5.1 The economic evidence comprises a cost analysis submitted by the manufacturer, data from a National Institute for Health Research's Health Technology Assessment and economic results from the NHS Technology Adoption Centre's project on intra-operative oesophageal doppler-guided fluid management.
5.2 The manufacturer's cost analysis was undertaken from the perspective of the NHS. The model evaluated separately the cost impact of using the CardioQ-ODM in patients undergoing surgery and in a critical care environment. Both arms of the model used the same comparators. The CardioQ-ODM plus conventional clinical assessment was compared with:
conventional clinical assessment alone
central venous pressure monitoring plus conventional clinical assessment
pulse pressure waveform analysis plus conventional clinical assessment
central venous pressure monitoring plus pulse pressure waveform analysis plus conventional clinical assessment
central venous pressure monitoring plus the CardioQ-ODM plus conventional clinical assessment.
The key outcome in the cost analysis was length of in-hospital stay, with adverse events and complications captured through their impact on length of stay. The time horizon chosen for the model was the period of in-hospital care.
5.3 In the cost model for patients undergoing surgery, the baseline length of hospital stay was 7.52 days (0.16 days in the critical care unit, 0.58 days in the high-dependency unit and 6.78 days in a general ward). The baseline length of stay is the stay associated with patients whose fluid status is monitored using conventional clinical assessment alone. The base-case analysis assumed that monitoring with the CardioQ-ODM was associated with a reduction in length of stay of 50% in the critical care unit, and 25% in both the high-dependency unit and the general ward, resulting in a total reduction in length of stay of 1.92 days. The External Assessment Centre considered that a 35% reduction in length of stay in the critical care unit was more appropriate for monitoring with the CardioQ-ODM, based on the evidence from randomised controlled trials. Central venous pressure monitoring was assumed to have no impact on length of stay in any setting. Some data used to populate the manufacturer's cost model were considered by the External Assessment Centre to be inaccurate and the Centre updated the model with more accurate data relating to the costs of nurse time and bed-days in the high-dependency unit. The base-case analysis reported that the costs associated with CardioQ-ODM monitoring in patients undergoing surgery were lower than for any of the comparators. The corrected incremental cost for the most relevant comparator, namely central venous pressure monitoring, was £1062 in favour of the CardioQ-ODM based on a 7.5-day hospital stay.
5.4 Deterministic sensitivity analyses were undertaken for a range of parameter values, including reduction in length of stay in the critical care unit, high-dependency unit and general ward, baseline length of stay, device use, general ward cost, and purchase and maintenance costs for comparator devices. The main factors affecting cost were changes in the length of stay parameters. The sensitivity analyses showed CardioQ-ODM to be cost saving in all cases, except when it is assumed that central venous pressure monitoring reduces the length of stay in the general ward by 30%.
5.5 In the cost model exploring the use of the CardioQ-ODM in patients on a critical care unit, the baseline length of stay was 36 days. This was subdivided into 12 days on the critical care unit and 24 days on the general ward. Data for reduction in length of stay relating to CardioQ-ODM monitoring were derived from the only relevant randomised controlled trial available. The base-case analysis assumed a 20% reduction in length of stay on both the critical care unit and the general ward for patients who had CardioQ-ODM monitoring. In the same analysis, the comparator, pulse pressure waveform analysis, was assumed to lead to no reduction in length of stay on the critical care unit, and a 10% reduction in length of stay on the general ward. Some data used to populate the manufacturer's cost model were considered inaccurate by the External Assessment Centre who updated the model with more appropriate data relating to the cost of nurse time, bed-day costs in the high-dependency unit and for three incorrect values that were typographical errors. Additional calculations were carried out by the External Assessment Centre on the impact of pulse pressure waveform analysis on the length of stay in the critical care unit and the subsequent length of stay on the general ward. In the revised calculation, a reduction of length of stay on the general ward of 41% rather than 10% was applied on the basis of the results of Pearse et al. (2005), and the incremental cost saving with the CardioQ-ODM was £1285 compared with £3064 as cited in the manufacturer's submission.
5.6 The Committee heard from the experts that when clinicians start to use the CardioQ-ODM, they are initially reluctant to stop using central venous pressure monitoring until their confidence with the new technology grows. The Committee noted that the cost model showed a marginal reduction in incremental cost to £1022 when central venous pressure monitoring was compared with the combination of central venous pressure and CardioQ-ODM monitoring, from the £1062 when central venous pressure monitoring was compared with CardioQ-ODM monitoring alone.
5.7 The Committee noted that the cost savings associated with the use of the CardioQ-ODM for patients undergoing surgery were similar in the manufacturer's cost analysis and in the NHS Technology Adoption Centre's report.
5.8 The Committee concluded that the lack of convincing evidence of benefit when the CardioQ-ODM was used in patients on the critical care unit who have not had surgery means that there is considerable uncertainty about potential cost savings in this clinical setting.