Abdominal Compartment Syndrome

Introduction

Normal zero.
Mild elevation up to 15mmHg common in IPPV, obese, post abdominal surgery.
Compartment syndrome develops when pressure high enough to compromise blood flow.
Compartment syndrome occurs at pressures >25mmHg but can occur at lower pressures if hypovolaemic.

Measurement

Direct.
At laparoscopy.
Indirect.
Transmural

  • Bladder
  • Rectum
  • Stomach
  • Femoral vein
Practical
Bladder most commonly used via urinary catheter.
Fill with 100 mls saline so bladder wall acts like a diaphragm and there is a continuous fluid column to transducer (incorporated into system or attached to a needle inserted through the aspiration port).
Zero at level of symphysis pubis with patient supine.

The most basic method is to instil 100mls of saline and attach a suction catheter in place of the catheter bag (make sure you cover the hole with your thumb). Raise the end of the catheter in the air and measure how far above the symphysis the saline level is. This is the IAP in cm of H2O. Convert to mmHg. 10cm H2O = 7.5 mmHg.

Incidence

Up to 15% in blunt trauma.
Higher in AAA repair.

Causes

Abdomen will initially distend until limit after which pressure ↑.
Fluid.
Ascites
Blood
Oedema
  • SIRS – trauma, sepsis, pancreatitis etc
  • Fluid overload
  • Hypoalbuminaemia
Gas
Laparoscopy
Ruptured viscus
Bowel gas (obstruction)
Solid objects
Tumour
Faeces
Surgical packs
Abdominal wall
Obesity
Peritonism
Burn eschars

Effects

CVS
↓ cardiac output
  • ↓ preload - IVC compression in abdo and ↑ ITP
  • ↑ afterload - Vessel compression, low BP therefore a late sign
  • ↓ ventricular compliance - Diaphragmatic elevation compresses ventricles
  • Acidosis → ↓ contractility
Venous stasis → TE
RS
Diaphragm elevates
VQ mismatch (↓ FRC, atelectasis)
↑ inflation pressures due to ↓ lung and chest wall compliance
Renal
↓ renal blood flow
  • ↑ renovascular resistance
  • ↓ CO
CNS
↑ ICP
GI
Gut mucosal ischaemia
↓ hepatic blood flow
↑ anastomotic breakdown

Diagnosis

Clinical unreliable
CT suggestive
Measuring it the only definitive way




Management

15-25 mmHg
Optimal fluid loading (balance between increasing CO and minimising oedema)
Vasopressors to maintain APP 50-60 (MAP – IAP)
Prokinetics if ileus
Paracentesis if ascites
Consider muscle relaxants
>25
Muscle relaxants to buy time to surgery.
Surgical decompression +/- re-exploration.
Mortality in ACS without decompression is high.
Can be done on ICU.
Early decompression before organ dysfunction – 20% mortality.
Late – 50%.

Post decompression
Acts like clamp off in AAA
  • ↓ SVR
  • ↓ ITP → ↑ TV
  • Wash-in of toxic metabolites
  • Pre-oxygenate, fluid load, vasopressors to hand
Open abdo
  • Enteral feeding well tolerated
  • Large fluid losses
  • Heat loss