Background: Cardiac sympathetic blockade is a therapeutic approach for arrhythmias and heart failure and may be a beneficial effect of high thoracic epidural anesthesia. These treatments require detailed knowledge of the spatial location and distribution of cardiac autonomic nerves, however, there are controversies on this subject in humans. Objective: To provide a systematic overview of current knowledge on human anatomy of the cardiac autonomic nervous system. Results: In contrast to the often claimed assumption that human preganglionic sympathetic cardiac neurons originate mainly from thoracic spinal segments T1-T4 or T5, there is ample evidence indicating involvement of cervical spinal segment C8 and thoracic spinal segments below T5. Whether cervical ganglia besides the stellate ganglion play a role in transmission of cardiac sympathetic signals is unclear. Similarly, there is debate on the origin of cardiac nerves from different thoracic ganglia. Most human studies report thoracic cardiac nerves emerging from the first to fourth thoracic paravertebral ganglia; others report contributions from the fifth, sixth and even the seventh thoracic ganglia. There is no agreement on the precise composition of nerve plexuses at the cardiac level. After years of debate, it is generally accepted that the vagal nerve contributes to ventricular innervation. Vagal distribution appears higher in atria, whereas adrenergic fibers exceed the number of vagal fibers in the ventricles. Conclusion: Anatomy of the human cardiac autonomic nervous system is highly variable and likely extends beyond generally assumed boundaries. This information is relevant for thoracic epidural anesthesia and procedures targeting neuronal modulation of cardiac sympathetic innervation.

Meta-analysis, Level II.

The analgesic effect of local infiltration analgesia (LIA) after total knee arthroplasty (TKA) has been reported to be less than 24 hours. The concept of continuous LIA (CLIA) has been developed to achieve prolonged analgesia by bolus injections or by pump infusion of analgesics. The purpose of this meta-analysis is to assess the effect of CLIA versus single-shot injection LIA (SLIA) and placebo on pain after TKA.A systematic search was performed in most relevant databases to identify all randomized controlled trials (RCTs) comparing intra-articular CLIA with SLIA or placebo for TKA. Primary outcome measures were visual analogue scale (VAS)-scores after 24, 48, and 72 hours at rest and during activity. Data were extracted for meta-analysis and pooled using Cochrane software. The results of comparable studies were pooled using the fixed effects model or random effects model.A total of 11 RCTs were included. Five articles were eligible for meta-analysis comparing CLIA versus placebo, involving 227 TKAs. VAS scores at rest 24 hours after surgery were in favor of CLIA with a decrease of pain scores of 46%. On the second and third postoperative day, the decrease in VAS scores was no longer significant. During activity VAS scores were also in favor of CLIA after 24 and 48 hours.Two studies were eligible for meta-analysis comparing CLIA versus SLIA. VAS scores at rest, 48 hours after surgery, were in favor of CLIA. CLIA can possibly provide a reduced pain perception for 24 hours postoperative at rest after performing a TKA. This effect may persist until 48 hours postoperative during activity. Due to the high level of heterogeneity no firm further conclusions can be drawn.