Impact of Enhanced in-Hospital Infection Prevention During the COVID-19 Pandemic on Postoperative Pneumonia in Older Surgical Patients

Figures & data

Figure 1 The number of patients treated monthly for all types of pneumonia in South Korea.

Table 1 Baseline Characteristics Before and During the COVID-19 Pandemic

	Before COVID-19 (N=14,647)		During COVID-19 (N=10,547)		ASD
	n	Mean ± SD or (%)	n	Mean ± SD or (%)
Age (years)	14,647	75.6 ±4.5	10,547	75.9 ±4.6	0.06
Female	6872	(46.9)	4955	(47.0)	0.00
Body mass index (kg/m^2)	14,492	24.5 ±3.2	10,427	24.6 ±3.2	0.04
Smoker	579	(4.0)	366	(3.5)	0.03
ASA physical status					0.32
1	1695	(11.6)	365	(3.5)
2	10,237	(69.9)	7844	(74.4)
3	2603	(17.8)	2243	(21.3)
4	112	(0.8)	95	(0.9)
Preoperative SpO2 (%)	14,647	96.6 ±2.6	10,547	97.1 ±2.4	0.17
Hemoglobin (g/dl)	14,647	12.7 ±1.5	10,547	12.8 ±1.6	0.02
Surgical incision					0.01
Peripheral	6165	(42.1)	4438	(42.1)
Upper abdominal	6802	(46.4)	4924	(46.7)
Intrathoracic	1680	(11.5)	1185	(11.2)
Type of anesthesia					0.02
General	12,519	(85.5)	9083	(86.1)
Spinal	2128	(14.5)	1464	(13.8)
Duration of surgery (hours)	14,647	2.1 ±1.7	10,547	2.0 ±1.7	0.04
Duration of anesthesia (hours)	14,647	3.0 ±2.0	10,547	2.8 ±1.8	0.09
Intraoperative transfusion	1030	(7.0)	696	(6.6)	0.02
Postoperative ICU stay	2209	(15.1)	1195	(11.3)	0.11
Postoperative length of hospital stay (days)	14,647	7.2 ±22.9	10,547	6.4 ±10.9	0.05
Postoperative mechanical ventilation within 24 hours	800	(5.5)	481	(5.0)	0.02
ARISCAT score	14,647	25.4 ±16.4	10,547	24.6 ±16.1	0.05
ARISCAT risk					0.06
Low	7150	(48.8)	5417	(51.4)
Intermediate	5562	(38.0)	3903	(37.0)
High	1935	(13.2)	1227	(11.6)

Abbreviations: ASA, American Society of Anesthesiologists; SpO₂, oxygen saturation measured by pulse oximetry; ICU, intensive care unit; ARISCAT, Assess Respiratory Risk in Surgical Patients in Catalonia; ASD, absolute standardized mean difference; SD, standard deviation.

Figure 2 Flowchart of the study. ARISCAT: Assess Respiratory Risk in Surgical Patients in Catalonia.

Figure 3 The number of monthly postoperative pneumonia cases per 1000 patients. The blue solid line represents the expected number of pneumonia and the red dashed line indicates the de-seasonalized expected number of pneumonia cases in model 0.

Table 2 Interrupted Time Series Analysis for the Monthly Incidence Rate of Postoperative Pneumonia

	Model 0: Before Covariate Adjustment	Model 1: After Adjustment of Monthly ARISCAT Score Median	Model 2: After Adjustment of Monthly Proportion of Patients with ARISCAT Low Risk
	β-Coefficient [95% CI]	β-Coefficient [95% CI]	β-Coefficient [95% CI]
Slope before COVID-19 period	−0.007 [−0.022, 0.007]	−0.008 [−0.022, 0.007]	−0.009 [−0.023, 0.006]
Intercept change during COVID-19 period	−0.012 [−0.442, 0.417]	−0.012 [−0.446, 0.422]	−0.022 [−0.462, 0.417]
Slope change during COVID-19 period	−0.007 [−0.029, 0.015]	−0.005 [−0.031, 0.022]	0.001 [−0.028, 0.030]
Monthly median of ARISCAT score		0.007 [−0.021, 0.034]
Monthly ARISCAT low risk proportion			−0.019 [−0.055, 0.016]

Abbreviations: ARISCAT, Assess Respiratory Risk in Surgical Patients in Catalonia; CI, confidence interval.