Allogeneic blood transfusion and postoperative duration of mechanical ventilation: effects of red cell supernatant, platelet supernatant, plasma components and total transfused fluid.

BACKGROUND AND OBJECTIVES: In patients undergoing open-heart surgery, allogeneic blood transfusion (ABT) may be related to an enhanced inflammatory response and impaired pulmonary function, resulting in a need for prolonged mechanical ventilation. Transfused red blood cell (RBC) supernatant, platelet supernatant or plasma components, may exercise varying effects on pulmonary function, because these fluids differ in their content of soluble biological-response modifiers. MATERIALS AND METHODS: The records of 416 patients undergoing coronary artery bypass graft operations at the Massachusetts General Hospital were reviewed. Possible predictors and the number of days of postoperative ventilation, as well as the number of all transfused blood components, were recorded. The association between mechanical ventilation past the day of operation and the volume of transfused RBC supernatant, platelet supernatant, or plasma components, was calculated by logistic regression analyses. RESULTS: The volume of each transfused fluid differed (P < 0.0001) among patients ventilated for 0, 1, 2, 3, or > or = 4 days after the day of the operation. After adjusting for the effects of confounding factors, the volume of administered RBC supernatant was associated (P = 0.0312) with the likelihood of postoperative ventilation past the day of operation, but the volume of platelet supernatant, plasma components, or total transfused fluid was not (P = 0.1528, P = 0.1847, and P = 0.0504, respectively). CONCLUSIONS: These results are congruent with the hypotheses that ABT may impair postoperative pulmonary function and that any such adverse effect of ABT is probably mediated by the supernatant fluid of stored RBCs. Both hypotheses should be examined further, in future studies of the outcomes of ABT.

Allogeneic blood transfusion and postoperative duration of mechanical ventilation.

BACKGROUND: In patients having open heart surgery, allogeneic blood transfusion (ABT) may be related to an enhanced inflammatory response and impaired pulmonary function, resulting in the need for prolonged mechanical ventilation. STUDY DESIGN AND METHODS: The records of 416 consecutive patients undergoing coronary artery bypass graft surgery at Massachusetts General Hospital were reviewed. Possible predictors and the number of days of postoperative ventilation, as well as the number of RBC units transfused and the length of their storage, were recorded. The association between mechanical ventilation after the day of operation and the number of RBC units transfused was calculated by logistic regression analysis. RESULTS: The number of RBC units transfused, but not the length of their storage, differed (p<0.0001) among patients ventilated for 0, 1, 2, 3, or 4 or more days after the day of operation. Patients taken off ventilation on the day of operation received (mean +/- SE) 2.01 +/- 0.14 RBC units; patients kept on ventilation for 4 or more days received 9.45 +/- 1.83 units. After adjusting for the effects of 18 confounding factors, the number of RBC units transfused was not a significant predictor of ventilation past the day of operation. There was, however, a trend suggesting that the likelihood of such ventilation might increase by 26 percent per RBC unit transfused (p = 0.0628). CONCLUSIONS: Future studies of the outcomes of ABT should examine further the possibility of a relationship between the number of transfused RBCs and the likelihood of postoperative ventilation after the day of operation.

RBC transfusion and postoperative length of stay in the hospital or the intensive care unit among patients undergoing coronary artery bypass graft surgery: the effects of confounding factors.

BACKGROUND: Data on the independent association between perioperative allogeneic blood transfusion (ABT) and postoperative length of stay at the hospital or in the intensive care unit (ICU) are sparse. STUDY DESIGN AND METHODS: The records of 421 consecutive patients undergoing coronary artery bypass graft (CABG) operations at the Massachusetts General Hospital were reviewed. The effect of perioperative ABT in explaining the variation in the postoperative length of stay (LOS) at the hospital or in the ICU was calculated after adjustment for the effects of 20 confounding factors that pertained to severity of illness, difficulty of operation, and risk of postoperative wound infection or pneumonia. RESULTS: Postoperative LOS averaged (mean +/- SE) 8.0 +/- 0.3 days in the hospital and 50.0 +/- 4.1 hours in the ICU. After adjustment for the effects of confounding factors, the postoperative length of hospitalization increased by 0.837 percent (95% CI, 0.249-1.425%) per RBC unit transfused (p<0.001), and the postoperative length of stay in the ICU increased by 0.873 percent (95% CI, -0.068-1.814%) per RBC unit transfused (p<0.10). CONCLUSION: Allogeneic blood transfusion was independently associated with longer postoperative stays in the hospital or the ICU, but the observed independent association is perhaps too small to be clinically relevant. This independent association may be due to a relationship between ABT and a higher incidence of septic complications of surgery, or it may reflect the function of blood transfusion as a surrogate marker for severity of illness.

Length of storage of transfused red cells and postoperative morbidity in patients undergoing coronary artery bypass graft surgery.

BACKGROUND: The transfusion of old red cells (RBCs) may be associated with reduced delivery of oxygen to tissues and an increased risk of transfusion complications. The association of postoperative morbidity with the length of storage of perioperatively transfused RBCs was studied in 268 consecutive patients receiving a blood transfusion for coronary artery bypass graft surgery. STUDY DESIGN AND METHODS: The postoperative length of hospitalization, the postoperative length of stay in the intensive care unit, and the length of endotracheal intubation after the day of the operation were used as surrogate measures of global postoperative morbidity. The length of storage of the oldest transfused RBC unit, the mean length of storage of the oldest and second oldest RBC units, and the mean length of storage of all RBC units transfused to each patient were tested for association with the three outcome variables. Multiple linear regression analysis and Cox proportional-hazard analysis were used to adjust for the effects of confounding factors that pertained to each patient's severity of illness and the difficulty of each operation. RESULTS: There were no significant associations after adjustment for the effects of confounding factors. CONCLUSION: This study did not corroborate the previously reported association between transfusion of old RBCs and increased morbidity. However, there is surprisingly little research on the clinical outcomes of the transfusions of old RBCs, and this hypothesis should be investigated further.

Transfusion and postoperative pneumonia in coronary artery bypass graft surgery: effect of the length of storage of transfused red cells.

BACKGROUND: Various bioactive substances are released from white cell (WBC) granules into red cell (RBC) components in a time-dependent manner during blood storage. Some of these substances may have immunosuppressive effects and may contribute to transfusion-induced immunomodulation. RBCs transfused after prolonged storage may be associated with a higher incidence of postoperative infections than fresh RBCs. This hypothesis does not seem to have been investigated in a clinical study. STUDY DESIGN AND METHODS: The records of 416 consecutive patients undergoing coronary artery bypass graft operations at the Massachusetts General Hospital were reviewed. The association between the length of storage of the transfused RBCs, as well as the number of units of non-WBC-reduced allogeneic RBCs and/or platelets transfused, and the occurrence of postoperative pneumonia was calculated by logistic regression analyses adjusting for the effects of confounding factors. Among these were the numbers of days of intubation, days of impaired consciousness, and units of RBCs transfused. RESULTS: By Centers for Disease Control and Prevention criteria, pneumonia developed in 54 patients (13.0%). Among 269 patients given RBCs, the risk of pneumonia increased by 1 percent per day of increase in the mean storage time of the transfused RBCs (p<0.005). In an analysis of all patients, the risk of pneumonia increased by 5 percent per unit of non-WBC-reduced allogeneic RBCs and/or platelets received (p = 0.0584). CONCLUSION: After adjustment for the effects of the risk factors for pneumonia and the number of transfused RBCs, an association was observed between the length of storage of transfused RBCs and the development of postoperative pneumonia. This association should be investigated further in future studies of the outcomes of blood transfusion.

Transfusion of white-cell containing allogeneic blood components and postoperative wound infection: effect of confounding factors.

Randomized controlled trials (RCTs) of the relationship between allogeneic transfusion and post-operative bacterial infection at any site have generated discordant results, but have suggested an association of transfusion with wound infection. To examine the specific association of perioperative transfusion with wound infection, we reviewed the records of 964 consecutive patients undergoing elective colorectal cancer resection at our hospital. Diagnoses of wound infection were made retrospectively by the Centers for Disease Control criteria, and transfusion was defined as number of units of white-cell containing allogeneic blood components received. The probability of wound infection in association with the transfusion was calculated following adjustment for the effects of 12 confounders that had not been previously considered in combination. These factors related to severity of illness, difficulty of operation and risk of wound infection. Wound infection developed in 39 (11.4%) transfused patients, as compared to 24 (3.9%) untransfused subjects (P < 0.0001). In the multivariate analysis, there was a trend suggesting an adverse transfusion effect, which amounted to a 7% increase in the risk of wound infection per unit of red cells or platelets transfused (relative risk [RR] = 1.07; 95% confidence interval for RR = 0.98-1.16; P = 0.1241). This marginally significant effect was related to post-operative (P = 0.1274), rather than perioperative (P = 0.3061), transfusion. We conclude that allogeneic transfusion may perhaps be associated with a small increase in the risk of post-operative wound infection, but this small effect can be established only by RCTs enrolling several thousand patients. The modest magnitude of the effect may have been responsible for the disagreements among the published RCTs.

Allogeneic blood transfusion, hospital charges, and length of hospitalization: a study of 487 consecutive patients undergoing colorectal cancer resection.

OBJECTIVE: To investigate the independent association of allogeneic blood transfusion with longer hospital stays and higher hospital charges, after adjustment for the effects of confounding factors that are related to both these outcomes and the receipt of a perioperative transfusion. DESIGN AND METHODS: The records of 487 consecutive patients undergoing colorectal cancer resection and assigned a diagnosis-related group code between 146 and 149 were reviewed. The influence of allogeneic transfusion in explaining the variation in the observed length of stay and total hospital charges was calculated after adjustment for the effects of 20 confounding factors that related to severity of illness, difficulty of operation, and risk of postoperative infection. RESULTS: Length of stay (mean +/- SE) was 16.7 +/- 0.81 days in the transfused group, compared with 10.3 +/- 0.26 days in the untransfused group (P < .0001); hospital charges were $28101 +/- 1121 and $15978 +/- 265, respectively (P < .0001). After adjustment for the effects of 20 confounding factors, length of stay increased by 1.3% (95% confidence interval 0.5% to 2.1%) per unit of red blood cells and/or platelets transfused (P < .001), and hospital charges increased by 2.0% (95% confidence interval, 1.4% to 2.6%) per unit (P < .001). CONCLUSION: Allogeneic transfusion was independently associated with longer hospital stays and higher hospital charges. This association may be due to a relationship between allogeneic transfusion and a higher incidence of septic complications of surgery or may reflect the function of blood transfusion as a surrogate marker for severity of illness.

Blood transfusion and infection after colorectal cancer surgery.

BACKGROUND: Many observational studies have described an association between perioperative transfusion and postoperative infection. Detection of such a relationship may depend on which variables are considered as potential confounders of the association under study. However, most reports have not considered risk factors for postoperative infection at specific sites as possible explanations for the observed relationship. STUDY DESIGN AND METHODS: The records of 492 patients undergoing elective colorectal cancer resection at the Massachusetts General Hospital between January 1992 and December 1994 were reviewed. The probability of infection in association with transfusion was calculated with and without adjustment for the effects of chronic systemic illness, number of days with urinary catheter, endotracheal intubation, impaired consciousness, and specific risk factors for wound infection. Postoperative infection at any site and infections at specific sites were analyzed as separate outcomes. RESULTS: After adjustment for the effects of the variables listed above, allogeneic transfusion was not associated with postoperative infection at any site (p = 0.407). Only a specific association of transfusion with wound infection could be detected. However, in an analysis that adjusted for the effects of only the 18 confounders considered by previous authors, transfusion was the most significant predictor of infection. In that analysis, the risk of postoperative infection increased by 14 percent per unit of red cells transfused (p < 0.001). CONCLUSION: The overall adverse relationship between transfusion and infection reported by previous observational studies may have been due to an incomplete consideration of the variables that confound that association. This finding may help explain the disagreement between the conclusions of recent large, randomized, controlled trials (which failed to detect a deleterious transfusion effect) and the earlier observational studies.