『Echo to Anesthesia Map 13』のカバーアート

Echo to Anesthesia Map 13

Echo to Anesthesia Map 13

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 A Basic-Science–Integrated, Clinical-Anesthesia–Focused Chapter

A 41-year-old male with end-stage renal disease (ESRD), thrice-weekly dialysis, hemoglobin 9 g/dL, post-dialysis potassium 5–6 mmol/L, creatinine 8–9 mg/dL, and urea 110–150 mg/dL undergoes preoperative echocardiographic assessment before renal transplantation. He demonstrates classical uremic cardiac remodeling: severe LV hypertrophy, diastolic dysfunction, pulmonary hypertension, and right heart dilation.

The purpose of this chapter is to integrate echo findings → physiology → physics → anatomy → anesthesia strategy, forming a complete, mechanistic, clinically relevant approach.

1. CARDIAC ANATOMY AND PATHOPHYSIOLOGY RELEVANT TO THIS PATIENTLEFT VENTRICULAR ANATOMY: THE THICK-WALLED PRESSURE PUMP

The LV has:

  • Thick muscular myocardium (especially septum and posterior wall)

  • Helico-spiral fiber orientation, allowing torsion and recoil

  • A relatively small cavity in severe concentric LVH


Severe LVH in ESRD: What the Echo Shows

  • IVSd = 20 mm, PWd = 18 mm
    (Normal: ~9–11 mm)


This is pathological concentric hypertrophy with significantly altered chamber compliance.

Physics of a Hypertrophied LV:

Laplace’s Law (Wall Stress = (Pressure × Radius) / (2 × Wall Thickness))

  • When wall thickness increases, wall stress drops.

  • The LV adapts to chronic hypertension by thickening its walls to reduce wall stress.


But this comes at a cost:

  • Reduced compliance

  • Higher diastolic pressures

  • More oxygen consumption

  • More dependence on slow filling


This fundamentally changes anesthetic goals:

A hypertrophied LV can generate pressure but cannot accept volume.

RIGHT VENTRICULAR ANATOMY: THE THIN-WALLED VOLUME PUMP

The RV has:

  • Thin free wall

  • Crescent-shaped geometry

  • Greater sensitivity to afterload than preload


In this patient:

  • RV dilated

  • TR Grade II

  • RVSP = 57 + RAP mmHg
    → Moderate–severe pulmonary hypertension


Physics and Physiology:

RV afterload is primarily determined by PVR (pulmonary vascular resistance).
PVR ∝ (Mean PAP – LAP) / CO

Any increase in:

  • Hypoxia

  • Hypercarbia

  • Acidosis

  • High PEEP
    → increases PVR → RV failure.


ATRIAL ANATOMY AND FILLING PHYSIOLOGYDilated LA + RA = high chronic filling pressures

  • Reflects diastolic dysfunction and volume overload

  • LA contraction becomes essential for LV filling


Importance of Sinus Rhythm

In Grade II diastolic dysfunction:

  • Up to 40% of LV stroke volume is dependent on atrial contraction
    Loss of atrial kick (AF, junctional rhythm) = sudden drop in CO.


2. ECHO FINDINGS TRANSITIONED INTO BASIC-SCIENCE MECHANISMSA. Severe Concentric LVH → Physics + PathophysiologyStiffness (compliance) curve

The LV pressure-volume relationship becomes:

  • Steep early diastolic slope

  • Small increase in volume → large increase in pressure
    (Physics: ∂P/∂V greatly increased)


Clinical anesthesia relevance:
Small fluid boluses → FLASH PULMONARY EDEMA.

B....
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