Evaluation of two different fluids regimens on central venous-to-arterial Carbon Dioxide difference (pCO₂ gap) - a randomized controlled trial

Figures & data

Table 1. Demographic Characteristics, fluid intake, type of surgery and ASA status fluid intake,type of surgery and ASA status fluid intake,type of surgery and ASA status of included participants in Crystalloids and Colloids groups.

	Crystalloids(n = 41)	Colloids(n = 41)	Significance
	mean (SD)
Age (years)	51.58(7.58)	50.85(7.84)	t = .429, p = .669
BMI	28.17(2.46)	28.19(2.45)	t = −.045, p = .964
Duration (min)	266.59(9.64)	267.32(10.72)	t = −.325, p = .746
	559.27(46.49)	558.29(49.89)
	Frequency (%)
Gender:
Female	15(36.6)	13(31.7)	X^2 0.217
Male	26(63.4)	28(68.3)	p .641
ASA classification:
I	22(53.7)	24(58.5)
II	14(34.1)	14(34.1)	MCp = .849
III	5(12.2)	3(7.3)
Type of surgery:
Hip	7(17.1)	5(12.2)
LL	4(9.8)	6(14.6)
Pelvis	12(29.3)	10(24.4)	X2 1.31
Reconst	4(9.8)	6(14.6)	p .859
Spine	14(34.1)	14(34.1)

t: Independent sample t test

X²: Chi-square test

Results≤.05 are significant

Figure 1. Flow diagram of Demographic Characteristics

Table 2. Comparison of different parameters between Crystalloids and Colloids groups

Parameter	Group		Significance*
	Crystalloids	Colloids
	Mean (Std. Deviation)
Baseline infusion (Lactated Ringer) ml	559.27(46.49)	558.29(49.89)	.927
Bolus infusion(ml)	2612.20(226.04)	1619.51(253.19)
TOTAL INPUT	3171.46(266.22)	2177.8(295.41)
BLOOD LOSS (ml)	764.63(101.39)	758.78(117.32)	.810
Heart Rate:
Baseline	69.27(3.64)	68.98(4.81)	.757
1 Hour	71.32(4.06)	70.46(4.47)	.369
2 Hours	71.71(3.36)	70.83(4.20)	.369
3 Hours	72.24(3.88)	71.22(4.36)	.299
4 Hours	72.98(3.68)	71.73(3.95)	.265
5 Hours	73.34(3.52)	71.78(4.21)	.144
PACU	73.80(3.50)	72.59(4.0)	.072
Mean Arterial Pressure (mmhg):
Baseline	89.93(2.42)	88.78(2.97)	.059
1 Hour	90.02(2.84)	88.54(3.52)	.038**
2 Hours	89.88(3.27)	89.17(3.34)	.336
3 Hours	89.49(3.29)	89.24(3.76)	.756
4 Hours	89.90(3.72)	89.17(4.16)	.404
5 Hours	90.07(3.35)	89.22(4.61)	.341
PACU	90.34(2.98)	89.66(3.47)	.343
Central Venous Pressure (mmhg)
Baseline	7.24(.88)	7.44(.808)	.301
1 Hour	9.98(1.17)	9.78)1.275	.473
2 Hours	10.51(1.28)	10.37(1.47)	.634
3 Hours	10.76(1.62)	11.05(1.93)	.461
4 Hours	10.95(1.49)	11.22(1.31)	.391
5 Hours	11.00(1.22)	11.22(1.08)	.393
PACU	11.05(1.11)	11.39(1.41)	.228
Oxygen Saturation(%)
Baseline	96.37(1.24)	95.93(1.10)	.094
1 Hour	98.41(1.09)	98.29(.92)	.588
2 Hours	98.34(1.01)	98.24(1.01)	.665
3 Hours	98.27(1.14)	98.27(.83)	1.000
4 Hours	98.41(.97)	98.46(.86)	.811
5 Hours	98.59(.80)	119.66(135.96)	.327
PACU	98.41(.83)	98.24(.83)	.356
Urine output(ml)
Baseline	0	0	.476
1 Hour	67.44(8.74)	68.78(8.19)	.718
2 Hours	64.63(5.04)	64.15(6.97)	.149
3 Hours	62.32(6.81)	64.27(5.19)	.081
4 Hours	62.68(6.43)	64.88(4.67)	.606
5 Hours	64.27(6.47)	65.00(6.32)	.832
PACU	65.63(7.46)	65.98(7.09)	.476
Serum Lactate(mmol/L)
Baseline	1.0705(.09)	1.032(.100)	.083
1 Hour	1.061(.08)	1.03(.09)	.171
2 Hours	1.11(.10)	1.05(.097)	.005**
3 Hours	1.12(.11)	1.09(.11)	.234
4 Hours	1.18(.09)	1.06(.10)	<.001**
5 Hours	1.18(.09)	1.139(.09)	.017**
PACU	1.08(.11)	1.0312(.08)	.015**
Central Venous Oxygen Saturation
Baseline	78.68(2.04)	79.10(1.85)	.339
1 Hour	78.15(1.96)	78.90(2.02)	.090
2 Hours	78.80(2.07)	79.32(2.38)	.302
3 Hours	78.07(1.95)	78.63(2.41)	.251
4 Hours	77.24(1.88)	78.07(2.04)	.059
5 Hours	76.37(1.69)	77.51(1.96)	.006**
PACU	75.59(1.62)	77.00(1.94)	.001**
Carbon Dioxide gap(ml)
Baseline	4.35(.46)	4.34(.54)	.896
1 Hour	4.315(.48)	4.39(.57)	.506
2 Hours	4.62(.65)	4.64(.62)	.877
3 Hours	4.824(.79)	4.56(.82)	.148
4 Hours	4.97(.86)	4.52(.89)	.023**
5 Hours	5.09(.92)	4.57(.87)	.011**
PACU	5.27(.86)	4.88(.85)	0.001**

*Independent sample t-test

**Results≤ .05 are statistically significant

Figure 2. Mean serum Lactate (mmol/L) along time between two treatment groups

Figure 3. Mean Central Venous Oxygen Saturation (%) along time between two treatment groups

Figure 4. Mean Carbon Dioxide gap (mmHg) along time between two treatment groups

Table 3. Correlation of different parameters with Carbon Dioxide gap (ml) at 5 hours intraoperative

		Carbon Dioxide gap(ml) at 5 hours intraoperative
Heart Rate	r	−.071
	p-value	.527
Mean Arterial Pressure(mmhg)	r	.144
	p-value	.197
Central Venous Pressure(mmhg)	r	−.008
	p-value	.944
Oxygen Saturation (%)	r	−.040
	p-value	.721
Blood loss in ml	r	−.151
	p-value	.174
Serum Lactate	r	.133
	p-value	.234
Central Venous Oxygen Saturation	r	−.180
	p-value	.106

r: Pearson’s correlation coefficient

Table 4. Linear regression model for prediction of Carbon Dioxide gap

b (95.0% Confidence Interval for B)	SE	Standardized Beta	t	Sig.
−.517(−.913 to −.913)	199	−.279	−2.602	.011

Backward stepwise regression model, F = .676, p = .001

Average Carbon Dioxide gap for crystalloids group = 5.09 mmhg

Average Carbon Dioxide gap for colloid group = 5.09– 0.517 = 4.57 mmhg

b Unstandardized beta

SE: Std. Error

R² 7.8%, adjusted R² 6.6%

Variables excluded from model due to non-significance by stepwise approach include MABP, CVP, Blood loss and oxygen saturation at 5 hours intraoperative