Laryngeal Mask as the Primary Airway Device During Laryngotracheal Surgery: Data From 108 Patients.

BACKGROUND: Airway management during repair of laryngotracheal stenosis is demanding, and there is currently no accepted standard of care. Recently an increasing number of airway centers have started to use a laryngeal mask until the airway is surgically exposed and cross-table ventilation can be initiated. However detailed data on this approach are missing in the literature. METHODS: Patients receiving laryngotracheal surgery from November 2011 until October 2018 were retrospectively included in this single-center study, except for patients who presented with a preexisting tracheostomy at time of surgery. Airway management uniformly consisted of laryngeal mask ventilation until cross-table ventilation was established. Clinical variables, perioperative complications, and airway complications were analyzed. RESULTS: One hundred eight patients (65 women, 43 men) receiving tracheal resection (n = 50), cricotracheal resection (n = 49), or single-stage laryngotracheal reconstruction (n = 9) were included in the analysis. Of the included patients 23 (21.3%) had malignant disease and 85 (78.7%) a benign pathology. In the subgroup of patients with subglottic disease 85.1% had high-grade stenosis (Myer-Cotton III°). Airway management with a laryngeal mask was successful in all except 1 patient (99.1%). Mean pulse oximetry and mean end-tidal CO2 during laryngeal mask ventilation was 98.7% ± 2.4% and 34.8 ± 7.6 mm Hg, respectively. At the end of surgery 95 patients (88%) were successfully weaned from the respirator using the laryngeal mask. CONCLUSIONS: The laryngeal mask as the primary airway device is feasible and safe in patients undergoing laryngotracheal surgery even in cases with high-grade stenosis.

Intraoperative extracorporeal membrane oxygenation and the possibility of postoperative prolongation improve survival in bilateral lung transplantation.

OBJECTIVES: The value of intraoperative extracorporeal membrane oxygenation (ECMO) in lung transplantation remains controversial. In our department, ECMO has been used routinely for intraoperatively unstable patients for more than 15 years. Recently, we have extended its indication to a preemptive application in almost all cases. In addition, we prolong ECMO into the early postoperative period whenever graft function does not meet certain quality criteria or in patients with primary pulmonary hypertension. The objective of this study was to review the results of this strategy. METHODS: All standard bilateral lung transplantations performed between January 2010 and June 2016 were included in this single-center, retrospective analysis. Patients were divided into 3 groups: group I-no ECMO (n = 116), group II-intraoperative ECMO (n = 343), and group III-intraoperative and prolonged postoperative ECMO (n = 123). The impact of different ECMO strategies on primary graft function, short-term outcomes, and patient survival were analyzed. RESULTS: The use of intraoperative ECMO was associated with improved 1-, 3-, and 5-year survival compared with non-ECMO patients (91% vs 82%, 85% vs 76%, and 80% vs 74%; log-rank P = .041). This effect was still evident after propensity score matching of both cohorts. Despite the high number of complex patients in group III, outcome was excellent with higher survival rates than in the non-ECMO group at all time points. CONCLUSIONS: Intraoperative ECMO results in superior survival when compared with transplantation without any extracorporeal support. The concept of prophylactic postoperative ECMO prolongation is associated with excellent outcomes in recipients with pulmonary hypertension and in patients with questionable graft function at the end of implantation.

Lung transplantation for idiopathic pulmonary arterial hypertension on intraoperative and postoperatively prolonged extracorporeal membrane oxygenation provides optimally controlled reperfusion and excellent outcome.

OBJECTIVES: Lung transplantation for idiopathic pulmonary arterial hypertension has the highest reported postoperative mortality of all indications. Reasons lie in the complexity of treatment of these patients and the frequent occurrence of postoperative left ventricular failure. Transplantation on intraoperative extracorporeal membrane oxygenation support instead of cardiopulmonary bypass and even more the prolongation of extracorporeal membrane oxygenation into the postoperative period helps to overcome these problems. We reviewed our experience with this concept. METHODS: All patients undergoing bilateral lung transplantation for idiopathic pulmonary arterial hypertension on intraoperative extracorporeal membrane oxygenation with or without prophylactic extracorporeal membrane oxygenation prolongation into the postoperative period between January 2000 and December 2014 were retrospectively analysed. RESULTS: Forty-one patients entered the study. Venoarterial extracorporeal membrane oxygenation support was prolonged into the postoperative period for a median of 2.5 days (range 1-40). Ninety-day, 1-, 3- and 5-year survival rates for the patient collective were 92.7%, 90.2%, 87.4% and 87.4%, respectively. When compared with 31 patients with idiopathic pulmonary arterial hypertension transplanted in the same period of time without prolongation of extracorporeal membrane oxygenation into the postoperative period, the results compared favourably (83.9%, 77.4%, 77.4%, and 77.4%; P = 0.189). Furthermore, these results are among the best results ever reported for this particularly difficult patient population. CONCLUSIONS: Bilateral lung transplantation for idiopathic pulmonary arterial hypertension with intraoperative venoarterial extracorporeal membrane oxygenation support seems to provide superior outcome compared with the results reported about the use of cardiopulmonary bypass. Prophylactic prolongation of venoarterial extracorporeal membrane oxygenation into the early postoperative period provides stable postoperative conditions and seems to further improve the results.

Standard donor lung procurement with normothermic ex vivo lung perfusion: A prospective randomized clinical trial.

BACKGROUND: Ex vivo lung perfusion (EVLP) was primarily developed for evaluation of impaired donor lungs. The good clinical results raise the question for its possible impact on lungs meeting standard criteria. Before application of EVLP on such lungs enters routine clinical practice, it must be demonstrated whether EVLP would affect or improve outcome when used in standard donor lungs. We performed a prospective randomized trial to investigate the role of EVLP in standard lung transplantation (Tx). METHODS: This prospective randomized clinical trial compared patients who underwent Tx with ex vivo evaluated donor lungs with an equivalent patient population without previous EVLP. RESULTS: From October 2013 to May 2015, 193 lung Tx were performed at the Medical University of Vienna. During this period, 80 recipient/donor pairs that met the inclusion criteria were included in this trial, 41 pairs in the control group, and 39 in the EVLP group. In the EVLP group, 4 lungs (10.2%) ultimately did not qualify for Tx and were rejected for lung Tx owing to technical reasons (n = 2) and quality criteria (n = 2). Donor and recipient characteristics were comparable in both groups. Total cold ischemic time in the EVLP group was significantly longer for both implanted lungs (first side, 372 minutes vs 291 minutes, p < 0.001; second side, 437 minutes vs 370 minutes, p = 0.001); median duration of surgery showed no differences (277 minutes vs 275 minutes). Median oxygen partial pressure/fraction of inspired oxygen ratio at 24 hours after Tx was 516 (range, 280-557) in the EVLP group and 491 (range, 352-575) in the control group (p = 0.63). Incidence of primary graft dysfunction >1 was lower in the EVLP group at all time points compared with the control group (24 hours, 5.7% vs 19.5%, p = 0.10), and need for post-operative prolonged extracorporeal membrane oxygenation was lower in the EVLP group (5.7% vs 12.2%, p = 0.44). Short-term clinical outcomes did not differ between recipients in the 2 groups. Patients remained intubated (1.6 days vs 1.6 days, p = 0.67), in the intensive care unit (6 days vs 6 days, p = 0.76), and in the hospital (23 days vs 19 days, p = 0.42) for a comparable period of time. The 30-day survival was 97.1% vs 100% (p = 0.46). CONCLUSIONS: This study provides evidence that EVLP can safely be used in standard donor lungs. Functional results and perioperative outcome are comparable to those achieved with standard donor lung preservation techniques. As an evaluation tool, EVLP allows clinicians to identify and to possibly exclude lungs with functional impairment. Finally, EVLP can safely extend total preservation time.

Haemodynamic response at double lumen bronchial tube placement - Airtraq vs. MacIntosh laryngoscope, a randomised controlled trial.

INTRODUCTION: Tracheal intubation causes a haemodynamic response that might be harmful for patients. The Airtraq® laryngoscope has been shown to decrease the haemodynamic response to single-lumen tube intubation. We hypothesised that double-lumen bronchial tube placement with the Double-lumen Airtraq® laryngoscope would cause a reduced haemodynamic response and decreased catecholamine release compared with the MacIntosh laryngoscope. METHODS: Forty adult patients were randomly assigned to the Airtraq® group or to the MacIntosh group. Intubation with either the Airtraq® or the MacIntosh laryngoscope was performed two minutes after standardised induction of anaesthesia. Arterial blood pressure, heart rate, catecholamine levels, bispectral index and duration of the intubation procedure were measured. RESULTS: Mean (standard deviation [95% confidence interval]) systolic arterial blood pressure at laryngoscopy with the Airtraq® laryngoscope was 124 (34 [106 to 141]) mmHg and, with the MacIntosh laryngoscope, it was 110 (25 [99 to 122]) mmHg (p=1.0). Heart rate at laryngoscopy with the Airtraq® laryngoscope was 75 beats·min-1 (16 [67 to 83]) and, with the MacIntosh laryngoscope, it was 64 beats·min-1 (14 [58 to 71]) (p=0.71). Adrenaline levels post-intubation were 54.3 ng·l-1 (41.5) [29.3 to 79.4] in the Airtraq® group and 30.5 ng·l-1 (25.6) [15.1 to 46.0] in the MacIntosh group (p=0.016). The duration of intubation with the Airtraq® laryngoscope was 88 s (31 [72-104]) while, with the MacIntosh laryngoscope, the duration was 75 s (35 [59-92]) (p=0.26). CONCLUSIONS: The use of the Double-lumen Airtraq® laryngoscope provides no benefit regarding stress response compared to the MacIntosh laryngoscope.

Performance of supraglottic airway devices and 12 month skill retention: a randomized controlled study with manikins.

PURPOSE: Airway management for successful ventilation by laypersons and inexperienced healthcare providers is difficult to achieve. Bag-valve mask (BVM) ventilation requires extensive training and is performed poorly. Supraglottic airway devices (SADs) have been successfully introduced to clinical resuscitation practice as an alternative. We evaluated recently introduced (i-gel™ and LMA-Supreme™) and established SADs (LMA-Unique™, LMA-ProSeal™) and BVM used by laypeople in training sessions on manikins. METHODS: In this randomized controlled study, 267 third-year medical students participated with informed consent and IRB approval. After brief standardized training, each participant applied all devices in a randomized order. Success of device application and ventilation was recorded. Without further training, skill retention was assessed in the same manner 12 months later. Outcome parameters were the number of application attempts, application time, tidal volume and gastric inflation rate recorded at successful attempts, and subjective ease-of-use rating by the participants. RESULTS: i-gel™ and LMA-Supreme™ were the most successful in the first attempt at both assessments and in the subjective ease-of-use rating. The shortest application time was found with BVM (8 ± 5s in 2008 vs. 9 ± 5s in 2009) and i-gel (10 ± 3s vs. 12 ± 5s). Tidal volumes were disappointing with no device reaching 50% volume within the recommended range (0.4-0.6L). Gastric inflation rate was highest with BVM (18% vs. 20%) but significantly lower with all SADs (0.4-6%; p < 0.001 for 2008 and 2009). CONCLUSION: SADs showed clear advantages over BVM. Compared with LMA-Unique™ and LMA-ProSeal™, i-gel™ and LMA-Supreme™ led to higher first-attempt success rates and a shorter application time.

Effects of high-urgency ambulance transportation on pro-B-type natriuretic peptide levels in patients with heart failure.

OBJECTIVES: We hypothesized that pro-B-type natriuretic peptide (proBNP) levels in venous blood increase in patients with acute out-of-hospital heart failure because of stress during emergency ambulance transportation, and furthermore, we wanted to show if there is an effect of increasing proBNP levels on hemodynamic parameters. METHODS: Venous proBNP levels, visual analog scale (VAS) for pain and anxiety before and after transportation, heart rate, blood pressure, and transcutaneous Spo(2) were measured every 3 minutes in 32 patients with defined clinical signs of heart failure. RESULTS: ProBNP levels increased significantly (P < .01) during transportation (278.13 +/- 113.20 vs 984.67 +/- 627.33 pg/mL), whereas heart rate and mean blood pressure remained almost stable. There was no significant change in VAS for pain and anxiety (3.79 +/- 3.70 and 2.89 +/- 3.01 vs 2.13 +/- 3.30 and 1.57 +/- 2.78). CONCLUSION: A rapid increase in proBNP levels was shown in patients with acute out-of-hospital heart failure during emergency ambulance transportation but no significant changes in hemodynamic parameters.

Hemodynamic parameters change earlier than tissue oxygen tension in hemorrhage.

BACKGROUND: Untreated hypovolemia results in impaired outcome. This study tests our hypothesis whether general hemodynamic parameters detect acute blood loss earlier than monitoring parameters of regional tissue beds. MATERIALS AND METHODS: Eight pigs (23-25 kg) were anesthetized and mechanically ventilated. A pulmonary artery catheter and an arterial catheter were inserted. Tissue oxygen tension was measured with Clark-type electrodes in the jejunal and colonic wall, in the liver, and subcutaneously. Jejunal microcirculation was assessed by laser Doppler flowmetry (LDF). Intravascular volume was optimized using difference in pulse pressure (dPP) to keep dPP below 13%. Sixty minutes after preparation, baseline measurements were taken. At first, 5% of total blood volume was withdrawn, followed by another 5% increment, and then in 10% increments until death. RESULTS: After withdrawal of 5% of estimated blood volume, dPP increased from 6.1% +/- 3.0% to 20.8% +/- 2.7% (P < 0.01). Mean arterial pressure (MAP), mean pulmonary artery pressure (PAP) and pulmonary artery occlusion pressure (PAOP) decreased with a blood loss of 10% (P < 0.01). Cardiac output (CO) changed after a blood loss of 20% (P < 0.05). Tissue oxygen tension in central organs, and blood flow in the jejunal muscularis decreased (P < 0.05) after a blood loss of 20%. Tissue oxygen tension in the skin, and jejunal mucosa blood flow decreased (P < 0.05) after a blood loss of 40% and 50%, respectively. CONCLUSIONS: In this hemorrhagic pig model systemic hemodynamic parameters were more sensitive to detect acute hypovolemia than tissue oxygen tension measurements or jejunal LDF measurements. Acute blood loss was detected first by dPP.

Extended videoscopic robotic thymectomy with the da Vinci telemanipulator for the treatment of myasthenia gravis: the Vienna experience.

Surgical treatment of myasthenia gravis should include the complete resection of the thymus with the whole fatty tissue adherent to the pericardium for immunologic as well as oncologic reasons. The aim of the current study was to investigate the efficacy and safety of robotic approach. A total of 18 patients with myasthenia gravis (mean age 44 years) have been operated robotically via a left-sided approach. Preoperative MGFA (Myasthenia Gravis Foundation of America) classification was: Class I n=4, Class IIa n=4, Class IIb n=5, and Class IIIa n=3, IIIb n=2. Total endoscopic resection was feasible in 17/18 patients. One patient had to be converted due to bleeding. In the remaining patients, operative time was 175 min, intensive care unit (ICU) one day, hospital stay four days. In all patients it was possible to perform an extended thymic resection. MGFA post-intervention status after a mean of 18 months follow-up showed complete stable remission n=5, pharmacologic remission n=4, minimal manifestations n=5, unchanged n=1. Complete endoscopic thymus surgery with the da Vinci surgical system enables a complete and extended resection of all thymic tissue in the mediastinum. Due to the minimal trauma, patients can return to full activity within a short time.

A comparison of noninvasive blood pressure measurement on the wrist with invasive arterial blood pressure monitoring in patients undergoing bariatric surgery.

BACKGROUND: In morbidly obese patients, oscillometric blood pressure measurements with an upper-arm cuff are often difficult to perform. The alternative method, invasive blood pressure monitoring, can be difficult to place and is associated with risks. A wrist-mounted blood pressure-monitoring device, the Vasotrac, provides accurate blood pressure measurements in lean patients. Even in the obese, wrist morphology remains relatively unchanged. We thus assessed the degree to which blood pressure measurements with the Vasotrac on the wrist and cuff measurements agree with invasive arterial blood pressure monitoring. METHODS: We evaluated 22 morbidly obese patients undergoing bariatric surgery lasting 3.8+/-1.1 h. Intraoperative blood pressure was simultaneously measured using the Vasotrac mounted on one wrist; an arterial catheter was inserted in the opposite radial artery, and an oscillometric cuff was positioned on the upper arm. Preoperative patient comfort was evaluated on a scale from 1 to 10, with 10 being most uncomfortable, just after the first oscillometric cuff inflation. Values from the Vasotrac and arterial catheter were recorded at 5-s intervals. Bias, precision, and clinically acceptable agreement were calculated between the two continuous monitoring devices and between the arterial catheter and the cuff measurements, with the arterial catheter providing the reference value. RESULTS: The patients' age was 44.3+/-9.5 years (mean+/-SD), body mass index was 66.7+/-13.8 kg/m2, and arm circumference was 48.6+/-7.5 cm. Patients found the Vasotrac more comfortable than the oscillometric device [1.7+/-1.8 vs 5.3+/-0.5 (P=0.009)]. A total of 40,411 pairs of values from the Vasotrac and arterial catheter were recorded. Lin's concordance correlation coefficient (95% CI) for mean arterial blood pressure measured between the arterial line and the Vasotrac was 0.74 (0.67, 0.82). The bias (mean error) was -0.25 mmHg; however, the Bland-Altman limits where 95% of individual pressure differences are expected to fall was (-20, 20) mmHg. The precisions for diastolic and systolic pressures were even worse. CONCLUSION: The Vasotrac was more comfortable than an oscillometric device. Although the average accuracy was good, individual mean Vasotrac and noninvasive blood pressure pressures often differed considerably from arterial values. These results suggest that the Vasotrac monitor should not be substituted for an arterial catheter in super-obese patients.

Prehospital analgesia with acupressure at the Baihui and Hegu points in patients with radial fractures: a prospective, randomized, double-blind trial.

BACKGROUND: Pain during transportation is a common phenomenon in emergency medicine. As acupressure has been deemed effective for pain management by the National Institutes of Health, we conducted a study to evaluate its effectiveness in prehospital patients with isolated distal radial fracture. METHODS: This was a prospective, randomized, double-blind study. Thirty-two patients were enrolled. Acupressure was performed either at "true" points or at "sham" points. Vital signs and pain and anxiety scores were recorded before and after the acupressure treatment. Normally distributed values were compared using the Student t test. RESULTS: Pretreatment scores for pain and anxiety were similar in the 2 groups (47.6 +/- 8.9 vs 51.2 +/- 8.7 visual analog scale [VAS] score for pain, 52.4 +/- 6.0 vs 47.5 +/- 9.3 VAS score for anxiety). At the hospital, patients in the true-points group had significantly lower pain (36.6 +/- 11.0 vs 56.0 +/- 13.3 VAS score, P < .001) and anxiety scores (34.9 +/- 22.2 vs 53.4 +/- 19.7 VAS score, P = .022). CONCLUSION: Acupressure in the prehospital setting effectively reduces pain and anxiety in patients with distal radial trauma.

The influence of stellate ganglion transcutaneous electrical nerve stimulation on signal quality of pulse oximetry in prehospital trauma care.

BACKGROUND: Accurate monitoring of the peripheral arterial oxygen saturation has become an important tool in the prehospital emergency medicine. This monitoring requires an adequate plethysmographic pulsation. Signal quality is diminished by cold ambient temperature due to vasoconstriction. Blockade of the stellate ganglion can improve peripheral vascular perfusion and can be achieved by direct injection or transcutaneous electrical nerve stimulation (TENS) stimulation. We evaluated whether TENS on the stellate ganglion would reduce vasoconstriction and thereby improve signal detection quality of peripheral pulse oximetry. METHODS: In our study, 53 patients with minor trauma who required transport to the hospital were enrolled. We recorded vital signs, including core and skin temperature before and after transport to the hospital. Pulse oximetry sensors were attached to the patient's second finger on both hands. TENS of the stellate ganglion was started on one side after the beginning of the transport. Pulse oximeter alerts, due to poor signal detection, were recorded for each side separately. RESULTS: On the hand treated with TENS we detected a significant reduction of alerts compared to the other side (mean alerts TENS 3.1 [1-15] versus control side 8.8 [1-28] P < 0.05). The duration of dropouts was shorter as well (mean duration TENS 77 [16-239] s versus control side 333 [78-1002] s). CONCLUSION: The data indicate that blockade of the stellate ganglion with TENS improves signal quality of pulse oximeters in the prehospital setting.

Assessing intravascular volume by difference in pulse pressure in pigs submitted to graded hemorrhage.

We assessed changes in intravascular volume monitored by difference in pulse pressure (dPP%) after stepwise hemorrhage in an experimental pig model. Six pigs (23-25 kg) were anesthetized (isoflurane 1.5 vol%) and mechanically ventilated to keep end-tidal CO2 (etCO2) at 35 mmHg. A PA-catheter and an arterial catheter were placed via femoral access. During and after surgery, animals received lactated Ringer's solution as long as they were considered volume responders (dPP>13%). Then animals were allowed to stabilize from the induction of anesthesia and insertion of catheters for 30 min. After stabilization, baseline measurements were taken. Five percent of blood volume was withdrawn, followed by another 5%, and then in 10%-increments until death from exsanguination occurred. After withdrawal of 5% of blood volume, all pigs were considered volume responders (dPP>13%); dPP rose significantly from 6.1+/-3.3% to 19.4+/-4.2%. The regression analysis of stepwise hemorrhage revealed a linear relation between blood loss (hemorrhage in %) and dPP (y=0.99*x+14; R2=0.7764; P<.0001). In addition, dPP was the only parameter that changed significantly between baseline and a blood loss of 5% (P<0.01), whereas cardiac output, stroke volume, heart rate, MAP, central venous pressure, pulmonary artery occlusion pressure, and systemic vascular resistance, respectively, remained unchanged. We conclude that in an experimental hypovolemic pig model, dPP correlates well with blood loss.

Hypercapnia improves tissue oxygenation in morbidly obese surgical patients.

Risk of wound infection is increased in morbidly obese surgical patients, in part because a major determinant of wound infection risk, tissue oxygenation, is marginal. Unlike in lean patients, supplemental inspired oxygen (Fio2) only slightly improves tissue oxygenation in obese patients. Mild hypercapnia improves tissue oxygenation in lean patients but has not been evaluated in obese patients. We thus tested the hypothesis that mild hypercapnia markedly improves tissue oxygenation in morbidly obese patients given Fio2 80% during major abdominal surgery. Thirty obese patients (body mass index 61.5 +/- 17 kg/m2) scheduled for open gastric bypass were randomly assigned to normocapnia (n = 15, end-tidal Pco2 35 mm Hg) or hypercapnia (n = 15, end-tidal Pco2 50 mm Hg); Fio2 was 80%. Anesthetic management and other confounding factors were controlled. Tissue oxygen tension was measured subcutaneously at the upper arm using a polarographic probe in a silastic tonometer. Demographic characteristics, cardiovascular measurements, and Pao2 (222 +/- 48 versus 230 +/- 68 mm Hg in normocapnic versus hypercapnic; mean +/- sd; P = 0.705) were comparable in the groups. Tissue oxygen tension, however, was greater in hypercapnic than in normocapnic patients (78 +/- 31 versus 56 +/- 13 mm Hg; P = 0.029). Mild hypercapnia increased tissue oxygenation by an amount believed to be clinically important and could potentially reduce the risk of surgical wound infection in morbidly obese patients.

Caudal clonidine prolongs analgesia from caudal S(+)-ketamine in children.

UNLABELLED: We performed a prospective randomized double-blinded study to test preservative-free S(+)-ketamine alone or in combination with clonidine for intra- and postoperative caudal blockade in pediatric surgery over a 24-h period. Fifty-three children (1-72 mo) scheduled for inguinal hernia repair were caudally injected with either S(+)-ketamine 1 mg/kg alone (Group K) or with additional clonidine (Group C1 = 1 microg/kg; Group C2 = 2 microg/kg) during sevoflurane anesthesia via a laryngeal mask. Intraoperative monitoring included heart rate, blood pressure, and pulse oximetry; postoperative monitoring included a pain discomfort scale and a sedation score. No additional analgesic drugs were required during surgery. The mean duration of postoperative analgesia was 13.3 +/- 9.2 h in Group K, 22.7 +/- 3.5 h in Group C1, and 21.8 +/- 5.2 h in Group C2 (P < 0.0001, Group K versus other groups). Groups C1 and C2 received significantly fewer analgesics in the postoperative period than Group K (15% and 18% vs 63%; P < 0.01). The three groups had similar postoperative sedation scores. We conclude that the combination of S(+)-ketamine 1 mg/kg with clonidine 1 or 2 microg/kg for caudal blockade in children provides excellent analgesia without side effects over a 24-h period. IMPLICATIONS: Caudally administered preservative-free S(+)-ketamine combined with 1 or 2 microg/kg clonidine provides excellent perioperative analgesia in children and has minimal side effects.