Abstract

NM-325

Unexpected increases in blood pressure and heart rate with the sound of the drill in a 10-month-old undergoing cranial vault remodeling using non-neurotoxic anesthetics

¹Thurman M, ²Khan U, ¹Alex G
¹UT Southwestern Medical Center/Children's Medical Center, Dallas, Texas, United states; ²Children's Health, Dallas, Texas, United states

A 10-month-old, 9 kg boy presented for an open posterior vault remodeling due to sagittal synostosis. The patient was induced with sevoflurane, intravenous lines started and intubated without complication. The patient was paralyzed and turned prone. The sevoflurane was turned off, and remifentanil (REM) and dexmedetomidine (DEX) infusions were started at rates of 0.3mcg/kg/min and 0.3mcg/kg/hr, respectively.
45 minutes into the case, as the neurosurgeon used the craniotome to make cuts into the skull, the patient’s blood pressure (BP) and heart rate (HR) increased significantly. The HR reached a maximum rate of 192 bpm, and the BP a level of 115/64mmHg (MAP of 81mmHg) following its use. The REM and DEX infusion rates were increased to 0.5mcg/kg/min and 0.5mcg/kg/hr, respectively, with temporary resolution of the hypertension and tachycardia. This phenomenon occurred again several times, correlated with the sound of the craniotome and resolving when the craniotome was turned off [see figure]. After this phase, there were no noted significant increases in BP or HR to the degree which was seen when the craniotome was used. At the end of the case the patient was awaken, extubated and given 0.01mcg/kg of hydromorphone.

We chose to use a neuroprotective technique to anesthetize this patient due to the FDA’s recent safety warning against volatile agents in developing brains [1]. Narcotics [2] and DEX [3] are agents that have been identified as safe to use in this patient population. DEX, an alpha2-adrenoreceptor agonist, is used clinically for analgesia, anxiolysis, sedation, sympatholysis, as well as anesthetic-sparing and hemodynamic-stabilizing effects [4]. DEX has been found to provide significant neuroprotection in previous preclinical studies by exerting its effects via upregulation of the alpha2-adrenoreceptor and favorably modulating the ratio of pro-apoptotic to anti-apoptotic proteins [3].

One critical objective of modern anesthesia administration is to ensure adequate depth of anesthesia to prevent awareness. In the case presented, effort was made on the anesthesiologist’s part to utilize a neurotoxic-free anesthetic, but at the expense of a phenomenon that manifested as potential inadequate depth of anesthesia. While anesthesiologists take into account such factors as patient age, level of surgical stimulation, and the use of analgesic agents in efforts to titrate anesthetic agents, one factor not measured is the auditory stimulus, which represents a major component of consciousness and memory formation [5]. Brainstem auditory potentials are notoriously resistant to the effects of anesthesia and can be used for intraoperative neuromonitoring despite complete anesthesia.

References
1. U.S. FDA. 2016. https://www.fda.gov/downloads/Drugs/DrugSafety/UCM533197.pdf.
2. Ann N Y Acad Sci. 2010;1199:43-51.
3. Neurotoxicol Teratol. 2017;60:102-116.
4. Anesthesiology. 2000;93(5):1345-1349.
5. Med Hypotheses. 2013;80(5):568-572.