Sensory Assessment and Block Duration of Deep Parasternal Intercostal Plane Block in Patients Undergoing Cardiac Surgery: A Prospective Observational Study

INTRODUCTION: There has been increasing interest in using deep parasternal intercostal plane (PIP) block as a supplement to multimodal analgesia regimens in cardiac surgery. The aim of this study was to observe cutaneous sensory block distribution and its duration for deep PIP blocks in patients undergoing open cardiac surgery. METHODS: This observational, prospective clinical study consisted of 113 participants. All patients received bilateral ultrasound-guided deep PIP block with 40 ml 0.33% ropivacaine. The primary study outcome was cutaneous sensory block distribution of deep PIP blocks in patients undergoing open cardiac surgery. Secondary outcome included block duration in all participants. The area of cutaneous sensory block was tested by using a cold stimulus (ice cube) 30 min after the end of deep PIP block administration. Cutaneous sensory testing was performed once every hour after extubation until the return of normal sensation. RESULTS: Thirty minutes after bilateral deep PIP block administration, the successful block rate of dermatomes T4 to T6 was almost 100%. However, T2 (percentage of left T2 block: 64.6%; percentage of right T2 block: 42.5%) and T3 (percentage of left T3 block: 88.5%; percentage of right T3 block: 87.6%) had a lower percentage of success. A few patients had blocked dermatomes at T1 or T7 (percentage of left T1 block: 7.08%; percentage of right T1 block: 2.65%; percentage of left T7 block: 6.19%; percentage of right T7 block: 10.6%). The mean effective duration of the deep PIP block was 17 h. CONCLUSION: Bilateral deep PIP blocks can produce a widespread cutaneous sensory blockade with variable dermatomal distribution in the mid-sternum for a considerable effective duration. TRIAL REGISTRATION: This study was registered in the Chinese Clinical Trial Registry (ChiCTR2100047755).