Ultrasonographic Assessment of Gastric Volume in Fasted Patients Undergoing Gastrointestinal Endoscopy Under Sedation

Figures & data

Figure 1 Upper abdominal sonographic image showing an empty stomach antrum. Antrum is pointed out by 4 x’s corresponding to its 2 perpendicular diameters.

Abbreviations: AA, longitudinal diameter; BB, anteroposterior diameter; Ao, aorta; L, liver; P, pancreas; R, rectus abdominis muscle; Sma, superior mesenteric artery.

Figure 2 Gastric ultrasound performed based on the qualitative 3-point grade assessments. Antrum is pointed out by 4 x’s corresponding to its 2 perpendicular diameters. (A) The empty antrum (Grade 0) in the semi-recumbent (A1) and right lateral decubitus (A2) positions appear small and “flat”. (B) The antrum with minimal, insignificant amount of fluid (Grade 1), a small amount of fluid is detectable only in the right lateral decubitus position (B2). (C) The antrum with significant fluid content (Grade 2), fluid is evident in both positions, but more marked in the right lateral decubitus position (C2).

Abbreviations: AA, longitudinal diameter (D1); BB, anteroposterior diameter (D2); Ao, aorta; L, liver; P, pancreas; Sma, superior mesenteric artery.

Table 1 Patient Demographics, Gastric Ultrasound Examination, and Gastric Fluid Volume Data

	Grade 0	Grade 1	Grade 2	All Subjects	P-value
N	156	449	131	736
Age (years)	47.8±13.8	45.5±12.5	45.9±14.0	46.1±13.1	0.189^a
Male (%)	71(45.5)	201(44.8)	55(42.0)	327(44.4)	0.814^b
Female (%)	85(54.5)	248(55.2)	76(58.0)	409(55.6)
Weight (kg)	58.6±11.5	58.6±10.0	58.4±11.0	58.6±10.5	0.974^a
Height (cm)	161.2±7.8	161.7±7.3	161.7±7.5	161.6±7.5	0.788^a
BMI (kg/m^2)	22.4±3.4	22.4±3.0	22.3±3.5	22.4±3.2	0.904^a
ASA physical status, n (%)					0.018^c
I	109(14.8)	327(44.4)	79(10.7)	515(69.9)
II	47(6.4)	120(16.3)	49(6.7)	216(29.4)
III	0(0.0)	2(0.3)	3(0.4)	5(0.7)
Semi-recumbent CSA (cm^2)	2.9(2.2, 3.9)	3.2(2.4, 4.1)	4.7(3.3, 6.3)^#,†	3.3(2.4, 4.5)	<0.001^d
RLD CSA (cm^2)	4.5(3.5, 5.8)	6.4(4.8, 8.5)*	8.2(6.1, 11.3)^#,†	6.1(4.5, 8.5)	<0.001^d
Suctioned gastric volume (mL)	7.0(3.0, 13.0)	30.0(20.0, 43.0)*	61.0(46.0, 80.0)^#,†	29.5(14.0, 48.0)	<0.001^d
Suctioned gastric volume (mL/kg)	0.1(0.05, 0.2)	0.5(0.3, 0.8)*	1.1(0.8, 1.4)^#,†	0.5(0.2, 0.8)	<0.001^d
Calculated gastric fluid volume (mL)	33.0(11.2, 51.5)	61.1(35.3, 93.4)*	86.3(58.1, 130.4)^#,†	58.4(30.8, 92.9)	<0.001^d
Calculated gastric fluid volume (mL/kg)	0.5(0.2, 1.0)	1.0(0.7, 1.6)*	1.6(1.0, 2.1)^#,†	1.0(0.6, 1.6)	<0.001^d

Notes: Values are presented as means (Standard deviation SD), median (interquartile range IQR), or number of patients (%). *P<0.05, group Grade 1 vs group Grade 0; ^#P<0.05, group Grade 2 vs group Grade 0; ^†P<0.05, group Grade 2 vs group Grade 1. ^aOne-way ANOVA test. ^bPearson’s chi-squared test. ^cFisher’s exact test. ^dKruskal–Wallis rank sum test.

Abbreviations: BMI, body mass index; ASA, the American Society of Anesthesiologists; CSA, cross-sectional area; RLD, right lateral decubitus.

Figure 3 Flow chart of the study. RLD represents right lateral decubitus.

Figure 4 Receiver operating characteristic curves for the ultrasonographic diagnosis of risk stomach, as defined by a suctioned fluid volume of gastric contents > 1.5 mL/kg of antral CSA in patients with RLD (A) and semi-recumbent positions (B), and defined by a suctioned fluid volume of gastric contents > 100 mL of antral CSA in patients with RLD (C) and semi-recumbent positions (D).

Notes: AUC, area under the receiver operating characteristic curve, with 95% CI. P < 0.001 for the CSA of the RLD position curve.

Abbreviations: CSA, cross-sectional area; RLD, right lateral decubitus.

Figure 5 Bland–Altman analysis demonstrates the agreement between the current calculated volume (CCV) according to mathematical Model (2) and the suctioned volume (SV) through gastroscopy. The y-axis represents the difference between the two values (CCV-SV), and the x-axis represents the mean between the two values (CCV+SV/2). The Orange dotted line (inner dotted lines) represents perfect agreement. The blue solid line is the mean difference or “bias” of the model. The outer dotted lines represent the upper and lower limits of 95% agreement.

Abbreviations: CCV, current calculated volume; SV, suctioned volume.

Table 2 Correlation Analysis Between Gastric Volume and Independent Variables

Independent Variables	Suctioned Gastric Volume
	r	P -value
Sex	−0.040	0.921
Age	−0.186**	<0.001
Height	0.030	0.412
Weight	0.000	0.997
BMI	−0.002	0.953
ASA	0.007	0.850
Semi-recumbent CSA	0.079*	0.032
RLD CSA	0.221**	<0.001
3-point grades	0.712**	<0.001

Notes: *P < 0.05; **P < 0.01.

Abbreviations: BMI, body mass index; ASA, American Society of Anesthesiologists; CSA, cross-sectional area; RLD, right lateral decubitus.

Figure 6 Bland–Altman analysis demonstrates the agreement between the new calculated volume (NCV) according to mathematical Model (3) and the suctioned volume (SV) through gastroscopy. The y-axis represents the difference between the two values (NCV-SV), and the x-axis represents the mean between the two values (NCV+SV/2). The blue solid line is the mean difference or “bias” of the model. The outer dotted lines represent the upper and lower limits of 95% agreement.

Abbreviations: NCV, new calculated volume; SV represents the suctioned volume.