Chinese Journal of Physiology

: 2023  |  Volume : 66  |  Issue : 1  |  Page : 21--27

Preoperative anemia: Predictor of free flap reconstruction complications in head and neck cancer

Cheng Hung Tu, San Fu Hong 
 Department of ENT Head and Neck Surgery, Changhua Christian Hospital, Changhua, Taiwan

Correspondence Address:
Dr. San Fu Hong
Department of ENT Head and Neck Surgery, Changhua Christian Hospital, 135 Nanhsiao Street, Changhua 500


Free flap reconstruction has been the mainstay among reconstruction surgeries for head and neck cancer. Intraoperative and postoperative hemoglobin (Hb) levels were both possible risk factors of flap failure and had been discussed widely. However, few investigations of preoperative Hb were seen in the previous study with its effect to flap condition remain uncertain and no conclusions in the literature. Patients who underwent free flap reconstruction after head and neck surgery in our institution between May 2014 and May 2019 were enrolled. The postoperative flap condition was observed carefully, and re-exploration was performed if necessary. We then retrospectively collected patient data with several intraoperative and postoperative indices. A total of 598 patients were enrolled in our study. The total major flap complication rate was 10.6%, with an overall success rate of 89.4%. They were predominantly male (95%), and most of them underwent free flap reconstruction for the first time (91%). A total of 81 (13%) patients received radiotherapy before reconstruction. Among all factors, the preoperative Hb level and free flap type showed significance in univariate and multivariate analyses. A previous history of radiotherapy, body mass index, nutrition status, or poorly controlled diabetes mellitus showed no significant results in either univariate or multivariate analysis. Our study showed that a lower preoperative Hb level affects free flap survival. Meanwhile, preoperative radiotherapy history has no significant influence in either univariate or multivariate analysis.

How to cite this article:
Tu CH, Hong SF. Preoperative anemia: Predictor of free flap reconstruction complications in head and neck cancer.Chin J Physiol 2023;66:21-27

How to cite this URL:
Tu CH, Hong SF. Preoperative anemia: Predictor of free flap reconstruction complications in head and neck cancer. Chin J Physiol [serial online] 2023 [cited 2023 Mar 28 ];66:21-27
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Full Text


Head and neck squamous cell carcinomas (HNSCCs) cancer arises from the mucosal epithelium of the oral cavity. The incidence of head and neck cancers is increasing worldwide and is anticipated to increase by 30% by 2030.[1] The most important risk factors for HNSCCs are tobacco and alcohol consumption. Increasing evidence has documented human papillomavirus (HPV) as a cause of specific subsets of HNSCCs. HPV-positive HNSCC could be prevented by vaccination; however, HPV-negative HNSCC requires a physical examination for early detection.[2]

Wide excision of tumors is the most common treatment modality for oral cavity cancer and selected cases of oropharyngeal, hypopharyngeal, and laryngeal cancers. Many cases require free flap reconstruction when the tissue defect is too extensive.[3],[4] Anterolateral thigh (ALT) free flaps and radial forearm flap (FA) free flaps are frequently used for head and neck soft tissue reconstruction. The fibular flap was very useful in cases which needed bone reconstruction.[5],[6] However, free flap reconstruction, especially in the head and neck region, often carries a great risk of complications, including thromboembolic events requiring exploratory surgery, flap dehiscence, partial flap loss, and total flap loss, thus posing a great working load to medical staff and caregivers.

Several possible factors related to these adverse events have been described previously, including poor preoperative nutritional support,[7] prolonged operation time,[8],[9] preoperative anemia, previous radiation history in the operative field,[10],[11] and significant intraoperative blood loss. However, each of these factors has not shown a consistent effect on flap survival. Herein, we re-examined the possible risk factors that might cause free flap adverse events in a single institution retrospectively. A history of radiation therapy in the operative field, the preoperative body mass index (BMI), and the preoperative hemoglobin (Hb) level have all been associated with contradictory evidence of their effect on free flaps. Our study showed that a lower preoperative Hb level affects free flap survival. Meanwhile, preoperative radiotherapy history has no significant influence in either univariate or multivariate analysis.

 Materials and Methods


This study was approved by the Institutional Review Board of Changhua Christian Hospital (IRB220307). Patients who underwent microvascular free flap reconstruction after wide excision of a tumor, debridement of poorly healing wounds, or trismus postsubcondylar osteotomy between May 2014 and May 2019 in the Otolaryngology Head and Neck Surgery Department of Changhua Christian Hospital were included in this study.

Surgery and treatment

There were no exclusion criteria. Tumor excision and reconstruction were performed by two separate teams. Both teams included otolaryngology head and neck surgeons. We included FA, ALT, and fibular free flaps to reconstruct the defects. The patient's medical records were reviewed retrospectively, including the patient's age, sex, height, weight, tumor site, Hb levels preoperatively and on postoperative day 1, date of surgery, total operation time, total ischemia time, flap type (FA, ALT, fibular), and vascular anastomosis type (end-to-end and end-to-side). In general, patients were transferred to the ward after the surgery with only a few patients transferred to the intensive care unit (ICU) due to combinations with other major surgeries (e.g., esophageal reconstruction). We encouraged patients to engage in early mobilization after the surgery (<4 days). After the surgery, we avoided the use of tranexamic acid or vasoconstrictors but continued administering anticoagulant medications in patients with a previous cardiovascular history or stroke history. We checked each flap status immediately after transfer to the ear, nose, and throat (ENT) ward or ICU and then every 4 h routinely by nurses and several times a day by physicians.


In each checkup, we examined the flap color, flap texture, capillary refilling time, and Doppler sound. If prolonged compromised signs were observed, such as pale or congested flap appearance, delayed capillary refilling time, or absent Doppler sound, the patient was then suggested to undergo exploration for suspected thrombosis or embolism. During the exploration, venous thrombosis, arterial embolism, or the existence of both were recorded.


Statistical analysis was performed using IBM SPSS Statistics for Windows, Version 27.0 (IBM Corp., released 2020; Armonk, NY, USA) for the Student's t-test, Chi-squared test, Fisher's exact test, logistic regression, and Youden's index.


Patients characteristic and univariate model on free flap complications

A total of 623 consecutive patients in the ENT ward or Head and Neck Surgery Department at a single institution were retrospectively included in this study. The patients' characteristics are presented in [Table 1]. The median age was 56.0 (48.0–63.0) in the no complication group and 56.5 (51–62) in the complication group, with 528 (94.8%) male patients in the no complication group and 65 (98.5%) in the complication group. The median BMI was 23.2 (20.7–26.1) kg/m2 and 23.5 (21.6–27.1) kg/m2 in each group, respectively. Preoperative Hb level was 13.9 (12.3–15) g/dL and 13.2 (11.7–14.6) g/dL. Hb level on postoperative day 1 was 11.0 (9.9–12.3) g/dL and 10.6 (9.5–11.6), relative change in Hb was 18.8% (−36.8% to −45.0%), total blood loss was 300 (200–500) mL and 375 (250–600), operation time was 590 (205–1405) min and 602 (525–685) min, and flap size was 48 (35–64) cm2 and 52 (35–78) cm2. Eighty-two (13.2%) patients received radiotherapy before the surgery. The BMI was categorized as underweight, normal weight, preobesity, and obesity (Class I–III) according to the World Health Organization. Over half of the patients were within the normal weight category in both the no complication group and the complication group. In the preobesity category, both groups exceeded 25% (25.7% and 27.3%). Moreover, in the obesity category, both groups were <10% (7% and 4.5%). The underweight category both comprised nearly 10% of the patients (10.8% and 9.1%). The end-to-side venous anastomosis technique was used in only 10 (1.6%) patients. The primary tumors included in this study were mostly oral cancer and oropharyngeal cancer in 539 (87%) and 57 (9.1%) patients, respectively. Only 2 patients had hypopharyngeal cancer and 3 had nasopharyngeal cancer. ALT flap reconstruction was performed in 347 (57%) patients, radial FA flap was performed in 250 (40%) patients, and fibular bone flap was used in 26 patients (4%). Contralateral neck vessel anastomosis was performed in 41 (7%) patients. Major complications are shown in [Table 2], including 21 (3%) patients requiring exploratory surgery, 5 (0.8%) patients with flap dehiscence, 14 (2.2%) patients with partial flap failure, and 25 (4%) patients with total flap loss. The major flap complication rate was 10.6%, with an overall success rate of 89.4% [Table 1]. In the restricted cubic spline curve, preoperative Hb level, postoperative Hb level, absolute change of Hb level, and relative change of Hb level were all associated with decreased flap failure odds ratio as Hb level increased [Figure 1]. Both the preoperative Hb level and postoperative Hb level were stratified into different categories. While in preoperative Hb level, both groups of Hb lower than 12.3 and Hb level between 12.3 and 13.8 had increased crude odds ratio (OR), postoperative Hb level was only associated with significant increased risk of free flap complication in the group of Hb level <10.3 [Figure 2]. Importantly, in multivariate analysis, only preoperative Hb level <13.8 remained significant [Figure 3]a. Postoperative Hb level [Figure 3]b, primary tumor site, and free flap type did not significantly increase the risk of major complications. The subcategory within [Table 2] is mutually exclusive. In univariate analysis, preoperative Hb level, postoperative Hb level (24 h within operation), total blood loss, primary tumor site, and free flap type showed statistically significant differences. The sex, BMI, nutrition status, and diabetes mellitus showed no significant differences. In multivariate analysis, only preoperative Hb level remained significant.{Figure 1}{Figure 2}{Figure 3}{Table 1}{Table 2}


Head and neck cancers that require free flap reconstruction often exhibit extensive soft tissue loss during tumor excision. The survival of the transferred free flap is extremely essential to both the functional and cosmetic outcomes in patients. Our team has an overall success rate comparable to other facilities.[12] Nevertheless, we examined several risk factors that are potentially related to the overall condition of free flaps.

Our study revealed that obese patients were not associated with increased complications than normal weight or underweight patients. Clinically, we did found that obese patients' vessel networks appear to be more complex and comprise smaller vessel diameters, hence increasing the technical difficulty while performing the anastomosis. However, this difficulty could be overcome by increased operation experience. Previous studies have shown conflicting evidence regarding whether BMI affects the flap survival rate. Two studies in which patients with combined breast and nonbreast cancer who underwent free flap reconstruction both showed that a higher BMI is associated with poorer outcomes in terms of the flap survival rate, specifically related to breast reconstruction flaps but not nonbreast reconstruction flaps.[13],[14] Another retrospective study of 259 patients with head and neck cancer who underwent free flap reconstruction demonstrated that the BMI is not associated with increased flap failure or other possible surgical complications, such as wound infection or pharyngocutaneous fistula.[15] In contrast, a retrospective analysis of the American College of Surgeons National Surgical Quality Improvement Program database of 5951 patients showed BMI as one of the factors associated with complications, including flap failure. However, the authors also concluded that owing to greater than 34% of the study population being obese, obesity should not be a contraindication. The operation time within this study showed no differences in the complication risk. However, a literature review of factors related to poorer free flap outcomes suggested that an operation time longer than 11 h is associated with major flap complications.[8] Based on the literature, a longer operation time often indicates a more complicated disease and longer ischemia time. Our study showed longer median and mean operation times in patients with complications, but these were not statistically significant. Nevertheless, the short ischemia times in our patients were well within hazardous limits, and thus, no survival difference was shown in the results.

Blood transfusion is a postoperative management approach often performed in clinical practice. A study of the transfusion protocol for patients with head and neck cancers who underwent neck dissection and free flap reconstructions found that nearly 30% of all patients who underwent free flap reconstruction received transfusions postoperatively.[16] A recent study, also focusing on the same population, indicated that the perioperative lowest Hb level is associated with flap failure.[17] The results in the same study indicated a Hb threshold of 8.75 g/dL, which is the lowest level at which transfusion is initiated.[17] Another study of double free flap transfers also indicated a comparable transfusion threshold (hematocrit level of 25%).[6] In our study, a low postoperative Hb level (<10.3 g/dL) showed a tendency toward flap complications in univariate analysis but not in multivariate analysis. Thus, we concluded that transfusion is encouraged in conditions when necessary. Nevertheless, although transfusion is not associated with an increased risk of free flap failure, according to previous studies,[17] it is still related to increased wound infection rates, increased risks of readmission, and increased risks of medical comorbidities with >3 blood transfusions.[18] Clinicians should be aware of the risks and provide blood transfusions only when necessary. With a close follow-up of Hb levels during the surgery and postoperatively and providing judicious blood transfusion if Hb levels are <10 g/dL, it is not surprising that the postoperative Hb levels showed little significance in our study.

Meanwhile, preoperative Hb levels are a multifactorial-related index that could be easily affected by a patient's nutritional status, renal function, and even smoking status; thus, Hb levels are likely not the result of a single factor. However, we observed a significant decrease in the flap complication rate in the higher preoperative level group. A possible explanation for this is that a higher preoperative Hb level indicates a more robust overall patient condition. Second, a lower Hb level may have had a possible negative effect on free tissue transfer. Hill et al. observed a similar finding in a study that included 156 free flaps in 147 patients.[19] They proposed a possible physiological mechanism to support this result by explaining the change in the Reynolds number of laminar flow. When a patient has anemia, the blood viscosity decreases, which in turn increases the Reynolds number and transforms the laminar flow into turbulent flow, thus increasing the possibility of thrombosis. Thrombus then leads to revisiting the operation room within days after surgery and possibly causing partial and total flap failure.

Conflicting data exist in previous reports about the effects of preoperative radiotherapy on free flap reconstruction. In 2018, a study including 344 patients showed a greater proportion of total flap loss among irradiated patients than that among nonirradiated patients.[11] Another study of the national Diagnosis Procedure Combination Database of Japan including 2846 patients also suggested preoperative radiotherapy as an indicator of flap loss.[20] In contrast, a case series of double flap reconstruction in 45 patients accounting for 90 free flaps concluded that preoperative radiotherapy is not related to more complications, including flap failure.[21] Similarly, another two single-institution studies with substantial numbers of patients in Taiwan showed that irradiated patients had the same failure rate compared to that of nonirradiated patients.[22],[23] Both studies concluded that free flap transfer is safe in patients with head and neck cancers who receive radiotherapy. Our current study showed no significant effect of preoperative radiotherapy on free flap complications. While the impact of previous radiation has been substantially discussed in previous reports, very few have discussed the impact of radiation dosage and elapsed time from radiation to surgery. Since both factors may have a potential effect on the survival of the transferred flap, our earlier unpublished analysis of these two factors failed to exhibit significance. Currently, it is not clear how preoperative radiotherapy affects the flap survival rate.

The flap size is not related to the flap survival rate, according to a previous report. In a retrospective study of 121 patients who underwent head and neck free tissue reconstructions, very-large-area flaps (>200 cm2) did not negatively affect clinical outcomes compared with large-area flaps (100–199 cm2).[24] All our flap sizes were smaller than 200 cm2; thus, it is understandable that the flap size is not a significant factor related to flap survival.

In addition, our results showed a higher survival rate associated with FA flaps than that associated with ALT flaps in univariate and multivariate analyses. A recent study by Sweeny et al. also showed a slightly higher survival trend associated with FA flaps than that associated with ALT flaps, although the difference was not statistically significant.[25] Similarly, Oranges et al. also discovered a higher microsurgical success rate with a radial FA flap than with an ALT flap, although the difference was not statistically significant.[26]

Decreased donor site function is observed with ALT flaps compared to that with radial FA flaps.[27] Our department also adjusted the preference with increasing the use of ALT flaps and decreasing the use of radial FA flaps in recent years.

First, strong risk of bias of gender is inevitable in our Taiwan due to most consumers of betel nuts, cigarettes, and alcohol were mostly men. According to Taiwan Health Promotion Administration, Ministry of Health and Welfare report, the number of male patients is 10 times greater than female patients. Second, due to the low failure rate, we could not achieve sufficient statistical power to predict total flap failure.


In this study, we further confirmed the significant impact of preoperative anemia on the free-flap complication rate. Radial free-FA flaps were less likely to be associated with complications in our study.

Author contributions

CHT contributed to draft and design, acquisition of data, or analysis and interpretation of data. SFH revised the article, final approval of the version to be published, and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.


This research received financial support from Changhua Christian Hospital (Y-111-0094) offered to San Fu Hong.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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