Key points
Outpatient parenteral antimicrobial therapy (OPAT) is an increasingly utilised, safe and effective model of care in the UK, endorsed by the Department of Health as a key antimicrobial prescribing decision within an antimicrobial stewardship programme
National and international guidelines and clinical governance standards have been published to support quality assurance in OPAT services
Several models of OPAT organisation and delivery are in use with adaptability to local circumstances
Skin and soft tissue, and bone and joint infections account for a large proportion of OPAT episodes, but a wide variety of infections including endocarditis can be treated in OPAT safely and effectively
Novel antimicrobials with long half-life are useful in OPAT and can allow convenient management of drug resistant microbes
Introduction
Outpatient parenteral antimicrobial therapy (OPAT) refers to outpatient or community-based management of an infection via the administration of an intravenous (IV) antimicrobial without an overnight hospital stay. Patients may be managed without admission or may transition to OPAT following hospitalisation. By minimising hospital stay, OPAT is increasingly recognised as a cost-efficient and acceptable management strategy for a variety of selected patients requiring either short- or medium-to long-term parenteral therapy in the UK (Table 1).1–5 This short article outlines good practice recommendations and highlights OPAT management of infections commonly encountered by physicians with acute medical duties.
Characteristics of recently published UK OPAT service cohorts.
How does OPAT normally work in the UK?
The precise structure and function of OPAT differ between services and are adaptable to local requirements. It is recommended that the core OPAT team includes a consultant clinician, a medically qualified infection specialist (for example an internal medicine specialist and a clinical microbiologist, or an infectious diseases physician holding both roles), a clinical pharmacist with antimicrobial interest and an OPAT nurse specialist with intravascular access expertise. Delivery of antimicrobials may occur in an OPAT clinic area (which will require patient transport to and from the clinic) or in the home (with the patient or carer trained to administer IV treatment or with visits from OPAT staff or community nurses). Increasingly, some aspects of OPAT (such as the management of cellulitis) are delivered in the context of an acute-medicine-led ‘hospital at home’ service, which may encompass other lower-risk acute medical conditions, such as selected venous thrombo-embolism, chronic obstructive pulmonary disease (COPD) exacerbation and chronic cardiac failure. Selection of patients with infection who are suitable for ambulatory care is essential. Substantive considerations include infection severity, patient mobility, stability of co-morbidity and the need for ancillary management and understanding of care.
Good clinical practice recommendations for OPAT
OPAT guidelines have been produced in a number of countries and updated good clinical practice (GCP) recommendations were published for the UK in 2012, covering five key components of OPAT services (Table 2).6
Summary of good clinical practice recommendations for OPAT in UK.6
Specific conditions pertinent to medical specialties and acute medicine
Skin and soft tissue infections
Cellulitis and erysipelas alone account for about 70,000 admissions to hospital in England annually.7 A large point prevalence survey of inpatient antibiotic use in Scotland found that 10% of hospitalised patients were receiving IV antibiotics, one in six of whom were being treated for skin and soft tissue infection (SSTI).8 Randomised control trial (RCT) data suggest about one-third of patients with an SSTI requiring IV antimicrobial therapy could be managed as outpatients, with equivalent clinical outcomes and higher patient satisfaction.9
Complicated and drug-resistant SSTI cases can also potentially be treated through OPAT. This has been facilitated in recent years by novel broad-spectrum antimicrobial agents with expedient pharmacokinetic properties allowing once daily dosing. In a phase III RCT establishing ertapenem for complicated SSTI treatment, 40% of patients were managed in whole or in part as outpatients.10 Similarly, in a retrospective analysis of data from the Cubicin® outcomes registry, 276 of 435 (63%) patients treated for SSTI with daptomycin received OPAT, with a 95.5% success rate in those with complicated SSTI.11
UK OPAT services now have extensive experience of SSTI management and are responsible for a number of service innovations. Based on population pharmacokinetic modelling of patients treated through OPAT, teicoplanin dosing guidelines have been developed which provide effective and convenient individualised three-times-weekly regimens, which are useful for selected SSTIs treated in OPAT.12 Specialist nurse-led outpatient management of SSTIs, including parenteral antimicrobial prescribing under a ‘patient group direction’ (PGD) protocol, may be associated with shorter duration of therapy for moderately severe cellulitis.13
Even with careful patient selection based on severity classification, failures of OPAT in SSTI are seen. In a cohort of 963 OPAT-treated SSTI cases in Glasgow, progression of infection occurred in 2.8% of patients. 6% required admission to hospital from OPAT and significant adverse events (predominantly drug reactions) were observed in 7.1%.14 This emphasises the need for accessible and well-defined pathways for prompt review and escalation of care for OPAT services managing SSTIs.
Infective endocarditis
While OPAT is being used to avoid hospital admission for SSTI, it is also of use in supporting early discharge of patients with conditions requiring more prolonged parenteral antimicrobial therapy. This use is well exemplified by the increasing practice of completing endocarditis treatment through OPAT following initial inpatient stabilisation. In contrast to SSTI, no RCT data exist for OPAT management of endocarditis. International OPAT guidelines for endocarditis recommend stringent patient selection criteria. Contraindications to outpatient therapy include the presence of a prosthetic valve, persistently positive blood cultures, congestive cardiac failure, vegetations greater than 10 mm in length, recurrent embolic events, conduction abnormalities and Staphylococcus aureus aetiology.15 It is, however, clear from more recent cohort reports that OPAT services are successfully treating S aureus and prosthetic valve endocarditis,16–18 and recent European Society of Cardiology recommendations do not explicitly preclude this practice (Table 3).19 It remains standard practice to initially manage endocarditis with a minimum inpatient stay of 2 weeks prior to OPAT, with the possible exception of clinically stable patients with ‘oral’ streptococcal infection. Careful follow up during OPAT and consideration of adverse drug reactions, disease progression and complications is essential.
European Society of Cardiology recommendations on suitability of patients for OPAT treatment of endocarditis 2009.19
Bone and joint infection
The general physician will encounter bone and joint infections most commonly in the context of diabetic foot or vertebral osteomyelitis/discitis and native joint septic arthritis. Typically, such infections require a combined surgical and medical management approach, including prolonged antibiotic therapy with a significant proportion of IV therapy. The majority of such infections may be managed for a proportion of their therapy via OPAT, although the elderly, those with resistant organisms or diabetic foot disease have a greater chance of a complicated OPAT course (disease complications, drug reactions or readmission), and therefore should be carefully selected and monitored.20
Other infections
A multitude of other infections may be amenable to OPAT therapy, including bacterial meningitis (following initial inpatient management), drug resistant mycobacterial infection, complex Lyme infection21 and some imported parasitic infections.22 In particular, Gram-negative infections and extended spectrum beta-lactamase (ESBL) infections are increasingly managed via OPAT.1 These are usually in the context of a urinary tract infection (UTI)23 that is not amenable to oral therapy and reflect epidemiological change in the hospital population.
Complications of OPAT
Parenteral treatment outside an inpatient environment potentially exposes patients to a different risk profile. As with any model of healthcare delivery, complications can be anticipated and ameliorated.24 It is recommended that OPAT services systematically record adverse outcomes for quality assurance purposes.6 Many (but not all) OPAT models make use of indwelling intravascular access devices (Table 1). These are associated with line infections (at a rate of 0–3 per 1,000 OPAT patient days in published cohorts), while other line events, such as thrombosis and mechanical and chemical phlebitis, occur at higher rates (0.5–5 per 100 OPAT patient days).3,25–27 This underlines the need for specialist nursing involvement with intravascular device expertise in OPAT. Rates of healthcare associated infection (HAI) are lower than in hospitalised patients. For example, Clostridium difficile-associated disease (CDAD) is rare in OPAT patients, with rates of less than 0.5% per OPAT patient episode in UK cohorts reporting on CDAD.1–4 Overall rates of unplanned readmission from OPAT range from 6% to 12%.1–4 Appropriate and well supported self-administration of OPAT by patients or carers at home has not been associated with increased rates of complications.4,25
Antimicrobial stewardship and OPAT
Antimicrobial stewardship is a locally based programme to ensure safe, effective and prudent use of antimicrobials in order to optimise outcome and minimise unintended consequences such as CDAD, methicillin-resistant Staphylococcus aureus (MRSA) infection and drug-related toxicity. Following the decision to prescribe an antimicrobial, OPAT has been identified as one of the five key prescribing decisions by the Department of Health in England,28 highlighting the importance of early identification of patients who could be safely and effectively managed in a non-hospital setting. Within the OPAT programme, antimicrobial stewardship principles are similarly important, minimising unnecessarily prolonged IV therapy, promoting early switching from IV to oral treatment and, whenever possible, simplification of antimicrobials to the narrowest spectrum possible.6 It is therefore essential that every patient undergoing OPAT has an antibiotic plan and that the plan is reviewed regularly and adapted as circumstances evolve. The development of a patient group direction in skin and soft tissue infection, giving clinical nurse specialists the facility to implement a timely IV-to-oral switch without the need for medical review, has been associated with progressive reductions in the duration of IV therapy.13,14 While IV therapy is regarded as a standard of care in the management of many deep-seated infections, the relative efficacy of IV vs oral antibiotic therapy in bone and joint infections is unknown. An Oxford-initiated UK multicentre randomised study of IV vs oral treatment is currently underway and may better define the role of OPAT in this important patient group.
Acknowledgements
The Glasgow OPAT team: Lindsay Semple, Fiona Robb, Claire Vallance and Deepa Matthew.
- © 2013 Royal College of Physicians
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