Alleged intraoperative awareness: a report of two cases

Intraoperative awareness can traumatize those patients who experience it and result in anxiety disorders such as posttraumatic stress disorder.1 Although it occurs rarely, anaesthesiologists should examine anaesthetized patients carefully to detect its signs and try to prevent it.2–5 Most of the common causes of intraoperative awareness are the mechanical problems with vaporizers, anaesthetic machines or respiratory circuits. It has been postulated that changes in patients' blood pressure (BP) or heart rate caused by low concentrations of anaesthetics were concealed by the use of opioids under these circumstances.6 Similar situations may occur during emergence from anaesthesia if opioids are administered to reduce postoperative pain. Patients' anxiety or fear encountered during recovery, which can be magnified by the confused mental state, tends to be neglected. This distress, however, may be very serious and intense if patients confuse the memories during emergence from general anaesthesia with intraoperative awareness. We report two patients who encountered severe discomfort during recovery and asserted that they experienced intraoperative awareness. Case reports Case 1 A 69-year-old woman was diagnosed with stomach cancer and admitted for a subtotal gastrectomy. She was operated on for acute appendicitis under general anaesthesia 5 years ago. She also had ulcerative colitis and took acetic salicylic acid and prednisolone. No sedative or opioid premedication was given before surgery. When the patient arrived in the operating room, she was monitored with an electrocardiogram, a noninvasive arterial BP monitor, a pulse oximeter and a peripheral nerve stimulator. Anaesthesia was induced with thiopental 250 mg and fentanyl 100 μg intravenously. After endotracheal intubation was achieved following neuromuscular blockade, anaesthesia was maintained with sevoflurane and a mixture of oxygen and air. Concentrations of oxygen, inspired/end-tidal sevoflurane and carbon dioxide were measured with an anaesthetic machine (Primus; Drager, Lubeck, Germany) and patient monitor (Solar 8000M; GE Medical System, Milwaukee, Wisconsin, USA). The sevoflurane concentration was adjusted in the range of 2.2–3.9 vol% based on the haemodynamic response of the patient. Her vital signs were so stable during the operation with no signs of inadequate anaesthesia, such as hypertension, tachycardia, sweating and movement, that no more opioids were administered. At the end of the surgery, residual neuromuscular blockade was reversed with neostigmine mixed with atropine, and the patient's lungs were ventilated with 100% oxygen. The total anaesthesia time was 120 min. Although she did not regain consciousness completely, we removed the endotracheal tube because the patient was breathing adequately and seemed very uncomfortable with it. After observing the patient carefully for a few minutes, we started patient-controlled analgesia [(PCA) morphine 40 mg, fentanyl 1500 μg, ondansetron 4 mg, isotonic saline 64 ml, total 100 ml, continuous infusion rate 1 ml h−1, bolus 0.5 ml and lockout time 15 min] to relieve her postoperative pain and transferred her to the postanaesthesia care unit (PACU). Because she had not recovered consciousness after about an hour in the PACU, the PCA was stopped, and, thereafter, she became fully awake. After staying in the PACU for another 2 h without any particular complaint, she was transferred to a general ward. However, the next day, she insisted that she had experienced intraoperative awareness. We visited her and asked her about it. She told us that there were other patients beside her, and the ceiling light was different from the one she had seen during the induction of anaesthesia. The place she remembered must have been the PACU, not the operating room, so we explained that she had confused the two places and assured her of the adequate depth of anaesthesia during surgery. However, she disagreed with us and asserted that she was awake during surgery. She said that she would refuse to be operated on again under general anaesthesia because of the horrible experience of intraoperative awareness. Case 2 An 81-year-old woman was admitted for a subtotal gastrectomy. She had undergone a repair surgery of the knee cartilage under spinal analgesia 2 years earlier. She had a history of hypertension and diabetes mellitus and took amlodipine, candesartan and glimepride. Anaesthesia was induced with thiopental 250 mg and fentanyl 100 μg intravenously, and vecuronium 8 mg was administered. After endotracheal intubation, anaesthesia was maintained with desflurane, oxygen and air. The inspired and end-tidal concentrations of oxygen, desflurane and carbon dioxide were monitored. The desflurane concentration was changed between 4.3 and 6.0 vol% to maintain a sufficient depth of anaesthesia to prevent sympathetic responses by the patient. No additional opioids were required during surgery. The total anaesthesia time was 220 min. After the operation was over, neuromuscular blockade was reversed with neostigmine mixed with atropine, and 100% oxygen was supplied. When the patient was breathing adequately and responded to verbal commands, the endotracheal tube was removed. We started PCA (morphine 30 mg, fentanyl 1000 μg, ondansetron 4 mg, isotonic saline 25 ml, total 50 ml, continuous infusion rate 1 ml h−1, bolus dose 0.5 ml and lockout time 15 min) for the relief of pain and transferred the patient to surgical ICU (SICU). She did not regain her consciousness completely until 3 h after her arrival at SICU and occasionally complained of pain. After she became fully awake, she did not mention any discomfort except postoperative pain and was transferred to a general ward the next day. We heard that she insisted that she had experienced intraoperative awareness and visited her. She told us that she awoke from anaesthesia because of pain during the operation and had asked us to reduce her pain. She felt that she was not given enough analgesics, although a nurse had explained to her that more analgesics had been given. She must have confused SICU and the operating room based on communication with a nurse, and we gave her a full explanation to clear up any misunderstandings. However, she refused to accept our explanation and said that she would never be operated on again under general anaesthesia for fear of awareness during surgery. Discussion The subconscious recollection of intraoperative events could be excluded based on the end-tidal inhalant level and recall situation such as a different ceiling light and communication with a nurse. There was one similar case report to ours.7 A 60-year-old woman underwent a left colectomy under general anaesthesia with isoflurane and N2O. After the operation was over, she was transferred to the PACU. It was decided to keep the endotracheal tube in place for some time because the patient was very obese and had a history of obstructive sleep apnoea. Morphine was administered intermittently, and the endotracheal tube was removed after 4 h. The next day, the patient complained of awareness during the operation and refused all further operations, although the authors explained the situation. In the course of speculation about the causes of patients' confusion, we have found some similarities between our cases and this one. First, opioid-containing analgesia was started even before the patients regained consciousness fully. Second, it took the patients a few hours to become fully awake, and they complained of intraoperative awareness on the first postoperative day. Finally, all of them were probably elderly Asian women. Although the report by Ho7 did not describe the race of the patient, it was reported in Hong Kong, and she was likely to be an Asian. Considering all these facts, immediate postoperative administration of opioids, along with the patients' old age and the severe pain during a slow recovery of consciousness, could have an influence on their confusion. It might be affected by the racial differences because there was no report on white patients. Attention should be paid to discriminate between these situations and postoperative delirium, which occurs especially in older patients. Anticholinergic agents, such as atropine and glycopyrrolate, are the precipitating factors for delirium after surgery. However, our patients were alert and did not meet the criteria of postoperative delirium, which include confusions, hallucinations and cognitive disorders such as disorientation and memory disorder. Although two big awareness studies5,6 analysed multiple aspects of awareness, they did not consider discomfort during recovery. The anxiety and distress encountered during recovery from anaesthesia can be confused with intraoperative awareness and can cause patients severe psychological stress similar to real intraoperative awareness. We suggest that more attention should be paid to postoperative alleged awareness in the elderly patients who receive opioids during the recovery period.