The sepsis syndrome - aspects of epidemiology, cost, and outcome in Aotearoa New Zealand

Abstract

The syndrome of sepsis is a life-threatening illness caused by a dysregulated host response to infection. Little is known about the epidemiology, optimal management or cost of sepsis in Aotearoa New Zealand. A series of studies were therefore conducted to investigate the local incidence, clinical features, and cost of sepsis. Findings were used to design and evaluate a whole-of-system quality-improvement programme.

Lower socio-economic status (Age Standardized Rate Ratio (ASRR) 1.72; 95% CI, 1.5-1.97)) comparing the highest with the lowest quintile of socioeconomic deprivation, and Māori ethnicity (ASRR 3.22 compared with non-Māori; 95% CI 2.85-3.65) are independently associated with incident sepsis. The incidence of sepsis may be increasing (ASRR 1.62 (95% CI 1.18-2.24) comparing 2012 with 2007 at Waikato District Health Board). In 2016, the median national cost of a sepsis-associated hospitalisation was $10,381 (interquartile range $6,093–$10,964).

Microbiological findings stratify mortality risk. Staphylococcus aureus bacteriuria in patients with Staphylococcus bacteraemia increases the risk of ICU admission (relative risk (RR) 2.5; 95% CI: 1.06-4.36; p=0.04) and in-hospital death (RR 2.18; 95% CI: 1.05-3.75; p=0.04). Compared with patients who do not grow a pathogen in blood, the recovery of Gram-negative organisms is associated with lower mortality despite high-risk clinical findings at presentation across a range of clinical infections (odds ratio (OR) for 30-day mortality 0.2, 95% CI 0.08-0.55, p<0.001).

In a cohort of hospitalised adults with and without sepsis, treatment escalation or death were associated with a respiratory rate >30 (adjusted hazard ratio (aHR) 5.97: 95% CI 2.11-16.91; p=0.001) and systolic blood pressure <80 mmHg (aHR 3.57: 95%CI 1.26-10.11; p=0.017). Building on these observations and using markers of critical illness to define high-risk cases, a whole-of-system sepsis quality improvement intervention was associated with reduced odds of in-hospital death (OR 0.83, 95% CI 0.7-0.98, p<0.05).

The sepsis syndrome in Aotearoa New Zealand is associated with poor clinical outcomes and high in-patient costs. Sepsis and the underlying infections which cause it disproportionately harm Māori people and those exposed to socio-economic deprivation. Short term outcomes are amenable to quality improvement efforts focused on early identification and management.