Medical background
Medical background
State of the artDifficulty of diagnosis
The circulatory shocks is a diagnostic and therapeutic emergency whose delay in treatment causes excess mortality. The state of shock is defined as : a failure of the circulatory system, resulting in a mismatch between the intake and the peripheral oxygen requirements. The quick identification of the mechanisms involved, the etiology of the state of shock and its severity, allows for optimal therapeutic care of patients.
In practice, the main mechanism distinguishes four major categories of state of shock : cardiogenic shock, hypovolemic shock, distributive shock, and obstructive shock.
The acute circulatory failure is characterized by an arterial hypotension, namely systolic blood pressure (SBP) less than 90 mmHg or mean arterial pressure (MAP) less than 65 mmHg.
Shock is typically associated with evidence of inadequate tissue perfusion on physical examination. The three organs readily accessible to clinical assessment of tissue perfusion are :
- skin (degree of cutaneous perfusion: CRT, mottling, skin temperature) ;
- kidneys (urine output) ;
- brain (mental status).
Many additional examinations are available when treating a patient in shock to evaluate tissue perfusion quantitatively.
These examinations make it possible to evaluate the impact of the state of shock and its severity.
The most frequently performed exam (although sometimes difficult to interpret, and with a delay of about 30 minutes) is the lactate assay.
Repetition of the lactate assay during the therapeutic management of a patient in a state of circulatory shock allows the evaluation of the effectiveness of the therapies used
Resucitation based on tissue perfusion tends to be more efficient on survival in patients with circulatory failure.
Clinicians, paediatricians, emergency physicians, resuscitators, mobile rescuer do not have proven solutions available that are simple to implement at a patient's bedside.
Bioelectrical impedance, videomicroscopy, Laser Doppler flowmetry, thermoconductivity, PcO2, plethysmography, IR thermography, prove either too difficult to implement, or uncalibrated, or invasive or with no proven utility.