Anesthesia

HPV is a unique, intrinsic, locally-mediated pulmonary vascular reflex - opposite of systemic circulation where hypoxia causes vasodilation. By diverting flow away from poorly-ventilated alveoli, HPV optimizes V/Q matching and is the single most important mechanism limiting hypoxemia during OLV.

Alveolar hypoxia (primary trigger) -> sensed by pulmonary vascular smooth muscle cells themselves -> inhibition of Kv channels -> depolarization -> Ca2+ influx/release -> smooth muscle contraction -> vasoconstriction of small pulmonary arterioles -> blood diverted to better-ventilated regions.

• Site: pre-capillary arterioles (200-500 um), not larger conducting arteries
• Biphasic: immediate phase (minutes) + sustained phase (hours)
• Regional/local, functions independently in each segment - persists in denervated/transplanted lungs
• Can reduce flow to a hypoxic region by up to 50%

• Hypoxemia is the principal concern - non-ventilated lung still gets ~20-30% CO as shunt
• V/Q mismatch: non-dependent lung becomes a pure shunt unit
• Time course: HPV reduces non-ventilated lung flow from ~40% to ~20-25% within 20-30 minutes

State HPV is local/intrinsic (persists in denervated lungs). List 4-5 blunting factors with mechanism and connect back to OLV hypoxemia troubleshooting.

LAST occurs because LAs block voltage-gated Na+ channels non-selectively - at sufficient systemic concentration they block CNS and cardiac Na+ channels. Bupivacaine is disproportionately cardiotoxic due to ""fast-in, slow-out"" kinetics; CNS toxicity classically precedes cardiac toxicity except with bupivacaine.

• Primary: Na+ channel blockade in excitable tissue at toxic systemic concentrations
• CNS: preferentially blocks inhibitory interneurons first -> excitatory phase -> then global depression
• Cardiac: slows phase 0 depolarization -> conduction slowing -> re-entrant arrhythmias; bupivacaine also inhibits mitochondrial fatty acid metabolism
• ""Fast-in, slow-out"" (bupivacaine): rapid binding during systole, slow dissociation during diastole -> cumulative use-dependent block at normal heart rates -> disproportionate cardiotoxicity

Bupivacaine cardiac arrest is classically refractory to standard ACLS - lipid emulsion is a specific antidote; prolonged resuscitation (up to an hour+) may succeed.

Concurrent measures: stop injecting LA, call for help, get lipid kit; 100% O2; benzodiazepines for seizures (avoid propofol if unstable); reduce initial epinephrine to <=1 mcg/kg, avoid vasopressin/CCBs/beta-blockers, amiodarone preferred for VT; prepare for prolonged resuscitation (>1h), consider CPB early; monitor 4-6h post-event (2h if CNS-only).

Quote the lipid protocol exactly (1.5 mL/kg bolus, 0.25 mL/kg/min infusion, max 12 mL/kg). Mention 40-60% atypical presentations and reduced epinephrine dosing.

This patient combines two independent high-risk factors: severe systolic heart failure (EF 25%) requiring meticulous hemodynamic management, and a CIED requiring EMI mitigation, especially with monopolar electrocautery near the upper abdomen. Manage both simultaneously.

Cardiac optimization: assess NYHA class/recent decompensation; review recent echo; continue beta-blockers, hold ACE-I/ARB morning of surgery; correct K+/Mg2+; ECG, BNP/troponin baseline; involve high-risk team early given urgent status.

Anesthetic technique: GA typically required (open surgery). Goal: hemodynamic stability, avoid myocardial depression - slow titrated induction with etomidate or careful low-dose propofol, high-dose opioid. Avoid ketamine if active ischemia a concern. Maintenance: low-dose volatile + opioid, or careful TIVA. Avoid both tachycardia/excess afterload and excessive bradycardia/hypotension.

• ICU/HDU admission for continuous monitoring
• Device re-interrogation by cardiology - confirm function, restore original settings
• Judicious fluid management, inotropic support if needed (dobutamine/milrinone)
• Multimodal analgesia (rectus sheath/TAP blocks) to minimize opioid/sympathetic swings
• Resume cardiac medications as tolerated; monitor for arrhythmia/ischemia/decompensation

Structure the answer around the two parallel risk domains (cardiomyopathy + CIED/EMI). State the surgical-site rule (above umbilicus = higher EMI risk) and mention external pacing/defib availability.

BCIS results from embolic phenomena (fat, marrow, cement, air forced into venous circulation during pressurization/insertion) plus the direct vasoactive/cardiodepressant effects of circulating methylmethacrylate monomer - spectrum from transient hypoxemia to catastrophic collapse, most dramatic at cementing/insertion.

Reaming + cement pressurization -> marrow fat, debris, air, monomer forced into venous sinusoids -> embolization to lungs -> (1) mechanical obstruction -> raised PVR -> acute RV strain -> (2) complement/histamine release -> further vasoconstriction/bronchoconstriction -> (3) monomer -> peripheral vasodilation + direct myocardial depression -> combined hypoxemia + hypotension +/- arrest.

Highest-risk moments: femoral canal reaming/broaching, cement insertion, prosthesis insertion, joint reduction.

1. Immediate recognition via temporal correlation with cementation

2. FiO2 100% immediately

3. IV fluid bolus + vasopressors (phenylephrine/noradrenaline) for hypotension; inotropes if RV dysfunction dominates

4. Communicate with surgeon, may pause the step

5. Treat as acute PE/RV strain physiologically; TEE if available

6. Full ACLS/CPR if Grade 3; prolonged resuscitation may be needed

7. Postoperative ICU monitoring, serial reassessment

State Donaldson's grading with exact numeric thresholds. Identify femoral canal venting and lavage as the two most effective preventive interventions; distinguish prevention from treatment clearly.

Severe thrombocytopenia (45,000/mm3) raises concern for spinal/epidural hematoma with neuraxial technique, while GA carries its own severe risks in pre-eclampsia (exaggerated pressor response, difficult airway, magnesium-NMB interaction). Fetal distress adds time pressure.

Decision in this case: with platelets at 45,000, most protocols favor GA due to unacceptable hematoma risk, despite GA's own risks - unless recent reliable coagulation profile supports individualized regional decision.

Target SBP <160, DBP <110 mmHg; avoid overly aggressive correction to preserve uteroplacental perfusion.

Treatment of toxicity: stop infusion, calcium gluconate 1g (10mL 10%) IV antidote, supportive ventilation.

PPH: oxytocin infusion first-line (slow, avoid bolus hypotension); avoid ergometrine (hypertensive effect); carboprost with caution; anticipate platelet transfusion need; escalate atony management per standard ladder.

Explicitly justify the GA-vs-regional choice using the given platelet count. Quote the magnesium toxicity staged levels with numbers and the calcium gluconate dose exactly.

Pheochromocytoma anesthesia swings from hypertensive crisis (induction, tumor handling, pneumoperitoneum) to potentially severe hypotension after venous ligation removes the catecholamine source. Adequate preoperative alpha-blockade is the single most important determinant of stability.

Beta-blockade added only AFTER adequate alpha-blockade (never start beta first - unopposed alpha stimulation -> crisis). Liberal volume/salt expansion preoperatively blunts post-excision hypotension.

High-risk triggers: laryngoscopy/intubation, pneumoperitoneum insufflation, direct tumor manipulation (highest risk), positioning changes.

Invasive arterial line before induction; central venous access; continuous ECG; communicate with surgeon before high-risk manipulation.

1. Anticipate - advance warning from surgeon, vasopressors drawn up

2. Volume loading before/during this phase

3. Stop/reduce vasodilator infusions immediately

4. Vasopressors: noradrenaline/phenylephrine first-line; vasopressin if refractory

5. Hydrocortisone if bilateral adrenalectomy

6. Monitor glucose closely (rebound hyperinsulinemia -> hypoglycemia)

7. Continue ICU monitoring 24-48h postoperatively

Quote Roizen's criteria by number - the single most commonly tested fact here. Structure the answer around the three hemodynamic phases and always mention post-excision hypoglycemia.

Pediatric FB aspiration anesthesia is unique because the surgeon and anesthesiologist share the airway - the goal is to maintain spontaneous ventilation wherever possible, avoiding positive-pressure ventilation that could push the object distally or cause ball-valve air-trapping/pneumothorax.

1. Inhalational induction with sevoflurane in 100% O2

2. Avoid muscle relaxants initially

3. Deepen with additional volatile +/- topical lidocaine (<=4-5 mg/kg max)

4. Shared airway technique via rigid bronchoscope side-port

5. TIVA (propofol +/- remifentanil) increasingly favored as alternative to volatile through an open scope

6. Continuous communication with surgeon, brief interruptions for oxygenation between attempts

7. Be prepared to advance the object past carina to one side if complete obstruction threatens

SpO2/ETCO2 (often intermittent given open airway); watch for sudden desaturation, laryngospasm, or pneumothorax; have chest drain kit ready.

Postop: watch for post-obstructive pulmonary edema, laryngeal/subglottic edema (nebulized adrenaline/dexamethasone if stridor), residual fragments, aspiration pneumonitis.

Explain WHY spontaneous ventilation is preserved (ball-valve mechanism) rather than just stating it as a rule. Mention TIVA as a modern alternative to volatile through an open bronchoscope.

The sitting position offers excellent surgical access but creates a unique hazard: non-collapsible dural venous sinuses held open by bone/fibrous attachments sit at the highest point of the field, often above the right atrium - creating a negative pressure gradient that can entrain air directly into venous circulation.

Preop: echocardiography for PFO (~25-30% prevalence - if present, sitting position often avoided); assess cardiovascular reserve; cervical spine assessment.

Positioning: gradual staged elevation; lower extremity compression; minimum 2-finger chin-to-sternum distance; pad all pressure points.

Open dural sinus/large vein above right atrium -> held open by surrounding bone (non-collapsible) -> negative pressure gradient -> atmospheric air entrained -> travels to right heart -> (1) air lock/mechanical outflow obstruction, (2) diffuse pulmonary microvascular obstruction, (3) if PFO present, paradoxical air embolism -> stroke/coronary air embolism.

Incidence reported as high as 25-40% with sensitive monitoring, though most episodes are small-volume.

Quote the sensitivity-ranked detection list with precordial Doppler at the top. Explain WHY dural sinuses are vulnerable (non-collapsible, held open by bone). Name Durant's maneuver specifically.

RALP combines two independently stressful insults that compound each other: pneumoperitoneum (raised intra-abdominal pressure, CO2 absorption) and steep Trendelenburg (30-45 deg head-down for hours) - causing cephalad fluid shift, raised ICP/IOP, reduced pulmonary compliance, and altered cerebral autoregulation.

• Increased IOP from elevated episcleral venous pressure and choroidal congestion, worsens with duration
• Postoperative visual loss (POVL) - rare but devastating, mainly ischemic optic neuropathy from prolonged positioning, venous congestion, relative hypotension, anemia, prolonged duration
• Conjunctival/periorbital edema (chemosis) - usually self-limiting
• Prevention: minimize angle/duration, avoid excessive crystalloid, maintain hemoglobin, careful eye protection/padding

• Reduced FRC/compliance from cephalad viscera and diaphragm displacement
• Increased peak/plateau pressures - pressure-controlled ventilation often preferred
• Atelectasis in dependent regions - recruitment + PEEP balanced against hemodynamic/ICP effects
• Risk of endobronchial intubation from cephalad mediastinal shift - re-auscultate after final positioning
• CO2 absorption requires increased minute ventilation; rare capnothorax/subcutaneous emphysema

• Cerebral autoregulation generally preserved but hypercapnia (vasodilator) + venous congestion can push CBV/ICP higher
• Airway/facial edema may warrant cuff-leak test or delayed extubation after prolonged cases
• Relative contraindications: pre-existing raised ICP, cerebrovascular disease, severe cardiopulmonary disease, glaucoma

Controlled pressure-limited ventilation with titrated PEEP; invasive arterial monitoring for prolonged/high-risk cases; judicious/restrictive fluid management; maintain hemoglobin; meticulous eye protection; minimize total steep time; gradual return to supine with hemodynamic monitoring.

Structure the answer explicitly across ocular, respiratory, and cerebrovascular systems as demanded. Name ischemic optic neuropathy specifically and mention the role of fluid restriction.

The ARDS lung is functionally a ""baby lung"" - only a fraction of normal-sized lung tissue remains aerated/compliant. Ventilating this small volume with conventional tidal volumes causes VILI via volutrauma, barotrauma, atelectrauma, and biotrauma - driving low tidal volume, adequate PEEP, and prone positioning strategy.

• ARDSNet target: Vt 4-8 mL/kg (commonly start 6 mL/kg) of predicted/ideal body weight (PBW), NOT actual body weight
• Why PBW: lung size correlates with height/sex, not fat/edema-related weight
• IBW formula: Male = 50 + 0.91x(height cm - 152.4); Female = 45.5 + 0.91x(height cm - 152.4)
• Plateau pressure target <30 cmH2O (some evidence supports <=27-28 when feasible)
• Permissive hypercapnia accepted (pH tolerated to 7.20-7.25) - caution with raised ICP/RV dysfunction

PEEP: maintains recruitment, prevents atelectrauma. Higher PEEP favored in moderate-severe ARDS (P/F<200) per patient-level meta-analyses. Titration via ARDSNet tables, best-compliance, esophageal pressure, or decremental trials.

NMB: early short-course (~48h) infusion considered in P/F<150. ACURASYS (2010) suggested mortality benefit; ROSE (2019) found no difference with light sedation + as-needed NMB - current practice is individualized, not routine.

Indications: P/F<150 on PEEP>=5 and FiO2>=0.6 despite optimization (PROSEVA criteria). Initiate early (24-48h), sessions >=16 h/day.

Contraindications: unstable spine fracture, raised ICP, recent open abdomen, hemodynamic instability, late pregnancy.

Write out the exact IBW formula. Mention driving pressure with the Amato 2015 reference and >15 cmH2O threshold. Show awareness of the ACURASYS vs ROSE NMB evidence evolution.