2. Preoperative assessment
a) Burn patients require 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 burn patients that anesthesia providers should know, including 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.
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 α1-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 (Vd) for the drug and possibly increased duration of action.
c) Drugs primarily bound to α1-acid glycoprotein (e.g., lidocaine, meperidine, propranolol) have the opposite effect.
d) Vd may be increased or decreased in patients with burns. In general, two factors may cause alteration in Vd: 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 Vd 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 into the operating room.
b) Plan preoperative anesthesia for the burn patient.
(2) Check on the patient’s blood status and order more blood and blood products 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 pediatric patients.
(4) Have at least one blood warmer primed, plugged in, and turned on. If the burn is large, have two available.
(5) Make sure that you have adequate intravenous (IV) access before the surgeon begins débriding the burn.
(6) Because of hypermetabolism and pharmacologic tolerance that occurs, narcotic requirements may be extreme.
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 crossmatch (number of units depends on the area to be débrided or 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.
5. Equipment and room preperation
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 a 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%, TBSA invasive blood pressure monitoring should be instituted after induction, if not already 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, ear, and 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 IV 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 ECG. 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.