Robert K. Crone

Congenital diaphragmatic hernia: Arterial structural changes and persistent pulmonary hypertension after surgical repair

Some infants with congenital diaphragmatic hernia who die after surgical correction have a transient postoperative period during which systemic oxygenation is adequate (honeymoon period), whereas others have persistent hypoxemia. Using morphometric techniques, we analyzed lung structure, especially the arterial bed, in seven infants who died within 1 week of surgical repair. Three infants comprised the honeymoon group, the PaO2 transiently being greater than 150 mm Hg in the descending aorta (FiO2 1.0); four infants comprised the no-honeymoon group and never had PaO2 greater than 85 mm Hg. All lungs were hypoplastic for age; with one exception, infants in the no-honeymoon group had smaller lungs. Arterial structure in the no-honeymoon group contributed to a greater reduction in pulmonary arterial cross-sectional area. Each infant in the no-honeymoon group had muscularization of intra-acinar arteries and failure of perinatal increase in compliance of small preacinar arteries, features not seen in the honeymoon group or in the normal newborn infant. In addition, compared with the honeymoon group, luminal area of preacinar and intra-acinar arteries in the no-honeymoon group was decreased by reduced external diameter or increased medial thickness. Clinical deterioration in the honeymoon group is based on a vasoconstrictive response of the hypoplastic vascular bed. Persistent hypoxemia in the no-honeymoon group is based on both severity of pulmonary hypoplasia and structural remodeling of the pulmonary arteries.

Health impact assessment and short-term medical missions: A methods study to evaluate quality of care

BackgroundShort-term medical missions (STMMs) are a well-established means of providing health care to the developing world. Despite over 250 million dollars and thousands of volunteer hours dedicated to STMMs, there is a lack of standardized evaluation to assess patient safety, quality control, and mission impact. The objective of this project is to design and implement an assessment tool that defines objective parameters of quality of care as identified by STMMs.MethodsThe study was conducted in 3 phases: 1) Base-need analysis to determine factors critical to the quality of STMMs, 2) Design of 5 surveys for mission personnel and patients to enable 360-degree evaluation based on factors from phase 1, and 3) Field testing of the surveys with 5 STMMs.ResultsAn evaluation tool was created assessing 6 major and 30 minor factors identified as important to the quality of STMMs. 5 mission directors, 43 personnel, 10 local hosts, and 55 patients completed the surveys. Of the 6 major measures of quality, missions performed best in Cost (mean score 86%), and Impact (84%). The poorest performance was in Education (64%). Efficiency, Sustainability, and Preparedness showed mean scores of 76%, 77%, and 73%, respectively.ConclusionOur study provides a novel standardized tool for STMM evaluation. Use of the assessment instrument identified areas of strength and weakness of a particular mission, and delineated general trends in performance compared to other STMMs. We anticipate that the use of this tool may improve the quality of care provided by missions, and stimulate solution-sharing and scholarly discussion among missions.

Inappropriate secretion of antidiuretic hormone in a postsurgical pediatric population

Twenty-four pediatric patients undergoing corrective posterior spinal fusion surgery for idiopathic scoliosis were studied to determine the frequency with which the syndrome of inappropriate antidiuretic hormone secretion (SIADH) developed. We measured arterial blood gases, serum and urine electrolytes and osmolalities, CVP, and urine output during and after surgery. The 20 patients receiving hypotonic iv salt solution in the immediate postoperative period experienced a significant drop in serum sodium values (6.2 ± 2.9 mEq/L) and 5 (25%) developed SIADH as diagnosed by routine laboratory procedures. Four patients were treated with iv isotonic salt solution. No patient developed hyponatremia (serum Na+ <130 mEq/L) and the decrease in serum sodium (3.0 ± 0.8 mEq/L) was not statistically significant. We conclude that SIADH occurs commonly in patients undergoing corrective vertebral surgery and that vigilant attention must be paid to their fluid and electrolyte management in the postoperative period.

Halothane in status asthmaticus.

The authors administered halothane anesthesia to treat a child with status asthmaticus that was refractory to conventional pharmacological therapy and mechanical ventilation. Halothane is an inhalation anesthetic with potent bronchodilator properties. Marked improvement in gas exchange occurred in this patient after 10 min of treatment with halothane. The pharmacology of halothane is reviewed and a possible role for its use in childhood asthma is proposed.

The effect of extracorporeal membrane oxygenation on the survival of neonates with high-risk congenital diaphragmatic hernia: 45 cases from a single institution.

At The Childrens Hospital, Boston (TCH), in the 3 years before extracorporeal membrane oxygenation (ECMO) was available, infants with high-risk congenital diaphragmatic hernia (CDH) had a 47% survival rate. In February 1984, ECMO was introduced and offered to all high-risk CDH infants with a 100% predicted mortality. Since February 1984, 45 infants with high-risk CDH presented to TCH. Twenty-six (58%) were supported with ECMO; 19 (42%) never met the criteria for 100% predicted mortality and were supported with conventional mechanical ventilation (CMV). Overall survival was 49%. Nine (35%) of the 26 ECMO patients survived. Thirteen (68%) of the 19 CMV patients survived. Although there was no change in survival, there was a change in the cause of death. Deaths in the ECMO group were either early (n = 8, secondary to a complication of ECMO or lack of pulmonary improvement) or late (n = 9). The late deaths were infants who were successfully weaned from ECMO, never weaned from CMV, and who died secondary to complications of chronic lung disease.

The cardiopulmonary consequences of high-risk congenital diaphragmatic hernia

The cardiopulmonary effects of high-risk congenital diaphragmatic hernia have been studied in 50 neonates at The Childrens Hospital Boston, from October 1982 through February 1987. Extracorporeal membrane oxygenation (ECMO) was added in February 1984 as therapy for infants who failed to respond to conventional therapy and had 100% predicted mortality. Twenty-three patients received ECMO support; 19 underwent cardiac catheterization immediately after surgery and had hemodynamic parameters measured and pulmonary angiograms performed. The infants fell into two physiologic groups based on their ability to achieve a postductal P O2 ≥ 100: “responders” and “nonresponders” to conventional therapy. “Responders” most often began with left-to-right shunting, and therefore had a pulmonary vascular bed large enough to accept a full cardiac output, even though it was hypoplastic. Their episodes of right-to-left shunting were mostly caused by severe pulmonary aterial vasospasm, which could be reversed in many instances. “Nonresponders” never showed an ability to accept a cardiac output, and therefore had severe hypoplasia as a limiting condition. Survival was 68% in the “responders” and 8% in the “nonresponders”. Overall survival was 49%. Of the patients placed on ECMO, 82.6% were weaned successfully but 65.2% died eventually, most often due to complications of chronic ventilator support. Preliminary analysis of the lungs demonstrated significant iatrogenic damage, but showed some evidence of pulmonary growth. These data suggest that if support can be provided with less iatrogenic injury after ECMO, pulmonary vascular remodeling and growth may be sufficient for improved survival.

The effects of pancuronium bromide on infants with hyaline membrane disease

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Mechanical influences on the capnogram.

We found that altering aspirating flow rate (ASR) and sample tubing length (STL) affected the response time and capnogram of 2 different side-stream capnometers. Increased flow rate shortened rise time, transit time, and total delay time (TDT), whereas increased STL increased transit and TDTs but not rise time. Increasing rise time pushed the ascending limb of the capnogram to the right. Peak and baseline PCO2 values were accurate only when TDT did not exceed respiratory cycle time (RCT). Awareness of the potential for artifactual changes in the capnogram will avoid their misinterpretation as physiologic events.

Renal and hemodynamic effects of dopamine in infants following cardiac surgery

The renal and hemodynamic effects of dopamine were measured during the immediate postoperative period in six infants following repair of congenital cardiac defects. Dopamine was infused at rates of 5, 10, and 15 micrograms/kg/min. Cardiac index (CI) increased significantly at a dopamine infusion rate of 15 micrograms/kg/min. The glomerular filtration rate (GFR) and urine output increased at dopamine infusion rates of 5 and 10 micrograms/kg/min and returned to baseline at 15 micrograms/kg/min. No significant changes occurred in right atrial pressure (RAP), left atrial pressure (LAP), systemic artery pressure, systemic vascular resistance (SVR), or pulmonary vascular resistance (PVR). Heart rate (HR) increased slightly at a dopamine infusion rate of 15 micrograms/kg/min. Pulmonary artery pressure (PAP) increased significantly in only one patient. These data demonstrate that infants require high doses of dopamine to produce the hemodynamic effects seen in adults and that these higher doses may be used without adverse renal effects.

Extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation is still a relatively new technology that has recently achieved recognition after initial clinical disappointment in the late 1970s. At present, it is considered standard therapy for the full-term infant with PPHN who fails CMV and extraordinary, heroic therapy for older children and adults with ARF or cardiac failure, or both. Currently, the emphasis is on developing new technologies for increasing safety and effectiveness. Areas of interest include heparinless circuits, carotid artery reconstruction, improved monitoring, and expanding applications of VV ECMO. As ECMO becomes safer and more effective, it is believed that new and expanding patient populations will emerge to include premature infants, earlier intervention in term infants, and more liberal application to pediatric and adult populations.