SECTION X. Other Procedures
A Burns
1. Introduction
Burn injuries, regardless of their origin, are classified according to the depth and the extent of the skin and tissue destruction as well as the total body surface area (TBSA) involved. The degrees of burn injury with classification, tissue involvement, and appearance are shown in the following table.
A major burn is a second-degree burn involving more than 10% of the TBSA in adults or 20% at extremes of age; a third-degree burn involving more than 10% of the TBSA in adults; and any electrical burn or one complicated by smoke inhalation. A burn formula derived from the National Burn Registry estimating mortality is as follows: If the age of the patient plus the percentage of the TBSA burned exceeds 115, the mortality is greater than 80%. Additionally, from clinical observations, it is estimated that the mortality of a burn victim is approximately doubled if there is an inhalation injury sustained in conjunction with a thermal burn.
Patients who sustain full-thickness burns are seen in the operating room, probably repeatedly, for débridement and grafting. The initial assessment of the emergency patient with a burn injury is initiated as for any trauma patient and begins with airway intubation. Keep in mind that airway edema happens rapidly in a burn patient, and intubation after the edema occurs is difficult. Burn patients must have aggressive fluid resuscitation in the first 48 hours. Burns are described according to the rule of nines, which divides the body into areas of 9% or multiples thereof. For example, the head and neck combined, each arm, each leg, the posterior surface of the upper trunk, and the posterior surface of the lower trunk are each considered to be 9% of the surface area of the body. Survival is influenced by the percentage of the surface area involved, and the age of the patient.
The pathophysiologic effects of major burns on each organ system are listed in the table below.
2. Preoperative assessment
a) The burn patient requires a thorough and complete preoperative assessment. A complete medical history, including laboratory studies, and a brief physical examination with lung auscultation, assessment of chest compliance, and inspection of the neck and oral cavity to evaluate for difficulties with intubation or reintubation should be implemented.
b) There are specific data unique to the burn patient that the anesthesia provider should know: knowledge regarding the underlying trauma, the mechanism of burn (electrical, inhalation), the percentage of TBSA burned, the location of the burn sites, the area and the amount that the surgeon intends to débride, and whether the patient will undergo skin grafting during the perioperative course. The assimilation of this information affects the anesthetic plan in terms of anesthetic agents selected, appropriate monitoring, positioning, vascular access, and blood product requirements.
c) A review of prior anesthetic records can be helpful in determining the anesthetic plan. Quite often, this is possible to do because, more often than not, these patients make several trips to the operating room.
3. Pharmacologic considerations
a) Burn injury causes considerable changes in plasma protein levels, with significant consequences for the protein binding of drugs. In general, patients with burns exhibit decreased albumin and increased α 1-acid glycoprotein levels.
b) Because the pharmacologic effect is often related to the unbound fraction of a drug, alterations in protein binding can also affect the efficacy and tolerability of drug treatment in patients with burns. This alteration causes the plasma binding of predominantly albumin-bound drugs, such as benzodiazepines, phenytoin, and salicylic acid, to be decreased, resulting in an increase in the free fraction and thus a larger volume of distribution (V d) for the drug.
c) Drugs primarily bound to α 1-acid glycoprotein (e.g., lidocaine, meperidine, propranolol) have the opposite effect.
d) V d may be increased or decreased in patients with burns. In general, two factors may cause alteration in V d: changes in extracellular fluid volume and changes in protein binding.
e) Fluid loss to the burn wound and edema can decrease plasma concentrations of many drugs. After the initial resuscitation state, cardiac output increases as the hypermetabolic phase develops. This increases blood flow to the kidneys and liver with increased drug clearance. Dosage requirements may change if the drug has a small V d and a narrow therapeutic range. Overall, there is significant patient variability based on fluid status and phase of recovery.
4. Patient preparation
a) A successful anesthetic for the excision and grafting of a burn wound requires planning and preparing needed equipment. Specific anesthetic interventions should be done for these patients before their arrival in the operating room.
b) Plan preoperative anesthesia for the burn patient
(1) Warm up the operating room ahead of time, well before the patient arrives.
(2) Check on the patient’s blood status and order more blood if necessary, based on the patient’s preoperative hemoglobin and hematocrit values, the size of the burn, and the extent of the planned débridement.
(3) Have the blood in the operating room and checked before surgical débridement is initiated. This is critical in the pediatric patient.
(4) Have at least one blood warmer primed, plugged in, and turned on. If the burn is large, have two.
(5) Make sure that you have adequate intravenous access before the surgeon begins débriding the burn.
(6) Have an adequate supply of narcotics.
(7) Know whether invasive lines will need to be placed, and plan ahead of time.
(8) Have a plan, but be willing to modify it if needed.
c) Complete blood count, electrolytes, blood urea nitrogen, creatinine, glucose, urinalysis, prothrombin time, partial thromboplastin time (D-dimer or fibrin split products if disseminated intravascular coagulation is suspected), type and cross-match (number of units depends on the area to be débrided/grafted), chest radiography, and arterial blood gases (with carboxyhemoglobin if indicated) are obtained. Other tests are done as suggested by the history and physical examination.
d) Begin volume replacement with crystalloid or blood, or both, preoperatively. If the patient’s condition permits, an anxiolytic (e.g., benzodiazepine) and a narcotic may be useful preoperatively.
5. Equipment and monitoring
a) Burn patients require all the standard monitors intraoperatively. It can be challenging at times to adapt the standard monitors to the burn patient.
b) Electrocardiogram (ECG) leads are often difficult to place secondary to a lack of intact skin. It may be necessary to staple the leads or use needle electrodes on the patient to obtain an acceptable ECG tracing.
c) Ideally, blood pressure cuffs should be placed on an unaffected limb or at times, at a nonsurgical site.
d) The placement of an arterial line for blood pressure monitoring may be warranted even in the healthy patient if the planned amount of surgical débridement is extensive or if manipulation of the patient’s limbs intraoperatively limits the accuracy of noninvasive cuff readings. In large burns that are greater than 20% to 30%, invasive blood pressure monitoring should be instituted after induction, if not in place preoperatively. Rapid blood losses, the potential for hemodynamic swings, and the need to check intraoperative laboratory values all validate this requirement.
e) The standard sites for pulse oximetry placement may not be available. Alternative sites include the nose, the ear, and the cheek.
f) Any preexisting invasive monitors such as arterial line catheters or central venous or pulmonary artery catheters should be continued in the operating room.
g) Accurate temperature monitoring is essential, because burn patients can become very hypothermic intraoperatively. Temperature measurements should be obtained through an esophageal stethoscope. Skin temperature devices are highly inaccurate, and there may not be a suitable place to place one.
h) Patients with burns who are critically ill are usually transported directly to the operating room from the burn intensive care unit and vice versa postoperatively, by the anesthesia provider. These patients are usually intubated, are receiving continuous infusions of pharmacologic agents, and have invasive lines in place. Astute monitoring of the patient’s vital signs during transport is mandatory. Care must be taken while transporting the patient to not disrupt or dislodge any invasive or intravenous lines. A portable oxygen delivery system is another component of required transport equipment. Careful handling and vigilant guarding of the airway are vital. The anesthesia provider must also consider the patient’s comfort and privacy during transport. Amnestic and analgesic drugs should be administered as needed.
i) Monitors: Standard. Needle electrodes may be needed for electrocardiography. Blood pressure can be measured on the lower extremities; an arterial line or a cuff can be placed over the burned area with a sterile lubricated dressing after consultation with the burn specialist. Most patients with burns of more than 40% to 50% require an arterial line, a central line, and a pulmonary arterial catheter if they are hemodynamically unstable. Use caution in placement, and avoid burned areas.
j) Additional equipment: Blood and fluid warmers. A heated circuit and warming blanket are used. Room temperature is increased. Burn patients are poikilothermic.
k) Positioning: Various positions may be required intraoperatively, depending on the area being treated. Assess limb contractures, and stabilize fractures.
6. Airway management
a) Any acute airway problems are usually handled on admission to the burn unit. In the patient with a major burn or one who has an inhalation injury, preoperative intubation is likely.
b) In the nonintubated patient without an inhalation injury and whose airway is normal, induction and intubation of the airway can proceed as during any other anesthetic regimen (except no succinylcholine).
c) Preoperative airway evaluation is necessary as with any other patient. The anesthesia provider should exert good judgment in determining the degree of intubation difficulty. If the airway appears difficult, fiberoptic intubation should be considered or, at least, readily available.
d) In the severely burned patient who is intubated preoperatively, vigilance is required to protect the airway from accidental extubation. Loss of the airway in this patient may be impossible to regain because of edema of the airway structures.
e) Securing of such an airway can be problematic. Tape does not readily stick to burned skin. The use of soft beard straps to secure an endotracheal tube is a good option, especially if the plan is to extubate the patient at the end of the case. Cloth ties encircled around the head are frequently employed in the burn unit to secure endotracheal tubes and should not be disrupted.
7. Temperature regulation
a) Depending on the percentage of TBSA affected by the burn, temperature regulation can be problematic in the burn patient. These patients are at high risk of hypothermia development resulting from the loss of the skin’s insulating mechanisms, radiation and evaporative heat losses, and the large amount of body surface area exposure intraoperatively.
b) The temperature in the operating room should be greater than 28° C.
Intravenous solutions and skin preparations should be warmed. All methods of heat conservation should be employed while the patient is in the operating room.
c) The use of in-line Humidivents or low gas flows reduces evaporative respiratory tract heat loss.
d) Forced-air warming blankets are very effective, but their use can be limited. Over-body heating lamps can be used but need to be at a safe distance above the patient to prevent further skin burns. Plastic bags can also be used to insulate any exposed body parts not being treated surgically.
e) It is suggested that keeping a patient warm is more beneficial than rewarming. With hypothermia, vasoconstriction occurs that may curtail any later warming efforts later. It has been shown that slow rewarming postoperatively in critically ill patients with burn injuries leads to an increase in mortality. If the patient becomes hypothermic even despite the best effort put forth, the surgeon needs to be advised to stop the procedure.
8. Fluid and blood replacement
a) Surgical burn débridements may be extraordinarily bloody operations. Wound management involves removal of the burn eschar layer until brisk bleeding of the dermis is reached.
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