Early Postoperative Hypoalbuminaemia as a Risk Factor for Postoperative Pneumonia Following Hip Fracture Surgery

Figures & data

Figure 1 Flowchart illustrating the selection of the patients for this study.

Table 1 Univariate and Multivariate Regression Analyses of Risk Factors for Postoperative Pneumonia

Variables	Univariate			Multivariate
	Pneumonia (n=59)	Non-pneumonia (n=1096)	P-value	OR	95% CI	P-value
Demographic characteristics
Sex (male/female)	21 (35.6)/38 (64.4)	295 (26.9)/801 (73.1)	0.145
Age (years)	83.08 ± 7.30	77.90 ± 10.05	<0.001	1.062	(1.022, 1.103)	0.002
BMI (kg/m^2)	22.32 ± 3.43	22.57 ± 3.63	0.673
Period between injury and operation date (days)	3.92 ± 4.39	3.72 ± 3.14	0.643
HTN	46 (78.0)	748 (68.2)	0.117
DM	21 (35.6)	388 (35.4)	0.976
COPD	4 (6.8)	54 (4.9)	0.526
CKD	10 (16.9)	140 (12.8)	0.353
Cardiovascular disease	17 (28.8)	170 (15.5)	0.007	2.03	(1.118, 3.688)	0.02
Cerebrovascular disease	11 (18.6)	230 (21.0)	0.666
Medication history
Antiplatelets	20 (33.9)	371 (33.9)	0.994
Anticoagulants	6 (10.2)	66 (6.0)	0.199
Type of surgery			0.385
Osteosynthesis	33 (55.9)	675 (61.6)
Arthroplasty	26 (44.1)	421 (38.4)
Laboratory findings
Preoperative Hb (g/dL)	11.62 ± 1.57	11.59 ± 1.60	0.856
Preoperative Hct (%)	34.90 ± 4.69	34.67 ± 4.69	0.721
Preoperative Plt (×10^9/L)	216.31 ± 98.02	204.57 ± 73.31	0.369
Preoperative Cr (mg/dL)	0.96 ± 0.32	0.96 ± 0.77	0.953
Albumin (g/dL)
Preoperative	3.59 ± 0.45	3.71 ± 0.43	0.04	1.012	(0.514, 1.994)	0.972
<3.0 during the first two postoperative days	45 (76.3)	557 (50.8)	<0.001	2.428	(1.261, 4.676)	0.008
EBL during the first postoperative week (mL)	941.96 ± 434.69	893.41 ± 373.88	0.336
Minimum Hb during the first postoperative week (g/dL)	8.63 ± 1.18	8.54 ± 1.21	0.611
Volume of fluid administered intraoperatively (mL)	701.69 ± 409.79	614.69 ± 420.60	0.121
Anaesthesia time (minutes)	121.44 ± 31.12	121.00 ± 34.20	0.924
Length of stay (days)	17.25 ± 9.93	15.77 ± 11.18	0.319
Postoperative transfusion rate (%)	3 (5.1)	73 (6.7)	0.634

Note: Data are presented as mean ± standard deviation or number (%)

Abbreviations: OR, odds ratio; CI, confidence interval; BMI, body mass index; HTN, hypertension; DM, diabetes mellitus; COPD, chronic obstructive pulmonary disease; CKD, chronic kidney disease; Hb, haemoglobin; Hct, haematocrit; Plt, platelet count; Cr, creatinine; EBL, estimated blood loss.

Table 2 Demographic and Perioperative Characteristics of Patients According to Minimum Serum Albumin Level During the First Two Postoperative Days

Variable	Total (N=1155)	Minimum Albumin During the First Two Postoperative Days (g/dL)		P-value	Standardised Difference
		<3.0 (n=602)	≥3.0 (n=553)
Demographic characteristics
Sex (male/female)	316 (27.4)/839 (72.6)	129 (21.4)/473 (78.6)	187 (33.8)/336 (66.2)	<0.001	0.631
Age (years)	78.16 ± 9.99	80.77 ± 7.99	75.33 ± 11.13	<0.001	0.058
BMI (kg/m^2)	22.73 ± 18.95	22.55 ± 24.44	22.93 ± 10.02	0.740	0.001
Period between injury and operation date (days)	3.73 ± 3.22	3.83 ± 3.07	3.61 ± 3.37	0.259	0.021
HTN	794 (68.7)	418 (69.4)	376 (68.0)	0.597	0.067
DM	409 (35.4)	205 (34.1)	204 (36.9)	0.314	0.124
COPD	58 (5.0)	36 (6.0)	22 (4.0)	0.120	0.423
CKD	150 (13.0)	84 (14.0)	66 (11.9)	0.308	0.179
Cardiovascular disease	187 (16.2)	99 (16.4)	88 (15.9)	0.806	0.039
Cerebrovascular disease	241 (20.9)	139 (23.1)	102 (18.4)	0.052	0.283
Medication history
Antiplatelets	391 (33.9)	210 (34.9)	181 (32.7)	0.440	0.096
Anticoagulants	72 (6.2)	43 (7.1)	29 (5.2)	0.182	0.326
Type of surgery				0.544	0.073
Osteosynthesis	708 (61.3)	364 (60.5)	344 (62.2)
Arthroplasty	447 (38.7)	238 (39.5)	209 (37.8)
Laboratory findings
Preoperative Hb (g/dL)	11.59 ± 1.60	11.22 ± 1.52	11.99 ± 1.59	<0.001	0.317
Preoperative Hct (%)	34.68 ± 4.69	33.67 ± 4.48	35.78 ± 4.67	<0.001	0.101
Preoperative Plt (×10^9/L)	205.17 ± 74.76	206.64 ± 79.61	203.57 ± 69.15	0.483	0.001
Preoperative Cr (mg/dL)	0.96 ± 0.75	0.93 ± 0.57	1.00 ± 00.91	0.150	0.112
Preoperative albumin (g/dL)	3.70 ± 0.43	3.54 ± 0.42	3.88 ± 0.38	<0.001	2.135
EBL during the first postoperative week (mL)	895.89 ± 377.16	894.13 ± 376.81	897.81 ± 377.88	0.868	<0.001
Minimum Hb during the first postoperative week (g/dL)	8.55 ± 1.20	8.18 ± 1.03	8.96 ± 1.25	<0.001	0.594
Volume of fluid administered intraoperatively (mL)	619.14 ± 420.31	632.24 ± 425.97	604.88 ± 413.98	0.269	<0.001
Anaesthesia time (minutes)	121.03 ± 34.04	122.44 ± 36.96	119.48 ± 30.51	0.137	0.003
Length of stay (days)	15.85 ± 11.12	16.31 ± 9.41	15.35 ± 12.72	0.146	0.008
Postoperative transfusion rate (%)	76 (6.6)	55 (9.1)	21 (3.8)	<0.001	0.892

Note: Data are presented as mean ± standard deviation or number (%)

Abbreviations: BMI, body mass index; HTN, hypertension; DM, diabetes mellitus; COPD, chronic obstructive pulmonary disease; CKD, chronic kidney disease; Hb, haemoglobin; Hct, haematocrit; Plt, platelet count; Cr, creatinine; EBL, estimated blood loss.

Table 3 Comparison of the Incidence of Pneumonia According to Minimum Serum Albumin Level During the First Two Postoperative Days

Outcome	Minimum Albumin During the First Two Postoperative Days (g/dL)	Crude			IPTW*		PSM*
		Event/N	OR (95% CI)	P-value	OR (95% CI)	P-value	Event/N	OR (95% CI)	P-value
Pneumonia	<3.0	45/602	3.110 (1.688, 5.732)	<0.001^a	3.053 (1.958, 4.760)	<0.001^b	19/223	3.111 (1.237, 7.825)	0.016^c
	≥3.0	14/553					7/223

Notes: *The propensity score was calculated using a multiple logistic regression model that included all variables presented in Table 1 excluding postoperative transfusion rate, length of stay, estimated blood loss, and minimum Hb during the first postoperative week. ^ap-value by simple logistic regression. ^bp-value by weighted logistic regression. ^cp-value by conditional logistic regression

Abbreviations: IPTW, inverse probability of treatment weighting; PSM, propensity score matching