spa meeting reviews
Emerging Surgical Technologies
By Sandra Kaufmann, MD
Joe DiMaggio Children’s Hospital
This session was moderated by Nina Deutsch, MD (Johns Hopkins, Baltimore) and featured three topics: nanotechnology and anesthesia, open vs endoscopic craniosynostosis repair and the use of 3D printing in airway surgery.
The first presenter was Sujatha Kannan, MD (Johns Hopkins, Baltimore) who discussed nanotechnology and its utilization in creating innovative drug delivery systems to treat neurologic injury. The talk commenced with an overview of nanoparticles and the challenges directing these particles through the Blood Brain Barrier (BBB) to desired target zones. More specifically, she discussed dendrimers, which are synthetic, biocompatible, tree-like polymers (5-10 nm) that are cleared intact from the circulation by the kidney. She then demonstrated the targeting ability of these molecules in that they accumulate in activated microglia in brain areas affected by cerebral palsy.
A brief review of the etiology of cerebral palsy followed, pointing out a correlation with maternal chorioamnionitis and immune dysregulation in the infant brain. She discussed the hypothesis that immune activation may be mediated by intracranial microglia in this disease process. These microglia cells play an important role in the developing brain as the resident immune cells, participate in remodeling and become activated in the presence of inflammation.
N-acetyl cysteine (NAC), having potent anti-inflammatory and anti-oxidant properties has been shown to reduce infarct volume and inflammation in animal models of stroke and cerebral ischemia. Conjugating NAC to the dendrimer, Dr. Kannan demonstrated that the NAC does not release in the plasma when conjoined, but instead travels through the BBB and gets released intracellularly in the microglia.
In impressive videos, Dr. Kannan demonstrated the effects of treatment with NAC-Dendrimer in fetal CP rabbit models. Following one dose of 10 mg/kg at birth, dramatic improvement in the motor function and locomotion was seen clearly five days after one treatment.
In summation, Dr. Kannan reviewed a novel approach of nanomedicine as a post natal therapy for a prenatal injury using a targeted therapy to either prevent or arrest fetal neural inflammation.
The second presenter was Petra M. Meier MD, DEAA (Boston Children’s Hospital, Boston) who reviewed the etiologies and different repair modalities for craniosynostosis. She reviewed the evolution of treatment through to today’s state of the art method of minimally invasive endoscopic strip craniectomy (ESC).
Dr. Meier initiated the talk with a review of the previous treatment methodologies for craniosynostosis. Surgical treatment began with strip craniectomies in 1890 by Lannelongue and Lane. This progressed to the classic, open full vault remodeling in the 1970s and now has returned to strip craniectomies. These, however, are performed in conjunction with post-operative orthotic molding and done at a much earlier age. Open surgery as compared to the minimally invasive ESC consists of a very exposed, mechanic surgery where bones are removed and replaced into a desired location with anesthesia risks that include massive blood loss, venous air embolism, airway complications and an extensive hospitalization. ESC is a suture release procedure whereby the skull shape is determined by brain growth instead of surgical placement and augmented by use of a molding helmet. The less invasive technique has been shown shown to have fewer complications with similar outcomes.
Dr. Meier presented a comparison chart of the standard strip craniectomy, calvarial vault remodeling and ESC. Of significance, ESC required less surgical time with significantly less blood loss (7% of EBV vs 100% for vault) and shorter hospital stay.
Therefore, Dr. Meier suggested altering standard anesthesia practice and, for ESC, not require an arterial line and to use two large bore intravenous lines. She still recommended PRBCs available in the OR as well as use of local anesthetic and Doppler monitoring.
She then reviewed the less prevalent use of surgical springs that are placed internally at the sight of the craniectomy to assist in the remodeling of the skull. Whereas the surgical outcomes results were positive, the springs required a second surgery approximately 4-6 months later for removal.
Lastly, Dr. Meier reviewed treatment of Unilateral Coronal Synostosis with ESC and orthosis and presented evidence that this treatment modality had improved facial asymmetry as compared to treatment with Facial orbital advancement. As well, the ophthalmologic outcomes were improved after 2 years with ESC.
The third presentation in this session was by Glenn Green, MD (University of Michigan/Division of Pediatric Otolaryngology, Ann Arbor) and Paul Reynolds, MD, FAAP (CS Motts Children’s, Ann Arbor) who discussed 3D printing and its applications for treatment of airway disease. The first point of discussion was an explanation of 3D printing which was described as a system to create an object “printed” from a computer model out of metal or plastic, with the intrinsic advantage of being able to craft customized devises within 24 hours of an MRI or CT scan. Dr. Green demonstrated the creation of multiple products such as prosthetics, surgical scaffolds, fitted CPAP masks as well as organs.
The main topic however, was the creation of airway stents to treat children with severe tracheal or bronchial collapse that were otherwise not extubatable. To date, these stents have been placed in four patients at their facility for a variety of disease states and the procedure consists of suturing an elongated, perforated omega shaped stent external to the airway thus pulling the airway open rather than placing the stent internally within the airway. Results have demonstrated significant improvement in all four patients.
Dr. Reynolds followed, discussing the challenges of providing anesthesia to these patients pre-procedurally, during the procedure and then in post- procedural evaluations. Prior to the stent creation, the children were evaluated with imaging studies and direct laryngoscopy and bronchoscopy. Anesthetic goals during the CT scan included avoiding atelectasis, recruitment after induction, specific TV and PEEP and breath holding during inspiration and expiration. DL bronchoscopies require spontaneous breathing with propofol infusion with the possible addition of ketamine and remifentanil. During the procedure itself, a DL bronch is performed before and after stent placement and care taken to have specific placement of the ET tube to avoid interference with the stent. Two of the four patients required cardiopulmonary bypass during stent placement.
In conclusion, Dr. Reynolds summed up the challenges which included but were not limited to difficulty with ventilation prior to stent placement, transportation with tenuous airways, desaturations with procedures, coordination of care, prolonged hospital stays and high narcotic and benzodiazepine requirements.