Presented at ASA, October 24, 2015
Emmett E. Whitaker, M.D., Bruno Bissonnette, M.D., Joseph Tobias, M.D., Tanner L. Koppert, B.S., Fievos L Christofi, Ph.D.
Nationwide Children’s Hospital, Columbus, Ohio , United States
Background:
The effect of anesthetics on the developing brain has received considerable attention recently, and it has become critical to answer this pressing question. We developed a translational preclinical piglet model to study anesthesia-related neuroinflammation and identify safe pharmacologic regimens in pediatric anesthesia. The study of animals with lissencephalic brains, such as rodents, have contributed most basic research data on the effects of isoflurane on brain development. Very limited studies in large animals with gyrencephalic brains are reported. We present our piglet model, an alternative to larger, costly animals. We believe our model has the potential to be ideal for preclinical screening in this research.
Methods:
35 animals are studied. Animals are divided into three groups: 1) control, 2) LPS and 3) Isoflurane 2%. Untreated animals serve as controls. The positive control group receives E. coli endotoxin, lipopolysaccharide (LPS) intraperitoneally at a dose known to induce an acute phase response. For the experimental animals, sevoflurane 8% in 100% O2 via face cone is used to induce anesthesia followed by isoflurane 2% in 50% O2/50% air for 3 hours. An IV catheter is placed, the trachea intubated and lungs mechanically ventilated to ensure normocapnia and normoxia. A femoral artery catheter assures continuous blood pressure monitoring and allows for blood sampling. End-tidal carbon dioxide, rectal temperature, and arterial blood pressure are monitored continuously throughout the study. Arterial blood gases are measured hourly during anesthesia. At the end, vascular catheters are removed and the surgical incision is closed and infiltrated with bupivacaine. Piglets are awakened and the trachea extubated. Animals are returned to a temperature-controlled cage for 72h. They are monitored every hour for the first 6 hours and every 4 hours thereafter. Piglets receive a nutritionally complete commercial piglet milk replacer. After 72 hours the piglets receive 8% sevoflurane in 100% O2. Peripheral blood is collected via venipuncture and cerebrospinal fluid (CSF) is obtained via cisterna magna puncture. The CSF and blood are frozen and stored at -80oC within 30 min. A transaortic perfusion of heparinized phosphate buffered saline (PBS) and 4% paraformaldehyde (PFA) is given. Brains are harvested. Results: 35 animals have been studied thus far (12 isoflurane, 10 control, and 13 LPS). Our model reproduces exactly the surgical and anesthetic conditions children undergo in the operating room. A standard anesthesia machine is used (Figure 1). Vital signs and arterial blood gases are monitored to ensure physiologic homeostasis. Table 1 shows a summary of average vital signs and selected laboratory values for isoflurane animals studied.
Discussion:
A clinically relevant, translational piglet model recreating similar surgical and anesthesia conditions as in neonates and infants has been developed to study anesthesia-induced neurotoxicity. We can now safely and effectively use it to easily test a number of different conditions and anesthetic regimens in piglets. It is a viable, cost-effective, and clinically appropriate model for anesthetic neurotoxicity screening.