الفهرس 
PATHOPHYSIOLOGY OF HYPOVOLEMIC SHOCKOnly 14 pages are availabe for public view
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Abstract
The recognition, assessment and management of hypovolemic shock still
remain an important task during initial trauma assessment. Recently, we have
questioned the validity of the Advanced Trauma Life Support (ATLS)
classification of hypovolemic shock by demonstrating that the suggested
combination of heart rate, systolic blood pressure and Glasgow Coma Scale
displays substantial deficits in reflecting clinical reality.
Some studies were done to introduce and validate a new classification of
hypovolemic shock based upon base deficit (BD) at emergency department
(ED) arrival showed that base deficit may be superior to the current ATLS
classification of hypovolemic shock in identifying the presence of
hypovolemic shock and in risk stratifying patients in need of early blood
product transfusion.
The American College of Surgeons has defined in its training program
Advanced Trauma Life Support (ATLS) four classes of hypovolemic shock.
This classification is based upon an estimated blood loss in percent
together with corresponding vital signs , For each class ATLS allocates
therapeutic recommendations (for example, the administration of intravenous
fluids and blood products) .
Recently, the clinical validity of the ATLS classification of hypovolemic
shock has been questioned by two analyses independently from each other on
two large-scale trauma databases: the TARN (Trauma Audit and Research
Network) registry and the Trauma Register DGU®, which had consisted of
more than 140,000 trauma patients , According to both analyses, ATLS seems
(a) to overestimate the degree of tachycardia associated with hypotension and
(b) to underestimate mental disability in the presence of hypovolemic shock
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These observations and conclusions prompted to develop an alternative
approach for the early assessment of hypovolemic shock in the emergency
department (ED). Several studies have already identified worsening base
deficit (BD) as an indicator for increased transfusion requirement
The base deficit is defined as the amount of base (in millimoles) needed
to titrate one liter of whole blood to a PH of 7.40 at temperature of 37c and
PCO2=40mm Hg, the normal range for base deficit is +2 to -2 mmol\L, in the
injured or bleeding patient an elevated base deficit is an indicator of global
tissue acidosis from impaired oxygenation .
BD has been associated with increased mortality, intensive care unit
(ICU) and in-hospital lengths of stay, and a higher incidence of shock-related
complications such as acute respiratory distress syndrome , renal failure,
hemocoagulative disorders, and multiorgan failure (MOF) .
A lot of trauma scoring systems such as EMTRAS , TASH score , BIG score
depends on BD as one of the parameters used to assess the condition of the
patient.
Monitoring of BD has also been suggested as an indicator and
monitoring parameter for the success of resuscitation efforts, However a lot of
objections arise now against considering BD the best end point of
resuscitation , as the body response to regenerate HCO3 after resuscitation is
relatively slow & there’s some medical interventions during resuscitation that
can influence the BD, the BD can be assessed in a fast and easy manner and
therefore is available within minutes after admission to the ED.