The initiation of fluid resuscitation in a pre-hospital setting by paramedics in the United Kingdom has been an ongoing practice for over 20 years. At the inception of paramedic practice, such practitioners were able to administer both colloids and crystalloid fluids for resuscitation purposes. However, over the past decade paramedic practice has been dictated by national clinical guidelines, namely that from the Joint Royal Colleges Ambulance Liason Committee (JRCALC) (2006), and fluid resuscitation restricted to crystalloid administration only.
It has become commonplace for paramedics to gain intravascular access and infuse crystalloid fluids in trauma patients, while using other noninvasive patient assessment techniques and incorporating management strategies from the aforementioned clinical guidelines. Thus JRCALC (2006) suggests that when there is visible external blood loss of over 500 ml, fluid replacement must be commenced with an initial bolus of 250 ml through a large bore cannula.
Conversely, there exists an expanding body of literature and research on the utilisation of permissive hypotensive resuscitation, with the drivers for such research stemming from recent military conflicts in Iraq and Afghanistan. Such research tends to highlight that limiting volume replacement can negate the often lethal triad seen in trauma patients, namely acute coagulopathy, metabolic acidosis, and hypothermia.
As a consequence, this review will critically appraise the use of permissive hypotensive resuscitation on patients suffering from trauma-related injuries, identifying whether such treatment modalities could be implemented to the wider UK pre-hospital arena and paramedic practice. Further to this, it will evaluate the effectiveness of such interventions with the aim of assessing the consistency and validity of such research.
Hypotensive resuscitation
Jackson and Nolan (2009) note that although the understanding of hypotensive resuscitation as described in the literature is clear, there are a number of discrepancies with regards to how much of which fluid to which endpoint. They believe this is because this information has not been defined precisely.
Geoghegan et al (2010) suggest that ‘hypotensive resuscitation in the trauma setting can be defined as deliberately allowing blood pressure to remain below normal until any active bleeding has been controlled.’
Stahel et al (2009) states that trauma is the primary cause of death for young individuals in industrialised countries, with 40% of deaths being attributed to haemorrhage, even though numerous advances have been made in the delivery of trauma care. In the UK, pre-hospital trauma care is delivered by paramedics and ambulance technicians. Paramedics have the ability to perform a number of invasive techniques, notwithstanding intravenous cannulation, and the administration of drugs and intravenous fluids, namely crystalloids, in the form of Ringer’s Lactate or sodium chloride. In the adult trauma patient the maximum cumulative dose of intravenous fluid is two litres; however, this is titrated in boluses of 250 ml.
Using national guidelines
The management techniques outlined are driven by national guidelines, including JRCALC (2006) and the National Institute for Health and Clinical Excellence (NICE) (2004) guideline on pre-hospital fluid replacement therapy in trauma.
While JRCALC (2006) does not make reference to hypotensive resuscitation per se, a cursory comment acknowledges that the cavalier use of intravenous fluids can be detrimental to the overall patient outcome. The guideline claims that current research shows:
‘Little evidence to support the routine use of IV fluids in adult trauma patients. In circumstances such as penetrating chest and abdominal trauma, survival worsens with the routine use of IV fluids.’
Such a perfunctory comment can be criticised due to the fact the authors use research that was undertaken 10 years before the publication of the clinical guidelines. Such tokenism fails to acknowledge the numerous animal and human studies that had generated such clinical debate for over a decade in relation to hypotensive resuscitation.
In contrast, NICE (2004) uses several randomised controlled trials to underpin the current guidelines relating to fluid administration in the pre-hospital setting. It is acknowledged that the administration of intravenous fluids in the pre-hospital setting can be advantageous and that such administration can improve tissue and organ perfusion culminating in reduced mortality rates; however, this is counterbalanced by the normalisation of blood pressure, leading to the increased likelihood of further haemorrhage. Furthermore, NICE (2004) suggests that delaying fluid administration in turn decreases time at the scene. The author suggests that such assumptions in today’s pre-hospital arena lack any credibility; however, the author does concede there is little in the way of evidence to refute such a statement with the scope of this work not permitting further research to substantiate or refute such claims. Having said this, it is customary that delays at the scene are often not due to invasive procedures but a multitude of confounding variables, such as extrication and a lack of resources, namely ambulances to convey patients.
In summary, NICE (2004) is able to speculate that of the several randomised controlled trials systematically reviewed, insufficient evidence exists to draw definitive conclusions on the benefit of pre-hospital fluid administration and/or hypotensive fluid resuscitation. Moreover, NICE (2004) identifies two studies that conclude hypotensive resuscitation strategies lead to higher mortality rates in trauma victims.
Alternative research
Historically, Mackinnon (2005) concludes that the use of pre-hospital fluid resuscitation has been driven by the want to normalise numbers, specifically blood pressure and heart rate, regardless of physiological evidence to the contrary. Moreover, the use of fluid resuscitation has been the fundamental remedy to haemorrhagic shock with the logical assumption that if a pre-hospital care provider can increase intravascular volume and preload along with perfusion pressure, such patients will remain stable until surgery and definitive repair is achieved. Such presupposition stems from animal studies conducted during the 1950s and 1960s, whereby experimenters were able to demonstrate positive outcomes using fluid resuscitation models.
‘A fundamental shift in thinking towards fluid resuscitation has occurred in the past decade’
Mackinnon (2005) argues that if normalization of blood pressure is to occur and oxygen delivery is to be maintained, the use of fluid resuscitation is therefore the key, although it is the conjecture that such use will potentially dislodge thrombus formation, increase bleeding time, and more importantly, haemodilute existing haemoglobin, platelet and coagulation factors. As a result, Mackinnon (2005) suggests that a fundamental shift in thinking towards fluid resuscitation has occurred in the past decade, leading to a dichotomy of views regarding the use of fluid resuscitation and the use of hypotensive resuscitation strategies.
Nolan (2001), although an advocate of controlled fluid resuscitation not hypotensive resuscitation, speculates that common vital signs, such as heart rate, respiratory rate and blood pressure, are poor indicators of hypovolaemia, citing two recent studies whereby volunteers underwent haemorrhage of between 20% and 30%, and showed no significant increase in heart rate or rise/fall of blood pressure. As a consequence, in a systematic review of hypotensive resuscitation Nolan (2001) identifies a number of methodological weaknesses in studies that advocate the use of such strategies and seem to suggest that hypotensive resuscitation and its adoption can improve survival of trauma patients.
‘Even with brief periods of hypotension the clinical outcome is much worse in those patients with traumatic brain injury’
Conversely, Mackinnon (2004) identifies that the use of permissive hypotensive strategies is commonplace during the management of leaking aortic aneurysms. It has become common practice to manage such patients with a systolic blood pressure of between 70 and 85 mm Hg until an operative repair can be undertaken, whereas in those patients who were previously managed by adhering to normal systolic blood pressure are found to repeatedly bleed. Mackinnon (2004) further cites Bickel et al (1994), who were able to show that patients suffering from penetrating torso trauma showed a 70% survival rate for delayed fluid resuscitation, compared to 62% survival in those patients receiving aggressive fluid resuscitation.
Søreide et al (2005) systematically reviewed the study and conclusions drawn by Bickel et al (2004) and found that the claim of reduced mortality in 8% of patients receiving hypotensive resuscitation was strictly limited in patients with cardiac injuries, and failed to highlight that during the study, travel times to definitive care were short and the population of the study were predominately young.
Stahel et al (2009) identify that permissive hypotension has become a standard concept in the management of combat casualties in Iraq, but in their critique find such a management protocol has many limitations. These are often found in the polytrauma patient, especially when prolonged hypotension can aggravate post injury coagulopathy and increase the likelihood of secondary insults in patients with severe brain injuries. Søreide (2005) concurs with Stahel et al (2009) and identifies that patients with a severe traumatic brain injury, commonly defined as presenting with a Glasgow coma scale score of less than nine, do not tolerate even brief periods of hypotension. It is further suggested that even with brief periods of hypotension the clinical outcome is much worse in those patients with traumatic brain injury. In patients with a traumatic brain injury, a systolic blood pressure of around 100 mm Hg is needed to ensure cerebral perfusion. In contrast, Berry (2008) stipulates that permissive hypotension aims to maintain a systolic blood pressure of around 90 mm Hg, which would, in the brain injured patient, cause untold long–term cerebral damage.
Conclusions
It is apparent that current research is well-defined and able to demonstrate that excessive fluid resuscitation can have a wide range of detrimental effects on homeostasis of patients presenting with trauma. Similarly, the implementation of permissive hypotension seems to have similar negative outcomes, especially in the polytrauma or traumatic brain injured patient. Research fails to prove equivocally that permissive hypotension in the trauma patient would improve survival or clinical outcome.
It seems that pre-hospital providers would benefit from education as to the negative effects of excessive fluid administration. Clinical intervention should be made on an individual basis and dependent on the presenting condition, whether this be traumatic brain injury, blunt or penetrating trauma.
It is suggested that the implementation of permissive hypotensive resuscitation strategies into the UK pre-hospital arena lacks the underpinning high-quality evidence of randomised controlled human trials, even though at first glance evidence does seem compelling. Management of the trauma patient needs to follow current trends in damage control resuscitation rather than permissive hypotension, with further research undertaken into choice of fluids used when resuscitating the trauma patient.
As Søreide et al (2005) eloquently state:
‘Venous access and fluid therapy should still be considered to be essential elements of pre-hospital advanced life support in the critically ill patient. Initiation of fluid therapy should be based on clinical assessment…’
Paramedics should be encouraged to undertake a critical review of any guidance issued in order to ensure that they are fit for purpose. Emerging JRCALC guidelines may provide the paramedic with further guidance, and this too must be critically reviewed by practitioners.