Japanese Journal of Clinical Oncology

INTRODUCTION

Stress from surgery disturbs patients' sleep (1-3). Even minor surgery like inguinal hernia repair can disrupt sleep with a reduction of total sleep and REM sleep (4). Major surgery curtails sleep even further. REM sleep on the first and second post-operative night is virtually eliminated (5,6). Knill et al. (7) reported that the REM sleep reappeared thereafter and even increased to a level greater than the pre-operative amount.

In the post-operative period, hypoxemia is another well-known threat (8-10). The hypoxemia in this stage is predominantly caused by a corruption of the airway patency, i.e. obstructive apnea (11,12). The obstructive apnea is often observed in the patients during REM sleep after major surgery (13-15).

Glossectomy and laryngectomy are major surgical procedures. These procedures are stressful to patients and may not only simply disrupt their sleep, they simultaneously interfere with the air flow in the upper airway because of surgery and post-operative edema. Hence, we suspected that after glossectomies and laryngectomies, patients could show disturbance as described, and have studied their breathing during the perioperative nights using an apnea monitor.

METHODS

With approval from the ethics committee of the National Cancer Center Hospital, 16 patients, aged 63 ± 8 years, ASA 1-2 (ASA is the risk grade for patients by the American Society of Anesthesiologists), gave informed consent for the study. Patients with carcinoma of the tongue, base of the tongue or mesopharynx who underwent glossectomy with microsurgical transfer of the rectus abdominis or antero-lateral thigh musculocutaneous flap, and patients with hypopharyngeal carcinoma or laryngeal carcinoma who underwent pharyngo-laryngo-esophagectomy with free jejunum transfer or laryngectomy, were subjects for the study. The patient characteristics are shown in Table 1. Simple partial glossectomy was excluded from the study. General exclusion criteria were pre-existing symptoms of neurological, cardiac or respiratory disease, including excessive daytime sleepiness.

Table 1. Patient characteristics

Number of patients	16
Weight (kg)	61.6 ± 8.0
Height (cm)	167.0 ± 5.1
Laryngectomy (n)	9
Glossectomy (n)	7

Data are the mean ± SD.

Anesthesia

Anesthesiawas induced with thiopental (5 mg/kg), vecuronium (0.1 mg/kg). It was maintained with sevoflurane and nitrous oxide. Muscle relaxant was not administered after the induction. An arterial line was placed for repeated blood analysis. Fluid was administered in milliliters at the rate of three times the body weight (in kilograms) per hour. Blood transfusion was given when the blood lost was over 900 g.

An epidural catheter was inserted before the induction of anesthesia at T11-12 or L1-2 intervertebral space to control post-operative pain at the location from where the free skin flap was taken. Three to four milligrams of morphine hydrochloride in a vehicle of 5 ml saline were administered through the epidural catheter about one hour before termination of surgery. Five to fifteen milligrams of pentazocine and 50 mg of flurbiprofen axetil were administered intravenously when the patients required further analgesics.

Surgery

Surgery comprised glossectomy with mandibular resection, radical neck dissection and free flap reconstruction from the abdomen or lateral thigh; pharyngo-laryngo-esophagectomy with radical neck dissection and free jejunum transfer; or laryngectomy with radical neck dissection (16). Eight patients who received either pharyngo-laryngo-esophagectomy or laryngectomy received tracheostomies at the end of the surgical procedure. The rest were kept intubated over the night of the operation and extubated the next morning. For both of the patients kept intubated and tracheostomized, 1 mg of midazolam hydrochloride per hour was used for sedation until the next morning. The success of the free skin flap was judged tentatively two weeks after the operation.

Apnea Monitoring

All patients were attached to an apnea monitor (Apnomonitor II, Chest Co., Tokyo, Japan) three days prior to the operation, one day before the operation, on the day of the operation, two days after, and on the fourth day after the operation. The Apnomonitor was to detect air flow (thermistor on airway) and air flow sound (microphone). The built-in pulse oximeter detected arterial oxygen saturation (17). The air flow sensor thermistor was positioned at the naris [Fig. 1(A)]. When the patient received a tracheostomy after the glossectomy or laryngectomy, a custom-built thermosensor was put at the tracheostoma [Fig. 1(B)]. When the patient was kept intubated, we made another custom-built thermosensor which could be connected to the intratracheal tube [Fig. 1(C)]. The thermosensor detects changes in temperature as low as 1°C. The microphone sensor was put on the throat to detect the air flow turbulence in the trachea. The microphone sensor detects sound as low as -65 dB. A built-in microcomputer in the Apnomonitor analyzes no air flow when input sound changes within 9.5 dB. A band filter was used for the microcomputer to detect only the sounds from 200 to 1000 Hz in order to suppress heart sounds and carotid pulsations. Apnea was identified when the thermosensor and nose sensors detected no airway temperature change and no airway sound simultaneously for a period of 10 s (18).

Figure 1. The air flow sensor thermistors at the naris (A), at the tracheostoma (B) and the built-in air flow thermistor in an air circuit (C). The air flow sensor at the tracheostoma and the built-in air flow thermistors are custom made for this study.

The probe of the built-in pulse oximeter was put on the second finger to monitor arterial blood oxygen saturation. The Apnomonitor records the data from the pulse oximeter every three seconds as well as the occurrence of apneic episodes. Routine daily arterial blood gas measurement correlates well with pulse oximeter readings. A decrease in SpO₂ (saturation of oxygen in pulse oximeter) of <90% for >60 s was considered significant. All of the patients had a baseline SpO₂ value of >95%. The period of monitoring was from 8:00 p.m. to 6:00 a.m. the next morning.

The Patients' Level of Comfort

The patients' level of comfort during the study nights was evaluated by a blinded anesthesiologist the next day by means of a visual analog scale. The imaginably most dreadful feeling in the night was counted as 0 mm. The imaginably most peaceful feeling in the night should be counted as the 100 mm point on the scale.

Statistics

The comparison of the values between the extubated and the tracheostomized group was calculated with the Cochran Cox test or Student's t-test where adequate. SpO₂ changes within the same surgical group of patients were also analyzed by the Wilcoxon Signed Rank Test. A P value of <0.05 was considered statistically significant.

RESULTS

Sixteen patients completed the study where respiration was recorded for a total of five days. All anesthetic and surgical procedures were uneventful. The patients underwent glossectomies or laryngectomies (including pharyngo-laryngo-esophagectomies) with an average duration of 507.6 ± 68.4 min. They were administered 3.56 ± 0.30 mg of morphine during the operation through the epidural catheter. These measurements and the patients' characteristics were not statistically different in groups of glossectomies and laryngectomies. They did not receive any other narcotics during the operation. After surgery, however, the patients received 6 mg of morphine with a vehicle of 20 ml saline per day continuously through the epidural catheter up to three days. We did not use patient-controlled analgesia during the study.

Figure 2 shows the change in apneic episodes in a survey of all the patients. The number of apneic episodes per hour (Apneic Index) increased greatly after the glossectomy, pharyngo-laryngo-esophagectomy or laryngectomy. The increase on the second and fourth post-operative days was significant and more than four-fold.

Figure 2. Apnea record of all the patients for the study. Sleep apnea was frequently observed on the second and fourth operative nights, and second and fourth post-operative nights. The value of the Apnea Index of each day was compared with that three days prior to surgery. **P < 0.01 in paired Student's t-test.

In Fig. 3, the two groups, delayed extubation versus tracheostomy, are separated for analyses. The glossectomy is classified in the delayed extubation group, the pharyngo-laryngo-esophagectomy and laryngectomy are in the tracheostomy group. Several patients with delayed extubation increased their Apnea Index more than 20-fold, while patients with tracheostomy only increased the same index by less than five times. Changes for patients with delayed extubation were significant, while the changes for tracheostomized patients were not.

Figure 3. Apnea record of two patient groups: the patients who were tracheostomized, and patients who were kept intubated and later extubated. The value of the patients who were not tracheostomized was compared with that of the patients who were tracheostomized. **P < 0.01 in unpaired Student's t-test.

Similarly, patients with delayed extubation after glossectomy showed a significant decrease in pulse oxymetry (Fig. 4). This change occurred on both the second and fourth post-operative days. In patients with tracheostomy, there were no significant changes in oxygenation.

Figure 4. Mean hemoglobin saturation of oxygen measured by pulse oximeter. All recorded values were averaged to calculate the mean, except when we considered that the changes were caused simply by the patient's movements during the monitoring and excluded from the average calculation. The value of the patients who were not tracheostomized was compared with that of the patients who were tracheostomized. *P < 0.05, unpaired Student's t-test.

In our evaluation of patient comfort, patients with tracheostomy were much more comfortable in the post-operative period than those with delayed extubation (Fig. 5).

Figure 5. Comfort of perioperative sleep. The value of the patients who were not tracheostomized was compared with that of those who were tracheostomized. **P < 0.01 in unpaired Student's t-test.

DISCUSSION

A high value of the Sleep Apnea Index was seen in the patients after extubation. Before the extubation, it was not seen. Although we suspected there would be frequent central apnea before the extubation because the remaining anesthetic agents, epidural morphine and midazolam hydrochloride may all have participated in factors for central sleep apnea, our suspicion was unfounded. It is noticeable, therefore, that central apnea was found to be negligible after glossectomies, pharyngo-laryngo-esophagectomies and laryngectomies, as reported in other operations (5,6). With assurance of airway and secured sleep with midazolam, all the patients slept well during the night following surgery.

The post-operative sleep apnea after the glossectomy was obstructive sleep apnea. The results coincide with previous reports (11,12). The glossectomy patients who were extubated the next morning showed an acute rise in sleep apnea frequency and a decrease in mean values in the pulse oximeter. There were frequent temporary hypoxemias after the extubation in the glossectomy patients. In the questionnaire on the patient's level of comfort, glossectomy patients reported that they had a dream, a part of which was dreadful. Because they did not receive any sedation on the first operative night and during the days after, it was possible that their REM sleep resumed (7). Study with electroencephalography to elucidate their sleep is preferable to maintain the patient's post-operative condition better in future.

To keep a free flap viable, the posture of the patients is important. The free flap is fed by the blood circulation through the anastomoses of feeding arteries and draining veins. The patient's posture, when it interferes with the blood circulation, causes a failure of the tissue transplantation. It is preferable that the patients keep a posture in which the local circulation is at its best. In seven extubated patients, we found reports of two skin flaps that had failed, while none out of four with pharyngo-laryngo-esophagectomy had a failed free jejunum flap. We need to pursue the relationship between their nightmare and the skin flap failures. To keep the best posture further maintained, a longer more strict sedation may be beneficial for the patients undergoing glossectomies.

We conclude that patients with extensive head and neck surgery need at least a comfortable first and second post-operative night with close monitoring to keep them free from discomfort, and the free flap in the best possible condition.

Acknowledgment

We acknowledge the kind suggestions and provision of information by Dr Jacob Rosenberg.

References

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Received September 4, 1998; accepted November 19, 1998
For reprints and all correspondence: Toshiyuki Saito, 1236-7 Kagawa, Chigasaki, Kanagawa 253, Japan. E-mail: toshis{at}nms.ac.jp

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