ABSTRACT
Victims of severe accidental hypothermia are frequently treated with catecholamines to counteract the hemodynamic instability associated with hypothermia-induced cardiac contractile dysfunction. However, we previously reported that the inotropic effects of epinephrine are diminished after hypothermia and rewarming (H/R) in an intact animal model. Thus, the goal of this study was to investigate the effects of Epi treatment on excitation-contraction coupling in isolated rat cardiomyocytes after H/R. In adult male rats, cardiomyocytes isolated from the left ventricle were electrically stimulated at 0.5 Hz and evoked cytosolic [Ca2+] and contractile responses (sarcomere length shortening) were measured. In initial experiments, the effects of varying concentrations of epinephrine on evoked cytosolic [Ca2+] and contractile responses at 37 °C were measured. In a second series of experiments, cardiomyocytes were cooled from 37 °C to 15 °C, maintained at 15 °C for 2 h, then rewarmed to 37 °C (H/R protocol). Immediately after rewarming, the effects of epinephrine treatment on evoked cytosolic [Ca2+] and contractile responses of cardiomyocytes were determined. At 37 °C, epinephrine treatment increased both cytosolic [Ca2+] and contractile responses of cardiomyocytes in a concentration-dependent manner peaking at 25-50 nM. The evoked contractile response of cardiomyocytes after H/R was reduced while the cytosolic [Ca2+] response was slightly elevated. The diminished contractile response of cardiomyocytes after H/R was not mitigated by epinephrine (25 nM) and epinephrine treatment reduced the exponential time decay constant (Tau), but did not increase the cytosolic [Ca2+] response. We conclude that epinephrine treatment does not mitigate H/R-induced contractile dysfunction in cardiomyocytes.
ABSTRACT
Objective: To study the applicability of on-table extubation (OTE) protocol following congenital cardiac surgery in a low-resource setting and its impact on the length of intensive care unit (ICU) stay, hospital stay, hospitalization cost, parental anxiety, and nurse anxiety. Materials and Methods: In this prospective, nonrandomized, observational single-center study, we included all children above 1 year of age undergoing congenital cardiac surgery. We evaluated them for the feasibility of OTE using a prespecified protocol following separation from cardiopulmonary bypass. The data were prospectively collected on 60 children more than 1 year of age, belonging to the Risk Adjustment for Congenital Heart Surgery 1, 2, 3, and 4 groups and divided into two groups: those who underwent successful OTE and those who were ventilated for any duration postoperatively (30 children in each group). Duration of hospital stay, ICU stay, and total hospital cost were collected. Anxiety levels of the primary caregiver (nurse) in the ICU and the mother were assessed immediately after the arrival of the child in the ICU using the State Trait Anxiety Inventory (STAI). Results: Children who were extubated immediately following congenital cardiac surgery had significantly shorter ICU stay (median 20 [19, 22] h vs. 22 [20, 43] h [P < 0.05]). Patients extubated on table had a significant reduction in hospital cost {median Rs. 161,000 (138,330; 211,900), approximately USD 1970 (P < 0.05)} when compared to children who were ventilated postoperatively {median Rs. 201,422 (151,211; 211,900) , approximately USD 2464}. The anxiety level in mothers was significantly less when their child was extubated in the operating room (STAI 36.5 ± 5.4 vs. 47.4 ± 7.4, P < 0.001). However, for the same subset of patients, anxiety level was significantly higher in the ICU nurse (STAI 46.0 ± 5.6 vs. 37.8 ± 4.1, P < 0.05). Conclusion: OTE following congenital cardiac surgery is associated with a shorter duration of ICU stay and hospital stay. It also reduces the total hospital cost and the anxiety level in mothers of children undergoing congenital heart surgery. However, the primary bedside caregiver during the child's ICU stay had increased anxiety managing patients with OTE.