Clinical Anaesthesiology

Qiu Wei FanAssociate professor

Department of AnaesthesiologyRui Jin Hospital

Shanghai Second Medical University

Local Anaesthetic techniques

Features of local anaesthesia Methods of local anaesthesia Complications of local

anaesthesia Regional block equipment Spinal, epidural, & caudal blocks Peripheral nerve blocks

Preoperative assessment and premedication Purpose

Establish rapport with the patient Obtain a history and perform a

physical examinations Order a special investigations Assess the risks of anaesthesia and

surgery and if necessary postpone or cancel the date of surgery

Instutite preoperative management Prescribe premedication and the

anaesthesia management

Preoperative assessment

and premedication

Routine preoperative anaesthetic evaluation

History Current problem Other known problems Medication history

Preoperative assessment and premedication Medication history

Allergies

Drug

intolerances

Present

therapy Prescription

Nonprescription

Nontherapeutic Alcohol

Tobacco

Illicit

Preoperative assessment and premedication

Previous anaesthetics, surgery, and obstetric deliverries

Family history Review of organ systems Last oral intake

Preoperative assessment and premedication Review of organ systems

General Respiratory Cardiovascular Renal Gastrointestinal Hematologic

Preoperative assessment and premedication Review of organ systems

Neurologic Endocrine Psychiatric Orthopedic Dermatologic

Preoperative assessment and premedication Physical examination

Vital signs Airway Heart Lungs Extremities Neurologic examination

Preoperative assessment and premedicationLaboratory evaluation Hematocrit or hemoglobin

concentrationAll menstruating womenAll patients over 60 years of ageAll patients who are likely to experience significant blood loss and may require transfusion

Serum glucose and creatinine (or blood urea nitrogen) concentration: all patients over 60 years of age

Electrocardiogram: all patients over 40 years of age

Chest radiogram: all patients over 60 years of age

ASA classification I A normal healthy patient other

than surgical pathology- without systemic disease.

II A patient with mild systemic disease – no functional limitations.

III A patient with moderate to severe systemic disturbance duo to medical or surgical disease- some functional limitation but not incapacitating.

ASA classification IV A patient with severe systemic

disturbance which poses a constant threat to life and is incapacitating.

V A moribund patient not expected to survive 24 hours with or without surgery.

E If the case is an emergency, the physical status is followed by the letter “E”-, “IIE”.

American Society of Anaesthesiologists classification and perioperative mortality rates

Class Mortality Rate I 0.06-0.08%

II 0.27-0.4%III 1.8-4.3%IV 7.8-23%V 9.4-51%

Documentation

Informed Consent The preoperative note The intraoperative

anaesthesia record The postoperative notes

Local Anaesthetic techniques Features of local anaesthesia

Preservation of consciousness The quality of early postoperative

analgesia Simplicity of administration Sympathetic blockade attenuation

of the stress response Minimal depression of ventilation

Local Anaesthetic techniques Methods of local anaesthesia

Surface anaesthesia Local infiltration Field block Regional blocks (Spinal,

epidural, & caudal blocks) Peripheral nerve blocks

Complications of local anaesthesia

Local anaesthetic toxicity( Systemic toxicity): Cardiovascular, Respiratory ， Cerebral and Immunologic

Hypotension Motor blockade Pneumothorax Urinary retention Neurological complications Equipment problems

Local anaesthetic toxicity

Systemic toxicity Cardiovascular:

Cardiac dysrhythmia or circulatory collapse is often the presenting sign of local anaesthetic overdose during anaesthesia.

Local anaesthetic toxicity

Systemic toxicity Respiratory:

Lidocaine depresses hypoxic drive. Apnea can result from phrenic and intercostal nerve paralysis or depression of the medullary respiratory center.

Local anaesthetic toxicity

Systemic toxicity Cerebral:

Early symptoms are circumoral numbness, tongue paresthesia, and dizziness. Sensory complaints may include tinnitus and blurred vision.Excitatory signs often precede central nerve system depression.

Local anaesthetic toxicity

Systemic toxicity Immunologic:

True hypersensitivity reactions to local anaesthetic agents- as distinct from systemic toxicity due to excessive plasma concentration- are quite uncommon.

Regional block equipment

Spinal needles (26G) Pencil-point 24G needles Catheters Label syringes A short length of tubing Nerve stimulators Local anaesthetic drugs

Complications of local anaesthesia Hypotension

Sympathetic blockade Total spinal blockade Vasovagal attack Anaphylactoid reaction

Regional block

Subarachnoid block(SAB): Spinal anaesthesia

Extradural nerve block: Epidural anaesthesia may be performed in the sacral(caudal block), lumbar, thoracic or cervical regions.

蛛网膜下腔阻滞联合硬脊膜外腔阻滞

Regional BlockPhysiology:

Somatic BlackadeVisceral blackadeCardiovascularPulmonaryGastrointestinalLiverUrinary tractMetabolic & Endocrine

Physiology effects of SABDifferential nerve blockade

Sympathetic fibres block sensory block Motor block

Physiology effects of SABRespiratory system Roots of the phrenic nerves:

apnoea Thoracic level: loss of intercostal

muscle activity, decrease in vital capacity, reduction in cardiac output and pulmonary artery pressure, and increased ventilation/perfution imbalance, resulting in a decrease in arterial oxygen tension (PaO2)

Physiology effects of SABCardiovascular system

Denervation of the sympathetic outflow tracts (T1-L2): dilatation of resistance and capacitance vessels and results in hypotension

Bradycardia: vasovagal syndrome; block of the cardiac sympathetic fibres

Physiology effects of SABGastrointestinal system

Sympathetic denervation and unopposed parasympathetic action : a constricted gut with increased peristaltic activity (nausea, retching or vomiting)

Physiology effects of extradural block

The physiological effect of extradural blockade are similar to those following subarachnoid block.

Spinal anaesthesia ：Indications Lower extremities Hip Perineum Lower abdomen Lumber spine

Type of surgery: Urology, Gynaecology, Obstetrics and any surgical procedure on the lower limbs or perineum.

Urologic endoscopic surgery, Rectal surgery, repair of hip fracture, obstetrics, orthopedic, Inguinal hernia repair, etc.

Spinal anaesthesia ： Contraindications

Absolute:SepsisBacteremiaSkin infection at injection siteHypovolemiaCoagulopathyTherapeutic anticoagulationDemyelating central nerve system diseaseIncreased intracranial pressurePsychosis or dementiaLack of consent

Spinal anaesthesia ： Contraindications

RelativePeripheral neuropathyMini-dose” heparinAspirin or other antiplatelet drugsPrior lumbar spine surgeryChronic back painCertain cardiac lesionsPsychologic or emotional instabilityUncooperative patients Prolonged surgerySurgery of uncertain durationSurgical team resistance to awake patients

Patient preparation Consent Physical examination Laboratory Tests Premedication

Equipment & Safety General Preparation:

Monitoring Administration of GA if

necessary Resuscitation equipment Regional equipment

Patient position Sitting position Lateral position Prone position

Technique ： Needle Technique

Midline Technique Paramedian Technique

Factors influencing spinal anaesthesia

Agents: Procaine,

Tetracaine, Lidocaine,

Bupivacaine

Dosage

Vasoconstrictors

Specific Gravity:

Hyperbaric technique,

Hypobaric technique,

Isobaric technique

Posture

Intra-abdominal

Pressure

Spinal Curvature

Prior Surgery of Spine

Age

Obesity

Pregnancy

Spread of the agent

Redistribution

Spinal anaesthesia ： Complications

Pain on injection Backache Headache Urinary Retention Meningitis and meningism Vascular injury Nerve injury: Cranial nerve palsy High spinal anaesthesia Transverse myelitis and cauda

equina syndrome

Epidural anaesthesia ： Indications

Specific IndicationsHip and knee surgeryLow extremity RevascularizationObstetric deliveriesPostoperative management

Epidural anaesthesia ：Contraindications

Epidural anaesthesia

shares the contraindications

discussed in the section on

spinal anaesthesia.

Applied Physiology for Epidural Anaesthesia

Segmental Blockade Differential Blockade

Table Agents for epidural anaesthesia

Agent Concentration Onset Sensory Block Motor Block Chloroprocaine 2% Fast Analgesic Mild to moderate

3% Fast Dense Dense lidocvaine ≥1% Intermediate Analgesic Minimal

1.5% Dense Mild to moderate 2% Intermediate Dense Dense

Mepivacaine 1% Intermediate Analgesic Minimal 2% Intermediate Dense Dense

Prilocaine 2% Fast Dense Minimal 3% Fast Dense Dense

Bupivacaine ≥0.25% Slow Analgesic Minimal 0.375-0.5% Slow Dense Mild to moderate

0.75% Slow Dense Moderate to dense

Technique of Epidural Anaesthesia

A) Safety B) Preparation of the patient

Informed consentPreoperative evaluationLaboratory assessmentPremedication

C ） Equipment: The epidural needle

Technical performance of a block

Identification of the epidural space:

Loss of resistance technique;

Hanging drop technique

Level selected Lumbar epidural anaesthesia:

Midline technique, paramedian technique

Thoracic epidural anaesthesia: Midline technique, paramedian technique

Cervical epidural anaesthesia: Midline technique

Strategies for injection of the anaesthetic agent

A test dose Incremental dosing

Choice of local anaesthetic

Agent Concentration Onset Sensory Block Motor Block

Chloroprocaine 2% Fast Analgesic Mild to moderate 3% Fast Dense Dense

lidocvaine ≥1% Intermediate Analgesic Minimal 1.5% Dense Mild to moderate 2% Intermediate Dense Dense

Mepivacaine 1% Intermediate Analgesic Minimal

2% Intermediate Dense Dense Prilocaine 2% Fast Dense Minimal

3% Fast Dense Dense Bupivacaine ≥0.25% Slow Analgesic Minimal 0.375-0.5% Slow Dense Mild to moderate 0.75% Slow Dense Moderate to dense

Factors that affect epidural anaesthesia

Dosage Patient Age Weight & Height Posture Vasoconstrictors pH adjustment of local

anaesthesia Failure of epidural block

Epidural anaesthesia Complications(Intraoperative)

Dural tap Total spinal anaesthesia Profound hypotension Apnoea Massive extradural block and

subdural block Intravenous toxitity Hypotension Shivering Nausea/ vomiting

Epidural anaesthesia Complications(Postoperative)

Headache Infection Extradural haematoma Neurological

complications

Caudal anaesthesia Indications

Obstetric patients, for vaginal deliveries

Surgery related to the sacral area (anorectal and vaginal procedures).

Caudal anaesthesia: Contraindications

The contraindications for

caudal anaesthesia are the

same as for any central block.

Caudal anaesthesia

Complications

The complications of caudal

block are essentially the same

as those associated with

epidural and spinal block.

Differences between subarachniod and extradural block

Dose of drug employed

Rate of onset

Intensity of block

Pattern of block

Subarachniod Extradural block

Small Large

Fast Slow

Complete anaesthesia Not complete

anaesthesia

Cord transection

Dermatomal

Peripheral nerve blocks

Upper limb blocks Brachial plexus block Axillary block Supraclavicular block Interscalene block

Peripheral nerve blocks

Lower limb blocks Sciatic nerve block Femoral nerve block Mid tarsal block

Question What are the complication of local

anaesthesia? What are the features of local

anaesthetic toxicity? What are the absolute

contraindications to subarachnoid block and extradural block?

Question

What are the major differences between subarachnoid block and extradural block?

How do you take the history from a patient?

What are the methods for identifying the epidural space?

Any Questions?

Thank you !