1. Abdominal Compartment Syndrome
2. Laparostomy and the Abdomen that Will Not Close
3. Management of the Open Abdomen

Indications
ACS and IAP
OA Consequences
Temporary Closure
Timing of Return to OT
Permanent Closure

Indications

If the abdomen cannot be closed or closed safely.
If a closed abdomen is judged unsafe.
Eg:
Abdo Trauma
Massive oedema to intestine & mesentery
- both from insult and necessary fluid resuscitation.
Damage Control Laparotomy
Where the triad of acidosis, hypothermia, coagulopathy, laparotomy may be terminated.
- pack the abdo, leave open.
- reschedule a look in 1-2d.
Secondary Peritonitis
Delayed diagnosis & perforation, ischaemic necrosis, anastomotic dehiscence, pancreatitis are typical situations.
Post-op Wound Dehiscence
- or abdo wall defect.

Abdo Compartment Syndrome (ACS) & Intra-Abdo Pressure (IAP)

Normal range is up to 5mmHg.
Intra-abdominal hypertension = >12 mmHg
Deleterious effects on heart, lung, kidneys, lungs and gut as low as 15 mm Hg
Abdominal comparment syndrome (ACS) = >20 mmHg with associated new organ dysfunction
Epidemic in the 1990s; now declining with judicious appropriate fluid management in trauma and other critical illness.

Characteristics of ACS

A hypoxic, acidotic patient despite high peak airway pressures, renal dysfunction, decreased cardiac output and a tense abdomen.
- immediately improved by abdo decompression.
ACS comes on incrementally.
- new evidence suggests IAP of 20mmHg (leads to resp, cardiac, renal and visceral abnormality).
--> fluids and inotropes may help avert ACS in this group.
Decompression may be accompanied by lethal reperfusion injury if severe.
Note that a patient with an open abdomen may develop ACS
- typically in the pack & run trauma laparotomy with ongoing bleeding.

Risk Fx
Abdo trauma, AAA rupture, severe pancreatitis, septic shock, severe SIRS of other causes.
Bowel swelling, third spacing, hypoalbuminaemia with extracellular fluid sequestration, contained haemorrhage.
>5L fluid per day or massive transfusion (>10u blood in 6h)
Acuteness of onset plays a role in how the abdomen can adjust to the change in pressure.
- thus there is no specific 'level' at which ACS occurs or becomes treatment-critical.
- and these pts often have organ dysfx for other reasons making treatment decisions difficult.

Grading
Grade I : 12-15 mm Hg
Grade II : 16-20 mm Hg
Grade III : 21-25 mm Hg
Grade IV : >25 mmHg
- recommended that grades 3 & 4 be decompressed.

When should IAP be measured?
When abdo distension with massive trauma, multiple transfusions and abdominal packing.
More subtly, when increasing organ dysfunction in context of a tense distended abdo and threat of ACS.
- impaired oxygenation
- cardiac failure (impaired venous return)
- oliguric renal failure
- GI ischaemia (decreased splanchic perfusion)

Diagnosis
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Measurement
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Abdominal examination is unreliable
At-risk pts need measurement using a system e.g. the above.
- ie a pressure transducer inserted via urinary catheter to bladder and zeroed etc as usual
- 25mL sterile saline into empty bladder, recording at midaxillary line

Management
Pts with pressures >20 who need ongoing fluid loading at the highest risk.
Medical Therapies
- improve abdominal wall compliance (sedation / anaesthesia); body positioning, muscular blocking
- evacaute intra-abdominal contents: NG decompression, rectal enemas, prokinetics
- perc drain any abdo fluid collections
- correct +ve fluid balance; diuretics, restriction, dialysis.

Rational for Opening.
1. Expansion of peritoneal space.
2. Allows orderly egress of fluids.
3. Facilitates subsequent laparotomy.
4. Minimising chances of intra-abdo sepsis.
It should be used out of necessity, ie only when IAH and ACS and clinical scenario dictate.
Abdominal closure should be performed as soon as possible when medical management failure and organ compromise.
- ventral hernia and fistula are main risks, and should not be incurred lightly.

Who gets an open abdomen in damage control surgery?
1. Patients with or at risk of IAH or ACS
2. Patients undergoing damage control surgery
3. Cannot close fascia
4. Nec fasc of abdo wall
5. 2nd look.

Damage control laparostomy; what next?
48h return to OT
- in meantime, correct physiology and achieve diuresis.
If still unable to close, return 48-72h later and perform sequential closure or VAC (see below).
- with sequential closure; freshen abdomen, lyse simple adhesions, clean
- then oppose upper and lower limits as possible; then VAC
- then repeat and repeat until closed.
- until D14: still no closure? Accept inevitible hernia and achieve visceral coverage
--> risk benefit at this time is resource intensiveness, fistula risk.
--> can simply close skin with vertical mattress 2.0 over abdominal contents. Or bridge with a biological mesh (maybe better; can also VAC over top if skin doesn't meet); or SSG.
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Component separation is not recommended in the acute setting
Biological meshes good but avoid them in heavily infected fields or the mesh disintegrates.
Long-term management otherwise as for massive abdo hernia.

Consequences of an Open Abdomen (OA)

Inflammatory Response
Inevitable profound local and variable systemic response.
Activation of neutrophils, macrophages and inflammatory cascade; SIRS
Activation of coagulation, cytokine and other inflammatory cascades in first 48hrs leads to massive fluid loss.
- this continues at a slower rate later.
The underlying pathology has a compound effect with the open abdomen.
- if there is ongoing pancreatitis, peritonitis, for example, the systemic response will be severe.

Coagulum / Adhesion formation
After 48hrs, fibrin forms in the exudate.
- a gelatinous mass holds the intestine and omentum loosely together.
Polymerisation of the fibrin follows and collagen is laid down during next 4-5 days.
- by day 10, abdomen is essentially sealed by vascular, organising granulation.
- initially by fibrin deposition and collagenisation.
- subsequently fibrinolysis predominates and laparotomy may not be possible after this for at least 6 weeks and possibly longer, until this process is complete.

Notes
1. Maturing adhesions are laying down increasing fibrin and collagen from first week.
- however this will not provide sufficient strength to the wound to allow cough impulse.
- a cough may cause unsupported abdomen in the first 3 weeks to rupture the fragile coagulum and eviscerate.
- serosal tears and fistulas may result.
2. Adhesion maturation fixes omentum and intestine to edges of abdominal wound.
- beyond d10, any attempt to dissect bowel away from the perterior aspect of the wound edges may result in multiple enterotomies and fistulas.
- delayed closure past d10 of an OA will be difficult unless specific interventions undertaken.

Secondary Peritonitis
Another risk of open abdomen.

Fistula
Catastrophe.  Mortality rates 30-50%.
May result from underlying pathology (eg leaky anastomosis)
- or from the OA (eg ill-advised dissection, or serosal tears at coughing / changing dressings).
Arising on a mobile portion of bowel, it may rise to the surface, where mucosa may be seen.
- organising granulation of the wound edge adheres and eventually it will unite at the edges of the abdominal wound.
- a retroperitoneal fistula to duodenum / pancreas will form a granulation-lined tract to meet abdo wound edges.
When associated with distal obstruction, maignancy, Crohn's, radiation, or when mucosa fixed to surface, spontaneous closure will not occur.
- up to 75% of other fistulas may heal (likely after weeks of nutritional and nursing care).
If a fistula is present after 10d in an OA, a long period of supportive treatment is inevitable before repair of fistula & closure possible.

Wound Edges
Wound retraction will progress during the first week, particularly if visceral oedema is pronounced.
- this may enhance the evisceration, with bowel loops widely outside the confines of the abdominal wall.
- if persisting, the bowel may lose its 'right to abode' and a large hernia becomes inevitable.
- high risk of serosal tear and fistula.
As rapidly as possible, eventration should be achieved: the abdomen, though open, contains its contents.
By week 2, granulation will occlude the OA surface, uniting the edges tenuously.
- progression over weeks and months forms a scar, which contracts much smaller than the original OA.
- this would take 3-6 months if an open abdomen is left to its own devices.
- initially a hernia may not be visible due to scar density; later scar thins and softens and a hernia will become apparent.
The option of skin grafting a granulating OA wound is controversial.
- speeds up healing, deals with metabolic / nutritional complications, tidy and dressing-free.
- but reduces contraction and collagen, leading to earlier larger herniae in the long-run.

Breathing and Coughing
The OA wall needs several weeks before it will be strong enough to cough and breath normally.
- mostly surgeons intervene prior by closing the abdomen / using prosthetic mesh.
The use of a VAC can provide effective support.

Renal function
Often these patients require large fluid volumes to maintain renal perfusion.
A proportion is sequestered intra-abdominally.
- intestinal oedema, mestery, retroperitoneum, abdominal wall oedema all result.
- waterlogged gut and mesentery tend to protrude through the OA, and steps must be taken to deal with this.
- compartment syndrome may be anticipated if laxity not given.

Intensive Care Dynamics
Communication is essential.
Important decisions include:
i) temporary abdominal closure
ii) timing of return to theatre
iii) permanent abdominal closure

Temporary Abdominal Closure

Principles
1. Encompass viscera; allow swelling while tamponading bleeding if reqd.
2. Contain fluid, prevents fluid loss; must seal / stick.
3. Prevent anterior adhesions.
4. Quick
5. Allows subsequent closure.

Components
Fenestrated inner layer
- AVOID direct suction on bowel or may get fistula
Middle layer of foam or towels
Suction mechanism to middle layer
Outer airtight seal.

Mesh
Provide abdominal support and allow respiratory rehabilitaiton to proceed.
Porosity is important
- should alow ongoing egress of exudate while maintaining abdominal support.
1. Polypropylene
- should not be allowed to remain in contact with serosal surfaces >7d, as beyond this, enterotomies are almost inevitable.
- maintains strength but IAH may recur as it does not expand well.
- healing without hernia but overshadowed by high rates of fistula and sepsis.
2. Polyglactin
- maintains strength for 10-14d before fragmenting; can be peeled off within 2 weeks.
- cannot expand, so ACS possible, may rip at suture lines.
- significant hernia rate, fistula rate 8%.
3. Woven polyglycolic acid
- maintains integrity <21d, embeds at 10-12d, granulation grows through.
- moderate fistula risk, high incidence of large herniae.
- has large interstices: low risk of ACS.

Bogota Bag
Sterile plastic bag opened and sutured to skin / fascia.
Easily available and simple to apply.
Initial measure, but deals poorly with fluid loss from the OA, does not contribute to abdominal support.

Vacuum-Assisted Closure
Subatmospheric pressure helps in healing wounds.
And controlled staged abdominal repair becomes possible.
An inert foil is placed over viscera, with esay access to wound edges for delayed primary repair.

Technique
1. Arrange omentum over viscera.
2. Cut a large bowel bag in a large sheet
- have an assistant hold it taught perform multiple punctures with a scalpel.
3. Place sheet over omentum and viscera.
- tuck it as far laterally as possible, 10cm or more.
4. Place 2 abdo packs over the polyethylene.
5. Place two Jackson-Pratt drains on the packs (one each side of wound).
6. Two further packs on top.
7. Carefully try abdo and place a large ioban / opsite stretched over wound under tension.
8. Return to ICU, connect drains to wall suction between 100-150mmHg.
- a Y connection can allow a single suction outlet.
- the wound will concave in, and fluid will flow.

Leave the Vac in place 3-5d, renew as necessary.
Dressings can be renewed in a general ward.
Laparotomy is easy, and the VAC can be easily replaced.

Advantages of the VAC
Easy, cheap, good ongoing care.
Low fistula rate cf mesh.
Allows delayed primary closure for up to 4 weeks.
Minimises chances of IAH.
Don't put them near a vascular repair.
- and safety near an anastomosis is unclear.

KCI ABThera
Similar but all within the supplied kit and connected to VAC setup

ABx?
No evidence for a role beyond the first 24h

Outcomes
Primary closure rate is 70-80%
Mean closure time 6-10d
Complications are fistula (5%), abscess (5%), delayed SBO (5%)

Timing of Return to OT

1. Mandated in damage control laparotomy.
2. Increasingly, the rest can be managed in ICU (dressing changes, minor debridements etc).
3. Return to theatre for major procedures, such as bowel resection, stoma, major debridement or tracheostomy.

Ettapenlavage
A concept of mandated daily formal laparotomy, debridement and cleansing in severe intra-abdominal infections until closure judged possible.
Good initial results.
But onerous, and associated with bleeding and fistulas.
Prefer a less intensive approach.

Permanent Abdo Closure

Staged repair / Sequential Closure
(STAR = staged abominal repair)
Visceral swelling and retraction of wound edges are opposing forces to closure.
Delayed closure is a relatively new idea.
- evolved to minimise complex secondary reconstruction.
Ideally OA should be closed by edge-to-edge fascial apposition within 7-10 days.
- a velcro fastener progressively tightened was pioneered initially.
VAC, with negative pressure assisting wound approximation is preferable.
- allows DPC of OA wounds for up to 4 weeks.
- the inert plastic foil is essential as it provides safe access to wound edges indefinitely.
Tension suture systems have been successfully employed
- tension closure generally to be avoided, but strong benefit in primary closure.
- risk of fascial necrosis minimised if tension applied incrementally & sequentially.
If closure remains impossible, continuing VAC for a minimum of 6 weeks is advised, before abdominal reconstruction contemplated.
- don't skin graft a granulating OA; a rapidly growing symptomatic hernia would be expected.

Delayed secondary closure
Long standing OA leads to ventral hernia.
If safe and accessible, repair fistulas first.
Then deal with the defect.
- easier if left to collagenise and scar than if grafted.
Fistula does complicated 25% of OA patients.
- if declared early, a window of opportunity to resect / stoma is afforded.
- more usually it appears in a granulating abdomen, meaning 6 weeks delay for definite treatment if it remains patent.
- easier to manage if a VAC, with daily dressings as required.
The hostility of the abdomen in a pt with ongoing intra-abdominal trouble may be predicted by the open wall.
- an oedematous, indurated, warm, blanching, non-mobile wall spells trouble.
- defer fistula resection and abdo reconstruction until these signs have passed.

Prognosis
High mortality associated with underlying pathology.
20-40%.
Resolution and good judgement are required.
Talk to the family regularly, they may be horrified.