Factors affecting the duration of intravenous antibiotic therapy for cellulitis in an outpatient setting

Abstract number: P1520

Lillie P., Darton T., Andrews D., Eaves K., Chapman A.

Objectives: Cellulitis is a common community acquired infection that is increasingly treated with IV antibiotics in an outpatient setting. We analysed patients under the care of our outpatient IV antibiotic service for cellulitis to ascertain factors affecting duration of therapy.

Methods: A retrospective review of cases of cellulitis managed by the outpatient IV antibiotic service at our institution between 1st October 2007 and 30th September 2008. Demographic, clinical, laboratory and outcome data were collected. Cases were split into short course therapy (3 days) or extended course (7 days). Factors associated with increased duration on univariate analysis were then entered into a multivariate regression analysis. P values <0.05 were considered significant.

Results: 98 cases were available for review. 61.2% were male, the mean age was 54.6 years and the mean duration of therapy was 6 days. 28 cases had 3 days therapy, 32 had 4–6 days and 38 had 7 days. On univariate analysis (table 1) extended course treatment was associated with higher baseline CRP, ESR, creatinine, longer duration of cellulitis pre outpatient IV antibiotics, lower haemoglobin, increasing age, presence of diabetes and male sex. In the multivariate model, male sex (P < 0.001), increasing age (P = 0.038) haemoglobin (P < 0.001) and CRP (P = 0.001) remained predictive of an extended course.

Conclusion: An extended course of IV therapy for cellulitis in an outpatient setting is associated with male sex, increased age, low baseline haemoglobin and high baseline CRP. These factors may be useful to guide frequency of medical review of patients in this setting and may also help with decisions about the nature of intravenous access for antibiotics.

Table 1. Univariate factors affecting duration of treatment

	3 day, n = 28 (%)	7 days, n = 38 (%)	P value
Diabetes	0 (0)	8 (21.1)	0.0169
Male gender	13 (46.4)	31 (81.6)	0.0038
CRP (mg/L)	31.2	84.6	0.002
ESR (mm/hr)	20.4	46.8	<0.001
Creatinine (mmol/dl)	77.2	89.6	0.0423
Albumin (g/L)	37.4	32.2	<0.001
Haemoglobin (g/dl)	14.3	13.5	0.0423
Duration of symptoms pre treatment (days)	5.0	9.3	0.014
Age (years)	48.4	62.1	0.0013