literature reviews
Journal Review
By Elizabeth S. Yun, MD
University of Wisconsin School of Medicine
Madison, WI
In 2015, the Canadian Journal of Anaesthesia published several articles on a variety of pediatric anesthesia issues. This review highlights the original investigations published during the year.
The first article, A randomized comparison between the i-gel and the air-Q supraglottic airways when used by anesthesiology trainees as conduits for tracheal intubation in children by Jagannathan, N et al., hypothesized that the air-Q would have a higher success rate for fiberoptic (FOB) guided intubations by trainees compared to the i-gel. Ninety-six patients scheduled for elective surgery were randomized to the air-Q or i-gel group. Anesthesia trainees were defined as a resident or fellow who had never attempted FOB guided intubations in children. After induction and placement of the SGA, three time points were measured with the start time noted as the removal of the face mask to the time to first glottis view, time to carinal view, and time to successful tracheal intubation. The duration of time ended at confirmation with end tidal CO2.
Trainees had three attempts for successful intubation. A failed attempt was defined as any oxygenation desaturations, any time the bronchoscope had to be withdrawn completely or a greater than three minutes per attempt. After a successful intubation, the supraglottic (SGA) airway was removed using a second endotracheal tube as a stabilizer and the time from disconnection from the circuit to observation of ETCO2 was noted. Twenty-four trainees participated in this study. All SGAs were placed on the first attempt with i-gels associated with more placement problems compared to the air-Q. The times for obtaining glottic and carinal views as well as overall time were not significantly different with either device. The time for removal of the SGA device was also similar for both groups although the i-gel group had more problems at this stage. The authors acknowledged the limitations of the study including possibility of a different outcome in patients with difficult airways, the use of trainees versus experts for airway management, the use of verbal cues to trainees by the expert study investigators and non-blinded data collection.
In conclusion, the authors suggested that i-gel was an acceptable alternative to the air Q. However, they suggested that the air Q might still be the preferred airway because its wider airway tube better accommodated a cuffed ETT.
The article, Celecoxib pharmacogenetics and pediatric adentosillectomy: a double blinded randomized controlled study by Murto K et. al. studied the analgesic efficacy of celecoxib for treating postoperative pain after a pediatric adentosillectomy. They noted that celecoxib, a cyclooxygenase-2-specific inhibitor NSAID that preserves platelet function, is an effective opiate sparing analgesic in adult patients with less side effects compared to other NSAIDs. Therefore, the authors wanted to see if a twice daily dose of celecoxib for pediatric patients, a protocol used for adult patients, would reduce acute postoperative pain, decrease the amount of other analgesics and improve functional recovery. They also evaluated the role of cytochrome P450 2C9 allele as a genetic marker for reduced celecoxib metabolism.
Two hundred and eighty two children, ages 2-18 years undergoing elective surgery, were randomized to receive either oral celecoxib or placebo. Each patient received an adult dose equivalent of either the placebo or celecoxib preoperatively (6 mg/kg) followed by a lower dose (3 mg/kg) given two times per day for five doses postoperatively. Oral acetaminophen and rescue morphine were also allowed in the postoperative period. Blood work for the genetic marker was drawn during the surgery. In the PACU, pain and delirium were assessed with modified CHEOPS and numerical rating. Emergence delirium was measured with the PAED score. On discharge, parents and patients were given a diary to record the patients’ pain, other analgesic use and quality of life measures.
The authors found that there was a modest but clinically significant decrease in postoperative pain with celecoxib. They also suggested that rebound in pain after celecoxib was stopped might be due to differences in celecoxib’s different pharmacokinetics in children. They did not see any increase in complications from bleeding. They acknowledged the limitations of the study including high parental refusal rate and the bias of using a once daily global report of pain. The authors also noted that the study was underpowered for measuring celecoxib safety and the CYP2C9 genotype influence on analgesia.
The authors concluded that celecoxib provides early modest pain relief but analgesic efficacy was limited when adult dosing was used. Further work is needed to determine what the celecoxib dose and schedule would work for longer pain control in children.
The impact of pneumoperitoneum and Trendelenberg positioning on respiratory mechanics during laparoscopic pelvic surgery in children: a prospective observational study by Neira VM et. al., examined changes in respiratory system compliance and pulmonary function due to a 12 mmHg pneumoperitoneum and a 20 degree Trendelenburg positioning under pressure control ventilation.
Fifteen patients undergoing pelvic laparoscopy surgery were recruited. Patients received oral acetaminophen preoperatively and underwent a standard inhalational induction with sevoflurane. After IV access was obtained patients received propofol, rocuronium and fentanyl and were intubated with a cuffed endotracheal tube. Patients were placed on pressure controlled ventilation with settings of peak inspiratory pressures (PIP) of 10-15 cmH2O and positive end expiratory pressure of 5 cnH2O. These settings, along with respiratory rate (RR) were titrated to achieve a tidal volume (VT) of 6-10 ml/kg and an ETCO2 of 35-40 cmH2O. The respiratory parameters of PIP, expired VT, RR MV, ETCO2, and SpO2 were measured at several points throughout the case. These points included a baseline set in the supine position, after pneumoperitoneum insufflation, the addition of Trendelenburg, at deflation of the pneumoperitoneum and post deflation. Dynamic compliance of the respiratory system (Cdyn/kg), the primary outcome, was calculated using the formula Cdyn= VT/(PIP-PEEP) at each of these points.
The authors found that Cdyn/kg decreased significantly after the pneumoperitoneum was started. Trendelenburg however only had a minor effect. They noted that PIP had to be increased to achieve an acceptable VT at both time points with a higher increase occurring with Trendelenberg. As a result of these changes, MV also decreased. ETCO2 levels tended to rise with insufflation and significantly increased with Trendelenberg although it remained at the acceptable range. The authors noted the limitations of the study including a small heterogeneous patient population, no measurement of intrapulmonary pressure and the observational nature of the study.
They concluded that significant changes in Cdyn and lung mechanics occur during laparoscopic urological procedures. The pnueumoperitoneum had its greatest effect on Cdyn and lung mechanics. Trendelenburg on the other hand reduced VT and increased ETCO2.
The final article, A naloxone admixture to prevent opioid induced pruritus in children: a randomized controlled trial by West N, et al. theorized that a mixture of naloxone and morphine would prevent opioid induced pruritus in patients without affecting analgesic efficacy. They used a mixture of naloxone 12 ug per 1 mg of morphine per 1 ml of normal saline given to patients as either a continuous infusion or as a PCA depending on the clinical situation.
Ninety-two participants, ages 8-18 years, were randomized to receive this admixture or a control solution of morphine 1 mg/ml without naloxone. Other medications ordered followed the institution’s acute pain service protocol with diphenhydramine as the rescue anti pruritus drug. Patients assessed the severity of their pruritus using a modified color analogue scale. Incidence of pruritus was assessed every four hours by patient report and use of rescue antipruritic medication. Opioid use was measured from volume of continuous infusion used and PCA use. Based on their findings, the authors did not see a significant difference between incidence and severity of pruritus and opioid utilization in the two groups. They observed that patients receiving a continuous infusion had less pruritus compared to the PCA group. They suggested several limitations of the study that might have affected the outcome. For instance, the dose of naloxone in the admixture was at a sub therapeutic level. The use of intraoperative morphine before the start of the infusions may have had an impact on pruritus scores. Several patients also received and its antipruritic properties may have skewed some of the outcome data.
The authors concluded that a naloxone-morphine solution did not decrease the incidence of pruritus. While a larger study might find an optimal dose mix, the unpredictable range of postoperative morphine dose may preclude creation of an acceptable mixture. The authors suggested that a continuous separate naloxone infusion started before the administration of opioids would be the best treatment for opioid induced pruritus.
References
- Jagannathan N, Sohn L, Ramsey M, Huang A, Sawardekar A, Suquera-Ramos L, Kromrey L, De Oliveira GS. A randomized comparison between the i-gel and the air-Q supraglottic airways when used by anesthesiology trainees as conduits for tracheal intubation in children. Can J Anaesth (2015) 62: 587-594.
- Murto K, Lamontagne C, McFaul C, MacCormick J, Ramakko KA, Aglipay M, Rosen D, Vaillancourt R. Celecoxib pharmacogenetics and pediatric adentosillectomy: a double blinded randomized controlled study. Can J Anaesth (2015) 62: 785-797.
- Neira VM, Kovesi T, Guerra L, Campos M, Barrowman N, Splinter WM. The impact of pneumoperitoneum and Trendelenburg positioning on respiratory system mechanics during laparoscopic pelvic surgery in children: a prospective observational study. Can J Anaesth (2015) 62: 798-806.
- West N, Ansermino M, Carr RR, Leung K, Zhou G, Lauder GR. A naloxone admixture to prevent opioid induced pruritus in children: a randomized controlled trial. Can J Anaesth (2015) 62: 891-900.
