Respiratory functions during epidural and spinal anesthesia

Abstract

Relationship between respiratory functions and the upper limit of the spinal cord anesthelized by epidural (157 cases) or spinal (77 cases) anesthesia was studied in 234 patients (age: 13.68 years) who underwent surgery in the abdomen or lower limb. Respiratory functions were measured with a spirometer (Minato-Ikagaku auto-spiro 500) before and after anesthesia. The following results were obtained.1) Vital capacity (VC): VC did not change if the upper limit remained lower than the T7 spinal segment. As the upper limit ascended segment from T7 to C8 in epidural anesthesia, VC was linearly decreased. Decrease rate per spinal segment was 2.8%. At the level of C8, VC decreased to 70.9%. In spinal anesthesia, VC linearly decreased as the upper limit ascended from T9 to C8. The decrease rate per spinal segment was 3.9%. At the level of C8, VC decreased to 59.1%.2) Inspiratory reserve volume (IRV): In epidural anesthesia, IRV began to drop when the upper limit reached the T7 and then decreased linearly as the upper limit ascended to the higher level of the spinal segment. Decrease rate per spinal segment was 3.5%. At the level of C8, IRV decreased to 69.6%. In spinal anesthesia, IRV also began to decrease at the level of T7 and then continued to decrease linearly as the upper limit ascended. The decrease rate per spinal segment was 4.6%. At the level of C8, IRV decreased to 56.4%.3) Expiratory reserve volume (ERV): In epidural anesthesia, ERV began to decrease when the upper limit reached T8. When the upper limit ascended beyond T5, decrease of ERV was remarkable. At the level of C8, ERV was 55.6%. In spinal anesthesia, ERV remarkably decreased at the levels higher than the T8. At the level of C8, ERV was 48.5%.4) Tidal volume (TV) and %FEV, were almost unchanged in both epidural and spinal anesthesia.5) Respiratory gas flow factors had a general tendency to decrease in both epidural and spinal anesthesia, although their time courses varied considerably.6) Analysis of the arterial blood gases indicated no significant changes in PaO2, PaCO2 and pH in both epidural and spinal anesthesia.