Infectious problems after elective surgery of the alimentary tract: the influence of peri-operative factors. The Norwegian Gastro-Intestinal Group (NORGAS)

Blood transfusion and the risk for infections in kidney transplant patients

BACKGROUND

Receipt of a red blood cell transfusion (RBCT) post-kidney transplantation may alter immunity which could predispose to subsequent infection.

METHODS

We carried out a single-center, retrospective cohort study of 1,258 adult kidney transplant recipients from 2002 to 2018 (mean age 52, 64% male). The receipt of RBCT post-transplant (468 participants transfused, total 2,373 RBCT) was analyzed as a time-varying, cumulative exposure. Adjusted cox proportional hazards models were used to calculate hazard ratios (HR) for outcomes of bacterial or viral (BK or CMV) infection.

RESULTS

Over a median follow-up of 3.8 years, bacterial infection occurred in 34% of participants at a median of 409 days post-transplant and viral infection occurred in 25% at a median of 154 days post-transplant. Transfusion was associated with a step-wise higher risk of bacterial infection (HR 1.35, 95%CI 0.95-1.91; HR 1.29, 95%CI 0.92-1.82; HR 2.63, 95%CI 1.94-3.56; HR 3.38, 95%CI 2.30-4.95, for 1, 2, 3-5 and >5 RBCT respectively), but not viral infection. These findings were consistent in multiple additional analyses, including accounting for reverse causality.

CONCLUSION

Blood transfusion after kidney transplant is associated with a higher risk for bacterial infection, emphasizing the need to use transfusions judiciously in this population already at risk for infections.

The Immunosuppressive Aspects of Blood Transfusion

Blood transfusion is associated with immunosuppression, although the exact etiology of the immunosuppressive effect is not fully understood. The clinical significance of the immunosuppressive effect of blood transfusion has been examined in three situations: (1) studies of renal allograft survival after renal transplantation, (2) outcome studies in patients who have had surgical resection of solid cancer tumors, and (3) studies of infection rates in postoperative patients. In each scenario, the data support the conclusion that transfusion is associated with immunosuppression as manifested by increased renal allograft survival, increased recurrence and mortality rates in patients with cancer, and increased infection rates in postoperative patients who are transfused. Not all studies demonstrate an immunosuppressive effect of transfusion. There are several possible explanations for these discrepancies. First, prognostic variables other than transfusion itself account for the outcome results in these retrospective studies. Second, the extent of immunosuppression may be influenced by the type of blood product transfused, the amount transfused, and the timing of the transfusion; these factors have not been considered in all studies. For example, whole blood has been implicated as having a greater immunosuppressive effect than packed red blood cells, and many studies have shown that more than three units of packed red blood cells are necessary to affect outcome. Controlled animal studies have tested the hypothesis that transfusions increase solid tumor growth or the risk for infection. These studies have yielded conflicting results. Nevertheless, evidence that blood transfusion influences clinical outcome mitigates that a decision to transfuse must consider both risks and benefits of a transfusion; the possible consequences of immunosuppression must be included among the risks. Use of autologous blood, erythropoietin, and, in the future, synthetic hemoglobin may lead to improved outcome in patients with certain disease processes.

Infectious problems in elective surgery of the alimentary tract: the influence of pre-operative factors. The Norwegian Gastro-Intestinal Group (NORGAS)

The influence of some pre-operative factors on infectious complications after elective abdominal surgery was investigated in a prospective multi-centre study of 1537 patients in surgical departments regularly using a standardized prophylactic antibiotic regimen. A total of 1101 patients received 1600 mg tinidazole plus 400 mg doxycycline intravenously 1-hour pre-operatively. Analysis of the results showed that increasing age, malignancy, risk factors noted by the surgeon before the surgical procedure, and discrepancies between assumed disease and peri-operative findings were associated with significantly more post-operative complications, but not more infectious complications related to peri-operative contamination. Pre-operative hospital stay did not influence the infection rate provided that prophylaxis was given.