Anatomy Flashcards
Anatomy Qs approach
Description, function, boundaries, relations, vascular, nervous, points of interest
Standard requirements for blocks: full anaesthetic assessment and informed consent, monitoring, IV access, emergency drugs and resuscitation equipment, trained assistant, sterile equipment and light source, stop before you block (ACMI ET SBYB)
Block indications: surgery, trauma, pain, other
Block risks: immediate (failure/inadequacy, intraneural injection, IV injection/LA toxicity), early (haematoma, motor block), late (infection, compression neuropathy, persisting sensory loss or weakness)
Ankle block*
Femoral –> saphenous (medial border of foot)
Sciatic –> sural (lateral border of foot), posterior tibial (sole), superficial peroneal (dorsum and web spaces), deep peroneal (first web space)
Options: GA, neuraxial, paravertebral, lumbosacral plexus, sciatic/femoral, popliteal fossa, ankle block
- Tibial: sciatic nerve divides at apex of popliteal fossa. Tibial runs between heads of gastrocnemius then supplies calf/heel and runs behind medial malleolus and terminates as medial and lateral plantar branches which supply sole. Block anterior to tibial artery pulsation in posterior groove of medial malleolus.
- Sural: is actually a branch of tibial; passes behind lateral malleolus to supply lateral border of foot and 5th toe. Block in posterior groove of lateral malleolus - SC infiltration.
- CPN winds round neck of fibula and divides. Superficial supplies dorsum of foot. Deep is first web space. Deep: block between extensor hallucis longus tendon and DP artery proximal to first metatarsal web space. Superficial: block by SC infiltration (5-10ml, largest volume) between extensor hallucis longus tendon and lateral malleolus.
- Saphenous: terminal branch of saphenous. Supplies medial calf, medial malleolus and medial arch. Runs with saphenous vein. Block medial to extensor hallucis longus tendon.
Ind for block: forefoot surgery e.g. metatarsal osteotomy, Morton’s neuroma excision, amputation
Antecubital fossa
- Boundaries
- Contents
- Indications for vessel cannulation
- Complications/structures at risk
Contents: 531 (5 nerves, 3 veins, 1 artery)
At risk: brachial artery beneath median cubital vein, lateral cutaneous nerve of the forearm beneath cephalic vein
I: diagnostic/therapeutic (sampling, invasive BP, access - peripheral/central)
C: immediate/early (misplacement, injury to other structures, extravasation, air emboli, critical ischaemia), late (infection, thrombophlebitis)
PICC line insertion
Autonomic nervous system (RCoA old book, past Q)
Sympathetic blocks
Denervated heart
Types of ganglia
Sympathetic ganglia: cervical (3 - C1-C8), stellate (C7-T1), thoracic (12), lumbar (4), sacral (4)
Sympathetic plexi: cardiac (deep and superficial), coeliac (biggest), hypogastric
Axilla
Pyramidal
Boundaries: pec major, lat dorsi, serratus anterior, coracobrachialis
Contents: axillary artery, axillary vein, brachial plexus, LNs
Base of skull
.
Brachial plexus*
Axillary block (RCoA old book) + others
Roots - interscalene, trunks - supraclavicular, cords - infraclavicular, branches - axillary.
Infraclavicular - can be performed landmark - midpoint of line from suprasternal notch and acromion. 50mm needle inserted vertically. Cords are at 2-3cm. Wrist/finger extension (posterior cord) for best results. Risks: PTX, IV/IN inj, pectoralis haematoma, failure.
Needle should be cathode if using nerve stim
BP supplies all of arms apart from trapezius (spinal accessory nerve) and skin over medial aspect of axilla (intercostobrachial nerve).
Roots and trunks lie in posterior triangle. Trunks emerge between anterior and middle scalenes. Plexus leaves neck by crossing mid-clavicle.
Causes of injury: those relating to BP blocks/other procedures in area; and stretching from positioning, retractors, tourniquet. Avoid arm abduction >90 degrees, head neutral, US guidance, aspiration, blocks awake etc.
CIs to block: generic ones + adverse neck anatomy, contralateral PTX, pre-existing neurology
Bronchi and bronchial tree
.
Central neuraxial blockade
- CIs (absolute/relative)
- Benefits
- Risks (early/late)
- Epidural space
- Caudal (Krishnachetty)
CIs: abs (refusal, LA allergy, local sepsis), rel (coagulopathy, thrombocytopenia, hypovolaemia, cardiac stenotic lesions)
Benefits: gold standard analgesia, reduced opioid req, lower blood loss, faster liberation from MV, shorter ICU LoS (psychological/financial/economic benefits), earlier recovery of gut function/feeding, reduced postop comps (VTE, LRTI, wound infection, N&V, MI, resp depression, possibly mortality (controversial))
Risks: early (hypotension, N&V, shivering, pruritis, failure/inadequacy, unilateral block, subdural block, misplacement or migration (IV, intrathecal - LA toxicity/total spinal), dural tap; late (PDPH, urinary retention, nerve damage, epidural haematoma, epidural abscess/other infection)
Caudal: Armitage
Cervical plexus blocks (past Q)
Deep = higher complication rate
Supine/semi sitting, head turned away
Landmarks: mastoid C1, cricoid C6 (Chassaignac’s tubercle - TP of C6). Moore (multi shot) technique. Line between mastoid and Chass. 2nd line parallel and 1cm posterior. C2 TP is 1-2cm caudal to mastoid on the 2nd line. C3 and C4 are then 1-2cm below respectively. LA to skin then 22G needle inserted posterior and caudad until TP encountered or parasthesiae felt. Then aspirate and inject 3ml at each level. A single shot technique also exists (Winnie).
Superficial (safer)
25G needle, midpoint of the posterior border of sternocleidomastoid, depth of 1cm, fan/sausage shape, 20ml.
Cervical spine
.
Circle of Willis (past Q)
.
Coeliac plexus
- Block
I: analgesic (acute post laparotomy, chronic pain e.g. pancreatitis) or neurolytic (e.g. ca pancreas)
CI: refusal, coagulopathy, sepsis, AAA
Coeliac plexus is Posterior to Pancreas and Anterior to Aorta
T: fluoroscopic guided; sedation, IV fluids, pt prone, 20G 10-15cm needle at L1 level just below tip of 12th rib and 7.5cm out from midline, advance to touch L1 vertebral body, withdraw and angle anterior, advance 2-3cm, confirm with contrast (excludes epidural/IV placement) (can also be done endoscopic US-guided, or CT-guided)
Non-ca pain: 15ml 0.5% bupivacaine each side; ca pain: 20ml 5% phenol or 50% alcohol
C: immediate (injury to viscera/great vessels - retroperitoneal haematoma, IV/SA/epi injection), early (anterior spinal artery syndrome, hypotension due to splanchnic vasodilatation, diarrhoea, acute pancreatitis, peritonitis, lumbar plexus irritation), late (sexual dysfunction, pain recurrence, painful neuroma formation)
Coronary circulation*
R aortic sinus –> RCA: gives off PDA (determines dominance) and R marginal. Supplies SAN in 65%, AVN in 80%, rest of conducting system in 80%. Supplies RA, RV and part of septum.
L aortic sinus –> LMS: gives off LAD, Cx and L marginal. Supplies LA/LV, part of RV and part of septum.
2/3 venous drainage is by veins that accompany coronary arteries and drain into RA. Great (with LAD), middle (with Cx/RCA) and small (with R marginal) cardiac veins drain into coronary sinus. Also anterior and oblique veins. Smallest cardiac veins = Thebesian veins (drain endo/myocardium directly into heart).
Cranial nerves* (and monitoring - Krishnachetty, past Q)
Why monitor? Prevent intraop injury, monitoring neuromuscular blockade, brainstem death testing. Implications - affects our use of MRs and volatiles (need TIVA), requires control of temp/BP/acid-base, and EMI can occur.
Five
Largest CN. Motor to muscles of mastication, sensory to face/scalp. 1 motor nucleus, 3 sensory (mesencephalic, principal sensory, spinal tract). Fibres emerge from pons. Sensory fibres go through trigeminal ganglion (at apex of petrous temporal bone), motor bypass it and join Viii. Divide into i (sensory), ii (sensory) and iii (mixed). Vi - SOF, frontal/lacrimal/nasociliary nerves. Vii - foramen rotundum, facial branches then infraorbital nerve. Viii - foramen ovale, auriculotemporal, buccal, lingual and inferior alveolar nerves.
In BST: corneal reflex (Vi to VII) and supraorbital pressure (V to VII).
Seven
Branches: Two Zulus Buggered My Cat (temporal, zygomatic, buccal, mandibular, cervical)
Ten
Path: jugular foramen, carotid sheath, behind respective brachiocephalic veins, travels posterior to respective lung hila, pierces diaphragm at T10
BST - all except I, XI, XII. Know the afferents and efferents
Monitoring in surgery
1 - cannot be monitored; 2 - rarely
3/4/6/11/12 - base of skull
5 - MVD for trigeminal neuralgia
7 - parotidectomy, CPA tumour
8 - CPA tumour (by auditory evoked potentials)
9 - radical neck dissection
10 - thyroidectomy/vocal cord surgery/cholesteatoma
Diaphragm and phrenic nerve
Main muscle of respiration (75% of function during quiet breathing); separates thorax and abdomen.
Dome shaped and reaches 5th rib on R and 5th ICS on L on expiration. Excursion is 1.5cm normally, up to 10cm in deep breathing.
Central tendinous portion and peripheral muscular area. Central tendon blends with fibrous pericardium above. Muscular portion: sternal (from xiphoid), lumbar (R and L crura from vertebral bodies L1-3) and costal (cartilages of T6-12) origins. Arcuate ligaments: lateral (quadratus lumborum), medial (psoas) and median (between crura).
T8: IVC, R phrenic. T10: oesophagus, vagi, gastric vessels. T12: aorta, azygos, thoracic duct. Other openings transmit superior epigastric vessels, lymphatics, sympathetic trunk and L phrenic.
Innervation: phrenic (mixed) to central tendon and lower intercostals (sensory) to muscular region.
U/L raised hemidiaphragm: phrenic nerve palsy, (hepatomegaly). B/L: any cause of enlarged abdomen (FFFFFF!)
GA reduces inferior movement of diaphragm - predisposes to atelectasis. In SV GA, movement of dependent portions is greatest, and vice versa for IPPV/paralysed.
Diaphragmatic rupture: 5% of blunt abdo trauma, more common on L (no liver), sx due to abdo contents in chest - pain, DIB, reduced breath sounds.
NAVA - neurally adjusted ventilatory assist.
Phrenic nerve: anterior rami of C3/4/5, descends in neck beneath sternocleidomastoid, then passes in front of subclavian artery at thoracic inlet. Descends in front of root of lung then between pericardium and mediastinal pleura. Branches to supply motor and sensation to diaphragm.
Epidural space*
Layers: skin, fat, interspinous, supraspinous, ligamentum flavum, epidural space (then dura, subarachnoid space)
Approaches: cervical, thoracic, lumbar, caudal. Midline, paramedian. Interlaminar (usual), transforaminal, transsacral, paravertebral, direct vision with spinal endoscopy.
The epidural space is the area that surrounds the dural sheath within the vertebral canal. Runs from foramen magnum to sacrococcygeal mem. Lumbar epidural space especially is discontinuous and divides into segments where dura connects to spinal canal; normally permits passage of fluids and catheter. Tethering can produce patchy block or inadvertent dural puncture.
Boundaries
Anterior: vertebral bodies/intevertebral discs/posterior longitudinal ligament
Lateral: pedicles and intervertebral foramina. Connected to paravertebral space via lateral foramina.
Posterior: vertebral laminae/ligamentum flavum.
Contents: anterior, posterior and lateral compartments. Contains spinal nerves with an investing cuff of dura, fat, connective tissue, lymphatics and vessels. The veins run vertically and form one trunk either side of the posterior longitudinal ligament, and two posteriorly; they are valveless and have high abdo pressure transmitted to them.
Benefits: superior analgesia (MASTER trial 2002), reduced VTE, reduced atelectasis/LRTI, reduced SNS activity/attenuated stress response, avoidance of opioid problems (resp depression, sedation, ileus, nausea and vomiting).
Eye and orbit* (RCoA old book)
- Boundaries/contents
- Innervation
- Blocks - technique, pros and cons of RA for eye surgery
Orbit = pyramidal, base at front. Contains two compartments: intraconal and extraconal spaces (within or without the rectus muscles, respectively). Three openings: SOF (CN3/4/6/5i/superior orbital vein), IOF (Vii, inferior ophthalmic vein, infra-orbital artery), optic canal (II, ophthalmic artery, central retinal vein).
Boundaries. Roof: frontal bone. Floor: maxilla and zygoma. Lateral: zygoma and greater wing of sphenoid. Medial: maxilla, lacrimal bone, ethmoid and sphenoid.
Globe layers: conjunctiva, cornea/Tenon’s capsule, sclera, choroid, retina.
Muscles: 4 rectus, 2 oblique. Unite at apex of orbit to form annulus of Zinn.
Innervation:
- Motor: LR6SO4
- Sensory: II (retina to optic chiasm), Vi (lacrimal, nasociliary, frontal nerves via SOF), Vii (infra-orbital nerve via IOF), VII (orbicularis oculi)
- Autonomic (SNS - mydriasis (T1 outflow –> superior cervical ganglion –> short and long ciliary nerves), PNS - meiosis (Edinger-Westphal nucleus –> III –> ciliary ganglion –> short ciliary nerves)
Blocks:
- Peribulbar: extraconal, 5-10ml LA, shorter needle, inferotemporal, may need medial supplementation. 6-10ml.
- Retrobulbar: intraconal, 40mm 25G needle, inferotemporal (fewer blood vessels), 5ml LA, percutaneous or transconjunctival, risk of globe perforation and N/V injury. 1.5-4ml.
- Sub-Tenon’s: Topical LA and iodine drops. Retractor inserted, pt looks up and out. Inferonasally, tent conjunctiva with forceps, small incision. Blunt dissection down to Tenon’s fascia to sclera. Blunt 19G cannula curved around, becoming vertical beyond equator. Aspirate, inj 3-5ml. Some proptosis normal; excessive chemosis = subconjunctival (analgesia but not akinesia). Apply pressure/Honan balloon (spreads LA, lowers IOP by reducing AH production). Success = akinesia, ptosis, inability to close eye.
- Also: sunconjunctival and topical LA.
Eye block pros: better for day case, avoid GA comps, intraop analgesia and akinesia, postop analgesia, blunts oculo-cardiac reflex
Eye block cons: CIs include axial length>26mm, inability to lie flat/still, INR>2.5, previous retinal detachment, eye trauma, local infection. Not suitable for long surgery. Risks: IV/SA/subconjunctival spread, injury to globe/extraocular muscles/vessels (retrobulbar/subconjunctival haemorrhage), raised IOP, LA toxicity, anaphylaxis, oculocardiac reflex, optic nerve atrophy.
Oculocardiac reflex: bradycardia due to traction on eye, esp medial rectus. Short and long ciliary nerves –> trigeminal ganglion. Efferent = vagus to SAN. Release traction, give atropine. Avoid by prophylactic atropine, avoid hypoxia/hypercapnoea/light planes of anaesthesia.
Eye pain postop: acuity, fields, fundoscopy, reflexes, slit lamp. Causes.
Fascia iliaca
I: #NOF, hip/knee surgery (may need sciatic block too)
CI: abs (refusal, allergy, infection), rel (sepsis, coag/plts, LL neuro deficit, ipsilateral renal graft)
T: line btwn ASIS-pubic tubercle, junction of lat/middle thirds, 1cm inferior. 2 clicks (fascia lata, fascia iliaca), aspirate. Up to 30ml or catheter.
More consistent and better analgesia than ‘3 in 1’ block - femoral, obturator and lateral femoral cutaneous nerves
Will not block higher branches of lumbar plexus, risk of visceral/vascular injury/injection
Femoral nerve and triangle
L2-4 anterior primary rami –> posterior divisions unite in psoas to form femoral nerve –> travels down on iliacus –> crosses inguinal ligament lateral to vessels –> enters femoral triangle –> divides into ant/post branches just below inguinal ligament
Ant: medial and intermediate cut. nerves of thigh supply skin front and medial thigh; motor branches to sartorius and pectineus
Post: 3 branches - articular branch (innervates hip/knee), muscular branch (quadriceps) and terminal saphenous nerve (runs through adductor canal, becomes superficial and supplies skin medial calf)
T: nerve stim 45 degrees, 1cm lat to pulse, 1-3cm, 2 clicks, quads should contract (patella moves). If sartorius contracts, move lateral. 15-20ml.
Femoral triangle borders: inguinal ligament, adductor longus, sartorius. Floor = pectineus, adductor longus, iliopsoas. Roof = fascia lata and cribriform fascia. Contents = femoral nerve, femoral sheath (contains FA, FV, femoral canal (contains lymphatics/LNs)).
Fetal circulation and placenta
- Oxygenated blood enters fetus via umbilical vein (SpO2 70%)
- Mixes with deoxygenated blood in ductus venosus
- Travels up IVC to RA
- Most blood in RA goes straight to LA via PFO (small amount goes to RV and then lungs, and via PDA to aorta)
- Mixes with deoxygenated blood from lungs
- Ejected by LV into aorta, which divides into two umbilical arteries
Transitional circulation: umbilical cord clamped and baby takes breath so R sided pressures fall. L sided pressures rise and foramen ovale is flapped shut (immediate functional closure). All RA blood must now go to RV. PDA constricts in response to high PaO2 (functional closure by 12h). Transition complete by 3/12 - anatomical fusion of foramen ovale and obliteration of PDA.
Inguinal region
Nerves (4): subcostal (T11-12 lateral cut. branches), iliohypogastric (upper gluteal, lat. abdo wall), ilio-inguinal (TA/IO muscles, pubic symphysis, femoral triangle and genitalia), genitofemoral (–> genital and femoral branches)
Combined field block of IH/II/GF:
- 2cm inf/med to ASIS, 1 click through EO = IH; 5ml
- Advance 1-2cm, 2nd click through IO = II; 5ml
- Fanwise infiltration around ASIS blocks small branches from the above
- Fanwise lateral to pubic tubercle towards external ring blocks GF; 5ml
Often needs supplementation by surgeon; risk of intraperitoneal injury and inadvertent femoral nerve block; but can avoid GA, opioid sparing, quicker recovery than spinal
Intercostal nerve
- Anatomy/course
- Block - indications, technique, risks
Ventral and dorsal thoracic spinal nerve roots unite, exit via intervertebral foramen, then divide into anterior and posterior rami. Posterior ramus supplies back extensors and skin. Anterior ramus (i.e. the intercostal nerve) runs in the N/V bundle below rib and travels round chest; innervates intercostal and transverse thoracic muscles. At mid-axillary line, gives off lat. cut. branch (sensory up to MCL), then terminates as ant. cut. branch (sensory from MAL to ant. midline of chest wall). IN is connected to sympathetic chain via grey and white rami communicantes. IN is initially btwn pleura and post. intercostal membrane, then btwn internal and innermost intercostal muscle layers.
IN block: rib #, intercostal procedures e.g. drain, postop analgesia (thoracic/upper abdo; 2 levels above + below; superseded), acute herpes zoster, chronic pain. Tether skin. Inject at or before angle of rib to include lat. cut. branch. Insert needle 20deg cephalad, hit lower rib border, release skin to make needle horizontal, walk off rib, advance 2-3mm (pleura is at 8mm). Aspirate, inject 2-5ml. Risk of PTX, vessel injury, SA inj (dural cuff can extend 8cm), resp distress/diaphragm palsy (esp. in COPD etc), IV inj/LA toxicity (rapid absorption - rich blood supply), spread to adjacent levels/sympathetic chain blockade.
Internal jugular vein (past Q)
- Anatomy/course
- Cannulation: indications, technique, risks
- Ant/post triangles of the neck
- Subclavian
IJV formed by unification of sigmoid sinus and inferior petrosal sinus; exits skull via JF with CNs 9/10/11, runs down neck in carotid sheath with ICA and vagus nerve. RLN is medial. IJV is usually posterior, lateral then anterolateral to ICA as it runs down. Upper half is superficial, lower half deep to sternocleidomastoid. Terminates by joining SCV behind manubrium to form BCV.
Uses
- DIagnostic: CVP, PAC (–> CO, SvO2, central temp), ScvO2 (surrogate for SvO2), cardiac catheter studies, jugular venous bulb sats
- Therapeutic: vaso-irritants (e.g. inotropes, TPN) RRT, TPW, large bore access e.g. PAC sheath, general IV access/multiple infusions
Risks
- Insertion: arrhythmia, misplacement (SC/intrapleural), PTX/HTX, carotid puncture (–> obstruction, dissection, emboli), nerve injury (RLN/vagus), haematoma, thyroid puncture, thoracic duct puncture on left
- Line: infection, thrombosis, air embolism, vessel stenosis, flow obstruction, cardiac tamponade from vessel erosion
Anterior triangle: sternocleidomastoid, mandible imaginary mid-sagittal line
Posterior triangle: sternocleidomastoid, clavicle, trapexius
Interpleural block
- Indications
- Technique
- Risks
Indications
- Surgery: breast, cardiothoracic, upper abdo
- Trauma: multiple rib #
- Pain: acute herpes zoster/post-herpetic neuralgia, cancer pain, chronic pain
Technique: 1L crystalloid with giving set and 3 way tap, pt supine with hand behind head. 16G Tuohy, 4-8th ICS, MAAL. Insert onto rib, remove stylet, attach 3WT, open fluid. Walk off superior rib border. Only advance in expiration. When parietal pleura punctured, fluid will run. Detach fluid and inj LA 20-40ml. Remove needle with fluid running. Can insert catheter.
Risks: PTX, BPF, bronchospasm, infection, catheter misplacement, intrabronchial injection, LA toxicity, IV inj, Horner’s, phrenic nerve palsy, myocardial depression
Laryngoscopy
FNE and cord positions
Larynx*
- Location
- Cartilages
- Muscles
- Nerves
Base of tongue to cricoid cartilage. Musculocartilaginous structure. C3-C6.
Cartilages (3 singles, 3 pairs): epiglottis, cricoid, thyroid (Adam’s apple), arytenoid, corniculate, cuneiform.
Muscles. Extrinsic (3, anchor larynx): sternothyroid, thyrohyoid, inferior pharyngeal constrictors. Intrinsic (6, move vocal cords): posterior cricoarytenoid (abduct), lateral cricoarytenoids and inter-arytenoids (adduct), cricothyroid (tensor), thyroarytenoids and vocalis (relaxors).
Nerves. Vagus divides into SLN and RLN. SLN: sensation above cords (ILN), motor to cricothyroid (ELN). RLN: sensation below cords, motor to all other intrinsic muscles.
Paravertebral space
- Anatomy/boundaries/contents
- Block (Krishnachetty, old Q): indications, technique, risks
PVS = wedge-shaped bilateral potential space lateral to thoracolumbar vertebral column. Communicates with epidural space via intervertebral foramina, and intercostal spaces.
Boundaries
- Anterolateral: pleura and lung (thorax), intercostal space, psoas/sacrospinalis (abdo)
- Medial: vertebral body, intervertebral disc, vertebral foramen
- Posterior: transverse process, costo-transverse ligament (thorax)
- Superior: head of adjacent rib (thorax)
Contents (anterior and posterior compartments): spinal nerve roots, sympathetic chain, vessels, lymph nodes, fat. SNRs give off rami communicantes, then divide into dorsal and ventral branches.
Block
- I: surgery (breast, cardiothoracic, VATS, open chole, hernia, renal), trauma (rib #s), pain (CRPS, ca, post-herpetic neuralgia), sympathetic block for hyperhydrosis
- T: Sitting or lateral. Find spinous process, mark 2.5cm lateral (where transverse process of that VB should be if lumbar, or the one below if thoracic). Blunt tip or Tuohy inserted perpendicular 3-5cm to hit TP. Walk off caudally with LOR syringe and advance 1cm (‘pop’ in thoracic region - costo-transverse ligament). Change rather than loss of resistance. Aspirate and inj 3-5ml. Single shot/multi-level/catheter.
- R: failure, IV inj/LA toxicity, SA/extradural spread, high spinal, PDPH, interpleural/epidural placement, PTX/HTX, Horner’s, haematoma, infection, nerve injury, hypotension if B/L, extension of block to B/L in 10%, Stellate ganglion block in high PVB.
Ascertain extent of surgery beforehand; VATS T3-T8, thoracotomy T2/3-T8/9, mastectomy T1-T6. For multiple dermatomes, multi-level single shot technique e.g. 10ml at T3/5/7.
Advantages over epidural: fewer PDPH, nerve damage, sedation, N&V, reduced CVS effects if unilateral, no motor blockade or bladder disturbance, better RS function. Equivalent analgesia and success rates (95%).
BPF: Most common cause = PPV after thoracotomy –> bronchial stump dehiscence. Occurs 3-10/7 postop. Causes V/Q mismatch. Need flow limitation (LTVV, low PEEP, low RR), sometimes OLV and HFV to aid healing. High mortality. Surgical tx: bronchoscopic sealant application, VATS or open surgical management. Anaesthetise lateral positon, good lung up. TIVA as volatile leak with BPF.
Popliteal fossa
- Nerves
- Block
Nerves
- Tibial: main branch of sciatic. Gives off sural, medial and lateral plantar nerves. Will plantar flex toes and invert foot.
- Common peroneal: divides above pop fossa into superficial and deep. Will dorsiflex toes and evert foot.
Block
Prone awake, or supine/lateral GA. Locate tendons of biceps femoris (lateral) and semitendinosus and semimemranosus (medial). Insertion point is 1cm lateral to where they meet, about 6-8cm above popliteal crease. Insert needle perpendicular until foot stimulated. Aspirate and inj.
Sciatic nerve
- Anatomy/course
- Blocks
Anatomy
Largest nerve in body and main branch of sacral plexus. Anterior primary rami L4-S3. Roots unite on piriformis then exit via greater sciatic foramen as sciatic nerve. Leaves pelvis, enters thigh, passing midway between ischial tuberosity and greater trochanter. Descends in posterior compartment of thigh. Divides 6-10cm above pop. fossa into tibial and common peroneal.
Blocks - anterior (Beck/Meier); parasacral (Mansour); posterior (Labat); inferior (Raj)
Anterior: supine. Two lines: ASIS to PT and parallel below it from greater trochanter to thigh. Junction of middle and medial thirds on line 2 is insertion point. 150mm needle, touch femur, withdraw and angle medially, 2-3cm further (total depth 10-13cm). If pt awake, do femoral block first.
Risks: injury, IV inj/LA toxicity, IN inj/neuronal ischaemia (avoid adrenaline), infection, failure.
Spinal cord blood supply (Krishnachetty, Mendonca, old Q)
Spinal cord: 45cm long, roughly cylindrical, 31 pairs spinal nerves
Ascending tracts: STT, DCs; descending = anything ending in ‘spinal’ e.g. corticospinal, tectospinal, vestibulospinal.
1 x ASA
- Midline, starts at foramen magnum from two branches from vertebral arteries. Supplies anterior 2/3 of spinal cord.
- Ruptured AAA/elective or emergency repair (also dissection, scoliosis surgery, coeliac plexus block) can precipitate ischaemia/infarction (hypotension, atherosclerosis, luminal narrowing, emboli, graft interposition). Loss of motor and spinothalamic function occurs below lesion (DCs preserved).
2 x PSA
- Arise from PICAs. Supply posterior 1/3 (dorsal columns - fasciculus gracilis/cuneatus - vibration, light touch, proprioception). Good collaterals.
Supplemental radicular branches
- 25-40 additional radicular vessels join; cervical (e.g. vertebrals), thoracic (e.g. intercostals), lumbosacral (e.g. iliacs). Main one is artery of Adamkiewicz/radicularis magna. In 80%, this comes off aorta at T9-11 on left. In 15%, arises at T5 so lower cord more reliant on iliac vessels –> prone to cauda equina if these are interrupted.
- Functionally, good horizontal cross-cover but poor vertical overlap –> risk of watershed ischaemia. Most at risk = T3-5 (greatest distance between radicular arteries = greatest watershed effect).
Venous: radicular and spinal veins –> vertebral venous plexus –> azygous –> SVC. Continuous with pelvic veins, basilar sinus in brain, IVC (hence high AP gets transmitted to epidural veins –> higher risk of venous puncture and lower volume of LA needed for epidurals).
Causes of poor blood supply: trauma, AAA rupture, dissection, inflammation, atherosclerosis, cross-clamping. RFs for cord ischaemia in aortic surgery: pre-existing disease (DM, atherosclerosis, renal), larger aneurysm, longer XCT, redo procedure, increased periop hypotension. Strategies: minimise XCT, maintain SCPP (keep MAP up and CSFP down e.g. spinal drain), mild hypothermia, epidural cooling, femorofemoral bypass/DHCA, pharmacological neuroprotection (?epo), spinal cord monitoring. In elective cases, preop anatomical evaluation for location of collaterals.
ASA syndome: loss of motor, pain and temperature below lesion; DCs preserved.
Cross section through spinal cord.
TAP block
- Indications
- Techniques (blind/US)
- Risks
Blind or US guided. T10-L1 spread (T6-11 intercostals, T12 subcostal, ilioinguinal, iliohypogastric). Can also be done subcostally. Plane btwn int oblique and transversus abdominis.
I: open appendicectomy, open chole, laparoscopy, LSCS/Pfannenstiel, other abdo surgery with CI to neuraxial.
T: Blind - triangle of Petit (ASIS, lat dorsi, ext oblique); insert just behind MAL; two pops (int oblique, transversus abdominis); aspirate, inj. US - linear array, horizontal between costal margin and iliac crest, in plane, needle inserted 3-4cm lateral to probe, asp/inj, confirm LA spread. Skin, adipose tissue, ext oblique, int oblique, transversus abdominis.
R: damage to viscera/bowel, vessels, nerves, IV inj, infection, failure.
Hand nerve supply
- Nerves, root/cord origins and areas supplied
- Peripheral blocks U/M/R elbow/wrist
- Ulnar nerve especially
What they supply
- Ulnar: C8-T1, medial cord of BP. Ulnar palmar 1.5 digits and hypothenar eminence. Flexor carpi ulnaris, instrinsic muscles of hand except lateral lumbricals and thenar.
- Median: C6-T1. Medial and lateral cords. Radial palmar 3.5 digits and thenar eminence. Pronator teres, flexor carpi ulnaris, lateral lumbricals and thenar muscles.
- Radial: C5-T1. Posterior cord. Radial back of hand and 3.5 digits except fingertips. Triceps, brachialis, brachioradialis and forearm and hand extensors.
- Musculocutaneous: C5-C7. Lateral cord. Terminates as lateral cutaneous nerve of the forearm. Radial forearm. (Medial cutaneous nerve of the forearm supplies ulnar forearm.)
Blocks
Ulnar: Elbow - medial epicondyle. Wrist - 2cm proximal to crease.
Median: Elbow - medial to brachial artery. Wrist - 2-4cm above wrist crease between FCR and PL tendons.
Radial: Elbow - 1-2cm proximal to elbow crease, between biceps and brachioradialis. Wrist - ring block around radial border.
Course
Radial: continuation of posterior cord. Posterior to axillary and brachial arteries, between heads of triceps, runs around spiral groove of humerus. Runs btwn brachialis and brachioradialis, terminates as radial and posterior interosseus.
Median: crosses brachial artery at mid-humerus to become medial in ACF. Runs on coracobrachialis and brachialis, enters forearm btwn flexor tendons. Runs in carpal tunnel and terminates in medial and lateral branches.
Ulnar: from medial cord. Runs on coracobrachialis, behind medial epicondyle, enters forearm btwn two heads of flexor carpi ulnaris. Initially deep then becomes superficial to flexor retinaculum and terminates into superficial and deep branches over pisiform bone.
Vertebrae and ligaments
Joints between adjacent thoracic vertebrae (4): cartilaginous (intervertebral disc), synovial (facets, costovertebral and costotransverse)
Ligaments between adjacent thoracic vertebrae (8): ant and post longitudinal, ligamenta flava, ligamentum nuchae, interspinous, supraspinous, intertransverse, intervertebral
Nerve supply: intervertebral joint - anterior and posterior plexi. Synovial joints - corresponding spinal nerves.
