Prognostic value of lactate in out-of-hospital cardiac arrest: a prospective cohort study
Karl Charlton (Corresponding Author), Research Paramedic, North East Ambulance Service NHS Foundation Trust, Newcastle upon Tyne, UK; Hayley Stagg, Statistician, North East Ambulance Service NHS Foundation Trust, Newcastle upon Tyne, UK. Email: firstname.lastname@example.org
Background: The prognostic role of lactate in out-of-hospital cardiac arrest (OHCA) remains unclear. Aims: To explore serum lactate as a predictor of return of spontaneous circulation in patients experiencing OHCA after arrival at hospital. Methods: This 13-month prospective observational cohort study involved patients aged ≥18 years. Serum lactate levels were measured during cardiopulmonary resuscitation before ROSC. Patients were divided into two groups by lactate level: Group 1, low (≤9.9 mmol/l) and Group 2, high (≥10 mmol/l). Findings: 105 patients were included, 50 in group 1 and 55 group 2. Median lactate were 7.4 mmol/l and 14.2 mmol/l respectively. More patients in group 1 were found with ventricular fibrillation (40% versus 14.5%; P≤0.01), obtained ROSC more quickly (37 minutes 38 seconds versus 39 minutes 13 seconds; P=0.79) and achieved short-term survival (survived >24 hours) (40% versus 23.5%; P=0.32), versus group 2; prediction of survival did not reach statistical significance. Conclusion: Lower lactate levels in OHCA appear to be associated with better short-term outcomes but the cut-off points regarding survival remain unclear. Key words l Hyperlactataemia l Out-of-hospital cardiac arrest l Paramedic l Cardiopulmonary resuscitation l Prehospital emergency care
Accepted for publication:24 January 2022
Out-of-hospital cardiac arrest (OHCA) is a major public health concern in industrialised countries, with high mortality rates (Zhou et al, 2018). UK emergency medical services treat 30 000 OHCAs annually (Perkins and Brace-McDonnell, 2015) but the survival rate remains persistently low. Highquality cardiopulmonary resuscitation (CPR) and early defibrillation, where indicated, are essential to achieve optimal outcomes (Deakin et al, 2010).
Sudden OHCA results in cessation of cardiac function with haemodynamic collapse leading to anaerobic metabolism (Dadeh and Nuanjaroan, 2018). In anaerobic conditions, tissue hypoxia leads to an accumulation of lactate (Mizock and Falk, 1992).
Patients who have had an OHCA are hypoxic, hypoperfused and experience hyperlactataemia, most likely caused by ischaemia and inflammation resulting from ischaemia-reperfusion injury (Donnino et al, 2007; Cocchi et al, 2011), which is a surrogate marker for hypoxic insult (Orban et al, 2017).
During OHCA, lactate concentrations increase with duration of down time (Carden et al, 1985), and are influenced by quality of bystander CPR (BCPR) and initial rhythm (Zhou et al, 2018), which are known to influence survival.
Current guidelines recommend the measurement of lactate in patients after cardiac arrest to guide therapy, although the International Liaison Committee on Resuscitation recognises a knowledge deficit in the evidence supporting this guideline (Nolan et al, 2008).
Several observational studies suggest hyperlactataemia is prognostic of mortality in patients with cardiac arrest, but comparisons are difficult as research has focused mainly on OHCA patients who achieved return of spontaneous circulation (ROSC) (Nishioka et al, 2021) and involved varying outcome measures and populations of interest (Kleigel et al, 2004; Williams et al, 2016).
The PREDICT study explored serum lactate levels as a predictor of ROSC in patients who experienced OHCA after arrival at hospital (Charlton and Moore, 2021).
Vol 14 No 4 • Journal of Paramedic Practice