Determinante De Salud

CHAPTER 44 – Hypertension and Kidney Disease in Pregnancy
Sharon E. Maynard S. Ananth Karumanchi Ravi Thadhani
| | Physiologic Changes of Pregnancy, 1567 |
| | Preeclampsia and the HELLP Syndrome, 1569 |
| | Chronic Hypertension and Gestational Hypertension, 1582 |
| | Acute Kidney Injury in Pregnancy, 1585 |
Pregnancy is characterized by a myriad of physiologic changes, ofwhich the emergence of a placenta and growing fetus is the most dramatic. Hypertension and/or renal disease occurring in the setting of pregnancy presents a unique set of clinical challenges. This chapter includes a detailed discussion of preeclampsia, a syndrome specific to pregnancy that remains one of the most enigmatic human disorders and continues to claim the lives of thousands of mothersand neonates yearly. Other causes of acute kidney injury (AKI) in pregnancy are discussed. The chapter reviews current data on epidemiology and management issues regarding chronic hypertension, chronic kidney disease (CKD), and kidney transplantation in the setting of pregnancy. Our hope is that this chapter offers the reader insights into our emerging understanding of the pathogenesis ofpreeclampsia and provides a sound basis for the management of pregnancy from a nephrologist's perspective.
PHYSIOLOGIC CHANGES OF PREGNANCY
Hemodynamic and Vascular Changes of Normal Pregnancy
Normal pregnancy is characterized by profound vascular and hemodynamic changes that reach far beyond the fetus and placenta ( Table 44-1 ). Early in pregnancy, Systemic vascular resistance (SVR) decreases andarterial compliance increases.[1] These changes are evident by 6 weeks' gestation, prior to the establishment of the uteroplacental circulation.[2] The decrease in SVR leads directly to several other cardiovascular changes. Mean arterial blood pressure falls by an average of 10 mm Hg below baseline by the second trimester ( Fig. 44-1 ). Sympathetic activity is increased, reflected in a 15% to 20%increase in heart rate.[3] The combination of increased heart rate and decreased afterload leads to a large increase in cardiac output in the early first trimester, which peaks at 50% above prepregnancy levels by the middle of the third trimester ( Fig. 44-2 ).

TABLE 44-1 -- Physiologic Changes in Pregnancy
Physiologic Variable | Change in Pregnancy |
Hemodynamic parameters |
Plasma volume| Rises by 30%–50% above baseline. |
Blood pressure (BP) | Decreases by to about 10 mm Hg below prepregancy level; nadirs in second trimester. Gradual increase toward prepregnant levels by term. |
Cardiac output | Rises 30%–50%. |
Heart rate | Rises by 15–20 beats per minute (bpm). |
Renal blood flow | Rises by 80% above baseline. |
Glomerular filtration rate | 150–200 ml/min (rises40%–50% above baseline). |
Serum chemistry and hematologic changes |
Hemoglobin | Decreases by an average of 2 g/L (from 13 g/L to 11 g/L) owing to plasma volume expansion out of proportion to the increase in red blood cell mass. |
Creatinine | Falls to 0.4–0.5 mg/dL. |
Uric acid | Falls to a nadir of 2.0–3.0 mg/dL by 22–24 wk, then rises back to nonpregnant levels toward term. |
pH |Increases slightly to 7.44. |
PCO2 | Decreases by about 10 mm Hg to an average of 27–32 mm Hg. |
Calcium | Increased calcitriol stimulates increased intestinal calcium reabsorption and increased urinary calcium excretion. |
Sodium | Falls by 4–5 mEq/L below nonpregnancy levels. |
Osmolality | Falls to a new osmotic set point of about 270 mOsm/kg. |

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FIGURE 44-1 Changes in meanarterial pressure in normal gestation. Mean arterial blood pressure (MAP) according to gestational age in weeks in a large representative cohort of pregnant women followed longitudinally. (Adapted from Thadhani R, Ecker JL, Kettyle E, et al: Pulse pressure and risk of preeclampsia: A prospective study. Obstet Gynecol 97(4):515–520, 2001.) | |

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FIGURE 44-2 Hemodynamic changes in...