Anesthetic Considerations for Orthognathic Surgery: RECOVERY

In: Anesthesia

26 Feb 2010

Hypotensive anesthesia

In the recovery room, the patient remains in the same position and is given oxygen through a ventimask and is monitored until the patient is able to respond to commands. During this period, the most common problems are airway obstruction and bleeding. Before discharging from the recovery room, the patient is made comfortable. If the patient is scheduled for patient-controlled analgesia, the anesthesia is started with the basal infusion and the response monitored prior to the patient leaving the recovery room. The intravenous line for patient-controlled analgesia is usually a separate line from that infusing the fluids. Once the patient is responding to commands, is able to maintain the airway, and is comfortable and not bleeding, the patient is transferred to the ward. Those with intermaxillary fixation may be transferred to an intensive care unit or a high-dependency ward if such facilities exist. Wire cutters are always kept near a patient with intermaxillary fixation in order to cut the wires and relieve any airway obstruction if such occurs.

PROBLEMS

Many problems may occur during anesthesia for orthognathic surgery. The most common problem is the disconnection of the endotracheal tube from the connectors by the surgeons assisting at the head end. Thus, the anesthetist should make sure the connections are made tight prior to handing over the head end to the surgeons. The endotracheal tube may be cut or punctured during the use of burs, which will cause a leak in the tube. Often, the leak is not severe and is noticeable only during certain positions of the head. The operation may be continued. Occasionally, if the leak is severe, the operation may have to be stopped and the tube changed. Displacement of the tube is rare but may occur if the tube is near the carina. It may enter one lung, causing a rise in the inflation pressure, a drop in oxygen saturation, and a rise in the end tidal carbon dioxide. Surgery should be stopped and the tube repositioned. If the cuff inflation of the endotracheal tube is uneven, the tube may bend to one side. With nitrous oxide diffusing into the cuff, this deviation may increase. Further, with surgeons assisting at the head end and pushing the tube, at times, the tip of the tube can impinge on the tracheal mucosa and cause an obstruction to ventilation. The end of the tube will act like a flap valve, the inflation pressure will become very high, and ultimately the ventilation will stop. If this happens, surgeons should immediately be asked to stop surgery and the tube should be repositioned.
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Occasionally, severe bleeding may occur despite hypotensive anesthesia. The bleeding may be generalized oozing from the bone and connective tissues or the surgeon may have cut one of the vessels. Usually, there is more bleeding during maxillary osteotomies than mandibular osteotomies. During maxillary osteotomies, bleeding may occur from damage to the greater palatine artery, pterygoid venous plexus, sphenopalatine artery, or maxillary artery. During mandibular osteotomies, bleeding may occur from damage to the inferior alveolar artery and vein, retromandibular vein, facial artery, maxillary artery, masseteric vessels, and the vessels supplying the medial pterygoid muscle.

The usual response to oral surgery is tachycardia due to stimulation of the sympathetics via the trigeminal nerve. However, during orthognathic surgery, bradycardia and asystole have been reported. It has occurred by activation of the trigeminovagal reflex during down fracture or sectioning of maxillary tuberosities, during maxillary osteotomies, and during the use of a channel retractor subperiosteal along the medial aspect of the mandibular ascending ramus during a mandibular osteotomy.

Pallor or cyanosis of the osteotomized segment may occur during the procedure. If that happens, the patient’s blood pressure should be raised and maintained at the preoperative resting blood pressure.

In the early postoperative period, there is always some bleeding, as stated earlier. Sometimes continuous bleeding may be seen. It may be due to a cut vessel opening up when the rises with the awakening of the patient or it may be due to improper suturing of the torn nasal mucosa.

Late postoperative complications following orthognathic surgery are cyanosis and necrosis of the skin of the tip of the nose and the sacral region. These complications are due to a combination of hypotension and pressure on the skin of these areas reducing the blood flow. Thus, special care should be taken during taping of the endotracheal tube and in positioning of the patient to prevent these problems.


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