Infections in the Intensive Care Unit: Posttransplant Infections

Delirium Among Adults Undergoing Solid Organ Transplantation

Purpose of Review

To summarize the research on post-operative delirium among patients undergoing solid organ transplantation in efforts to improve recognition, evaluation, and management, as well as highlight areas for future research.

Recent Findings

Delirium is a common complication in patients with organ failure before and after undergoing solid organ transplant (range: 4.7-47%). However, it is frequently unrecognized and underdiagnosed-even among those closely monitored after major surgery-given that its manifestation is often variable and inconsistent. Delirium has multifactorial etiologies comprising of a complex mix of predisposing recipient, donor, and transplant factors, as well as intraoperative and perioperative factors. Evidence suggests that delirium risk increases with presence of a greater number of such risk factors, and can lead to adverse outcomes such as increased hospital length of stay, time in the ICU, time on mechanical ventilators, graft dysfunction, graft loss, and mortality. Though no trials have been conducted among transplant populations specifically, delirium has been shown to be preventable among hospitalized older adults generally. Multicomponent, primary prevention strategies designed to target multiple risk factors of delirium, such as cognitive impairment, sleep deprivation, immobility, visual impairment, hearing impairment, and dehydration, have been identified as most effective. Whether these approaches translate to improvements in quality of life and long-term health outcomes among patients with organ failure before and after transplantation is yet to be determined.

Summary

Delirium is an important, common, yet potentially preventable complication among patients with organ failure. Future studies are needed to test the efficacy of multicomponent, primary prevention strategies on long-term health outcomes among these vulnerable populations.

Effect of Blood Product Resuscitation on the Pharmacokinetics of Ampicillin-Sulbactam during Orthotopic Liver Transplantation

Background: Ampicillin-sulbactam is a piperacillin-tazobactam-sparing alternative antibiotic administered as surgical prophylaxis during orthotopic liver transplant (OLT), but limited data are available describing its pharmacokinetics and impact of blood product resuscitation. The purpose of this study was to determine the intra-operative pharmacokinetics of ampicillin-sulbactam in patients during OLT and evaluate the effects of blood resuscitation on exposure. Patients and Methods: This was a pharmacokinetic study in 10 OLT patients receiving ampicillin-sulbactam surgical prophylaxis. A 5,000-patient Monte Carlo simulation was conducted to identify optimal ampicillin-sulbactam regimens. Linear regression assessed association between blood product administration and ampicillin exposures. Results: Ampicillin and sulbactam concentrations best fitted two-compartment models. Mean ampicillin pharmacokinetic parameters were central compartment volume (V_c): 6.9 ± 2.0 L, clearance (CL): 26.6 ± 18.4 L/h, and inter-compartmental rate constants (k₁₂ and k₂₁): 4.8 ± 2.6 and 2.3 ± 1.4 h^-1. Sulbactam pharmacokinetic parameters were V_c: 8.1 ± 2.7 L, CL: 26.1 ± 7.4 L/h, k₁₂ and k₂₁: 4.9 ± 1.0 and 2.8 ± 1.1 h^-1. Participants received between 500 and 23,642 mL of total blood product. No statistical relations were observed between blood product administration and exposures (R² 0.00-0.26). Ampicillin-sulbactam 2/1 g every two hours and 2/1 g bolus followed by 6/3 g continuous infusion provided acceptable probability of target attainment up to minimum inhibitory concentrations (MICs) of 16 and 32 mcg/mL, respectively. Conclusions: High and frequent ampicillin-sulbactam doses are required to maintain 100% fT > MIC at relevant MICs during OLT and no impact of blood product resuscitation was observed on ampicillin exposure. These are the first data available to guide ampicillin-sulbactam dosing in patients undergoing OLT.

Health Care-Associated Infection in Solid Organ Transplant Recipients

BACKGROUND

Health care-associated infection (HAI) represent a global health problem with an increase in hospital stays, deaths, and monetary costs. Recipients of solid organ transplants are a population at risk. The objectives of the study were to characterize the incidence of HAI in renal and hepatic transplant recipients as well as to compare them with the population without transplants in intensive care units (ICU).

METHODS

The data on the incidence of HAI, localization, microorganisms, and demographics were taken from the patients admitted between the years 2013 to 2018 (n = 4307) from the registration of the Project for the Reduction of Nosocomial Infection in Intensive Care Units. The variables were compared with those of renal transplant (n = 96) and liver transplants (n = 68) recipients.

RESULTS

Renal transplant recipients showed 26% incidence of HAI. The most frequent were surgical site infection (SSI), urinary tract infection, and primary bacteremia; the most frequent microorganism was Staphylococcus spp, mortality 3.8%. Liver transplant recipients showed 41% incidence of HAI. The most frequent were tracheobronchitis associated with mechanical ventilation, SSI, and primary bacteremia; the most frequent microorganism was Staphylococcus spp, mortality 37%. The population without transplants in the ICU showed 17% incidence of HAI. The most frequent were respiratory infections associated with mechanical ventilation, primary bacteremia, and SSI; the most frequent microorganism was Acinetobacter spp, mortality 21%.

CONCLUSIONS

HAI in recipients of solid organ transplants (renal and hepatic) have a higher incidence than in a population without transplants. The location and causal microorganisms have particularities that must be taken into account for the development of prevention protocols.

Co-infection with human polyomavirus BK enhances gene expression and replication of human adenovirus

Immunocompromised patients are susceptible to multiple viral infections. Relevant interactions between co-infecting viruses might result from viral regulatory genes which trans-activate or repress the expression of host cell genes as well as the genes of any co-infecting virus. The aim of the current study was to show that the replication of human adenovirus 5 is enhanced by co-infection with BK polyomavirus and is associated with increased expression of proteins including early region 4 open reading frame 1 and both the large tumor antigen and small tumor antigen. Clinical samples of whole blood and urine from 156 hematopoietic stem cell transplant recipients were tested. We also inoculated adenocarcinomic human alveolar basal epithelial cells with both human adenovirus 5 and BK polyomavirus to evaluate if co-infection of viruses affected their replication. Data showed that adenovirus load was significantly higher in the plasma (mean 7.5 x 10³ ± 8.5 x 10² copies/ml) and urine (mean 1.9 x 10³ ± 8.0 x 10² copies/ml) of samples from patients with co-infections, in comparison to samples from patients with isolated adenovirus infection. In vitro co-infection led to an increased (8.6 times) expression of the adenovirus early region 4 open reading frame gene 48 hours post-inoculation. The expression of the early region 4 open reading frame gene positively correlated with the expression of BK polyomavirus large tumor antigen (r = 0.90, p < 0.0001) and small tumor antigen (r = 0.83, p < 0.001) genes. The enhanced expression of the early region 4 open reading frame gene due to co-infection with BK polyomavirus was associated with enhanced adenovirus, but not BK polyomavirus, replication. The current study provides evidence that co-infection of adenovirus and BK polyomavirus contributes to enhanced adenovirus replication. Data obtained from this study may have significant importance in the clinical setting.