Does perioperative opioid infusion increase postoperative opioid requirement?

OBJECTIVES

Opioids are the cornerstone therapy for the optimal pain management. Perioperative opioid infusion is accused of causing acute opioid tolerance, especially as the postoperative opioid requirement increases in time to provide efficient analgesia. It is debatable whether there is a difference between opioid agents regarding tolerance development. We aim to compare the effects of morphine, remifentanil and alfentanil when infused intravenously during the perioperative period.

METHODS

Sixty patients undergoing elective major abdominal surgery were randomized into four groups. The four groups obtained the following treatments: saline 5 cc iv bolus and 10 cc/h infusion for induction and maintenance in Group C, remifentanil infusion 0.25 µg/kg/min following 1 µg/kg iv bolus in Group R, alfentanil infusion 0.50 µg/kg/min following 10 µg/kg iv bolus in Group A, and morphine infusion 0.02 mg/kg/h after 0.1 mg/kg iv bolus in Group M. Meperidine 10 mg/cc iv patient-controlled analgesia was used postoperatively, and total meperidine consumptions were recorded. VAS scores and side effects were recorded during postoperative 48 hours.

RESULTS

VAS scores in Group M were found to be significantly lower than in Group C at the 1st postoperative hour. Twenty-four hour total meperidine consumption in Group R and Group M were significantly lower than in Group C. No statistical difference was found between groups regarding the incidence of nausea and vomiting.

CONCLUSION

Our study indicated that infusions of morphine, alfentanil and remifentanil administered to patients undergoing major abdominal surgery did not cause acute opioid tolerance. In contrast, infusion of morphine and remifentanil reduced postoperative opioid requirement.

Airtraq, LMA CTrach and Macintosh Laryngoscopes in Tracheal Intubation Training: A Randomized Comparative Manikin Study

OBJECTIVE

Training students on simulators before allowing their direct contact with patients is well accepted. There is no clinical or manikin-based simulation study in the literature comparing tracheal intubation with Airtraq, laryngeal mask airway (LMA) CTrach and Macintosh laryngoscopes performed by medical students having no prior intubation experience.

METHODS

After obtaining written informed consents, 123 participants were included in the study. The participants were asked to intubate the manikin five times with each device randomly. After all the participants had completed their fifth intubations, the measurements were performed. The primary outcome variables were the first-attempt success rate and the time for a successful intubation, while the secondary outcome variables were to determine the scores of dental trauma, the difficulty visual analogue scale and the optimization manoeuvres.

RESULTS

The LMA CTrach group revealed a significantly higher number of intubation attempts. The mean time for a successful intubation was the longest in the LMA CTrach group (17.66±8.22 s, p<0.05). Students defined the Airtraq as the easiest to use and the Macintosh laryngoscope as the most difficult device to use and learn. Dental trauma severity was significantly lower in the Airtraq group than in the other groups (p<0.05), and it was found to be 0 in 81.1% in the Airtraq group. The head extension optimization manoeuvre rate was significantly higher with the Macintosh laryngoscope than with the Airtraq laryngoscope (p<0.05).

CONCLUSION

This study, in which different types of laryngoscopes were compared, revealed that the Airtraq laryngoscope has advantages, such as shorter intubation duration, less additional optimization manoeuvres, less dental trauma intensity and is easier to learn compared with the LMA CTrach and Macintosh laryngoscopes.

Perioperative Effects of Different Narcotic Analgesics Used to Improve Effectiveness of Total Intravenous Anaesthesia

OBJECTIVE

We aimed to evaluate the depth of anaesthesia, perioperative haemodynamics, postoperative pain scores, analgesic consumption in patients receiving remifentanil- or alfentanil-based total intravenous anaesthesia for single-level lumbar discectomy.

METHODS

Seventy patients undergoing discectomy were enrolled in the study. Patients were intravenously administered an initial bolus dose of 2 mg kg(-1) propofol and 10 mcg kg(-1) alfentanil or 1 mcg kg(-1) remifentanil, followed by 6 mg kg(-1) h(-1) propofol and either 1 mcg kg(-1) min(-1) alfentanil or 0.25 mcg kg(-1) min(-1) remifentanil infusion. Bispectral index (BIS) values, mean arterial pressure, heart rate, end-tidal carbon dioxide and oxygen saturation were recorded. Postoperative pain scores at 0, 30 and 60 min were measured and recorded with additional opioid requirements.

RESULTS

Postoperative pain scores at 0 and 30 min, total analgesic consumption and requirement for additional analgesics were significantly high in the remifentanil group. After the first hour, the pain scores were not significantly different. Mean arterial blood pressure was significantly low at 45 and 60 min preoperatively in the remifentanil group. In the remifentanil group, heart rate at 15, 30, 45, 60 min were significantly lower than those in the alfentanil group. BIS values of the two groups were not significantly different at any measurement time point. BIS values of remifentanil group at 30, 45, 60, 90 and 180 min significantly increased compared with those at 15 min.

CONCLUSION

Alfentanil provided more stable BIS and haemodynamic values preoperatively and less opioid consumption, along with lower pain scores, during the early postoperative period compared with remifentanil in patients undergoing single-level discectomy.

The Effects of Desflurane and Propofol on the Release of Thyroid Hormones in Euthyroid Patients Undergoing Elective Lumbar Discectomy

OBJECTIVE

In this study, we aimed to compare the effects of desflurane and propofol on the release of thyroid hormones in euthyroid patients undergoing single-level lumbar discectomy.

METHODS

The study group included 21-65-year-old American Society of Anesthesiology (ASA) I-II euthyroid 40 patients undergoing elective single-level lumbar discectomy. They were randomly divided into 2 groups (n=20). In the maintenance of anaesthesia, Group D received desflurane inhalational anaesthesia and remifentanil infusion, and Group P received propofol and remifentanil IV infusions. Four blood samples for the determination of plasma levels of free triiodothyronine (FT3), free thyroxine (FT4) and thyrotropin (TSH) were collected 5 min before and 60 min after the induction of anaesthesia and 60 min and 24 h after the surgery.

RESULTS

Plasma TSH levels in both groups reached the highest levels at the first postoperative hour and returned to the preoperative levels 24 hours after the surgery. Regarding plasma FT3 levels, there were no significant differences within and between groups. There were no significant differences in plasma FT4 levels within the patients of Group P, but in Group D, FT4 levels reached its peak in the first hour of anaesthesia induction and returned back to preoperative levels 24 hours postoperatively (p<0.05).

CONCLUSION

Further studies are needed to confirm our findings and evaluate patients with thyroid gland pathologies.

Does the Method and Timing of Intravenous Ketamine Administration Affect Postoperative Morphine Requirement After Major Abdominal Surgery?

OBJECTIVE

Single intravenous bolus administration and postoperative or perioperative infusions are the most preferred methods of ketamine. Nevertheless, there is no clear explanation on the ideal ketamine administration method. In this study, we aimed to compare the effects of the most common ketamine administration methods and administration time on postoperative opioid consumption.

METHODS

Fifty-two patients undergoing colectomy for colon cancer were randomly assigned into four groups. Group 1 was the control group. Group 2 received only a single intravenous bolus dose of 0.5 mg kg(-1) ketamine at induction. Group 3 received 0.5 mg kg(-1) intravenous ketamine bolus at induction and perioperative ketamine infusion at a rate of 0.25 mg kg(-1) h(-1). Group 4 received a bolus of 0.5 mg kg(-1) intravenous ketamine at induction and perioperative and postoperative ketamine infusion at a rate of 0.25 mg kg(-1) h(-1). Postoperatively, visual analogue scale pain scores, side effects, and morphine consumption were recorded.

RESULTS

There was no statistically significant difference in postoperative pain scores. Total morphine consumption was found to be significantly lower in Group 4 compared to the other groups (p=0.03, p=0.004, p=0.03, respectively). During the 1(st), 2(nd), and 4(th) hours in the postoperative period, patient-controlled analgesia morphine consumption was significantly lower in Group 4 compared to the control group (p<0.01).

CONCLUSION

Preoperative single-bolus dose or intraoperative low-dose ketamine infusion does not decrease postoperative morphine consumption; however, per- and postoperative 48-hour ketamine infusion has a significant effect in decreasing morphine consumption without decreasing the incidence of side effects in patients undergoing major abdominal surgery.

The Professional Experience of Anaesthesiologists in Proper Inflation of Laryngeal Mask and Endotracheal Tube Cuff

OBJECTIVE

Cuffs inflated to inappropriately high pressures cause ischemia, reducing tracheal mucosal blood flow, while cuffs inflated at lower pressure than necessary give rise to inadequate ventilation, aspiration of gastric contents, or extubation due to air leakage. In this study, we aimed to investigate the effect of the experience of anaesthesia staff on endotracheal tube and laryngeal mask airway cuff inflation.

METHODS

The study included 348 elective patients scheduled to undergo surgery under general anaesthesia, with 34 anaesthesia technicians, 16 anaesthesia residents, and 12 anaesthesiologists with different years of professional experience. The participants were told to inflate the cuff balloon with air to the level of the pressure that was appropriate for them. No information was provided to the participants about the values of the cuff pressure pending the completion of all measurements. After placement of the laryngeal mask airway and endotracheal tube, the success of the procedure was checked by monitoring square-wave capnograph tracing and thoracoabdominal motion. Each participant performed the procedures on three patients, and the mean cuff pressures were measured.

RESULTS

There was no significant correlation between duration of experience of technicians, residents, and experts in using laryngeal mask airway pressure (r=-0.192/p=0.278, r=0.225/p=0.402, r=-0.476/p=0.118, respectively) and endotracheal tube (r=-0.306/p=0.079, r=-0.060/p=0.826, r=-0.478/0.116, respectively).

CONCLUSION

It has been concluded that professional experience does not contribute to achieving normal cuff pressure without monitoring. Introduction of the cuff manometer into routine anaesthesia practice will be useful, irrespective of anaesthesiologists' experience.

Effects of Esmolol on the Prevention of Haemodynamic Responses to Tracheal Extubation after Craniotomy Operations

OBJECTIVE

The aim of this study was to evaluate the effects of esmolol infusion on the prevention of haemodynamic responses to tracheal extubation in patients undergoing elective craniotomy.

METHODS

With approval from the Medical School Ethics Committee at Marmara University and the patients' written consent, 30 patients between 20-65 years of age undergoing elective craniotomy were randomly placed in either the Group Esmolol (n=15) or the Group Control (n=15). Anaesthesia was induced with 5-7 mg kg(-1) thiopental sodium, 1 μg kg(-1) remifentanil, and 0.1 mg kg(-1) vecuronium bromide iv, and was maintained with 1 MAC sevoflurane in oxygen-air mixture (50:50) and 0.25 μg kg(-1) min(-1) remifentanil infusion. At the end of the operation, patients inhaled 100% oxygen after the discontinuation of the anaesthetic agents. For Group Esmolol, 5 min before extubation 2 mg kg(-1) esmolol in 50 mL was infused over 10 min (0.2 μg kg(-1) min(-1)), while for Group Control, 50 mL saline was infused over 10 min. The quality of extubation was evaluated with a 5 point scale, recording heat rate, systolic, diastolic, and mean arterial pressures before infusion, 1 min after infusion, during extubation, and at 1, 3, 5, and 10 min after extubation.

RESULTS

In the esmolol group, systolic, diastolic, and mean arterial pressures, as well as heart rate, decreased significantly after esmolol infusion and were significantly lower than in the control group after extubation (p<0.05). The ratio of patients with an extubation score of one was significantly higher in the esmolol group than in the control group (p<0.05).

CONCLUSION

We concluded that 2 mg kg(-1) esmolol infusion before extubation can prevent hypertension and tachycardia caused by extubation in patients undergoing elective craniotomy.

Histopathological effects on epidural tissue of bolus or continuous infusions through an epidural catheter in ewes

This study was performed to evaluate the histopathological effects of epidural drug injection given either by intermittent bolus or continuous infusion through a catheter on epidural tissue. Fourteen ewes received intermittent bolus injections of morphine with bupivacaine, or a bolus of the same drugs followed by continuous infusion for 5 days. After 5 days, histopathological examination of the epidural space revealed mild to moderate inflammatory changes, and focal fibrosis surrounding the catheter in all ewes. The similarity of the inflammatory reaction in the control and drug treated groups seems to indicate that neither intermittent bolus or continuous infusion after a bolus dose caused histopathological changes in the epidural space beyond that caused by the catheter itself.

The in vitro effects of isoflurane, sevoflurane, and propofol on platelet aggregation

We studied the in vitro effects of sevoflurane, isoflurane, and propofol anesthesia on platelet function. Thirty patients undergoing minor surgical procedures were divided into three groups (n = 10 each). Induction of anesthesia was achieved by using 5 mg/kg thiopental i.v., and 0.1 mg/kg vecuronium i.v. was used for muscle relaxation. Anesthesia maintenance was provided by sevoflurane in the first, isoflurane in the second, and propofol infusion in the third group with 70% N2O in O2. Hemoglobin, hematocrit, thrombocyte count, prothrombin time, activated partial thromboplastin time, international normalized ratio, arterial pH, von Willebrand factor, viscosity, platelet aggregation, and bleeding time were measured 1 h pre-, intra-, and postanesthesia. There was no difference among the platelet aggregation ratios of the pre-, intra-, and postoperative periods in the isoflurane group. The aggregation ratios in the sevoflurane and propofol groups were significantly reduced at intraoperative periods compared with preoperative values. Diminished aggregation values were also found 1 h postoperatively compared with the control values in the sevoflurane and propofol groups. We conclude that, in patients with a bleeding tendency during the intra- and early postoperative period, isoflurane may be preferred as a general anesthetic.

IMPLICATIONS

In our study, using vacuum-operated tubes, we demonstrated that sevoflurane and propofol had a significant inhibitory effect on intraoperative and early postoperative platelet aggregation, whereas isoflurane had no effect. Therefore, isoflurane may be preferred as a general anesthetic in patients with a clinically relevant bleeding tendency.