|Year : 2015 | Volume
| Issue : 1 | Page : 114-123
Ultrasound-guided transversus abdominis plane block versus dexmedetomidine infusion in open ovarian cystectomy: Analgesic efficacy and effect on stress response
Khaled M Maghawry MD 1, Ayman A Rayan2, Alaa S El-Kateb1
1 Department of Anesthesia, Faculty of Medicine, Ain Shams University, Cairo, Egypt
2 Department of Anesthesia, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||10-Feb-2014|
|Date of Acceptance||02-May-2014|
|Date of Web Publication||25-Mar-2015|
Khaled M Maghawry
Department of Anesthesia, Faculty of Medicine, Ain Shams University, PO Box 11591, Cairo
Source of Support: None, Conflict of Interest: None
Ultrasound (US)-guided transversus abdominis plane (TAP) block has been proven to be an effective method of providing postoperative analgesia in laparotomy. Dexmedetomidine has sedative, analgesic, sympatholytic, and amnestic properties. In the present study, we evaluated the analgesic efficacy and the attenuation of stress surgical response of US-guided TAP block in comparison with dexmedetomidine infusion in patients undergoing open ovarian cystectomy in a randomized, double-blinded clinical study.
Patients and methods
A total of 60 patients were randomly assigned into two groups (30 in each) to be administered, before skin incision, either a combination of general anesthesia with a US-guided TAP block (TAP group), or an intraoperative intravenous infusion of dexmedetomidine (DEX group). In the DEX group, loading dose of 1 μg/kg of dexmedetomidine was infused over 10 min, followed by infusion of 0.2-0.6 μg/kg/h. Measurements included hemodynamics, stress hormones, pain score, time of first analgesia, and amount of pethidine during the first 24 h postoperative.
In the DEX group, there was a significant decrease in heart rate (HR) at 45, 60, and 90 min after surgical incision in comparison with preoperative HR. In the TAP group, there was a significant decrease in HR at 60 and 90 min after surgical incision in comparison with preoperative HR. In the DEX group, there was a significant decrease in mean arterial pressure at 30, 45, 60, and 90 min after surgical incision in comparison with preoperative mean arterial pressure. The DEX group had shown a statistically significant increase with regard to change in the blood level of stress hormones 12 and 24 h postoperative in comparison with the preoperative values. There was a highly significant increase in postoperative pethidine supplementation in the DEX group than in the TAP group. There was a significant difference with regard to time of the first postoperative request of analgesia in the DEX group than in the TAP group.
In open ovarian cystectomy, US-guided TAP block was comparable to dexmedetomidine infusion with regard to intraoperative hemodynamic stability and opioid requirement without change in stress response hormones. However, TAP block provided superior analgesia when compared with dexmedetomidine infusion up to 24 h postoperatively.
Keywords: analgesia, dexmedetomidine, ovarian cystectomy, pain score, stress response, ultrasound-guided transversus abdominis plane block
|How to cite this article:|
Maghawry KM, Rayan AA, El-Kateb AS. Ultrasound-guided transversus abdominis plane block versus dexmedetomidine infusion in open ovarian cystectomy: Analgesic efficacy and effect on stress response. Ain-Shams J Anaesthesiol 2015;8:114-23
|How to cite this URL:|
Maghawry KM, Rayan AA, El-Kateb AS. Ultrasound-guided transversus abdominis plane block versus dexmedetomidine infusion in open ovarian cystectomy: Analgesic efficacy and effect on stress response. Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2021 Oct 24];8:114-23. Available from: http://www.asja.eg.net/text.asp?2015/8/1/114/153952
| Introduction|| |
Ovarian cystectomy is a moderate surgical procedure, after which patients may suffer from substantial postoperative discomfort and pain  . These patients require multimodal postoperative pain management regimens that facilitate effective analgesia with minimal side effects  . The provision of high-quality postoperative analgesia is of great importance to facilitate early ambulation and avoidance of postoperative complications  .
The pain experienced by patients after abdominal surgery is initiated by an important key stimulant, which is the abdominal wall incision  . The lateral abdominal wall is formed of three muscle layers, the external oblique, the internal oblique, and the transversus abdominis, and their fascial sheaths, whereas the central abdominal wall includes the rectus abdominis muscles and its fascial sheath. The nerves that supply the anterior abdominal wall pass through the neurofascial plane between the internal oblique and the transversus abdominis muscles  .
Analgesia can be provided to the parietal peritoneum, skin, and muscles of the anterior abdominal wall by a type of regional anesthesia technique known as transversus abdominis plane (TAP) block  . Ultrasound (US)-guided TAP block can be used as a method of multimodal analgesia reducing postoperative pain and perioperative opioid consumption, while decreasing the adverse events from opioids, such as sedation, nausea, vomiting, respiratory depression, and ileus  .
Dexmedetomidine is an effective and highly selective α2 -adrenoceptor agonist with sedative, analgesic, sympatholytic, and amnestic properties  . The sedating and analgesic effects of dexmedetomidine are due to stimulation of postsynaptic α2 -adrenoreceptors. Stimulation of α2 -adrenoreceptors inhibits adenylate cyclase activity, leading to decrease in central nervous system (CNS) sympathetic outflow in a dose-dependent manner  , which reduces norepinephrine output at various sites in the CNS, in particular the locus ceruleus. The locus ceruleus, along with many other sites in the brain, is known to have a role in the control of ventilation, sleep modulation, and make dexmedetomidine have an analgesic effect best described as opioid-sparing  .
The stress response is a collecting item given to a sum of hormonal and metabolic changes that follow injury or trauma. This is a part of the systemic reaction to injury that includes a wide range of endocrinal, immunological, and hematological effects  .
Monitors that process electroencephalography are widely used to predict both the loss and recovery of consciousness and assess the level of sedation and hypnosis during surgery  . Bispectral index (BIS) is derived from a bispectral analysis of the electroencephalography signal recorded over the forehead using a proprietary algorithm to assess the depth of anesthesia, specifically its hypnotic component  .
Therefore, we conducted the present study to evaluate the analgesic efficacy and the attenuation of stress surgical response of US-guided TAP block in comparison with dexmedetomidine infusion in patients undergoing open ovarian cystectomy.
| Patients and methods|| |
This randomized, double-blinded, clinical study was carried out after obtaining approval by the Hospital Ethics Committee and written informed consent from the patients in Prince Salman Hospital in the Kingdom of Saudi Arabia from January 2013 to October 2013. We examined 60 female patients of American Society of Anesthesiology (ASA) physical status I and II, aged 20-50 years, scheduled to undergo an elective open ovarian cystectomy.
Patients were randomly assigned according to computer-generated randomization to be administered either a combination of standard general anesthesia with a US-guided TAP block (TAP group), which was carried out before skin incision, or standard general anesthesia with an intraoperative administration of intravenous loading and maintenance intravenous infusion of the dexmedetomidine (DEX group), also before making an incision on the skin. The anesthesiologist administering general anesthesia was blinded to the performance of TAP block and type of infusion during surgery.
Patients were excluded if there was a history of allergies against amino amide local anesthetics, coagulopathy, patients receiving medical therapies that may result in tolerance to opioids, infection at the needle insertion site, patients who had a difficulty to understand the study protocol, or prolonged surgery time more than 90 min.
For a duration of 30 min before the induction of anesthesia, all patients were premedicated with intravenous midazolam 0.02 mg/kg after insertion of a 20-G peripheral intravenous cannula, and administration of 500 ml lactated Ringer's solution was started. Upon arrival to the operating room, standard monitoring (Aisys, Datex-Ohmeda Inc., a General Electric company, doing business as GE Health Care, Madison, Wisconsin, USA) was applied. Five-lead electrocardiograph to monitor the heart rate (HR), noninvasive blood pressure, and oxygen saturation were continuously monitored, together with monitoring of BIS (Aspect Medical System Inc., and are registered in USA, EU and other countries 194-0068 3.01). Intravenous lactated Ringer's solution infusion 6-8 ml/kg was started.
All patients underwent standard anesthetic technique after 5 min of preoxygenation in the form of intravenous administration of fentanyl 2 μg/kg, ondansetron 0.1 mg/kg, dexamethasone 0.1-0.2 mg/kg, and propofol 1-2 mg/kg till loss of verbal response. Endotracheal intubation was facilitated by the use of cisatracurium 0.15 mg/kg. Anesthesia was maintained by 1 minimum alveolar concentration (MAC) sevoflurane in oxygen/nitrous oxide flow (FiO 2 32%). Adequate muscle relaxation was maintained by 0.05 mg/kg of cisatracurium every 30 min. Increments of fentanyl 1 μg/kg were administered when there were signs of inadequate analgesia (e.g. increase in noninvasive blood pressure 20% greater than baseline blood pressure and/or tachycardia more than 90/min for 10 min). The lungs were mechanically ventilated using volume-controlled mode to maintain normocapnia (end-tidal CO 2 30-35 mmHg).
After 10 min intubation, bilateral US-guided TAP block using Sonosite M-Turbo US device and 5-12 MHz linear transducer (Sonosite, Bothell, Washington, USA) was performed in the TAP group. After draping the needle insertion site, the probe was placed transversely on the level of the right anterior axillary line between the 12th rib and the iliac crest, and the external oblique, internal oblique, and transversus abdominis muscles were visualized. A 21-G 90 mm Facette tip needle and an injection line (Polymedic by tenema, Z.I. des Amandiers, France) was inserted medial to the probe by the in-plane technique and advanced in a lateral direction. When the tip of the needle reached the TAP between the internal oblique and transversus abdominis muscles, US imaging, ensuring no puncture of peritoneum or visceral organs injury, and also a negative aspiration, was carried out, and then 15-20 ml bupivacaine (2.5 mg/ml) was administered under direct ultrasonographic guidance, certified by an oval-shaped hypoechoic fluid pocket at TAP with real-time US imaging. The contralateral block was performed equally. This was associated with intravenous infusion of 50 ml of 0.9% normal saline with the same rate of dexmedetomidine infusion in the other group to confirm that the anesthesiologist administering general anesthesia was blinded to the type of the group. Skin incision was made in the allowed 15 min after the TAP block.
After 10 min intubation in the DEX group, loading dose of 1 μg/kg of dexmedetomidine diluted in 10 ml of 0.9% normal saline infused over 10 min, and then followed by infusion rate of 0.2-0.6 μg/kg/h (200 μg dexmedetomidine diluted in 48 ml of 0.9% normal saline injection for a final concentration of 4 μg/ml) according to hemodynamic status and BIS monitoring.
Approximately 20 min before the end of surgery, top-up doses of cisatracurium were stopped and intravenous infusion of paracetamol 15 mg/kg over 15 min was administered. At the end of the surgery, intravenous infusion was stopped in both the groups, and the residual of neuromuscular blocker was antagonized with neostigmine 0.04 mg/kg and atropine 0.02 mg/kg. After extubation, patients were transferred to the postanesthesia care unit (PACU) to be observed for 1 h for postoperative monitoring of hemodynamics and time to first rescue analgesia, which was pethidine 0.5 mg/kg intramuscularly administered on demand, with maximum dose of 1 mg/kg intramuscularly administered every 6 h for the first 24 h.
Hemodynamics [(HR, mean arterial blood pressure (MAP)] and oxygen saturation before the induction of anesthesia were taken as baseline values. BIS reading after intubation was taken as baseline. Stress response was assessed by measurement of serum level of cortisol and norepinephrine preoperative (baseline reading), intraoperative, and postoperative.
Intraoperative measurements included hemodynamics (HR, MAP) and BIS readings, at baseline and every 15 min till the end of the surgery, and stress hormones (serum level of cortisol and norepinephrine) preoperatively, after skin incision and at skin closure. In addition, total amount of rescue fentanyl was administered if there were signs of inadequate analgesia.
Postoperative measurements included stress hormones (serum level of cortisol and norepinephrine) immediately in PACU, 12 and 24 h postoperatively, and pain intensity score at 1, 3, 6, 12, and 24 h.
The primary outcome measure in this work was total 24-h pethidine consumption as rescue analgesia postoperatively. Secondary outcome measures included time to first request for pethidine and pain intensity.
Pain intensity was assessed as the verbal numerical rating scale (VNRS: 0, no pain; 10, the severest pain imaginable) at arrival to the recovery room (time 0) and at 1, 3, 6, 12, and 24 h postoperatively. Every assessment of VNRS was carried out by a blinded interviewer, and pain was scored under two conditions: at rest (VNRSr) and at coughing (VNRSc). When the VNRSr was greater than 4 in the recovery room, pethidine 0.5 mg/kg intramuscularly as a rescue analgesic was administered. After being transferred to the ward, the patient was managed with a standard protocol including injection of pethidine 0.5 mg/kg intramuscularly on demand with a maximum dose of 1 mg/kg intramuscularly every 6 h for the first 24 h. The time to first rescue analgesia and total amount of recues pethidine at the recovery room and ward were recorded for the first 24 h.
The sample size was based on data from the pilot study, a calculation based on 0.05 and a power of 80% yielded. A sample size of 25 patients per group used a two-tailed test assuming a difference in postoperative pethidine requirements of 50 mg and SD of 20. A total of 30 patients per group were included to replace any dropouts.
The statistical analysis was performed using a standard SPSS software package version 17 (SPSS Inc., Chicago, Illinois, USA). Data were expressed as mean ± SD or number (%). Student's t-test was used to analyze the parametric data, and discrete variables were analyzed using χ2 -test, with P-value less than 0.05 considered statistically significant.
| Results|| |
A total of 60 adult female patients were included in this study, and no patients were excluded throughout the course of the study. There was no statistically significant difference between the two groups in the patients' demographic data in terms of age, weight, and ASA classification ([Table 1]).
In the DEX group, there was a statistically significant decrease in HR at 45 min (75.9 ± 8.65 bpm), 60 min (71.33 ± 7.72 bpm), and 90 min (71.07 ± 6.74 bpm) after surgical incision in comparison with preoperative HR (84.93 ± 9.53 bpm) ([Table 2]).
|Table 2 Heart rate changes in both dexmedetomidine and transversus abdominis plane groups|
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In the TAP group, there was a statistically significant decrease in HR at 60 min (77.53 ± 4.36 bpm) and 90 min (77.5 ± 4.94 bpm) after surgical incision in comparison with preoperative HR (82.97 ± 8.14 bpm) ([Table 2]).
In the DEX group, there was a statistically significant decrease in MAP at 30 min (81.77 ± 6.98 mmHg), 45 min (77.23 ± 7.56 mmHg), 60 min (78.7 ± 6.69 mmHg), and 90 min (80.63 ± 6.14 mmHg) after surgical incision in comparison with preoperative mean arterial blood pressure (89.07 ± 7.95 mmHg) ([Table 3]).
|Table 3: Changes of mean arterial pressure in both dexmedetomidine and transversus abdominis plane groups|
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In the TAP group, there was no statistically significant change in the MAP at any period of intraoperative duration in comparison with preoperative MAP ([Table 3]).
No statistically significant difference was observed with regard to BIS in both the groups throughout the intraoperative duration ([Table 4]).
|Table 4: Changes of bispectral index in both dexmedetomidine and transversus abdominis plane groups|
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In the DEX group, there was a statistically significant increase in blood level of cortisol 12 h postoperatively (21.87 ± 7.48 μg/dl) and 24 h postoperatively (22.37 ± 8.01 μg/dl) in comparison with preoperative blood level (14.17 ± 6.41 μg/dl) ([Table 5]; [Figure 1]).
|Figure 1: Changes in serum cortisol (¦Ìg/dl) in both the DEX and TAP groups. DEX, dexmedetomidine; TAP, transversus abdomin is plane.|
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|Table 5 Changes in serum cortisol (¦Ìg/dl) in the dexmedetomidine and transversus abdominis plane groups|
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In the TAP group, there was no statistically significant change in the blood cortisol level at any time of measurement (intraoperatively or postoperatively) in comparison with preoperative cortisol blood level ([Table 5]; [Figure 1]).
The blood level of cortisol was significantly higher in the DEX group 12 and 24 h postoperatively when compared with that in the TAP group ([Table 5]; [Figure 1]).
In the DEX group, there was a statistically significant increase with regard to the blood level of norepinephrine, 12 h (530.67 ± 141.85 pg/ml) and 24 h (659.67 ± 190.79 pg/ml) postoperatively, in comparison with preoperative blood level of norepinephrine (243.63 ± 122.26 pg/ml) ([Table 6]; [Figure 2]).
|Figure 2: Changes in serum norepinephrine (pg/ml) in both the DEX and TAP groups. DEX, dexmedetomidine; TAP, transversus abdomin is plane.|
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|Table 6 Changes in serum norepinephrine in both dexmedetomidine and transversus abdominis plane groups|
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In the TAP group, there was no statistically significant change in the blood level of norepinephrine at any time of measurement intraoperatively or postoperatively in comparison with preoperative norepinephrine blood level ([Table 6]; [Figure 2]).
There was no statistically significant difference with regard to intraoperative fentanyl increments in both the groups ([Table 7]).
|Table 7: Intraoperative incremental fentanyl in both dexmedetomidine and transversus abdominis plane groups|
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There was a highly significant difference with regard to postoperative pethidine supplementation in both the groups ([Table 8]).
|Table 8: Postoperative pethidine in both dexmedetomidine and transversus abdominis plane groups|
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In the DEX group, there was a statistically significant increase in VNRS at rest at: 6, 12, and 24 h postoperatively in comparison with value of VNRS at rest immediately in PACU ([Table 9]; [Figure 3]).
|Figure 3: VNRS at rest in the TAP group. Data are presented as median and interquartile range. TAP, transversus abdominis plane; VNRS, verbal numerical rati ng scale.|
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|Table 9: Verbal numerical rating scale at rest in both dexmedetomidine and transversus abdominis plane groups|
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In the TAP group, there was no statistically significant change in VNRS at rest at any time of postoperative period in comparison with the value of VNRS at rest immediately in PACU ([Table 9]; [Figure 4]).
|Figure 4: VNRS at rest in the DEX group. Data are presented as median and interquartile range. DEX, dexmedetomidine; VNRS, verbal numerical rating scale.|
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In the DEX group, there was a statistically significant increase in value of VNRS on coughing at: 3, 6, 12, and 24 h postoperatively in comparison with the value of VNRS at coughing immediately in PACU ([Table 10]; [Figure 5]).
|Figure 5: VNRS at coughing in the DEX group. Data are presented as median and interquartile range. DEX, dexmedetomidine; VNRS, verbal numerical rating scale.|
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In the TAP group, there was no statistically significant change of the value of VNRS at coughing at any time of postoperative in comparison with the value of VNRS immediately in PACU ([Table 10]; [Figure 6]).
|Figure 6: VNRS at coughing in the TAP group. Data are presented as median and interquartile range. TAP, transversus abdominis plane; VNRS, verbal numerical rati ng scale.|
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|Table 10: Verbal numerical rating scale at coughing in both dexmedetomidine and transversus abdominis plane groups|
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There was statistically significant increase in time required for first request of analgesia (pethidine) postoperative in the TAP group in comparison with the DEX group ([Table 11]; [Figure 7]).
|Figure 7: Time to fi rst postoperative request of analgesia (pethidine) (h) in both the groups. DEX, dexmedetomidine; TAP, transversus abdomin is plane.|
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|Table 11 Time to fi rst postoperative request of analgesia (pethidine) in both the groups|
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| Discussion|| |
Postoperative analgesia reduces postoperative stress response and postoperative morbidity, and in certain types of surgery it improves surgical outcome, fastens recovery after surgery, and makes rehabilitation much easier  .
US-guided TAP block is an effective anesthetic technique for abdominal surgeries, providing anesthesia to the entire anterior abdominal wall , . Direct imaging using US increases safety and quality of the block. This coincides with Liu et al.  and Koscielniak-Nielsen  who concluded that US guidance reduces the block time and the number of attempts, and decreases the block onset time. In addition to Farooq and Carey  who found another advantage of using a US-guided technique, is that accidental puncture of the internal gastrointestinal organs reported with the TAP block can be avoided.
Dexmedetomidine is a potent α2 agonist. Its primary analgesic effect is mediated through the activation of the α2 receptors on the dorsal horn of the spinal cord and also by the inhibition of substance P  . It has analgesic-sparing effect proved by Ebert et al.  who showed dose-dependent decrease in pain rating with increasing doses of dexmedetomidine in volunteers.
In the present study, with regard to the intraoperative hemodynamic changes, we have found that patients in both the DEX and TAP groups had a statistically significant intraoperative decrease in the HR, with it being more decreased in the DEX group (45, 60, and 90 min after surgical incision) than in the TAP group (60 and 90 min after surgical incision). In the DEX group, bradycardia is caused by baroreceptor reflex and enhanced vagal activity resulting from central stimulation of parasympathetic outflow, as well as a reduced sympathetic drive  . Changes in the TAP group coincided with the study by Tsuchiya et al.  who concluded that combining TAP block with general anesthesia in high-risk ASA III patients with cardiovascular disease promotes intraoperative hemodynamic stability with mild decrease in HR and MAP, as well as early emergence from anesthesia.
There is better intraoperative control of the MAP in the DEX group than in the TAP group, as the DEX group showed statistically significant decrease in the intraoperative MAP, whereas in the TAP group there was no significant change in MAP compared with preoperative values. This hypotensive effect of dexmedetomidine results from the stimulation of subtypes α2 a and α2 c inhibitory neurons found predominantly in the CNS in the medullary vasomotor center (nucleus reticularis lateralis) of the brainstem, which leads to a reduction in norepinephrine release and sympathetic nerve outflow from the CNS to the peripheral tissues  . This coincides with the conclusion stated by Karakaya et al.  that the use of dexmedetomidine in coronary artery bypass graft surgery causes a moderate decrease in HR and MAP without reaching clinically important levels. It is also agreed with by Penttilδ et al.  who noted that the cardiovascular effects of dexmedetomidine are predictable and caused by α2 -adrenoceptor pharmacological effects.
There is no evident advantage or effect on the depth of anesthesia neither in the DEX group nor in the TAP group, as BIS readings showed almost the same range of readings in both the groups all through the time of surgery.
Activation of the hypothalamic-pituitary-adrenal axis and cortisol secretion associated with surgical trauma are very important perioperative stress responses  . The TAP block had intense effect on controlling surgical stress response. This is proved when there was no change in the plasma level of cortisol and norepinephrine during the time of surgery, in PACU immediately after surgery, 12 and 24 h postoperatively when compared with the preoperative value.
In the DEX group, intraoperative records for stress hormones did not show a significant change. Thomas et al.  showed that dexmedetomidine infusion decreased the plasma level of catecholamine in healthy volunteers. Venn et al.  proved that dexmedetomidine was not found to affect the process of steroidogenesis. However, Aho et al.  found that patients receiving dexmedetomidine had significantly lower intraoperative cortisol levels. This supports our findings intraoperatively. On the contrary, the DEX group in our study showed marked increase in the level of plasma cortisol and norepinephrine in the postoperative period.
The analgesic properties of dexmedetomidine in humans are more controversial. Stimulation of the α2 a subtype is responsible for sedation, analgesia, and sympatholysis, whereas stimulation of the α2 c subtype is responsible for anxiolysis and contributes to spinal antinociception  . Therefore, it appears to exert analgesic effects at the spinal cord level and at the supraspinal sites  . Although the TAP block has been described as an effective regional anesthetic method for various surgical procedures  .
In the present study, incremental intraoperative doses of fentanyl are almost the same. This was confirmed by Flacke et al.  who stated that dexmedetomidine infusion reduces opioid intraoperative  . In addition, Cho et al.  found that The TAP block caused a 25% reduction in intraoperative fentanyl. The advantage of using preoperative TAP block is explained by blocking the somatosensory pain of the incision site, reducing intraoperative opioid requirements and postoperative side effects, which were confirmed by Mukhtar and Singh  .
With regard to postoperative analgesic effect, there was a remarkable difference between the two groups. The TAP group had a significant better postoperative analgesic effect than the DEX group, as the DEX group experienced higher pain score at late postoperative period. This coincides with the study by Kida et al.  who concluded that intraoperative administration of dexmedetomidine improved early postoperative pain status. However, this was against the results of McCutcheon et al.  who they stated that intraoperative DEX infusion significantly reduced postoperative supplemental analgesics. They referred this to the continued effect of DEX on α2 -adrenoreceptor in the spinal cord  . This can also be supported in our study that patients in the DEX group required significantly higher total doses pethidine compared with those in the TAP group. In addition, patients who had been treated with DEX asked for the first dose rescue pethidine much earlier than those in the TAP group.
The VNRS scores at rest and at coughing in the TAP group were almost of the same values up to 24 h postoperatively, meaning that the analgesic effect of TAP block extends to cover the first 24 h. Same results were shown by Niraj et al.  who confirmed that pain scores, both at rest and during mobilization, were significantly reduced with the TAP block in the early postoperative period (0-6 h), and Carney et al.  who found that pain scores were also reduced for 24 h. The reasons for the prolonged duration of analgesic effect after TAP blockade may relate to the fact that the TAP is relatively poorly vascularized, and therefore drug clearance may be slowed.
Our data are in contrast with those of McMorrow et al.  who found no additional analgesic effect of the TAP block, when TAP block and spinal morphine were administered in combination, with the difference that the TAP block was performed by anatomical landmark technique.
The total dose of rescue pethidine is lower in the first 24 h postoperative, with delayed request for rescue analgesia in the TAP group. This goes hand in hand with McDonnell et al.  who proved that the first 48 h morphine requirements were decreased by 70%, and delayed supplemental opioids in patients who underwent TAP block compared with standard analgesia regimen alone.
| Conclusion|| |
In open ovarian cystectomy operations, in the setting of multimodal analgesia, US-guided TAP block was comparable to dexmedetomidine infusion with regard to intraoperative hemodynamic stability, opioid requirement without change in stress response hormones. However, in the postoperative period, US-guided TAP block provided superior analgesia when compared with dexmedetomidine infusion up to 24 h postoperative, demonstrating both a substantial reduction in pethidine consumption as well as improved pain scores and delayed request of rescue analgesia, with no change in stress response hormones.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11]