Risk factors for post-induction hypotension in children presenting for surgery.

BACKGROUND: Preoperative factors have been correlated with pre-incision hypotension (PIH) in children undergoing surgery, suggesting that PIH can be predicted through preoperative screening. We studied blood pressure (BP) changes in the 12 min following the induction of anesthesia to study the incidence of post-induction hypotension and to assess the feasibility of predicting PIH in low-risk children without preoperative hypotension or comorbid features. METHODS: We retrospectively evaluated 200 patients ranging in age from 2 to 8 years with American Society of Anesthesiologists' (ASA) physical status I or II, undergoing non-cardiac surgery. Patients were excluded if they had preoperative (baseline) hypotension (systolic blood pressure (SBP) < 5th percentile for age). BP and heart rate (HR) were recorded at 3 min intervals for 12 min after the induction of anesthesia. Pre-incision hypotension (PIH) was initially defined as SBP < 5th percentile for age: (1) at any timepoint within 12 min of induction; (2) for the median SBP obtained during the 12 min study period; or (3) at 2 or more timepoints including the final point at 12 min after the induction of anesthesia (sustained hypotension). In addition, we examined PIH defined as > 20% decrease in SBP from baseline: (4) at any timepoint within 12 min of the induction of anesthesia; (5) for the median SBP obtained during the 12 min study period; or (6) at two or more timepoints including the final point at 12 min after the induction of anesthesia. Agreement among the six definitions was analyzed, in addition to the effects of age, gender, type of anesthetic induction, use of premedication, preoperative BP, preoperative HR, and body mass index on the incidence of PIH according to each definition. RESULTS: Five patients were excluded due to baseline hypotension and six were excluded for missing data. In the remaining cohort, estimated PIH prevalence ranged from 4% [definition (Stewart et al., in Paediatr Anaesth 26:844-851, 2016), sustained PIH according to SBP percentile-for-age] to 57% [definition (Task Force on Blood Pressure Control in Children, in Pediatrics 79:1-25, 1987), at least one timepoint where SBP was > 20% lower than baseline]. Pairwise agreement among the six definitions ranged from 49 to 91% agreement. No sequelae of PIH were noted during subsequent anesthetic or postoperative care. On multivariable analysis, no covariates were consistently associated with PIH risk across all six definitions of PIH. CONCLUSION: The present study describes the incidence and prediction of PIH in a cohort of relatively healthy children. In this setting, accurate prediction of PIH appears to be hampered by lack of agreement between definitions of PIH. Overall, there was a low PIH incidence when the threshold of SBP < 5th percentile for age was used. LEVEL OF EVIDENCE: II.

Dura to spinal cord distance at different vertebral levels in children and its implications on epidural analgesia: A retrospective MRI-based study.

BACKGROUND: The distance from the dura to spinal cord is not uniform at different vertebral levels. The dura to spinal cord distance may be a critical factor in avoiding the potential for neurological injury caused by needle trauma after a dural puncture. Typically, the greater the dura to spinal cord distance, the larger the potential safety margin. The objective of our study is to measure dura to spinal cord distance at two thoracic levels T6 -7 , T9 -10 , and one lumbar level L1 -2 using MRI images. METHODS: Eighty-eight children under the age of 8 years old qualified for the study. The distance from dural side of ligamentum flavum to the posterior margin of the spinal cord was defined as dura to spinal cord distance. Sagittal T2 -weighted images of the thoracic and lumbar spine were used to measure the dura to spinal cord distance at the T6-7 , T9-10 , and L1-2 interspaces. Measurements were taken perpendicular to long axis of the vertebral body at each level. RESULTS: The dura to spinal cord distance was 5.9 ± 1.6 mm at T6-7 (range: 1.4-9.9 mm), 5.0 ± 1.6 mm at T9-10 (1.2-8.1 mm), and 3.6 ± 1.2 mm at L1-2 (1.2-6.8 mm). There were no evident differences in dura to spinal cord distance by gender, age, height, or weight. CONCLUSION: The present study reports that the largest dura to spinal cord distance is found at the T5-6 level, and the shortest dura to spinal cord distance at the L1-2 level. There appears to be substantially more room in the dorsal subarachnoid space at the thoracic level. The risk of spinal cord damage resulting from accidental epidural needle advancement may be greater in the lumbar region due to a more dorsal location of the spinal cord in the vertebral canal compared to the thoracic region.