Note:

Mr. Jones had suffered from MG for over 6 years; therefore, he has at least one risk factor for postoperative mechanical ventilation following general anesthesia.

Pyridostigmine treatment is usually given at bedtime, as a sustained release tablet, and during the day every 3 h, beginning at 6 a.m. A cumulative daily dose of 750 mg is quickly reached. Dr. Deborah didn’t ask specifics; therefore, she couldn’t note that on the preoperative evaluation. A definite classification of the disease according to Osserman classification can’t be determined from the information given.

Furthermore, pulmonary function tests were not ordered or performed. Vital capacity of <2.9 l further increases the risk of postoperative mechanical ventilation after general anesthesia [2]. A preoperative, objective evaluation of pulmonary function should be done in MG patients.

Even when regional anesthesia is planned, informed consent for general anesthesia is necessary. In patients with MG, the additional risk of postoperative mechanical ventilation should be described in the informed consent discussion.

Benzodiazepines have a central-acting myotonic effect. The prescription for midazolam for preoperative sedation is contraindicated.

The order for a trigger-free general anesthesia is incorrect. There is no association between MG and malignant hyperthermia.

>> Dr. Mallory felt well prepared as he entered the OR that morning. His fellows had called him from the preanesthesia clinic and told him about Mr. Jones. It wasn’t every day that the anesthesiologists had an MG patient; therefore, Dr. Mallory had read up on the subject the night before. His board certification exam was a few years ago, and he noticed more and more often that his theoretical knowledge had decreased over time. “Bummer,” he thought, as he noticed that Mr. Jones was scheduled for a spinal, “I already prepared myself for general anesthesia, studied up on the muscle relaxants and monitoring the neuromuscular blockade, and now I can’t use a bit of what I learned.”

He greeted Mr. Jones; the anesthesia technician Donald already had him sitting up for the spinal anesthesia. Dr. Mallory glanced at the preanesthesia evaluation, to see what the daily dose of pyridostigmine was. “240 mg at night, then 6 × 120 mg during the day; makes a total of 960 mg,” he mumbled to himself. The prescribed midazolam was not given to Mr. Jones. Dr. Mallory had called the preoperative check-in area from home this morning to cancel the order.

After proper preparation, Dr. Mallory placed the spinal needle into the subarachnoid space at the level of L ₄ /L ₅ and injected 2.4 ml bupivacaine 0.5 % hyperbaric and 10 μg fentanyl. “Finished! You may lie down again,” he said to Mr. Jones. After 10 min, the spinal level reached T ₁₂ . That was the bad news. The good news was that the sympathicolysis had no effect on the vital signs: blood pressure was unchanged at180/90 mmHg, and the heart rate remained at 65 beats/min.

The dispersal of a sensory and motor block after intrathecal injection of a local anesthetic is not entirely predictable. An important factor is the level of the puncture [11], which was rather low in Mr. Jones. Puncture below the lordosis of the lumbar region aids caudal dispersion [12] so that changing position can influence dispersal of the local anesthetic. Therefore, Mr. Jones should be positioned in the Trendelenburg position in order to raise the level of the block.

>> Mr. Jones was almost in 30° Trendelenburg position as the surgeon Dr. Martin entered the OR. “You haven’t done a spinal, have you?” he questioned Dr. Mallory. “That’s probably not going to work. Mr. Jones has a bit of bowel in the hernia.” Then he went to scrub. “Thanks a lot for the information!” thought Dr. Mallory. The cranial dispersal of the spinal anesthesia had reached the T ₆ level, and Dr. Mallory returned the patient to the supine position. Mr. Jones’s blood pressure had decreased to 140/80 mmHg and his heart rate was unchanged. He was becoming anxious. He hadn’t understood everything, but he did pick up on the fact that the surgeon was upset about something.

The surgery began. Dr. Martin made an incision in the inguinal region, and Mr. Jones had no pain. The hernia was actually rather large, and Dr. Mallory was annoyed with himself for not obtaining more detailed information earlier. After about an hour into the procedure, Dr. Martin mobilized the hernia sac. All of a sudden, the heart rate dropped to 40 beats/min, blood pressure 90/55 mmHg.

A cholinergic crisis is triggered by an overdose of cholinesterase inhibitors. The symptoms are:

Since Mr. Jones had not received an extra dose of cholinesterase inhibitor, a cholinergic crisis can be ruled out.

>> Mr. Jones moaned because of extreme pain. Just as the surgeon Dr. Martin had warned, the spinal wasn’t sufficient. “Could you please do your job and anesthetize the patient? I can’t operate like this!” complained Dr. Martin. Dr. Mallory glanced at the surgical area: bowel loops were hanging out, and Dr. Martin looked as if he was untangling them. Mr. Jones moaned in pain again. Dr. Mallory felt sick. He must get help and quickly. He called anesthesia technician Donald, who was currently helping in the next OR. Then he gave Mr. Jones 1 mg atropine, 100 μg phenylephrine, and 200 μg fentanyl IV. The circulatory status improved immediately, but the S _P O ₂ decreased to 85 %. Dr. Mallory interrupted his preparation for induction/intubation, turned off the monitor alarm, grabbed a mask and filter from the anesthesia cart, turned on the fresh oxygen, and began to preoxygenate Mr. Jones. The S _P O ₂ increased to 96 %.

Anesthesia technician Donald entered the room. “Do you have to intubate?” he asked.

Dr. Mallory only nodded. With practiced efficiency, tech Donald prepared everything. “We can begin,” he informed Dr. Mallory. Just in the nick of time, because Mr. Jones was again agitated and moaning. As ordered by Dr. Mallory, tech Donald gave 160 mg propofol, 200 μg fentanyl, and 80 mg succinylcholine IV. After the last medication was in, Dr. Mallory shouted “Dammit!” Shortly thereafter, he intubated Mr. Jones without difficulty.

As already discussed in Sect. 17.1.2, there is no association between MG and malignant hyperthermia. There was nothing wrong with the administration of succinylcholine. However, in MG patients, the effect of succinylcholine is altered: due to a minimal number of functioning ACh receptors, the onset of effect is prolonged. Among other irregularities, an increased dose is necessary. In summary, the effect is very unpredictable.