Overview
Definition:
Abdominal compartment syndrome (ACS) is a life-threatening condition characterized by sustained intra-abdominal pressure (IAP) of 20 mmHg or greater, with or without an elevated abdominal perfusion pressure (APP), that is associated with new organ dysfunction or failure
Decompressive laparotomy is a surgical intervention to relieve this elevated pressure.
Epidemiology:
ACS can occur in various surgical and non-surgical settings, including major abdominal surgery, trauma, pancreatitis, intra-abdominal sepsis, and major fluid resuscitation
Incidence varies widely, with higher rates reported in critically ill patients post-trauma or sepsis, ranging from 5-15% in susceptible populations.
Clinical Significance:
Untreated ACS leads to progressive organ ischemia and failure, including renal, respiratory, hepatic, and intestinal dysfunction, significantly increasing mortality
Early recognition and timely decompressive laparotomy are crucial for improving patient survival and reducing morbidity in surgical and critically ill patients.
Clinical Presentation
Symptoms:
Progressive abdominal distension
Severe abdominal pain, often out of proportion to physical findings
Decreased urine output
Shortness of breath
Altered mental status.
Signs:
Tense, distended abdomen
Palpable bladder distension
Bradycardia or other hemodynamic instability
Tachypnea and hypoxia
Oliguria or anuria
Elevated central venous pressure (CVP) with hypotension
Absent or diminished bowel sounds.
Diagnostic Criteria:
The diagnostic criteria for ACS, as defined by the World Society of the Abdominal Compartment Syndrome (WSACS), include: sustained IAP ≥ 20 mmHg (with or without an inspiratory drop in mean arterial pressure < 5 mmHg) AND evidence of new organ dysfunction or failure.
Diagnostic Approach
History Taking:
Focus on conditions predisposing to ACS: recent major abdominal surgery, blunt or penetrating abdominal trauma, massive fluid resuscitation, pancreatitis, sepsis, ascites, bowel obstruction
Note timeline of symptom onset and progression.
Physical Examination:
Assess for abdominal distension and tenderness
Evaluate for signs of organ dysfunction: respiratory distress (hypoxia, tachypnea), oliguria (monitor urine output), hemodynamic instability (hypotension, tachycardia), and neurological changes
Assess for bladder distension.
Investigations:
Intra-abdominal pressure measurement: Via Foley catheter (transducer connected to catheter at mid-axillary line, zeroed at atmospheric pressure, measurement taken after instilling 25ml saline and waiting 30-60 seconds), direct intra-abdominal monitoring, or rectal balloon
Normal IAP is <5 mmHg
elevated IAP is >12 mmHg
ACS is typically ≥20 mmHg
Other investigations include serial ABGs for acid-base and oxygenation status, serum lactate for tissue hypoperfusion, renal function tests (BUN, creatinine), liver function tests, and urine output monitoring.
Differential Diagnosis:
Conditions mimicking ACS include ascites, bowel obstruction, severe constipation, ileus, retroperitoneal hemorrhage, and massive abdominal wall hematoma
Differentiating factors include the presence of sustained elevated IAP with associated organ dysfunction.
Management
Initial Management:
Maximize abdominal perfusion pressure (APP = Mean Arterial Pressure - IAP)
Optimize hemodynamics with fluid resuscitation and vasopressors if necessary to maintain MAP > 65 mmHg
Mechanical ventilation to support oxygenation and reduce abdominal wall compliance
Sedation and analgesia
Decompressive laparotomy is indicated when medical management fails to improve organ function and IAP remains elevated.
Medical Management:
Aggressive fluid management to maintain adequate circulating volume
Vasopressors (e.g., norepinephrine) to maintain MAP
Diuretics to reduce fluid overload and urine output if renal perfusion is adequate
Nasogastric decompression to reduce gastric distension
Optimization of ventilation
Neuromuscular blockade can transiently lower IAP.
Surgical Management:
Decompressive laparotomy is the definitive treatment for ACS
Indications include IAP ≥ 20 mmHg with evidence of organ dysfunction, or IAP ≥ 12 mmHg with evidence of organ dysfunction and failure to respond to medical management
The procedure involves opening the abdominal cavity to release pressure
Techniques include midline laparotomy
Abdominal wall closure may be delayed using temporary abdominal closure devices (e.g., Bogota bag, vacuum-assisted closure) to allow for edema resolution and prevent fascial dehiscence.
Supportive Care:
Intensive monitoring in an ICU setting
Close surveillance of hemodynamics, respiratory function, renal output, and IAP
Nutritional support
Management of sepsis and organ failures
Pain control and sedation.
Complications
Early Complications:
Intra-abdominal bleeding, bowel ischemia or necrosis, damage to abdominal organs during surgery, incisional hernia, wound dehiscence, entero-cutaneous fistula, prolonged mechanical ventilation, sepsis, renal failure, ARDS.
Late Complications:
Chronic abdominal pain, incisional hernia requiring repair, intestinal dysfunction, adhesions and bowel obstruction, malnutrition, psychological sequelae.
Prevention Strategies:
Awareness of risk factors
Early identification of increased IAP
Prompt medical management
Judicious fluid resuscitation
Minimizing intra-abdominal packing and fluid accumulation
Early decision-making regarding surgical decompression.
Prognosis
Factors Affecting Prognosis:
The primary determinant of prognosis is the promptness and success of decompression
Severity of underlying illness, presence of sepsis, number of failing organs, and duration of elevated IAP prior to decompression significantly impact outcomes.
Outcomes:
Mortality rates in ACS remain high, ranging from 30-50%, and can be higher depending on the cause and delay in treatment
Survivors often experience significant morbidity
Successful decompression with resolution of organ dysfunction improves survival significantly.
Follow Up:
Close follow-up in an ICU and surgical setting
Serial monitoring of IAP if recurrent ACS is suspected
Management of hernias and nutritional deficits
Rehabilitation and psychological support for long-term survivors.
Key Points
Exam Focus:
Understand the definition and diagnostic criteria of ACS (IAP ≥ 20 mmHg + organ dysfunction)
Recognize risk factors and clinical signs
Know the indications and principles of decompressive laparotomy, including temporary abdominal closure
Be aware of complications and prognostic factors.
Clinical Pearls:
Measure IAP routinely in high-risk patients
Do not delay surgical decompression if medical management fails and IAP is persistently elevated with organ dysfunction
Consider temporary abdominal closure for definitive management of abdominal wall closure in the presence of significant edema
Optimize APP to > 60-65 mmHg.
Common Mistakes:
Delaying diagnosis or intervention due to vague symptoms
Underestimating the severity of ACS
Inadequate fluid resuscitation or reliance solely on vasopressors without addressing the elevated IAP
Failure to consider ACS in patients with abdominal sepsis or massive trauma
Improper technique for IAP measurement.