to evaluate pancreatic injury (haematoxylin and eosin staining) and acinar cell apoptosis (Terminal deoxynucleotidyl transferase mediated dUTP Nick-End Labelling staining).

RESULTS

Pancreatic injury severity score was mildly increased in terms of oedematous features at 12 h after reperfusion, but normalized to sham levels by the second day and thereafter. Necrotic injury was not statistically significant at any time point. Acinar cell apoptotic index was mildly increased at 12 and 48 h, but showed a tendency to decrease towards sham levels by the fifth day. One animal developed acute pancreatitis.

CONCLUSION

Acute pancreatitis is unlikely to occur after 45 min of thoracoabdominal aortic occlusion. However, an early, mild oedematous and apoptotic injury that occurs subclinically seems to be a constant event. This injury might have clinical significance when combined with pre-existent pancreatic pathologies.

Optimal End-Organ Protection for Thoracic and Thoracoabdominal Aortic Aneurysm Repair Using Deep Hypothermic Circulatory Arrest

BACKGROUND

Despite the advent of numerous protective strategies, thoracic and thoracoabdominal aortic replacement remains a high risk. While mortality rates have improved over the last 15 years, the incidence of adverse outcomes (including stroke, renal failure, and paraplegia, as well as death) remains at 13% to 30% in all published series. The use of deep hypothermic cardiopulmonary bypass with circulatory arrest has been associated with high morbidity in the past; however, we report a single surgeon's experience of improved end-organ protection with low morbidity and mortality utilizing this technique.

METHODS

One hundred seventy-three consecutive patients with descending thoracic and thoracoabdominal aneurysms were operated on between April 1995 and March 2005. Hypothermic (15 degrees C) cardiopulmonary bypass with circulatory arrest and open proximal anastomosis were utilized in all subjects. Visceral arteries were uniformly reimplanted as an island while additional renal artery bypasses were performed as required. Lower intercostals and lumbar arteries were aggressively reimplanted or preserved at the aortic anastomosis. No other adjuncts for spinal cord protection were routinely employed.

RESULTS

Sixty-three patients with isolated descending thoracic aortic aneurysms and 27 patients with extent I, 49 with extent II, 20 with extent III, and 14 with extent IV thoracoabdominal aortic aneurysms underwent operative repair. Ninety percent of cases were elective while 10% were urgent or emergent. There were seven hospital deaths, and the hospital mortality was 4.0%. Operative complications included stroke in seven patients (4.1%), paraplegia in four (2.4%), including 0 of 62 ambulatory patients with isolated thoracic aneurysm repairs, and acute renal failure requiring dialysis in two of 168 operative survivors that were not dialysis-dependent before surgery.

CONCLUSIONS

Deep hypothermic circulatory arrest allows replacement of complex aortic pathology with low mortality. End-organ protection is excellent with lower incidences of dialysis-dependent renal failure and paraplegia than are reported with other currently used surgical techniques.

Preservation of Renal Function Utilizing Hypothermic Circulatory Arrest in the Treatment of Distal Thoracoabdominal Aneurysms (Types III and IV)

Although left heart bypass and hypothermia are often used in the performance of type I and type II thoracoabdominal aneurysms (TAAs), most of these more distal aneurysms are done utilizing the clamp and sew technique. Renal failure occurs between 8.6% to 39% in recent series of patients following surgery for type III and IV TAAs. The purpose of this study was to determine whether the use of hypothermic circulatory arrest in these cases would serve to protect renal function. All patients were operated on using hypothermic circulatory arrest. The kidneys were perfused with cold blood during the procedures, and renal artery bypasses were aggressively used (when stenoses greater than 50% were observed). The series describes 33 consecutive patients with type III and IV TAAs who were operated on utilizing hypothermic circulatory arrest with a core temperature of 15 degrees centigrade. All visceral and renal arteries were individually perfused; 20 patients had bypass grafts of their renal artery stenoses. Although six patients had renal failure preoperatively, only one developed postoperative renal failure. This was the patient who was operated on as an emergency for severe abdominal pain, back pain, and acidosis who was also the only hospital death. Of the remaining five patients with elevated creatinines preoperatively, four had postoperative decrease of the serum creatinine. One patient developed paraparesis and one developed a stroke. The median length of stay was 8 days. Consideration should be given to the use of hypothermic circulatory arrest in type III and IV TAAs for the preservation of renal function and improved overall results.