PubMed · 5900084
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1965. Respiratory failure.. https://pubmed.ncbi.nlm.nih.gov/5900084/
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OBJECTIVES: Hypertrophied myocardium is more sensitive to ischaemic dysfunction and damage. The objective of this study was to determine the effect of respiratory acidosis on cardiac muscle function following hypoxia-induced right ventricular hypertrophy, and to ascertain the role of Na(+)-H+ antiporter, which is known to be associated with cell growth. METHODS: Wistar rats were maintained at 10% O2 for 1 or 4 weeks. Experiments were performed on right ventricular papillary muscles stimulated at 1 Hz, and developed tension was recorded. The effect of respiratory acidosis was examined by equilibrating the perfusing solution with increasing levels of CO2, and the role of the Na(+)-H+ antiporter was determined by preincubation with the inhibitor 5-(N,N-hexamethylene) amiloride (HMA). Data were analysed by comparison of the slope of the semi-log plot of normalised tension against pH. RESULTS: Right ventricular hypertrophy was apparent after both 1 and 4 weeks of hypoxia. Respiratory acidosis reduced developed force in preparations from all groups, but the relationship between log tension and pH in the 4-week hypoxia group was less steep than in controls (4-week hypoxia 0.736 (0.057); control 0.947 (0.067); P < 0.01). In the 1-week hypoxia group however the relationship was steeper (1.243 (0.090); P < 0.01). HMA increased the slope in all groups, and under these conditions the control and 4-week hypoxia groups were not significantly different (control 1.134 (0.080); 4-week hypoxic 1.083 (0.087); P > 0.05). CONCLUSIONS: The increased resistance to respiratory acidosis of hypertrophied cardiac muscle following 4 weeks of hypoxia was abolished by HMA. This implies that it is related to increased activity of the Na(+)-H+ antiporter. The mechanism underlying the decreased resistance to acidosis following 1 week of hypoxia is unclear, but is unlikely to involve the Na(+)-H+ antiporter.
Laparoscopic surgery has been termed minimally invasive surgery by advocates of this technology. It has been demonstrated previously that using carbon dioxide for insufflation produces a respiratory acidosis due to transperitoneal absorption of gas. Insufflation with helium does not create this acidosis. We questioned whether laparoscopic surgery would elicit a stress response and whether the absence of acidosis with helium might prevent or reduce the levels of stress hormones. Sixteen female patients undergoing laparoscopic cholecystectomy were randomly assigned to helium (n = 8) or CO2 (n = 8) insufflation. Serum cortisol, epinephrine, and norepinephrine were measured preoperatively, after induction of anesthesia but before insufflation, at 45 min of surgery, and after desufflation. There were increases in epinephrine, norepinephrine, plasma cortisol, and urine cortisol at 45 min and at the conclusion of the procedure over the preoperative value. With ANOVA, each variable showed significant increases from preoperative values, at 45 min, and at the end of the case. Except for the increased epinephrine when helium was used, there were no significant differences in the other variables between helium and CO2. Laparoscopic cholecystectomy produces significant increases in stress hormone levels. Prevention of acidosis with helium insufflation does not appear to protect against increases in stress hormones. Epinephrine levels with helium insufflation are higher than with CO2, and elevations in stress hormones suggest that laparoscopic cholecystectomy is not physiologically minimally invasive.
Early tracheal extubation in the operating room after atrial septal defect (ASD) surgery was recommended as part of a clinical practice guideline (CPG) established in the Cardiovascular Program at the Children's Hospital, Boston, MA. This retrospective review was undertaken to determine whether this practice was efficient without compromising patient care. The charts and hospital charges for 102 patients undergoing secundum ASD or sinus venosus defect surgery between March 1992 and July 1994 were reviewed; 36 patients (Group I) had surgery prior to introduction of the CPG, and 66 patients were managed according to the CPG. Of the latter, 25 patients (Group II) were tracheally extubated in the operating room (OR) and 41 patients (Group III) were extubated in the cardiac intensive care unit (CICU). Patients in all three groups were similar with respect to height, weight, and surgical conditions including cardiopulmonary bypass time, lowest esophageal temperature, hematocrit, total OR time, and the time from completion of bypass to leaving the OR. Patients in Group II received significantly less fentanyl during anesthesia, were more likely to have a respiratory acidosis on admission to the CICU, and had an increased frequency of vomiting in the CICU. There was no difference in duration of CICU stay among groups. The length of hospital stay was reduced in Groups II and III after introduction of the CPGs, but was not influenced by tracheal extubation in the OR. There was no difference among groups in the hospital charges for OR, anesthesia and CICU time. However, when the combined hospital charges for services provided both in the OR and CICU were included, patients in Group II were charged significantly less, and this primarily reflects the absence of postoperative mechanical ventilation charges. Tracheal extubation in the OR after ASD surgery in children can result in lower patient charges without significantly compromising patient care.