But These Data Don't Apply to Me
Can we claim that US perioperative clinical practice differs too much from ours for the headline observations from this study to be relevant to European practice? The model of anaesthesia care is somewhat different; in these hospitals, a licenced 'attending' anaesthesiologist supervises anaesthesia provision by either a certified registered nurse anaesthestist ('CRNA'; who comprised just under half of the in-room providers in this study) or medically trained residents (the remainder). No patients who received fluid therapy from a student registered nurse anaesthestist were included, on the basis that only one of the two institutions had them. In the UK, intraoperative cardiac output monitoring to guide stroke volume optimization during many elective major surgeries is recommended by the National Institute for Health and Care Excellence (NICE) and advocated as a means to achieve bespoke fluid therapy for the individual, but this has gained little traction in America as yet. The authors of this paper specifically mention that goal-directed fluid therapy was not practised. Also omitted is information about perioperative vasoactive drug use. Vasopressors may be used as part of 'balanced' haemodynamic therapy during surgery and are likely to have an impact on the fluid volumes used.
But there are broad similarities between the health-care models in the two continents. With the advent of the 'perioperative surgical home' in the USA, elective surgical services increasingly resemble Europe's enhanced recovery. If anything, outcomes from leading US hospitals are often better than ours for similar procedures.
Is the variability unique to the two institutions in this study? No! Registry data for a period of 5 yr from more than half a million patients having colonic or arthroplasty surgery confined to nine ICD-9 procedure codes across 524 US hospitals shows that fluid usage complies to a U-shaped curve, with a median of around 3 litres crystalloid per procedure; however, the interquartile range of intraoperative fluid administration ranges from 1.3 to 5.0 litres, and varies by institution. A quarter of colonic surgery patients received >5 litres on the day of surgery and 11 litres postoperatively.
In the UK, it is likely that there is similar variability in 'standard care' across providers and institutions. This is certainly apparent in UK perioperative fluid therapy studies. Recommended control group baseline fluid regimens in recent prominent trials have ranged from dextrose water 5% (1 ml kg h) to isotonic crystalloid (10 ml kg h). Consensus guidelines from England's Enhanced Recovery Partnership Programme recommend that maintenance fluid during surgery should be limited to <2 ml kg h, with further fluid challenges guided by stroke volume monitoring; several state-of-the-art recent fluid therapy studies have used no baseline crystalloid at all. It seems unlikely that both ends of this spectrum of current common clinical practice are correct (Fig. 1).
(Enlarge Image)
Figure 1.
Hourly water and solute load of two i.v. fluid maintenance regimens commonly used in clinical practice. For a 70 kg patient, dextrose water 5% administered at 1.5 ml kg h (lower left) contains the equivalent of two 50 ml syringes of water and 5 g dextrose (approximate sugar content of a small handful of raisins). In contrast, 10 ml kg h is the equivalent of fourteen 50 ml syringes of water and the salt content of ten 32.5 g bags of crisps. (Image courtesy of Department of Medical Photography, Derriford Hospital.)