'Hypothesis-generating' study to assess whether the presence of a central venous line significantly affects the volumes of fluid infused perioperatively in major elective colorectal surgery

There are several indications for elective central venous cannulation in major colorectal surgery, particularly in those at a higher risk of morbidity and mortality. These include: the ability to infuse certain vasoactive medications, monitor central venous pressure, allow for frequent blood sampling, and provide a route of access for total parenteral nutrition(1). Furthermore, there has been a great deal of recent interest in whether there are improved outcomes with restrictive as opposed to liberal fluid therapy in major abdominal surgery(2), and, similarly, with individualised, rather than generic, blood pressure management in major surgery(3). However, there have been no major studies to date examining whether the simple act of electively inserting a central venous catheter prior to the start of surgery influences the volume of fluid infused and the use of vasopressors perioperatively.

The RELIEF trial reported that modestly liberal perioperative fluid regimens conferred no greater disability-free survival benefit over restrictive regimens, but are likely to reduce rates of acute kidney injury(2). This contrasts with the restrictive protocols championed by various Enhanced Recovery After Surgery (ERAS) programs(4). Previous works have suggested that not only does adherence to ERAS principles lead to superior patient outcomes, but some have gone further in identifying restriction of intravenous fluids perioperatively to be one of the few interventions that independently predicts a better outcome(5). One of the advantages of central venous catheterisation is the ability to administer drugs in smaller volumes of fluid. Therefore, given the intensity of the debate surrounding restrictive and liberal regimens, it should be investigated whether the availability of central venous access impacts upon the volumes of fluid infused.

Furthermore, central venous catheterisation is unlikely just to have an impact via the avoidance of inadvertent larger volume infusion, which is sometimes seen with drug administration through a peripheral line. The RELIEF trial reported that the patient cohort managed with a restrictive fluid regimen were more likely to receive vasopressor support, compared with those receiving a liberal regimen(2). The presence of a central venous catheter enables the use of potent vasopressor agents, such as noradrenaline, which will further influence fluid administration, by introducing a second therapeutic option for correcting perioperative hypotension. The importance of 'tight' blood pressure control has been demonstrated by the INPRESS trial, which showed a reduction in post-operative organ dysfunction with individualised blood pressure management, over standard management strategies(3). This is of particular importance, as evidence has shown that cardiac output-directed fluid therapy should not lead to 'excessive fluid administration, but may lead to a more individualised approach to achieving the correct dose of fluid'(6), and may require concomitant use of vasoactive agents.

Thus, the investigators have set out to investigate whether the elective insertion of a central venous catheter prior to the start of major colorectal surgery, influences the volumes, and types, of fluid infused, as well as the use and mean dose of vasopressor agents, intra-operatively and for the first 12 hours post-operatively.

1. Smith, RN, et al., 'Central venous catheters', BMJ 2013; 347:f6570
2. Myles, PS, et al., 'Restrictive versus Liberal Fluid Therapy for Major Abdominal Surgery', N Engl J Med 2018; 378:24
3. Futier, E, et al., 'Effect of Individualised vs Standard Blood Pressure Management Strategies on Postoperative Organ Dysfunction Among High-Risk Patients Undergoing Major Surgery', JAMA 2017; 318(14):1346
4. Feldheiser, A, et al., 'Enhanced Recovery After Surgery (ERAS) for gastrointestinal surgery, part 2: consensus statement for anaesthesia practice', Acta Anaesthesiologica Scandinavia 2016, 60:289
5. Gustafsson, UO, et al., 'Adherence to the Enhanced Recovery After Surgery Protocol and Outcomes After Colorectal Cancer Surgery', Arch Surg 2011; 146(5):571
6. Pearse, RM, et al., 'Effect of a Perioperative Cardiac Output- Guided Haemodynamic Therapy Algorithm on Outcomes Following Major Gastrointestinal Surgery', JAMA 2014; 311(21):2181

Inclusion Criteria:

The inclusion criteria will be all adult patients presenting for elective major colorectal surgery (resection), whom are to be electively admitted to critical care directly from theatre.

Exclusion Criteria:

• Patients under 18 years of age
• Patients undergoing emergency surgery
• Those not admitted electively to critical care directly from theatre
• Those patients that do not undergo any bowel resection
• Patients in whom central venous catheter insertion is as an emergency peri- operatively
• Patients refusing/unable to give valid informed consent

Adult patients, undergoing elective major colorectal resection, at a district general hospital in east London, UK.

At this stage there is no plan to make IPD available, and certainly no such intention has been discussed with the relevant ethical and review boards (HREC/HRA).