A comparison of two constant-dose continuous infusions of remifentanil for severe postoperative pain

Effect of Low Dose Remifentanil on Postoperative Pain Relief and Heart Rate Variability in Post-Anaesthesia Care Unit

Objective

Several reports have shown the negligible adverse effects of low-dose remifentanil on the autonomic nervous system. We propose that the administration of low-dose remifentanil would be beneficial without adverse respiratory and hemodynamic effects. This study aimed to examine the effects of low-dose remifentanil on postoperative pain relief and heart rate variability (HRV) after surgery.

Methods

In total, 20 patients, who underwent breast cancer surgery, were analysed for HRV in the post-anaesthesia care unit (PACU). A sedative dose of remifentanil was continuously infused if patients experienced pain while in PACU. The remifentanil infusion dose was determined by achieving analgesia with no adverse effects on hemodynamics and/or respiration. Variables of low-frequency power, high-frequency power and low-frequency power/high-frequency power ratio were measured before and after the administration of remifentanil. Pain score was expressed as the numeric rating scale (NRS) from 0 to 10.

Results

The mean dosage of remifentanil administered as a continuous infusion was 0.029±0.0042 μg kg^-1 min^-1. After remifentanil administration, the value of the NRS decreased from 4.2±2.9 to 2.7±2.6. In addition, the value of high-frequency power increased from 35.6±14.3 to 49.4±3.0.

Conclusion

The continuous infusion of low-dose remifentanil may reduce post-operative pain scores and trigger the relative activation of the parasympathetic nervous system in post-surgical patients. This indicates that continuous infusion of low-dose remifentanil may be a useful option for postoperative pain relief in cases where postoperative pain control proves inadequate even with the application of regional block technique.

Continuous postoperative infusion of remifentanil inhibits the stress responses to tracheal extubation of patients under general anesthesia

PURPOSE

The study aimed to assess the combined effects of parecoxib with three different doses of remifentanil and its effect on the stress and cough responses following tracheal extubation under general anesthesia.

METHODS

A total of 120 patients with American Society of Anesthesiologists (ASA) scores of I or II, undergoing selective thyroidectomy with total intravenous anesthesia (propofol-remifentanil) and tracheal intubation, were randomly allocated to be treated with an intravenous injection of parecoxib and a continuous infusion of remifentanil at 0.1 μg/kg/min (R1), 0.2 μg/kg/min (R2), 0.3 μg/kg/min (R3), or an isotonic saline injection (the control group). Hemodynamic vital signs, emergence time, extubation time, sedation-agitation scale (SAS) score, pain visual analog scale (VAS) score, occurrence of coughing, and side effects were recorded before surgery and during the peri-extubation period. The vital signs included blood pressure (BP), heart rate (HR), respiratory rate (R), and peripheral arterial oxygen saturation (SPO₂).

RESULTS

BP, HR, the occurrence rate of coughing, and extubation awareness decreased with the dose of remifentanil, and the differences among the groups were significant (P < 0.05). Emergence and extubation time increased with the dose of remifentanil, and the differences among the groups were significant (P < 0.05). The occurrence rates of respiratory depression and bradycardia in group R3 were significantly higher than those in other groups (P < 0.05). SAS and VAS were lowest in group R3, and the differences among the groups were significant (P < 0.05). BP, HR, SAS, and VAS increased with time in the remifentanil groups.

CONCLUSION

The combined use of parecoxib and a moderate dose of remifentanil can effectively suppress the stress and coughing responses during the peri-extubation period. The appropriate quantity of remifentanil was found to be 0.2 μg/kg/min, as this dosage caused no side effects.

Effect of remifentanil on consumption of sevoflurane in entropy monitored general anesthesia

BACKGROUND

Monitoring of anesthetic depth is important for successful general anesthesia. It is well known that entropy or BIS monitoring assisted titration of anesthetic drugs decreases their consumption. This study evaluated the effect of remifentanil on consumption of sevoflurane during entropy monitored general anesthesia.

METHODS

Patients were randomly assigned to two groups. The R group was administered 0.1 µg/kg/min of remifentanil and inhaled sevoflurane, while the S group was administered only inhaled sevoflurane. Anesthesia was maintained using sevoflurane with nitrous oxide, and entropy was monitored. In both groups, the concentration of sevoflurane was adjusted to keep the state entropy (SE) value between 40 and 60. End-tidal sevoflurane concentration (ET), entropy value, systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were measured at 5 minute intervals, during a 25 minute period after intubation, skin suture and the end of surgery.

RESULTS

ET was significantly lower in the R group than the S group. There were no significant differences in entropy value between R and S groups.

CONCLUSIONS

Entropy monitored titration of sevoflurane with remifentanil administration decreased ET with stable hemodynamics.

Continuous infusion of two doses of remifentanil immediately after laparoscopic-assisted vaginal hysterectomy

Background

We evaluated the effect and safety of the immediate postoperative continuous infusion of remifentanil at two doses in patients undergoing laparoscopic-assisted vaginal hysterectomy (LAVH) with alfentanil-based patient-controlled analgesia (PCA).

Methods

The study enrolled 50 ASA physical status 1 or 2 patients scheduled to undergo LAVH. Anesthesia was maintained with sevoflurane-remifentanil-air. At the last skin suture, the sevoflurane was discontinued, and patients were randomized to receive remifentanil 0.05 µg/kg/min (group I) or 0.1 µg/kg/min (group II). PCA was started at the time of eye opening and response to a verbal command. In the recovery room, we monitored the mean arterial blood pressure (MAP), heart rate (HR), respiratory rate (RR), SpO₂, and bispectral index (BIS) at 5-minute intervals. Thirty minutes after starting PCA, the remifentanil was discontinued. Pain was assessed using a visual analog scale (0 = no pain; 100 = the worst possible pain) at 0, 5, 10, and 30 minutes after stopping the remifentanil infusion.

Results

The eye opening time, BIS, MAP, and HR did not differ significantly between the two groups, and pain scores were similar between the two groups. Respiratory depression (SpO₂ < 90% or RR < 8/min) did not occur in group I but did occur in three patients in group II.

Conclusions

Continuous remifentanil infusion (0.05 µg/kg/min) immediately postoperatively with alfentanil-based PCA had a similar effect as a 0.1 µg/kg/min infusion with respect to pain control without side effects. However, special attention must be given to respiratory depression.

Comparison of remifentanil and fentanyl for postoperative pain control after abdominal hysterectomy

PURPOSE

In this randomized, double-blind study, we investigated the analgesic efficacy and side effects of continuous constant-dose infusions of remifentanil after total abdominal hysterectomy and compared it to fentanyl.

MATERIALS AND METHODS

Fifty-six adult female patients scheduled for elective total abdominal hysterectomy were enrolled in this study. Patients were randomly assigned to two groups according to fentanyl (group F, n=28) or remifentanil (group R, n=28) for postoperative analgesia. Patients in group F were given fentanyl intravenously with an infusion rate of fentanyl 0.5 microg/kg/hr; group R was given remifentanil with an infusion rate of remifentanil 0.05 microg/kg/min for 2 days. Pain intensity at rest, occurrence of postoperative nausea and vomiting (PONV), dizziness, pruritus, and respiratory depression were assessed 1 hr after arrival at the post-anesthesia care unit, at 6; 12; 24; and 48 hr post-operation and 6 hr post-infusion of the study drug. Pain was evaluated by using visual analogue scale (VAS; 0-10). The time that patients first requested analgesics was recorded as well as additional analgesics and antiemetics.

RESULTS

There were no significant differences in VAS, time to first postoperative analgesics, and additional analgesics between the 2 groups. The incidences and severities of PONV and opioid related side effects were not different between the groups; however, there were 3 episodes (10.7%) of serious respiratory depression in group R.

CONCLUSION

Continuous infusion technique of remifentanil did not reveal any benefits compared to fentanyl. Furthermore, it is not safe for postoperative analgesia in the general ward.

Remifentanil for tracheal tube tolerance: a case control study

We assessed the minimal remifentanil dosage required for tracheal tube tolerance in awake and spontaneously breathing patients after major abdominal surgery. Forty postoperative patients received remifentanil 0.1 microg.kg(-1).min(-1), which was reduced in steps of 0.025 microg.kg(-1).min(-1) every 30 min. Respiratory response subscore of comfort scale (CSRR), Ramsay sedation scale (RSS), visual analogue scale (VAS), respiratory rate, and minute ventilation were recorded. Spontaneous respiration with no or little response to ventilation (CSRR 2) in co-operative, oriented and tranquil patients (RSS 2) was defined as the main outcome and study endpoint. Thirty-one patients (77.5%) reached a CSRR 2 and RSS 2 with remifentanil 0.025 microg.kg(-1).min(-1) and nine patients (22.5%) required remifentanil 0.05 microg.kg(-1).min(-1). Analgesia was sufficient in all patients (VAS = 30). Remifentanil 0.025-0.05 microg.kg(-1).min(-1) achieves satisfactory tracheal tube tolerance in awake and spontaneously breathing patients.

Remifentanil patient-controlled analgesia following cardiac surgery

BACKGROUND

Remifentanil is increasingly used as a component of cardiac anaesthesia. Following cardiac surgery remifentanil is often substituted for alternative opioids on the intensive care unit. We were interested to evaluate postoperative continuation of remifentanil in the form of remifentanil patient control analgesia (RPCA) for those patients who received intraoperative remifentanil. The objectives of this study were to assess the safety, efficacy and feasibility of the RPCA.

METHODS

Ten patients who received an intravenous infusion of remifentanil perioperatively for coronary artery bypass graft surgery (CABG) had their remifentanil infusion converted to RPCA following extubation on the intensive care unit. Remifentanil patient control analgesia delivered an initial background infusion consistent with the infusion rate at extubation and with a bolus facility of 50 microg administered over 5 min followed by a 5-min lockout. Data collection included sedation and pain scores, respiratory rate, arterial blood gases, number of successful/unsuccessful attempts and the background infusion rate for each subject over a period of 12 h following extubation.

RESULTS

The data from nine male and one female patient were analyzed by using SPSS11 for Windows. During the study period the patients achieved adequate pain control and made more RPCA attempts at lower background infusion rates. No episodes of apnoea, SpO(2) less than 95% or a rise in PaCO(2) greater than 6.5 kPa were observed.

CONCLUSION

Remifentanil patient control analgesia with a background infusion was effective and safe for postoperative pain relief in this group of spontaneously breathing ICU patients following cardiac surgery.