Arjunan Ganesh

Validation of the Bispectral Index Monitor for Measuring the Depth of Sedation in Children

The Bispectral Index (BIS) is an empirically calibrated number derived from adult electroencephalograph data that correlates with the depth of sedation in adults. We tested the hypothesis that the BIS score is a valid measure of the depth of pediatric sedation in a study designed to avoid limitations of a previously published report. BIS values from 96 healthy ASA physical status I–II children aged 1–12 yr undergoing sedation were continually recorded and electronically transferred to a computer. Two independent observers blinded as to BIS score evaluated sedation using the Observer’s Assessment of Alertness/Sedation (OAA/S) and the University of Michigan Sedation Scale (UMSS) at 3–5 min intervals. There was a significant correlation between BIS and UMSS and between BIS and OAA/S by both the Spearman’s rank correlation test and by prediction probability (P < 0.001). In children <6 yr, there was a significant correlation between BIS and the clinical sedation scores for subgroups undergoing invasive and noninvasive procedures (P < 0.001). There was also good agreement between the 2 independent observers who assessed clinical sedation scores (kappa = 0.51, P < 0.001). We conclude that the BIS monitor is a quantitative, nondisruptive and easy to use depth of sedation monitor in children.

Evaluation of ultrasound-guided radial artery cannulation in children

Objective: To compare ultrasound (US)-guided radial artery cannulation with the traditional palpation technique. Design: Prospective randomized study. Setting: Operating room in a tertiary care pediatric center. Patients: One hundred fifty-two children under 18 yrs of age requiring radial artery cannulation. Interventions: Patients were randomized to either 1) palpation or 2) US guidance technique for radial artery cannulation. Measurements and Main Results: The primary end point of the study was the time taken for attempted cannulation by the first operator at the first site. Secondary end points included the number of attempts at arterial cannulation, the number of cannulae used, and the need for additional assistance from another anesthesiologist. Eighty and 72 children were randomized to the palpation and the US-guided groups, respectively. There were no statistically significant differences in age, gender, weight, and systolic blood pressure between the two study groups. The designated first operator (20 pediatric subspecialty trainees and eight consultant anesthesiologists) had previous experience in US-guided arterial cannulation in <10 cases, with 94% having experience in <5 cases. Although the radial artery was eventually cannulated in all patients, the designated operator was successful at the first site of cannulation in only 66% and 69% in the palpation and US groups, respectively. There were no statistically significant differences between the groups in time to successful cannulation, total number of attempts, number of successful cannulations during the first attempt, or in the number of cannulae used for catheterization. Conclusions: US guidance did not facilitate faster cannulation of the radial artery in children in our study.

Pathophysiology and Management of Opioid-Induced Pruritus

Pruritus occurs frequently following opioid use, particularly after neuraxial administration. Although not life threatening, pruritus is discomforting and may decrease patient satisfaction. Even though the mechanism of opioid-induced pruritus is not yet fully understood, there is increasing evidence of the important role played by μ opioid receptors. Animal experiments pointing to the role of the μ opioid receptor and the efficacy of μ opioid receptor antagonists for opioid adverse effect prophylaxis and treatment have been replicated in several studies. Serotonin and dopamine D2 receptors, prostaglandins and spinal inhibitory pathways may also be involved in the genesis of pruritus.Several pharmacological agents have been used both for the treatment of established pruritus and in its prevention. Of these, μ opioid receptor antagonists have been most consistent in terms of attenuating opioid-induced pruritus but present problems in dose and administration. Other drugs, including mixed opioid receptor agonist-antagonists, serotonin 5-HT3 receptor antagonists, propofol, NSAIDs and D2 receptor antagonists, have also been demonstrated to be useful.This review summarises the current understanding of the mechanisms causing opioid-induced pruritus and the pharmacological therapies available to prevent and/or manage this disorder.

Prospective randomized observer-blinded study comparing the analgesic efficacy of ultrasound-guided rectus sheath block and local anaesthetic infiltration for umbilical hernia repair

BACKGROUND Umbilical hernia repair, a common day-surgery procedure in children, is associated with considerable postoperative discomfort. Possible modes of postoperative analgesia for umbilical hernia repair are rectus sheath block (RSB) and local anaesthetic infiltration of the surgical site (LAI). METHODS We undertook an observer-blinded, randomized, prospective, observational study to compare the efficacy of ultrasound-guided RSB and LAI in providing postoperative analgesia for umbilical hernia repair. Our primary objective was to compare the use of opioid medication between patients who receive RSB and those who receive LAI. Our secondary objectives were to compare the duration of analgesia based on time to first rescue analgesic, to compare the quality of analgesia based on revised FACES scale, and to determine the incidence of side-effects. RESULTS Fifty-two patients (26 in each group) completed the study. There was a statistically significant difference in the perioperative opioid medication consumption between the LAI group [mean: 0.13 mg kg(-1), confidence interval (0.09-0.17 mg kg⁻¹)] and the RSB group [mean: 0.07 mg kg⁻¹, confidence interval (0.05-0.09 mg kg⁻¹)] (P=0.008). When we compared the postoperative opioid consumption between the LAI group [mean: 0.1 mg kg⁻¹, 95% confidence interval (0.07-0.13 mg kg⁻¹)] and the RSB group [mean: 0.07 mg kg(-1), 95% confidence interval (0.05-0.09 mg kg⁻¹)] (P=0.09), there was a trend towards statistical significance between the two groups. The difference in time to rescue analgesic administration between the RSB group [49.7 (36.9) min] and the LAI group [32.4 (29.4) min] was not statistically significant (P=0.11). CONCLUSIONS This study demonstrates that ultrasound-guided RSB provides superior analgesia in the perioperative period compared with infiltration of the surgical site after umbilical hernia repair. In comparing only the postoperative period, analgesia provided by an ultrasound-guided RSB showed a trend towards statistically significant improvement compared with infiltration of the surgical site.

The effects of clonidine on postoperative analgesia after peripheral nerve blockade in children.

BACKGROUND:The effect of clonidine on the duration of sensory blockade after peripheral nerve blockade is controversial. We evaluated the effects of clonidine on the duration of sensory and motor block and analgesia time in children who underwent a variety of peripheral nerve blocks. METHODS:We reviewed the regional anesthesia database that contains data on children who underwent an infraclavicular, lumbar plexus, femoral, fascia iliaca or sciatic nerve block for postoperative analgesia at The Children’s Hospital of Philadelphia between October 2002 and December 2005. Patients were prospectively followed after the nerve block. RESULTS:Two hundred fifteen patients (47%) received either bupivacaine or ropivacaine local anesthetic (LA) and 220 (53%) a combination of local anesthetic and clonidine (LAC). The duration of sensory block was significantly longer in the LAC (17.2 ± 5 h) compared with that in the LA group (13.2 ± 5 h) (P = 0.0001). The increase in duration was independent from the type of peripheral nerve block, local anesthetic used and operation performed. The motor block duration was significantly longer in the LAC group (9.6 ± 5 vs 4.3 ± 4 h, P = 0.014). Two patients in the LAC and one in the LA group experience prolonged numbness (max 72 h). No paresthesia or dysesthesia was observed. CONCLUSION:The addition of clonidine to bupivacaine and ropivacaine can extend sensory block by a few hours, and increase the incidence of motor blocks.

Low-dose intrathecal morphine for postoperative analgesia in children.

BACKGROUND: We evaluated the efficacy and safety profile of low-dose (4–5 mcg/kg) intrathecal morphine for postoperative pain management after various surgical procedures in children. METHODS: We reviewed the pain management service database and the medical records of patients who received low-dose intrathecal morphine for postoperative analgesia at The Childrens Hospital of Philadelphia between October 2003 and March 2006. Patients had been prospectively followed for 24–48 h after the intrathecal morphine administration. RESULTS: The medical records of 187 patients were examined. The mean age was 5.6 ± 5.1 yr (median 4.0, interquartile range [IQR] 1.0–10.0). The median maximum pain score during the first 24 h in patients evaluated by the FLACC score and in those evaluated by the numeric verbal rating scale, was 0 (IQR 0–3) and 0 (IQR 0–4), respectively. The mean time to first rescue opioid was 22.4 ± 16.9 h (range: 0–48 h, 95% CI: 19.9–24.8 h). During the first 24 h after surgery, 70 patients (37%) did not receive any opioids (oral or IV). Of the 117 patients who received opioids, 59 (50%) were managed with oxycodone only. Pain was managed with ketorolac in 33% of patients, either alone (11%) or in combination with IV or oral opioids (22%). The incidence of nausea or vomiting, pruritus, and urinary retention was 32%, 37%, and 6% respectively. One patient had transient postdural puncture headache, while two patients received supplemental oxygen beyond the first 60 postoperative minutes to manage occasional episodes of hypoxemia. No severe respiratory depression requiring assisted ventilation or naloxone administration was observed. CONCLUSION: We conclude that low-dose intrathecal morphine in the pediatric population can be a useful and safe adjunct for postoperative analgesia.

Evaluation of the VIA Blood Chemistry Monitor for Glucose in Healthy and Diabetic Volunteers.

Background: Manual methods of blood glucose monitoring are labor-intensive, costly, prone to error, and expose the caregiver to blood. The VIA® blood chemistry monitor for glucose can automatically measure plasma glucose (PG) every 5 minutes for 72 hours using blood sampled from a peripheral vein/artery or a central vein. Methods: VIA performance was evaluated in eight normal and five type 1 diabetic (T1DM) subjects in 15 separate experiments. The VIA device was connected to a peripheral vein and reported a PG value every 5 minutes during each 510-minute experiment. Blood samples were collected manually every 10 minutes and assayed using a HemoCue® β-glucose analyzer (HC). Whole blood HC measurements were corrected to PG values. Paired HC/VIA measurements (n = 717) were analyzed. Results: Mean PG was 90 ± 14 and 96 ± 12 mg/dl in normal subjects and 194 ± 64 and 173 ± 48 mg/dl in T1DM subject as measured by the HC and VIA, respectively. Clark error grid analysis revealed 86% points in zone A, 11% points in zone B, and 2% points in zone D. Linear regression analysis yielded the following equation: VIA = 0.732 × HC + 30.5 (r 2 = 0.954). Residual analysis revealed a glucose-dependent bias between the HC and the VIA. VIA data were transformed using the linear regression equation to correct for bias. After the correction, the mean absolute relative difference between the VIA and the HC was less than 10%, and 99.6% of data were in zones A and B. The VIA was able to sample blood automatically every 5 minutes for more than 8 hours in the laboratory setting. On average, the VIA reported glucose values for 94% of the samples it attempted to obtain. Conclusions: This study demonstrated that the VIA blood chemistry monitor for glucose can reliably sample blood frequently for a prolonged period of time safely and effectively in diabetic and nondiabetic volunteers. Agreement between the two devices was the closest at normal glucose concentrations. After correcting for a glucose-dependent bias between the devices, the MARD was consistently less than 10% for all glucose ranges.

Ambulatory continuous peripheral nerve blocks in children and adolescents: a longitudinal 8-year single center study.

BACKGROUND:Although the role of regional anesthesia in pediatric patients has been increasing over the last few years, there are only a few small case series that describe the use of ambulatory continuous peripheral nerve blocks (CPNBs) in this patient population. In this report, we describe our experience with the use of ambulatory CPNBs in 1285 children. METHODS:Data were collected for consecutive children who had a CPNB placed between January 2005 and December 2011 at The Children’s Hospital of Philadelphia from the departmental regional anesthesia database. Data collected included demographics, the site of catheter placement and technique of nerve block, presence of sensory/motor blockade, use of perioperative opioids, and any complications related to CPNBs. RESULTS:Continuous infusions of local anesthetics were administered via the catheters in 1285 outpatients. The mean duration of the CPNB was 50.7 ± 14.4 hours (mean ± SD). Among patients discharged home with the CPNBs, 969 (75.4%) of the patients required either no supplemental opioids or oral opioids only on an “as needed” basis in the postoperative period (confidence interval, 73.0%–77.8%). Two patients were readmitted for IV pain management after they were discharged home with the CPNB catheters. No neurological deficit related to the CPNBs was identified in any of the patients at their 6-month follow-up with the orthopedic surgeon (confidence interval, 0%–0.29%). CONCLUSION:This audit of 1285 children shows ambulatory CPNBs can provide postoperative analgesia and may reduce the need for inpatient parenteral opioid therapy.

Hyperkalemic cardiac arrest after cardiopulmonary bypass in a child with unsuspected duchenne muscular dystrophy

Adverse reactions to volatile anesthetics and depolarizing muscle relaxants can occur in patients with Duchenne muscular dystrophy (DMD) resulting in acute rhabdomyolysis and hyperkalemia. We report a case of hyperkalemic cardiac arrest after cardiac surgery using cardiopulmonary bypass in a child with unsuspected DMD. Early diagnosis and management of hyperkalemia resulted in a successful outcome. Genetic testing confirmed the diagnosis of DMD. We recommend a thorough preoperative investigation, including creatine kinase estimation, in children with a history of unexplained motor delay.

Intraarticular bupivacaine-clonidine-morphine versus femoral-sciatic nerve block in pediatric patients undergoing anterior cruciate ligament reconstruction

We hypothesized that combined femoral-sciatic nerve block (FSNB) offers better analgesia with fewer side effects than intraarticular infiltration (IA) in children undergoing anterior cruciate ligament (ACL) reconstruction. Thirty-six children undergoing ACL reconstruction were randomized to FSNB or IA. FSNB patients had FSNB with bupivacaine (0.125%)-clonidine (2 &mgr;g/kg), whereas IA patients received bupivacaine (0.25%)-clonidine (1 &mgr;g/kg)-morphine (5 mg). Postoperatively, analgesia was provided with patient-controlled analgesia and rescue morphine. Patient demographics were similar. FSNB patients required less intraoperative fentanyl (50 ± 40 &mgr;g versus 80 ± 50 &mgr;g; P = 0.04). Visual analog scale score for FSNB was smaller than IA in the recovery room (1.8 ± 3 versus 5.4 ± 3; P = 0.0002) and during the first 24 h (1.6 ± 1 versus 2.9 ± 2; P = 0.01)). FSNB morphine use in the first 18 h was less (7 ± 13 mg versus 21 ± 21 mg; P = 0.03). Fewer FSNB patients vomited (11% versus 50%; P = 0.03). IA patients required morphine patient-controlled analgesia sooner. After ACL reconstruction in children, FSNB with bupivacaine-clonidine provides better analgesia with fewer side effects than IA with bupivacaine-clonidine-morphine.