Direct and Indirect Blood Pressure: Indications and Methods - Nuts and Bolts

INTRODUCTION

Arterial blood pressure (ABP) is the lateral force or pressure exerted by the blood on the arterial vessel wall. Although the term ABP is used, in reality there is a systolic arterial pressure (SAP), a diastolic arterial pressure (DAP) and a mean arterial pressure (MAP). Its values vary accordingly to the measurement technique, studied population and animal handling 1 . Natural factors which are known to influence ABP include breed (in dogs), sex, age (cats), obesity (dogs), anxiety and circadian variation (possible in dogs).

WHY SHOULD WE MEASURE ABP IN EMERGENCY AND CRITICAL CARE?

In ECC there are many reasons that justify measuring ABP including:

• ABP is one of the most important endpoints of resuscitation, because MAP is the critical determinant of tissue perfusion.
• Animals with several types of emergencies are hypotensive. Common examples include several types of shock, but also hypothermia, endocrinopathies, CNS diseases and intoxications.
• Vital organs such as the heart and the brain maintain tissue perfusion due to autoregulation of blood flow. When MAP is below 60 mmHg or above 150 mmHg, the autoregulation fails and organ perfusion will depend directly from the MAP.
• Several disease states are accompanied by high ABP. These include kidney failure and endocrinopathies, such as Cushings´s disease and pheocromocytoma. High ABP in these circumstances can also contribute to the progression of the disease, especially in kidney disease.
• Increased ABP itself is associated to severe pathological consequences including neurological, ophthalmological, cardiac and renal. Damage that results from the presence 1 of a sustained high ABP is referred as target-organ damage (TOD) .
• Many emergency and critical care interventions have a direct effect in ABP. These include for example mechanical ventilation, continuous renal replacement techniques peritoneal dialysis and all involving anesthesia and surgery. The same reasoning also applies to several medications (e.g. sedatives) and fluids (e.g. fresh whole blood, artificial colloids) administered in the critical care environment.  […]