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Table 3 Cox proportional hazards regression (n = 160)

From: Varied flushing frequency and volume to prevent peripheral intravenous catheter failure: a pilot, factorial randomised controlled trial in adult medical-surgical hospital patients

  Univariable Multivariable
HR (95 % CI) HR (95 % CI)
10 mL volume (referent: 3 mL) 1.56 (0.97–2.50)* f
6 hr frequency (referent = 24 h) 1.58 (0.99–2.53)* f
Interaction of volume and frequencya 0.54 (0.21–1.42) f
Age (one year increase) 1.00 (0.99,1.02) f
Gender (female) 1.90 (1.18,3.05)*** 2.17 (1.33,3.55)***
Weight (over/obese) 1.29 (0.81,2.05) f
Comorbidities (one category higher)b 1.03 (0.78,1.35) f
Insertion on dominant side 1.67 (1.01,2.76)** f
Infection at baseline (any) 1.56 (0.93,2.59)* f
Antibiotics at baseline (yes) 0.99 (0.60,1.64) f
IV treatment at baseline (yes) 0.95 (0.43,2.07) f
Insertion at hand/posterior wristc 1.67 (1.04,2.70)** 1.66 (1.02,2.69)**
Insertion at forearma 0.58 (0.35,0.97)** e
Insertion at cub. fossa/ant. upper armc 1.01 (0.53,1.93) f
Inserted by IV servicec 0.95 (0.59,1.52) f
Inserted by nursec 2.01 (1.11,3.63)** f
Size (20 g versus 22 g) 1.14 (0.70,1.87) f
Vein quality (poor) 1.26 (0.79,2.01) f
Multiple insertion attempts (yes) 1.32 (0.78,2.23) f
Extension tubing (yes) 1.25 (0.78,1.98) f
3-way tap (yes) 1.33 (0.79,2.24) f
IV treatment at device removal (yes) 2.61 (1.28,5.29)*** e
IV treatment rate at device removald 1.40 (1.07,1.82)** e
IV antibiotics at device removal (yes) 2.07 (1.27,3.38)*** e
IV antibiotics rate at device removald 1.33 (1.09,1.62)*** e
Medication types administered:   
- antibioticsc 1.12 (0.67,1.87) f
- cephalosporinsc 0.80 (0.49,1.32) f
- penicillin combinationc 0.75 (0.40,1.41) f
Episode rate (medications and flushes) 1.22 (1.08,1.38)*** 1.25 (1.10,1.41)***
  1. HR hazard ratio, CI confidence interval, IV intravenous
  2. *p value <0.2; **p value <0.05; ***p value <0.01
  3. aModel for the interaction term results included the main effects
  4. bOrdinal: 0 = none/one, 1 = two/three, 2 = four or more
  5. cVersus all others
  6. dPer day, ordinal: 0 = none, 1 = one/two, 2 = three/four, 3 = five or more
  7. eExcluded due to correlation with other covariate
  8. fCovariate not entered into multivariate model (at p ≥ 0.2), or removed during model building at p > 0.05. Only variables p < 0.2 on univariable analysis entered into the multivariable model