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Predictors of mortality in the surgical intensive care unit among non-cardiac surgery patients receiving transfusion
1Internal Medicine Department of Hematology, School of Medicine, Ministry of Health Bursa City Hospital, 16110 Bursa, Turkey
2Internal Medicine, Istanbul Medipol University School of Medicine, 34214 Istanbul, Turkey
3Department of Anesthesiology and Reanimation, Istanbul Medipol University School of Medicine, 34214 Istanbul, Turkey
*Corresponding Author(s):sevil.sadri@saglik.gov.tr (Sevil Sadri)
| History | Submitted: 31 July 2024 | Accepted: 12 November 2024 | Published: 08 May 2025 |
| Copyright: | ©2025 The Author(s). Published by MRE Press. |
Background: Postoperative complications are a major contributor to increased mortality rates, which can be reduced by monitoring and managing high-risk patients in the intensive care unit (ICU) following surgery. Methods: This retrospective analysis reviewed the records of patients who underwent non-cardiac surgery and received postoperative follow-up care in the ICU between January 2021 and March 2022 using collected demographic data, hematologic parameters, and the number of transfusions performed in the ICU to assess their impact on postoperative mortality. Results: The mean ICU length of stay was longer in patients who received red blood cell (RBC) transfusions (4.03 ± 6.09 days) compared to those who did not. Patients without RBC transfusions were more likely to have preoperative hemoglobin (Hb) levels >10 g/dL (n = 290, 80.8%). Several factors, including ICU length of stay, need for and duration of mechanical ventilation, preoperative Hb levels, platelet (PLT) counts, and American Society of Anesthesiologists (ASA) scores, were significantly associated with mortality (p < 0.05). Mortality was higher in patients with preoperative Hb levels <7.5 g/dL (n = 4, 25%) and in those with Hb levels <10 g/dL on ICU day one and at discharge (p < 0.05). Low Hb levels were strongly associated with increased mortality. Similarly, low PLT counts demonstrated a significant association with mortality (p < 0.001), and patients with an ASA score above 2 had significantly higher mortality rates (p < 0.001). Conclusions: Anemia was identified as an independent risk factor for adverse outcomes after non-cardiac surgery. While RBC transfusions were associated with poor prognosis, this association was not observed in patients with moderate-to-severe anemia. PLT transfusion was found to be a significant risk factor for mortality. These findings suggest the importance of careful preoperative planning and multidisciplinary management to minimize postoperative transfusion requirements.
Cite this article
Sevil Sadri, Bora Sahin, Burcu Tunay. Predictors of mortality in the surgical intensive care unit among non-cardiac surgery patients receiving transfusion. Signa Vitae. 2025; 21(5): 68-78. doi: 10.22514/sv.2025.068
1. Introduction
Postoperative complications are a leading contributor to increased mortality rates, and the follow-up of high-risk patients in the intensive care unit (ICU) after surgery has been shown to reduce mortality [1]. Previous studies indicate that fewer than 15% of high-risk surgical patients require intensive care [2]. However, the demand for ICU care continues to rise due to an aging population with multiple comorbidities, despite advancements in medical science. Therefore, greater efforts are needed to prevent, promptly identify and effectively manage potentially life-threatening postoperative complications.
Several perioperative risk scores and prediction models have been developed to estimate postoperative risks. Among these, the American Society of Anesthesiologists Physical Status (ASA-PS) score remains the most widely used. However, its ability to predict individualized risks of adverse outcomes is limited [3]. Anemia is a common condition among surgical ICU patients [4, 5], and it has been significantly linked to increased mortality [6]. For instance, a study involving 821 patients demonstrated that the 30-day survival rate was higher in patients who received transfusions compared to those who did not [4], which highlights the importance of evaluating the impact of blood transfusions and refining approaches to transfusion preparation and administration.
The present study retrospectively analyzed data from the ICU of our hospital to identify predictors of blood transfusion-related outcomes and mortality in the surgical ICU (SICU). The primary outcome measure was the need for perioperative packed red blood cell (RBC) transfusions. Secondary outcome measures included the length of ICU stay, in-hospital mortality from all causes, and an approximate calculation of transfusion costs based on the quantity of blood products transfused and their unit cost.
2. Methods
This study was approved by the Ethics Committee of Medipol University Hospital (Ethics approval no: E-10840098-772.02-2981). The retrospective nature of the study and its use of anonymized data eliminated the need for informed consent.
All adult patients (>18 years) admitted to the inpatient ICU between January 2021 and March 2022 were retrospectively analyzed. Data were extracted from bedside monitors, ventilators, and the clinical information system. The recorded parameters included patients’ age, sex, type of surgical procedure, comorbidities, medications and laboratory data. For patients with multiple ICU admissions, only data from the first admission were included. ASA scores were determined by the intensive care physician on the first day of ICU admission. Hospital records were reviewed to document discharge dates and in-hospital mortality.
In our hospital, all RBC and platelet (PLT) transfusions are electronically recorded, enabling precise documentation of the number of transfusions received by each patient during their ICU stay. Blood transfusion decisions were made by the primary intensive care physician, with the targeted hemoglobin (Hb) range set at 7–9 g/dL during hospitalization. In patients with comorbidities such as ischemic heart disease or hypoperfusion, the targeted Hb level was >9 g/dL. Physicians also conducted routine quality assessments of blood transfusions, and staff underwent regular training to maintain transfusion standards. The records of patients who underwent non-cardiac surgery and received postoperative follow-up care in the SICU between January 2021 and March 2022 were reviewed. Data collected included patients’ demographic characteristics, hematologic parameters and the number of transfusions received in the ICU, which were analyzed for their association with postoperative mortality. Subgroup analyses were performed based on Hb levels (<7 g/dL, 7–10 g/dL and >10 g/dL) and PLT counts (<80,000/mcL and >80,000/mcL) to evaluate the relationship between these parameters and mortality outcomes.
The decision to administer transfusions was made by the attending physicians, with the target Hb range set between 7 and 9 g/dL during the ICU stay. Data on intraoperative transfusions were not included in this analysis; only transfusions administered during the ICU period were recorded and evaluated.
3. Statistical analysis
The data were analyzed using IBM SPSS version 25 (IBM Corporation, Armonk, NY, USA). Categorical variables are presented as percentages, while continuous variables are reported as medians or mean ± standard deviation (SD). The Chi-square or Fisher’s exact tests were used to analyze categorical variables. Normally distributed continuous variables were compared using the Student’s t-test, whereas non-normally distributed variables were analyzed using the Mann-Whitney U test. Age, sex, clinical characteristics and laboratory results were initially assessed using univariate logistic regression (LR). Variables identified as significant in the univariate analysis were further analyzed using stepwise multivariate LR (Enter method). The assumption of homogeneity was tested using Levene’s Test of Equality of Error Variances. For parameters with repeated measurements, intragroup comparisons were performed using repeated measures Analysis of variance (ANOVA) Test. p < 0.05 was considered statistically significant.
4. Results
The sociodemographic and clinical characteristics of the patients are summarized in Table 1. Among the study cohort, 367 patients (56.2%) were male and 286 (43.8%) were female. The mean age was 60.59 ± 14.41 years, ranging from 19 to 93 years. 71.9% of the patients were operated on due to diagnosis of cancer and 28.1% were transferred to intensive care in the postoperative period due to other reasons. Regarding comorbidities, there were 38.5% diabetes mellitus, 48.7% ischemic heart disease, 10.4% chronic obstructive pulmonary disease and 2.4% hematological malignancy. Of the patients, 292 (44.7%) received RBC transfusions, 25 (3.8%) received PLT transfusions and 131 (20.1%) required mechanical ventilation. The mean duration of mechanical ventilation was 8.33 ± 5.05 days. An ASA score above 2 was documented in 219 patients (33.6%) and 282 patients (43.2%) had at least one comorbidity. Mean Hb levels were 11.27 ± 4.10 g/dL preoperatively, 10.25 ± 1.73 g/dL on ICU day one, and 10.12 ± 1.69 g/dL at discharge. Mean PLT counts were 239.43 ± 129.15 × 109/L preoperatively, 221.17 ± 189.59 × 109/L on ICU day one and 211.84 ± 117.66 × 109/L at discharge.
| Variables | n (%) | |
| Sex | ||
| Female | 286 (43.8) | |
| Male | 367 (56.2) | |
| Age (mean ± SD) | 60.59 ± 14.41 | |
| RBC (mean ± SD) | 4.70 ± 4.41 | |
| Received RBC transfusion | 292 (44.7) | |
| Not received RBC transfusion | 361 (55.3) | |
| PLT (mean ± SD) | 0.12 ± 0.09 | |
| Received PLT transfusion | 25 (3.8) | |
| Not received PLT transfusion | 628 (96.2) | |
| Length of stay in the ICU (d) (mean ± SD) | 3.81 ± 3.55 | |
| Length of mechanical ventilation (d) (mean ± SD) | 8.33 ± 5.05 | |
| Received mechanical ventilation | 131 (20.1) | |
| Not received mechanical ventilation | 522 (79.9) | |
| ASA score (mean ± SD) | 2.32 ± 0.84 | |
| ASA Score ≤2 | 433 (66.4) | |
| ASA Score >2 | 219 (33.6) | |
| Medication | ||
| Aspirin | 1 (0.2) | |
| Warfarin | 3 (0.5) | |
| DOAC | 2 (0.3) | |
| LMWH | 585 (99.0) | |
| Comorbidities | ||
| Absent | 371 (56.8) | |
| Present | 282 (43.2) | |
| Preoperative Hb (g/dL) | ||
| <7.5 | 16 (2.5) | |
| 7.5–10 | 183 (28.1) | |
| >10 | 452 (69.4) | |
| Preoperative Hb (mean ± SD) | 11.27 ± 4.10 | |
| Hb (g/dL) on day one of the ICU | ||
| <7.5 | 18 (2.8) | |
| 7.5–10 | 315 (48.4) | |
| >10 | 318 (48.8) | |
| Hb on day one of the ICU (mean ± SD) | 10.25 ± 1.73 | |
| Hb (g/dL) at discharge from the ICU | ||
| <7.5 | 15 (2.3) | |
| 7.5–10 | 352 (54.2) | |
| >10 | 283 (43.5) | |
| Hb at discharge from the ICU: (mean ± SD) | 10.12 ± 1.69 | |
| PLT preoperative (×106) | ||
| <80 | 30 (4.6) | |
| >80 | 621 (95.4) | |
| Preoperative PLT (mean ± SD) | 239.43 ± 129.15 | |
| PLT on day one of the ICU | ||
| <80 | 29 (4.5) | |
| >80 | 622 (95.5) | |
| PLT on day one of the ICU (mean ± SD) | 221.17 ± 189.59 | |
| PLT at discharge from the ICU | ||
| <80 | 36 (5.5) | |
| >80 | 614 (94.5) | |
| PLT at discharge from the ICU (mean ± SD) | 211.84 ± 117.66 | |
| Overall mortality | ||
| Discharge | 621 (95.1) | |
| Died | 32 (4.9) | |
| 30-day mortality | ||
| Discharge | 628 (96.2) | |
| Died | 25 (3.8) | |
SD: Standard Deviation; RBC: red blood cell; PLT: platelet; ICU: intensive care unit; ASA: American Society of Anesthesiologists; Hb: hemoglobin; DOAC: Direct Oral Anticoagulant; LMWH: Low molecular weight heparin. |
Patients who received RBC transfusions were compared to those who did not in terms of sociodemographic and clinical characteristics (Table 2). Statistically significant differences were observed between the two groups in age, ICU length of stay, Hb levels and the frequency of PLT transfusions (p < 0.05). The mean age of patients who received RBC transfusions was 61.82 ± 13.77 years, which was significantly higher than the mean age of those who did not receive transfusions. Similarly, the mean ICU length of stay was longer in the RBC transfusion group, at 4.03 ± 6.09 days, compared to the non-transfusion group. Patients who did not receive RBC transfusions were more likely to have preoperative Hb levels >10 g/dL (n = 290, 80.8%). These patients also maintained Hb levels >10 g/dL on the first day in the ICU and at discharge, with significant differences observed (p < 0.05). Notably, all patients who received PLT transfusions also received RBC transfusions, indicating a close relationship between the need for PLT transfusion and RBC administration.
| Variables | Did not receive RBC (n = 361) | Received RBC (n = 292) | p | |
| n (%) | n (%) | |||
| Sex | ||||
| Female | 145 (40.2) | 141 (48.3) | 0.038* | |
| Male | 216 (59.8) | 151 (51.7) | ||
| Age (mean ± SD) | 59.60 ± 14.85 | 61.82 ± 13.77 | 0.048† | |
| Comorbidity | ||||
| Absent | 208 (57.6) | 163 (55.8) | 0.645* | |
| Present | 153 (42.4) | 129 (44.2) | ||
| Length of ICU stay (mean ± SD) | 3.63 ± 8.55 | 4.03 ± 6.09 | <0.001‡ | |
| Hb_preoperative | ||||
| <7.5 | 5 (1.4) | 11 (3.8) | <0.001* | |
| 7.5–10 | 64 (17.8) | 119 (40.8) | ||
| >10 | 290 (80.8) | 162 (55.5) | ||
| Hb_day one | ||||
| <7.5 | 9 (2.5) | 9 (3.1) | <0.001* | |
| 7.5–10 | 147 (40.9) | 168 (57.5) | ||
| >10 | 203 (56.5) | 115 (39.4) | ||
| Hb at discharge | ||||
| <7.5 | 7 (2.0) | 8 (2.7) | <0.001* | |
| 7.5–10 | 163 (45.5) | 189 (64.7) | ||
| >10 | 188 (52.5) | 95 (32.5) | ||
| PLT preoperative | ||||
| <80 | 15 (4.2) | 15 (5.1) | 0.562* | |
| >80 | 344 (95.8) | 277 (94.9) | ||
| PLT on day one | ||||
| <80 | 15 (4.2) | 14 (4.8) | 0.705* | |
| >80 | 344 (95.8) | 278 (95.2) | ||
| PLT at discharge | ||||
| <80 | 15 (4.2) | 21 (7.2) | 0.096* | |
| >80 | 343 (95.8) | 271 (92.8) | ||
| ASA_Score | ||||
| <2 | 247 (68.6) | 186 (63.7) | 0.187* | |
| >2 | 113 (31.4) | 106 (36.3) | ||
| PLT | ||||
| Received | 0 (0) | 25 (8.6) | <0.001* | |
| Not Received | 361 (100) | 267 (91.4) | ||
| Mechanical ventilation | ||||
| Received | 68 (18.8) | 63 (21.6) | 0.385* | |
| Not Received | 293 (81.2) | 229 (78.4) | ||
| Outcome in the ICU | ||||
| Discharged | 343 (95) | 278 (95.2) | 0.918* | |
| Died | 18 (5) | 14 (4.8) | ||
| 30-day mortality | ||||
| Discharged | 346 (95.8) | 282 (96.6) | 0.629* | |
| Died | 15 (4.2) | 10 (3.4) | ||
*p value was obtained from Fisher Exact or Chi-square test. |
The association between sociodemographic and clinical characteristics and mortality was analyzed (Table 3), and the results demonstrated statistically significant relationships between mortality and length of ICU stay, the need for and duration of mechanical ventilation, Hb levels, PLT count and ASA scores (p < 0.05). The mean length of ICU stay was significantly higher among patients who died (15.18 ± 20.82 days) compared to those who were discharged. Similarly, the mean duration of mechanical ventilation was longer in patients who died (14.52 ± 20.17 days), and mortality was more frequently observed in patients with preoperative Hb levels <7.5 g/dL (n = 4, 25%) and in those with Hb levels <10 g/dL on ICU day one and at discharge (p < 0.05). Low Hb levels were significantly associated with increased mortality risk. In addition, a strong association was observed between low PLT counts and mortality (p < 0.001). Patients with an ASA score above 2 also exhibited significantly higher mortality rates (p < 0.001).
| Variables | Survivor (n = 621) | Died (n = 32) | p | |
| n (%) | n (%) | |||
| Sex | ||||
| Female | 270 (43.3) | 16 (50.0) | 0.462* | |
| Male | 351 (56.7) | 16 (50.0) | ||
| Age (mean ± SD) | 60.55 ± 14.30 | 61.41 ± 16.75 | 0.744† | |
| Length of stay in the ICU (mean ± SD) | 3.22 ± 5.59 | 15.18 ± 20.82 | <0.001‡ | |
| Mechanical ventilation | ||||
| Received | 100 (16.1) | 31 (96.9) | <0.001* | |
| Not Received | 521 (83.9) | 1 (3.1) | ||
| Length of ventilation (d) (mean ± SD) | 6.41 ± 12.58 | 14.52 ± 20.17 | 0.024‡ | |
| PLT | ||||
| Received | 22 (3.5) | 3 (9.4) | 0.094* | |
| Not Received | 599 (96.5) | 29 (90.6) | ||
| RBC | ||||
| Received | 277 (44.8) | 14 (4.8) | 0.918* | |
| Not Received | 343 (55.2) | 18 (5.0) | ||
| Comorbidity | ||||
| Absent | 352 (56.8) | 18 (4.9) | 0.953* | |
| Present | 268 (43.2) | 14 (5.0) | ||
| Hb_preoperative | ||||
| <7.5 | 12 (2.0) | 4 (12.5) | <0.001* | |
| 7.5–10 | 170 (27.5) | 13 (40.6) | ||
| >10 | 436 (70.5) | 15 (46.9) | ||
| Hb_day one | ||||
| <7.5 | 13 (2.1) | 5 (15.6) | <0.001* | |
| 7.5–10 | 306 (49.4) | 9 (28.1) | ||
| >10 | 299 (48.5) | 18 (56.3) | ||
| Hb at discharge | ||||
| <7.5 | 10 (1.6) | 5 (15.6) | <0.001* | |
| 7.5–10 | 337 (54.5) | 15 (46.9) | ||
| >10 | 270 (43.9) | 12 (37.5) | ||
| PLT_preoperative | ||||
| <80 | 23 (3.7) | 7 (21.9) | <0.001* | |
| >80 | 597 (96.3) | 25 (78.1) | ||
| PLT_day one | ||||
| <80 | 21 (3.4) | 8 (25.0) | <0.001* | |
| >80 | 596 (96.6) | 24 (75.0) | ||
| PLT_discharge | ||||
| <80 | 21 (3.4) | 15 (46.9) | <0.001* | |
| >80 | 597 (96.6) | 17 (53.1) | ||
| ASA_Score | ||||
| <2 | 430 (69.5) | 2 (6.3) | <0.001* | |
| >2 | 189 (30.5) | 30 (93.8) | ||
*p value was obtained from Fisher Exact or Chi-Square test. |
Univariate LR analysis identified mechanical ventilation, ASA score, Hb levels and PLT counts as significant predictors of mortality (p < 0.05) (Table 4). Patients requiring mechanical ventilation demonstrated a 161.20-fold increased risk of mortality (95% CI (confidence interval): 21.76–1194.45; p < 0.001). Similarly, an ASA score above 2 was associated with a 34.13-fold higher risk of mortality (95% CI: 8.07–144.26; p < 0.001). Preoperative Hb levels also showed a strong association with mortality. Patients with preoperative Hb levels between 7.5 and 10 g/dL had a 9.69-fold increased mortality risk compared to those with Hb levels >10 g/dL (95% CI: 2.80–33.59). For patients with preoperative Hb levels <7.5 g/dL, the mortality risk was 2.22 times higher than in those with Hb levels >10 g/dL (95% CI: 1.04–4.77; p < 0.05). Hb levels on ICU day one and at discharge were similarly predictive of mortality. Patients with Hb levels <7.5 g/dL on ICU day one had a 6.39-fold increased risk of mortality compared to those with Hb levels >10 g/dL on day one (95% CI: 2.05–19.89; p = 0.001). Additionally, patients with Hb levels <7.5 g/dL at discharge had an 11.25-fold increased mortality risk compared to those with Hb levels >10 g/dL at discharge (95% CI: 3.32–38.08; p = 0.001). PLT counts also showed a significant relationship with mortality. Patients with preoperative PLT counts <80 × 109/L had a 7.24-fold higher mortality risk compared to those with PLT counts >80 × 109/L (95% CI: 2.84–18.47; p < 0.001). For PLT counts measured on ICU day one, a value <80 × 109/L was associated with a 9.48-fold increased risk of mortality compared to counts >80 × 109/L (95% CI: 3.81–23.56; p < 0.001). At discharge, a PLT count <80 × 109/L was found to be associated with a 25.04-fold increased risk of mortality compared to counts >80 × 109/L (95% CI: 11.04–56.83; p < 0.001).
| Variables | Univariate LR | Multivariate LR | |||
| OR (95% CI) | p | OR (95% CI) | p | ||
| Sex (Male) | 0.77 (0.38–1.57) | 0.469 | |||
| Age >65 yr | 0.58 (0.28–1.18) | 0.130 | |||
| RBC transfusion | 0.96 (0.47–1.97) | 0.910 | |||
| PLT transfusion | 2.81 (0.80–9.94) | 0.108 | |||
| Mechanical ventilation | 161.20 (21.76–1194.45) | <0.001 | 95.21 (12.55–721.92) | <0.001 | |
| Comorbidity | 1.02 (0.50–2.09) | 0.953 | |||
| ASA Score >2 | 34.13 (8.07–144.26) | <0.001 | 20.79 (4.36–99.06) | <0.001 | |
| Hb_preop (ref >10) | 0.001 | ||||
| 7.5–10 | 9.69 (2.80–33.59) | <0.001 | |||
| <7.5 | 2.22 (1.04–4.77) | 0.040 | |||
| Hb_day one (ref >10) | <0.001 | ||||
| 7.5–10 | 0.49 (0.21–1.11) | 0.085 | |||
| <7.5 | 6.39 (2.05–19.89) | 0.001 | |||
| Hb_discharge (ref >10) | <0.001 | ||||
| 7.5–10 | 1.01 (0.46–2.18) | 0.997 | |||
| <7.5 | 11.25 (3.32–38.08) | 0.001 | |||
| PLT_preop (ref >80) | 7.24 (2.84–18.47) | <0.001 | |||
| PLT_First day in ICU (ref >80) | 9.48 (3.81–23.56) | <0.001 | |||
| PLT_discharge (ref >80) | 25.04 (11.04–56.83) | <0.001 | |||
RBC: red blood cell; PLT: platelet; ICU: intensive care unit; ASA: American Society of Anesthesiologists; Hb: hemoglobin; LR: logistic regression; OR: odds ratio; CI: confidence interval; ref: reference. |
Univariate LR analysis identified mechanical ventilation, ASA score, Hb level and PLT count as statistically significant predictors of 30-day mortality (p < 0.05) (Table 5). Patients who required mechanical ventilation had a significantly higher 30-day mortality risk, with an odds ratio (OR) of 116.86 (95% CI: 15.64–873.18; p < 0.001), compared to those who did not require mechanical ventilation. Similarly, patients with an ASA score >2 exhibited a 53.17 times greater 30-day mortality risk (95% CI: 7.14–395.83; p < 0.001). Hb levels also demonstrated a strong association with 30-day mortality. Patients with preoperative Hb levels <7.5 g/dL had a 13.36-fold increased risk (95% CI: 3.72–48.07; p < 0.001) compared to those with preoperative Hb levels >10 g/dL. On ICU day one, a Hb level <7.5 g/dL was associated with a 7.76-fold higher 30-day mortality risk (95% CI: 2.45–24.64; p < 0.001) compared to Hb levels >10 g/dL. Similarly, patients with a Hb level <7.5 g/dL at discharge had an 11.29-fold increased risk (95% CI: 3.34–38.22; p < 0.001) compared to those with Hb levels >10 g/dL at discharge. Low PLT counts were also significant predictors of 30-day mortality. Patients with preoperative PLT counts <80 × 109/L had a 10.20-fold higher risk (95% CI: 3.87–26.82; p < 0.001) compared to those with counts >80 × 109/L. On ICU day one, a PLT count <80 × 109/L was associated with a 10.68-fold increased 30-day mortality risk (95% CI: 4.04–28.20; p < 0.001) compared to counts >80 × 109/L. At discharge, patients with PLT counts <80 × 109/L exhibited a 15.36-fold higher mortality risk (95% CI: 6.30–37.45; p < 0.001) compared to those with counts >80 × 109/L at discharge.
| Variables | Univariate LR | Multivariate LR | |||
| OR (95% CI) | p | OR (95% CI) | p | ||
| Sex (Male) | 1.19 (0.54–2.66) | 0.666 | |||
| Age >65 yr | 1.71 (0.76–3.83) | 0.192 | |||
| RBC transfusion | 0.82 (0.36–1.85) | 0.629 | |||
| PLT transfusion | 1.05 (0.14–8.08) | 0.964 | |||
| Mechanical ventilation | 116.86 (15.64–873.18) | <0.001 | 171.81 (11.63–2537.75) | <0.001 | |
| Comorbidity | 1.22 (0.55–2.73) | 0.621 | |||
| ASA Score >2 | 53.17 (7.14–395.83) | <0.001 | 35.19 (3.53–350.62) | 0.002 | |
| Hb_preop (ref >10) | <0.001 | 0.296 | |||
| 7.5–10 | 2.32 (0.97–5.55) | 0.060 | 0.19 (0.01–3.72) | 0.272 | |
| <7.5 | 13.36 (3.72–48.07) | <0.001 | 0.11 (0.01–2.08) | 0.142 | |
| Hb_day one (ref >10) | <0.001 | 0.177 | |||
| 7.5–10 | 0.33 (0.12–0.91) | 0.032 | 12.39 (0.44–352.16) | 0.141 | |
| <7.5 | 7.76 (2.45–24.64) | <0.001 | 22.28 (0.79–626.96) | 0.068 | |
| Hb_discharge (ref >10) | <0.001 | 0.003 | |||
| 7.5–10 | 0.53 (0.21–1.30) | 0.165 | 0.01 (0.01–0.14) | 0.002 | |
| <7.5 | 11.29 (3.34–38.22) | <0.001 | 0.03 (0.01–0.66) | 0.027 | |
| PLT_Preop (ref >80) | 10.20 (3.87–26.82) | <0.001 | 0.53 (0.05–5.12) | 0.581 | |
| PLT_day one of ICU (ref >80) | 10.68 (4.04–28.20) | <0.001 | 1.89 (0.21–17.01) | 0.570 | |
| PLT_discharge (ref >80) | 15.36 (6.30–37.45) | <0.001 | 0.14 (0.02–0.84) | 0.032 | |
RBC: red blood cell; PLT: platelet; ICU: intensive care unit; ASA: American Society of Anesthesiologists; Hb: hemoglobin; LR: logistic regression; OR: odds ratio; CI: confident interval; ref: reference. |
Repeated measurements of Hb and PLT levels were analyzed using intra-group comparisons for patients who survived and were discharged and for those who died (Table 6). The results showed that in patients who were discharged, their Hb levels showed significant variation over time (p = 0.001). The mean preoperative Hb level in this group was 11.33 ± 4.16 g/dL, which decreased significantly to 10.24 ± 1.66 g/dL on ICU day one and remained significantly lower at 10.13 ± 1.6 g/dL at discharge. In patients who died, PLT levels exhibited significant variation over time (p = 0.001). The mean preoperative PLT count was 251.28 ± 217.82 × 109/L, which decreased significantly to 174.16 ± 112.26 × 109/L on ICU day one and further declined significantly to 140.88 ± 159 × 109/L at discharge (p = 0.016).
| Variables | Discharge | Died |
| Mean ± SD | Mean ± SD | |
| Preop Hb | a11.33 ± 4.16 | 10.05 ± 2.67 |
| Hb on day one of the ICU | b10.24 ± 1.66 | 10.34 ± 2.87 |
| Hb at discharge from the ICU | c10.13 ± 1.60 | 9.97 ± 2.91 |
| p* | 0.001 | 0.540 |
| Preop PLT | 238.78 ± 123.21 | a251.28 ± 217.82 |
| PLT on day one of the ICU | 223.54 ± 295.96 | b174.16 ± 112.26 |
| PLT at discharge from the ICU | 215.44 ± 114.16 | b140.88 ± 159.00 |
| p* | 0.083 | 0.016 |
*p value was obtained from Repeated ANOVA test, a,b,c: Different
lower-case superscript letters indicate significant differences among the
repeated measures. |
5. Discussion
This study revealed significant findings. First, adult patients undergoing elective non-cardiac surgery at our center exhibited a remarkably high prevalence of preoperative anemia. Most patients in our cohort met the World Health Organization (WHO) criteria for anemia, with Hb levels indicative of anemia observed in over 50% of the sample. This prevalence significantly exceeds values reported in prior literature and was an unexpected finding. Although the underlying causes and duration of preoperative anemia were not determined, our results suggest a close relationship between anemia, aging, the severity of comorbidities and the complexity of the presenting surgical condition. Second, preoperative anemia was a significant and independent predictor of perioperative RBC transfusion. Among anemic patients, 94.5% demonstrated a three-and-a-half-fold increased likelihood of receiving perioperative transfusions, even when the anemia was mild (Hb ≥10 g/dL). This increased transfusion incidence in the anemic group also contributed to substantially higher financial costs associated with their care. Third, preoperative anemia was strongly associated with higher in-hospital mortality and adverse postoperative outcomes, including prolonged ICU stays.
The present study investigated the administration of RBC and PLT transfusions during ICU follow-up and their association with 30-day mortality. Patients who received RBC transfusions had a longer ICU stay compared to those who did not. However, this extended length of stay was likely attributable to the underlying anemia rather than the transfusions themselves.
In addition, there were three key findings reported in our present study. First, adult patients presenting for elective heart surgery at our center were highly likely to have preoperative anemia. The majority of patients in our sample met the WHO criteria for anemia, meaning their Hb level was greater than 50%. This high prevalence of preoperative anemia, which is far greater than previously documented in the literature, was an unexpected finding. The reason and duration of the preoperative anemia were not found, but our findings suggest that anemia and aging, the severity of comorbidities at the same time, and the complexity of the presenting non-cardiac surgical situation are closely related. Second, preoperative anemia was a significant and independent predictor of perioperative RBC transfusion. Among anemic patients, 94.5% demonstrated a three and a half-fold increase in the likelihood of requiring perioperative transfusion, even when the anemia was mild (Hb concentration ≥10 g/dL), which also resulted in higher financial costs. Third, preoperative anemia was strongly associated with increased in-hospital mortality and a higher incidence of postoperative adverse outcomes, including prolonged stays in the ICU.
Preoperative anemia in non-cardiac surgery represents a potentially treatable condition with important therapeutic implications. If postoperative adverse outcomes are indeed attributable to preoperative anemia, addressing low Hb levels prior to elective non-cardiac surgery could reduce mortality rates and decrease the duration of prolonged ICU stays.
The present study demonstrated that perioperative and postoperative mortality are influenced by multiple factors by assessing several key elements, including length of ICU stay, the requirement for and duration of mechanical ventilation, Hb levels, PLT counts and ASA scores, all of which showed significant associations with mortality. The observed associations may be related to anemia or to various mechanisms by which stored allogeneic erythrocytes disrupt homeostasis. Some of these mechanisms, such as impaired rheological properties, reduced oxygen delivery and the procoagulant effects of RBC-derived microparticles [7, 8, 9, 10, 11], manifest immediately. In contrast, other adverse effects, particularly those related to transfusion-associated immunomodulation (TRIM), develop over time [12]. Although the precise mechanisms underlying TRIM remain unclear, the modulation of cellular immunity is thought to play a key role [13].
The widened mortality gap between the transfusion and non-transfusion groups observed in this study supports the hypothesis that immunological factors likely contributed to the poorer outcomes in the transfusion group. Significant differences were also observed between these groups in terms of age distribution, ICU length of stay, Hb levels and PLT transfusion rates.
The results of the current research align with previous research investigating preoperative anemia as defined by the WHO [14, 15]. Several studies have associated anemia with an increased risk of postoperative complications [16, 17]. In the present analysis, the mortality risk was found to be 9.69 times higher in patients with preoperative Hb levels of 7.5 to 10 g/dL (95% CI: 2.80–33.59) and 2.22 times higher in those with preoperative Hb levels <7.5 g/dL (95% CI: 1.04–4.77) compared to patients with preoperative Hb levels >10 g/dL.
Blaudszun et al. [17] reported an inverse correlation between preoperative hematocrit levels and the risk of cardiac complications or death in patients undergoing non-cardiac surgery. Similarly, Mazer et al. [18] demonstrated an association between preoperative anemia and increased 30-day mortality (OR = 612, 95% CI: 573–654) as well as perioperative complications (OR = 330, 95% CI: 320–340) in non-cardiac surgical patients. Additionally, an analysis of cancer patients identified a relationship between anemia and an elevated risk of postoperative complications [16]. In the present study, univariate logistic regression analysis revealed that mechanical ventilation, ASA score, Hb level and PLT count were statistically significant predictors of 30-day mortality.
Several randomized controlled trials have evaluated the safety and potential benefits of a restrictive transfusion strategy in both cardiac and non-cardiac surgeries [19, 20, 21]. One study reported no superiority of a higher Hb threshold (Hb 10 g/dL) over a lower threshold (Hb 8 g/dL) in terms of survival and mobility at day 60 after hip surgery (OR = 1.01, 95% CI: 0.84–1.22) [18]. In the present study, univariate logistic regression analysis identified mechanical ventilation, ASA score, Hb level and PLT count as statistically significant predictors of mortality.
Three large randomized trials did not confirm the safety of a restrictive transfusion strategy (Hb threshold of 7.5–8 g/dL) compared to a liberal transfusion strategy (Hb threshold of 9–10 g/dL) in patients following cardiac surgery [19, 20, 22]. Conversely, evidence from vascular surgery suggests that transfusion at a higher Hb threshold (Hb 9 g/dL) improved cerebral oxygenation parameters and resulted in fewer complications compared to a lower threshold (Hb 8 g/dL) [23]. In the present study, 30-day mortality risk was found to be 13.36 times higher in patients with a preoperative Hb level of <7.5 g/dL compared to those with levels >10 g/dL (95% CI: 3.72–48.07, p < 0.001). Similarly, the 30-day mortality risk was 7.76 times higher in patients with a Hb level of <7.5 g/dL on the first day of the SICU compared to those with levels >10 g/dL (95% CI: 2.45–24.64, p < 0.001).
Reducing exposure to the identified mortality risk factors can potentially improve patient outcomes. Patients with elevated ASA scores should receive perioperative care specifically tailored to their physiological status and the surgical procedure. In the present study, the ASA score was identified as an independent risk factor for mortality, with the 30-day mortality risk being 53.17 times higher in patients with an ASA score above 2.
PLT transfusion has been identified as an independent risk factor for poor postoperative outcomes following cardiac surgery and liver transplantation [24, 25]. In the present study, a preoperative PLT value of <80 × 109/L was associated with a 30-day mortality risk 10.20 times higher than in patients with a PLT value >80 × 109/L (95% CI: 3.87–26.82). Similarly, on the first day of the surgical SICU, patients with a PLT value <80 × 109/L had a 10.68-fold higher risk of 30-day mortality compared to those with a PLT value >80 × 109/L (95% CI: 4.04–28.20). At discharge, patients with a PLT value <80 × 109/L showed a 15.36-fold increased mortality risk compared to those with a PLT value >80 × 109/L (95% CI: 6.30–37.45), with all these above findings showing statistical significance (p < 0.001).
In critically ill adult patients admitted to the ICU, the prevalence of hospital-acquired thrombocytopenia (HAT) ranges from 8.3% to 67.6%, with a prevalence of 14%–44% during ICU treatment [26, 27]. Recent data indicate that HAT is associated with an increased risk of bleeding, transfusion, ICU mortality, prolonged ICU stay and the need for organ support [28]. HAT frequently occurs following major surgeries, including hip replacement, abdominal surgery and cardiac procedures. Typically, PLT counts reach their lowest levels postoperatively between the first and fourth day, return to preoperative levels by the fifth to seventh day and peak around Day 14 due to tissue injury and blood loss [29]. While this clinical pattern appears brief, temporary and reversible, and often unrelated to the patient’s postoperative recovery, emerging evidence suggests it is not a benign process. For instance, a PLT count of <75 × 109/L after cardiac surgery has been associated with complications such as acute kidney injury (AKI), infection and stroke [25]. In the present study, a preoperative PLT count of <80 × 109/L was associated with a 30-day mortality risk 10.20 times higher than patients with a count >80 × 109/L (95% CI: 3.87–26.82). Similarly, on the first day in the surgical ICU (SICU), patients with a PLT count <80 × 109/L exhibited a 10.68-fold higher 30-day mortality risk compared to those with counts >80 × 109/L (95% CI: 4.04–28.20, p < 0.001).
6. Limitations
This study has several limitations that should be acknowledged. The primary limitation is the lack of detailed information on underlying medical conditions and surgical variables, such as whether surgery was performed and if transfusions were administered during surgery. These factors likely have a significant impact on transfusion decisions, especially in the ICU, where such considerations are pivotal. In addition, comorbidities were not comprehensively recorded, and their inclusion, along with more detailed factors and analyses, could have provided a deeper understanding of the findings. Moreover, the study is subject to biases inherent due to its retrospective, single-center design, which may limit the generalizability of the results. The study’s external validity is restricted, as it included only critically ill patients, which may not represent the broader surgical population. Furthermore, the observational design of the study prevents the establishment of definitive causal relationships between anemia, RBC transfusion and postoperative complications. The absence of detailed comorbidity data and surgical variables highlights the need for future studies to include these parameters to better understand their impact on transfusion practices and patient outcomes, and prospective, multicenter studies are necessary to validate these findings and explore the causal pathways underlying the observed associations.
7. Conclusions
This study demonstrates that the incidence of preoperative anemia reported here is among the highest documented in existing literature. The findings establish a clear relationship between anemia and transfusion, with transfusion-related anemia being associated with poorer postoperative outcomes in non-cardiac surgery. Anemia was identified as an independent predictor of adverse outcomes, with older patients (aged over 65 years) exhibiting reduced tolerance to anemia. While RBC transfusion appeared to worsen prognosis, this effect was not observed in cases of moderate-to-severe anemia. PLT transfusion was shown to significantly increase mortality risk, underscoring its role as an independent risk factor. The study highlights the need for further research to identify which patients benefit from PLT transfusions, the surgical procedures that demand higher PLT usage, and the associated risk factors. These insights are critical for developing targeted transfusion strategies to improve surgical outcomes. Future studies could aim to refine transfusion protocols to minimize risks and improve survival rates, and further evidence-based guidelines could enable clinicians to personalize transfusion practices based on patient-specific factors and surgical requirements, thereby enhancing perioperative care and reducing mortality risks.
Availability of data and materials
Not applicable.
Author contributions
SS—designed the research study; wrote the manuscript.. BT—performed the research. BS—analyzed the data. All authors read and approved the final manuscript. All authors critically revised the manuscript, agreed to be fully accountable for ensuring the integrity and accuracy of the work, and read and approved the final manuscript.
Ethics approval and consent to participate
This study was approved by the Ethics Committee of Medipol University Hospital (Ethics approval no: E-10840098-772.02-2981). Informed consent was waived by the Ethics Committee of Medipol University Hospital.
Acknowledgment
Not applicable.
Funding
This research received no external funding.
Conflict of interest
The authors declare no conflict of interest.
