Emergency anesthesia: What should we do? (Proceedings)


Emergency anesthesia: What should we do? (Proceedings)

Aug 01, 2011

The risk of anesthesia is higher in emergency cases compared with elective cases. Most of these patients are compromised and this increases the danger of anesthesia, especially in cases when there is no time to optimize the condition of the patient before anesthesia. Some of these cases are performed at night and the increased risk may be related to inadequate personnel help during this time. The personnel may also be tired as a result of the long day resulting in inattentiveness to problems.

Emergency cases are those that involved diseases or injury that pose an immediate risk to an animal's life or long term health. Some of these cases will need anesthesia. Cases of note in small animal practice include: acute diaphragmatic rupture, gastric dilatation-volvulus, fracture repair due to trauma, septic abdomen, hemoabdomen, blocked urethra, ruptured urinary bladder and C-section.

When these cases are presented, oxygen supplementation and fluid therapy should be instituted immediately while the initial assessment is being done. Pertinent blood work should be done following the initial examination. The most important problems that will complicate anesthesia should be identified and stabilization should be done before anesthesia.

Preoperative preparation

Emergency cases can have one specific problem or a combination of different problems. The cardiovascular compromise is a common problem in emergency cases. They can have hypovolemia, dehydration, shock, and arrhythmias. Fluid resuscitation should be performed in these animals. With continuous bleeding, the goal of fluid resuscitation should be to maintain a mean arterial pressure (mmHg) in the 60s. Arrhythmias can be present in animals involved in vehicular accident, patients with electrolyte imbalances, and in gastric dilatation-volvulus. Arrhythmias are usually controlled with lidocaine.

The following are problems that should be identified, managed, and corrected before anesthesia:
     1. Pneumothorax:
        Perform thoracocentesis once or twice. If signs of respiratory compromise persist, chest tube should be placed before anesthesia.
     2. Hemothorax:
        If the hemothorax results in respiratory compromise, thoracocentesis should be performed and blood aspirated from the pleural cavity.
     3. Head trauma:
        The goal of therapy is to maintain cerebral perfusion. This can be achieved by optimizing mean arterial pressure (fluid therapy) and reducing intracranial pressure. For fluid therapy, isotonic crystalloid solutions like lactated Ringer's, 0.9% NaCl, or Normosol are usually suitable. Hypertension and overhydration should be avoided. Do not use crystalloid solution with dextrose unless the patient is hypoglycemic. Mannitol (20%) and 7.5% hypertonic saline are indicated in patients with deteriorating neurologic signs. These preparations can worsen cerebral hemorrhage. Colloids can be also be used to decrease cerebral edema and increase cerebral perfusion. The use of corticosteroids (methyprednisolone sodium succinate and dexamethasone sodium phosphate) is controversial.
        Supplemental oxygen should be provided.
     4. Hyperkalemia, acidosis, dehydration, and uremia
        These are related to ruptured urinary bladder. Hyperkalemia increases the risk of anesthesia. Hyperkalemia and dehydration should be corrected before anesthesia.
     5. Shock
        Emergency patients in a state of shock should be treated before anesthesia. Crystalloids and colloids are administered to restore vascular volume. If there is an infection or if there is a suspicion of infection, an antibiotic should be given. Oxygen supplementation should be done routinely.

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