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Background: Evidence shows that spinal anesthesia can alter the penile length and penile engorgement and the fact that patients undergoing spinal anesthesia may experience erectile dysfunction. We hypothesized that spinal anesthesia would not result in altered penile length; however, it can lead to temporary erectile dysfunction. Methods: A total of 73 patients referred to our hospital for endoscopic urological surgeries underwent either spinal anesthesia (SA, n = 37) or general anesthesia (GA, n = 36). We measured patients’ penile length in both stretched and flaccid states during surgery and compared changes in penile length between the SA and GA groups. We assessed erectile function in patients through a standard questionnaire one month and three months after the surgery. Results: No significant difference was observed in penile length during and two weeks after surgery between the SA and GA groups (P > 0.05). Regarding erectile function, we observed a significant difference in the international index of erectile function (IIEF)-5 score between the two study groups one-month after surgery (P < 0.05). However, there was no significant difference between the SA and GA groups three months after the surgery. Spinal anesthesia had no significant effect on penile length during and two weeks after surgery compared to general anesthesia. Conclusions: Patients undergoing SA may experience transient erectile dysfunction one month after surgery; however, they may develop transient erectile dysfunction, which is recovered three months after surgery.

Introduction In this study, we aim to assess the intra-operative effect of dexmedetomidine administration on the hemodynamic parameters and bleeding volume during hip fracture surgery. Patients and methods we designed and implemented a triple-blinded randomized clinical trial to objectively compare the effects of 0.5 µg/kg/h infusion of dexmedetomidine with placebo (equal amount of normal saline) during hip fracture surgery. All included cases were between 30 and 70 years old and underwent surgery for fixation of a proximal femur fracture from September 26, 2020 until February 15, 2021. They were all ASA class I or II with preoperative hemoglobin levels of 10 mg/dL or higher. Surgical blood loss and hemodynamic parameters were documented. Results 76 patients were enrolled. There were no significant differences in baseline patient characteristics. The bleeding rate was 620 ± 190.0 mL for the normal saline group and 476 ± 177.98 mL in the dexmedetomidine group (P = 0.04). No significant effect on hemodynamic parameters was observed. Conclusion Based on the current study, intravenous infusion of dexmedetomidine during hip fracture surgery under general anesthesia reduced the amount of intraoperative bleeding without causing any significant hemodynamic disturbances. Registration number IRCT20191222045857N1 (Iranian Registry of Clinical Trials)

Introduction: The most common type of neck pain is chronic nonspecific pain. There are conflicting opinions about the beneficial effects of a low-level laser in reducing chronic nonspecific neck pain. The aim of this study was to evaluate the efficacy of low-level laser therapy (LLLT) for the treatment of non-specific chronic neck pain. Methods: This study was conducted as a prospective randomized clinical trial. Forty-four patients were randomly divided into two groups: (1) Intervention group (n=22): LLLT in the red spectra range with a wavelength of 980 (nm) and a power of 16 (J/cm2 ) was irradiated in the affected areas of the neck, the muscles along the spine, and the upper trapezius; (2) sham group (n=22): A low-level laser was irradiated with a passive probe (non-laser red light) in the affected areas of the neck, the muscles along the spine, and the upper trapezius. The treatment protocol consisted of 12 sessions (15 minutes, three times a week, for four weeks). These patients were evaluated for pain using the visual analog scale (VAS) (0-10). The patients were followed up for four weeks. Results: This study showed a statistically significant reduction in chronic nonspecific neck pain in the LLLT group (P

Background: The corona pandemic has created many unpredictable challenges for the medical staff and students. In almost all countries, changes have been made in the medical education programs at all levels. The anesthesiology assistants are among the most affected groups due to the role of this specialty in the management of COVID patients. Methods: We prepared a questionnaire including demographic information, as well as 20 questions associated with work and educational issues. The questionnaire was sent to all anesthesia assistants via SMS and the answers were collected within 5 days. The 20 main questions were designed in the form of multiple-choice questions with 5 standard options. Results: Responses were immediately reported after categorization. Chi-square test was used to compare the answers among the subgroups, such as male and female, single and married and at different levels. 66 anesthesia assistants out of total amount of 71 at four different levels (92.9%) answered the questions. The results showed that the majority of assistants have experienced a higher level of stress during corona pandemic and the negative effects of the pandemic on their medical education were obvious. Conclusion: According to the responses received in this study, the amount of stress in male assistants was less than females and also married assistants experienced less stress in comparison to singles.

Background: Spinal anesthesia is commonly used for orthopedic surgeries. The most important issue to improve outcome is patient cooperation to have a proper position for reducing pain during spinal anesthesia procedure. However, any change in position is painful which leads to sympathetic activation, tachycardia and hypertension, which may put patients with ischemic heart disease at risk. Peripheral nerve block is a safe and reliable alternative to systemic analgesia. Using the ultrasound-guided method reduces local anesthetics’ amount and side effects. Methods: In this study, 53 patients who came to the operating room with femoral fracture as candidates for spinal anesthesia were enrolled and received ultrasound-guided Femoral Nerve Block (FNB) (10 ml Lidocaine 1.5%). Before and after receiving the nerve block, the patients were asked about the severity of their pain using the Numerical Rating Scale (NRS). Both groups of patients and physicians were asked about their satisfaction according to a 5-point Likert scale. Results: Mean pain intensity in the NRS score at the time of admission to the operating room was 7.6±0.8, which was reduced to 1.8±1.5 after blockade. In this study, 39 (73.5%) patients were very satisfied (Likert scale 5), 10 (18.8%) were satisfied (Likert scale 4), 2 (3.7%) had no opinion (Likert scale 3), 2 (3.7%) were not satisfied (Likert scale 2), and no one was very dissatisfied (Likert scale 1). There was significant difference in physician’s satisfaction. Conclusion: Ultrasound-guided nerve block is a safe and effective method to be used for positioning during spinal anesthesia procedure.

Achondroplasia is the result of a mutation in the gene encoding the type 3 receptor for a fibroblast growth factor. This abnormality results in malformation endochondral ossification. Achondroplasia is characterized by disproportionately short stature, lumbar lordosis, large head, midface hypoplasia, short hands, and normal cognitive development. Our report is about a 28-year-old patient with achondroplasia who underwent surgery for correction of kyphosis due to spinal canal stenosis. In this present case we study management anesthesia.

Cystic fibrosis (CF) is a genetic disease resulting from a chlorine channel defect with autosomal recessive show, a physical and functional disorder in the transport of chlorine (Cl) through the plasma membrane in epithelial cells in organs such as the lungs, pancreas, liver, intestines, sweat glands, and epididymis. These cases are important for their perioperative respiratory complications. We present an anesthesia method conducted on a 24-year-old men CF case receiving general anesthesia for Arnold Chiari malformation surgery.

Background: One of the most common devastating problems that occur after urethroplasty is erection, which causes surgical complications (fistula, wound dehiscence, and surgical graft failure) and the need for repairing the complications. We attempted to compare the effect of continuous epidural infusion of dexmedetomidine and ropivacaine as a post-surgical erection prevention strategy. Objectives: In this study, we aimed to compare the effect of dexmedetomidine and ropivacaine epidural infusion on the incidence of erection after reconstructive urethral surgery. Methods: An RCT was conducted on 45 patients who were scheduled for reconstructive urethral surgery. They were randomly divided into three groups: (1) control (n = 15), (2) epidural dexmedetomidine (n = 15), (3) and epidural ropivacaine (n = 15). The control group received oral medication after surgery according to the conventional method (cyproterone compound tablets 50 mg BD and diazepam tablets 2 mg TDS for a week) to prevent erection. The DEX group received dexmedetomidine as continuous epidural infusion, and the ROP group received ropivacaine in addition to the conventional method. The occurrence of erection during day and night was recorded separately until the seventh day after surgery. Due to the long-time interval between case selection, participants from different groups were not matched with each other. Results: The incidence of erection in the dexmedetomidine group was lower than that in the ropivacaine group per person (0.87) and significantly lower than in the control group (2.8 per person). Also, there was significantly less erection in the ropivacaine group (1.2 per person) than in the control group. Our study showed that erection after surgery significantly decreased with the continuous epidural infusion of dexmedetomidine and ropivacaine. Conclusions: Dexmedetomidine seems to have a significant preventive effect on erection after reconstructive urethral surgery.

Introduction: Urinary stone disease is the third most common affliction of the urinary tract that has been associated with an increasing incidence. Over decades, great advances have been made in the minimally invasive treatment of urinary stones. Recently, transurethral lithotripsy (TUL) by holmium laser was introduced as a possible therapeutic option. This study evaluated the effect of propofol on the success rate of TUL by holmium laser. Methods: A double-blind randomized controlled trial was conducted on 180 patients to investigate the effect of propofol on the success and complication rate of TUL by holmium laser. The enrolled patients were divided into two groups: the first group received sodium thiopental (n=89) while the second group received propofol (n=91). The two groups were compared in terms of the fluctuations of systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), operation time, future stone-free rate (SFR), stone migration, post-operative fever, and ureteral complications such as perforation and mucosal damage. Other developed complications were also recorded. After data gathering, statistical analysis was performed with SPSS version 21. Results: the patients’ data such as age, sex, stone diameter, stone laterality, duration of stone impaction, primary SBP, DBP and HR were not significantly different between the two groups (P>0.05). TUL and anesthesia duration, first-minute and fifth-minute SBP and DBP, and also changes of HR were significantly lower in the propofol group compared with the sodium thiopental group (PConclusion: Propofol was associated with a higher reduction in SBP and DBP, decreased duration of TUL, fewer fluctuations in HR, and an increased success rate of stone removal by TUL with holmium laser.

Background: The use of regional methods in various types of surgery such as mastectomy is very popular today. Various methods, including Pecs I-II block, erector spinae, epidural thoracic, and paravertebral block have been used in these operations, each with its own advantages and disadvantages. Recent studies on the effect of μ receptor stimulation on the likelihood of recurrence and metastasis have been published, which make the use of a suitable regional approach with low complications and high efficacy attractive. Among the side effects of breast surgery in patients with cancer are nausea and vomiting, the risk of which is reduced through regional procedures that reduce the need for opioids. Methods: We randomly divided 64 patients into two pectoralis block (Pecs B) and erector spinae block (ESB) groups. Visual analogue scale (VAS) scores at 2, 4, 6, and 10 hours, nausea and vomiting, need for opioids, and hemodynamic changes were recorded. Results: The analyses showed that pain score was significantly higher in the Pecs B group compared to the ESB group, while VAS score, as well as the frequency of opioid use, were lower, which could be due to medial branch of the anterior intercostal nerve. Hemodynamic changes were also significantly greater in the ESB group, which could be due to the proximity of the block to the thoracic sympathetic nerves and spinal cord. Conclusions: Despite the statistically significant differences in analgesia and hemodynamic changes, the seemingly superiority of the Pecs B is not clinically significant and the use of both types of the block is selective. Regarding the need for opioids and nausea, Pecs B showed a tangible advantage over ESB.

Background Various mechanisms have been suggested for analgesic effects of drugs used in infra-clavicular block and each has contributed to pain relief. Objectives The aim of this study was to compare the degree of sympathetic block and measure tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-1 levels before and after infra-clavicular block with ropivacaine and bupivacaine in patients undergoing arterio venous fistula (AVF) surgery. Methods Forty-eight patients undergoing AVF surgery were randomly divided to two groups, undergoing infra-clavicular block with ropivacaine and bupivacaine. The bupivacaine group was blocked with 30 mL of 0.5% bupivacaine and in the ropivacaine group, the blockage was done with 30 mL of 0.5% ropivacaine. Infra-clavicular block was carried out by ultrasound in a vertical manner. Blood samples were taken before the block and one hour after the block to measure IL-1, IL-6, and TNF-alpha. Data were analyzed by covariance analysis and correlation t-test. Results T-correlation analysis showed that in both ropivacaine and bupivacaine groups, the TNF-alpha, IL-6, and IL-1 levels decreased after the block. Also, the increase in arterial diameter was significantly greater in ropivacaine group. Conclusions The present study showed that peripheral block with any single drug could reduce pre-inflammatory factors. On the other hand, ropivacaine significantly increased the diameter of the artery compared to the bupivacaine group.

Background: The best arteriovenous access in diabetic patients under dialysis is crucial to attain better therapeutic outcomes and improved prognosis in the patients. The purpose in this study was to compare the primary patency and maturation rate of antecubital artriovenous fistula for dialysis in diabetic patient with two methods: regional block with Ropivacaine 0.5% and local anesthesia with lidocaine 2%. Methods and Materials: In this randomized clinical trial, 40 consecutive diabetic patients under dialysis in 2016 and 2017 in a training center were enrolled and the primary patency and maturation rate of antecubital artriovenous fistula were compared with regional block with Ropivacaine 0.5% versus local anesthesia with lidocaine 2%. Results: The results in this study demonstrated that all factors of final arterial and venous diameter, blood flow, and patency were higher in group under regional block with Ropivacaine 0.5% and all except patency showed significant difference (P < 0.05). The complications rates were alike across the groups (P > 0.05). Conclusion: Totally, according to the obtained results, it may be concluded that regional block with Ropivacaine 0.5% is superior to local anesthesia with lidocaine 2% leading to higher patency rate and shorter maturation time and also higher arteriovenous diameter and blood flow.

Background: Post - operative nausea and vomiting (PONV) still continues to be a serious problem. Incidence of PONV is more than 20% to 30%. Intravenous fluid administration seems to decrease PONV. Objectives: The aim of this study was to evaluate the effect of pre - operative and intraoperative intravenous hydration in comparison to routine hydration on PONV in breast cancer surgery. Methods: This study was performed on 105 female patients with ASA class grade I and II; they were randomly divided to 3; group 1: routine hydration (1.5 cc/kg/h normal saline). Group 2: routine hydration + 5 cc/kg of ringer lactate serum 80 to 90 minutes before surgery, and group 3: routine hydration + 5 cc/kg post - operative pain, anti - emetic and analgesic administration were compared between 3 groups, using VAS and cortila questionnaire. Results: There were no significant difference between 3 groups considering demographic data (age, literacy, weight, height, etc.) duration of breast cancer, cancer stage, pre - operative fasting time, duration of surgery, etc. Blood loss was significantly lower in intraoperative fluid supplementation group (P < 0.05), but PONV and post - operative pain were significantly lower in those who received pre - operative fluid supplementation. They also needed less anti - emetic or analgesic administration. Conclusions: Pre - operative fluid supplementation showed to be an effective prophylactic strategy in PONV. Type of fluid and its volume need more evaluation in future studies.

Background In patients admitted to the Intensive Care Unit (ICU), Enteral Nutrition (EN) is the first choice for feeding support, however, it is often complicated by gastrointestinal side effects, such as diarrhea. There are no studies that have specifically evaluated effect of a prebiotic, which prevents diarrhea during enteral nutrition. Objective This study aimed at evaluating the effect of honey in enteral diet during occurrence of diarrhea and fecal microbiotain in critically ill patients. Materials and methods In this double-blind, randomized controlled single-center study, 32 patients were randomly selected to receive a high protein kitchen enteral diet and the study group had honey as 10% of its carbohydrate intake. Quantitative analyses of bifidobacterium and Lactobacillus species of fecal samples were assessed by Real-Time Polymerase Chain Reaction (PCR) on days 0 and 7. Results Patients in the honey group showed an insignificant increase in the frequency of bifidobacterium DNA by study day 7 in comparison with the control group. In the honey group, there was a considerable reduction in diarrhea (P = 0.09). A significant difference was found in length of Intensive Care Unit (ICU) stay (P = 0.001) and Sequential Organ Failure Assessment (SOFA) score (P = 0.04) in favor of the honey group. Conclusions Enteral nutrition with honey might reduce the length of stay at the ICU and development of organ failure in critically ill patients. It seems that honey helps reduce the incidence of diarrhea.

BackgroundThe use of ultrasonographic guide is a suggested way to ease the obturator nerve block procedure. Accordingly, in this study, the procedures by selective obturator nerve block with and without use of ultrasonographic guide were compared.MethodsThis interventional study was performed as an open-label randomized clinical trial among 50 consecutive subjects under surgery for intramural tumors of urinary bladder in a training hospital in 2016. The subjects were randomly assigned to be operated under spinal anesthesia accompanied with selective obturator nerve block (10 mL of 1.5% lidocaine adding 1:200000 epinephrine) with or without ultrasonographic guide. The outcomes were compared across the groups.ResultsThere was no statistically significant difference between the onset time in group without guide (6.3 ± 2.2 minutes) and that in the guided group (5.9 ± 2.1 minutes). The time required for the nerve block (4.4 ± 1.3 minutes versus 1.7 ± 0.8 minutes) was significantly shorter (P = 0.001). There were less complications in the group with use of ultrasonographic guide showing significant difference (P = 0.01). The success rate in block was significantly higher in the group with ultrasonographic guide (100% versus 92%, P > 0.05).ConclusionsFinally, according to the obtained results, it may be concluded that ultrasonography guidance would improve efficacy of obturator nerve block compared with conventional techniques.

Introduction: Pain is the most common complaint of patients referring to emergency department (ED). Consideringthe importance of pain management in ED, this study aimed to investigate the efficacy and feasibility ofultrasound-guided nerve blocks in this setting. Methods: 46 patients who came to the ED with injured extremitieswere enrolled in the study and received either femoral, axillary or sciatic nerve block depending on theirsite of injury (1.5 mg Bupivacaine per kg of patient’s weight). Patients were asked about their level of pain beforeand after receiving the nerve block based on numerical rating scale. The difference between pre and post blockpain severity was measured. Both patients and physicians were asked about their satisfaction with the nerveblock in 5 tiered Likert scale. Results: 46 patients with the mean age of 37.5 § 12.5 years (8-82 years) receivedultrasound-guided nerve block (84.8% male). 6 Sciatic, 25 axillary, and 15 femoral nerve blocks were performed.Mean pain severity on NRS score at the time of admission was 8.1 § 1.4, which reduced to 2.04 § 2.06 after block.25 (54.3%) patients were highly satisfied (Likert scale 5), 15 (32.6%) were satisfied (Likert scale 4), 3 (6.5%) wereneutral and had no opinion (Likert scale 3), 1 (2.1%) was not satisfied (Likert scale 2), and 2 (4.3%) were highlyunsatisfied (Likert scale 1). There was no significant difference among the satisfaction scores within the threeblock locations (p = 0.8). There was no significant difference in physicians level of satisfaction between the threeblock locations either (p = 0.9). 1 (2.1%) case of agitation and tachycardia and 1 (2.1%) case of vomiting wereobserved after the procedure. Conclusion: Ultrasound-guided nerve block of extremities is a safe and effectivemethod that can be used for pain management in the ED. It results in high levels of satisfaction among bothpatients and physicians.

Background: Postoperative pain is one of the most common problems after hernia repair. Decrease in postoperative pain accelerates functional recovery, decreases duration of hospital stay and postoperative morbidity. Objectives: To compare postoperative analgesic effect of infiltration of magnesium versus bupivacaine into incision of inguinal hernia repair. Patients and Methods: In a double blind clinical trial, 80 patients’ candidates for elective inguinal hernia repair were enrolled. Right before closure of incision, in Bupivacaine group 5 mL Bupivacaine 0.5% added to 5 mL normal saline and in Magnesium group, 10 mL Magnesium sulfate 20% was infused subcutaneously. Pain score was measured using numeric rating score (NRS) at 1, 3, 6, 12 and 24 hours postoperatively. If NRS was above 3, 1 mg morphine was administered as rescue analgesic until patient felt comfortable or NRS < 3. Results: Postoperative pain scores at 1 and 3 hours were not significantly different between bupivacaine and magnesium groups (P = 0.21, 0.224; respectively). However, at 6 (P = 0.003), 12 (P = 0.028) and 24 (P = 0.022) hours postoperative, pain score (NRS) was significantly lower in bupivacaine group. Number of patients needed at least 1 dose of rescue morphine (P = 0.001), mean number of episodes asked for morphine during next 24 hours (P = 0.001) and total dose of morphine requirement (P = 0.01) were significantly lower in bupivacaine group. Conclusions: Magnesium infiltration did not decrease total dose and number of episodes needed for morphine rescue analgesic. Bupivacaine infiltration into surgical site was more effective than magnesium sulfate infiltration in postoperative pain control.

Background: The current randomized double-blind clinical trial aimed to compare the incidence of post-operative cough with intravenous vs. topical lidocaine in children with mild upper respiratory infection (URI) anesthetized with laryngeal mask airway (LMA) in the university-affiliated medical center. Objectives: To assess the incidence of adverse respiratory event including cough, apnea, laryngospasm, bronchospasm following two different methods of lidocaine administration in anesthetized children with mild URI. Patients and methods: One hundred and thirty pediatric patients with mild URI (within the previous two weeks) aged between one and six years were enrolled. They were candidates to undergo immediate full ophthalmic examination, and randomly divided into two groups of 65to receive intravenous (1.5 mg/kg) or topical lidocaine on LMA. Anesthesia was induced with sevoflurane, subsequently LMA was inserted when the patient was in deep anesthesia status and maintained on (50% N2O, 50% O2) and 3% sevoflurane. Spontaneous ventilation was maintained throughout the procedure and LMA was removed in deep anesthesia. Outcomes (cough, laryngospasm, bronchospasm and vomiting) were evaluated peri-operatively and one day post-operation. Results: One hundred and twenty four patients fulfilled the trial. Cough (primary outcome) was significantly more frequent among those with topical compared with intravenous lidocaine (46% vs. 26%; P = 0.004). The incidence of laryngospasm (32% vs. 27%), bronchospasm (18% vs. 12%), desaturation (18% vs. 12%) and vomiting (5% vs. 2%) was not statistically different between the groups. Conclusions: The pediatric patients undergoing general anesthesia with LMA with intravenous lidocaine experienced fewer incidence of postoperative cough compared to the ones in the topical lidocaine group.

BACKGROUND: Opium is an addictive agent and one of the most common narcotics With great challenges of intraoperative hemodynamic instabilities. OBJECTIVES: The current study aimed to assess the effects of clonidine on intraoperative blood loss in patients with and without opium addiction in femoral fracture surgeries. PATIENTS AND METHODS: In a randomized clinical trial, 160 candidates for elective femoral fracture operations under general anesthesia were divided into four groups of 40 subjects: group 1 (placebo 1), subjects without addiction received placebo 90 minutes before the operation; group 2 (placebo 2), patients with opium addiction received placebo as group 1; group 3 (Clonidine 1), patients without addiction received clonidine 90 minutes before the operation and group 4 (Clonidine 2), patients with opium addiction received clonidine as premedication. RESULTS: Intraoperative blood loss in clonidine recipient groups, patients with and without addiction, was less than that of the placebos (both P values < 0.01) and the difference magnitude was higher in patients with opium addiction. CONCLUSIONS: Premedication with clonidine to decrease intraoperative blood loss can be more effective in patients with opium addiction than the ones without addiction.

Background Postoperative sore throat is one of the most common complications after endotracheal intubation. Both Ketamine and magnesium can block N-methyl-D-aspartic acid (NMDA) receptors and provide central and local analgesia. Objectives To compare the effect of magnesium sulfate and ketamine gargle on the incidence and severity of postoperative sore throat. Patients and methods A total of 100 patients candidate for emergency acute appendicitis surgery were enrolled in the study. Patients in ketamine group received ketamine gargle (0.5 mg/kg) and magnesium group received magnesium sulfate gargle (20 mg/kg up to 30 mL dextrose water 20%) 15 minutes before the operation. Patient complaint of postoperative sore throat, and its severity measured by visual analogue scale (VAS) were recorded at baseline in recovery room, and then 2, 4, and 24 hours after operation. Results There were no significant differences between age, sex, and body mass index (BMI) between two groups of patients. Hemodynamics of patients, including blood pressure, respiratory rate, oxygen saturation %, and conscious state were not significantly different (P > 0.05). Number of patients with sore throat were significantly lower in magnesium group compared to ketamine group at 2 (P = 0.032), 4 (P = 0.02), and 24 hours (P = 0.01) after the operation. Sore throat pain score (VAS) was significantly lower in magnesium group compared to ketamine group at 2 (P = 0.019), 4 (P = 0.028), and 24 hours (P = 0.014) after the operation. Conclusions Magnesium at low dose decreases sore throat and pain severity more effectively compared to ketamine gargle.

Introduction Postoperative shivering (POS) is an early complication after craniotomy. Preventive pharmacologic drugs are the mainstay of treatment. Meperidine is the drug of choice but with increased risk of apnea, nausea, and increased intracranial pressure. Some reports have suggested that ondansetron and meperidine have similar anti-shivering effects. Objectives To assess the preventive effect of ondansetron on POS after craniotomy. Methods In a randomized, double-blind, placebo-controlled trial, 80 patients with American Society of Anesthesiologists status I to II between 20 and 60 years of age scheduled for elective craniotomy were enrolled in the study. Patients received either intravenous ondansetron 4 mg (n = 40) or saline (n = 40) 10 minutes before the end of surgery. Results POS was observed in 3 patients (7.5%) in the ondansetron group, significantly lower than in the control group (6 patients [15%]; P =0.048). Ondansetron decreased the relative risk of occurrence of POS after craniotomy from 4.42 (95% confidence interval [CI], 2.3–8.5; P = 0.0021) in the control group to 1.05 (95% CI, 0.76–2.20; P = 0.074). In the ondansetron group, the mean (± standard deviation) core temperature in the preoperative phase (36.6°C ± 0.66°C) was significantly higher than in the postoperative phase (34.2°C ± 0.56°C) ( P = 0.001). In addition, the mean (± standard deviation) peripheral temperature in the preoperative phase (36.5°C ± 0.72°C) was significantly higher than in the postoperative phase (34.4°C ± 0.51°C) ( P = 0.001). Conclusions Ondansetron can effectively decrease POS after craniotomy. This effect is not mediated through maintenance of the core or peripheral temperature. Ondansetron probably acts by a central inhibitory mechanism on POS through 5-hydroxytryptaminergic pathways, not by changing thermoregulatory set points.