1. Units consumed per 100 patients
Cost analysis of patients undergoing cardiac surgery managed with or without cerebral oximetry (INVOS)
M. Bennett, D. Walsh and S. Bennett
Cardiothoracic Unit, Castle Hill Hospital, UK
Presented at ACTA UK - Association of Cardiothoracic Anaesthetists Meeting June 2011 (the poster won 1st prize)
Introduction
Cerebral oximetry (rSO2) using near infrared spectroscopy has been practiced in our unit using INVOS for some time. A 100 patient audit examining the efficacy of the use of INVOS showed a reduction in the mortality rate and post-operative length of stay (LOS) against national statistics.1 This is a cost analysis of the use of INVOS based on that audit.
Aim
To analyse the cost effectiveness of the use of INVOS in mixed cardiac surgery by comparing the INVOS audit group to a control group. Also, to examine the cost effectiveness within coronary bypass (CABG) only patients in order to compare the results to the existing INVOS literature. 2,3
Method
A cost analysis of the INVOS group was done by comparing against 100 control patients who underwent cardiac surgery immediately prior to the INVOS audit. Hospital finance department data was used to calculate the cost of patient care.
The areas for comparison were cost of: INVOS equipment used during the operation; ICU post-operative LOS; stroke rehabilitation; non-ICU post-
operative LOS.
Previous INVOS studies have focused on CABG only patients. 2,3 In order to compare outcomes with those found in these papers we selected the CABG only patients out of the INVOS group and the control group. This data was then analysed to give a final saving for CABG only patients.
Results
Despite having the cost of the probes, all other outcomes had a reduced cost in the INVOS group. Overall there is shown to be a saving of £102,000 per 100 patients undergoing cardiac surgery.
There was improvement in all outcomes in both INVOS (n=65) and the control group (n=66) once the criteria of CABG only had been applied. LOS in ICU and non-ICU was reduced in both groups, and neither group contained an incident of stroke.
Units consumed per 100 patients
Cost per unit (£)
Cost per 100 patients (£)
INVOS
Control
INVOS probes
200
100
20,000
ICU (days)
179.4
233.3
1,212
227,400
282,800
Stroke rehab (days)
67 .3
367
24,700
Non-ICU (days)
810.3
934.7
255
206,600
238,300
TOTALS
444,000
546,000
TOTAL SAVING
Per 100 patients
£102,000
This resulted in an even greater saving of £114,000 per 100 CABG only patients.
Both comparisons, mixed and CABG only, showed the biggest cost saving to be due to a reduction in post operative LOS both in ICU and on the wards. This correlates with the findings of previous INVOS studies. 2,3
Table 1 Cost comparison for the two mixed cardiac groups
Discussion
This cost analysis shows a significant saving when using INVOS in the management of both mixed and CABG only cardiac surgery. Despite the extra cost for the probes, due to the reduction in the LOS both in ICU and on the wards, there is significant reduction in the cost of cardiac surgery by using INVOS. The CABG only patients showed the greatest saving of £114,000 per 100 patients.
The reduction in both ICU and non-ICU LOS seen in the audit data is strongly supported by existing literature. 2,3 However, these papers only considered CABG patients and did not undertake any cost analysis. Further analysis with mixed cardiac surgery and a fully randomised trail is required. This is currently underway.
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References
1. Bennett S, Haworth CM, Bennett M, Walsh D. Active management using INVOS data in adult cardiac surgery – An audit 2010 (ACTA Brighton, 2010).
2. Slater JP, Guarino T, et al. Ann Thorac Surg Cerebral oxygen desaturation predictscognitive decline and longer stay in hospital after cardiac surgery 2009; 87: 36–45.
3. Murkin JM, et al. Anesth. Analg. Monitoring brain oxygen saturation during coronary bypass surgery: A randomized, prospective study2007; 104: 51-58 .