Monitoring of intra-abdominal pressure (IAP) in the intensive care unit

Measurement of intra-abdominal pressure (IAP) is one of the parameters that are routinely performed in intensive care units, such as central venous pressure, heart rate, invasive and non-invasive blood pressure monutoring, etc. 

It is a constant indicative of the pressure inside the abdominal cavity, with normal values ​​in  adults ranging between 5 and 7 mmHg, and it rises according to certain physiological conditions such as obesity, pregnancy, etc. 

It is evident that its monitoring helps to reduce morbidity and mortality of these patients due to the direct relationship between intra-abdominal pressure (IAP), Intra-abdominal Hypertension (IAH) and Abdominal Compartment Syndrome (ACS). 


High values of (IAP) ​​can produce pathophysiological alterations related to the reduction of capillary perfusion at different levels resulting in dysfunction of vital organs.

Risk factors influencing IAH / ACS development:

Pancreatitis
Peritonitis
Intraabdominal abscess
Intestinal occlusion
Paralytic ileus
Gastroparesis
Pneumoperitoneum
Hemoperitoneum
Hemo-retroperitoneum
Laparoscopic surgery
Abdominal-thoracic surgery
Ascites
Hepatic dysfunction
Peritoneal dialysis
Acidosis 
Shock
Hypothermia (temperature <33ºC)
Sepsis
Extensive burns
Major trauma
Massive fluid resuscitation (more than 5 liters in 24 hours)
Multiple transfusions 
Coagulopathies
Mechanical ventilation
Prone decubitus
Obesity.


Consequences of increased intra-abdominal pressure (IAP):

Brain : Increased intracranial pressure, and decreased cerebral perfusion.

Lungs : Atelectasis, decreased gas exchange, increased intrapulmonary shunt, decreased pulmonary capillary flow, decreased tidal volume, reduced compliance. 
As a consequence hypercapnia and hypoxemia occur.

Heart: Increased intrathoracic pressure results in compression of vessels such as the inferior vena cava and portal vein, as well as cardiac compression. 
Increased heart rate, central venous pressure, blood pressure, systemic vascular resistance, pulmonary artery pressure, as well as reduced cardiac output, end-diastolic volume, cardiac contractility and elasticity.

Renal: Compression of vessels and renal parenchyma, reduction of renal perfusion, renal blood flow, glomerular filtration, resulting in oliguria and even anuria.

Hepatic: Decreased arterial and portal venous flow, lactate clearance, glucose metabolism.

Therefore it's essential to monitor intra-abdominal pressure (IAP) on suspicion or confirmation of two or more risk factors and / or organ dysfunction.