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Upper Extremity Nerve Blocks: Comprehensive Question & Answer

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PART I: BRACHIAL PLEXUS ANATOMY — FOUNDATIONS

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PART II: INTERSCALENE BLOCK

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• Bilateral interscalene blocks — absolutely contraindicated due to bilateral phrenic nerve palsy causing complete diaphragmatic paralysis
• Contralateral phrenic nerve palsy — the ipsilateral phrenic nerve is almost always blocked
• Severe pulmonary disease (e.g., severe COPD or moderate-to-severe obstructive pulmonary disease) — hemidiaphragmatic paresis can result in dyspnea, hypercapnia, and hypoxemia

• Local infection at the injection site
• Severe coagulopathy
• Local anesthetic allergy
• Patient refusal
• Contralateral recurrent laryngeal nerve paralysis (hoarseness/respiratory distress may ensue)
• Obesity — worsens the impact of hemidiaphragmatic paresis

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1. Lower injection volumes (≤5–10 mL vs. traditional 20–30 mL)
2. More distal/caudal injection — targeting just above the clavicle ("low" interscalene)
3. Anterior suprascapular nerve block or superior trunk block — emerging "lung-sparing" alternatives that provide shoulder analgesia with less phrenic involvement
4. Injectate directed to the proximal origin of the suprascapular nerve — reduces neurologic and diaphragmatic side effects

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PART III: SUPRACLAVICULAR BLOCK

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• Elbow surgery
• Forearm surgery
• Hand surgery

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PART IV: INFRACLAVICULAR BLOCK

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• Produces complete brachial plexus anesthesia covering the entire arm, forearm, and hand
• Stable location for catheter placement — the infraclavicular region allows the catheter to be secured away from flexion creases, making it the preferred approach for continuous brachial plexus analgesia
• No arm manipulation necessary (unlike axillary block, which requires abduction)
• The three cords are at a predictable location relative to the axillary artery at this level
• Lower incidence of phrenic nerve block compared to interscalene and supraclavicular approaches

• Deep block — the plexus lies beneath two overlying muscles (pectoralis major and minor), requiring deeper needle insertion
• Steep angles of needle insertion reduce needle tip visibility on ultrasound
• Slower onset than axillary block (see Miller comparison table)
• Less predictable tourniquet tolerance than infraclavicular (though better than axillary)

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• Lateral cord — lateral/superior to the artery (10 o'clock position)
• Posterior cord — directly posterior to the artery (6 o'clock position)
• Medial cord — medial/inferior to the artery (4 o'clock position)

• Reduction in axillary artery diameter during injection
• "U-shaped" distribution of local anesthetic underneath the axillary artery
• Separation of cords from the axillary artery
• "White wall appearance" to the axillary artery (free walls)
• Dark layer underneath the axillary artery on long-axis view

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PART V: AXILLARY BLOCK

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• Elbow, forearm, and hand surgery
• Particularly useful for finger, wrist, and distal forearm procedures

• The superficial location makes it the safest of all brachial plexus block approaches — compressible, no risk of pneumothorax, no phrenic nerve involvement
• Suitable for anticoagulated patients (vessel puncture can be directly compressed)
• No risk of spinal/epidural injection
• Rapid onset

• The musculocutaneous nerve leaves the lateral cord proximal to the axilla and enters the coracobrachialis muscle — it must be blocked separately within the coracobrachialis or at mid-humerus
• The intercostobrachial nerve (T2 — medial upper arm sensation) must be blocked separately for tourniquet tolerance
• Requires arm abduction to 70–90 degrees with elbow flexion — may be difficult in trauma patients or those with painful shoulder/arm
• Fascial septa within the axillary sheath may create separate compartments, reducing reliability of single-injection technique
• Catheter placement is less stable than infraclavicular approach

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• The axillary artery appears as a circular, anechoic, pulsatile structure centrally
• The median nerve lies anterior/superior and medial to the artery (roughly at 12 o'clock / "above" the artery)
• The ulnar nerve lies posterior/inferior and medial to the artery
• The radial nerve lies posterior/inferior and lateral to the artery
• The musculocutaneous nerve is characteristically found within or adjacent to the coracobrachialis muscle, lateral and away from the main neurovascular bundle. It has a characteristic shape change: round when adjacent to the artery → flat inside the coracobrachialis muscle → triangular as it exits the muscle

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• Superior (above) the artery → Median and musculocutaneous nerves (responses: wrist/finger flexion, forearm pronation; elbow flexion for musculocutaneous)
• Inferior (below) the artery → Ulnar and radial nerves (responses: finger adduction/wrist flexion ulnar deviation; wrist/finger extension for radial)

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PART VI: ELBOW BLOCK

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1. Intraneural injection — the nerve may be directly punctured or the injectate may enter the nerve fascicles due to the tight surrounding tissue
2. Pressure injury — the volume of local anesthetic can elevate pressure within the tunnel
3. Risk of post-block ulnar neuropathy

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PART VII: WRIST BLOCK

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PART VIII: FOREARM BLOCKS

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1. Supplement an incomplete brachial plexus block — missed segments can be filled in precisely
2. Selective anesthesia for procedures with a limited field (e.g., a single finger procedure)
3. Avoid complications of proximal blocks — no risk of phrenic nerve palsy, pneumothorax, or Horner syndrome
4. Safer ulnar nerve block — the ulnar nerve can be blocked at the midforearm to avoid the risks of cubital tunnel injection at the elbow
5. Ultrasound feasibility — superficial location makes ultrasound-guided forearm blocks technically easy
6. Reduced systemic LA toxicity risk — smaller volumes needed for peripheral nerve blocks

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• Out-of-plane (OOP): A 30–50 mm insulated needle is inserted perpendicular to the transversely placed probe at a 45–60 degree angle, with the target nerve centered on screen
• In-plane (IP) with medial-to-lateral direction: Useful at the elbow; allows tracking of needle to avoid brachial artery
• After a test dose with D5W (to distinguish intraneural from perineural injection), 5 mL of local anesthetic is deposited circumferentially around the nerve

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• A "hockey stick" (small footprint linear) probe is used for better maneuverability at the distal forearm
• The ideal injection point is where the ulnar nerve is still separate from the ulnar artery (more proximal midforearm), to reduce arterial puncture risk
• In-plane technique with the needle aligned to the small-footprint probe allows tracking of the needle approaching the nerve from the lateral aspect

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• With ultrasound, the nerve is identified as a flat, hypoechoic structure within the coracobrachialis muscle
• Inject 5 mL of local anesthetic directly within the muscle belly around the nerve

• Subcutaneous injection of 5–10 mL in the lateral bicipital groove at mid-humerus anesthetizes the nerve as it traverses between biceps and brachialis

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PART IX: LOCAL ANESTHETIC SELECTION AND DOSING

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• Interscalene: 10–20 mL (as low as 5 mL for phrenic-sparing)
• Supraclavicular: 15–30 mL
• Infraclavicular: 20–35 mL
• Axillary: 10–15 mL per nerve (multiple injections), 30–40 mL total

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PART X: LOCAL ANESTHETIC SYSTEMIC TOXICITY (LAST)

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1. CNS toxicity (earlier onset — lower threshold): perioral numbness, metallic taste, tinnitus, visual disturbances, anxiety → seizures → coma
2. Cardiovascular toxicity (higher doses): arrhythmias, prolonged PR/QRS, hypotension, ventricular fibrillation. Bupivacaine is the most cardiotoxic agent.

• Interscalene/supraclavicular blocks have highest LAST risk due to proximity to carotid and vertebral arteries and high vascularity of the neck. As little as 1 mL of LA into the vertebral artery can cause seizure (Morgan).
• Large volumes required for infraclavicular and axillary blocks also confer risk

• Ultrasound guidance to visualize needle tip
• Incremental injection with frequent aspiration
• Epinephrine test dose (sudden HR increase indicates intravascular injection)
• Use minimum effective volume

1. Stop injection immediately
2. Airway management — 100% O₂, intubate if needed to prevent hypoxia/acidosis (worsens toxicity)
3. Suppress seizure: benzodiazepines preferred (avoid succinylcholine if GABA involvement)
4. Intralipid (lipid emulsion rescue): 20% lipid emulsion — bolus 1.5 mL/kg IV, then infusion 0.25 mL/kg/min; may repeat bolus 1–2x if no improvement
5. ACLS for cardiac arrest; avoid vasopressin, calcium channel blockers, beta blockers
6. Prolonged CPR may be required

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PART XI: ULTRASOUND PRINCIPLES FOR UPPER EXTREMITY BLOCKS

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1. Nerve appearance: Peripheral nerves appear as honeycomb-like or fascicular structures in cross-section (short axis) — a collection of hypoechoic dots (fascicles) surrounded by hyperechoic epineurium. In long axis, nerves appear as hyperechoic parallel lines.
2. Probe frequency:
   • High-frequency probes (10–15 MHz): better resolution, limited depth penetration — ideal for superficial nerves (axillary, forearm, wrist)
   • Lower-frequency probes (5–10 MHz): deeper penetration — needed for infraclavicular block in larger patients
3. Needle visualization:
   • In-plane (IP): Needle enters parallel to the long axis of the probe; the entire needle shaft and tip are visible
   • Out-of-plane (OOP): Needle enters perpendicular to the probe; only a bright dot (cross-section of needle) is seen
   • IP preferred for deep blocks (infraclavicular); OOP acceptable for superficial blocks
4. Hydrodissection: Small amounts of normal saline (or D5W to avoid false-positive NS response) can be used to identify the perineural space before LA injection
5. Color Doppler: Essential for identifying arteries and veins near target nerves before needle advancement
6. Intraneural injection recognition: Nerve swelling (increase in cross-sectional area) during injection indicates intraneural deposition — stop immediately

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PART XII: SPECIAL SITUATIONS AND ADVANCED TOPICS

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1. Superior trunk block: Local anesthetic is deposited selectively at the superior trunk of the brachial plexus at a site just distal to where the phrenic nerve branches from the C5 root. This provides shoulder analgesia via suprascapular and axillary nerves while minimizing phrenic involvement.
2. Anterior suprascapular nerve block: The suprascapular nerve is blocked as it passes deep to the omohyoid muscle (anterior approach) or in the supraspinous fossa (posterior approach). The suprascapular nerve provides approximately 70% of shoulder joint innervation. Used with an axillary nerve block for the lateral shoulder, it can replace ISB.
3. Costocervical trunk block / selective C5 root block
4. Low-volume ISB (≤5 mL): Reduces (but does not eliminate) phrenic nerve block.

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• Postoperative shoulder analgesia (especially when ISB is contraindicated due to pulmonary risk)
• Combined with infraclavicular or axillary nerve block to provide shoulder analgesia while avoiding phrenic nerve block
• Chronic shoulder pain management

• Anterior approach: Identify the nerve deep to the omohyoid muscle in the posterior triangle; inject 5–10 mL
• Posterior approach: Patient in sitting/lateral position; identify the nerve in the supraspinous fossa; inject 5–10 mL

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• Significantly reduce opioid consumption
• Superior analgesia vs. single-shot blocks for major limb surgery
• Can be managed at home with portable infusion pumps (ambulatory catheter program)

• Stable anatomical location away from flexion points
• Low risk of catheter displacement
• High catheter success rate (Miller Table 42.2 shows "High" for infraclavicular vs. "Low" for axillary)

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• Tourniquet pain (limits use beyond 60–90 minutes)
• Loss of block is immediate on tourniquet release (unlike peripheral nerve blocks)
• Risk of LAST if tourniquet deflates prematurely
• Cannot be used for digit or wrist procedures (requires double cuff above the elbow)
• Bupivacaine is absolutely contraindicated for Bier block (fatal cardiac arrests reported)

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SUMMARY TABLE

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Upper Extremity Regional Blocks: Comprehensive Q&A

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PART I — BRACHIAL PLEXUS ANATOMY

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PART II — INTERSCALENE BLOCK

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• Absolute: Bilateral interscalene blocks (bilateral phrenic palsy → apnea); contralateral phrenic nerve palsy; severe pulmonary disease (e.g., moderate-to-severe COPD) — hemidiaphragmatic paresis can cause dyspnea, hypercapnia, and hypoxemia; local anesthetic allergy; local infection; patient refusal
• Relative: Contralateral vocal cord paralysis (recurrent laryngeal nerve block → respiratory distress); coagulopathy; obesity (worsens diaphragmatic impact)

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1. Reduce volume to ≤5–10 mL (US-guided)
2. Anterior suprascapular nerve block — targets the suprascapular nerve at the omohyoid for shoulder analgesia without significant phrenic involvement
3. Superior trunk block — selective deposition at the superior trunk distal to phrenic nerve origin
4. Low interscalene block (just above clavicle, below C6)

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PART III — SUPRACLAVICULAR BLOCK

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PART IV — INFRACLAVICULAR BLOCK

• Complete brachial plexus anesthesia
• Stable catheter location — the infraclavicular region is the optimal approach for continuous peripheral nerve catheters
• No arm manipulation required
• Low phrenic nerve risk (below the level of phrenic nerve origin)
• The cords are at predictable positions relative to the axillary artery

• Deep block — beneath pectoralis major and minor; steep needle angles reduce tip visibility
• Slower onset than axillary block
• Requires either probe manipulation or steep needle angulation

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• Lateral cord → 10 o'clock (lateral/superior to artery)
• Posterior cord → 6 o'clock (directly posterior)
• Medial cord → 4 o'clock (medial/inferior)

• Reduction in axillary artery diameter during injection
• "U-shaped" LA distribution underneath the artery
• Separation of cords from the axillary artery
• "White wall" appearance to the artery (free walls)
• Dark layer underneath the artery on long-axis view

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PART V — AXILLARY BLOCK

• Safest brachial plexus approach — superficial, compressible, no phrenic nerve risk, no pneumothorax
• Suitable for anticoagulated patients
• No risk of spinal/epidural injection

• Musculocutaneous nerve has already left the axillary sheath proximal to the axilla → must be blocked separately
• Intercostobrachial nerve (T2 — medial upper arm) must be blocked separately for tourniquet tolerance
• Requires arm abduction to 70–90° with elbow flexion — not possible in severe trauma or frozen shoulder
• Fascial septa within the axillary sheath create separate compartments → single injection is unreliable → multi-injection technique required
• Low catheter success rate vs. infraclavicular

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• Median nerve — anterior/superior (12 o'clock)
• Ulnar nerve — posterior-inferior and medial
• Radial nerve — posterior-inferior and lateral
• Musculocutaneous nerve — within or adjacent to the coracobrachialis muscle lateral to the bundle. Characteristic shape: round when adjacent to artery → flat inside coracobrachialis → triangular on exit. Must be identified and injected separately.

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• Above artery → Median (wrist/finger flexion, pronation) and musculocutaneous (elbow flexion)
• Below artery → Ulnar (ring/little finger flexion, ulnar wrist deviation) and radial (wrist/finger extension)

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PART VI — ELBOW BLOCK

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1. Intraneural injection — fascicles may be directly entered in the confined space
2. Elevated tunnel pressure — local anesthetic volume cannot decompress
3. Post-block ulnar neuropathy (weakness, clawing, sensory loss in little/ring finger)

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PART VII — WRIST BLOCK

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• Insert needle just radial to the PL tendon at the proximal wrist crease
• Depth ~3–5 mm
• Inject 3–5 mL after negative aspiration
• Avoid epinephrine (end-artery territory of digital vessels)

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• Insert needle just medial to the pulsating ulnar artery, lateral to FCU
• Inject 3–5 mL after careful aspiration (ulnar artery is immediately adjacent)
• US Doppler is valuable to avoid arterial puncture

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• 3–5 mL deposited subcutaneously in a band across the dorsal wrist from the radial artery to the dorsum
• At the level of the radial styloid

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PART VIII — FOREARM BLOCKS

1. Supplement an incomplete brachial plexus block — targeted rescue of missed segments
2. Selective anesthesia for limited-field procedures (single digit)
3. Avoid proximal block complications — no phrenic nerve palsy, pneumothorax, or Horner syndrome
4. Safest ulnar nerve approach — midforearm avoids cubital tunnel pressure injury risk
5. Technically easy with US — all nerves are superficial (<2 cm)
6. Smaller LA volumes — lower LAST risk

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• OOP: Needle perpendicular at 45–60°; center nerve on screen
• IP (medial-to-lateral) at elbow: Allows tracking to avoid brachial artery

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• "Hockey stick" small-footprint linear probe preferred at the distal forearm
• Inject at the most proximal point where the nerve is still clearly separate from the ulnar artery
• IP technique with needle aligned to the probe, approaching laterally
• Volume: 5 mL; circumferential spread; avoid arterial puncture

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• US: flat hypoechoic nerve within the coracobrachialis muscle; inject 5 mL directly within the muscle belly

• Subcutaneous injection of 5–10 mL in the lateral bicipital groove anesthetizes the nerve between biceps and brachialis

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PART IX — LOCAL ANESTHETIC SELECTION AND DOSING

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PART X — TOXICITY AND SAFETY

1. Stop injection immediately
2. Airway — 100% O₂, intubation if needed (hypoxia/acidosis worsen toxicity)
3. Benzodiazepines for seizure suppression
4. Lipid emulsion rescue (Intralipid 20%): Bolus 1.5 mL/kg IV → infusion 0.25 mL/kg/min; repeat bolus 1–2× if no improvement
5. ACLS for cardiac arrest; avoid vasopressin, calcium channel blockers, beta-blockers
6. Prolonged CPR may be required

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PART XI — ULTRASOUND PRINCIPLES

1. Nerve appearance: In short axis — honeycomb pattern (hypoechoic fascicles in hyperechoic epineurium). In long axis — parallel hyperechoic lines.
2. Frequency: 10–15 MHz for superficial nerves (axillary, forearm, wrist); lower for deep blocks (infraclavicular in obese).
3. In-plane (IP): Full needle visibility — preferred for deep or high-risk blocks.
4. Out-of-plane (OOP): Only needle cross-section visible — acceptable for superficial blocks.
5. Color Doppler: Identify adjacent vessels before needle advancement.
6. D5W hydrodissection: Identifies perineural space without interfering with NS response.
7. Intraneural injection sign: Nerve cross-sectional area increases during injection → stop immediately.

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PART XII — ADVANCED TOPICS

1. Superior trunk block — LA deposited at superior trunk distal to C5's phrenic contribution; provides shoulder analgesia via suprascapular and axillary nerves
2. Anterior suprascapular nerve block — at the omohyoid; blocks ~70% of shoulder joint afferents
3. Low-volume ISB (≤5 mL) — reduces but does not eliminate phrenic block
4. Combined suprascapular + axillary nerve block — covers shoulder without phrenic nerve

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• Anterior approach: Deep to omohyoid in posterior triangle; 5–10 mL
• Posterior approach: In supraspinous fossa; patient sitting/lateral; 5–10 mL

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MASTER SUMMARY TABLE

Anaesthetic Management of the Diabetic Patient

Comprehensive Q&A from Miller's Anesthesia 10e & Barash Clinical Anesthesia 9e

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SECTION A — FOUNDATIONS: DIABETES AND ANAESTHESIA

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• Macrovascular: Coronary artery disease, hypertension, cerebrovascular disease, peripheral vascular disease
• Microvascular: Retinopathy, nephropathy, neuropathy (peripheral and autonomic)
• Other: Stiff joint syndrome, gastroparesis, increased infection risk, poor wound healing

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1. Type 1 diabetes — Immune-mediated β-cell destruction; absolute insulin deficiency
2. Type 2 diabetes — Progressive insulin resistance with variable secretory defect; accounts for the great majority of diabetics
3. Secondary diabetes — Due to glucocorticoids, HIV medications, post-transplant immunosuppressants, chronic pancreatitis/pancreatectomy, or monogenic syndromes (maturity-onset diabetes of the young — MODY)
4. Gestational diabetes (GDM) — Diagnosed during second or third trimester in a previously non-diabetic patient; highly relevant for the LSCS scenario

• Diabetics (especially insulin-requiring) are categorised as "elevated risk" for perioperative cardiac events under the 2014 ACC/AHA Guidelines — Barash p. 4046

• Target HbA1c for Type 1 DM: <8% (ADA) — delay elective surgery if above
• Target HbA1c for Type 2 DM: <7% (ADA) — delay elective surgery if above
• If HbA1c is above target range, elective surgery should be postponed for optimisation — Barash p. 4062

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• Predominantly Type 1 DM (also SGLT-2 inhibitor-associated euglycaemic DKA in Type 2)
• Blood glucose: 250–400 mg/dL (moderate elevation)
• Ketonemia: elevated β-hydroxybutyrate, acetoacetate, acetone
• Metabolic acidosis with increased anion gap
• Volume deficit: approximately 2–4 L
• pH: <7.3 (usually); HCO₃: <18 mEq/L

• Predominantly Type 2 DM, older patients
• Blood glucose: 600–1000 mg/dL (markedly elevated)
• No ketosis (sufficient residual insulin to prevent lipolysis)
• No significant acidosis
• Volume deficit: 6–10 L (much greater than DKA)
• Osmolality: markedly elevated
• Mortality: 10–20% (Barash) vs. DKA mortality ~1–5% (Miller gives DKA mortality 5%, HHS mortality 10–20%)
• Coma, seizures, intravascular thrombosis due to hyperviscosity

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• SGLT-2 inhibitors must be discontinued 3–4 days before surgical procedures to prevent ketoacidosis
• These patients may have DKA with a blood glucose that appears deceptively normal — check ketones

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SECTION B — SCENARIO 1: 40-YEAR-OLD DIABETIC FOR SHOULDER SURGERY UNDER GENERAL ANAESTHESIA

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1. History

• Type of diabetes (Type 1 vs Type 2) and duration
• Current diabetes medications: Insulin regimen (type, dose, timing), OHAs (particularly metformin and SGLT-2 inhibitors)
• Glycaemic control history: Frequency and severity of hypoglycaemic episodes; level at which symptoms occur; hypoglycaemic unawareness?
• HbA1c: Most recent value and trend
• Insulin pump users: Pump type, basal rate, insulin-to-carbohydrate ratio, correction factor, glucose targets

2. Systemic Review for Diabetic Complications

• History of CAD, MI, angina, heart failure, hypertension
• ECG: silent ischemia (common due to autonomic neuropathy — diabetics may have no symptoms)
• Echocardiogram if symptomatic or abnormal ECG

• Orthostatic hypotension, resting tachycardia, exercise intolerance
• Gastroparesis — nausea, vomiting, early satiety, bloating → aspiration risk even after adequate fasting
• Decreased hypoxia-induced ventilatory drive
• Baroreceptor insensitivity → haemodynamic lability during anaesthesia

• Pre-existing neurological deficits — must be documented before any regional technique or positioning
• Vascular disease → increased susceptibility to positioning injuries

• Creatinine, eGFR, urine albumin/creatinine ratio — diabetic nephropathy → contrast precautions, drug dose adjustments
• Microalbuminuria rises logarithmically at HbA1c >8% — Miller p. 4587

• Stiff joint syndrome — glycosylation of proteins + abnormal collagen cross-linking → reduced mobility of temporomandibular joint, atlanto-occipital joint, and cervical spine → difficult intubation
• Particularly in longstanding Type 1 DM; incidence of difficult intubation 20–30% in some series (Barash)
• "Prayer sign": Inability to completely oppose palmar surfaces of interphalangeal joints — traditionally associated with stiff joint syndrome and difficult laryngoscopy. Miller (p. 4591) notes this has been refuted as a predictor of difficult laryngoscopy but Barash (p. 2841) states it may predict difficult laryngoscopy in up to 40% of juvenile DM patients presenting for renal transplantation
• Thorough airway exam mandatory before induction for all diabetic patients

3. Preoperative Laboratory Investigations

• Blood glucose (on arrival and 1-hourly if delayed)
• HbA1c (target: Type 1 <8%, Type 2 <7%)
• Serum electrolytes (K⁺ critical — OHAs and DKA affect potassium)
• Creatinine and eGFR
• ECG (12-lead — screen for silent ischaemia)
• Urinalysis/urine dipstick — ketonuria, proteinuria
• Fasting lipid profile if not recent (for cardiovascular risk)

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Oral Hypoglycaemic Agents

Insulin Regimens on Day of Surgery

• Never withhold ALL insulin → risk of DKA
• Evening before surgery: Continue usual dose of short-acting insulin with the evening meal; reduce intermediate/long-acting by 20%
• Morning of surgery: Omit morning short-acting insulin; reduce intermediate-acting by 50% or long-acting by 20% (give only if fasting glucose >120 mg/dL — Barash p. 2850)
• Maintain a 5% dextrose infusion at 75–125 mL/hour to prevent hypoglycaemia while fasting

• Hold oral agents; manage with insulin infusion or basal long-acting insulin + regular insulin sliding scale (RISS)
• A RISS as the sole method of control is discouraged (Barash p. 2990) — risk of wide glucose fluctuations

• Continue pump intraoperatively with basal rate reduced by 20–25%
• Check blood glucose every hour if pump is continued during surgery — Barash p. 2850

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1. Schedule as the first case of the day — to minimise fasting duration (Barash p. 4080)
2. Patient arrives in early morning — blood glucose checked on arrival and every hour if the case is delayed
3. If hypoglycaemia develops during waiting: Give glucose tablet or clear juice (oral) if no IV; IV glucose-containing fluid if IV is in place
4. Coordinate preoperative optimisation with the patient's endocrinologist 1–2 weeks before elective surgery (Barash p. 4060)
5. Type 1 diabetics should be first case to minimise the risk of DKA from prolonged fasting

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A. Airway Management

• Thorough airway evaluation for stiff joint syndrome — reduced TM joint and atlanto-occipital mobility
• Use the prayer sign as part of the preoperative airway assessment
• Prepare for potential difficult intubation: Have fibreoptic equipment, video laryngoscope, and airway trolley available
• Patients with acromegaly (associated with DM) have 20–30% incidence of difficult intubation

B. Aspiration Risk

• Gastroparesis from autonomic neuropathy → delayed gastric emptying → residual gastric contents even after adequate fasting
• Increase index of suspicion; consider RSI (rapid sequence induction) if gastroparesis is confirmed
• GLP-1 receptor agonists further delay gastric emptying — particularly risky if recently started
• Consider premedication with metoclopramide, H₂-blocker or PPI, and sodium citrate

C. Positioning: Beach Chair or Lateral Decubitus

• Shoulder surgery is most commonly performed in the beach chair position (sitting/semi-recumbent)
• Haemodynamic implications for the diabetic:
  • Autonomic neuropathy → orthostatic hypotension — diabetics are at heightened risk of severe hypotension in the upright position, which may worsen silent cardiac ischaemia
  • Cerebral hypoperfusion — cerebral perfusion pressure = MAP minus head height; in the upright position, for every 1 cm above the heart, MAP at the brain is ~0.77 mmHg less. Diabetics with cerebrovascular disease are particularly vulnerable
  • Maintain MAP ≥65–80 mmHg; consider measuring BP at the level of the external auditory meatus as a surrogate for cerebral perfusion

D. Cardiovascular Management

• Diabetics are at elevated ACC/AHA risk — have ECG and consider stress testing if multiple risk factors
• Increased incidence of silent myocardial ischaemia (autonomic neuropathy blunts pain perception)
• Consider initiating beta-blockers preoperatively if ≥2 cardiac risk factors (Barash p. 4062) — no evidence beta-blockers worsen glucose intolerance or mask hypoglycaemic symptoms
• Intraoperative ST-segment monitoring (V5 + II leads optimal)

E. Haemodynamic Lability

• Diabetic autonomic neuropathy impairs baroreceptor sensitivity and hypoxia-driven ventilatory drive
• Expect exaggerated hypotension at induction and haemodynamic swings during the case
• Use smaller, incremental induction doses; have vasopressors ready (phenylephrine preferred in beach chair to avoid excessive tachycardia from ephedrine)

F. Peripheral Neuropathy and Positioning

• Document all pre-existing neurological deficits before positioning
• Diabetics are more susceptible to peripheral nerve and pressure injuries — careful padding of all pressure points
• Vascular disease increases tissue ischaemia risk from compression

G. Renal Considerations

• Adjust drug doses for renal impairment (nephropathy common)
• Avoid nephrotoxic agents; cautious hydration

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Monitoring Protocol

• Check blood glucose on arrival to the anaesthetic room
• Check every 1–2 hours intraoperatively (Barash p. 4086, 4098)
• For major/long surgery: consider continuous glucose monitoring (CGM) device — approved for hospital use since COVID-19 pandemic (Barash p. 2977)

Glucose Measurement Methods and Accuracy (Barash p. 2976)

Insulin Administration Strategy

• For short, non-invasive outpatient procedures in well-controlled diabetics: Subcutaneous sliding scale alone may suffice
• For longer or major surgery: IV regular insulin infusion is preferred over subcutaneous or long-acting insulin (Barash p. 4098)
  • Separate IV insulin infusion + separate IV glucose infusion (not combined GIK) — more easily adjusted
  • Insulin infusion via side-port of glucose infusion line (for safety)
  • A separate non-glucose isotonic solution (e.g., normal saline) is used for fluid replacement and loss compensation
• IV regular insulin (Barash Table 47-12): Onset 15 min, peak 15–30 min, duration 0.5–1 hour — ideal for titration
• Sliding scale insulin (RISS) as sole method is discouraged — leads to wide glucose fluctuations (Barash p. 2990)

Glucose Targets Intraoperatively

• Aim: 140–180 mg/dL (ADA/NICE-SUGAR-derived consensus)
• Avoid hypoglycaemia (glucose <70 mg/dL) — symptomatic sweating, tachycardia, confusion under GA may be masked
• Treat hypoglycaemia promptly with IV dextrose 50% (25 mL = 12.5 g glucose) or 10% dextrose infusion

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Standard ASA/Routine Monitors

• ECG (5-lead if available; V5 + Lead II for optimal ischaemia detection)
• Pulse oximetry (SpO₂)
• Non-invasive blood pressure (NIBP) — consider invasive arterial line for:
  • Significant autonomic neuropathy
  • Established CAD or suspected silent ischaemia
  • Beach chair positioning with high risk of cerebral hypoperfusion
• Capnography (EtCO₂) — mandatory for GA with intubation
• Temperature monitoring — diabetics prone to hypothermia (peripheral vascular disease, autonomic neuropathy impairs thermoregulation)
• Peripheral nerve stimulator (TOF monitor) — for neuromuscular blockade monitoring (stiff joint syndrome → difficult airway; be sure of reversal before extubation)
• Depth of anaesthesia monitoring (BIS/Entropy) — particularly relevant in the sitting position where awareness risk may be higher

Specific Diabetic Monitoring

• Blood glucose: every 1–2 hours (Barash; Miller)
• Intraoperative urine output — diabetics have impaired renal autoregulation; maintain >0.5 mL/kg/hour
• Intra-arterial line — enables beat-to-beat BP measurement in beach chair position + frequent blood sampling for glucose

Postoperative Monitoring (PACU)

• Blood glucose on arrival to PACU and repeated every 1–2 hours
• Observe for hypoglycaemia — masked in post-anaesthesia recovery
• Watch for silent myocardial ischaemia — post-op ECG if concerned
• PONV prophylaxis (critical in Type 1 DM — early resumption of diet and insulin is essential) — use multimodal prophylaxis (dexamethasone + ondansetron ± scopolamine patch)

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Induction

• Propofol or thiopental — no significant direct effect on glucose; propofol has mild anti-oxidant properties
• Consider modified RSI if gastroparesis/aspiration risk — preoxygenation, cricoid pressure, use of succinylcholine (if no contraindications) or high-dose rocuronium + sugammadex reversal plan
• Ketamine causes catecholamine release → hyperglycaemia; avoid or minimise in diabetics with poor glycaemic control

Maintenance

• Volatile anaesthetics (sevoflurane, desflurane): All potentiate peripheral glucose tolerance impairment to variable degrees; sevoflurane may have some cardioprotective preconditioning properties
• TIVA with propofol + remifentanil/fentanyl: Offers haemodynamic stability, less nausea, precise control — advantageous in diabetics
• Nitrous oxide: Can be used but increases PONV risk — problematic in gastroparetic diabetics; use judicious

Muscle Relaxation

• Rocuronium or vecuronium — standard; renal clearance of vecuronium is prolonged in significant nephropathy → prefer atracurium/cisatracurium (Hofmann elimination) if renal impairment
• Monitor NMB with TOF watch — critical; do not extubate without confirmed reversal (stiff joint → potential difficult re-intubation if airway lost)

Fluid Management

• Use balanced crystalloids (Hartmann's/PlasmaLyte) rather than saline if large volumes anticipated — saline → hyperchloraemic acidosis which can obscure DKA assessment
• Glucose-containing fluids only as part of glucose management protocol — not as routine IV fluid
• Avoid dextrose infusions in euglycaemic patients (risk of hyperglycaemia)

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1. Resume oral intake as early as possible → allows transition back to oral glucose-lowering regimen
2. Glucose monitoring continues in PACU and ward — 4-hourly on ward for stable patient; every 1–2 hours if labile
3. PONV prophylaxis with multimodal agents — PONV in a Type 1 diabetic delays oral intake and insulin resumption, risking DKA
4. Wound healing: Diabetics have impaired neutrophil function, reactive oxygen species overproduction, and vascular disease → increased infection risk; strict asepsis, glycaemic control
5. Restart medications: Oral agents resumed once patient is eating. Metformin is restarted only once renal function is confirmed adequate. SGLT-2 inhibitors can be restarted after wound has healed and patient is eating normally.
6. Consider multimodal analgesia — regional nerve blocks reduce stress response (↓ cortisol, catecholamines → less hyperglycaemia); NSAIDs with caution in diabetic nephropathy; paracetamol safe
7. Interscalene block (ISB) as part of shoulder surgery anaesthesia: If used as an adjunct or sole technique, monitor for autonomic effects (Horner syndrome, phrenic nerve palsy) — particularly important since diabetics may already have compromised respiratory reserve

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SECTION C — SCENARIO 2: 30-YEAR-OLD DIABETIC FOR LSCS (LOWER SEGMENT CAESAREAN SECTION)

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1. Pre-existing Type 1 DM — absolute insulin deficiency; autoimmune
2. Pre-existing Type 2 DM — insulin resistance ± secretory defect; often obesity-related
3. Gestational Diabetes Mellitus (GDM) — diabetes first diagnosed during second or third trimester; the most common form in pregnancy; usually resolves postpartum but increases lifetime risk of Type 2 DM
4. Secondary diabetes — steroid-induced (e.g., betamethasone given for fetal lung maturity), pancreatic disease

• 1-hour 50g glucose challenge test (GCT): if ≥140 mg/dL → 3-hour 100g OGTT for confirmation
• Or: Fasting glucose ≥92 mg/dL, 1-hour ≥180, 2-hour ≥153 on 75g OGTT (IADPSG criteria)
• Risk factors: Age >25, obesity, family history of DM, prior macrosomic baby, polycystic ovary syndrome

• Pre-existing DM carries higher risk of established end-organ disease (neuropathy, nephropathy, retinopathy, CAD)
• GDM typically has fewer end-organ complications but introduces:
  • Macrosomia (fetal overgrowth) → obstructed labour → LSCS
  • Pre-eclampsia and hypertension risk
  • Neonatal hypoglycaemia (neonatal team must be present)
  • Polyhydramnios → aspiration risk

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• Placental hormones (HPL, progesterone, cortisol, prolactin) → peripheral insulin resistance
• Insulin requirements rise progressively through pregnancy (especially in the 2nd–3rd trimester)
• Impaired fasting glucose is normal in pregnancy due to increased peripheral glucose uptake by fetus and placenta

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History

• Urgency of LSCS (Category I–IV): Urgency governs the choice between spinal, epidural, and GA
• Type of diabetes, duration, current glycaemic control
• Current medications: Insulin type and doses; metformin (last dose?); SGLT-2 inhibitors (if any — must have been discontinued 3–4 days before); GLP-1 agonists (aspiration risk)
• Obstetric history: Gestational age; antenatal complications; fetal well-being; placenta position
• Pre-eclampsia (complicates 15–20% of diabetic pregnancies) → affects anaesthetic choice (thrombocytopenia → contraindication to regional block?)

Systematic Review for End-Organ Disease

• Cardiovascular: Silent ischaemia, hypertension (superimposed pre-eclampsia in DM patients)
• Renal: Diabetic nephropathy + pre-eclampsia (superimposed) — check proteinuria, creatinine
• Neurological: Peripheral neuropathy → document before regional block
• Airway: Stiff joint syndrome (longstanding T1DM) + pregnancy-related oropharyngeal oedema → combined difficult airway

Laboratory Investigations

• Blood glucose on arrival and 1-hourly (more frequently if unwell)
• HbA1c
• FBC — platelet count (pre-eclampsia → thrombocytopenia; minimum platelet count for neuraxial block: 70,000–100,000/mm³ depending on institutional policy)
• Coagulation (PT, APTT) if pre-eclampsia or on LMWH
• Renal function (creatinine, uric acid — uric acid elevated in pre-eclampsia)
• LFTs (HELLP syndrome screen if severe pre-eclampsia)
• Group and screen / crossmatch (obstetric haemorrhage risk)
• ECG (if pre-existing DM with cardiac risk factors)

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Preferred Technique: SPINAL ANAESTHESIA

1. Avoids the risks of GA in a potentially difficult airway (pregnancy + diabetic stiff joint syndrome)
2. Avoids aspiration risk — these patients are "full stomach" even after fasting (gastric stasis from autonomic neuropathy)
3. Lower stress response vs. GA → better glycaemic control (less catecholamine/cortisol surge)
4. Neonatal benefits — avoids foetal exposure to GA agents
5. Superior postoperative analgesia — intrathecal opioids (morphine 100–200 µg, fentanyl 10–25 µg) provide prolonged analgesia
6. Conscious patient — facilitates immediate maternal–neonatal bonding

• Heavy bupivacaine 0.5%: 1.5–2.0 mL (typically 10–12 mg)
• Intrathecal fentanyl 10–25 µg — onset analgesia
• Intrathecal morphine 100–200 µg — prolonged postoperative analgesia (4–18 hours)
• Block level required: T4 (nipple line) for complete LSCS anaesthesia

When Epidural is Preferred

• If labour epidural is already in-situ → epidural top-up for LSCS
• Non-urgent LSCS where gradual onset of block is preferred
• Allows titration in haemodynamically unstable patients

When Combined Spinal-Epidural (CSE) is Used

• Ultra-low-dose spinal supplemented by epidural if surgery is prolonged
• Allows top-up if spinal inadequate without repeat spinal

When GA is Required

• Category I (crash) LSCS when there is no time for neuraxial block
• Contraindications to neuraxial block: Thrombocytopenia (<70,000), coagulopathy, patient refusal, raised ICP, local infection, severe uncorrected hypovolaemia
• Failed or inadequate spinal/epidural

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• Pregnancy alone: failed intubation rate ~1:300 (vs. 1:2,000 in general surgery)
• Diabetic stiff joint syndrome compounds this → among the highest-risk airways in anaesthesia
• Must have:
  • Fibreoptic laryngoscope + video laryngoscope immediately available
  • Declare difficult airway before induction
  • Consider awake fibreoptic intubation if airway exam is very concerning
  • Follow DAS (Difficult Airway Society) obstetric failed intubation algorithm

• Highest-risk scenario: diabetic gastroparesis + pregnant (↓ LOS tone, ↑ gastric pressure)
• Rapid Sequence Induction (RSI) is mandatory for GA in all obstetric patients
• Preoxygenation (100% O₂ for ≥3 minutes or 8 vital capacity breaths)
• Cricoid pressure (Sellick manoeuvre) applied until intubation confirmed
• IV sodium citrate 30 mL (oral) given ≤30 min before induction (neutralises gastric acid)
• IV ranitidine 150 mg or pantoprazole the night before and morning of LSCS
• IV metoclopramide 10 mg — prokinetic; promotes gastric emptying, reduces aspiration risk; also important as antiemetic

• RSI with induction doses followed by volatile agent; thiopental (5–7 mg/kg) or propofol (2–2.5 mg/kg) as induction agent
• Use of BIS monitoring to detect awareness

• All GA agents cross the placenta → neonatal sedation/respiratory depression
• Minimise the induction-delivery (I-D) interval — ideally <8 minutes
• Neonatal resuscitation team must be present in room

• Physiological response to laryngoscopy + intubation (catecholamine surge) → acute hyperglycaemia
• Stress hormones from surgery (cortisol, glucagon, catecholamines) → perioperative hyperglycaemia
• Monitor glucose from arrival; use IV insulin protocol

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1. Autonomic neuropathy → impaired compensatory baroreceptor reflexes → deeper and more prolonged hypotension
2. Pre-existing hypertension (common in DM) → acute BP drop may cause more profound organ hypoperfusion
3. Uteroplacental insufficiency → foetal distress if uterine blood flow drops

• Left uterine displacement (15°) — relieves aortocaval compression
• Preloading or co-loading with crystalloid (1 litre of Hartmann's rapidly given before or during spinal injection)
• Colloid co-load is more effective than crystalloid preload for maintaining BP
• Vasopressors:
  • Phenylephrine (alpha-agonist): Now the first-line vasopressor for spinal hypotension in obstetrics — maintains maternal BP and uteroplacental blood flow, prevents reflex tachycardia. Particularly advantageous in diabetics with autonomic neuropathy (already have resting tachycardia — phenylephrine does not add to it)
  • Ephedrine (mixed alpha + beta): Previously first-line; now second-line. Stimulates beta-receptors → crosses placenta → may cause fetal tachycardia and acidosis; stimulates glucogenolysis → hyperglycaemia in the diabetic
  • Noradrenaline (norepinephrine): Emerging data support use; may be better than phenylephrine in patients with underlying bradycardia
• Prophylactic vasopressor infusion: Phenylephrine infusion (50–100 µg/min) from the moment of spinal injection is now standard in many obstetric units

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Preoperative

• Check blood glucose on arrival (ideally fasting 4–6 hours before elective LSCS)
• Target glucose: 70–140 mg/dL for the parturient (tighter than non-pregnant surgical patients to prevent neonatal hypoglycaemia — a neonate exposed to maternal hyperglycaemia secretes excess insulin and becomes hypoglycaemic after delivery)
• Schedule LSCS as first case — minimise fasting duration
• Type 1 DM: Give half to two-thirds of usual intermediate insulin subcutaneously on the morning of surgery (never omit all insulin entirely)
• Type 2 DM on OHAs: Withhold all oral agents; manage with insulin infusion
• If blood glucose >140 mg/dL → start IV regular insulin infusion before proceeding

Intraoperative

• Monitor blood glucose every 30–60 minutes (more frequent than for non-obstetric cases — neonatal hypoglycaemia is the key concern)
• Maintain glucose 70–140 mg/dL throughout
• Run 5% dextrose at 100 mL/hour as a background infusion with a separate insulin infusion titrated to glucose
• Avoid glucose boluses (rapid glucose elevation → neonatal hyperinsulinism → neonatal hypoglycaemia after cord clamping)
• Lactated Ringer's (Hartmann's) solution for volume replacement (contains 28 mmol/L lactate which does not cause clinically significant hyperglycaemia)

Post-Delivery

• After placental delivery: insulin requirements drop dramatically (placental diabetogenic hormones removed)
• Risk of hypoglycaemia is highest in the immediate post-delivery period
• Reduce insulin infusion after cord clamping
• Monitor glucose every 1–2 hours in PACU and postoperative ward

Neonatal Team

• Neonatal hypoglycaemia is common (especially macrosomic infants of poorly controlled DM mothers)
• Neonatal resuscitation team must be present in the delivery room
• Early breastfeeding + glucose monitoring of the neonate

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Maternal Monitoring

Foetal/Neonatal Monitoring

• Intraoperative FHR (foetal heart rate) monitoring if available
• APGAR scores at 1 and 5 minutes
• Neonatal blood glucose within 30 minutes of birth and serially thereafter

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Multimodal Analgesia Approach

• Provides 4–18 hours of excellent postoperative analgesia
• Reduces opioid requirements → less sedation, earlier mobilisation, earlier breastfeeding
• Side effects: pruritus (treat with naloxone 0.04 mg IV or ondansetron), nausea/vomiting, delayed respiratory depression (risk up to 18 hours — observe regularly)
• Requires 12–24 hours of regular respiratory monitoring

• Highly effective multimodal component
• Caution in diabetic nephropathy — NSAIDs are relatively contraindicated (nephrotoxic); use paracetamol and tramadol instead if eGFR is impaired

• Bilateral TAP blocks at the end of LSCS provide somatic analgesia to the abdominal wall
• Particularly useful as an adjunct or if intrathecal morphine was not given
• Reduces postoperative morphine requirements

• Critical in the diabetic parturient — nausea and vomiting delay resumption of oral intake and insulin
• Ondansetron 4 mg IV; dexamethasone 4–8 mg IV (note: dexamethasone causes hyperglycaemia — monitor glucose carefully and cover with insulin); transdermal scopolamine patch

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KEY TABLES

Insulin Pharmacology (Barash Table 47-12)

Perioperative Glucose Targets Summary

Diabetic Complications Checklist for Preoperative Assessment

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