Kinetics of acid-base parameters in conventional hemodialysis

Details about the acid-base changes in hemodialysis are scarce in the literature but are potentially relevant to adequate management of patients. We addressed the acid-base kinetics during hemodialysis and throughout the interdialytic period in a cross-sectional study of adults undergoing conventional hemodialysis. Samples for blood gas analysis were obtained from the arterial limb of the arteriovenous fistula before the first session of the week (HD1), immediately at the end of HD1, and on sequential collections at 15, 30, 45, 60, and 120 min post-HD1. Additional blood samples were collected after ∼20 h following the end of the first dialysis and immediately prior to the initiation of the second dialysis of the week. Thirty adult patients were analyzed (55±15 years, 50% men, 23% diabetic; dialysis vintage 69±53 months). Mean serum bicarbonate levels increased at the end of HD1 (22.3±2.7 mEq/L vs 17.5±2.3 mEq/L, P<0.001) and remained stable until 20 h after the end of the session. The mean values of pCO2 before HD1 were below reference and at 60 and 120 min post-HD1 were significantly lower than at the start (31.3±2.7 mmHg and 30.9±3.7 mmHg vs 34.3±4.1 mmHg, P=0.041 and P=0.010, respectively). The only point of collection in which mean values of pCO2 were above 35 mmHg was 20 h post-dialysis. Serum bicarbonate levels remained stable for at least 20 h after the dialysis sessions, a finding that may have therapeutic implications. During dialysis, the respiratory response for correction of metabolic acidosis (i.e., pCO2 elevation) was impaired.

Eficacia da espirometria de incentivo na prevencao de complicacoes pulmonares apos cirurgias toracicas e abdominais - revisao de literatura / Incentive spirometry effectiveness following thoracic and abdominal surgeries: a literature review

O objetivo deste trabalho foi fazer uma revisao da literatura sobre a eficacia da espirometria de incentivo na prevencao de complicacoes pulmonares, que ainda sao a principal causa de morbidade e mortalidade apos cirurgias toracicas e abdominais. Alteracos na hematose, na mecanica respiratoria, nos volumes e nas capacidades pulmonares ocorrem apos cirurgia, tornando-se maximas, de 48 a 72 horas apos o periodo operatorio. Evidencias na literatura indicam que um padrao respiratorio superficial, sem inspiracoes profundas, e o principal fator que leva a essas alteracoes. O espirometro de incentivo e um recurso terapeutico largamenteutilizado na pratica clinica para induzir a inspiracao maxima sustentada, na tentativa de prevenir ou reverter colapso alveolar, reduzindo, assim, a incidencia de complicacoes pulmonares pos-operatorias. Entretanto, ha controversias quanto a sua eficacia. Varios estudos foram realizados para avaliar sua eficacia ou compara-lo a outras formas de tratamento na profilaxia de complicacoes pulmonares pos-operatorias. Na maioria dos estudos nao foi encontrada diferenca significativa na incidencia dessas complicacoes ao comparar o espirometro de incentivo a outras terapias, mas esse recurso tem sido considerado mais eficaz do que qualquer outra forma de terapia respiratoria. Estudos futuros que avaliem aspectos como influencia da supervisao, adesao ao tratamento, posicao corporal e custo beneficio poderao contribuir para elucidar a eficacia dos espirometros de incentivo