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Biomedical subjects

J M Davison

Publications and source records attributed to J M Davison.

At least 37 records · Page 2Linked to original sources
PubMed1997

Edema in pregnancy.

During normal pregnancy total body water increases by 6 to 8 liters, 4 to 6 liters of which are extracellular, of which at least 2 to 3 liters are interstitial. At some stage in pregnancy 8 out of 10 women have demonstrable clinical edema. There is also cumulative retention of about 950 mmol of sodium distributed between the maternal extracellular compartments and the product of conception. Thus, changes in factors governing renal sodium and water handling accompany alterations in local Starling forces whereby there is a moderate fall in interstitial fluid colloid osmotic pressure (COPi) and a rise in capillary hydrostatic pressure (Pc), as well as changes in hydration of connective tissue ground substance. Edema is a traditional criterion for diagnosing pre-eclampsia, but should no longer be used as its detection is not clinically useful. The role of diuretics in obstetric practice should be restricted to the management of pulmonary edema in pre-eclampsia. Volume expansion therapy in pregnancy runs the risk of pulmonary or cerebral edema, particularly in the immediate puerperium. Vulval edema and erythematous edema associated with deep venous thrombosis are rare but dangerous complications of pregnancy.

Diuretics↗
PubMed1996

Fetal hepatic necrosis following blood sampling from the intrahepatic vein.

Previous reports have suggested that fetal blood sampling from the intrahepatic vein is not associated with significant fetal hepatic injury. We report a case of fetal liver necrosis occurring 24 h following blood sampling from the intrahepatic vein of a fetus with severe growth retardation at 34 weeks. The placenta was in a posterior position, precluding either blood sampling from the placental insertion or placental biopsy. Fetal death occurred in utero within 24 h of the procedure, which was carried out by an experienced operator. At post-mortem the liver appeared normally formed, but the right lobe was diffusely congested, with a well-defined demarcation line between the right and left lobes. Liver histology revealed extensive recent haemorrhagic necrosis of the right lobe.

Adult↗
PubMed1996

The metabolic clearance of atrial natriuretic peptide during human pregnancy.

OBJECTIVE: Our purpose was to determine whether human pregnancy alters the metabolic clearance and natriuretic effect of atrial natriuretic peptide. STUDY DESIGN: The metabolic clearance rate of atrial natriuretic peptide (ANP 99-126) was measured serially in nine normotensive primigravid women studied in early and late pregnancy and again 4 months post partum (nonpregnant). Metabolic clearance of atrial natriuretic peptide was determined by use of a two-tier constant infusion technique (6 and 12 ng/kg/min, respectively). Sodium excretion was determined from 30-minute urine collections taken before and during infusion of atrial natriuretic peptide at both 6 and 12 ng/kg/min. RESULTS: Basal plasma atrial natriuretic peptide levels increased with gestation: in early pregnancy 18.0 +/- 2.7 pg/ml, in late pregnancy 22.6 +/- 4.2 pg/ml, and post partum 19.5 +/- 3.6 pg/ml. Infusion of atrial natriuretic peptide at 6 and 12 ng/kg/min produced two distinct physiologic plasma levels of atrial natriuretic peptide. The metabolic clearance rates for nonpregnant women and those in early and late pregnancy at 6 and 12 ng/kg/min, respectively, were 3.4 +/- 0.4 and 2.9 +/- 0.4 L/min at plasma atrial natriuretic peptide levels of 86.2 +/- 13.2 and 179.8 +/- 42.5 pg/ml, respectively, 4.3 +/- 0.5 and 4.3 +/- 0.5 L/min at plasma atrial natriuretic peptide levels of 61.1 +/- 4.9 and 131 +/- 20.9 pg/ml (p < 0.01, nonpregnant vs early pregnancy), and 3.8 +/- 0.6 and 3.8 +/- 0.5 L/min at plasma atrial natriuretic peptide levels of 72 +/- 8.0 and 136 +/- 18.3 pg/ml (p < 0.05, nonpregnant vs late pregnancy), respectively. Infusion of atrial natriuretic peptide produced natriuresis in both pregnant and nonpregnant states; sodium excretion (basal to atrial natriuretic peptide infusion at 12 ng/kg/min) increased from 133 +/- 19 to 207 +/- 18 mumol/min, 129 +/- 21 to 374 +/- 35 mumol/min, and 128 +/- 20 to 221 +/- 33 mumol/min in nonpregnant women and those in early and late pregnancy, respectively. CONCLUSIONS: The metabolic clearance of atrial natriuretic peptide increased by 16 weeks' gestation and remained elevated thereafter. There appears to be no attenuation of the natriuretic effect of infused atrial natriuretic peptide in normotensive human pregnancy.

Atrial Natriuretic Factor↗
PubMed1996

Altered glomerular permselectivity to neutral dextrans and heteroporous membrane modeling in human pregnancy.

Hyperfiltration precedes renal function loss in several nephropathies. Animal studies suggest this may be due to accompanying increases in transglomerular capillary hydrostatic pressure difference (delta P) and/or altered glomerular processing of macromolecules. Renal hemodynamics increase strikingly in human pregnancy. To test the hypothesis that these alterations are not potentially harmful, clearances of inulin, p-aminohippurate, and neutral dextrans were measured at 16- and 36-wk gestation, then 4 mo postpartum, in 11 normotensive women. Results were analyzed using two computer modeling programs. Glomerular filtration rate and renal plasma flow (RPF) were markedly elevated in early and late pregnancy (135 +/- 6 and 895 +/- 53 and 135 +/- 6 and 754 +/- 32 ml/min, respectively, vs. 87 +/- 7 and 520 +/- 17 ml/min postpartum). Gestational hyperfiltration was primarily due to RPF increments with a minor contribution from decrements in capillary oncotic pressure. Fractional dextran clearances (particularly the smaller dextrans, 30-39 A radii) were lower in early pregnancy, decreasing further in late pregnancy. There was no evidence of increased delta P and alterations in glomerular membrane porosity resolved postpartum. These data provide a database by which to study effects of pregnancy on chronic renal disease.

Adult↗
PubMed1996

Renal reserve during human pregnancy.

Pregnancy in healthy women is associated with increments in glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). We hypothesized that the hyperfiltration of normal pregnancy attenuates or exhausts renal reserve. In 21 healthy females studied serially in early and late pregnancy and then on average 15 wk postpartum, GFR and ERPF were determined by inulin and p-aminohippurate clearances, respectively, before and during either an amino acid infusion (Vamin 9; Kabi Pharmacia) (n = 14) or a control infusion of Hartman's solution (n = 7), both infused at 4 ml/min for 210 min. In early and late pregnancy, GFR increased significantly in response to amino acid infusion [from 137 +/- 29 to 162 +/- 35 ml/min (P < 0.001) and from 134 +/- 29 to 148 +/- 40 ml/min (P < 0.01), respectively], with the increments (18 and 10%, respectively) not significantly different from postpartum (non-pregnant) when GFR increased by 12% from 94 +/- 22 to 105 +/- 23 ml/min (P < 0.002). Amino acid infusion significantly increased ERPF from 874 +/- 188 to 980 +/- 215 ml/min in early pregnancy (P < 0.01), from 684 +/- 135 to 773 +/- 181 ml/min in late pregnancy (P < 0.01), and from 507 +/- 121 to 560 +/- 141 ml/min postpartum (P < 0.006), increments of 12, 13, and 10%, respectively. GFR did not change in response to control infusion. We conclude that, despite gestational increments in renal hemodynamics of > 40%, pregnancy does not attenuate the renal response to amino acid infusion.

Amino Acids↗
PubMed1996

Effect of atrial natriuretic peptide on renal hemodynamics and sodium excretion during human pregnancy.

The effect of infused atrial natriuretic peptide (ANP) on sodium excretion (UNa), glomerular filtration rate (GFR), and effective renal plasma flow (ERPF) was studied in 12 normotensive primigravidae at 32 wk gestation [late pregnancy (LP)] and again 4 mo postpartum [nonpregnant (NP)]. Three 20-min steady-state (renal) clearances of inulin and p-aminohippurate were used to measure GFR and ERPF, respectively, before and after infusion of ANP at 2 pmol.kg-1.min-1. Basal plasma ANP (pANP) was increased in LP compared with NP [7.8 +/- 0.6 vs. 3.3 +/- 0.4 pmol/l (P < 0.0001), respectively]. In LP, infusion of ANP increased pANP from 7.8 +/- 0.6 to 21.8 +/- 1.4 pmol/l (P < 0.00001), which produced a natriuresis [UNa of 0.18 +/- 0.02 vs. 0.25 +/- 0.03 mmol/min (P = 0.03), respectively], with no change in GFR (153 +/- 13 vs. 142 +/- 8 ml/min, P = 0.16) but a significant reduction in ERPF (766 +/- 52 vs. 660 +/- 31 ml/min, P = 0.002). In NP, ANP infusion increased pANP from 3.3 +/- 0.4 to 27.7 +/- 2.5 pmol/l (P < 0.00001), which produced no significant natriuresis [UNa of 0.22 +/- 0.07 vs. 0.26 +/- 0.09 mmol/min (P = 0.15), respectively] and no change in GFR (87 +/- 3 vs. 89 +/- 3 ml/min), but again a reduction in ERPF (486 +/- 17 vs. 414 +/- 9 ml/min, P < 0.001).

Atrial Natriuretic Factor↗
PubMed1996

Repeated successful pregnancies after kidney transplantation in 102 women (Report by the EDTA Registry).

BACKGROUND: Between 1967 and 1990, 820 successful pregnancies in 718 women on renal replacement therapy (RRT) were reported to the EDTA Registry. METHODS: This study analyses data on repeated successful pregnancies in 102 of these women, of whom 99 had two and three had three pregnancies. RESULTS: Primary renal diseases were mainly glomerulonephritis (41%), pyelonephritis (32%), and congenital malformations such as cystic diseases and hypoplasia or dysplasia (3%). Mean age at start of RRT was 21 years +/-5 SD. Ninety-four per cent of the women had the same transplant during the first and second pregnancies; 85% of these were alive with their first graft and 9% with a second graft; 4% were retransplanted after the first pregnancy and 2% were back on dialysis during the second pregnancy. Of the mothers with two successful pregnancies, two-thirds had a serum creatinine below 121 micromol/l after the first or after the second pregnancy. Six mothers lost their first graft after the first pregnancy. None of the mothers had died after delivery of the second or third baby. Several features of the first and the second pregnancy in these mothers were quite similar. Mean gestational age was 36 weeks+/-3SD during first and second pregnancy. Mean birth weight (height) of the first child was 2490 g+/-660 SD (48 cm+/-4 SD) and 2587 g+/-639 SD (50 cm+/-3 SD) of the second child (NS). Neonatal mortality was 4% after the first and second delivery; congenital abnormalities were found in five and three children respectively. CONCLUSIONS: Fourteen per cent of mothers who had a successful pregnancy on RRT subsequently had a second baby. Repeated pregnancies should not adversely affect graft function and/or fetal development provided that graft function was well preserved at the time of conception.

Adult↗
PubMed1995

Effect of pregnancy on the long-term function of renal allografts: an update.

In 1992 we published a case-controlled study of posttransplant follow-up in 36 renal allograft recipients (Am J Kidney Dis 19:167-172, 1992). Eighteen of these patients became pregnant and comprise the index group; the 18 patients who did not become pregnant were considered controls. By the end of the follow-up period, plasma creatinine in the index group and controls had increased by 19% and 8%, respectively. Graft loss or chronic rejection occurred in one patient in the index group and in two in the control group. As there were no significant differences between the two groups, we concluded that pregnancy was unlikely to have a major effect on long-term graft function and/or survival. Subsequently, a case control study of Finnish women demonstrated graft survival favoring women who never conceived versus those who did (69% v 100%, respectively; P < 0.005) and thus prompted us to extend our posttransplant follow-up by a further 3 years. Data are currently available for 17 index subjects and 17 controls and during the entire follow-up period, graft losses have occurred in one index subject and in four controls. Plasma creatinine at the end of the follow-up period (1.40 +/- 0.52 mg/dL and 1.54 +/- 0.95 mg/dL, respectively) had increased from 3 years earlier by 11% and 7%, respectively, increments across time that were not significant. Although the increase in plasma creatinine was greater in the index subjects compared with the controls, there were no significant differences between the two groups. While our data do not exclude a minor deleterious effect of pregnancy on long-term graft function, we believe that female allograft recipients can be reassured that pregnancy is unlikely to substantially alter long-term graft function.

Adult↗
PubMed1995

Osmoregulation, the secretion of arginine vasopressin and its metabolism during pregnancy.

This review stresses changes in osmoregulation as well as the secretion and metabolism of arginine vasopressin during pregnancy, focusing on human gestation. Pregnant women experience a decrease in body tonicity, plasma osmolality decreasing immediately after conception to a nadir approximately 10 mosmol/kg below non-pregnant levels early in pregnancy, after which a new steady state is maintained until term. Data from both human and rodent gestation have led to a formation of how these changes occur. The osmotic thresholds for thirst and antidiuretic hormone release decrease in parallel. Lowering the threshold to drink stimulates increased water intake and dilution of body fluids. Because arginine vasopressin (AVP) release is not suppressed at the usual level of body tonicity, the hormone continues to circulate and the ingested water is retained. Plasma osmolality declines until it is below the osmotic thirst threshold, and a new steady state with little change in water turnover is established. Pregnancy is characterized by increments in intravascular volume, but volume-sensing AVP release mechanisms appear to adjust as gestation progresses so that each new volume status is "sensed" as normal. The metabolic clearance of AVP increases fourfold, the rise paralleling that of circulating cystine aminopeptidase (vasopressinase), and enzyme produced by the placenta. Furthermore, the disposal rate of 1-deamino-8-D-AVP, and AVP analogue resistant to inactivation by vasopressinase, is unaltered in pregnancy. Thus, the increase in AVP's metabolism and the high circulating aminopeptidase levels have been implicated in certain forms of transient diabetes insipidus that occur in late pregnancy. Finally, mechanisms responsible for the altered osmoregulation in pregnancy are obscure, but chorionic gonadotropin and relaxin may be implicated in the changes.

Animals↗
PubMed1994

Renal haemodynamics and tubular function in human pregnancy.

In human pregnancy, effective renal plasma flow and glomerular filtration rate increase to levels 50-80% above non-pregnant values. The increments occur shortly after conception, persist throughout the second trimester and reduce slightly in late pregnancy. The hyperfiltration of pregnancy does not seem to be a potentially damaging process, as intraglomerular pressure remains unchanged. The increased excretion of glucose and other nutrients, as well as uric acid and protein, is related in part to altered tubular function. Renal physiology is altered so much in pregnancy that non-pregnant norms cannot be used in antenatal care.

Adult↗
PubMed1994

Pregnancy in renal allograft recipients: problems, prognosis and practicalities.

Improvements in reproductive function invariably follow renal transplantation. The possibility of conception in women of childbearing age emphasizes the need for compassionate and comprehensive counselling. Couples who want a child should be encouraged to discuss all the implications. Therapeutic abortion is undertaken in 20% of conceptions and the spontaneous abortion rate is about 14%, the same as for the normal population. Of the conceptions that continue beyond the first trimester, 93% end successfully. In most women, renal function is augmented during pregnancy, but permanent impairment occurs in 15% of pregnancies. In others there may be transient deterioration in late pregnancy (with or without proteinuria). There is a 30% chance of developing hypertension, pre-eclampsia or both. Preterm delivery occurs in 45-60%, and intrauterine growth retardation in at least 20% of pregnancies. Despite its pelvic location, the transplanted kidney rarely produces dystocia and is not injured during vaginal delivery. Caesarean section should be reserved for obstetric reasons only. Neonatal complications include respiratory distress syndrome, leucopenia, thrombocytopenia, adrenocortical insufficiency and infection. No predominant or frequent developmental abnormalities have been described and data on infancy and childhood are encouraging. Future clinical and laboratory research needs to focus on improving prepregnancy assessment criteria, better understanding of the mechanisms of gestational renal dysfunction, proteinuria and the rare, but devastating, accelerated rejection, assessing the side-effects and implications of immunosuppression in pregnancy and learning more about the remote effects of pregnancy on both renal prognosis and the offspring.

Adult↗
PubMed1994

Detecting premalignant cervical lesions. Contribution of screening colposcopy to cytology.

The combination of parallel cytology and screening colposcopy was found to increase the detection of premalignant cervical lesions from 8.2% in a group of patients (based on cytology alone) to 15.3% in that group (based on the combination). The combination of the two methods used in parallel increased the sensitivity, negative predictive value and efficiency of cervical cancer screening over cytology alone while having only a small negative impact on the positive predictive value of a positive test. The addition of screening colposcopy to cytology produces a significant improvement over current uniphasic screening protocols.

Biopsy↗