Emergency War Surgery NATO Handbook: Part III: General Considerations of Wound Management: Chapter XV: Anesthesia and Analgesia

Anesthetic Techniques

United States Department of Defense

The three categories of anesthetic techniques are local, regional, and general.

Local Anesthesia

While local infiltration techniques should be reserved for only the most minor of injuries, they do offer a fast and effective method to clean, suture, and remove small foreign bodies in forward facilities. These techniques allow early return to duty. Lidocaine, 0.5-1.0%, is the most popular agent. All of the local anesthetics shown in Table 9 can be used satisfactorily. In a medical facility overwhelmed with casualties, there is a temptation to perform an excessive number of operations under local anesthesia. Caution must be exercised in patient selection to avoid infiltration of toxic doses of local anesthetic under such circumstances. Local infiltration is seldom satisfactory for extensive debridement required to properly manage major wounds. Table 9 lists the common local anesthetics and their dosages.

Local anesthetics can be absorbed into the systemic circulation and, in excessive doses, can cause myocardial depression, hypotension, apnea, and seizures. Seizures should be treated with a rapidly acting benzodiazepine; respiratory depression by oxygenation and ventilation; and hypotension by intravenous fluid resuscitation and use of vasopressors.

It should be remembered that life support equipment such as oxygen, ventilation apparatus, airways, laryngoscopes, endotracheal tubes, adequate suction devices and muscle relaxant paralyzing drugs are minimum requirements in the event that a patient receives an overdose of local anesthetic or has an allergic reaction. Epinephrine, steroids, benadryl, intravenous barbiturate, and benzodiazepine medication should be readily available All medications necessary to support a successful cardiopulmonary resuscitation must be available before any anesthetic is begun.

 Table 9 - Local Anesthetic Agents

Notes:

1. These are general guidelines only. The smallest total dose necessary to accomplish satisfactory anesthesia should always be used. Consider patient age, physical status, debility, etc, in determining dosages

2. Dosage limits for infiltration, epidural, and major nerve block are calculated assuming epinephrine is added to solutions. Reduce dosage by approximately 50% if using plain solutions.

3. Plasma levels vary widely within anatomical site of nerve block or infiltration. Consult standard texts for specific limits,

4. Only single-dose, preservative-free preparations should be used for subarachnoid or epidural administration.

5. Do not exceed 600 mg in the adult.

Regional Anesthesia

Regional anesthesia can be a valuable and efficient technique in combat surgery. In a mass-casualty situation, the busy anesthetist may be able to safely administer more than one anesthetic at a time, with monitoring delegated to lesser-trained personnel. Shortly after establishment of the block, the anesthetist's attention can usually be directed intermittently elsewhere without jeopardizing the safety of the patient. The advantages of regional anesthesia include the absence of nausea, vomiting, aspiration, and other pulmonary complications, and decreased bleeding.

Major nerve blocks are particularly appropriate for isolated extremity injuries. Regional anesthesia is not normally satisfactory for intra-abdominal exploration. The anesthetic level required to block sensation from visceral manipulation in such cases is usually dangerously high, necessitating both circulatory and ventilatory support.

Subarachnoid or epidural anesthesia is contraindicated in patients whose intravascular volume is inadequate or uncertain. It may be administered cautiously when fluid losses have been corrected by appropriate resuscitative measures. The sympathetic block from a subarachnoid or epidural anesthetic may be advantageous for the patient with a vascular repair of the leg, while a brachial plexus or stellate ganglion block may provide the same benefit to those with vascular injuries of the arm or hand. Another advantage of these techniques is that they often provide long-acting postoperative analgesia without the use of depressant medications.

The intravenous regional or Bier block is a very useful technique for extremity injuries because of its ease of administration, reliability, and relative safety. It is not a satisfactory technique if the limb has multiple puncture wounds or jagged foreign bodies are embedded. Postoperative analgesia is usually of only brief duration.

Table 9 lists commonly available anesthetic agents and dosage forms. The maximum recommended dosage limits shown must, be tempered by modifying factors such as patient size, condition, and site of incision.

General Anesthesia

Anesthetic drug requirements in the critically injured patient will usually be much less than under more normal conditions. Often intraoperative management is primarily a matter of achieving hemodynamic stability, optimizing oxygenation, and supporting ventilation. If the patient is in profound shock, oxygenation, fluid resuscitation, and muscle relaxation may be the only anesthesia administered. Such patients rarely have recall of intraoperative events. In addition, blood flow is preferentially distributed to the heart and brain in the hypotensive patient, which may further decrease anesthetic requirements.

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Operational Medicine 2001

Health Care in Military Settings

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