General Patient Wellbeing

Wound management is optimized if the patient’s overall condition is as good as can be achieved. In acute wounding, adequate resuscitation is essential. Assessment of tissue viability and, therefore, debridement is compromised in a poorly perfusing patient. Compromised tissue will do less well with reduced oxygen delivery. The deleterious effects on wound healing of the systemic inflammatory response and metabolic response to trauma can be reduced in impact by good supportive care[2]. The nutritional state of the patient is important: the detrimental effects of chronic malnourishment need to be anticipated and managed. This includes consideration for reducing the patient’s parasite load, although there is some debate about the efficacy of this. Prophylaxis against tetanus must be ensured. There is a complex interaction between pain, stress levels, and the metabolic response, and adequate pain management strategies need to be available[3,4,5].

The Clinical Environment

This is an area of considerable challenge. By the very nature of a field hospital, control of the clinical environment is more difficult. The climate within a facility is much more influenced by external factors. Maintaining patient normothermia is most easily achieved if the internal ambient temperature is middle-to-high-twenties degrees centigrade. If lower than this, the use of near patient warming devices such as fluid warmers, warm air over-blankets, and under-patient warming mattresses is of help. There is no evidence of harm from the ambient temperatures being in the high-thirties degrees centigrade, but it is uncomfortable for patients and staff alike. Even tented facilities can be equipped to improve environmental control, creating clinical white space through the use of liners and additional outer shading layers plus air conditioning units.

Simple hygiene is of importance. Outcomes in wound management are adversely affected by infections. The potential for significant cross-contamination via staff and equipment is high. There is no reason why basic infection prevention and control measure cannot be followed[6]. Handwashing with soap and water and/or use of antiseptic hand rubs after each individual patient contact should be mandated and policed: there is no excuse for failures in such practices by staff. In genuine mass-casualty situations, the bedding down of large numbers of patients, sometimes in the open, makes it difficult to keep such areas clean, but the clinical spaces used for interventions and procedures should have clear protocols to maintain minimum standards of cleanliness.

Patient confidentiality should be respected with invasive interventions and, ideally, examinations being screened from general view.

Paying attention to the maintenance of standards in the clinical environment brings a sense of professionalism and “protected space” that instils confidence and morale among patients, as well as improving outcomes.

Antibiotics

The continued rise of antimicrobial resistance has led to attempts to more tightly restrict the use of antibiotics in normal clinical practice[7]. With respect to wound care, while infections will be treated, there are more general trends away from prolonged antibiotic prophylaxis. In the field hospital environment, assumptions are made about degrees of possible wound contamination which make the use of prophylaxis more appropriate, but this must be tempered with a rational approach. Prolonged use of broad-spectrum antibiotics simply as a precaution will result in the emergence of complex resistant strains of microorganisms.

The mainstay of wound care remains physical interventions with surgery, but for ballistic, blast, and contaminated wounds, it is accepted that there must be concomitant administration of antibiotics as prophylaxis[8]. Antibiotics alone cannot replace the need for surgery.

Field hospitals should have a clear policy of antibiotic use, which is appropriate to the environment in which it is operating. Individual clinicians must not be allowed to override the policy with attitudes based on their nondeployed practice.

A basic approach to antibiotic use in wound care is:

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  prophylaxis should be with broad-spectrum antibiotics, which cover those organisms known to cause early wound infections, predominantly Staphylococcus, Streptococcus, and Clostridium species

  
  
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  the first dose should be administered as soon after wounding as possible

  
  
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  a second dose is given at the time of debridement

  
  
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  a third dose is given about six to eight hours after that

Indications for prolonging prophylaxis beyond three doses are:

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  exposed bone

  
  
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  penetrating eye injuries

  
  
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  penetrating central nervous system injuries

  
  
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  where there is retained contamination within anatomically difficult areas, such as joints

Consideration of antibiotic choice should include tissue penetration for eye and central nervous system wounds, and additional anaerobic organism cover for bowel injuries.

If the wound is clinically infected at presentation, then use the same antibiotics as for prophylaxis. If the infection fails to clear or develops after prophylaxis, change to an antibiotic based on a knowledge of likely resistance patterns within the local geographical area.

If the field hospital has a microbiological laboratory capability, a policy of using wound surveillance swabs will help build a picture of local pathogens and resistance.

Wound Hygiene

The patient as a whole should be viewed as being dirty. Clothing should be removed, but kept to give back to the patient later. A very wide area of uninjured skin around the wound should be cleaned using a soapy solution in warm water and then dried. This is not a formal surgical preparation, but a basic hygiene clean known as a social wash. Ideally, the whole patient should be cleaned, but this may not be practicable preoperatively.

Nonsurgical Control of Hemorrhage

General oozing from the wound can be controlled with a pressure dressing and/or elevation.

There are several types of topical hemostatic agents available[14]. These are primarily designed for prehospital use to mitigate for a lack of surgical capability where tourniquets and pressure dressings prove inadequate, such as in junctional areas. Their use within hospital should be limited to extreme situations only; for example, an overwhelming number of casualties. Once within a field hospital, where surgeons and operating theaters are available, the approach to continuously bleeding wounds should be formal surgical control.

If the patient has a tourniquet in place, either from prehospital or applied on arrival during the primary survey, this should be evaluated before the wound is addressed. If the initial tourniquet has been on for significantly more than two hours, discussions about managing the patient’s general condition, overall distal viability, and potential need for fasciotomies should be had before it is released. If the tourniquet is a simple windlass type, as is common for prehospital use, this should be replaced by a pneumatic one as soon as is practicable. This can be placed proximal to the windlass, but not inflated initially. It should also not be applied too tightly such that it constricts venous flow when not inflated. The existing tourniquet can then be released and the wound observed. If there is no significant hemorrhage, then the pneumatic tourniquet does not need to be inflated immediately but should remain in place as a precaution or for use during debridement. This then allows an assessment of distal vascularity.

If, on releasing the tourniquet, there is significant bleeding, inflate the pneumatic tourniquet, and formal surgical vascular control should be obtained. Having an inflated pneumatic tourniquet in place makes the patient a priority for surgery.

Opinions on whether to debride a tourniquet-controlled exsanguinated limb or not vary and there is no hard evidence to support either view. Some feel that an injured limb is already undergoing a degree of vascular insufficiency and further periods of nonperfusion are potentially detrimental to the tissues. Others state that proper evaluation is not possible in a bloody field and the ongoing additional bleeding is not good for the patient and may increase demands on limited blood product stocks. Having an agreed approach in advance is preferable to having to make ad hoc decisions in the heat of the moment.

Nonpneumatic tourniquets designed for the prehospital environment are not appropriate for peroperative use. If a tourniquet is used during surgery, it should be released prior to any dressings to allow final assessment of tissue viability and control of any residual bleeding. It should be noted that on letting down a tourniquet, there is always a hyperemic surge with associated increase in bleeding and a sudden release of anaerobic metabolic products into the general circulation, which may have physiological sequelae in a shocked patient. It is important to communicate with the rest of the team that the tourniquet is about to be let down so any patient optimization can be performed. It is advisable to wrap the limb in gauze swabs and temporarily elevate it as the tourniquet is released to reduce the impact of the hyperemia.

General Wound Inspection

Much can be gleaned by observation with the patient under anesthesia in a controlled, well-lit environment, dressings off, bleeding controlled, and dirt and clothes removed. New wounds may have been uncovered during the social wash. Patterns in wounding can be assessed; for example, if there are several wounds, are they linked? Are there obvious signs of abnormal position suggesting fractures, dislocations, or tendon division? At this stage it is worth reviewing any radiological imaging and establish if all required views have been obtained. Any findings should be documented accurately; in particular, the size and position of wounds. There is always a possibility that these peroperative findings will form part of the evidence base for future legal considerations. With that in mind, it is important to avoid speculating as to the origin of wounds such as bullet versus fragment or entry versus exit. Your responsibility is to describe what you find as a professional description of fact, not to extrapolate that into opinion as to causation. The legal jurisdiction under which the field hospital functions should not unduly influence clinical practice, but clinicians must be aware of what their responsibilities are in terms of how information and material that may become evidence should be handled.

Having fully observed the location of all wounds and made an assessment of likely damage to anatomical structures, the patient can be formally prepped and draped for surgery with the exposed operative field based on an appreciation of likely procedures. For example, a high groin wound that may have caused a vascular injury should be prepared to permit proximal control to be obtained at the level of the iliac vessels, a vein graft to be harvested from the uninjured leg, and fasciotomies to be performed.

Information about the planned procedure should be shared with the full surgical team in the form of a safe surgery brief such as the World Health Organization (WHO) checklist[15]. This can be performed very rapidly in emergency situations and being in field conditions is not an excuse for missing out this vital patient safety step[16].

The process of performing the various surgical stages listed below has been broken down to aid explanation. In reality, for practicality and efficiency, the steps will be overlapping.

Wound Edge Excision

The rim of skin around any wound will have a degree of contamination and contusion. Skin has a good blood supply and is relatively resilient, so any excision can be minimal. Even heavily contused, degloved or abraded skin may survive and if it does progress to necrosis the risk to the patient of leaving small amounts of dead superficial tissue is very low. It is prudent to remove a 1 mm rim of skin from around a wound and only remove more if it is obviously nonviable. Over-exuberant excision risks converting a wound that is suitable for delayed direct closure into one that requires a more complex reconstruction.

Wound Extension

It is rare to be able to visualize the full extent of a wound through the skin defect. Wounds should be extended surgically to properly explore and this must include deep fascia. Also, a wound will become edematous and the rise in tissue tension restricts perfusion. Any deep contamination is more likely to cause suppuration if trapped. The process of opening a wound by extension “unbridles” the tissues, allowing free drainage of exudate and swelling without pressure increase. This is the origin of the term debridement.

Wound-extension incisions should be along normal lines of election in the limbs; that is, longitudinal with a horizontal component across flexion creases and in a way that allows fasciotomies and access to neurovascular bundles to be performed if necessary. In the torso and head and neck, extensions should be planned to anticipate underlying injuries and/or along natural skin creases. The extensions should only be so long as to decompress fully the zone of injury and allow what further procedures are required.

Wound Exploration

A thorough exploration of the wound is made to establish what structures have been injured and to assess viability of tissue and the degree of contamination. Some low energy projectiles can separate tissue planes without causing much visible disruption; it is important to spot subtle signs such as air or hematoma. Preoperative imaging can play a very useful part in predicting wound tracks. The anatomical position of the patient on the operating table is unlikely to be the same as when they were injured, and wound tracks will not necessarily be in straight lines. The exploration may well involve extending the wound further; in particular through deeper structures. It is not necessary to lay open every wound fully if it is clear that no significant deeper structures are damaged, and contamination and cavitation are likely to be minimal. This requires a degree of surgical judgment.

Great care must be taken not to increase the risk of vascular compromise to tissues as wound extensions and explorations are performed. It should also be performed in a way that does not remove potential reconstructive options. Limbs should be explored by raising the skin in the subfascial plane and preserving perforating vessels where possible.

Establishing a Surgical Plan

Wound extension and exploration essentially provide a wound diagnosis. Decisions now must be made about what needs to be done during this surgical procedure and what is better to be left. Devitalized tissue and contamination should be excised. In the majority of field hospital situations, the basic principle will be that of delayed repair. Immediate repair of damaged structures and closure of wounds that are caused by ballistic or blast mechanisms, sustained in a heavily contaminated environment, and where optimal care is not guaranteed is a highly risky approach. There are, however, some situations where immediate repair is necessary, and this should be performed as part of the IWS. There are also injuries where temporizing measures can be used. These decisions must be made with a full appreciation of the overall situation and context as outlined above.

Essential Surgical Interventions

Damage-control procedures to save life are, of course, essential. The main indication for repair at the time of initial wound surgery is restoration of vascularity. If larger vessels are damaged, a decision is needed as to the impact that will have on the viability of remaining tissues[17,18]. If repair will confer no benefit in terms of more distal viability, it is appropriate to ligate a damaged vessel. If by restoring flow there will be better functional recovery, then primary repair is indicated, even if this requires a patch repair or interposition graft. In contaminated wounds, autologous graft should be used in preference to artificial materials. If the surgical capability to perform a repair is not available or it is not appropriate because a damage control or abbreviated surgery approach is indicated, shunting of vessels can be performed[19]. This can also be done as a temporizing measure to allow a patient to be moved to a facility with greater capability in terms of vascular repair. If it is planned for a field hospital to receive patients with significant wounds, but it possesses no vascular surgery skills beyond ligation, questions need to be asked about the suitability of the facility to be allocated that role.

Ongoing contamination, such as leaking bowel, must be controlled.

The presence of compartment syndrome or a risk of it developing is an indication for fasciotomies as part of initial wound surgery. Similarly, retrobulbar hematomas should be released by lateral canthotomy.

Excision of Devitalized Tissue and Contamination

Removal of all visible contamination is a goal that is not always easy to achieve. Large pieces loose in a wound can be picked out individually. Finer material will often be firmly adherent to tissue and cannot be wiped off or irrigated out. Efforts to sharply excise all such material may remove otherwise healthy tissue. Material impregnated by a blast or ballistic mechanism will often follow tissue planes and it is possible to remove this by delicate excision of adventitial layers leaving functional structures intact. It has been shown that small metallic objects such as bullets and fragments which are deeply embedded in viable tissue can be safely left[20]. Any foreign body encountered during wound excision should be removed, but it may not be necessary to go hunting for every fragment seen on imaging. Fragments that are intraocular, in a synovial joint, or where they may cause impingement with the potential for erosion should be removed, although specialist surgical expertise may be required. More caution needs to be used with embedded environmental nonmetallic materials, and experience has shown that, if left, these will rapidly lead to local pus formation.

Decisions about how much tissue to excise are not solely related to assessment of viability at the time of debridement. Differing tissues have differing resilience and there are differing consequences of the way dubiously viable tissue is managed.

There are general factors to consider:

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  Is the patient’s physiological state contributing to apparent nonviability and will this improve?

  
  
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  Is there any risk that a change in the patient’s condition may go unnoticed, such as poor staff levels on the ward or the patient being moved to another facility?

  
  
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  Will future workload make it difficult to reassess the wound in the operating theater at an appropriate time?

It may be appropriate to leave some dubiously viable tissue if there is a degree of confidence in the control there will be over the patient’s postoperative care. If there is any doubt over what might happen to the patient in the next few days, it is more appropriate to be more radical in how much tissue is excised.

Then there are tissue specific factors to consider:

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  As described above, skin is reasonably resilient and well vascularized and should be preserved as much as possible to aid later wound closure.

  
  
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  Fat is poorly vascularized and has little functional benefit, so can be excised fairly radically. Caution should be taken in over-thinning the fat layer immediately beneath the skin as this can compromise the dermal blood supply.

  
  
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  Deep fascia, tendons, and ligaments are also poorly vascularized, but have a very low metabolic demand and are difficult to assess viability. There is also little harm in leaving them at IWS as long as gross contamination is removed. These are structurally resilient and useful tissues and worth preserving initially so simple trimming of ragged edges is all that is required. If nonviable, they tend to lose structural integrity over time and can be excised later.

  
  
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  Muscle is very sensitive to trauma and, even with its good vascularity, is liable to undergo necrosis. It is also liable to become infected once dead, and retained nonviable muscle presents a risk to the patient. It is therefore usual not to preserve dubiously viable muscle. Surface contamination of muscle can be removed by excision of the epimysial layer while preserving function.

  
  
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  Neurovascular bundles should be preserved at IWS and function not compromised by over-exuberant excision of contamination. Heavy contamination can be removed by careful excision of the loose adventitial tissue. Care should be taken to avoid unnecessarily dividing small side branches as this can lead to further devascularization and denervation of surrounding muscles. There is no indication to tag the ends of divided structures, particularly nerves. Tagging in itself causes a degree of further damage and, at later surgery, any reconstructive surgeon will know how to find the structures with the normal approach being to first identify healthy tissues outside of the zone of injury.

  
  
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  Bone fragments, no matter how comminuted, should be retained if there remain attachments to soft tissues and, therefore, a blood supply. Completely loose fragments should be removed.

There are no reliable, near patient, intraoperative investigations that are appropriate for the field-hospital environment that can give useful information about tissue viability. Assessment relies on the visual inspection by the surgeon. It would seem intuitive that the experience of the surgeon is the most sensitive measure, but this has not always been found to stand up to scientific scrutiny[21]. Small-vessel bleeding from tissue may confirm vascularity, but gives no indication about potential tissue survivability at the cellular level. Lack of bleeding in itself does not mean tissue will not survive as tissues may reperfuse as the patient’s general condition improves. Contractility of muscle does demonstrate that the muscle is currently functioning and, therefore, alive, but progressive necrosis over the next few days is well recognized. Gross distortion of normal macroscopic architecture usually results in nonviable tissue.

As bleeding is encountered it should be addressed. Continuing to work in a bleeding field is a poor surgical method as it further insults the patient’s physiology and makes assessment of tissues more difficult. Electrocautery, preferably bipolar, is useful for individual vessels but should not be used to scorch raw bleeding areas. This leaves a necrotic layer and makes assessment at later surgery more difficult.

The tissues of the hands and face are highly specialized and with little redundancy. Loss of form and function in these areas has a huge impact on the patient’s ability to perform in society. Every effort must be made to preserve tissue so as to maximize the reconstructive options. IWS should be as minimalistic as possible with the focus being on removal of gross contamination and preservation of blood supply. Involvement of specialists in hand and facial surgery should be sought as early as is realistically possible.

Amputation at IWS

Primary amputation to a defined level at IWS is not advocated. There are several factors that might influence the final level of an amputation, including patient preferences, and it is unlikely all the information will be available immediately.

Cases will present where there has been complete or near complete traumatic amputation by the mechanism of injury. It may also be obvious that even if the limb is still attached there will be no effective reconstructive options once all nonviable tissue is removed. In these cases, the process of removing nonviable tissue remains the same and this may result in what would be recognized as an amputation. What should not be done is excision of any viable tissue in anticipation of a predicted final amputation level. This includes bone, which, if viable, can be left longer than the soft tissues. This has been found to be useful in splinting the tissues and handling during procedures.

This approach means at IWS a significant limb wound is debrided, not amputated, even if the result of debridement is a shortened limb.

Wound Irrigation

With essential surgical procedures and excision of nonviable tissue complete, the final part of removal of contamination is wound irrigation. This will aid in washing out loose debris. More importantly, it will also reduce the total bacterial load in the wound and lower the chance of the residual microscopic contamination progressing to invasive infection.

Large volumes of low-pressure warm isotonic solutions are preferable[22]. Using fingers to gently agitate the tissues helps loosen material and ensures deeper recesses are reached. Evidence suggests that high-pressure irrigation systems can drive contamination deeper into tissues and potentially increase the risk of infection[23]. There is little clinical evidence to give guidance on how much fluid to use, but common practice is for about 3 L for each limb that has simple wounds, increasing to about 9 L for heavily contaminated open fractures. This places a significant resupply burden on a busy field hospital. A practical alternative is to use water that is clean enough to drink as the initial irrigating fluid and use sterile crystalloid for the last liter. Irrigating with common antiseptic solutions such as iodine, hydrogen peroxide, and chlorhexidine has not been shown to improve clinical outcomes[24,25].

A final check is made of the wound as irrigation can reveal new areas of contamination and restart some bleeding. If any deep pockets with narrow openings leave significant dead space, simple soft plastic ribbon drains can be used.

Any temptation to loosely close the tissues to restore anatomical alignment with sutures must be resisted. If vital structures need acute coverage, then this should be a formal surgical procedure.