8 Surgical Debridement of Penetrating Injuries

10.1055/b-0035-121754

8 Surgical Debridement of Penetrating Injuries

Roland A. Torres and P.B. Raksin

Introduction

Although open head injuries are commonly referred to as penetrating, not all such injuries are alike. The term penetrating injury technically describes the situation in which a projectile enters the skull but does not exit. A perforating injury occurs when the projectile passes entirely though the head, leaving both an entrance and an exit wound. This distinction has prognostic implications. In a series of projectile-related head injuries during the Iran-Iraq War, patients treated for perforating wounds had a poorer postsurgical outcome (50% greater morbidity and mortality) than those treated for penetrating wounds. ¹

Penetrating head injuries may result from intentional or unintentional events, including shootings, stabbings, blast injuries, and motor vehicle or occupational accidents (e.g., nails). Stab wounds are characterized by a smaller impact area and lower velocity than missile wounds. For the purposes of this chapter, we limit our discussion to missile wounds.

Historically, the management of civilian missile injuries has been informed by and evolved in concert with military practice. Since World War II, military neurosurgeons have uniformly advocated thorough debridement and watertight dural closure to prevent cerebrospinal fluid (CSF) leak and possible infection. During the Vietnam War era, craniectomy or craniotomy was accompanied by aggressive debridement of the in-driven bone, projectile fragments, and associated debris. The pursuit of debris into areas of potentially viable brain tissue was believed to be responsible for additional neurologic deficits and impairment. ² ^, ³ Partially in response to this finding and as the result of experience gleaned from multiple military conflicts over the past 40 years, a new management paradigm has emerged. Initial treatment of projectile wounds of the brain is now designed to preserve the maximum cerebral tissue and function either by limiting the wound debridement performed through a craniectomy or by care of scalp wounds only. ⁴ ^– ⁶ Branvold et al found no relationship between the presence of retained fragments and the development of either a seizure disorder or an infection of the central nervous system. ⁷ Findings such as this one support the growing consensus that routine reoperation for removal of retained fragments is unnecessary. The net result of this strategy has been improved outcomes with significantly decreased morbidity and mortality.

Indications

The totality of the observed injury reflects a combination of forces: (1) direct crush injury inflicted by the projectile along its path; (2) cavitation produced by the centrifugal effects of the projectile on the parenchyma; and (3) stretch injury resulting from the shock wave generated by the projectile in transit. Each must be factored into the decision-making process.
Two fundamental decisions drive management: (1) whether or not to operate and, if so, (2) the extent of the intervention to be undertaken.
The decision of whether or not to operate is dictated both by clinical status and the observed radiographic pathology.
- Supportive, expectant (nonoperative) management may be appropriate for a patient presenting with a Glasgow Coma Scale (GCS) score ≤ 5 and bilateral fixed, dilated pupils post-resuscitation.
  - If such a patient presents with a potentially reversible mass lesion and is deemed otherwise medically viable, consideration may be given to emergent operative intervention.
  - If no extra-axial mass lesion is present, consideration may be given to a trial of hyperosmolar therapy (20% mannitol bolus 1 g/kg); if a significant improvement in motor exam and/or pupillary response is noted, the patient may be considered a potential candidate for surgery.
- Hemodynamic instability and/or profound coagulopathy may influence the decision to forego operative intervention.
- Certain ominous radiographic findings portend a poor prognosis: anteroposterior or bilateral hemispheric through-and-through trajectory; or trajectory through the brainstem, hypothalamus, posterior fossa, and/or venous sinuses. These factors should be taken into account when determining candidacy for operative intervention.
- On the other hand, a patient presenting with a GCS score of 14 or 15 and minimal radiographic injury may require only local wound care and close observation.
Clinical exam and radiographic features guide the extent of operative intervention. ⁵ ^, ⁸
- Limited surgery may be appropriate for a patient presenting with a small entrance wound, coupled with minimally depressed bone fragments and little or no mass effect and/or hematoma on head computed tomography (CT). Such a patient may benefit from superficial debridement. ⁹
- ∘ Craniotomy/craniectomy with targeted, limited debridement may be appropriate for a patient presenting with limited mass effect, some in-driven bone fragments, some projectile fragments, and mild to moderate cerebral edema. Only the easily accessible bone and projectile fragments should be retrieved. Aggressive adjacent brain debridement should be avoided. These patients do very well with a combination of copious intraoperative antibiotic irrigation, formal dural closure, good scalp closure, and periprocedural broad-spectrum antibiotics.
- Craniotomy/craniectomy with more extensive debridement is appropriate in the presence of significant mass effect. Space-occupying lesions should be evacuated. Debridement of necrotic brain tissue, along with safely accessible bone and missile fragments, is recommended. ⁵ ^, ¹⁰ ^, ¹¹ Deep-seated bone and missile fragments—especially in eloquent areas—should not be retrieved because this has been shown to correlate with worse outcomes. When the projectile′s trajectory traverses an air sinus, operative intervention is recommended to achieve water-tight closure of the damaged dura. ¹ ^, ⁹ This may decrease the risk of CSF fistula and abscess formation. ¹ ^, ¹²
No evidence-based recommendations address the timing of intervention. Here, pragmatism applies.
- If a significant space-occupying lesion is present, emergent surgical intervention is warranted for relief of mass effect as a life-saving measure—with the recognition that it may not change outcome.
- If findings suggesting mass effect are less compelling, it would be reasonable to monitor intracranial pressure (ICP) and manage expectantly.
- If the goal is simple wound care, it would follow that expedient intervention may diminish the risk of infection and CSF complications. ⁹ ^, ¹⁰

Preprocedure Considerations

General

Attend to the ABCs of resuscitation (airway, breathing, circulation).
Control brisk bleeding from the scalp and associated wounds with hemostats or temporary staple closure, as well as a pressure dressing. Large, isolated scalp wounds may lead to fatal blood loss.
Document entrance and exit (if present) wounds, as well as the presence of powder burns, CSF leak, and brain herniation.
Early invasive ICP monitoring is an option when unable to follow a serial neurologic exam, when the need to evacuate an observed mass lesion is uncertain, and/or when imaging suggests increased intracranial pressure. ⁹ Brain tissue oxygen monitoring may be considered as well.

Radiographic Imaging

Anteroposterior and lateral skull X-rays may provide general information regarding the presence of radiopaque foreign bodies as well as entrance and exit sites. The ease with which multiplanar CT can be obtained in most settings has largely obviated the need for this diagnostic modality.
Noncontrast CT provides the most comprehensive source of anatomic information. CT will reveal the presence of hematoma and foreign bodies—both bony and metallic—as well as information regarding the likely missile trajectory. The CT should be studied for potential violation of vascular structures.
If direct vascular injury is suspected, emergency vascular imaging may be appropriate.
- Imaging findings arousing suspicion may include: orbitofacial or pterional location; trajectory through a venous sinus or the Sylvian fissure; the presence of fragments crossing dural compartments; or the presence of a large hematoma proximate to a named vessel.
- Formal cerebral angiography not only permits diagnostic assessment but also offers the potential for intervention.
- In recognition of expediency, CT angiography may be another option in this setting. ⁹
- A single negative study does not definitively rule out injury. The development of unexplained subarachnoid hemorrhage or hematoma in the days following the initial injury may provide an indication for delayed or repeat imaging.
Magnetic resonance imaging (MRI) is generally contraindicated in the setting of a penetrating injury with metallic foreign body. However, it should be noted that most civilian ammunition—particularly pistol ammunition—is actually nonferromagnetic and, hypothetically, should not preclude MRI evaluation. Caution must be exercised with shotgun wounds as many shotgun shells now deliver steel shot (due to Environmental Protection Agency legislation regarding lead pollution). MRI may play a role in the diagnostic evaluation of penetrating injuries from wooden or nonmagnetic objects. Keep in mind that MRI is not practical in the acute setting, given the time necessary to perform the study as well as potential risks associated with transporting a critically ill patient to an often “remote” area of the hospital.
Preoperative imaging (Fig. 8.1).

Medication

Antimicrobial prophylaxis is administered. Broad-spectrum coverage, perhaps skewed toward skin flora, is appropriate in the setting of gross contamination of the wound.
Antiepileptic drug prophylaxis is initiated.
A loading dose of mannitol 20% (1 g/kg) may be given.
A type and cross-match should be performed. Coagulopathy often develops in the setting of penetrating injury due to increased tissue thromboplastin activity. Ensure availability of a range of blood products (red blood cells, fresh frozen plasma, and platelets), as well as adjunctive agents (aprotinin, desmopressin, recombinant factor VII, tranexamic acid, vitamin K, and prothrombin complex concentrates) that might become necessary perioperatively.

Operative Field Preparation

If vascular injury is suspected, ensure that appropriate supplies (microscope, aneurysm clips, microsurgical instruments, blood products) are available prior to skin incision.

**Fig. 8.1a–c** Axial CT (a) brain and (b) bone windows demonstrating a comminuted bilateral frontal bone fracture, associated with a large left frontal intraparenchymal hematoma, in-driven bone, and pneumocephalus. (c) Three-dimensional reconstructed image demonstrates the full extent of the bony injury; note that the missile is actually lodged in the extracranial space, just posterior and lateral to the depressed fracture.

Control bleeding from scalp and associated wounds. Temporary staple or suture closure may be necessary to permit preparation of the field.
Foreign bodies protruding from the head are left in place during preparation of the surgical site.
A wide area of scalp is shaved to ensure identification of entrance and exit sites, to clear superficial scalp debris, and to allow for a large cranial opening.
The surgical site is prepared with alcohol, followed by a povidone-iodine or chlorhexidine solution in the usual sterile fashion. Avoid the latter if exposed brain is present. A diluted povidone-iodine solution may be used for the preparation of large contaminated wounds.
The incision is marked and infiltrated with 1% lidocaine with 1:100,000 epinephrine. Avoid areas of exposed brain tissue.