Anaesthesiology - Anatomy Flashcards

1
Q

Describe Central line

Locations for central line insertion

A

insertion of a thin, flexible catheter which is usually placed in a large vein going towards the heart. These catheters may have single or multiple lumens and can be inserted into neck or femoral veins.

Locations:
Internal jugular vein
Subclavian vein
Femoral vein

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2
Q

Describe PICC

A

PICC (peripherally inserted central catheter) are usually inserted in the upper arm through large peripheral veins (e.g. brachial, cephalic, basilic).

The tip of the line ends in the superior vena cava (SVC), so it is still considered a central line.

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3
Q

Indications for central line insertion

A

Venous access
1. Difficult peripheral venous access
2. Infusions of irritant or toxic substances e.g. concentrated ions, strong vasopressors, total parenteral nutrition (TPN), chemotherapy
3. Long term venous access required e.g. prolonged course of antibiotics in infective endocarditis
4. Potential major fluid shifts or blood loss during surgery
5. Multiple blood sampling needed

Monitoring
- Monitoring of central venous pressure (CVP) in certain types of surgery e.g. liver surgery, cardiac surgery, neurosurgery

Conduit for other procedures
1. Transvenous pacing
2. Renal replacement therapy/ plasmapheresis
3. Pulmonary artery catheter (PAFC) placement
4. Emergency aspiration of large air embolus

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4
Q

Contraindications for Central Line insertion

A
  • Patient refusal (absolute contraindication)
  • Infection over insertion site
  • Coagulopathy, thrombocytopenia (correct before insertion)
  • Uncooperative patient
  • Inability to lie flat (unless having femoral line)
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5
Q

Outline the course of the IJV

A

starts as a continuation of the sigmoid sinus at the jugular foramen
» descends in the carotid sheath lateral to internal, then common carotid arteries together with the vagus nerve
» passes deep in space between the sternal & clavicular heads of sternocleidomastoid
» joins the subclavian vein at the sternal end of the clavicle to become brachiocephalic vein.

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6
Q

Define the anterior and posterior structures to the IJV

A

Anterior- skin, fat, platysma then sternocleidomastoid muscle once lower in neck, fascia

Posterior (from above)- lateral C1, preverterbral fascia, vertebral muscles, transverse cervical process, sympathetic chain, root of neck, pleura, thoracic duct (left side only).

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7
Q

Define the approaches to central line insertion at the IJV

A

High approach: Palpate the mastoid process & the sternal notch. Draw an imaginary line between these 2 landmarks and the entry point of your needle is the halfway point on this line. Palpate the carotid artery and ensure you are lateral to it.

Low approach: The internal jugular vein is accessed at apex of the triangle formed by the 2 heads of sternocleidomastoid. Also palpate and ensure you are lateral to the carotid artery.

Advantages & disadvantages
High approach: Less risk of pneumothorax, higher risk of hitting carotid artery
Low approach: Higher risk of pneumothorax

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8
Q

Complications of IJV insertion

A

Iatrogenic damage:
i. Carotid artery- bleeding, haematoma, stroke
ii. Pleura- pneumothorax
iii. Myocardium- arrhythmias, cardiac tamponade
iv. Nerves
* Vagus- hoarse voice
* Sympathetic chain- Horner’s syndrome
* Phrenic- dyspnoea, raised hemi-diaphragm
v. Thoracic duct- chyle leak, chylothorax (left sided insertion only unless patient has aberrant anatomy)

Related to indwelling catheter
* Thrombosis
* Vein stenosis
* Infection
* Kinking, line blockage

Related to actual insertion process
* Air embolism
* Guidewire loss, shearing of guidewire, retained foreign bodies

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9
Q

Procedures for placing IJV central line

A

a. Obtain informed consent

b. Trendelenberg position, with face turned to opposite side being cannulated
(This position will increase central venous pressure- making vein fuller and easier to visualise/cannulate and reduce the risk of air embolism)

c. Use ultrasound- visualise vein and carotid artery. Can aid in cannulating vein at 1st pass, avoid hitting the carotid artery, ensuring guidewire is in the vein before dilating. Is also helpful in patient with difficult surface landmarks e.g. those with a short, fat neck

d. Strict septic technique- full gowning, chlorhexidine skin prep & sterile field

e. Use local anaesthetic if patient is awake. Prime all lumens with saline

f.** Visualise internal jugular vein with USS** halfway along imaginary line drawn from mastoid process to sternal notch. Make sure you can see where the carotid artery is

g. Cannulate vein with needle via Seldinger technique (guidewire through needle). Watch the ECG for arrhythmias. Dilate before cannulating vein

h.** Ensure blood can be aspirated** from all lumens. Flush line with saline & suture into place

i. Safely dispose of all the sharps

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10
Q

Define Anatomical position for the tip of central line

Complications of misplaced central line

A

For neck lines, the line tip should lie in the superior vena cava (SVC) above the right atrium (RA). On CXR, the level of the carina is a useful landmark.

Complications if line goes into RA:
- risk of eroding through the myocardium causing tamponade or myocardial perforation
- trigger arrhythmias
- damage to the tricuspid valve or enter the coronary sinus

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11
Q

Describe anatomical course of subclavian vein

A

Subclavian vein is the continuation of the axillary vein, it becomes the subclavian vein at the lateral border of the 1st rib. It runs under the clavicle anterior to the subclavian artery, separated from it by the anterior scalene. At the sternal edge of the clavicle, it joins the internal jugular vein to become the brachiocephalic vein.

The phrenic nerve runs posterior to the vein and the thoracic duct joins the left subclavian vein close to its junction with the left internal jugular. The lung pleura lies inferior to the medial aspect of the vein

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12
Q

Define central line insertion point for Subclavian vein

Complications of subclavian vein cannulation

A

inserted at a point just below the clavicle at point dividing it into its medial 2/3 and lateral 1/3. The needle should be advanced with the tip pointing towards the sternal notch, aspirating all the time.

Complications:
* potential lung injury, haemothorax, tracheal injury, recurrent laryngeal nerve injury
* higher risk of pneumothorax compared to internal jugular cannulation
* harder to apply manual pressure in the event of bleeding.

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13
Q

Define the anatomical course of the femoral vein

A

Femoral vein is the continuation of the popliteal vein at the adductor hiatus. It ascends the anteromedial thigh into the femoral triangle where it lies medial to the femoral artery in the femoral sheath. It is joined by the deep femoral vein & the saphenous veins before this point. It continues as the external iliac vein as it passes under the inguinal ligament. The needle insertion point is 2cm below the inguinal ligament, medial to the femoral artery.

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14
Q

Contraindications and complicatins of femoral vein cannulation

A

Contraindications
* Patient refusal (absolute contraindication)
* Infection over insertion site
* Coagulopathy, thrombocytopenia (correct before insertion)
* Uncooperative patient
* intra-abdominal haemorrhage, abdominal trauma

Complications
* femoral nerve damage, bladder/ bowel perforation,
* haematoma, retroperitoneal bleeding, femoral artery damage, vein stenosis, pseudo-aneurysm formation.
* High risk of thromboembolic complications and infection

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15
Q

Advantages and drawbacks of neck vein central lines

A
  • More accurate CVP measurement
  • More comfortable than femoral vein
  • Easier to insert with USS
  • Lower risk of pneumothroax (High approach + USS)
  • Can apply pressure for excessive bleeding (not for subclavian vein); excess pressure can cause stroke
  • Easier to keep clean (IJV line may be contaminated by saliva bacteria in intubated pt)
  • Safe with low complication rate
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16
Q

Advantages of drawbacks femoral vein central lines

A
  • For use in emergency, no need to lie flat (esp if pt is dyspnoeic)
  • No pneumothroax risk
  • Easy to apply pressure if bleeding, no risk of stroke if high pressure applied to bleeding site
  • Hard to keep clean, easily contaminated by groin bacteria
  • Safe with low overall complication rate
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17
Q

Define central neuro-axial block

A

Administration of medication (usually local anaesthetic) into the subarachnoid or epidural space to produce anaesthesia and analgesia.

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18
Q

Define types of neuro-axial blocks

A
  • Spinal anaesthesia- deposition of drugs into the subarachnoid space, which usually contains around 20ml CSF. The enlarged dural sac inferior to the conus medullaris is the target site for injection
  • Epidural anaesthesia- deposition of drugs into the epidural space. This space is defined as the space within the spinal canal that is outside of the dura mater
  • Caudal anaesthesia- access to the epidural space via the sacrococcygeal membrane is a popular technique in children
  • Combined spinal-epidural anaesthesia- combines effect of spinal & epidural
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19
Q

Define the anatomical boundaries of the epidural space

A

Extends from the foramen magnum to the sacrococcygeal membrane.

Boundaries
* Internal- dura mater
* Posterior- ligamentum flavum
* Anterior- posterior longitudinal ligament
* Lateral- intervertebral foramina

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20
Q

Contents of the epidural space

A

Epidural fat
Epidural blood vessels- Batson’s plexus, a valveless communication between pelvic & cerebral veins
Lymphatics
Spinal nerve roots
Connective tissue (reason why some blocks are “patchy”)

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21
Q

Define the depth of epidural space from skin

A
  • Depth of space 6mm lumbar, 1mm cervical
  • Negative pressure (transmission of negative intra-pleural pressure from paravertebral space)
  • Distance from skin 2-9cm (deeper in the obese)
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22
Q

Define all the structures traversed from skin to epidural space

Which structure gives resistance during needle puncture

A

Ligamentum flavum gives ‘gripping’ sensation

The needle is advanced through the ligamentum flavum whilst pushing on the syringe plunger, but it is difficult to inject the saline. Once the needle tip reaches the epidural space with its negative pressure, there is a sudden loss of resistance and saline can be easily injected.

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23
Q

Approaches for spinal or epidural space

A

Midline approach

Ease of epidural insertion- lumbar>thoracic>cervical. This is because the spinous processes are more perpendicular to the vertebral body in the lumbar compared to the cervical region. In the thoracic region, the spinous processes point downwards, therefore the angle of approach is more acute so the needle is more likely to hit bone.

Paramedian approach

The needle is inserted 0.5-1cm off the midline, contact with the lamina is made then needle is “walked off” and directed caudally and medially towards the epidural space. As the interlaminar distance is larger as you move laterally from the midline, whether the patient can maximally flex their spine is less crucial than with the midline approach.

24
Q

Landmarks for neuroaxial block

A

C7 bony prominence at the base of neck
T7-8 lower border of scapula
L4 line drawn at level of uppermost point of iliac crest

25
Q

Define which nerve fibers are blocked first in neuro-axial blocks.

A

Speed at which fibres are blocked: Sympathetics> pain> touch> motor

Block height is also exhibits this phenomenon. Sympathetic block is usually 2-4 dermatomes higher than motor block. Pain & touch can be 2-3 dermatomes beyond motor block.

26
Q

Procedure for epidural block

A
  • Obtain informed consent, check contraindications. Never perform blocks on anaesthetised patients (they can tell you if your needle hits nerves etc.)
  • Position patient- lateral or sitting position with back arched to open up spinal column
  • Full asepsis- gown, gloves, cap, mask. Clean skin with chlorhexidine. Use a sterile field
  • Identify your level (choose uppermost dermatome of surgical incision), infiltrate with local anaesthetic.
  • Advance Tuohy needle (16-18G in adult) slowly until ligamentum flavum is reached. Push plunger of LOR syringe (filled with saline) until LOR detected. Reposition needle if bone is encountered, patient complains of paraesthesiae or severe pain.
  • Note distance from skin to epidural space & thread catheter to this distance +4-6cm. Remove needle
27
Q

Tests to confirm needle insertion into epidural space

A
  1. Negative aspiration of blood & CSF
  2. Flush catheter with saline, remove filter & check fluid meniscus falls (due to the negative pressure)
  3. Give test dose e.g. 3ml 2% lidocaine with adrenaline and wait

If intrathecal- patient will develop sensory or motor block
If intravascular- patient may develop a tachycardia (from adrenaline)

28
Q

Tests to confirm neuroaxial block is working

A
  • Use ice to check level of temperature fibres blocked
  • Use light touch to check sensory dermatome level
  • Check motor block of lower limbs. There should be a dense motor block if spinal is working. (With epidural anaesthesia, low dose LA is usually utilised with minimal motor block. A dense motor block after epidural anaesthesia may indicate intrathecal placement of LA or nerve damage from spinal cord ischaemia.)
  • Check patient’s BP, usually drops due to sympathetic block
29
Q

Methods to modulate the intra-thecal spread of LA in neuroaxial blocks

A
  1. Baricity of local anaesthetic solution
    - Heavy bupivacaine- glucose is added to render solution hyperbaric compared to CSF. This means the drug will tend to sink in the direction of gravity with less variability in spread.
    -Plain bupivacaine- usually hypobaric compared to CSF, with greater variability in spread and less predictable block height.
  2. Dose- dose of drug is more important than volume. Higher drug doses will result in higher blocks and longer duration of action (can cause unintentional total spinal anaesthesia)
  3. Opioid additives- opioids increase mean spread & delay block regression. Addition of long acting opioids can prolong duration of anaesthesia & analgesia.
  4. Patient position- ultimate block height is an interplay between baricity of LA, dose & patient position after injection. Saddle block can be achieved using hyperbaric bupivacaine & keeping the patient in the sitting position. Trendelenberg position will lead to higher block height, due to the effects of gravity. Hip & knee flexion after injection flattens the lumbar lordosis, increasing cephalad spread, leading to higher block levels.
  5. Anatomy of spine- Normal spine has a lumbar lordosis with L4 as its highest point and this lumbar lordosis limits spread of LA. Due to increased lumbar lordosis in pregnancy, local anaesthetic spreads more extensively so than standard doses of local anaesthetic which can usually achieve a good block to around T8- T10 in the non-pregnant patient, can produce a sensory block to T5 in the term parturient, which is adequate for LSCS. Scoliosis usually does not affect spread but a kyphoscoliosis may do so.
30
Q

Complications of neuroaxial block

A
  1. Failure with inadequate, patchy or one-sided block. (Procedure is blind, catheter may go one sided, uneven spread of LA from connective tissue in epidural space etc.)
  2. Hypotension- from sympathetic block leading to vasodilatation, reduced preload & SVR. Hypotension can lead to severe nausea & vomiting.
  3. Intravascular injection
  4. Infection (foreign body placed in CNS)
  5. High block from extensive LA spread
  6. Dural puncture- leads to reduced ICP from CSF leak, risk of coning if patient has raised ICP or a space occupying lesion.
  7. Subdural block: result in a comparatively high sensory block (in relation to amount of LA given)
  8. Bleeding- blood clots may compress the spinal cord (confined space) with mass effect & spinal cord ischaemia
  9. Direct nerve damage from needle
  10. Neurotoxicity
    * If large doses are given e.g. epidural dose given intrathecally
    * Contamination of needle or catheter with chlorhexidine
    * Effect of LA on patients with neurological disease e.g. multiple sclerosis is unknown
31
Q

Treatment of dural puncture

A

the patient may develop a very severe and debilitating headache if there’s continued CSF leak from dural puncture from a spinal needle

treated by injecting patient’s own blood epidurally under aseptic conditions at a one level below or same level as the original puncture site. The blood should form a clot, sealing the dural hole, forming epidural blood patch.

32
Q

Consequences of high block at various spinal levels

A
  • T1-4 cardiac sympathetic block- bradycardia, hypotension
  • C6-8 hand & arm weakness, SOB due to accessory/ respiratory muscle weakness
  • C3-5 diaphragm weakness- hypoventilation, desaturation
  • Intracranial- brainstem anaesthetised, known as “total spinal” with LOC, slurred speech, apnoea, cranial nerve palsies, reduced HR & BP
33
Q

Indications for central neuro-axial block

A
  1. surgical procedures preferably at umbilical level or below (below T10)
  2. postoperative analgesia, improved post-operative respiratory function due to less pain, reduced pain scores, avoidance of systemic opioids & their side effects
  3. labour analgesia
34
Q

Contraindications to central neuroaxial block

A
  1. Patient refusal (absolute contraindication)
  2. Infection- over insertion site (absolute contraindication), systemic (relative contraindication)
  3. Severe uncorrected hypovolaemia
  4. Significant cardiac disease e.g. severe AS, MS, HOCM (large reduction in preload & afterload may lead to significant haemodynamic instability in patients with fixed cardiac output states especially if associated with a high sympathetic block)
  5. Raised ICP/ SOL (risk of cerebral herniation)
  6. Abnormal vertebral column (altered anatomy-unpredictable LA spread & technically challenging insertion)
35
Q

Compare spinal and epidural anesthesia

A
36
Q

Define the anatomical components of the larynx

A

The larynx separates the lower airway from the upper airway. It sits in the anterior neck at the level of C4-C6. Laterally lies the carotid sheath & the thyroid lobes. It is made up of:

a. Cartilages
Unpaired- thyroid, cricoid & epiglottis (hyoid is a bone and not strictly part of the larynx) cartilages
Paired- arytenoids, cuneiform & corniculate cartilages

b. Ligaments and membranes

c. Muscles

37
Q

Define the cartilages of the larynx

A

Unpaired- thyroid, cricoid & epiglottis (hyoid is a bone and not strictly part of the larynx) cartilages
Paired- arytenoids, cuneiform & corniculate cartilages

38
Q

Define the ligaments and muscles of the larynx

A

Ligaments and membranes: Ligaments hold the cartilages together & the membranes are part of the vocal structures.
* Cricothyroid membrane
* Thyrohyoid membrane
* Cricovocal ligament
* Hyoepiglottic ligament
* Cricotracheal ligament

Muscles
* Intrinsic- controls vocal cord aperture
* Extrinsic- anchors larynx to surrounding structures

39
Q

Define the nerve supply to the larynx

A

The larynx is supplied by branches of the vagus nerve. (Tongue base & vallecula are supplied by the glossopharyngeal nerve)

  1. Superior laryngeal nerve
    Internal branch- sensation to glottis, supraglottis & inferior epiglottis
    External branch- motor to cricothyroid muscle which tenses the vocal cord
  2. Recurrent laryngeal nerve- supplies all other intrinsic muscles of the larynx and sensation to the subglottis
40
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45
Q

Functions of the larynx

A

a. Production of voice- by controlling size of vocal aperture and the height of the larynx

b. Protection of the lower airway- laryngeal aperture is covered by the epiglottis during swallowing to prevent food going down into lower airway

c. Production of Valsalva manoeuvre- forced expiration against closed glottis
* Check for venous haemostasis during surgery
* Check autonomic nervous system integrity
* Termination of arrhythmias e.g. SVT

46
Q

Method to prevent aspiration during rapid sequence of induction of anesthesia

A

The cricoid cartilage is the only complete ring of cartilage that makes up the larynx. The theory is that applied backwards pressure on this cartilage of 20-44N should occlude the oesophagus and prevent passage of regurgitated stomach contents into the patient’s trachea. It is a component of rapid sequence induction of anaesthesia.

47
Q

Define emergency front of neck access

A

Emergency front of neck access (FONA)- cricothyroid membrane may be punctured to access the lower airway below the level of the vocal cords in an emergency e.g. cannot intubate, cannot ventilate situation to perform needle or surgical cricothyroidotomy.

A cannula or special tube is inserted to provide means of TEMPORARY emergency oxygenation.

The cricothyroid membrane can be identified using USS in difficult patients and the site marked prior to commencing anaesthesia if needed.

48
Q

Use of cricothyroid membrane in anesthesiology

A
  1. Emergency front of neck access (FONA)
  2. Anaesthetising inferior part of vocal cords and trachea as part of awake fibreoptic intubation technique.
  3. Rescue devices such as Ravussin cannula into difficult airway prior to induction of general anaesthesia (e.g. in “can’t intubate, can’t ventilate” situation)
49
Q

Brachial plexus anatomy

A
50
Q

Define the roots, trunks and divisions of the brachial plexus

A

The brachial plexus is derived from the anterior rami of the spinal nerves C5-T1. It ends in the axilla with the formation of its terminal branches. Before this, various preterminal branches are given off

Roots- The roots (as the ventral rami are called) join to form 3 trunks.** 3 lateral branches come off the roots- dorsal scapular nerve, long thoracic nerve & intercostal nerve**

Trunks-** Roots of C5 & C6 form superior trunk, C7 continues as the medial trunk and C8 & T1 join to form the inferior trunk.** After their origin, trunks pass over the base of the posterior triangle & travel between the anterior & interscalene muscles behind the subclavian artery. They then cross the apex of the lung & 1st rib towards the clavicle. Superior trunk gives off the suprascapular & subclavian nerves as preterminal branches

Divisions- At the posterior aspect of the middle third of the clavicle, each trunk divides onto anterior & posterior divisions. These then continue to pass behind the clavicle towards the axilla.

51
Q

Define the cords and terminal branches of the brachial plexus

A

Cords- Lateral, posterior & medial cords are formed & described by their relationship to the axillary artery. Lateral cord is formed from the anterior divisions of the superior & middle trunks. Medial cord is the continuation of the anterior division of the inferior trunk. The posterior cord is formed from the 3 posterior divisions of the 3 trunks

Terminal branches- The cords terminate at the inferior margin of the pectoralis minor. Lateral cord gives off the musculocutaneous and lateral root of the median nerve. Posterior cord gives off the radial & axillary nerves. The medial cord gives off the ulnar nerve & medial root of the median nerve

52
Q

Approaches for brachial plexus block

A
53
Q

Define the location for each brachial plexus block

A
54
Q

Methods to ensure safe brachial plexus block

A
  • Always perform in awake patients (patient can warn you of possible intraneural injection)
  • Prepare patient as if for GA- adequate fasting, full monitoring, intravenous access
  • Use USS guidance to delineate anatomy, helps to avoid intravascular injection, avoid hitting nerves, pleura etc.
  • Ensure negative aspiration (may aspirate blood/ CSF) & slow injection. Check resistance to injection is low (high resistance may indicate intraneural injection). Check spread of LA on USS is as expected
55
Q

General Complications of brachial plexus blocks

A

General complications of any nerve block- failure, bleeding, infection, nerve damage, intravascular injection of local anaesthetic, intraneural injection

56
Q

Specific anatomical complications of brachial plexus blocks

A

Interscalene
* Horner’s syndrome (Stellate ganglion blocked)
* Bleeding, i.v. injection (vertebral artery)
* Total spinal anaesthesia- epidural, intrathecal spread
* Pneumothorax
* Phrenic nerve palsy
* Hoarseness (recurrent laryngeal nerve block)

Supraclavicular Pneumothorax/ haemothorax
* Phrenic nerve palsy (lower risk than interscalene)
* Horner’s syndrome
* Bleeding, i.v. injection- (vessel rich area- subclavian,
transverse cervical, dorsal scapular arteries)

Infraclavicular
* Pneumothorax
* Haematoma (axillary artery)
* Axillary Haematoma (axillary artery)

57
Q

Limitations of brachial plexus blocks

A