Supplementation with dexmedetomidine decreases consumption of morphine, improves analgesic effects and subjective sleep quality without an increase in adverse effects in elderly patients after open abdominal surgery.

Opioids and non-opioids analgesics such as such as non-steroidal anti-inflammatory drugs (NSAIDs), ketamine and nefopam are the mainstays for achieving postoperative analgesia, but contraindications and safety concerns limit their widespread use. The use of these drugs is limited in elderly who have a higher incidence of cerebral, cardiovascular and postoperative neuropsychological events. Dexmedetomidine, a highly selective α-2 receptor agonist, is used as an alternative and shows some advantages in the management of pain. Studies have shown that the use of dexmedetomidine for acute pain after surgery can decrease the opioid consumption and improve analgesic effects, but the interpretation of results needs utmost care. Firstly, data were collected from studies that enrolled younger patients rather than elder ones. Also, the safety outcomes were not studied in detail in the majority of patients. It was also reported that infusion of a high dose of dexmedetomidine produces sedation and lowers heart rate and systolic blood pressure. The sedative dose of dexmedetomidine also inhibits the ventilatory response to hypercapnia and hypoxia in healthy volunteers. Therefore, safety remains a significant concern for the use of dexmedetomidine for achieving analgesia.

Rationale behind research:

The previous studies have indicated that the infusion of low dose dexmedetomidine improves sleep quality in elderly patients in the intensive care unit (ICU) after surgery, but evidence for explaining this aspect are still lacking. So, this study was organised to evaluate the effects of dexmedetomidine in improving sleep parameters in postoperative patients. 

Objective:

The present study intended to determine the effects of dexmedetomidine in combination with morphine on sleep quality, analgesia and safety outcomes in elderly patients after open abdominal surgery. 

Study outcomes:

• Patient demographic characteristics were studied at baseline
• The primary outcome was an evaluation of 72-hour morphine consumption, which can be explained as cumulative morphine consumption from the end of anaesthesia until 72 hours after surgery
• Secondary outcomes included evaluation of NRS pain scores, consumption of morphine, NRS score of sleep quality, and use of flurbiprofen axetil at several time-points after surgery
• Other outcomes included the evaluation of complications occurring within 30 postoperative days, the percentage of admission in the intensive care unit, the length of stay in the hospital after surgery, and 30-day mortality

Time Points:  4, 12, 24, 48, and 72 hours 

Outcomes:

Baseline: There were no significant differences observed at baseline

Study outcomes:

• A reduction in the 72-hour morphine consumption was observed in the DEX group as compared to CTRL group {median 39.0 mg [37.3, 41.0] vs. 49.0 mg [45.5, 50.0] [95% CI -10.0, -6.0], P<0.001} respectively.  {Fig 2.}

Fig 2. Cumulative consumption of morphine at different time points after surgery

• There was a significant decrease in the intensity of pain within 48 hours (P<0.001 at 4, 12 and 48 hr, P = 0.007 at 24 hours) and an increase the subjective quality of sleep (P = 0.031 & P<0.001 during the night of surgery and first night after surgery, respectively) in the DEX group as compared to control group.

• No significant differences were achieved in the incidence of 30-day complications, mortality and the rates of adverse events in both groups

The present study indicated that the combined use of dexmedetomidine and morphine for PCIA could reduce morphine consumption in elderly patients after open abdominal surgery.  Combination of dexmedetomidine and morphine significantly improves analgesic effects & sleep quality and also decreases the occurrence of PONV, without increasing the risk of adverse effects. The dose or infusion rate of dexmedetomidine also varies widely when used for postoperative analgesia. In the present study, the rate of dexmedetomidine infusion was set at 2μg/h (i.e., approx. 0.02–0.04 μg/kg/h according to the body weight of enrolled patients).  A lower background infusion rate was favored due to its effectiveness in reducing opioid consumption, and its expected duration of dexmedetomidine infusion was 72 hours in the abdominal surgery. Infusion of low-dose dexmedetomidine (at a rate of 0.1μg/ kg/h) during the night also influence sleep structure (by decreasing stage N1 sleep, increasing stage N2 sleep and sleep efficiency) and subjective sleep quality. Infusion of dexmedetomidine improved sleep quality postoperatively during the first night of surgery.  The results were comparable with the results of the previous studies.  Polysomnography and its effects on sleep efficiency and architecture were not determined in the present study. Dexmedetomidine administered by patient-controlled intravenous analgesia can also aid in the improvement of postoperative outcome. The incidence of complications was lower in the DEX group after surgery.  The results of the study did not show any differences in the occurrence of side effects. There is a need for further trials with large sample size, to elucidate the results in the geriatric patients.