The chainsaw kicked back and cut him a second mouth

A 36-year-old man was referred to the Nagano Red Cross Hospital in Japan with facial injuries from chainsaw kickback.

Kickback is the most notorious way a chainsaw injures its user. If the moving chain at the upper part of the tip of the bar touches the wood, or something else, it can grab, and the saw is thrown violently up and back in an arc towards the person holding it. That arc ends at the head and face.

On arrival his blood pressure was 100/60, his pulse 60 and his oxygen saturation 99% on room air. The cut had laid open his right eyelid, the inner corner of his right eye, his cheek and his jaw, and the wounds were bleeding steadily from veins. The cut through the cheek went all the way into his mouth, and to the team it looked like a second mouth.

FIG 1the bones beneath the cutCT scan · CC BY 4.0

A CT scan showed that the saw had gone through bone as well as skin. The right frontal bone of the forehead, the right cheekbone, the maxilla, the bone of the upper jaw, and the mandible, the lower jaw, were all broken. There was no fracture of the base of the skull, no air inside the skull and no injury to the neck. He could open his mouth about 3 centimetres, although it hurt.

The wounds had to be repaired urgently under general anaesthetic. That meant first getting a breathing tube into his windpipe, and this is where the injury made things dangerous.

His anaesthetist listed three risks. Blood in the mouth and throat could make it hard to see the vocal cords and pass the tube. The hole through his cheek meant that the usual way of breathing for a patient with a mask, by sealing it over the face and squeezing a bag, might not work, because the air would leak out through the wound. And with fractures all through the middle of his face, it was uncertain whether it was safe to pass anything through his nose, the route normally used to give extra oxygen during a difficult intubation.

The answer to the first two risks was to intubate him awake. Under light sedation with a short-acting opioid, remifentanil, he kept breathing for himself and kept his own airway open while the tube went in. His throat and larynx were numbed with a lidocaine spray. The tube went through the mouth rather than the nose, and the anaesthetist used a video laryngoscope, a blade with a camera at its tip, to see past the blood.

The answer to the third risk was the wound. Instead of giving oxygen through the nose, the anaesthetist passed a thin suction catheter into the “second mouth” and ran oxygen through it at 10 litres a minute throughout. The view of the larynx was poor and there was blood around it, but the tube went in on the second attempt. His oxygen saturation stayed at 99 to 100% the whole time, and he did not inhale any stomach contents.

FIG 2kickback, the wound, and the airwayoriginal diagram

Once the tube was in, he was put fully to sleep and the surgeons repaired the lacerations. The operation took 106 minutes, and he lost only about 20 millilitres of blood.

Twelve days after the first operation he had a second operation to set his broken right lower jaw and fix it with plates and screws, an open reduction and internal fixation.

He went home on the 21st day after the first operation, with no complications.

The report, written by his anaesthetist, is about getting him safely through those first minutes, and it does not include photographs of how his face healed or describe the long-term result for his eye and his facial nerve.

Most injuries of the face and jaws come from road accidents and assaults. Chainsaw injuries to the face are uncommon, and the author found very few reports of them. When they do happen, they typically cause deep soft-tissue cuts, sometimes with tissue torn away, along with fractures of the facial bones and damage to the teeth, which is the pattern this man had.

Awake intubation is the approach recommended by current guidelines whenever a difficult airway is expected, because the patient goes on breathing and protecting their own airway until the tube is safely in place. The author cites success rates of 88 to 100%, and evidence that a video laryngoscope does about as well for it as a flexible bronchoscope, with an advantage when there is blood in the airway. With low-flow oxygen during awake intubation, between 12 and 16% of patients see their oxygen saturation fall to 90% or below. Here, with oxygen running through the wound, his never fell.

The injury itself is largely preventable. Chainsaw safety guidance is consistent: modern saws have a chain brake designed to stop the chain when kickback happens, the tip of the bar should not be used to cut, the saw should be held firmly with both hands and kept below shoulder height, and users should wear a helmet with a face shield or visor, eye protection and cut-resistant clothing.

A 36-year-old man’s chainsaw kicked back into his face, cutting his right eyelid, the inner corner of his eye, his cheek and his jaw, opening his cheek into his mouth like a second mouth and breaking his forehead bone, cheekbone and both jaws. To get a breathing tube in for surgery, his anaesthetist kept him awake and breathing, numbed his throat, used a video laryngoscope to see past the blood, and, because his nose was not safe to use, ran oxygen through a catheter in the cheek wound. The tube went in on the second try with his oxygen never falling, the wounds were repaired with almost no blood loss, his jaw was fixed on day 12 and he went home on day 21. The most dangerous moment after a face injury is often not the repair but the airway, and the best fix is the one that uses what the injury has left.