Editing Open abdomen (section)

== Phases: ==
'''Sabiston divides it into 5 phases:'''

# Initial laparotomy and use of temporary closure device
# ICU resuscitation
# First re-operation
# Management of open abdomen
# Planned ventral hernia

=== '''Phase 1: Initial laparotomy and use of temporary closure device''' ===

* '''Indications for temporary abdominal closure (open abdomen)'''
** Patients with/at risk of IAH/compartment syndrome
** Damage control
*** Severe haemorrhage
*** Hypothermia, acidosis, coagulopathy
*** Delayed definitive operation secondary to patient's physiologic state
** Major abdominal and/or retroperitoneal tissue oedema
** Questionable visceral viability
** Planned acute re-operation
** Severe intra-abdominal sepsis
** Triage
* '''Goals:'''
** Minimise damage to abdominal contents
** Minimise adherence of abdominal contents to anterior abdominal wall
** Retain the ability to close the fascia primarily at a subsequent operation '''(aim to close within 8 days - much higher rate of complications after this point)'''
* '''Techniques:'''
** '''Skin closure techniques'''
*** Simple running sutures
*** Sequential towel clip closure
*** Silo technique/Bogota bag
**** Suture an inert, non-permeable barrier (IV bag etc) to the skin or fascia
**** Prone to leakage/evisceration
**** Do not prevent retraction
**** Do not allow effective removal of abdominal fluid
**** Rates of primary closure are mostly <30%
** '''Fascial closure techniques'''
*** Vicryl/biological mesh, polypropylene mesh, Wittman Patch, Esmark bandages, expanded PTFE
*** Should initially be loose to allow for visceral swelling without ACS
*** Do not prevent adhesions to anterior abdominal wall
*** For non-absorbable meshes, fistula formation is very high (6-18%) if a non-adherent barrier is not placed under the mesh (omentum, Ioban sheet)
*** Sequentially tightened by excising the central part and resuturing the fascial material closed
*** Should typically be tightened every 24-48 hours until the fascia is 2-4cm apart, at which point the fascia is closed primarily
*** Most useful when an extended duration of laparostomy is predicted (unlikely to be closed by 8 days)
** '''Negative pressure applications'''
*** ABThera - inner plastic-encased sponge designed to be indirect contact with the viscera, followed by a macroporous foam sponge, followed by adhesive dressing
**** Tips for ABThera
***** Maximally lateralise the internal visceral layer - prevents bowel from slipping out, and prevents adhesions. Some suggest taking down falciform ligament to help get it right into paracolic gutters.
***** Bury any intestinal anastomoses deep in abdominal cavity
***** Test thoroughly for leaks (can use tincture of benzoin)
***** Can use staples to fix sponge to skin edges (need it flush, as any contact of skin to sponge can damage epidermis, but you also want full coverage of wound)
***** Ostomy appliances should be OVER the adhesive layer, not under, or you risk sucking poo into the wound
***** Get the hole sized right - many manufacturers suggest 2x2cm
***** Adjust suction level as needed - 125mmHg is optimal for wound healing, but put down to 75mmHg if there is bleeding/coagulopathy
*** Low rate of fistulas (but beware of anastomoses directly under the pack and intra-abdominal sepsis), average primary closure rate of 67%
*** Highest primary fascial closure rates when the VAC is used in conjunction with a fascial tension device (such as simple interrupted fascial sutures which are added/tightened each relook)
* '''Choice of initial technique'''
** My approach:
*** Definitely one relook: Abthera/VAC 
*** Going to need multiple relooks: Large polypropylene mesh, with Ioban on each side, then VAC over the top
** Consensus guidelines recommend NPWT techniques initially, during the resuscitative phase where risk of ACS is highest
** NPWT is especially favoured in inflammatory pathologies - highest delayed primary closure rate, lowest mortality, lowest ECF formation

=== '''Phase 2: ICU resuscitation''' ===

* Management in ICU with the open abdomen
** Nutrition - Sabiston says early enteral nutrition in the open abdomen is beneficial, if feasible
** No specific antibiotic prophylaxis - data says unnecessary
** Strict fluid balance aiming euvolaemia
** Can be extubated between washouts if co-operative
** Correct hypothermia, coagulopathy and acidosis
** Minimising crystalloid infusion has been shown to increase rates of primary fascial closure
** Routine monitoring of intra-abdominal pressures in those with large-volume resuscitation due to haemodynamic instability or ongoing bleeding
*** See separate topic, but essentially, if bladder pressure >20mmHg, monitor hourly, and if any sign of end-organ dysfunction, needs return to theatre

=== '''Phase 3: First re-operation''' ===

* '''Takebacks'''
** Washout and re-VAC every 1-3 days
** Only do it at the bedside if patient is unstable and can't go to OT
** Check for complications/problems that will delay closure and serial fascial tightening
** For first 24-72 hours after index operation, adhesions are soft and give way easily. Operating again between 1-4 weeks can be hazardous. Avoid using sharp dissection. Generally look for collections at the periphery, and try to leave the 'central visceral block' alone.
* '''Check for reasons to delay closure:'''
** Ongoing inflammatory response
** Visceral oedema
** Retraction of abdominal wall musculature
** Lack of source control
** Intra-abdominal abscess
** Enterocutaneous fistula
* '''Assess readiness for closure:'''
** Direct closure is usually possible when the fascial edges are 3-7cm apart
** Intra-abdominal pressure >20mmHg or a rise of peak inspiratory pressure of 10cm H2O during attempts to close fascia are warning signs
** Delayed fascial closure (phase 4) might be prudent in this group
* '''Choice of technique to close after relook laparotomy:'''
** Patients predicted to be uncomplicated and likely to close within 8 days: NPWT + sequential fascial closure
** Patients with risk factors for difficult abdomen: NPWT + serial fascial tightening
*** Direct serial suturing if feasible
*** Interposition polypropylene mesh protected by Ioban if abdomen is too tight for direct suturing

=== '''Phase 4: Management of open abdomen''' ===

* '''Techniques for definitively closing the difficult open abdomen'''
** Serial fascial suturing in combination with NPWT
** Gradual fascial tightening via trans-fascial tension-bearing closure techniques
*** Principle is to redistribute tension lateral to rectus sheath, theoretically lengthening lateral wall musculature
*** Techniques
**** Wittman Patch (artificial burr)
**** Transabdominal wall traction (TAWT)
**** Mesh-mediated fascial traction
***** Protect viscera with a polyethylene sheet or double-sided Ioban
***** Suture in an oval-shaped inlay polypropylene mesh
***** Apply VAC over the top (Abthera)
***** Takeback every 2-3 days: exchange the protective sheet, and serially tighten the mesh, until it can be removed
** Biosynthetic mesh - avoid in acute setting due to risk of infection
*** Options - human acellular dermal matrix (HADM), absorbable mesh like Vicryl, composite meshes
*** Techniques - two options
**** Underlay - if skin is lax enough to close but fascia not, you can place the mesh as underlay and directly close the skin. The mesh would typically be placed intra-peritoneal and secured with transfascial sutures.
**** STSG - if neither skin nor fascia can close, the mesh is placed underlay intra-peritoneal with standard saline moist to dry dressings BD for 2-4 weeks until satisfactory granulation has appeared in the wound bed. Then STSG can be placed. Will then need definitive component separation and delayed closure in 6-9 months. See bottom of page for a description of how to definitively close this type of abdomen.
** Component separation - full component separation is not recommended in acute setting - makes future hernia repairs much harder
* Pharmacologic adjuncts
** Continuous neuromuscular blockade doesn't make a difference
** Botox injection has been shown to help in both elective and acute setting

=== '''Phase 5: Planned ventral hernia''' ===

* If closure has not occurred by 8-14 days, it is unlikely to be achievable in the acute setting (although plenty of closures have been reported up to 20-40 days)
* Options:
** If able to close skin: skin closure with absorbable mesh inlay or biologic mesh over drains
** If unable to close skin: intra-peritoneal vicryl mesh, with STSG on top once granulation tissue appears
** If persisting infection/dirty wound: biologic bridge repair with overlay NPWT
* Then aim for future ventral hernia repair when everything else is optimised