How Do We Evaluate Pelvic Circulation and Predict Buttock Claudication?
Article ID: CJ-21-0067
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Article ID: CJ-21-0067
In Europe and the United States, the prevalence of iliac artery aneurysm complication among patients with abdominal aortic aneurysm (AAA) is 20%,1 and straight grafts are used in 30–66% of AAAs that are surgically treated.2,3 In contrast, in consecutive 143 cases with AAA treated at our department, 68 cases (48%) were complicated with iliac artery aneurysm,4 and this high frequency is a cause for concern in Japan. This complication results in a need to ligate or embolize the hypogastric artery (HGA) during aneurysm repair with consequent dynamic changes in the pelvic circulation.
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After surgery, some patients with AAA complain of pain in the buttocks during walking. This is regarded as a claudication symptom attributable to gluteal muscle ischemia due to reduced blood flow. The incidence of buttock claudication after ligation or coil embolization of HGA has been reported to be approximatley 11–50% of patients.5,6
To avoid such complications, the preservation or reconstruction of HGA blood flow may be the most reliable approach. However, no intraoperative monitoring method has been established to assess pelvic circulation objectively, and there is no indication criteria for HGA reconstruction. In this issue of the Journal, Fujioka et al7 report that regional oxygen saturation (rSO2) measurement by near-infrared spectroscopy (NIRS) is useful for monitoring blood flow in the HGA area.
Intrapelvic blood flow can be evaluated by the penile brachial index (PBI), calculated by dividing the systolic blood pressure of the dorsal artery of the penile artery by the systolic blood pressure of the brachial artery. A PBI of ≤0.6 suggests a possible blood circulation disorder.8 Although it is possible to predict vasculogenic male sexual dysfunction with PBI, it is difficult to evaluate gluteal muscle ischemia. And although PBI measurement is an easy approach, there are limitations to this technique including first, its unavailability in female patients; second, its inability to diagnose which side is potentially affected; and third, its inability to predict the consequence of HGA area circulation caused by collateral vessel (Figure) compensation for arterial trunk occlusion because it does not evaluate ischemia in the HGA area directly.
Five possible options for collateral circulation to the HGA: ① Mesenteric route: IMA–superior rectal artery–intracolonic vessels–middle rectal artery–HGA; ② Lumbar artery route: lumbar artery–iliolumbar artery–HGA; ③ HGA route: contralateral HGA–lateral sacral artery–ipsilateral HGA; ④ EIA route: EIA–deep circumflex iliac artery–inferior gluteal artery–HGA; and ⑤ Deep femoral artery route: deep femoral artery–medial circumflex femoral artery–obturator artery–inferior gluteal artery–HGA. The HGA route, EIA route, and deep femoral artery route are important as possible collateral routes to HGA after endovascular aneurysm repair. EIA, external iliac artery; HGA, hypogastric artery; IMA, inferior mesenteric artery. A, Lumbar arteries; B, Superior gluteal artery; C, Iliolumbar artery; D, Deep iliac circumflex artery; E, External iliac artery; F, Common femoral artery; G, Medial femoral circumflex artery; H, Inferior mesenteric artery; I, Superior rectal artery; J, Hypogastric artery; K, Inferior gluteal artery; L, Lateral sacral artery; M, Middle and inferior rectal artery; N, Obturator artery.
Sugano et al5 assessed the usefulness of intraoperative HGA stump pressure measurement in predicting postoperative buttock claudication in patients with AAA. They found that the HGA–brachial pressure ratio, which is calculated as HGA stump pressure/brachial artery pressure, was 0.62 in cases wherein postoperative buttock claudication occurred. This was significantly lower than the ratio of 0.76 observed in cases without postoperative buttock claudication. Furthermore, the ratio did not exceed 0.65 in the cases with postoperative buttock claudication. These data suggest that the HGA stump pressure values measured intraoperatively could serve as a predictor for postoperative buttock claudication. However, this technique is applicable during open AAA surgery, but not easily applied during endovascular aneurysm repair (EVAR).
NIRS is a technique that uses near-infrared light to non-invasively monitor oxygen saturation of muscle tissues. NIRS is based on the following: (1) specific wavelengths of red and near-infrared light have the ability to penetrate through biological tissue; (2) absorption of these specific red and near-infrared wavelengths are dominated by hemoglobin; and (3) absorption varies between oxygenated and deoxygenated hemoglobin.9
Most commercially available NIRS optrodes consist of a light source and 2 receiving photodetectors. The light source emits red light and near-infrared light that passes through sampled tissue to its photodetectors. From the amount of light that is detected at the photodetectors, NIRS calculates the absorption of red and near-infrared light by oxy- and deoxyhemoglobin. Therefore, the proportion of oxyhemoglobin can be determined. The penetration depth is approximately equal to half the distance between the light source and the detectors, resulting in a maximum penetration depth of approximately 2 cm from the skin surface.9
Although NIRS is not adopted in daily vascular practice yet, it has recently been used to evaluate muscle deoxygenation in patients with various vascular diseases, including intermittent claudication accompanying arteriosclerosis obliterans.10 NIRS is able to provide real-time and continuous information regarding hemodynamic changes, and to distinguish between patients with normal and impaired vascularization.
One study described the ability of NIRS to identify buttock ischemia during AAA repair, and found that NIRS curves as gluteal muscles responded sensitively to aortic cross-clamping.11 Two other studies described the ability of NIRS to identify buttock ischemia after AAA repair.5,12 Fujioka et al7 applied NIRS to intraoperative monitoring of blood flow in the HGA area in patients with EVAR and HGA embolization. Their critical findings suggest that intraoperative reduction of rSO2 may be a predictor of buttock claudication after EVAR with HGA embolization.
One limitation of NIRS is that subcutaneous fat at the buttocks may be important in obese patients and whether the saturation measured is from fat or from muscles tissues must be considered. Furthermore, absolute values provided by the device seem relatively unreliable, and a rSO2 decrease seems to better distinguish between normal and abnormal results compared with absolute values.
Based on the data reported by Fujioka et al,7 NIRS is expected to contribute to the prediction of postoperative gluteal muscle claudication and provide additional information for indication of HGA reconstruction during AAA surgery in daily vascular practice.
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