ANEXO DE TABLA

Physiologic Changes in Pregnancy

Accurate assessment of the pregnant trauma victim requires knowledge of the physiologic changes that normally occur during gestation. No organ system is

unaffected, but the functions of the cardiovascular and respiratory systems are altered most dramatically. Plasma volume increases by 50%, while red blood cell mass increases by 25%, resulting in a physiologic anemia. Leukocytosis normally occurs, peaking in the third trimester with a white blood cell count of 12,000 to 18,000/mm ³ and 25,000/mm ³ in labor. Cardiac output increases by 4.5 to 6.0 liters per minute (30% to 50%), primarily as a result of a gradual increase in stroke volume to 50%

above nonpregnant levels. The majority of pregnant women have a widely split first heart sound, a third heart sound, and a systolic ejection murmur. Over 10% of cardiac output goes to the uterus at term, and veins in the pelvis and lower extremities are engorged. Renal blood flow increases by 30%, leading to a 30% to 50%

increase in the glomerular filtration rate. As a result, the BUN and creatinine fall and should not be higher than 13 mg/dL and 0.8 mg/dL, respectively, during pregnancy.

A hormonally mediated decrease in vascular resistance leads to a midtrimester decrease in both systolic and diastolic blood pressure. All these changes are affected by maternal position. In the supine position, the uterus compresses the vena cava, resulting in decreased venous return, decreased cardiac output, a drop in blood pressure, bradycardia, and syncope.

Hyperventilation begins as early as the first trimester, probably in response to increased progesterone levels. Because of gradual elevation of the diaphragm by the enlarging uterus, functional residual capacity, residual volume, and expiratory reserve volume all decrease, while inspiratory reserve volume increases. The normal gravida at term has a chronic respiratory alkalosis with a resting carbon dioxide tension below 30 mm Hg. Seventy-five percent of gravidas experience dyspnea in the third trimester. Although arterial oxygen tension generally rises toward term, a moderate hypoxemia can occur in the supine position. Thus, the midtrimester gravida lying supine in the emergency room may be hypotensive, bradycardic, relatively hypoxemic, and anemic, all because of normal physiologic changes.

The ABCs

Taking into consideration the physiology of pregnancy, the pregnant trauma patient should be assessed initially as any trauma victim is assessed, according to the ABCs: airway, breathing, and circulation. In a rapid assessment of the patient's status, airway patency and adequacy of respirations should be established.

Supplemental oxygen should be administered to all patients; the patient who is not breathing spontaneously should be intubated and mechanically ventilated. A wedge should be placed under the right hip to displace the uterus off the vena cava. Pregnancy significantly slows gastrointestinal motility, so all pregnant women should be assumed to have a full stomach. The conscious patient should be given sodium citrate or a similar antacid, while the airway of the unconscious patient should be protected.

If cardiac function is adequate, attention should be turned to maintaining adequate circulating volume. One or two large-bore intravenous lines should be established and Ringer's lactate solution given. Infusion of large volumes of sodium chloride should be avoided, because it can lead to hyperchloremic acidosis that would

exacerbate lactic acidosis caused by poor perfusion. If the patient is bleeding, packed red blood cells should be ordered and administered as soon as possible.

If cardiac arrest has occurred, full resuscitation should be initiated as for any other patient. CPR at most generates only 30% of the normal cardiac output; CPR of a pregnant woman in left lateral tilt will be even less effective. The patient must therefore remain supine, and someone must be assigned to elevate the uterus manually off the vena cava. It can be assumed that perfusion to the uterus will be negligible during CPR. The general consensus is that a fetus can survive total asphyxia for at most 4 to 6 minutes. If cardiac function has not been restored within 4 minutes of arrest and the fetus is still alive, an emergent, nonsterile, classic cesarean section should be performed without anesthesia at the bedside, and the uterus and abdominal incisions closed as rapidly as possible. If cardiac arrest has persisted for more than 6 minutes but fetal cardiac activity continues, delivery should still be performed. In addition to possibly saving the fetus, evacuation of the uterus will facilitate CPR by improving cardiovascular dynamics.

The American College of Obstetricians and Gynecologists recommends that any pregnant woman sustaining trauma beyond 22 to 24 weeks gestation undergo fetal monitoring for a minimum of 4 hours. If more than four contractions per hour are observed, if rupture of membranes, bleeding, fetal arrhythmia, or fetal heart rate decelerations occur, or if the mother is seriously injured, the patient should be admitted with continuous fetal monitoring for at least 24 hours.

Abdominal Trauma

Motor vehicle accidents are the leading cause of blunt abdominal trauma (especially if the woman is unrestrained or is not wearing her lap belt as low as possible under her uterus), followed by falls and direct assaults. Placental abruption is the most common severe complication of blunt trauma, occurring with 1% to 5% of minor

injuries and 20% to 50% of major injuries. Findings may include vaginal bleeding, uterine tenderness or contractions, as well as fetal tachycardia, decelerations, acidosis, and death. Direct fetal injury is less common but most often involves fetal skull and brain injury as a result of maternal pelvic fracture. Rupture of the liver or spleen can accompany blunt trauma, and rupture of the uterus occurs in less then 1% of cases. Bladder injury or rupture is more common after 20 weeks, when the bladder assumes an intraabdominal position and no longer is protected by the pelvis. Bladder injury may also result from pelvic fracture.

A patient with any signs of shock or peritoneal irritation is appropriately suspected to have major intraabdominal injury. Intraabdominal bleeding can be detected with intraperitoneal lavage, just as in the nonpregnant patient. Bladder injury is suspected when a urinary catheter cannot be passed, fails to return urine, or returns grossly bloody fluid. Bowel injury is uncommon, except at points of fixation. Uterine rupture usually results in vaginal bleeding, hypotension, absent fetal heart tones, and hematuria if the rupture involves the anterior uterine wall. If significant injury is suspected, the patient should be stabilized and a laparotomy performed as rapidly as possible. Extent of injuries, gestational age, and assessment of fetal well being are considerations for fetal delivery. Appropriate counseling should be provided regarding the possibility of hysterectomy, and blood products should obviously be available.

However, if the patient is stable and a CT scan or other radiologic studies are necessary for diagnostic purposes, they should be performed. If at all possible, the patient should be positioned with a wedge under one hip to deflect the uterus off the vena cava. The amount of radiation exposure resulting from standard radiologic procedures is less than the minimum dose associated with fetal teratogenicity or growth effects. The fetus is most susceptible before 15 weeks gestation, when radiation doses of 10 rad (0.1 Gy) or greater can cause mental retardation. At 16 to 25 weeks, the risk is considerably less, and radiologic procedures at 25 weeks or beyond pose minimal to no risk. Most authorities recommend limiting fetal exposure to less than 5 rad (0.05 Gy). Most plain radiographs entail doses of less than 1 rad (0.01 Gy); an abdominal CT scan exposes the fetus to 2 to 2.6 mrad (0.02 to 0.026 Gy). MR imaging does not require ionizing radiation and thus does not entail risk at any gestational age. Medical and surgical care should not be compromised in any way because the patient is pregnant. If the woman is Rh negative and unsensitized, Rh ₀(D) immune globulin will protect her if there was fetal-maternal bleeding.

Penetrating Abdominal Trauma

Gunshot and knife wounds are responsible for most cases of penetrating abdominal trauma in pregnancy. As the uterus grows out of the pelvis, it becomes more likely that the uterus will be a site of injury. Penetration of the uterus results in maternal mortality in less than 5% of cases, but in fetal injury in 59% to 89% of cases, with fetal death in 41% to 71%. After penetrating abdominal trauma, the pregnant patient should be assessed as above and attempts made to determine the exact site(s) of injury and associated organ damage. The initial evaluation and subsequent surgical management should be the same as for the nonpregnant patient. If the uterus is the primary site of injury, exploratory laparotomy will likely be required. Bullet wounds must be explored surgically, because deflection of the bullet off intraabdominal structures can cause extensive damage and make it impossible to determine the projectile path. Knife wounds may require exploration, because the enlarged uterus compresses other intraabdominal organs and prevents structures underlying the stab wound from sliding away from the blade, as they would in the nonpregnant state.

Ultrasonographic examination of the fetus to determine age and assess viability is essential.

Decisions about whether or not to empty the uterus should be individualized. If there is extensive intrauterine damage, if the pregnancy is near term, if there is a strong suspicion of fetal hemorrhage, or if uteroplacental insufficiency is present, the fetus should be delivered and the uterus thoroughly explored. If the uterus is uninjured or the injury can be repaired without entering the uterine cavity, if the fetus is previable or dead, and if uterine size does not preclude adequate exploration of the

abdominal cavity, hysterotomy may be avoided as long as hemostasis is achieved.

Intraabdominal organs are compressed into the upper abdomen as pregnancy advances. Penetrating wounds in this area are especially traumatic, because multiple organs are injured. In decreasing order of frequency, small bowel, liver, colon, and stomach are damaged most often. For this reason, many authorities recommend that upper abdominal wounds be explored by laparotomy in all pregnant patients. Broad-spectrum antibiotics should be administered, and tocolytic therapy can be used with caution during the postoperative period. Beta mimetic agents have maternal and fetal cardiovascular effects that may confuse postoperative assessment, while magnesium sulfate is associated with maternal nausea, vomiting, and dizziness. Maintenance of normal intravascular volume and close attention to fluid balance are crucial.

Head Trauma

The gravida with head trauma should be evaluated and treated in the same way as the nonpregnant patient. Assessment begins with the ABCs. The head and neck should be immobilized as a unit in case there is cervical spine injury. In the stable patient, gestational age and viability should be assessed. Unless precluded by vertebral fractures, the uterus should be rolled off the vena cava by placing a wedge under the backboard. Mannitol, steroids, and other medications should be given, as necessary. Because fluid restriction, osmotic diuresis, maternal hypotension, and hypothermia induced during neurosurgery may reduce uteroplacental blood flow, the viable fetus should be monitored and therapeutic adjustments made as required.

Burns

Burns are described as being partial or full thickness and quantitated according to the percentage of surface area affected. Extensive full-thickness burns result in severe thermal instability and dramatic fluid loss. Hypovolemic shock can occur, especially within the first 36 hours. Airway management and treatment of the burn, itself, should be the same for pregnant and nonpregnant patients. The pregnant burn victim, however, requires meticulous attention to fluid management, with

consideration of the expanded intravascular volume and altered cardiovascular dynamics associated with pregnancy (see above). Fetal status is related directly to the adequacy of uteroplacental perfusion; poor outcome is associated with inadequate fluid resuscitation. If more than 50% of the patient's surface area is affected,

immediate delivery of the viable fetus should be considered. However, in some cases, aggressive fluid resuscitation and close fetal monitoring may allow delivery to be deferred.

Thermal injury causes elevated prostaglandin levels and increased susceptibility to infection. These factors often contribute to preterm labor. Because complications typically associated with tocolytic therapy may not be tolerated by the gravid burn victim, tocolytics should be used cautiously, if at all. Indomethacin (Indocin) may be the safest agent for use before 32 weeks. If fetal surveillance (24 or more weeks gestation) indicates fetal compromise despite optimal maternal resuscitation, the fetus should be delivered.

Electrical Injury

There are very few reports of electrical injury during pregnancy. Because the uterus and amniotic fluid offer low resistance, current entering an upper xtremity and exiting a lower extremity may traverse the uterus and fetus. Maternal cardiac and respiratory status should be assessed and treated as in any injured patient.

Ultrasonographic examination and fetal monitoring should guide pregnancy management. Fetal survival without specific intervention has been reported, although immediate fetal death is also possible.

SUMMARY POINTS

The obstetrician-gynecologist must be thoroughly familiar with the normal physiologic changes of pregnancy, because these changes affect the clinical pictures of many diseases, as well as their management.

Although many disease processes are unchanged by pregnancy, the course of some diseases is altered. This alteration often affects diagnosis and therapy.

Necessary radiologic procedures can be performed during pregnancy.

Very few medications need to be restricted in pregnancy.

In general, pregnant and nonpregnant women with a medical or surgical disease should receive comparable care, although fetal well-being must be kept in mind if fetal viability has been reached.

RECOMMENDED READINGS Hematologic Disease

American College of Obstetricians and Gynecologists. Hemoglobinopathies in pregnancy. ACOG Technical Bulletin No. 220, Feb 1996.

American College of Obstetricians and Gynecologists. Thrombocytopenia in pregnancy. ACOG Practice Bulletin No. 6, 1999.

Lusher JM. Screening and diagnosis of coagulation disorders. Am J Obstet Gynecol 1996;175:778.

Olivieri NF. Medical progress: the ß-thalassemias. N Engl J Med 1999;341:99.

Rust O, Perry K. Pregnancy complicated by sickle hemoglobinopathy. Clin Obstet Gynecol 1995;38:472.

Thompson MW, McInnes RR, Willard HF. The hemoglobinopathies: modes of molecular disease. In: Thompson & Thompson genetics in medicine. Philadelphia: WB Saunders, 1991:247.

Gastrointestinal Disease

American College of Obstetricians and Gynecologists. Viral hepatitis in pregnancy. ACOG Educational Bulletin No. 248, 1998.

APGO Educational Series. Nausea and vomiting of pregnancy. 2001:1–28.

David A, Katz VL, Cox R. Gallbladder disease in pregnancy. J Reprod Med 1995;40:759.

Knox TA, Olans LB. Liver disease in pregnancy. N Engl J Med 1996;335:569.

Korelitz BI. Inflammatory bowel disease and pregnancy. Gastroenterol Clin North Am 1998;27:213.

Laifer SA, Guido RS. Reproductive function and outcome of pregnancy after liver transplantation. Mayo Clin Proc 1995;70:388.

Ramin KD, Ramin SM, Richey SD, et al. Acute pancreatitis in pregnancy. Am J Obstet Gynecol 1995;173:187.

Cardiovascular Disease

American College of Obstetricians and Gynecologists. Thromboembolism in pregnancy. ACOG Practice Bulletin No. 19, 2000.

American College of Obstetricians and Gynecologists. Cardiac disease in pregnancy. ACOG Technical Bulletin No. 166, 1992.

Bhagwat AR, Engel PJ. Heart disease and pregnancy. Cardiol Clin 1995;13:163.

Chan WS, Ray JG. Low molecular weight heparin use during pregnancy: issues of safety and practicality. Obstet Gynecol Surv 1999;54:649.

Hankins GDV, Wendel GD, Leveno KJ, et al. Myocardial infarction during pregnancy: a review. Obstet Gynecol 1985;65:139.

Lockwood CJ. Inherited thrombophilias in pregnant patients. Prenat Neonatal Med 2001;6:3.

Midei MG, De Ment SH, Feldman AM, et al. Peripartum myocarditis and cardiomyopathy. Circulation 1990;81:922.

Perloff JK. Congenital heart disease and pregnancy. Clin Cardiol 1994;17:579.

Presbitero P, Somerville J, Stone S, et al. Pregnancy in cyanotic congenital heart disease: outcome of mother and fetus. Circulation 1994;89:2673.

Renal Disease

Cunningham FG, Lucas MJ. Urinary tract infections complicating pregnancy. Baillieres Clin Obstet Gynaecol 1994;8:353.

Hou SH. Pregnancy in women on haemodialysis and peritoneal dialysis. Baillieres Clin Obstet Gynaecol 1994;8:481.

Houshiar AM, Ercole CJ. Urinary calculi during pregnancy: when are they cause for concern? Postgrad Med 1996;100:131.

Jones DC. Pregnancy complicated by chronic renal disease. Clin Perinatol 1997;24:483.

Wong KM, Bailey RR, Lynn KL, et al. Pregnancy in renal transplant recipients: the Christchurch experience. N Z Med J 1995;108:190.

Pulmonary Disease

American College of Obstetricians and Gynecologists. Pulmonary disease in pregnancy. ACOG Technical Bulletin No. 224, 1996.

Hilman BC, Aitken ML, Constantinescu M. Pregnancy in patients with cystic fibrosis. Clin Obstet Gynecol 1996;39:70.

Katz VL, Kuller JA, McMahon MJ, et al. Varicella during pregnancy: maternal and fetal effects. West J Med 1995;163:446.

Miller KS, Miller JM. Tuberculosis in pregnancy: interactions, diagnosis and management. Clin Obstet Gynecol 1996;39:120.

Rigby FB, Pastorek JG. Pneumonia during pregnancy. Clin Obstet Gynecol 1996;1:107.

Schatz M, Zeiger RS. Asthma and allergy in pregnancy. Clin Perinatol 1997;24:407.

Wendel PJ, Ramin SM, Barnett-Hamm C, et al. Asthma treatment in pregnancy: a randomized controlled study. Am J Obstet Gynecol 1996;175:150.

Neurologic Disease

American College of Obstetricians and Gynecologists. Seizure disorders in pregnancy. ACOG Educational Bulletin No. 231, 1996.

Bartleson JD. Treatment of migraine headaches. Mayo Clin Proc 1999;74:702.

Confaveux C, Hutchinson M, Hours MM, et al. Rate of pregnancy-related relapse in multiple sclerosis. N Engl J Med 1998;339:285.

Dias MS. Neurovascular emergencies in pregnancy. In: Pitkin RM, Scott JR, eds. Clinical obstetrics and gynecology. Philadelphia: JB Lippincott Co, 1994:337.

Digre KB, Varner MW, Corbett JJ. Pseudotumor cerebri and pregnancy. Neurology 1984;34:721.

Jaffe R, Mock M, Abramowicz J, et al. Myotonic dystrophy and pregnancy: a review. Obstet Gynecol Surv 1986;41:272.

Jaigobin C, Silver FL. Stroke and pregnancy. Stroke 2000;31:2948.

Mitchell PJ, Bebbington M. Myasthenia gravis in pregnancy. Obstet Gynecol 1992;80:178.

Pschirrer ER, Monga M. Seizure disorders in pregnancy. Obstet Gynecol Clin North Am 2001;28:601.

Sadasivan B, Malik GM, Lee C, et al. Vascular malformations and pregnancy. Surg Neurol 1990;33:305.

Endocrinologic Disease

American College of Obstetricians and Gynecologists. Thyroid disease in pregnancy. ACOG Technical Bulletin No. 181, 1993.

Kohlmeier L, Marcus R. Calcium disorders of pregnancy. Endocrinol Metab Clin North Am 1995;24:15.

Robertson GL. Diabetes insipidus. Endocrinol Metab Clin North Am 1995;24:549.

Rosen IB, Korman M, Walfish PG. Thyroid nodular disease in pregnancy: current diagnosis and management. Clin Obstet Gynecol 1997;40:81.

Sipes SL, Malee MP. Endocrine disorders in pregnancy. Obstet Gynecol Clin North Am 1992;19:655.

Yankowitz J, Weiner C. Medical fetal therapy. Baillieres Clin Obstet Gynaecol 1995;9:553.

Dermatologic Disease

Alsulyman OM, Ouzounian JG, Ames-Castro M, et al. Intrahepatic cholestasis of pregnancy: perinatal outcome associated with expectant management. Am J Obstet Gynecol 1996;175:957.

Errickson CV, Matus NR. Skin disorders of pregnancy. Am Fam Phys 1994;49:605.

Fuhrman L. Common dermatoses of pregnancy. J Perinat Neonat Nurs 2000;14:1.

Grin CM, Driscoll MS, Grant-Kels JM. Pregnancy and the prognosis of malignant melanoma. Semin Oncol 1996;23:734.

Uncu G, Ozan H, Tatlikazan S, et al. Gestational herpes: 3 cases. J Obstet Gynecol 1995;21:381.

Wong RC, Ellis CN. Physiologic skin changes in pregnancy. J Am Acad Dermatol 1984;10:929.

Acute Abdomen and Surgical Disease

Epstein FB. Acute abdominal pain in pregnancy. Emerg Med Clin North Am 1994;12:151.

Kochhar R, Goenka MK, Mehta SK. Endoscopic sclerotherapy during pregnancy. Am J Gastroenterol 1990;85:1132.

Mazze RI, Kallen B. Appendectomy during pregnancy: a Swedish registry study of 778 cases. Obstet Gynecol 1991;77:835.

Sharp HT. Gastrointestinal surgical conditions during pregnancy. In: Pitkin RM, Scott JR, eds. Clinical obstetrics and gynecology. Philadelphia: JB Lippincott Co, 1994:306.

Maternal Trauma

American College of Obstetricians and Gynecologists. Obstetric aspects of trauma management. ACOG Educational Bulletin No. 251, 1998.

Coleman MT, Trianfo VA, Rund DA. Nonobstetric emergencies in pregnancy: trauma and surgical conditions. Am J Obstet Gynecol 1997;177:497.

Connolly A, Katz VL, Bash KL, et al. Trauma and pregnancy. Am J Perinatol 1997;14:331.

Hoff WS, D'Amelio LF, Tinkoff GH, et al. Maternal predictors of fetal demise in trauma during pregnancy. Surg Gynecol Obstet 1991;172:175.

Kauff ND, Tejani N. Trauma in the obstetric patient: evaluation and management. Prim Care Update ObGyns 1998;5:16.

Kissinger DP, Rozycki GS, Morris JA, et al. Trauma in pregnancy: predicting pregnancy outcome. Arch Surg 1991;126:1079.