There are no published reports of fatalities as a consequence of IVRA or intravenous regional limb perfusion in horses, which indicates that it is probably a very safe technique. A mild and transient decrease in blood pressure is usually observed in the experience of the author after the release of a tourniquet in horses under general anesthesia.
Prevention
The absolute safe limit of tourniquet duration has not been established and may depend on location and vary from animal to animal. The usual clinical recommendation is to limit the time of tourniquet to 2 hours, although in the author’s clinical experience this time has sometimes been exceeded with no negative consequences. In experimental rhesus monkeys, the systemic changes produced as a result of the application of a tourniquet for periods of up to 3 hours were not marked and readily reversible, and the local acid–base changes in the ischemic limb recovered in less than 40 min post‐release [111]. However, it should be noted that these were healthy animals, and shorter tourniquet times are recommended in debilitated animals.
It is recommended to use a staggered tourniquet release, which will both avoid a sudden release of local anesthetic into the systemic circulation and will reduce the cardiovascular consequences of limb reperfusion.
Diagnosis
The clinical manifestations of tourniquet release may include hypotension, brady‐ or tachy‐cardia, arrhyhtmias, tachypnea, and in extreme cases cardiovascular collapse or cardiac arrest. Close monitoring of the cardiovascular system is therefore recommended during and at least 30–40 min following tourniquet release.
Treatment
In healthy animals and when the cardiovascular changes are mild, no treatment is necessary. In cases of severe hypotension or cardiovascular collapse, supportive treatment with intravenous fluids, positive inotropic drugs (e.g. dobutamine) and/or vasoconstrictors (e.g. phenylephrine) may be necessary. Also, a venous blood sample should be obtained to check acid–base balance and serum electrolytes, and treat derangements (e.g. hyperkalemia, hypercalcemia) as necessary.
Expected outcome
The outcome is good if the cardiovascular effects are mild, but it could be fatal if cardiovascular collapse or cardiac arrest occur.
References
1 1 Tanner, R.B. and Hubbell, J.A.E. (2019). A retrospective study of the incidence and management of complications associated with regional nerve blocks in equine dental patients. J. Vet. Dent. 36 (1): 40–45.
2 2 Loughran, C.M., Raisis, A.L., Haitjema G. et al. (2016). Unilateral retrobulbar hematoma following maxillary nerve block in a dog. J. Vet. Emerg. Crit. Care (San Antonio). 26 (6): 815–818.
3 3 Tanaka, K., Watanabe, R.Y., Harada T. et al. (1993). Extensive application of epidural anesthesia and analgesia in a university hospital: incidence of complications related to technique. Reg. Anesth. 18 (1): 34–38.
4 4 Rainger, J., Baxter, C., Vogelnest, L. et al. (2009). Seizures during medetomindine sedation and local anaesthesia in two dogs undergoing skin biopsy. Aust. Vet. J. 87 (5): 188–192.
5 5 Aprea, F., Vettorato, E., and Corletto. F. (2011). Severe cardiovascular depression in a cat following a mandibular nerve block with bupivacaine. Vet. Anaesth. Analg. 38 (6): 614–618.
6 6 Liu, S.S., Ortolan, S., Sandoval, M.V. et al. (2016). Cardiac arrest and seizures caused by local anesthetic systemic toxicity after peripheral nerve blocks: should we still fear the reaper? Reg. Anesth. Pain Med. 41 (1): 5–21.
7 7 O’Neill, H.D., Garcia‐Pereira, F.L., and Mohankumar, P.S. (2014). Ultrasound‐guided injection of the maxillary nerve in the horse. Equine Vet. J. 46 (2): 180–184.
8 8 Lewis, S.R., Price, A., Walker, K.J. et al. (2015). Ultrasound guidance for upper and lower limb blocks. Cochrane Database Syst Rev. September 11; (9): CD006459.
9 9 Meyer, G.A., Lin, H.C., Hanson, R.R. et al. Effects of intravenous lidocaine overdose on cardiac electrical activity and blood pressure in the horse. Equine Vet. J. 33 (5): 434–437.
10 10 Copeland, S.E., Ladd, L.A., Gu, S.Q. et al. (2008). The effects of general anesthesia on the central nervous and cardiovascular system toxicity of local anesthetics. Anesth. Analg. 106: 1429–1439.
11 11 Feldman, H.S., Arthur, G.R., Pitkanen, M. et al. (1991). Treatment of acute systemic toxicity after the rapid intravenous injection of ropivacaine and bupivacaine in the conscious dog. Anesth. Analg. 73 (4): 373–384.
12 12 Weinberg, G.L., VadeBoncouer, T., Ramaraju, G.A. et al. (1998). Pretreatment or resuscitation with a lipid infusion shifts the dose‐response to bupivacaine‐induced asystole in rats. Anesthesiology. 88: 1071–1075.
13 13 Weinberg, G., Ripper, R., Feinstein, D.L. et al. (2003). Lipid emulsion infusion rescues dogs from bupivacaine‐induced cardiac toxicity. Reg. Anesth. Pain Med. 28: 198–202.
14 14 Corman, S.L. and Skledar, S.J. (2007). Use of lipid emulsion to reverse local anesthetic‐induced toxicity. Ann. Pharmacother. 41 (11): 1873–1877.
15 15 Bern, S., Akpa, B.S., Kuo, I. et al. (2011). Lipid resuscitation: a life‐saving antidote for local anesthetic toxicity. Curr. Pharm. Biotechnol. 12 (2): 313–319.
16 16 Woolley, E.J. and Vandam. L.D. (1959). Neurological sequelae of brachial plexus nerve block. Ann. Surg. 149: 53–60.
17 17 Hogan, Q.H. (2008). Pathophysiology of peripheral nerve injury during regional anesthesia. Reg. Anesth. Pain Med. 33 (5): 435–441.
18 18 Selander, D., Brattsand, R., Lundborg, G. et al. (1979). Local anesthetics: Importance of mode of application, concentration and adrenaline for the appearance of nerve lesions. Acta Anaesth. Scand. 23: 127–136.
19 19 Gentili, F., Hudson, A.R., Hunter, D. et al. (1980). Nerve injection injury with local anesthetic agents: a light and electron microscopic, fluorescent microscopic, and horseradish peroxidase study. Neurosurgery. 6: 263–272.
20 20 Lofstrom, B., Wennberg, A., and Widen. L. (1966). Late disturbances in nerve function after block with local anaesthetic agents. Acta Anaesth. Scand. 10 (2): 111–122.
21 21 Hadzic, A., Dilberovic, F., Shah, S. et al. (2004). Combination of intraneural injection and high injection pressure leads to fascicular injury and neurologic deficits in dogs. Reg. Anesth. Pain Med. 29 (5): 417–423.
22 22 Kapur, E., Vuckovic, I., Dilberovic, F. et al. (2007). Neurologic and histologic outcome after intraneural injections of lidocaine in canine sciatic nerves. Acta Anaesth. Scand. 51 (1): 101–107.
23 23 Selander, D., Dhunér, K.G., and Lundborg, G. (1977). Peripheral nerve injury due to injection needles used for regional anesthesia. Acta Anaesth. Scand. 21 (3): 18–188.
24 24 Nitz, A.J. and Matulionis, D.H. (1982). Ultrastructural changes in rat peripheral nerve following pneumatic tourniquet compression. J. Neurosurg. 57: 660–666.
25 25 Tountas, C.P. and Bergman, R.A. (1977). Tourniquet ischemia: ultrastructural and histochemical observations of ischemic human muscle and of monkey muscle and nerve. J. Hand Surg. 2: 31–37.
26 26 Auroy, Y., Benhamou, D., Bargues, L. et al. (2002). Major complications of regional anesthesia in France. The SOS Regional Anesthesia Hotline Service. Anesthesiology: J. Am. Soc. Anesth. 9 (5): 1274–1280.
27 27 Fredrickson, M.J. and Kilfoyle, D.H. (2009). Neurological complication analysis of 1000 ultrasound guided peripheral nerve blocks for elective orthopaedic surgery: a prospective study.