Renal Acid-Base Titration Studies in Infants with and without Metabolic Acidosis in the Postneonatal Period

Svenningsen, N. W.

doi:10.1203/00006450-197406000-00007

Cited by 52 publications

(22 citation statements)

References 16 publications

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“…The normal blood total CO2 values found in prematures are lower than those observed in older children [21], but rise in the LBW infant during the first 3 weeks of extrauterine life from a mean of 18.6 to 20.3 mEq/1 [ 16], The interpretation of this transient hypobasemia is not clear; it has been attributed to a lower renal HCO3 threshold [22] or to a reduced maximum net acid excretion [6].…”

Section: Discussionmentioning

confidence: 74%

“…However, the relationship between maturity and incidence of metabolic acidosis in the neonatal period is still controversial [10,15]. Although it has been postulated that the renal HCO3 thresh old is low in prematures [22], most studies have been performed in neonates after the 1st week of life and while receiving oral feedings [2,25]. In addition, several factors known to affect HCO3 TR and thus the renal HCO5 threshold, such as blood PCO2, serum potas sium concentration, extracellular fluid vol ume, etc., have not been evaluated in neo nates of different gestational ages.…”

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confidence: 99%

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Renal Bicarbonate Handling in Low Birth Weight Infants during Metabolic Acidosis

Zilleruelo

Sultan

Bancalari³

et al. 1986

Neonatology

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We studied the fractional excretion of bicarbonate (FE HCO₃) in 10 low birth weight infants aged 1–6 days during metabolic acidosis (base excess ≥ ––5 mEq/l) and during subsequent sodium HCO₃ infusion. The mean birth weight was 1,095 g; the mean gestational age was 29 weeks. The ability to decrease urine pH to < 5.5 and FE HCO₃ to < 1 % during metabolic acidosis was not limited by low gestational age or birth weight. After HCO₃ therapy, all infants corrected their negative base excess, and plasma HCO₃ increased significantly. All infants with blood pH ≤ 7.22 or PaCO₂ ≥ 50 mm Hg had minimal or absent FE HCO₃. Infants with elevated PaCO₂ and mild or absent acidosis also had complete HCO₃ tubular reabsorption. These results suggest that the HCO₃ tubular reabsorption is adequate during metabolic and/or respiratory acidosis in low birth weight infants.

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Section: Discussionmentioning

confidence: 74%

mentioning

confidence: 99%

Renal Bicarbonate Handling in Low Birth Weight Infants during Metabolic Acidosis

Zilleruelo

Sultan

Bancalari³

et al. 1986

Neonatology

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“…For example, in the child with a serum bicarbonate of less than 16mEq/l, second ary to diarrhea bicarbonate loss or to the hydrochloric salts of total parenteral nutrition, the minimal urinary pH is expected to be less than 6.0 and net acid excretion in excess of 70 pEq/min/1.73 m2 [24][25][26]. Term infants after the first week of life [22,23] are able to lower urinary pH and excrete net acid similar to older children (table I). Preterm infants after the first 4-6 weeks of life also demonstrate normal acidification capacities, but not be fore this period (table I).…”

Section: Acid Loading Studiesmentioning

confidence: 99%

Tubular Disorders of Acid-Base and Phosphate Metabolism

Chan¹,

Alon²

1985

Nephron

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“…;IS p;~sscd. Rcn:tl hicarhonatc thrcsholcl \vas defined arllitrarily as tlic level of bicarbon;~tc in pl;~sma ;~t wllich the 11ic;rrbonatc cscretic>n in urinc is 20 pEcl/IOO ml of glonlerul;~r filtr;ition ratc (GI:l<) (7,38).…”

Section: Speculationmentioning

confidence: 99%

Influence of Fetal Extracellular Volume Contraction on Renal Reabsorption of Bicarbonate in Fetal Lambs

et al. 1977

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In orclcr to clcternline the renal thresholcl for bicarbonate in tlie fetal Ian111 ancl factors that niay influence renal reabsorption of bicarl)onate in the fetus, 18 acute fetal l a n~b preparations (110-140 clays of gestation) were stutliecl. In tlie first series of experinlents involving nine fetuses, the renal bicarbonate thresholtl of nornlal fetuses varied fro111 12.0 to 23.5 rnhl/liter with a rnenn value of 17.7 ? 1.37 n~hl/liter. This is significantly lower ( P < 0.005) than the value n~easurecl in five adult sheep of 28.7 ? 1.68 111hl/liter. There was a significant ant1 positive correlation bettveen tlie fetal pl:isn~a bicarbonate at thrcsholtl level ant1 the fetal kiclney weight, as well as fetal age. In a secontl series of experin~ents, the excretion of 1)icarl)onatc ancl socliuni was stuelied in nine fetuses I)cfore ant1 after tlehgdration by peritoneal tlialysis. After peritoneal tlialysis there was a significant clccrease in urinary p l i (ID < 0.025), 1)icarbonate excretion ( P < 0.001), socliurn excretion (P < 0.001), fractional cxcretion of socliuni (ID < 0.001), and a significant increase in bicarbonate reabsorption (P < 0.01). When glucose was replaced by ~nannitol in tlie peritoneal tlialysis floicl the effects on bicarbonate reabsorption par:~llclecl tliose rrhrn glucose bras present in tlialysis fluitl. It was also slloun that when glucose was given intravenously to the fetus, up to a plasnla concentration of 200 nig/100 1111, tllere was no effect on tlic fetal renal reabsorption of bicarbonate. These data inclicatc that the lorv tl~resholtl for bicarbonate reabsorption by tlie fetal kitlney is not clue to a lin~itecl capacity to increase 1)icarbonate or socliun~ reabsorption ancl suggest that the fetal kiclney is ablc to respontl to volu~ile clepletion by increasing its reabsorption in bicarbonate ancl electrolytes. SpeculationA nu~ilber of factors have been suggestctl to explain the low bicarbonate thresholcl observecl (luring fetal life ancl during the early newborn periocl. These inclucle the inln~aturity of the nephron, the oncotic press~lre in tlie peritubular rapillary circulation, the influence of distribution of intrarenal bloocl flow, the role playecl by the re11i11-angiotcnsir~ alclosterone sjsteni, ant1 the effect of a and / 3 aelreriergic stimulation.Tlie present study suggests that the state of high extracellular fluid volume that exists during fetal life and the early newborn period significantly influences the maturation of the renal thresl~old for bicarl)onate.Tlic regulation of acid-base homeostasis by the mature kidney involves tlic reabsorption of filtered bicarbonate on the one hand and the cxcrctiori of hydrogen ion as titrable acid and ammonium o n the other.

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Renal Acid-Base Titration Studies in Infants with and without Metabolic Acidosis in the Postneonatal Period

Cited by 52 publications

References 16 publications

Renal Bicarbonate Handling in Low Birth Weight Infants during Metabolic Acidosis

Renal Bicarbonate Handling in Low Birth Weight Infants during Metabolic Acidosis

Tubular Disorders of Acid-Base and Phosphate Metabolism

Influence of Fetal Extracellular Volume Contraction on Renal Reabsorption of Bicarbonate in Fetal Lambs

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