Comparison of Respiratory Variations of Subclavian Vein and Inferior Vena Cava in Hospitalized Patients with Kidney Disease

Figures & data

Table 1 Clinical Characteristics of Patients and Encounters

Individual Patient Characteristics	Longitudinal View SCV CI with IVC CI (n=68) (%)	Transverse View SCV CI with IVC CI (n=34) (%)	P values LLR
Age (median, range) years	55 (31–85)	54 (26–89)	0.704^&
Gender (male)	47 (69)	27 (79)	0.264
Hospital survival	52 (76)	15 (44)	0.0013
Reason for consult			0.065
AKD	22 (32)	15 (44)
AKD on CKD	13 (19)	8 (24)
CKD	3 (4)	1 (3)
ESKD on HD	26 (38)	8 (24)
ESKD on PD	4 (6)	0 (0)
Other	0 (0)	2 (6)
Primary disease states
Infection/sepsis/septic shock	35 (51)	14 (41)	0.326
Respiratory failure	27 (40)	16 (47)	0.479
Bleeding	8 (12)	4 (12)	1.000
Cardiac disease	15 (22)	6 (18)	0.600
Hepatitis/shock liver	9 (13)	3 (9)	0.505
Secondary disease states
HTN	35 (51)	14 (41)	0.326
DM	38 (56)	13 (38)	0.092
Cardiac disorders	29 (43)	15 (44)	0.888
Cirrhosis/liver failure	10 (15)	8 (24)	0.279
Morbid obesity	4 (6)	1 (3)	0.499
Anterior abdominal surgery	2 (3)	0 (0)	0.200
Intra-abdominal hypertension*	0 (0)	1 (3)	0.137
Individual encounter characteristics	Longitudinal view SCV CI with IVC CI (n=121) (%)	Transverse view SCV CI with IVC CI (n=39) (%)
ICU location	84 (69)	36 (92)	0.0017
Ventilatory support	44 (36)	21 (54)	0.055

Notes: Contingency tables were analyzed using log likelihood ratio tests; ages of the two cohorts were compared using t-test assuming unequal variance. ^&t-test assuming unequal variances. *Intra-abdominal hypertension (bladder pressure > 20 mmHg).

Abbreviations: AKD, acute kidney disease; CKD, chronic kidney disease; DM, diabetes mellitus; ESKD, end-stage kidney disease; HD, hemodialysis; HTN, hypertension; ICU, intensive care unit; IVC CI, inferior venal cava collapsibility; PD, peritoneal dialysis; SCV CI, subclavian vein collapsibility; LLR, log likelihood ratio.

Figure 1 Relationship of paired SCV CI to IVC CI values for encounters determined for all data (A), and different subgroups including transverse versus longitudinal SCV views (B), ventilated versus non-ventilated encounters (C), no central venous (CV) access versus CV access versus arterio-venous fistula (AVF) versus other* (peritoneal dialysis access (n=6) or femoral access (n=2)) (D), and AKD versus AKD on CKD versus ESKD (E). The IVC CI cut-offs of 20% and 50% are indicated by vertical-dotted lines.

Abbreviations: AKD, acute kidney disease; CKD, chronic kidney disease; ESKD, end-stage kidney disease receiving dialysis therapy; IVC CI, inferior vena cava collapsibility index; SCV CI, subclavian vein collapsibility index.

Figure 2 Sensitivity and specificity plots for various SCV CI cut-offs as predictors for whether IVC CI is <20% or >50% for spontaneous breathing and ventilated encounters. Solid circles are sensitivity and open circles are specificity. The solid lines are the sigmoidal fit to the data constrained to maximum and minimum sensitivities and specificities of 100% and 0%, respectively. The SCV CI cut-off at which the sensitivity and specificity are equal is indicated by the vertical lines. Sensitivity and specificity plots for various SCV CI cut-offs as predictors for whether IVC CI is <20% for spontaneous breathing encounters (A), <20% for mechanically ventilated encounters (B), >50% for spontaneous breathing encounters (C), >50% for mechanically ventilated encounters (D). Sensitivity and specificity plots for various SCV CI cut-offs from data derived from published reports, as predictors for whether IVC CI is <20% for spontaneous breathing encounters for medical patients (Munir et al¹⁶) (E), <20% for spontaneous breathing and mechanically ventilated encounters for surgical ICU patients (Kent et al¹³) (F), >50% for spontaneous breathing encounters for medical patients (Munir et al¹⁶) (G), and >50% for a combination of spontaneous breathing and mechanically ventilated encounters for surgical ICU patients (Kent et al¹³) (H). For the data from Munir et al,¹⁶ collapsibility index ((max-min)/max) *100% was derived from (1-the ratio of min/max) for both SCV CI and IVC CI.

Table 2 Relationship of Subclavian Vein to Inferior Vena Cava Data for Our Study, and Comparison to Data Derived from Previous Studies

Author/Year	Kaptein (Current study)				^gMunir (2007)^Citation16		^gMunir (2007)^Citation16	^gKent (2013)^Citation13
Patient population	Medical with acute and/or chronic kidney disease				Medical requiring echocardiography			Surgical ICU
Respiratory status	Spontaneous breathing		Mechanical ventilation		Spontaneous breathing		Spontaneous breathing	Mixed Spontaneous breathing and Mechanical ventilation
Patient position for SCV & IVC US	30 to 45 degrees (Subclavicular)		30 to 45 degrees (Subclavicular)		IVC flat/SCV 45 degrees (Supraclavicular)		IVC flat/SCV flat (Supraclavicular)	Not specified (Subclavicular)
Correlation of SCV CI to IVC CI	0.67 (n=95)^a		0.75 (n=65)^a,c		0.69 (n=39)^a		0.34 (n=39)^b	0.78 (n=94)^a
SCV CI cut-offs (%) and (95% confidence limits) at maximal Sensitivity and Specificity
IVC CI hypervolemia cut-off (%) (IVC CI<20%)	22 (21 to 23)^e		22 (21 to 23)^e		32^d (30 to 34)^e		N/A	23 (23 to 24)^e
IVC CI hypovolemia cut-off (IVC CI>50%)		39 (37 to 41)^e		39 (38 to 40)^e		39 (37 to 40)^e	N/A		40 (40 to 41)^e
SN/SP (%)	74 (72 to 75)^e	70 (69 to 73)^e	88 (86 to 89)^e	91 (89 to 93)^e	81 (77 to 85)^e	82 (80 to 85)^e	N/A	81 (80 to 82)^e	85 (84 to 89)^e
AUC (area±SD)	0.828±0.043^f	0.739±0.058^f	0.917±0.037^f	0.925±0.032^f	0.826±0.078^f	0.871±0.058^f	N/A	0.878±0.035^f	0.924±0.035^f
Concordance of IVC CI assessment to SCV CI assessment	Hypervolemia/not hypervolemia	Hypovolemia/not hypovolemia	Hypervolemia/not hypervolemia	Hypovolemia/not hypovolemia	Hypervolemia/not hypervolemia	Hypovolemia/not hypovolemia	N/A	Hypervolemia/not hypervolemia	Hypovolemia/not hypovolemia
Concordance (%)	72	71	85	89	77	82	N/A	77	84
PPV (%)	53	39	86	67	68	72	N/A	74	30
NPV (%)	84	90	83	98	85	91	N/A	80	99
+ LR	2.5	2.4	5.0	8.0	3.1	4.2	N/A	3.1	5.1
- LR	0.43	0.42	0.17	0.09	0.25	0.17	N/A	0.27	0.17

Notes: ^aP<0.001and ^bP<0.05indicates the significance of the correlation (R). ^cP=0.32 comparing correlation (R) values for spontaneous breathing encounters with mechanically ventilated encounters for our data. ^dCut-off may vary from that of the other two studies due to widely scattered and small data set (Figure 2E). The right SCV was imaged from the supraclavicular approach with the probe positioned above the medial end of the clavicle in the fossa between the sternal and the clavicular heads of the sternocleidomastoid muscle.¹⁶ e95% confidence interval. ^fP <0.001 testing whether AUC is =0.5. ^gData were extracted and transformed from published figures. For the data from Munir et al,¹⁶ collapsibility index ((max-min)/max) was derived from (1-the ratio of min/max) for both SCV CI and IVC CI. +LR is likelihood of a positive result for a positive patient/likelihood of a positive result for negative patient eg for a +LR >5.0, a positive result is 5 times more likely to be a true positive rather than a false positive. -LR is similar, eg for a –LLR <0.2, a negative result is 5 times more likely to be a true negative rather than a false negative. (is 0.2 times as likely to be a positive patient than a negative patient). +LR and –LR are independent of prevalence (ie distribution of the data) whereas PPV and NPV (positive predictive value and negative predictive value; fraction of positive/negative predictions that are correct) are affected by prevalence. DI and CI are mathematical transformations of each other as follows: DI =CI/(100%-CI) * 100%; CI=DI/(100%+DI) * 100%. Thus, an IVC CI cut-off of <20% for hypervolemia with spontaneous breathing and mechanical ventilation corresponds to an IVC DI cut-off of <25% and an IVC CI cut-off of >50% for hypovolemia in both spontaneous breathing and mechanical ventilation encounters corresponds to an IVC DI cut-off of >100%. An SCV CI cut-off of <22% corresponds to an SCV DI cut-off of <28% for predicting hypervolemia and SCV CI cut-off of >39% corresponds to a SCV DI cut-off of >64% for predicting hypovolemia.

Abbreviations: AUC, area under the curve expressed as a fraction of the total area; CI, collapsibility index; ICU, intensive care unit; IVC, inferior vena cava; LR, likelihood ratio; NPV, negative predictive value; PPV, positive predictive value; SCV, subclavian vein; SN, sensitivities; SP, specificities; US, ultrasound.

Munir A, D’Cruz I, Minderman D, Shelton M. The right subclavian vein can be used as a surrogate of the inferior vena cava, as an echocardiographic indicator of systemic venous congestion. Am J Med Sci. 2007;333(5):280–284. doi:10.1097/MAJ.0b013e3180533fa117505169

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Kent A, Bahner DP, Boulger CT, et al. Sonographic evaluation of intravascular volume status in the surgical intensive care unit: a prospective comparison of subclavian vein and inferior vena cava collapsibility index. J Surg Res. 2013;184(1):561–566. doi:10.1016/j.jss.2013.05.04023764308

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