Cytomegalovirus Control in Critical Care

Background:

• Cytomegalovirus (CMV) is a common virus which infects around half the UK population. Infection is usually mild, but after infection the virus is never completely eradicated, and may reactivate in ill health. Reactivation is most commonly seen in those with compromised immune systems, such as people with advanced HIV infection, or whilst on immunosuppression following organ transplantation. CMV reactivation in these patients can be life threatening. There is evidence to support the use of antiviral medication in these groups of immunosuppressed patients to prevent CMV reactivation, and their use is part of standard therapy. There is increasing evidence demonstrating that a third of critically ill patients will reactivate CMV, and these patients have as much as a doubled mortality.

Aims:

• This study is a proof of concept study designed to assess whether antiviral prophylaxis can effectively and safely suppress CMV reactivation in CMV seropositive high risk critically ill patients. Antiviral prophylaxis is currently not standard practice in critical care units, and no previous trials of prophylaxis have been undertaken in this setting. All commonly used antiviral agents have side effects, and it is important to demonstrate their efficacy and safety in the critical care setting before undertaking a large multicentre trial powered to identify mortality or morbidity differences with prophylaxis. Intravenous ganciclovir, and its oral prodrug valganciclovir have been effectively used as prophylaxis at low doses in immunosuppressed patients. Intravenous aciclovir and its oral prodrug valaciclovir in high dosage have also been demonstrated to be effective as prophylaxis in immunosuppressed patients. This study sets out to determine whether their use in critically ill patients are both effective and safe.

Plan of Investigation:

• This is a prospective, randomised, open-label single centre study. Patients admitted to the Queen Elizabeth Hospital Birmingham critical care unit, and identified by study criteria to be at high risk of CMV reactivation will be assessed for inclusion into the study. Blood will be analysed for CMV antibodies to establish eligibility. Recruited patients will be randomised to receive high dose aciclovir/valaciclovir, or low dose ganciclovir/valganciclovir for the duration of their critical care stay, for a maximum of 28 days, or to enter the control group receiving standard care. CMV viral load by polymerase chain reaction (PCR) will be measured in blood, throat swab, urine, and sputum via non-directed bronchiolar lavage (NDBL) twice weekly.

Potential Impact:

• Latent CMV infection is common, affecting around half of all adults in the UK. Evidence demonstrates that a third of these patients will reactivate leading to CMV viraemia when critically ill. Epidemiological data from multiple independent groups have identified a doubling in mortality in this group, although a causal link between CMV reactivation and mortality without a trial of antiviral drugs can not be assumed. From these figures, it is estimated that 16.5% of critically ill patients (current mortality rates of around 40%) may benefit from antiviral prophylaxis. Almost no patients are receiving prophylaxis or screening for reactivation worldwide in this group. Demonstration of mortality or morbidity improvements could potentially change worldwide intensive care practice.