Hyperoxia during colon surgery is associated with a reduction of xanthine oxidase activity and oxidative stress in colonic mucosa

Figures & data

Table 1. Demographic data of the two groups of cancer patients

	0.30 FiO2 group	0.80 FiO2 group
Age (year)	67.5 (43–77)	66.5 (42–76)
Sex (Male:female)	9:3	10:2
Weight (kg)	71.5 (61–91)	67.5 (52–112)
Diagnosis: colon-rectum cancer	12	12
Hemicolectomy	8	7
Sigmoid anterior section	4	5

Values expressed as median (range). Differences were analysed with two-tailed tests for non-parametric data: Mann–Whitney U and Wilcoxon tests. P values <0.05 were considered statistically significant. No differences were found between the study groups.

Table 2. Intraoperative values of clinical and physical status of the two groups of patients

	0.30 FiO2 group	0.80 FiO2 group
Duration of surgery (minute)	195 (150–270)	200 (145–260)
Number of patients transfused	3	4
Volume infusion (l)	4.5 (3.0–5.0)	4.5 (3.5–5.2)
Average core temperature (°C)	36 (35–37)	36 (35–37)
Average SpO2 (%)	97 (95–99) 99	(97–100)*
Average mean arterial pressure (mmHg)	83 (72–91)	86 (65–100)

Values expressed as median (range). Differences were analysed with two-tailed tests for non-parametric data: Mann–Whitney U and Wilcoxon tests. P values <0.05 were considered statistically significant. No differences were found between the study groups except in average SpO₂.

*Average SpO₂ (oxygen saturation on pulse oxymetry) values in the 0.80 group were higher than in the 0.30 group values (P < 0.001).

Figure 1. Effects of FiO₂ on arterial blood gas analysis (PaO₂ and PaCO₂) in the two groups (0.30 FiO₂ and 0.80 FiO₂) of cancer patients, before surgery and after surgery. Values expressed as scatter plot and median (horizontal bars). Differences were analysed with two-tailed tests for non-parametric data: Mann–Whitney U and Wilcoxon tests. P values <0.05 were considered statistically significant. (A and C), PaO₂ values in the 0.80 FiO₂ group were significantly higher (P < 0.001) than in the 0.30 FiO₂ group's values, before and after surgery. (B and D), in PaCO₂ values, no differences were found between the study groups, before and after surgery.

Table 3. Effects of FiO₂ on arterial blood gas analysis in the two groups of cancer patients

	0.30 FiO2 group	0.80 FiO2 group	P
Before surgery
pH	7.43 (7.36–7.56)	7.42 (7.38–7.53)	0.953
PaO2 (mmHg)	95 (72–131)	291(181–491)	<0.001
PaCO2 (mmHg)	33 (24–37)	33 (23–40)	0.854
PaO2/FiO2	338 (239–443)	386 (226–614)	0.169
SpO2 (%)	98 (95–100)	100 (99–100)	< 0.001
Haemoglobin (g/dl)	12.5 (10.30–15.8)	12.3 (10.4–12.8)	0.678
After surgery
pH	7.37 (7.33–7.40)	7.36 (7.26–7.42)	0.726
PaO2 (mmHg)	103 (74–131)	311 (246–383)	<0.001
PaCO2 (mmHg)	31 (23–36)	32 (24–38)	0.931
PaO2/FiO2	350 (285–522)	393 (286–479)	0.073
SpO2 (%)	97 (90.0–100)	100 (99–100)	<0.001
Haemoglobin (g/dl)	11.7 (9.4–14.8)	11.9 (10.0–14.4)	0.8010

Values expressed as median (range). Differences were analysed with two-tailed tests for non-parametric data: Mann–Whitney U and Wilcoxon tests. P values <0.05 were considered statistically significant. SpO₂ (haemoglobin oxygen saturation) and PaO₂ (oxygen partial pressure) values in the 0.80 FiO₂ group were significantly higher (P < 0.001) than in the 0.30 FiO₂ group's values, before and after surgery.

Figure 2. Effects of FiO₂ on levels of oxidative stress markers like MDA and GSSG in arterial blood of the two groups (0.30 FiO₂ and 0.80 FiO₂) of cancer patients, before surgery and after surgery. Values expressed as scatter plot and median (horizontal bars). Differences were analysed with two-tailed tests for non-parametric data: Mann–Whitney U and Wilcoxon tests. P values <0.05 were considered statistically significant. (A and B), MDA and GSSG values respectively – for these markers no differences were found between the study groups before surgery. (C and D), MDA and GSSG, respectively, in the 0.30 FiO₂ group were significantly higher than in the 0.80 FiO₂ group after surgery.

Figure 3. Effects of FiO₂ on MDA levels, XO activity, XDH activity, XO + XDH activities, and XO/(XO + XDH) ratio in colonic mucosa from excised colon in the two groups of cancer patients. MDA, malondialdehyde; XO, xanthine oxidase; XDH, xanthine dehydrogenase. Values expressed as scatter plot and median (horizontal bars). Differences were analysed with two-tailed tests for non-parametric data: Mann–Whitney U and Wilcoxon tests. P values <0.05 were considered statistically significant. (A) MDA values were significantly lower in the 0.80 group than in the 0.30 group. (B) XO activity was significantly lower in the 0.80 group than in 0.30 group. (C) On XDH activity no differences were found between the study groups. (D) On XO + XDH activities no differences were found between the study groups. (E) On XO/(XO + XDH) ratio, values were significantly lower in 0.80 group than 0.30 group.

Figure 4. Effects of FiO₂ on the correlations between MDA levels and XO activity and XO/(XO + XDH) ratio in colonic mucosa from removed piece of colon in the two groups of patients. MDA, malondialdehyde; XO, xanthine oxidase; XDH, xanthine dehydrogenase. r, Pearson's correlation coefficient. XO enzymatic activity and XO/(XO + XDH) ratio as independent variables and MDA as a dependent variable. P values <0.05 were considered statistically significant. (A) correlation between MDA levels and XO activity was very significant in 0.30 FiO₂ group. (B) correlation between MDA levels and XO activity was significant in 0.80 FiO₂ group and the r value was lower than 0.30 FiO₂ group. (C) correlation between MDA levels and XO/(XO + XDH) ratio on 0.30 FiO₂ group was statistically significant. (D) correlation between MDA levels and XO/(XO + XDH) ratio in 0.80 FiO₂ group was not statistically significant and the r value was lower than 0.30 FiO₂ group.