Maintenance

There are four basic goals of the maintenance phase of anesthesia:  

  1. Maintain required levels of unconsciousness, analgesia and muscle relaxation throughout the procedure,
  2. Provide effective cardiopulmonary stability and tissue perfusion, 
  3. Allow adjustments to the depth of anesthesia based upon the needs of the patient  
  4. Facilitate a smooth transition of the patient to the recovery phase

Anesthesia is typically maintained using inhalant anesthetics. However, it can also be maintained with a continuous infusion or intermittent administration of an injectable agent.  Also a combination of inhaled and injectable drugs can be administered simultaneously to maintain anesthesia.  

Alfaxan Multidose injectable anesthetic may be effectively used in combination with inhaled gases in partial intravenous anesthetic procedures or by itself for total intravenous anesthesia.
The depth of anesthesia must be continuously monitored and adjusted based upon the patient’s individual requirements.  Remember, only utilizing monitoring equipment to measure patient parameters is not sufficient.  Individual data points must be interpreted in light of the entire clinical picture.  This leads to informed decision-making throughout the procedure.

Complications during the maintenance phase - Despite the best planning, anesthetic complications are not uncommon.  To prevent a minor complication from escalating, it is essential to recognize it and respond quickly and correctly.

Common complications of anesthesia are hypoventilation, hypotension and cardiac arrhythmia.
Hypoventilation is an expected effect of inhalant anesthesia.  It can be estimated by observing respiratory rate and depth, and quantified using capnography. Normal end tidal carbon dioxide ranges from 35 to 40 mm of mercury in non-anesthetized patients and 40 to 50 mm in patients in a surgical plane of anesthesia.  Increases beyond these values may indicate the need for anesthetic adjustments.

Hypotension may be diagnosed by blood pressure monitoring.  Intervention includes lowering the depth of anesthesia, administering a crystalloid bolus and/or anticholinergics, vasopressors and inotropes.
  
Gas anesthesia is known to cause significant cardiac depression and vasodilation.  In a situation where the patient is insufficiently anesthetized but still exhibits symptoms of hypotension, it is possible to reduce the inhaled gas and give an injection of Alfaxan at approximately 1.0 mg/kg to increase depth of anesthesia while treating the underlying cause of hypotension.

Common anesthesia-related arrhythmias include bradycardia and ventricular arrhythmia.  These may be detected via auscultation or ECG monitoring.  
The decision to treat an arrhythmia should be based upon its severity and its effects on other hemodynamic parameters.

Anesthesia best practice:  When the procedure has concluded and the inhalant is discontinued, supplemental oxygen should be provided for at least 3-5 minutes.  During this time, observations may be made to ensure the patient can maintain normal oxygenation without it.