Toxic dose: Unknown; it is likely that the slow bupivacaine release due to liposomal encapsulation results in lower systemic exposure and decreased incidence of adverse effects. Administration ( Grubb et al., 2020): For tissue infiltration, BLIS is injected into the surgery or wound site tissue during wound/incision closure (currently used for a multitude of wounds/incisions but is off-label except for closure of incision for stifle surgery) using a 25-gauge needle or larger since smaller-bore needles can disrupt the liposomes. Injection at closure prevents liposome disruption during surgical tissue manipulation.
For nerve blocks that are not at the incision site (currently used for a multitude of nerve blocks but is off label except for blockade of the radius/ulnar/musculocutaneous nerves), pre-emptive administration is possible since the liposomes at the remote location will not be disrupted during the surgical incision. Due to their relatively large size, the liposomes release bupivacaine locally rather than diffusing throughout the tissue, thus, BLIS is not likely to be highly effective for ‘splash’ (i.e., ‘squirting’ local anaesthetics into the incision or wound) blocks.
ADJUVANTS AND LOCAL ANESTHETICS
The adjuvant drugs of regional LAs improve the quality and duration of anesthesia and analgesia and patient safety, thus increasing patient satisfaction and comfort (Schäfer, 2019).In veterinary medicine, the most common adjuvants for perineural injection with local anaesthetic drugs are opioids and Alpha-2 agonists. Properties of an ideal adjuvant ● Shortens the time it takes for local anesthetics to start working ● Reduce the dosage of local anesthetic drugs ● Provides hemodynamic stability also be given and include intravenous fluid therapy, oxygen administration, anticonvulsants for seizures, mechanical ventilation, and appropriate cardiovascular support. Advanced life support measures may be required in severe cases. Prevention: ● Dosage selection ● Aspiration before injection ● Use local anesthetics with lower systemic toxicity profiles when possible ● Use slow, incremental injections with aspiration to minimize the risk of intravascular injection B. Administration complications Potential complications of LNBs: ● Hematoma formation ● Accidental IV administration of local blocks ● Nerve blockade failure ● Other types of tissue injury at the site of administration C. Nerve damage associated with LNBs Damage ranges from transient neuropraxia (temporary loss of nerve function) to permanent nerve injury. This can manifest as weakness, paralysis, or paresthesia in the affected area. Prevention: ● Anatomical knowledge is crucial for accurate needle placement and minimizing the risk of nerve injury. ● Use appropriate needle size and gauge to minimize tissue trauma. ● Promotes optimal sedation ● Minimum adverse effects ● If applicable, use a nerve stimulator to confirm nerve proximity and avoid direct nerve contact during needle placement. ● Always aspirate before injection to avoid intraneural injection. ● Administer the recommended dosage to minimize the risk of neurotoxicity.
Local anesthetic use can be limited by their duration of action and the dose-dependent adverse effects on the cardiac and central nervous system. Adjuvants are drugs which, when co-administered along with local anesthetic agents, improve the latency of onset and duration of analgesia and counteract disadvantageous effects of local anesthetics. The use of adjuvant drugs has the potential to improve the efficacy of peripheral and central neuraxial blocks and decrease LA systemic toxicity by chiefly prolonging the duration of sensory block, enhancing motor blockade, and limiting the overall dose requirement of LAs (Mehta et al., 2020). Common complications associated with LNBs A. Local Anesthetic Toxicity (LAST) Central nervous system and cardiovascular disturbances are the most common adverse effects associated with local anesthetic systemic toxicity (LAST). Central nervous system signs usually appear first and include sedation, muscle tremors, and/or seizures (Hoon et al., 2023). CNS signs are further exacerbated by acidosis seen secondarily to seizure-induced hypoventilation following toxicity (Caulfield et al., 2022). Cardiovascular effects include bradyarrhythmia and reduced myocardial contractility. These effects are brought about by direct blockade of myocardial sodium channels (Hoon et al., 2023). Myocardial contractility reduction causes cardiovascular depression, secondary to bradycardia, hypotension and arrhythmias; in cases of severe contractility reduction, this leads to cardiac arrest (Grubb et al., 2020). Potential causes of local anesthetic systemic toxicity (LAST): ● Inadvertent IV injection ● Rapid intravenous administration ● Rapid systemic absorption ● Absolute overdosing ● Hypersensitivity reactions Local anesthetic agents with: ● Low toxicity risks : lidocaine, prilocaine, mepivacaine Cats are reportedly more susceptible to LAST, which is speculated to be due to reduced hepatic metabolism and the reduced accuracy of drug for weight calculations (Caulfield et al., 2022). Local anesthetic toxicity can be treated with the use of intravenous lipid emulsion (ILE), particularly intralipid 20% emulsion (Caulfield et al., 2022). Supportive therapy should ● Medium toxicity risks : ropivacaine ● High toxicity risks : bupivacaine
EliteLearning.com/Veterinarian
Book Code: VFL1526
Page 32
Powered by FlippingBook