Background 

Surgical wound-healing complications after tumor resections in tissue that has been preoperatively radiated are a major clinical problem. Most studies have reported that complications occur in more than 30% of patients undergoing such resections in the lower extremity. There is currently no available method to predict which patients are likely to have a complication. Transcutaneous oximetry has been identified in preliminary studies as potentially useful, but the available evidence on its efficacy for this application thus far is inconclusive.

Questions/purposes 

(1) Does transcutaneous oximetry measurement below 25 mmHg at any location in the surgical wound bed predict a wound-healing complication? (2) Does recovery (increase) in transcutaneous oxygen measurement during the rest period between the end of radiation and the time of surgery protect against wound-healing complications?

Methods 

A prospective, multi-institution study was coordinated to measure skin oxygenation at three timepoints in patients undergoing surgery for a lower extremity soft tissue sarcoma after preoperative radiation. Between 2016 and 2020, the five participating centers treated 476 patients for lower extremity soft tissue sarcoma. Of those, we considered those with a first-time sarcoma treated with radiation before limb salvage surgery as potentially eligible. Based on that, 21% (98 of 476) were eligible; a further 12% (56 of 476) were excluded because they refused to participate or ultimately, they were treated with a flap, amputation, or skin graft. Another 1% (3 of 476) of patients were lost because of incomplete datasets or follow-up less than 6 months, leaving 8% (39 of 476) for analysis here. The mean patient age was 62 ± 14 years, 62% (24 of 39) of the group were men, and 18% (7 of 39) of patients smoked cigarettes; 87% (34 of 39) of tumors were intermediate/high grade, and the most common histologic subtype was undifferentiated pleomorphic sarcoma. In investigating complications, a cutoff of 25 mmHg was chosen based on a pilot investigation that identified this value. All patients were assessed for surgical wound-healing complications, which were defined as: those resulting in a return to the operating room, initiation of oral or IV antibiotics, intervention for seroma, or prolonged wound packing or dressing changes. To answer the first research question, we compared the proportion of patients who developed a wound-healing complication between those patients who had any reading below 25 mmHg (7 of 39) and those who did not (32 of 39). To answer the second question, we compared the group with stable or decreased skin oxygenation (22 of 37 patient measurements [two patients missed the immediate postoperative measurement]) to the group that had increased skin oxygen measurement (15 of 37 measurements) during the period between the end of radiation and the surgical procedure; again, the endpoint was the development of a wound-healing complication. This study was powered a priori to detect an unadjusted odds ratio for wound-healing complications as small as 0.71 for a five-unit (5 mmHg) increase in TcO₂ between the groups, with α set to 0.05, β set to 0.2, and a sample size of 40 patients.

Results 

We found no difference in the odds of a wound-healing complication between patients whose transcutaneous oxygen measurements were greater than or equal to 25 mmHg at all timepoints compared with those who had one or more readings below that threshold (odds ratio 0.27 [95% confidence interval (CI) 0.05 to 1.63]; p = 0.15). There was no difference in the odds of a wound-healing complication between patients who had recovery of skin oxygenation between radiation and surgery and those who did not (OR 0.63 [95% CI 0.37 to 5.12]; p = 0.64).

Conclusion 

Transcutaneous oximetry cannot be considered a reliable test in isolation to predict wound-healing complications. This may be a function of the fact that transcutaneous oximetry samples a relatively small portion of the landscape in which a wound-healing complication could potentially arise. In the absence of a reliable diagnostic test, clinicians must still use their best judgment regarding surgical timing and work to address modifiable risk factors to avoid complications. The unanswered question that remains is whether there is a skin perfusion or oxygenation issue at the root of these complications, which seems likely. Alternative approaches that can assess the wound more broadly and in real time, such as fluorescent probes, may be deserving of further investigation.

Level of Evidence 

Level II, diagnostic study.

中文翻译：

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经皮血氧仪不能可靠地预测术前放射软组织肉瘤的伤口愈合并发症

背景 

在术前放射过的组织中切除肿瘤后的手术伤口愈合并发症是一个主要的临床问题。大多数研究报告说，超过 30% 的下肢接受此类切除术的患者会出现并发症。目前没有可用的方法来预测哪些患者可能有并发症。经皮血氧饱和度测定法已在初步研究中被确定为可能有用，但迄今为止关于其在该应用中有效性的可用证据尚无定论。

问题/目的 

(1) 经皮血氧饱和度测量在手术伤口床的任何位置低于 25 mmHg 是否预测伤口愈合并发症？(2) 在放疗结束和手术之间的休息期间，经皮氧测量值的恢复（增加）是否可以防止伤口愈合并发症？

方法 

协调一项前瞻性、多机构研究，以测量术前放疗后接受下肢软组织肉瘤手术的患者在三个时间点的皮肤氧合情况。2016 年至 2020 年间，五个参与中心共治疗了 476 名下肢软组织肉瘤患者。其中，我们认为那些在保肢手术前首次接受放射治疗的肉瘤患者可能符合条件。基于此，21%（476 人中的 98 人）符合条件；另有 12%（476 人中的 56 人）被排除在外，因为他们拒绝参与或最终接受了皮瓣、截肢或植皮治疗。另有 1%（476 人中的 3 人）患者因数据集不完整或随访时间少于 6 个月而丢失，留下 8%（476 人中的 39 人）用于此处分析。平均患者年龄为 62 ± 14 岁，62%（39 人中的 24 人）为男性，18%（39 人中的 7 人）吸烟；87%（39 个中的 34 个）肿瘤为中/高级，最常见的组织学亚型是未分化多形性肉瘤。在调查并发症时，根据确定该值的试点调查选择了 25 mmHg 的截止值。所有患者都接受了手术伤口愈合并发症的评估，这些并发症被定义为：导致返回手术室、开始口服或静脉注射抗生素、对血清肿进行干预或伤口包扎或换药时间延长的并发症。为了回答第一个研究问题，我们比较了读数低于 25 mmHg 的患者（39 名中的 7 名）和未读数的患者（39 名中的 32 名）之间出现伤口愈合并发症的患者比例。要回答第二个问题，我们将皮肤氧合稳定或减少的组（37 名患者测量值中的 22 名 [两名患者错过了术后即时测量值]）与皮肤氧测量值增加的组（37 名测量值中的 15 名）在辐射结束和外科手术；同样，终点是伤口愈合并发症的发展。这项研究是先验的，以检测伤口愈合并发症的未调整比值比小至 0.71，TcO 增加五个单位（5 毫米汞柱）终点是伤口愈合并发症的发展。这项研究是先验的，以检测伤口愈合并发症的未调整比值比小至 0.71，TcO 增加五个单位（5 毫米汞柱）终点是伤口愈合并发症的发展。这项研究是先验的，以检测伤口愈合并发症的未调整比值比小至 0.71，TcO 增加五个单位（5 毫米汞柱）_组间为2，α 设为 0.05，β 设为 0.2，样本量为 40 名患者。

结果 

我们发现在所有时间点经皮氧测量值大于或等于 25 mmHg 的患者与一个或多个读数低于该阈值的患者相比，伤口愈合并发症的几率没有差异（优势比 0.27 [95% 置信度）区间 (CI) 0.05 至 1.63]；p = 0.15）。在放疗和手术之间恢复皮肤氧合的患者与未恢复皮肤氧合的患者之间，伤口愈合并发症的几率没有差异（OR 0.63 [95% CI 0.37 至 5.12]；p = 0.64）。

结论 

不能单独将经皮血氧测定视为预测伤口愈合并发症的可靠测试。这可能是因为经皮血氧饱和度仪对可能出现伤口愈合并发症的一小部分景观进行采样。在没有可靠的诊断测试的情况下，临床医生仍必须对手术时机做出最佳判断，并努力解决可改变的风险因素以避免并发症。悬而未决的问题是，这些并发症的根源是否存在皮肤灌注或氧合问题，这似乎很有可能。可以更广泛、更实时地评估伤口的替代方法，例如荧光探针，可能值得进一步研究。

证据等级 

II 级，诊断研究。