Trends in Cardiac Surgery-Associated Acute Renal Failure in the United States: A Disproportionate Increase after Heart Transplantation

Figures & data

Table 1  Procedural codes used in this study

Procedures	CCS	ICD9-CM	Description
CABG	44	36.10–36.14	Aortocoronary bypass
		36.15–36.16	Internal mammary graft
		36.17–36.39	Other heart revascularization
Valve	43	35.00–35.04	Valvotomy
		35.10–35.14	Valvuloplasty
		35.20–35.28	Valve replacement
		35.96–35.99	Other valve procedures
Mitral valve	43	35.02	Closed valvotomy
		35.12	Open valvuloplasty
		35.23, 35.24	Replacement
Heart transplant	176	37.5, 37.51	Heart transplantation
Diagnosis	CCS	ICD9-CM	Description
ARF	157	584.0, 584.5–9,586	Acute renal failure

Abbreviations: ARF = acute renal failure, CABG = coronary artery bypass graft, CCS = clinical classification software, ICD9-CM = International Classification of Disease 9^th Revision Clinical Modification.

Figure 1.  Hierarchical methodology of definition of groups based on surgical procedure (see text for details). Abbreviations: CABG = coronary artery bypass graft, CCS = clinical classification software, ESRD = end stage renal disease, ICD9-CM = International Classification of Disease 9^th Revision Clinical Modification, MV = mitral valve, NIS = Nationwide Inpatient Sample.

Table 2  Group-wise distribution of the study population

	Heart transplant(Group A) N = 29,176	CABG + MV(Group B) N = 204,515	CABG + OV(Group C) N = 378,253	CABG (Group D) N = 6,756,846	Valve (Group E) N = 1,621,830
Age (yrs)	46.2 (18.2)	69.2 (9.5)	71.8 (9.4)	65.1 (10.5)	59.0 (21.0)
Female (%)	24.6	45.3	32.8	28.2	49.4
Number of grafts	0.1 (0.5)	2.5 (1.1)	2.4 (1.2)	3.4 (1.1)	0
Number of valves	0.0 (0.2)	1.2 (0.4)	1.00 (0.1)	0	1.0 (0.4)
Co-morbidities (out of 29)*	1.0 (1.0)	2.0 (1.4)	1.8 (1.3)	1.7 (1.3)	1.1 (1.1)
ARF (%)	17.0	11.8	6.9	3.6	4.7

Figures represent mean values with standard deviation in parentheses. Number of discharges (N) for each group represents national estimates after application of discharge weights as provided by the NIS.

Abbreviations: ARF = acute renal failure, Htx = cardiac transplantation, CABG = coronary artery bypass graft, MV = mitral valve, OV = other valve.

*List of comorbidities are described by Elixhauser et al.^[18]

Figure 2.  The incidence of ARF in each group (A-E) from 1988 to 2003. Abbreviations: ARF = acute renal failure, CABG = coronary artery bypass graft.

Table 3  Multivariable regression model comparing slopes

Variable	Parameter estimate	p value
Year	0.11	<0.0001
Group (reference group is isolated CABG)
Valve only	−0.16	<0.0001
CABG + valve	−0.53	<0.0001
CABG + mitral	−0.27	<0.0001
Heart transplant	1.64	<0.0001
Group × year interaction terms (reference group is CABG only)
Year × valve only	−0.02	<0.0001
Year × CABG + valve	−0.01	<0.0001
Year × CABG + mitral	−0.02	<0.0001
Year × heart transplant	0.04	<0.0001

Abbreviation: CABG = coronary artery bypass graft.

Figure 3.  A multivariable regression model comparing the rates of ARF among all groups to the reference CABG only group. The heart transplant group had a positive slope, indicating that the incidence of ARF in this group was rising faster than that in the CABG-only group. All other groups had negative slopes (see text for details). Abbreviations: ARF = acute renal failure, CABG = coronary artery bypass graft.

Elixhauser A, Steiner C, Harris DR, Coffey RM. Comorbidity measures for use with administrative data. Med Care. 1998;36:8–27.

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