To the best of our knowledge, this study was the first to assess the characteristics of postoperative sleep quality in patients with HFS after MVD surgery during the early postoperative period. The patients were in the general surgical wards, and it was found that their nocturnal sleep after MVD surgery was severely disturbed relative to their preoperative (baseline) nocturnal sleep in the hospital. POP and PONV were verified as the main causes of the patients’ PONSD. The administration of analgesic and antiemetic treatment using sufentanil, ketorolac, and tropisetron through IV-PCA reduced fragmented sleep, but patients felt more exhausted upon waking.
The patients experienced significant PONSD during the first 3 postoperative days compared with their preoperative baseline, with more mid-sleep waking and movements, shorter sleep duration, extended sleep latency, and decreased sleep depth. Several studies have shown that patients after craniotomy have disrupted sleep, from the early postoperative period to more than one year after surgery. For example, patients with acromegaly after transsphenoidal surgery had worse subjective sleep quality in the first 3 postoperative months, compared with patients with nonfunctioning pituitary adenomas.8 Huang et al.9 reported that the sleep quality of patients who underwent a glioma resection more than one year previously was worse than that of normal adults. Arık et al.7 found that patients in the neurosurgical intensive care unit who had received elective open-brain surgery experienced reduced sleep quality during the first 3 postoperative days. In addition, patients who underwent a craniotomy for pineocytoma had disturbed sleep latency and duration during a follow-up of 10.7 to 52.1 months, compared with patients after lumbar discectomy.10
In the present study, the patients in the control group considered POP to be the main cause of PONSD in the early postoperative period. This is consistent with previous findings.3 It was reported that subjects with chronic pain are 17 times more likely to suffer from sleep disturbance compared with pain-free individuals.15 MVD is a posterior fossa surgery that tends to cause greater intensive pain than supratentorial surgery.16 In the present study, the second most prevalent cause of PONSD was PONV, afflicting 70.0% of the HFS patients, who stated that it severely disrupted their nocturnal sleep on the first postoperative day. A similar rate of PONV was reported in patients within 24 hours after MVD surgery, despite the use of intraoperative prophylactic ondansetron.17
In the present study, the patients of the control group also suffered moderate or mild sleep impairment due to emotional reasons, such as worries about illness, missing relatives or homesickness, and boredom. However, the intensity of POP and PONV overwhelmed the effect of the emotional factors in disrupting nocturnal sleep. Our present results are not in accord with the findings of a questionnaire study conducted more than one month after surgery by Zhang et al.,8 whose patients had acromegaly, in whom disturbed sleep quality was associated with emotional problems (e.g., anxiety, depression, and disease stigma).
In the present study, to manage POP and PONV effectively and concomitantly assess the effect on sleep quality, the 18 patients in the intervention group received a combination of sufentanil, ketorolac, and tropisetron through IV-PCAs. As the most effective opioid analgesic known, sufentanil is considered appropriate to manage the POP of neurosurgical patients, because it preserves cognitive function and brain relaxation.18 Ketorolac is a potent IV nonsteroidal anti-inflammatory drug (NSAID), which is necessary to limit the side effects of opioids after craniotomy, while providing patients with effective pain relief.19 In addition, an antiemetic in combination with analgesics via PCA has been widely accepted as a successful approach toward reducing nausea and vomiting.20 Tropisetron was chosen in this study due to its ability to decrease PONV in patients with HFS after MVD, as it is recommended as first-line therapy for the prevention of acute nausea and vomiting.14
When compared with the control group, on postoperative days 1 and 2 the patients given the intervention (sufentanil, ketorolac, and tropisetron by IV-PCA) experienced less fragmented sleep, due to fewer mid-sleep waking and movements (e.g., tossing and turning). Since the ward’s environmental factors were held relatively stable during the 3 nights, and the psychological factors of the 2 groups were similar, this means that the less fragmented sleep of the intervention group was most likely associated with the treatment.
Studies have shown that sleep quality benefits from sufficient control of POP. For example, patients treated with opioid analgesic achieved adequate relief of chronic pain21 and POP, 22 and significant improvement in sleep quality. Intravenous ketorolac to reduce pain intensity was also associated with improved sleep quality.23 In the present study, the analgesic and antiemetic effects of the intervention were not directly measured. However, the efficacy of sufentanil and ketorolac for reducing POP after posterior fossa surgery has been documented, as well as the effect of tropisetron on PONV after MVD.14,19,24
An unexpected finding of this study was the low scores for feeling rested upon waking that the patients in the intervention group reported on postoperative days 2 and 3. Yet, their sleep quality (reflected by sleep fragmentation, duration, latency, and depth) did not change significantly day-by-day over postoperative days 1 to 3. A previous study reported similar results, that patients after gynecologic surgery treated with opioid via epidural catheter achieved excellent pain control, but also profound sleep impairment.25 Opioid use has been suggested to cause disrupted sleep and fatigue by influencing sleep hygiene and sleep architecture.26 Another study showed through polysomnography that IV administration of morphine led to a shift in sleep architecture to lighter stages, by reducing slow-wave and rapid eye movement (REM) sleep; these are generally associated with restorative processes in the body.27 NSAIDs were reported to increase the number of waking and reduce slow-wave and REM sleep, and sleep efficiency, by inhibiting prostaglandin synthesis, suppressing nighttime melatonin levels, and changing body temperature.28 Moreover, opioid analgesics are associated with high rates of PONV, which adversely influences postoperative sleep quality.19
This study had several limitations. First, this was a non-randomized trial, and the 2 groups were not equal in size. We considered it unethical to randomize patients, because of the invasiveness, cost, and side-effects of the sufentanil, ketorolac, and tropisetron treatment. Patients were apportioned to the groups based on their informed willingness to receive the postoperative treatment. Secondly, this study did not evaluate the effect of the treatment on POP and PONV, and it remains unknown if the patients in the intervention group achieved adequate analgesia or relief from PONV. Third, this was a single-center study, with only 48 patients enrolled. Larger randomized controlled trials are required to verify the outcomes. Fourth, the circadian rhythm and the exact amount of daytime sleep was not investigated. Thus, this study has significant inherent limitations when generalizing the findings.