Timothy Van Natta

Devices for lung isolation used by anesthesiologists with limited thoracic experience: Comparison of double-lumen endotracheal tube, Univent® torque control blocker, and Arndt Wire-guided Endobronchial Blocker®

Background:Lung isolation is accomplished with a double-lumen tube or a bronchial blocker. Previous studies comparing lung isolation methods were performed by experienced anesthesiologists in thoracic anesthesia. Therefore, the results of these studies may not be relevant to the anesthesiologist with limited experience. This study compared the success rates of lung isolation devices among anesthesiologists with limited experience in thoracic anesthesia. Methods:A prospective, randomized trial was designed to determine the success and time required for proper placement of the left-sided double-lumen tube (n = 22), the Univent® tube (Vitaid Ltd., Lewiston, NY; n = 22), and the Arndt Blocker® (Cook Critical Care, Bloomington, IN; n = 22). Anesthesiologists with less than two lung isolation cases per month were included (faculty n = 17 and senior residents n = 11). Variables recorded included (1) successful placement (as determined by an independent observer), (2) time of placement, and (3) the number of times the fiberoptic bronchoscope was used. Results:Participants failed to place or position their assigned device in 25 of 66 patients (failure was 39% among faculty and 36% among senior residents). The failure rate did not differ among the three devices (P = 0.65). The median (25th–75th percentile) times to complete the placement procedures were as follows: (1) double-lumen tube: 6.1 min (4.6–9.5 min), (2) Univent tube: 6.7 min (4.9–8.8 min), and (3) Arndt Blocker: 8.6 min (5.8–17.5 min) (P = 0.45 comparing all devices). After device malposition was identified, it took 1 min or less for the investigating anesthesiologist to achieve optimal position. Conclusions:Anesthesiologists with limited experience in thoracic anesthesia frequently fail to successfully place lung isolation devices. Rapid successful device placement by an experienced anesthesiologist excluded any contribution of uniquely difficult anatomy. The nature of the malpositions suggests that the most critical factor in successful placement was the anesthesiologist’s knowledge of endoscopic bronchial anatomy.

Metabolic Adaptation of the Fetal and Postnatal Ovine Heart: Regulatory Role of Hypoxia-Inducible Factors and Nuclear Respiratory Factor-1

Numerous metabolic adaptations occur in the heart after birth. Important transcription factors that regulate expression of the glycolytic and mitochondrial oxidative genes are hypoxia-inducible factors (HIF-1α and -2α) and nuclear respiratory factor-1 (NRF-1). The goal of this study was to examine expression of HIF-1α, HIF-2α, and NRF-1 and the genes they regulate in pre- and postnatal myocardium. Ovine right and left ventricular myocardium was obtained at four time points: 95 and 140 d gestation (term = 145 d) and 7 d and 8 wk postnatally. Steady-state mRNA and protein levels of HIF-1α and NRF-1 and protein levels of HIF-2α were measured along with mRNA of HIF-1α-regulated genes (aldolase A, α- and β-enolase, lactate dehydrogenase A, liver and muscle phosphofructokinase) and NRF-1-regulated genes (cytochrome c, Va subunit of cytochrome oxidase, and carnitine palmitoyltransferase I ). HIF-1α protein was present in fetal myocardium but dropped below detectable levels at 7 d postnatally. HIF-2α protein levels were similar at the four time points. Steady-state mRNA levels of α-enolase, lactate dehydrogenase A, and liver phosphofructokinase declined significantly postnatally. Aldolase A, β-enolase, and muscle phosphofructokinase mRNA levels increased postnatally. Steady-state mRNA and protein levels of NRF-1 decreased postnatally in contrast to the postnatal increases in cytochrome c, subunit Va of cytochrome oxidase, and carnitine palmitoyltransferase I mRNA levels. The in vivo postnatal regulation of enzymes encoding glycolytic and mitochondrial enzymes is complex. As transactivation response elements for the genes encoding metabolic enzymes continue to be characterized, studies using the fetal-to-postnatal metabolic transition of the heart will continue to help define the in vivo role of these transcription factors.

The modified Konno procedure for complex left ventricular outflow tract obstruction

BACKGROUND Complex left ventricular outflow tract (LVOT) obstruction with normal aortic valve function requires aggressive resection in the subaortic region and preservation of the aortic valve. The modified Konno procedure allows generous exposure of the LVOT from the left ventricular apex to the inter leaflet trigones of the aortic valve. Widespread use of this procedure has been limited by concern over injury to the aortic valve, the conduction system, and possibility of residual ventricular septal defect (VSD). METHODS Retrospective analysis of pertinent data for all patients undergoing the modified Konno procedure (1994 to 2001) at the University of Iowa were reviewed. RESULTS The modified Konno procedure was used in 18 patients (age 1 to 31) for LVOT obstruction associated with diffuse narrowing of the LVOT (n = 7), a discrete fibrous ring (n = 7), or a fibrous ring associated with abnormal mitral attachments (n = 4). Eight patients had previously undergone LVOT resection. There were no perioperative deaths. Estimated LVOT peak gradients by echocardiogram were 70.4 +/- 24.2 mm Hg (preoperative) and 19.2 +/- 20.4 mm Hg (postoperative) at most recent followup (p < 0.001 vs preop). Aortic insufficiency was moderate in one patient (present preop) and mild or less in all other patients. There were no cases of permanent heart block. Small residual VSDs were present in five patients (28%). Median follow-up is 3.1 years. CONCLUSIONS The modified Konno procedure can effectively relieve complex LVOT obstruction and preserve aortic valve function. Extension of this procedure for use in the initial presentation of LVOT may be appropriate in cases at increased risk of recurrent LVOT obstruction.

Myocardial apoptosis after cardioplegic arrest in the neonatal lamb

OBJECTIVE Myocardial apoptosis is observed after various cardiac injuries and is also a normal part of fetal cardiac development and early postnatal maturation. Cardioplegic arrest and reperfusion result in ischemic injury and oxidative stress, known triggers of apoptosis. Because the neonatal heart is in a proapoptotic state, we hypothesize that apoptosis is triggered after cardioplegic arrest in neonatal myocardium. METHODS We started neonatal lambs (6-8 days old, n = 5) on cardiopulmonary bypass and administered cold crystalloid cardioplegia at 20-minute intervals. Total crossclamp time was 70 minutes, and bypass time was 90 minutes. After a six-hour recovery period, the hearts were excised and examined by using TdT-mediated dUTP nick-end labeling; radiolabeled DNA electrophoresis; fluorimetric caspase 3, 8, and 9 activity assay; mRNA microarray; and Western immunoblotting. Control lambs were anesthetized but did not undergo operation (n = 5) or were started on cardiopulmonary bypass for 90 minutes but not arrested (n = 5). RESULTS Lambs subjected to cardioplegia had 5-fold more TdT-mediated dUTP nick-end labeling-positive nuclei compared with that seen in unoperated control animals (P =.007) and bypass-only control animals (P =.008). DNA laddering was present in all postcardioplegia hearts but absent among control hearts. Bad and Bcl-X mRNA transcription increased significantly. Caspase 3, 8, and 9 activities were slightly greater than those seen in control animals, but the differences were not significant. No change was detected in Bcl-2, Bax, or Bcl-xL proteins. CONCLUSIONS In a clinically relevant model of neonatal cardioplegic arrest, increased apoptotic cell death is present 6 hours after reperfusion, and both proapoptotic and antiapoptotic responses are triggered. The clinical implications of apoptosis after cardioplegic arrest remain undetermined.

The modified Konno procedure for complex left ventricular outflow tract obstruction: Invited commentary

Background. Complex left ventricular outflow tract (LVOT) obstruction with normal aortic valve function requires aggressive resection in the subaortic region and preservation of the aortic valve. The modified Konno procedure allows generous exposure of the LVOT from the left ventricular apex to the inter leaflet trigones of the aortic valve. Widespread use of this procedure has been limited by concern over injury to the aortic valve, the conduction system, and possibility of residual ventricular septal defect (VSD). Methods. Retrospective analysis of pertinent data for all patients undergoing the modified Konno procedure (1994 to 2001) at the University of Iowa were reviewed. Results. The modified Konno procedure was used in 18 patients (age 1 to 31) for LVOT obstruction associated with diffuse narrowing of the LVOT (n = 7), a discrete fibrous ring (n = 7), or a fibrous ring associated with abnormal mitral attachments (n = 4). Eight patients had previously undergone LVOT resection. There were no perioperative deaths. Estimated LVOT peak gradients by echocardiogram were 70.4 ± 24.2 mm Hg (preoperative) and 19.2 ± 20.4 mm Hg (postoperative) at most recent followup (p < 0.001 vs preop). Aortic insufficiency was moderate in one patient (present preop) and mild or less in all other patients. There were no cases of permanent heart block. Small residual VSDs were present in five patients (28%). Median follow-up is 3.1 years. Conclusions. The modified Konno procedure can effectively relieve complex LVOT obstruction and preserve aortic valve function. Extension of this procedure for use in the initial presentation of LVOT may be appropriate in cases at increased risk of recurrent LVOT obstruction.