Mechanism of action of the erector spinae plane block: distribution of dye in a porcine model

This study aimed to describe the anatomical distribution of dye injected in the erector spinae plane (ESP) in a porcine living model, which could aid to reveal factors potentially relevant to the unexplained clinical effects of the ESP block. Six pigs received 0.6 mL/kg of 0.25% new methylene blue at the level of the sixth thoracic vertebra through either a cranial-to-caudal or a caudal-to-cranial in-plane ultrasound-guided bilateral ESP injection 20 min before euthanasia.Spread of dye evaluated through transverse cryosections (four injections) extended from T5 to T10 and from T5 to T8 when a cranial-to-caudal direction of injection was used, and from T5 to T9 and from T5 to T8 when the opposite direction of injection was used. A median of 4.5 medial and lateral branches of the dorsal rami was observed stained through anatomical dissection (eight injections), regardless of the direction of injection. No evidence of dye was found in the thoracic paravertebral or epidural spaces, where the dorsal root ganglia, ventral rami and rami communicantes are located. In all the cases, dye solution was found in the prevertebral thoracic lymph nodes.In this study, ESP injection resulted in a median spread over five spinal segments (12 injections), staining the lateral and medial branches of the dorsal rami of the spinal nerves, regardless of the direction of the needle used.

Efficacy of Miniuniportal Video-Assisted Thoracoscopic Selective Sympathectomy (Ramicotomy) for the Treatment of Severe Palmar and Axillar Hyperhidrosis

Background Video-assisted thoracoscopic surgery (VATS) clipping of the sympathetic branch has become the standard approach for the treatment of essential hyperhidrosis when conservative treatment failed. However, this is associated with relevant potential complications such as postoperative compensatory sweating and recurrent sweating. We report the outcome after selective sympathectomy (ramicotomy) through a miniuniportal VATS approach in patients with therapy-refractory palmar and/or axillary hyperhidrosis. Methods A total of 51 consecutive patients (37 females, mean age: 30 years, range: 12–64 years) who suffered from therapy-refractory palmar and/or axillary severe hyperhidrosis were included. Data were prospectively collected and retrospectively analyzed. All patients underwent bilateral miniuniportal VATS ramicotomy. Duration of surgery, hospital stay, recurrent, and compensatory sweating were documented. Results All patients had palmar sweating, where 51% had additional axillary sweating and 57% had additional plantar sweating. In all patients, selective division of the rami communicantes of the thoracic sympathetic ganglions Th2 to Th5 was performed. The mean duration of bilateral surgery for both sides was 67 ± 2.5 minutes. The mean postoperative hospital stay was 2 ± 1 days. After surgery and at further follow-up (mean: 12 ± 2.5 months), all patients presented dry and warm hands and axillae, without any evidence of compensatory or recurrent sweating. All patients described a remarkable increase in quality of life. Conclusion Miniuniportal VATS ramicotomy represents a feasible surgical technique with a very high success and satisfaction rate. Therefore, this approach should be considered as the method of choice for the treatment of patients with severe therapy-refractory palmar and axillary hyperhidrosis.

Bradykinin and thromboxane A2 reciprocally interact to synergistically stimulate cardiac spinal afferents during myocardial ischemia

Myocardial ischemia is a complex process leading to the simultaneous release of a number of mediators, including thromboxane A2 (TxA2) and bradykinin (BK), that activate cardiac spinal afferents. The present study tested the hypothesis that TxA2 and BK reciprocally interact to excite ischemically sensitive cardiac afferents. Nerve activity of single cardiac afferent units was recorded from the left sympathetic chain or rami communicantes (T2–T5) of anesthetized cats. Fifty-two ischemically sensitive afferents (conduction velocity = 0.27–3.35 m/s, 7 Aδ-fibers and 45 C-fibers) were identified. Repeated injections (1 μg) of BK into the left atrium (LA) 4 min after the administration of U-46619 (5 μg into the LA), a TxA2 mimetic, induced a significantly larger cardiac afferent response than the first response to BK (0.61 ± 0.14 to 1.95 ± 0.29 vs. 0.66 ± 0.09 to 2.75 ± 0.34 impulses/s, first injection vs. second injection, n = 8). Conversely, blockade of TxA2 receptors with BM-13,177 (30 mg/kg iv) attenuated the responses of eight other afferents to BK (1 μg into the LA) by 45%. In contrast, repeated BK (1 μg into the LA) induced consistent discharge activity in six separate afferents. We then observed that the coadministration of U-46619 (5 μg) and BK (1 μg into the LA) together caused a total response that was significantly higher than the predicted response by the simple addition of the individual responses. BK (1 μg) facilitated eight cardiac afferent responses to U-46619 (5 μg into the LA) by 64%. In contrast, repeated U-46619 (5 μg into the LA) without intervening BK stimulation evoked consistent responses in seven other ischemically sensitive afferents. Finally, inhibition of cyclooxygenase with indomethacin (5 mg/kg iv) eliminated the potentiating effects of BK on the cardiac afferent response to U-46619 (5 μg into the LA) but did not alter the afferent response to U-46619. These data suggest that BK and TxA2 reciprocally interact to stimulate ischemically sensitive cardiac afferent endings leading to synergistic afferent responses and that the BK sensitization effect is mediated by cyclooxygenase products.