Robert E. Kimura

Neonatal Subglottic Stenosis—Incidence and Trends

Objective/Hypothesis Neonatal subglottic stenosis is a known entity arising from endotracheal tube intubation. In the 1970s and 1980s, estimates of the incidence of subglottic stenosis were in the range of 0.9% to 8.3% of intubated neonates. Because of improved techniques of handling neonates who require ventilatory support, we thought the actual incidence of neonatal subglottic stenosis in the late 1990s was much lower.

Accuracy of methods for calculating postnatal growth velocity for extremely low birth weight infants.

Objective. No uniform method for calculating growth velocity (GV) (grams per kilogram per day) among extremely low birth weight (ELBW) infants has been reported. Because the calculation of actual GV is so labor intensive, investigators have estimated GV with varying approaches, making comparisons across studies difficult. This study compares the accuracy of 3 mathematical methods used for estimating average GV, namely, 2-point models using the difference between weights at 2 time points divided by time and weight (either birth weight [BW] or average weight), linear regression models that are normalized for either BW or average weight, and an exponential model. The accuracy of all models was compared with actual GVs calculated from daily weight measures for a group of ELBW infants. Methods. Actual GVs were calculated from daily weights for 83 ELBW infants admitted to the special care nursery and were compared with estimated GVs from each of the 5 models for the same infants. Results. The exponential model, using weights from 2 time points, ie, GV = [1000 × ln(Wn/W1)]/(Dn − D1), was extremely accurate, with mean absolute errors of 0.02% to 0.10%. The 2-point and linear models were highly inaccurate when BW was used in the denominator, with mean absolute errors of 50.3% to 96.4%. The 2-point and linear models were fairly accurate when average weight was used in the denominator, with mean absolute errors of 0.1% to 8.97%. Additional analyses showed that the accuracy of the 2-point and linear model estimates was affected significantly by the combination of BW, length of stay, and chronic lung disease, whereas the exponential model was not affected by these combined factors. Conclusions. GV estimates calculated with 3 commonly used models varied widely, compared with actual GVs; however, the exponential model estimates were extremely accurate. The exponential model provides the accuracy and ease of use that are lacking in current methods applied to infant growth research.

Active transport of 3-O-methyl-glucose by the small intestine in chronically catheterized rats.

A method is described for determining the fraction of intestinal 3-O-methyl-glucose (3OMG) absorption that occurs by active transport in chronically catheterized rats without the influence of anesthesia or surgical bowel manipulation. That fraction was determined by simultaneously measuring portal venous-aortic blood concentration gradients (delta C) of 3-O-methyl-glucose (3OMG) and L-glucose, metabolically inert analogues of D-glucose. 3OMG is actively and passively absorbed by the same mechanisms as D-glucose, L-glucose is only passively absorbed. The fraction of 3OMG that is actively transported was calculated from the difference between 3OMG and L-glucose absorption, divided by total 3OMG absorption. We found that more than 94% of 3-O-methyl-glucose is absorbed by active transport when luminal concentrations range from 50 to 400 mM. We conclude that in unrestrained, unanesthetized chronically catheterized rats, most 3OMG is actively absorbed by the intestine even at high luminal concentrations.

The effect of surgical bowel manipulation and anesthesia on intestinal glucose absorption in rats.

The effects of surgical bowel manipulation and anesthesia on intestinal glucose absorption were determined in chronically catheterized rats. Total and passive rates of glucose absorption were measured using 3-O-methyl-glucose (3OMG) and L-glucose, metabolically inert analogues of D-glucose. The rates of 3OMG absorption immediately postoperative and 4 h later were 86 and 62% less than the absorption rate 6 d postoperative. The absorption rates of 3OMG 1 and 2 d postoperative were not different from 6 d postoperative. Absorption of L-glucose was not altered by bowel manipulation and anesthesia. Even after correction for the increased resistance of the unstirred water layer (UWL) after bowel manipulation, the rates of total and active intestinal glucose absorption immediately postoperative were only 11 and 15% of predicted rates of absorption. In chronically catheterized rats, > 75% of luminal 3OMG at a concentration of 400 mM was absorbed by active transport. The Km and Vmax of 3OMG active transport corrected for the resistance of the UWL were 11.3 mM and 15.6 mumoles/min, respectively. We conclude that measurements of intestinal glucose absorption performed within 24 h of surgical bowel manipulation greatly underestimate active absorption even if corrections are made to account for the increased resistance of the UWL.

Calculating postnatal growth velocity in very low birth weight (VLBW) premature infants

Objective:Currently, there is no standardized approach to the calculation of growth velocity (GV; g kg –1 day–1) in hospitalized very low birth weight (VLBW) infants. Thus, differing methods are used to estimate GV, resulting in different medical centers and studies reporting growth results that are difficult to compare. The objective of this study was to compare actual GV calculated from infant daily weights during hospitalization in a Neonatal Intensive Care Unit (NICU) with estimated GV using two mathematical models that have been shown earlier to provide good estimated GVs in extremely low birth weight (ELBW) infants: an exponential model (EM) and a 2-Point model (2-PM).Study Design:Daily weights from 81 infants with birth weights (BWs) of 1000 to 1499 g were used to calculate actual GV in daily increments from two starting points: (1) birth and (2) day of life (DOL) of regaining BW. These daily GV values were then averaged over the NICU stay to yield overall NICU GV from the two starting points. We compared these actual GV with estimated GV calculated using the EM and 2-PM methods.Results:The mean absolute difference between actual and EM estimates of GV showed <1% error for 100% of infants from both starting points. The mean absolute difference between actual and 2-PM estimates showed <1% error for only 38 and 44% of infants from birth and regaining BW, respectively. The EM was unaffected by decreasing BW and increasing length of NICU stay, whereas the accuracy of the 2-PM was diminished significantly (P<0.001) by both factors.Conclusion:In contrast to the 2-PM, the EM provides an extremely accurate estimate of GV in larger VLBW infants, and its accuracy is unaffected by common infant factors. The EM has now been validated for use in all VLBW infants to assess growth and provides a simple-to-use and consistent approach.

Morphological Basis of Directional Sensitivity of the Outer Hair Cells in the Organ of Corti

Electron‐microscope studies of cross sections of hair bundles on the outer hair cells in the organ of Corti show a consistent orientation of the sensory hairs. In the cuticle, a basal body is regularly found on the side of the cell toward the Hensens cells. The sensory hairs are organized in the shape of w pointing towards the basal body. The morphological polarization of the hair cells in the organ of Corti is discussed in the light of similar polarization of the hair cells in the vestibular sensory epithelia and the lateral‐line canal organs. A close relation is to be found between the morphological and electrophysiological polarization of the mechanoreceptors in the sense organs of hearing and equilibrium.

Divergent Views of Hope Influencing Communications Between Parents and Hospital Providers

This study evaluated parents’ and health care providers’ (HCPs) descriptions of hope following counseling of parents at risk of delivering an extremely premature infant. Data came from a longitudinal multiple case study investigation that examined the decision making and support needs of 40 families and their providers. Semistructured interviews were conducted before and after delivery. Divergent viewpoints of hope were found between parents and many HCPs and were subsequently coded using content analysis. Parents relied on hope as an emotional motivator, whereas most HCPs described parents’ notions of hope as out of touch with reality. Parents perceived that such divergent beliefs about the role of hope negatively shaped communicative interactions and reduced trust with some of their providers. A deeper understanding of how varying views of hope might shape communications will uncover future research questions and lead to theory-based interventions aimed at improving the process of discussing difficult news with parents.

Portal Venous and Aortic Glucose and Lactate Changes in a Chronically Catheterized Rat

ABSTRACT: A method for portal venous, aortic, and gastric cannulation in the rat is described. Changes in mean portal venous and aortic blood glucose and lactate concentrations after an intragastric infusion of d-glucose to chronically catheterized rats (after regaining preoperative weight) were compared to those of acutely catheterized rats (1 h after catheter placement). Both portal venous and aortic catheters were patent for blood sampling in 67% of rats 8 days after catheter placement and 42% after 14 days. After intragastric infusion of 10 ml of 0.29 M dextrose, mean aortic blood glucose and lactate concentrations in chronically catheterized rats increased 80 and 73%, respectively, 15 min after infusion and decreased to preinfusion concentrations by 60 min. In acutely catheterized rats, mean aortic glucose and lactate concentrations increased linearly for 60 min. The concentration differences between portal venous and aortic blood glucose and lactate concentrations in chronically catheterized rats were not significantly different than baseline differences. The portal venous glucose concentrations were significantly greater than aortic concentrations in acutely catheterized rats 15, 30, and 45 min after the glucose infusion when compared to baseline differences. These data suggest that the rate of glucose uptake and metabolism to lactate is significantly altered in acutely catheterized rats when compared to chronically catheterized animals.

Glutamine Oxidation by Developing Rat Small Intestine

ABSTRACT: Glutamine has been reported to be a major oxidative substrate in adult rat small intestine. The significance of glutamine by developing rat jejunal tissue slices and isolated mitochondria was determined. Jejunum slices from suckling rats actively oxidized glutamine at rates significantly greater than adult slices. Increasing the glutamine concentration (0.5-4 mM) in the assay increased glutamine by jejunum of suckling pups by 30% compared to a 100% increase in adult jejunum. Glutamine oxidation by isolated jejunal mitochondria was similar in suckling and adult rat. Glutamine oxidation by jejunum of suckling rat was increased in the presence of 5 mM glucose whereas adult glutamine oxidation was not affected by exogenous glucose. Glutamine inhibited glucose oxidation by jejunum of both suckling and adult rats. In adult jejunal homogenates alanine aminotransferase activity was 2-fold greater than in suckling animals. In the presence of 10 mM aminooxyacetate, a known inhibitor of alanine aminotransferase, glutamine oxidation by jejunum of suckling rat was inhibited by 95%, suggesting that alanine aminotransferase is a major metabolic pathway for the oxidation of glutamine.

Parent decision making for life support for extremely premature infants: from the prenatal through end-of-life period.

ABSTRACT Most deaths of extremely premature infants occur in the perinatal period. Yet, little is known about how parents make life support decisions in such a short period of time. In the paper, how parents make life support decisions for extremely premature infants from the prenatal period through death from the perspectives of parents, nurses, and physicians is described. Five cases, comprised of five mothers, four neonatologists, three nurses, and one neonatal nurse practitioner, are drawn from a larger collective case study. Prenatal, postnatal and end-of-life interviews were conducted, and medical record data were obtained. In an analysis by two research team members, mothers were found to exhibit these characteristics: desire for and actual involvement in life support decisions, weighing pain, suffering and hope in decision making, and wanting everything done for their infants. All mothers received decision making help and support from partners and family, but relationships with providers were also important. Finally, external resources impacted parental decision making in several of the cases. By understanding what factors contribute to parents’ decision making, providers may be better equipped to prepare and assist parents when making life support decisions for their extremely premature infants.