The effects of simulated Bier block IVRA on intracompartmental tissue pressure

The role of peripheral venous distension reflex in regulating hemodynamics: mini review

Significant volume is pooled in veins in humans and the amount is dramatically altered by various physiological stresses and diseases. Several animal and human studies demonstrated that limb venous distension evoked significant increases in blood pressure and sympathetic nerve activity (venous distension reflex, VDR). VDR has attracted much attention because of its potential to explain the still unknown mechanism of autonomic dysfunction in several diseases, which would lead to a new treatment approach. This mini review discusses accumulated evidence of VDR at this point and what should be investigated in the future to apply the current understanding of VDR in clinical practice.

Sympathetic responses during saline infusion into the veins of an occluded limb

Animal studies have shown that the increased intravenous pressure stimulates the group III and IV muscle afferent fibres, and in turn induce cardiovascular responses. However, this pathway of autonomic regulation has not been examined in humans. The aim of this study was to examine the hypothesis that infusion of saline into the venous circulation of an arterially occluded vascular bed evokes sympathetic activation in healthy individuals. Blood pressure, heart rate, and muscle sympathetic nerve activity (MSNA) responses were assessed in 19 young healthy subjects during local infusion of 40 ml saline into a forearm vein in the circulatory arrested condition. From baseline (11.8 +/- 1.2 bursts min(-1)), MSNA increased significantly during the saline infusion (22.5 +/- 2.6 bursts min(-1), P < 0.001). Blood pressure also increased significantly during the saline infusion. Three control trials were performed during separate visits. The results from the control trial show that the observed MSNA and blood pressure responses were not due to muscle ischaemia. The present data show that saline infusion into the venous circulation of an arterially occluded vascular bed induces sympathetic activation and an increase in blood pressure. We speculate that the infusion under such conditions stimulates the afferent endings near the vessels, and evokes the sympathetic activation.

Compartment syndrome following intravenous regional anesthesia

PURPOSE

To present two cases of upper extremity compartment syndrome following intravenous regional anesthesia.

CLINICAL FEATURES

Case 1: A 57-yr-old man presented for surgical release of a left-hand Dupuytren's contracture. The procedure was performed under iv regional anesthesia with 360 mg lidocaine and sedation with 150 microg fentanyl and 1.5 mg midazolam. Tourniquet time was 107 min at a pressure of 260 mmHg using three different tourniquet sites. Within minutes of tourniquet release, increased forearm muscle tension, hand anesthesia, pallor, and limited motor function developed. Serum CK and myoglobin levels rose. Myoglobinuria was present. Several fasciotomies and aggressive fluid therapy were performed. Patient made almost full recovery. Case 2: A 73-yr-old woman with controlled hypertension had Dupuytren fasciotomy of her right hand under iv regional anesthesia with 200 mg lidocaine and sedation using 75 microg fentanyl and 1.5 mg midazolam. Tourniquet time was 64 min at a pressure of 250 mmHg using three different tourniquet sites. The patient complained of pain at the iv site during injection of local anesthetic, third tourniquet inflation and after deflation of tourniquet. Thirty minutes after arrival in PACU, her fingers were bluish. She complained of pain and swelling of the forearm. Under general anesthesia, fasciectomy was performed. Myoglobin and CPK levels rose. CPK MB was high but troponin was negative. Three days later she developed pulmonary embolism. She was heparinized and subsequently discharged home. She recovered completely.

CONCLUSION

Compartment syndrome may have a rapid and severe onset. Etiology of our cases is still not established. We postulate that increased tissue pressure may be the cause. The anesthesiologists must be aware of compartment syndrome during regional anesthesia.

[Locoregional intravenous anesthesia]

OBJECTIVE

To analyse current data on intravenous regional anaesthesia (IVRA), its benefits and drawbacks.

DATA SOURCES

Articles were obtained from a Medline search using the following search terms: 'intravenous regional anaesthesia', alone or combined with 'local anaesthetic agents', 'toxicity'.

STUDY SELECTION

Following articles in English and in French have been selected: main articles, original articles, update and review articles, letters to the editor and recent editorials.

DATA EXTRACTION

Physiopathological and pharmacological data were extracted for involved mechanisms and means for improving this technique.

DATA SYNTHESIS

IVRA is a reliable and efficient technique with a lower cost than general anaesthesia and well adapted for limb surgery in the ambulatory patient. Depending on the site of the surgical field, the pneumatic tourniquet is set either on the arm, forearm or wrist for the upper limb or thigh, calf or ankle for the lower limb. When set in periphery, less local anaesthetic agent is required. A wide tourniquet requires a lower inflation pressure than a double cuff tourniquet. A single cuff is as efficient as a dual cuff if shape, size and inflating pressure are appropriate. The limb occlusion pressure (LOP) is the minimal pressure required to occlude blood flow. It is assessed with either a pulse oximeter or Doppler for determination of the lowest cuff inflating pressure. The cuff is inflated to 50 mmHg above LOP. Oozing in the surgical field can be decreased by the re-exsanguination technique. Currently, lidocaine is the only local anaesthetic released in France for IVRA. Addition of a muscle relaxant, a NSAID or clonidine allows the dose of local anaesthetic agent to be decreased and improves postoperative analgesia.