Regional Anesthesia. Fatiş Altındaş Dept. of Anesthesiology

Transcription

1 Regional Anesthesia Fatiş Altındaş Dept. of Anesthesiology

2 Regional anesthesia - Definition Renders a specific area of the body, e.g. foot, arm, lower extremities insensating to stimulus of surgery or other instrumentation Eliminates sensation in a limited region of the body Interferes with impulse transmission in peripheral or spinal cord nerves There is no loss of consciousness

3 Benefits of Regional Anesthesia Provide anesthesia for a surgical procedure Unsurpassed quality of analgesia post- operatively or during labor and delivery Reduction in stress response Improves regional blood flow Diagnosis or therapy for patients with chronic pain syndromes

4 Regional anesthesia - types Central neuraxial blockade Epidural Spinal Peripheral nerve block minor: single nerve major: multiple nerves or plexus Infiltration Topical skin mucous membranes

5 Central Blocks: Spinal, Epidural These blocks are also known neuroaxial anesthesia Performing as a single injection or with a catheter to allow intermittent boluses or continuous infusion

6 The principal site of action for central blocks is the nerve roots Injecting local anesthetic into CSF or the epidural space

7 Anatomy of the vertebral column Spinal cord and its nerve roots lie within the vertebral column Spinal cord extends from the foramen magnum to level of L1 in adults and L3 in children

8 Spinal cord Spinal cord is covered by meninges Pia mater Arachnoid mater Dura mater

9 CSF is contained between the pia and arachnoid mater in the subarachnoid space

10 Indications: Uses Central blocks may be used for nearly any procedure below the neck As a primary anesthetic technique Lower abdominal, inguinal Urogenital, rectal Lower extremity surgery

11 Indications-cont. The choice of anesthesia is determined by the patients Discussing risks and benefits Obtaining informed consent Suitability of the technique for the type of surgery The surgeon s preference The experience of the anesthetist Physiologic and mental state

12 Contraindications Absolute Infection at the site of injection Patient refusal Coagulopathy or bleeding diathesis Severe hypovolemia Increased ICP Severe aortic stenosis Severe mitral stenosis Relative Sepsis Uncooperative patient Preexisting neurologic deficits Demyelinating lesions Severe spinal deformity

13 Technical considerations They should only be performed in facility where all the equipment and drugs needed for intubation and resuscitation are immediately available Monitoring for surgical anesthesia is the same as for general anesthesia Blood pressure, heart rate, pulse oximetry

14 Central Blocks- Spinal Advantages Technically easy (LP technique) High success rate, rapid onset Disadvantages high spinal hypotension due to sympathetic block post dural puncture headache

15 Central Blocks- Epidural Performing at the cervical, thoracic, lumbar or sacral levels. Widely used for surgical anesthesia, obstetric analgesia, postoperative pain control and chronic pain management

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17 Epidural anesthesia is slower in onset (10-20 minutes) It is not as intense as spinal anesthesia

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21 Effects of central blocks Sempathetic blockade Vasodilation Hypotension Sensory blockade Interrupts both somatic and visceral painful stimuli Motor blockade

22 Advantages of central blocks Morbidity and mortality may be reduced by neuroaxial blockade Incidence of venous thrombosis Pulmonary embolism Cardiac complications in high risk patients Bleeding and transfusion requirements Pneumonia and respiratory depression

23 Complications of neuroaxial blocks Range from bothersome to crippling and life-threatining Result from medication introduced or the needle used to perform the procedure

24 Complications-cont. Needle Backache Headache Nerve injury Vascular injury Infection Medication=LA High blokade Systemic toxicity Local toxicity Infection

25 Plexus Blockade Injection of local anesthetic adjacent to a plexus, e.g cervical, brachial or lumbar plexus Uses: surgical anesthesia or post-operative operative analgesia in the distribution of the plexus Procedures on the arm, shoulder, trunk or legs Advantages: large area of anesthesia with relatively small dose of agent Disadvantages: - technically complex, potential for toxicity and neuropathy

26 Brachial plexus C5 through C8 and T1 Anesthesia of the shoulder and upper extremity

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28 Topical Anesthesia Application of local anesthetic to mucous membrane - cornea, nasal/oral mucosa Uses : - awake oral or nasal intubation, superficial surgical procedure Advantages : technically easy minimal equipment Disadvantages : potential for large doses leading to toxicity

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30 Local/Field Anesthesia =Infiltration Application of local subcutaneously to anesthetize distal nerve endings Uses: - Suturing, minor superficial surgery, line placement, more extensive surgery with sedation Advantages: - minimal equipment, technically easy, rapid onset Disadvantages: - potential for toxicity if large field

31 Bier Block Injection of local anesthetic intravenously for anesthesia of an extremity Uses - any surgical procedure on an extremity Advantages: - technically simple,, minimal equipment, rapid onset Disadvantages: - duration limited by tolerance of tourniquet pain, toxicity

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33 Peripheral nerve block Injecting local anesthetic near the course of a named nerve Uses: - Surgical procedures in the distribution of the blocked nerve Advantages: - relatively small dose of local anesthetic to cover large area; rapid onset Disadvantages: - technical complexity, neuropathy

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36 Local Anesthetics - Definition A substance which reversibly inhibits nerve conduction when applied directly to tissues at non- toxic concentrations

37 Local Anesthetics Mechanism of action is by reversibly blocking sodium channels to prevent depolarization Anesthetic enters on axioplasmic side and attaches to receptor in middle of channel

38 Local Anesthetics Linear molecules that have a lipophilic and hydrophilic end (ionizable) low ph-- more in ionized state and unable to cross membrane adding sodium bicarb-- more in non-ionized state

39 Local Anesthetics Two groups: esters and amides esters metabolized by plasma cholinesterase amides metabolized by cytochrome p-450

40 Local anesthetics - Classes Esters Cocaine Chloroprocaine Procaine Tetracaine Amides Bupivacaine vacaine Lidocainedocaine Ropivacaine vacaine Etidocaine docaine Mepivacaine

41 Local anesthetics - Duration Determined by rate of elimination of agent from site injected Factors include lipid solubility, dose given, blood flow at site, addition of vasoconstrictors (does not reliably prolong all agents) Some techniques allow multiple injections over time to increase duration,, e.g. epidural catheter

42 Precautions Epinephrine combinations should not be used where circulation may be compromised by vasoconstriction fingers toes ears nose penis

43 Local Anesthetics - Allergy True allergy is very rare Most reactions are resulted from ester class Ester hydrolysis (normal metabolism) leads to formation of PABA

44 Local Anesthetics Toxicity Tissue toxicity Rare Occurs if administered in high enough concentrations (greater than those used clinically) Usually related to preservatives added to solution

45 Systemic toxicity Related to blood level of drug Absolute overdose Accidentally intravascular injection All LA produce a similar picture of toxicity Degree of disturbances caused by toxicity Potency of drugs: lipid solubility Pharmacokinetics properties The rate of rise of plasma levels The peak level The fraction of unbound drug in the circulation

46 Toxic effects Lignocaine plasma conc. (mcg/ml) CVS depression Respiratory arrest Coma=CNS collaps Convulsions Unconciousness Muscular twitching Tinnitus Visual disturbance Ligthheadedness Numbness of tongue + Metallic taste

47 Prevention and Treatment of Toxicity Primarily from intravascular injection or excessive dose -- anticipation aspirate often with slow injection ask about CNS toxicity have monitoring available prepare with resuscitative equipment, CNSdepressant drugs, cardiovascular drugs ABC s

48 Treatment of Toxicity

49 Hoping without disability