spa meeting reviews
Outcome Data in Pediatric Anesthesia - How will it affect your practice today?
By Dean Laochamroonvorapongse, MD, MPH
OHSU Doernbecher Children’s Hospital
This session was moderated by Johan Diedericks MMed(Anes), FCA(SA), BA (University of the Free State, South Africa) and presented data from three clinical registries:
- North American Fetal Therapy Network (NAFTNet),
- Pediatric Craniofacial Surgery Perioperative Registry (PCSPR), and
- Difficult Airway Database.
All three registries were created to collect multicenter data for relatively infrequent clinical scenarios and surgical procedures in order to improve patient care and provide direction for future research.
The first presenter was Debnath Chatterjee MD (Children’s Hospital of Colorado, Aurora), Director of Fetal Anesthesia at Colorado Fetal Care Center. NAFTNet oversees several registries, collects anonymously submitted data, and provides peer review of study proposals. Dr. Chatterjee’s presentation focused on research arising from two of NAFTNet’s registries:
- Fetal myelomeningocele repair registry and
- Complicated monochorionic twin pregnancy registry.
Myelomeningocele is the most common neural tube defect and is characterized by a cleft in the vertebral column, resulting in variable motor, sensory, and cognitive deficits. Hydrocephalus requiring VP shunt occurs in 70-90% of patients. There is growing evidence supporting a “two hit” hypothesis as the etiology, with failure of neurulation compounded by secondary damage acquired in utero. The surgical approach for fetal myelomeningocele repair consists of a pfannenstiel incision followed by hysterotomy, with a stabilizing device placed on the uterus. The fetus is given rocuronium, and the myelomeningocele is repaired in layers. An alloderm graft is placed over large defects, with definitive repair postnatally. Anesthetic goals include controlled uterine hypotonia with high-dose inhaled anesthetic, maintaining uteroplacental blood flow, and maintaining uterine volume with amnioinfusion. With this procedure, there is a 30% risk of preterm birth and 10% risk of fetal bradycardia. Maternal risks include chorioamniotic separation and uterine dehiscence at delivery.
The Management of Myelomeningocele Study (MOMS- NEJM 2011) conducted from 2003-2010 randomized women to prenatal myelomeningocele repair before 26wks gestational age or standard postnatal repair across three fetal surgery centers. Primary outcomes included death, need for VP shunt by age 12mos, and composite mental development and motor function scores. The trial was stopped early for efficacy of prenatal surgery, with only 40% prenatal surgery patients requiring VP shunt compared to 82% of the postnatal group. There were also significantly improved mental development scores, ability to walk without orthotics, and decreased hindbrain herniation in the prenatal surgery group.
The fetal myelomeningocele repair registry is a prospective multicenter database with approximately 200 cases entered per year. An analysis of 100 fetal myelomeningocele repairs performed at CHOP from 2011-2014 showed an average gestational age of 23.4wks for repair and delivery at 34.4wks. Outcomes were comparable to those in the MOMS trial, which suggests that experienced fetal surgery centers will have similar results.
Ten percent of all twin pregnancies are monochorionic, diamniotic. These pregnancies are high risk for preterm delivery and complications, including twin-to-twin transfusion syndrome (TTTS), twin anemia/polycythemia sequence, and twin reversed arterial perfusion sequence. The complicated monochorionic twin pregnancy registry is a retrospective and prospective multicenter database with each center enrolling approximately 50 patients annually.
Dr. Chatterjee then focused on TTTS, which occurs in 5-15% of monochorionic pregnancies, with 80% mortality if left untreated. 900 cases of TTTS were diagnosed in 2013. Diagnostic criteria include growth discordance, oligohydramnios in the donor twin, and polyhydramnios in the recipient. There is transfer of vasoactive mediators renin and endothelin-1 to the recipient twin, leading to AV valve dysfunction and cardiomyopathy on echocardiogram in the recipient twin. The Quintero Staging System is used to classify severity of TTTS, and maternal calcium channel blockers may be used to treat the recipient twin.
Treatment options of TTTS include serial amnioreduction to improve uteroplacental blood flow and selective fetoscopic laser photocoagulation (SFLP), which is performed under regional anesthesia with IV sedation. Dr. Chatterjee then showed a video of SFLP, which involves placing a trocar into the uterus, mapping of placental vessels with estimation of placental sharing, and applying a 60W diode laser to abnormal vascular connections. In a 5 year multicenter, prospective randomized controlled trial of 40 women, Crombleholme et al. (Am J Obstet Gynecol 2007) could not conclusively determine whether amnioreduction or SFLP was a superior treatment modality. In conclusion, NAFTNet seeks to harness the collaborative power of research to answer these difficult questions involving rare cases.
The second presentation was by Paul Stricker MD (Children’s Hospital of Philadelphia, Philadelphia), who spoke about the Pediatric Craniofacial Surgery Perioperative Registry (PCSPR) and its potential to establish multicenter benchmarks, improve care for craniosynostosis patients, and generate hypotheses for future research. Currently, most information regarding management of craniosynostosis is disseminated via single center data or by word of mouth at meetings, which Dr. Stricker compared to a “collection of postcards.” He reiterated that this is a unique set of patients undergoing an elective, life-changing procedure that places them at risk for hemorrhagic hypovolemia, venous air embolism, loss of airway, and hyperkalemic cardiac arrest from massive transfusion.
The PCSPR is unfunded work created with data from the Pediatric Craniofacial Collaborative Group, a group of 29 U.S. and Canadian centers of varying sizes. All data is de-identified and entered into an online database. Since this is considered a quality improvement activity, it is not subject to IRB oversight. An executive committee provides oversight, with multiple layers of auditing to ensure quality data and minimize enrollment bias. Approximately 1400 cases have been entered to date.
Dr. Stricker then presented results from the Multicenter Benchmarking Study of 726 registry patients undergoing fronto-orbital advancement with reconstruction, mid/posterior cranial vault, and total cranial vault reconstruction. Median estimated blood loss was 71% of EBV for the 538 patients ≤24 months of age, with a median total donor blood exposure of 1 unit. This is likely because one unit of blood accounts for a large proportion of each patient’s EBV. Similar results were obtained when the averaged data from each reporting institution was given equal weight. In contrast to this, previously conducted single center studies reported the EBL for cranial vault reconstruction to be anywhere from 82% to 150% of EBV. Three cardiac arrests were reported (0.4% of patients), and no deaths occurred.
With regards to anesthetic monitors and technique, the Multicenter Benchmarking Study found that 18% of cases used CVP monitoring, 18% used precordial Doppler, and 8% used thromboelastography (TEG). 8% of patients required a vasoactive infusion. In terms of blood conservation techniques, cell saver was used for 12% of patients, one patient received recombinant EPO, and one patient had normovolemic hemodilution. Only 5% (26/538) of patients ≤24 months old did not receive blood transfusion and this subset of patients was distributed across all institutions. It is interesting to note that 50% of these transfusion-free patients received antifibrinolytics and cell saver was used in only 12% of transfusion-free cases. There was no difference in calculated blood loss in patients receiving antifibrinolytics compared to those receiving none.
The speaker finished by drawing attention to the fact that our ability to improve care pale in comparison to the impact of “Factor XIV,” i.e., surgical attention to hemostasis and advances in surgical techniques and technology. Ultimately, the PCSPR is observational data and cannot establish cause and effect. Future research targets for the registry include minimizing unnecessary labs and tracking ICU management for this challenging group of patients.
Although airway management is common, there are very few large reports, with most of the available literature being single center reports. Dr. John Fiadjoe MD (Children’s Hospital of Philadelphia, Philadelphia) concluded this session with an engaging presentation about the Difficult Airway Database, a web-based registry created to better define outcomes for patients with challenging airways. For this database, a difficult airway is defined as: 1. Grade III or IV view on direct laryngoscopy (DL) by the attending anesthesiologist, 2. DL is impossible (laryngoscope blade cannot be placed), 3. If DL has failed within a six month period, and 4. If DL is possible but felt to be harmful in a patient with suspected difficult airway (e.g. neonatal Pierre Robin sequence). Severe complications recorded include hypoxemia (SpO2 < 90% for >40s or a 10% decline for >40s), bronchospasm, laryngospasm, esophageal intubation, severe airway trauma, and cardiac arrest.
Four large pediatric hospitals are currently contributing data to the Difficult Airway Database, with approximately 1200 patients accumulated since 2012. In terms of demographic information, their age ranges from birth to 17 years, 58% are male, and most are ASA 3. The majority of patients weigh 0-10kg, 86% have an abnormal airway exam, and 72% are syndromic, with Pierre Robin sequence being most common. 90% of registry patients had their airways managed in the OR; not unexpectedly, patients managed outside the OR had a higher likelihood of severe complications.
Dr. Fiadjoe found that the first and second attempt at intubation was most likely to be performed by a trainee, with the attending anesthesiologist taking over for the third intubation attempt. No association was found between the number of years experience an attending anesthesiologist had and success or complication rates. Direct laryngoscopy was the most common technique employed for first and second intubation attempts, while a GlideScope or fiberoptic bronchoscope was used for the majority of third intubation attempts. However, for some patients, trainees were still performing the fifth intubation attempt. In addition, up to fourteen direct laryngoscopy attempts were reported for a single patient. Dr. Fiadjoe questioned the safety of these practices. Despite the prominence of the LMA in the ASA Difficult Airway Algorithm, 14% of registry patients were found to have inadequate ventilation (tidal volume <5mL/kg) despite placement of a supraglottic airway device.
After polling the audience, Dr. Fiadjoe revealed that a surprising 40% of database patients were paralyzed for airway management, with only 30% of patients maintained on spontaneous ventilation. There was no difference in complication rates for patients maintained on controlled ventilation compared to those breathing spontaneously. Three patients were impossible to ventilate, and these patient had either cervical spine abnormalities or micrognathia.
The data suggest that the most vulnerable group of difficult airway patients is those weighing less than 10kg. These patients were three times more likely to have severe complications and accounted for eight of the fifteen patients that suffered from cardiac arrest. Furthermore, patients <10kg were four times more likely to become hypoxemic during airway management and were less likely to be successfully intubated (29% vs. 40% of patients >10kg). While there was no difference in first pass success for GlideScope, freehand fiberoptic, and fiberoptic intubation through a supraglottic airway device for patients >10kg, fiberoptic intubation through a supraglottic airway device was more likely to be successful on the first attempt in patients <10kg (45% vs. 38%). Difficult Airway Database complication rates are likely to be an underestimate given the nature of self-reported, unobserved data.
Dr. Fiadjoe concluded his presentation by showing the audience a video of a fire rescue squad expertly performing a training exercise and compared our difficult airway patients where laryngoscopy fails to people trapped in burning buildings. He emphasized the need for us to practice advanced airway management techniques in those with normal airway anatomy. Future quality improvement efforts resulting from Difficult Airway Database include the use of high flow nasal cannula to provide oxygenation during intubation attempts and the creation of a web-based video library of difficult airway techniques for “just in time” review.