Spinal Anesthesia for Pyloromyotomy: Voodoo or Can do?

Transcription

1 Spinal Anesthesia for Pyloromyotomy: Voodoo or Can do? Ann Lawrence, DO, Assistant Professor of Anesthesiology and Pediatrics, Division Chief Emily Stebbins, MD, Assistant Professor of Anesthesiology and Pediatrics The University of Vermont Saturday, April 2, 2016; 4:20pm-5:30pm PBLD Table #: 32 GOALS: Recognize appropriate types of cases for selection of spinal anesthesia. Discuss benefits of spinal anesthesia over general anesthesia. Recognize that not every surgeon has the ability to practice under spinal anesthesia. Recognize spinal anesthesia as an acceptable alternative to general anesthesia in nonformer premature infants. Discuss appropriate positioning, local anesthetics and doses, and management of spinal anesthesia for various types of procedures, with specific emphasis on pyloromyotomy. CASE STEM: A male infant was born at 41 weeks gestation and admitted to the NICU for 24 hours to rule out sepsis due to maternal prolonged rupture of membranes. He was monitored and discharged home without any intervention. He presents to the emergency department at 6 weeks of age, now weighing 3.4 kilograms and with a history of projectile emesis. He is diagnosed with pyloric stenosis and admitted for intravenous fluid hydration and pyloromyotomy. Case stem questions: Describe the anatomic abnormality of pyloric stenosis. Discuss its mechanical and physiologic consequences. What is/are the most common electrolyte abnormality(ies) found in patients with pyloric stenosis? Is this an emergent surgical intervention? Why or why not? Provide a rationale for when it is appropriate to proceed to the operating room, which may include patient, family, surgeon and staff considerations. Preoperative assessment: The patient has no known drug allergies and has never had surgery. There is no family history of anesthetic complications. Laboratory values have normalized. On physical exam, he is vigorous, alert, with normal vital signs, has normal fontanels, and an unremarkable cardiopulmonary exam. He has a 24g IV in his left foot infusing D 5 NS at maintenance. After reviewing the chart, you speak to the parents to obtain consent for anesthesia. They are nervous about their son undergoing general anesthesia after reading a news story about the potential risks of general anesthesia in infants 1. They ask if there is any other way to perform the anesthesia for this procedure.

2 Preoperative assessment questions: Distinguish between open and laparoscopic approach to pyloromyotomy, including anesthetic techniques that can be utilized for each. Weigh risks and benefits of spinal anesthesia for each surgical approach. Describe how you will structure a conversation with the parents regarding their concerns, addressing both short and long term potential consequences. Discuss the concept of neuroapoptosis in animal models who have undergone general anesthesia. How does this information translate into clinical practice and how will you incorporate this into your preoperative discussion, if at all? If this patient was delivered at 28 weeks instead of term and has bronchopulmonary dysplasia, would a spinal anesthetic be better than a general anesthetic? Defend your answer. Consent and induction: After a long discussion with the parents, they elect to have the procedure performed under spinal anesthesia. The surgeon is at the bedside, agrees, and consents are signed. The patient is transported to the operating room. A gastric suction catheter is placed and gastric contents are aspirated in three positions. Standard ASA monitors are placed and the patient is positioned for placement of the spinal. Consent and induction questions: Describe how the patient will be positioned for placement of spinal. Consider lateral vs. sitting, as well as how you will instruct staff to maintain position. What local anesthetics can be used? For each local anesthetic, provide concentration, dose, and adjuvants. Discuss the signs and symptoms of high spinal in infants. What strategies can you use to minimize risk of high spinal in infants? Intraoperative The spinal is placed and the infant is positioned on the table. After following protocol for prepping, draping and completing the pre-surgical checklist, surgeon makes skin incision. Approximately 30 minutes after intrathecal injection, the infant starts crying and moving his upper extremities, causing movement of the abdomen. The surgeon requests that you do something to stop the moving because he is ready to make the pyloric incision. Intraoperative questions: Assuming that the patient s lower extremities are still flaccid, what strategies could be employed to calm the infant? Is there a place for IV medications? If so, what will you use? At what point would you consider converting to general anesthesia? The infant calms down with a pacifier and falls asleep. The procedure is completed uneventfully. He is transported to the recovery room, where he begins to move his legs and appears comfortable. He is transferred to the post-operative surgical floor for overnight observation. MODEL DISCUSSION: Pyloric stenosis is the most common gastrointestinal disorder in children less than six months of age, although it typically occurs between two and eight weeks of age. Males are affected four

3 times more than females. Pyloric stenosis develops over time as the circumferential muscles of the pylorus thicken leading to gastric outlet obstruction. Infants present with projectile nonbilious emesis, resulting in a hypochloremic, hypokalemic metabolic alkalosis. The metabolic abnormalities of pyloric stenosis should be recognized and treated. Intravascular volume should be restored with correction of the underlying electrolyte abnormalities. Even after medical optimization and appropriate NPO time, infants with pyloric stenosis are still at high risk for aspiration. Pyloric stenosis is not a surgical emergency 2. Timing of surgical intervention should be considered and discussed between the surgeon, anesthesiologist and staff. One must consider if surgical intervention outside the hours of a fully staffed operating room is reasonable (i.e. evening or weekend hours). When the infant is medically ready for pyloromyotomy, the anesthesiologist should discuss the anesthetic options with the parents. Laparoscopic pyloromyotomy is more common than open pyloromyotomy and has faster time to full oral feeding and hospital discharge 2. The laparoscopic approach is associated with higher complication rate and increased cost. The majority of centers perform laparoscopic repair under general anesthesia, however, one institution has published a few cases of laparoscopic pyloromyotomy performed under spinal anesthesia with midazolam pre-treatment 3. The open technique can be performed under regional or general anesthesia, as one does not have to be concerned about elevated intra-abdominal pressure from laparoscopic equipment. If the surgeon is comfortable with an open technique, spinal anesthesia is a viable and safe option. After conferring with the surgeon to determine the operative plan, one can approach the parents to discuss the anesthetic plan. General anesthesia would be the most reasonable plan for laparoscopic pyloromyotomy. Either is reasonable for open pyloromyotomy. In our institution, we have a strong preference for spinal anesthesia and open pyloromyotomy. Infant spinal anesthesia has been preformed successfully at the University of Vermont on more than 2500 patients since the late 1970 s. Benefits of spinal anesthesia are hemodynamic stability, avoidance of airway manipulation with a full stomach, post-operative pain control, and minimal need for sedation. A long term benefit of spinal anesthesia is avoidance of general anesthesia, although the absolute benefit is not known. Over the past decade, it has become increasingly clear that all general anesthetic agents utilized in children are neurotoxic in laboratory animals. Animals exposed to general anesthetics and sedatives during infancy consistently demonstrate a marked increase in neuroapoptosis 4. Because it is not ethical to perform general anesthesia on an elective basis in children, current human studies are all observational in nature. Many of these observational studies, such as the ones done by Wilder at Mayo Clinic, Block at Iowa, and Hansen in Denmark, demonstrate an association between exposure to general anesthesia during early childhood and later cognitive deficit 5,6,7. Wilder and colleagues at the Mayo Clinic demonstrated a marked increase in the risk for learning disabilities in children exposed to more than one anesthetic prior to age four 5. Block examined a group of Iowa children exposed to general anesthesia during infancy for one of three routine surgeries 6. They found that one exposure to anesthesia was associated with a marked increase in the number of children with very poor academic achievement on elementary school academic achievement tests. In addition they demonstrated a relationship between length of anesthesia and diminished test score performance. Conversely, Hansen examined a large registry of Danish children and found no clear relationship between one

4 exposure to general anesthesia for inguinal hernia repair and impaired test performance in high school 7. A large multi-center study, The General Anesthesia Compared to Spinal Anesthesia Study (GAS), randomized healthy infants undergoing repair for inguinal herniorrhaphy to either general anesthesia or regional anesthesia. The enrollment is closed and in 2015 a preliminary evaluation of GAS study brought to light many advantages of infant spinal when compared to general anesthesia in infants undergoing repair for inguinal herniorrhaphy. This study concluded that regional anesthesia is associated with less early apnea, decreased hypotension, and lower postoperative oxygen desaturation when compared to general anesthesia 8. Although general anesthesia can be performed in any age, regional anesthesia is a great option for patients with pulmonary disease. At our institution, if an infant has a history of bronchopulmonary dysplasia and needs surgery, we prefer spinal anesthesia if possible. Benefits include lack of manipulation of pulmonary mechanics, as well as intra-operative and immediate post-operative pain control. Spinal anesthesia can be performed with an infant in the seated or lateral decubitus position. In either position an experienced assistant should hold the infant securely with the back flexed. In the seated position extreme neck flexion should be avoided since this may result in airway obstruction 10. To facilitate placement of the spinal in the lateral decubitus position, the head of the infant should be to the side of the operator s non-dominant hand and care should be taken to keep the infants body perpendicular to the OR table. The neonatal spinal cord ends at the third lumbar level; therefore it is recommended that the spinal be placed in the fourth or fifth lumbar spaces. After the infant is properly positioned the back should be washed with betadine solution for premature infants or infants less than 2 months or with chlorhexidine for infants greater than 2 months of age, and draped in a sterile fashion 11. A midline approach is used with either a 22G or a 25G short Quincke needle. Once CSF is obtained, local anesthetic is injected without checking for backflow pre- or post-injection. The local anesthetics that we use at our institution include hyperbaric tetracaine and isobaric bupivacaine doses of mg/kg 12. Adjuvants to these anesthetics have been described. Epinephrine wash is commonly used to increase the duration of the spinal anesthetic. Clonidine (1mcg/kg) added to bupivacaine has been shown to significantly increase the duration of the block, but it can also cause hypotension as well as postoperative sedation and apnea 13. Other adjuvants have been used with limited success. After the spinal is placed the needle is removed and the baby is quickly placed supine with a small towel under the head to avoid a high spinal. At this time avoid any maneuver that would place the baby in Trendelenburg position such as lifting the legs to place a cautery pad. Trendelenburg position can cause a high or complete spinal. Signs and symptoms of a high or a complete spinal include decrease respirations, apnea and loss of consciousness 14. Infants with high spinals are remarkably hemodynamically stable 15. Once the spinal has been placed, most children can be soothed by gentle stroking or by sucking on a pacifier dipped in glucose water. Many infants will even sleep lightly once they are comforted 15. If the infant continues to move his upper extremities or is crying, a small amount of sedation such as midazolam or propofol can be added, although this can significantly increase the incidence of postoperative apneas 16.

5 Infant spinal anesthesia is an ideal choice for infants undergoing surgery below the xyphoid that last 80 minutes or less 14. Parents should be informed of the possibility of converting to a general anesthetic if the spinal inadvertently travels too high, the surgery outlasts the duration of the local anesthetic, or the surgical conditions under spinal become less than optimal. References 1 Grady, Denise. Researchers Warn on Anesthesia, Unsure of Risk to Children. The New York Times. Feb 25 th, Article accessed 11/11/15. 2 Hammer, G., Hall, S., and David, PJ. Anesthesia for General Abdominal, Thoracic, Urologic, and Bariatric Surgery. In Smith s Anesthesia for Infants and Children. 8 th Edition. Elsevier, Philadelphia, PA Chapter 23, pages Islam S., et al. Feasibility of laparoscopic pyloromyotomy under spinal anesthesia. Journal of Pediatric Surgery. 2014;49: Brambrink, A.M., et al. Isoflurane-induced apoptosis of oligodendrocytes in the neonatal primate brain. Ann Neurol. 2012;72(4): Wilder RT, Flick RP, Sprung J, Katusic SK, Barbaresi WJ, Mickelson C, Gleich SJ, Schroeder DR, Weaver AL, Warner DO. Early exposure to anesthesia and learning disabilities in a population-based birth cohort. Anesthesiology 2009; 110(4): Block RI, Thomas JJ, Bayman EO, Choi JY, Kimble KK, Todd MM. Are anesthesia and surgery during infancy associated with altered academic performance during childhood? Anesthesiology 2012; 117(3): Hansen TG, Pedersen JK, Henneberg SW, Pedersen DA, Murray JC, Morton NS, Christensen K. Academic performance in adolescence after inguinal hernia repair in infancy: a nationwide cohort study. Anesthesiology 2011; 114(5): Davidson A.J, et al. Apnea after Awake Regional and General Anesthesia in Infants: The General Anesthesia Compared to Spinal Anesthesia Study Comparing Apnea and Neurodevelopmental Outcomes, A Randomized Controlled Trial. Anesthesiology. 2015;123: Williams, R.K., et al. The Safety and Efficacy of Spinal Anesthesia for Surgery in Infants: The Vermont Infant Spinal Registry. Anesth Analg 2006;102: Frawley G and Ingelmo P. Spinal anaesthesia in the neonate. Best Practice & Research Clinical Anaesthesiology. 2010;24: RelatedDrugLabelingChanges/ucm htm. Information accessed 12/18/ Brown TCK, Eyres RL, and McDougall RJ. Local and regional anaesthesia in children. British Journal of Anesthesia. 1999;83(1): Rochette A, et al. Clonidine prolongs spinal anesthesia in newborns: A prospective doseranging study. Anesth Analg. 2004;98: Gupta A and Saha U. Spinal anesthesia in children: A review. J Anaesthesiol Clin Pharmacol. 2014;30(1): Williams R and Abajian C. Spinal Anesthesia in Infants. Techniques in Regional Anesthesia and Pain Management. 1999;3(3): Kokki H. Spinal blocks. Pediatric Anesthesia. 2012;22:56-64.