Serum Lactate
Introduction
Broad Spectrum Antibiotics
The administration of early empirical antibiotics in the treatment of
severe sepsis and septic shock is proven to reduce mortality (Robson et
al, 2010). Yet it remains an underutilised therapy in the prehospital
environment. Indeed, recent research has revealed perhaps more can
be done prehospitally for septic patients with the measurement of
lactate levels in the blood providing paramedics with a definitive
marker for recognising and subsequently initiating treatment of severe
sepsis and septic shock (Jansen et al, 2008). This study investigates the
issues surrounding the use of broad spectrum antibiotics and lactate
measurement by paramedics in the QAS for the treatment of severe
sepsis and septic shock.
Research indicates that patients suffering septic shock, who
receive IV antibiotic treatment within the first hour of
onset of hypotension have a survival rate of 79.9%. Every
hour that antibiotic therapy is delayed results in a 7.6%
reduction in survival (Figure 1). The Surviving Sepsis
campaign, responsible for releasing a set of international
guidelines as to the treatment of sepsis, recommend IV
antibiotics be started as soon as possible and ‘always within the first hour of
recognising severe sepsis and septic shock’ (Dellinger et al, 2008). Paramedics, who
are often the first health care workers to treat these patients, are thus in a prime
position to administer that initial potentially lifesaving antibiotic therapy. Moreover,
it is recommended that the initial antibiotic therapy be broad spectrum in order to
ensure all likely pathogens are targeted with more specific antibiotic therapy
initiated once the causative agent has been identified (Dellinger et al, 2008).
Ceftriaxone, already carried by QAS paramedics, is a broad spectrum antibiotic that
has been shown to be an effective empirical antibiotic treatment for severe sepsis
and is currently used as such by Ambulance Victoria (Roberts et al, 2007).
Current Practice
Currently, Queensland paramedics are only able to treat septic shock
symptomatically through the use of treatments such as oxygen,
paracetamol and fluid therapy (QAS, 2001). Although recent changes
allowing ICPs to administer 20mcg to 50mcg aliquots of adrenaline to
patients displaying signs of shock are a step in the right direction, there
is still more that can be done for these patients (QAS, 2010).
Paramedics working for Ambulance Victoria have more clearly defined
guidelines to follow affording them the option of administering
ceftriaxone on consult in cases of septic shock (Ambulance Victoria,
2005).
Epidemiology
Worldwide 13 million people become septic each year with mortality
rates for severe sepsis of 30% to 50% and septic shock greater than
50% (Daniels & Nutbeam, 2010). In Australia the mortality rate is
lower at 27.6%, however the number of septic patients admitted to
ICU’s over the last decade has steadily increased (Cameron et al, 2009).
Controversies
One of the main arguments against empirical antibiotic therapy is the
potential of creating antibiotic resistance in bacteria. After decades of
decline, the danger from infectious disease is now on the rise due in part to
the indiscriminate use of broad-spectrum antibiotics which has led to the
development of resistant strains among pathogenic bacteria (Tsiotou &
Sakorafas, 2004). Widespread use of certain antibiotics, particularly thirdgeneration cephalosporins, has been shown to foster development of
generalized b-lactam resistance in previously susceptible bacterial populations
(Yates, 1999) . The argument therefore, is that antibiotics should only be used
after a treatable infection has been recognised, or if there is a high degree of
suspicion of infection.
Recommendations
What is Septic Shock?
The Surviving Sepsis Campaign defines sepsis as a localised
infection with systemic manifestations whilst severe sepsis is
characterised as sepsis with associated organ dysfunction and/or
tissue hypoperfusion (Dellinger et al, 2008). Septic shock is classed
as severe sepsis plus hypotension that persists despite fluid
resuscitation (Dellinger et al, 2008).
Pathophysiology
Representation of Patient Mortality After Anti-biotic
Administration
It has been definitively proven that early empirical administration of broad
spectrum IV antibiotics in cases of severe sepsis and septic shock reduces
mortality (Ferrer et al, 2009). Paramedics, as the first physicians to treat such
patients are thus in a prime position to initiate treatment and therefore have a
significant impact on the outcome of these critically ill patients. The
development of resistance by bacteria to antibiotics is an important
consideration, however, is it ethical to withhold potentially lifesaving treatment
from a patient based on such a possibility? The introduction of lactate
measurement in the prehospital setting may allow paramedics to more
definitively diagnose septic patients and therefore administer antibiotics with
more discretion. Hence the current literature would suggest investigation by
the QAS into its treatment protocol surrounding septic shock, in particular the
empirical administration of ceftriaxone and serum lactate measurement, is
warranted.
90%
References
80%
70%
Survival Rate (%)
Toxins produced by invading bacteria initiate the inflammatory cascade
resulting in peripheral vasodilation and increased vascular permeability
causing oedema (Huether & McCance, 2008). Early in the progression
of the disease, cardiac output (CO) and heart rate are increased to
compensate for the widespread vasodilation however, as the disease
worsens, myocardial contractility is depressed, through the actions of
inflammatory mediators, causing CO to fall (Huether & McCance,
2008). Venous return is reduced which in turn further reduces CO
exacerbating the state of hypoperfusion (Huether & McCance, 2008).
Widespread hypoxia precipitates a shift from aerobic to anaerobic
metabolism resulting in a build up of lactate in the blood (Cameron et
al, 2009). Endothelial permeability as well as hypoxia extends to organ
systems causing malfunction then ultimately failure and death without
intervention (Beers et al, 2006).
One of the challenges facing paramedics is the recognition and
diagnosis of sepsis. In the out of hospital environment it is
often difficult to determine until the patient deteriorates into
septic shock. However the measurement of serum lactate has
been found to aid in the definitive diagnosis of severe sepsis
(Shapiro et al, 2009). Similar to testing a patient’s BSL, lactate
levels in the blood enable the clinician to accurately determine .
the presence of sepsis as lactate levels will rise to above 3.5 to 4mmol/L prior
to the onset of hypotension (Jansen et al, 2008) . If empirical antibiotic
therapy is initiated in response to the increase in lactate levels, as opposed to
waiting for the onset of hypotension, it results in an increase in survival
(Dellinger et al, 2008).
60%
50%
40%
Patients
30%
20%
10%
0%
<1
2
3
4
5
6
7
Administration (Hours)
Figure 1 – Information based on research by Kumar et al, (2006).
8
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