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Page 4 of 7 Aslam et al. Mini-invasive Surg 2018;2:10 I http://dx.doi.org/10.20517/2574-1225.2017.42

Table 2. Comparisons of the post-operative outcomes for the intra-operative CO monitoring group (treatment group) and the
no intra-operative CO monitoring group (control group)
Post-operative outcomes Treatment group Control group P
30-day mortality 0 1 NS
90-day mortality 0 0
30-day morbidity 0 0
Clavien-Dindo III-IV, n (%) 4 (5.7) 8 (5.5)
Readmission in 30days, n (%) 7 (10.1) 8 (5.5)
Length of hospital stay (days), median (range) 6 (2-92) 7 (2 -112)
Length of stay in HDU 0.01
Patients, n (%) 17 (24) 56 (39)
Median (range) days 2 (1-6) 2 (1-13)
Length of stay in ICU
Patients, n (%) 0 11 (7.6)
Median (range) days 2 (1-15)
NS: not significant (P > 0.05); HDU: high dependency unit (level 2 - patients needing single organ support excluding mechanical
ventilation such as renal hemofiltration or inotropes and invasive blood pressure monitoring. Staffed with one nurse to two patients); ICU:
intensive care unit (level 3 - patient requiring two or more organ support or needing mechanical ventilation alone. Staffed with one nurse
for per patient and usually with a doctor present in unit 24 h per day)

admitted to ICU in the control group. This could be due to several reasons: firstly, it may be that patients
with intraoperative CO monitoring received optimised fluid therapy and subsequently required lower
level of care, but the lack of data for the volumes of fluid administered to all patients leaves us unable to
draw this conclusion. Secondly, CO monitoring provided the anaesthetists with up-to-date and accurate
data about cardiovascular status and stability and may have influenced the need for postoperative care,
hence, patients who were performing well having their care needs downgraded. Thirdly, adequate fluid
administration intraoperatively would have reduced GI complications resulting from fluid overload or
hypovolaemia. Fluid overload can lead to several harmful effects such as, generalised oedema, hindering
[9]
tissue healing, detrimental effects on cardio-pulmonary functions, delayed recovery of gut functions ,
[10]
decreased muscular oxygen tension , increased risk of complications [11,12] and is linked to poor survival
[13]
rates . The effectiveness of intra-operative cardiovascular monitoring to reduce such complications has
been proven in other published studies [25-30] . On the other hand, hypovolemia can lead to hypoperfusion,
circulatory collapse, impaired wound healing, anastomotic leak [14,15] , bacterial translocations and endo-
[31]
toxaemia with activation of the systemic inflammatory response ; all of which account for the need of
[2]
prolonged stay in high level care facilities post-operatively. Noblett et al. have shown a reduction in peak
systemic inflammatory cytokine (IL-6) levels for patients undergoing CO monitoring with Doppler. This
study concluded that the Doppler intervention reduced the systemic inflammatory response to surgical
trauma, preserved splanchnic perfusion and thereby reduced gut-related inflammatory responses. Fourthly,
results could also have been affected by the fact that, within the control group, more patients had open
surgical procedures for malignancy, and many cases were converted to open (n = 27), thus those patients,
subsequently, required more HDU/ICU admissions. Therefore, the availability of intra-operative CO data in
that patient group would have influenced the decision for admission to HDU/ICU care is not known.

The median length of hospital stay for treatment group was shorter in comparison to control group (6 vs.
7 days). But, this difference did not reach statistical significance (P = 0.078). All patients in the treatment and
control groups were cared for on the ERAS programme. Outcomes associated with ERAS are dependent on
multiple peri-operative factors.

The limitations of this study are a lack of data about the accurate volume of intra-operative fluids
administrated, intra-operative CO variations, P-POSSUM scores and the rationale of the decision for
admission to different levels of post-operative care areas. Availability of such data would have allowed
adjusting for these confounding factors to assess post-operative outcomes more accurately. This study lacks
the data about study population representative for other surgeons, variability in ethnicity and socioeconomic