Objective: To investigate the utility of regional saturation oxygen (rSO₂) using near-infrared spectroscopy (NIRS) in the lower limbs and to estimate the safe occlusion duration in patients with abnormally adherent placentation who underwent intra-aortic balloon occlusion (IABO) during a cesarean hysterectomy by comparing them with infrarenal aortic clamping.

Methods: The researchers classified 15 lower limbs of patients with abnormally adherent placentation with IABO during a cesarean hysterectomy as the balloon group and 20 lower limbs of patients with cross-clamping on the infrarenal aorta during the aneurysmal repair as the clamping group. The rSO₂ measurement of the limbs was performed using a near-infrared spectrometer. In addition, the aortic occlusion duration, rSO₂ before and during occlusion, and after blood resumption were analyzed.

Results: Continuous rSO₂ measurement was possible in all patients. The median aortic occlusion durations in the balloon and clamping groups were 68 and 92.5 min, and the median minimum rSO₂ during occlusion was 60% and 17.5%, respectively. The clamping group was found to have stronger occlusion for a longer time than the balloon group. No complications associated with aortic occlusion were observed in both groups.

Conclusions: rSO₂ measurement using a near-infrared spectrometer effectively monitors lower-limb blood flow during IABO in patients with abnormally adherent placentation. An IABO duration of approximately 90 min was believed to be relatively acceptable in a cesarean hysterectomy under heparin administration.

Abnormally adherent placentation; Aortic occlusion duration; Intra-aortic balloon occlusion; Lower-limb regional saturation oxygen; Near-infrared spectroscopy

For a patient with abnormally adherent placentation, particularly placenta increta and percreta, a cesarean hysterectomy is commonly performed to prevent intrapartum and postpartum hemorrhagic complications. However, the risk of massive bleeding remains high in this surgery, requiring an elective adjuvant hemostatic procedure. Internal iliac artery balloon occlusion is a widely used method in cesarean hysterectomy of abnormally adherent placentation; however, this procedure does not decrease intraoperative hemorrhage [1]. Recently, IABO has been reported as an effective hemostatic procedure [2]. Previous studies revealed that the hemostatic effect of IABO is superior to that of balloon occlusion of the internal or common iliac artery [3]. Ischemia due to aortic balloon occlusion increases the risk of rare but serious complications, such as thrombosis, hyperkalemia, and acute kidney injury associated with ischemic reperfusion injury [4,5]. Although the risk of these complications is thought to increase with longer occlusion duration, safe occlusion duration for IABO remains unknown. NIRS is a simple, painless, and complication-free technique to evaluate tissue oxygenation. Unlike the arterial oxygen saturation (SPO₂) measurement using a pulse oximeter, rSO₂ measurement using NIRS helps determine the oxygen saturation of arterioles, venules, and capillaries and is a more useful tissue oxygenation index of decreased blood flow. The researchers examined the utility of rSO₂ measurement using NIRS for lower-limb blood flow monitoring and estimated the safe occlusion duration in patients with abnormally adherent placentation who underwent IABO during a cesarean hysterectomy by comparing the results to those with aortic cross-clamping during the surgical repair of aortic aneurysms.

Patients

The balloon group comprised nine patients, with a total of 15 lower limbs measured, of abnormally adherent placentation and placenta previa who underwent IABO during a cesarean hysterectomy between May 2007 and November 2019. The clamping group consisted of 11 patients, with a total of 20 lower limbs measured, who underwent cross-clamping with forceps on the infrarenal aorta and both common iliac arteries during the surgical repair of the abdominal aortic aneurysm during the same period. Informed consent was obtained from all study participants in this study.

rSO₂ measurement

rSO₂ in the lower limbs was percutaneously measured using a continuous dual-infrared spectrometer, INVOS 5100C (Somanetics, Troy, MI, USA).

NIRS probes were positioned on either the bilateral or unilateral anterior tibial muscle.

Data analysis

The researchers retrospectively examined the operative time, volume of intraoperative bleeding, occlusion duration in IABO/cross-clamping of the aorta, lower-limb rSO₂ before and during occlusion, rSO₂ after blood flow resumption, serum creatinine, serum potassium (K), serum lactate levels, and surgical complications from medical records. Thereafter, changes in lower limb rSO₂ before occlusion, during occlusion, and after blood flow resumption were assessed in each group, and the occlusion duration and occurrence of complications were compared between the two groups.

IABO

To initiate IABO, the right femoral artery was punctured using the Seldinger technique by placing a guide catheter sheath. Then, the occlusion balloon catheter was inserted and placed just above the abdominal aortic bifurcation. An 8-Fr. sheath introducer (Terumo, Tokyo, Japan) and a 7-Fr. Shaft HYM balloon catheter® (30 mm balloon; FORTE GROW MEDICAL Co. Ltd., Tokyo, Japan) were used. The aortic balloon catheter was inflated when the operator suspected increased bleeding. Heparin (5,000 U) was intravenously administered before the inflation and supplemented to maintain a 200-s activated clotting time (ACT). Protamine sulfate was injected after balloon deflation to neutralize heparin [6].

Aortic cross-clamping

Aortic clamping was performed at the proximal and distal sites of the aneurysm during a surgical repair of infrarenal abdominal aortic aneurysms. Bilateral common iliac arteries were selected for the distal clamping portion. The aortic aneurysm was resected, and a Y-shaped prosthetic graft replacement was performed. Heparin was administered at 100 U/kg before the aortic clamping and supplemented to maintain an ACT of ≥ 200 s. The postoperative diagnosis of abnormally adherent placentation severity (accreta, increta, or percreta) was made based on the histologic findings of the specimens. Wilcoxon signed-rank test was used to determine the rSO₂ differences of the lower limbs before occlusion, during occlusion, and after blood flow resumption. The Mann-Whitney test was used to compare the occlusion duration and rSO₂ between the two groups. This retrospective study was approved by the Institutional Review Board of the University in March 2021 (#1765).

In the IABO group, the rSO₂ of 15 lower limbs among nine patients was measured: both lower limbs in six and only the left leg in three patients as these patients occurred early in the study period. In the clamping group, the rSO₂ of 20 lower limbs of 11 patients was measured: both lower limbs in nine, only the left leg in one, and only the right leg in one.

Patient backgrounds

Patient backgrounds in the balloon group are shown in Table 1.

Table 1: Patient backgrounds in the balloon group.

All patients had a history of previous cesarean sections. Operative times ranged from 165 to 320 min, and the volume of intraoperative bleeding ranged from 2,955 to 11,800 mL. Postoperative diagnosis showed that the majority of patients had serious adherent placentation, and eight of nine patients were increta or percreta. Patient backgrounds in

the clamping group are shown in Table 2. All patients had infrarenal abdominal aortic aneurysms and underwent Y-graft replacement. The number of elderly patients in the clamping group was higher than that in the balloon group. Operative times ranged from 213 to 518 min, and the volume of intraoperative bleeding ranged from 215 to 3,475 mL.

Table 2: Patient backgrounds in the clamping group.

Aortic occlusion duration

The aortic occlusion duration of both groups is shown in Figure 1. The median occlusion duration of the balloon and clamping group was 68.0 (range 24-90) min and 92.5 (range 50-190) min, respectively, with the latter being significantly long (p=0.0028).

Figure 1: Aortic occlusion duration in both groups.

rSO2 in the lower limbs

Figure 2 shows the rSO₂ in the lower limbs in both groups. During occlusion, the rSO₂ was lower than during other phases. In the balloon group, the median rSO_2, i.e., 73% before occlusion, showed a significant decrease to 60% during occlusion (p<0.0001), but immediately recovered to the pre-occlusion level after the blood flow resumption. In the clamping group, the rSO₂ median considerably decreased from 71% before occlusion to 17.5% during occlusion (p<0.0001), whereas after the resumption, most limbs immediately showed recovery to the pre-occlusion values. Only two limbs showed rSO₂ of 16% immediately after the resumption but recovered to 65% and 66%, respectively, before the end of the surgery.

Figure 2: Lower limb regional saturation oxygen (rSO₂) before occlusion, during occlusion, and after blood flow resumption.

Pre- and postoperative serum creatinine, K, and lactate levels

Figure 3 shows the changes in serum creatinine, K and lactate levels of the balloon group. Only one patient showed an abnormally high serum creatinine level (0.98 mg/dL) immediately after the surgery but returned to normal (0.53 mg/dL) at discharge without treatment. No patient showed an abnormal increase in the serum K level. The serum lactate level showed a slight increase after the surgery, but no patient needed specific treatment for it. Changes in the serum creatinine, K, and lactate levels in the clamping group are shown in Figure 4. Ten of 11 patients showed an increase in serum creatinine level immediately after the surgery, as compared to preoperative values; however, all patients recovered nearly to preoperative values at discharge without treatment. No patients showed an abnormal increase in the serum K level. The serum lactate level showed a slightly increased after the surgery. Only one patient had a pathologic increase from a preoperative level of 0.5 mmol/L to 3.4 mmol/L; however, there was no evidence of muscle crush syndrome or other complications, and it did not require specific treatment.

Figure 3: Changes of preoperative and postoperative serum creatinine, K, and lactate in the balloon group.

Figure 4: Changes of preoperative and postoperative serum creatinine, K, and lactate in the clamping group.

Comparison between the balloon and clamping groups

Table 3 shows the comparison between the two groups in occlusion duration and lower limb rSO₂. The median occlusion duration in the balloon and clamping groups was 68 and 92.5 min, respectively, with the latter group being significantly longer than the former (p=0.0028). There was no significant difference in the median rSO₂ between the two groups before occlusion, but the clamping group had considerably lower median rSO₂ during occlusion than the balloon group (17.5% vs. 60%; p<0.0001). No patient showed a decreased rSO₂ that persisted postoperatively. Regarding surgical complications, one patient had a bladder injury in the balloon group but was repaired intraoperatively. No patient developed thromboembolism or other operative complications associated with aortic occlusion in both groups.

Table 3: Comparison of the occlusion duration and lower limb regional saturation oxygen (rSO₂) values between the balloon and clamping groups.

NIRS is a tool used to diagnose and evaluate the blood flow in the brain, liver, lungs, and other organs [7]. Some reports used NIRS to assess lower-limb rSO₂ while monitoring perioperative blood flow in the heart, arteriopathy, and intrapelvic diseases [8-10]. A case series report demonstrated that 67%, 32%, and 74% of 10 patients underwent abdominal aortic aneurysm resection with aortic clamping, lower limb rSO₂ preoperatively, during clamping, and after blood resumption, respectively [11]. However, no reports examined lower limb rSO₂ using NIRS in a large number of patients with abnormally adherent placentation who underwent IABO. The researchers measured the lower limb rSO₂ using NIRS for a total of 15 lower limbs in patients who underwent IABO during a cesarean hysterectomy. Continuous perioperative measurement was possible in all patients without difficulty.

Only a few studies reported the appropriate perioperative aortic occlusion duration. In cross clamping the supra-renal aorta, appropriate occlusion duration was reported to be within 50-90 min [12,13]. In infrarenal aortic occlusion, many collateral pathways exist; thus, even occlusion over a longer period is unlikely to cause ischemia of the organs or lower limbs. A report indicated that all nine patients who underwent abdominal aortic aneurysm resection with infrarenal aorta clamping returned to their pre-occlusion levels of lower limb rSO₂ after occlusion at an average of 66.7 min [14]. Others reported that all five patients who underwent occlusion for 40-65 min using the infrarenal aortic balloon during sacral tumor resection were discharged without sequelae [15]. However, for IABO in abnormally adherent placentation, the safe occlusion duration remains unknown as no study has been conducted with a large number of participants.

In the study, the results of the comparison between the two groups were as follows: 1) occlusion duration in the clamping group was significantly longer than in the balloon group, 2) rSO₂ during occlusion was considerably lower in the clamping group, and 3) no complications caused by aortic occlusion occurred in both groups. Although the clamping group underwent stronger occlusion, as evidenced by a significantly lower rSO2, for a longer time than the balloon group (median rSO₂ during occlusion was 17.5 vs. 60%, and median occlusion duration was 92.5 vs. 68 min), no complications associated with occlusion occurred in the clamping group. Based on these results, aortic balloon occlusion of approximately 90 min long was thought to be a relatively acceptable hemostatic procedure.

Aortic balloon occlusion during cesarean hysterectomy entails a risk of thrombosis, with an incidence of approximately 0.9%-10% [16-19]. A heparin dosage was administered to prevent thrombosis, and some reports demonstrated that heparin injection through an arterial sheath was effective for thromboprophylaxis in IABO [15,20]. However, no thorough examination of anticoagulant therapy in IABO including a large number of patients has been performed, and no formal recommendation for heparin administration has been established. Future studies on this issue will be necessary.

The study had several limitations. First, this was a single-center retrospective study with a small sample size. Second, rSO₂ measurement using NIRS can be influenced by some conditions and agents, such as anemia, regional blood flow, and vasoconstriction [21]. Third, researchers compared patients with different surgical procedures. To determine an acceptable occlusion duration in IABO, ideally, only those who underwent this procedure should have been evaluated; however, it would have been difficult to examine appropriate aortic occlusion duration in patients with abnormally adherent placentation alone. Therefore, occlusion duration and complications in an aortic aneurysm operation were investigated, as several patients underwent aortic occlusion.

An attempt was made to extrapolate an acceptable occlusion duration in patients who underwent IABO using these results. Therefore, although the clamping group underwent stronger and longer occlusion (median of 92.5 min) than the balloon group, complications associated with occlusion were not detected in either group. This led to the conclusion that aortic occlusion for approximately 90 minutes was likely to be relatively safe. For IABO in abnormally adherent placentation, the safe occlusion duration is still unknown. Further clinical studies involving more participants are necessary.

In conclusion, rSO₂ measurement using INVOS 5100C seemed to be useful as an evaluation method for lower limb blood flow during IABO in abnormally adherent placentation. With heparin administration, aortic balloon occlusion for approximately 90 min seemed to be acceptable in a cesarean hysterectomy.

The authors would like to thank Enago (www.enago.jp) for the English language review.

No funding was received for conducting this study.

Ethical approval

This retrospective study was planned in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of the university in March 2021 (#1765).

Consent to participate

Informed consent was obtained from all study participants.

Consent for publication

All authors have given their consent for publication.

Conflict of interest

All authors declare no conflicts of interest.

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