P | Nurse Key

Papanicolaou smear

Includes: Human Papilloma Virus testing (HPV DNA)

Purpose of the test

The Papanicolaou smear is used to detect inflammation, infection, premalignant changes, and malignancy of the cervix.

Basics the nurse needs to know

The Papanicolaou (Pap) smear is an inexpensive screening test that examines cervical cell scrapings for abnormality. Most commonly, the reported results are classified according to the Bethesda system. When an abnormality is present, the changes can be of an infectious, inflammatory origin or they can be squamous cell or glandular cell abnormalities. The abnormalities are graded in severity.

The borderline lesion (inconclusive result) is defined as atypical squamous cells of undetermined significance (ASC-US). The squamous intraepithelial lesions (SIL) are graded from low grade to high grade. The low-grade squamous intraepithelial lesion (LSIL) consists of condyloma, mild dysplasia (CIN 1)—a precancerous state—or both. A high-grade squamous intraepithelial lesion (HSIL) ranges from moderate dysplasia (CIN 2) to severe dysplasia (CIN 3), including carcinoma in situ and invasive carcinoma or adenocarcinoma (Box 8).

Human papilloma virus

The human papilloma virus is the causative agent for genital warts and almost all cases of carcinoma of the cervix. There are 200 genotypes (genetic subtypes) of this virus, but 15 to 20 of them are capable of causing cancerous cervical mutations (Forbes, Sahm & Weissfeld, 2007). HPV infection is the most common of the sexually transmitted diseases. Diagnosis of the HPV infection and its viral subtype is made by HPV DNA probe assay performed on the cervical cells obtained from the PAP smear. Genotypes 16 and 18 cause 70% of the cases of cervical cancer and the remainder of the cases are caused by various other HPV genotypes (CDC, 2010).

Most women who are sexually active develop an HPV infection. Usually, these infections are cleared spontaneously within a few weeks to months. There are, however, some cases where the virus persists and eventually cancer of the cervix develops. To date, except for those women who are immunocompromised, there is no way to predict which women will be unable to eliminate the infection spontaneously.

REFERENCE VALUES

Bethesda system classification: Normal; within normal limits

HPV DNA: Negative

How the test is done

Using a vaginal speculum to enhance visibility, the physician or nurse practitioner collects the patient’s secretions and cells from the cervix (Figure 74). The fluid and tissue scrapings are placed in the specimen jar with liquid-based/thin prep solution. In the laboratory, the cells of the tissue are examined microscopically. A sample of the cells also can be analyzed for the DNA of the human papilloma virus and its genotype.

Figure 74. Papanicolaou smear procedure. A, Cervix, as seen through a speculum, with the spatula being used to obtain a cell sample. B, Longitudinal view at the same point in the procedure. (From Katz VL et al: Comprehensive gynecology, ed 5, St Louis, 2007, Mosby.)

Interfering factors

• Menstruation

• Recent douching

• Vaginal infection or medication

• Recent sexual intercourse

• Inadequate specimen

• Lubricating jelly on the speculum

NURSING CARE

Posttest

• Once the gloves are removed, wash hands thoroughly.

• On the requisition form, the same identifying information is written. The physician or nurse practitioner adds any pertinent information, such as the date of last menstrual period, history of an abnormal Pap smear, carcinoma, radiation, chemotherapy, abnormal vaginal bleeding, exposure to diethylstilbestrol, a visible lesion, or recent pregnancy.

• When the woman is informed of abnormal Pap and/or HPV test results, she often requires additional information about the meaning of the results and any follow-up measures that are needed. The nurse recognizes the patient’s anxiety or confusion and can help with the emotional stress or lack of knowledge. Additional information and repetition of the instructions may be needed (Montgomery & Bloch, 2010). The nurse can provide help to clarify misconceptions and encourage the patient to complete the follow-up testing.

Health promotion

The nurse encourages parents to have their daughters routinely vaccinated against HPV infection. The CDC (2010) recommends the vaccination be done between ages 13 to 26 years, but the series can be started as early as 9 years of age. The vaccine is given in a 3-dose series.

• The American College of Obstetricians and Gynecologists guidelines (2009) provide recommendations for the timing and frequency of Pap testing as presented in Box 9. In the roles of health teaching and health promotion, the nurse should encourage women to have the Pap test and to return for results and follow-up appointments, as recommended. The nurse can also work in collaboration with community-based health programs because they have been effective in providing breast and cervical screening tests to low-income and uninsured women. For all women, the goal of the Pap smear testing is to detect cervical tissue changes and premalignant conditions before they become advanced or change into malignant tumors. Early detection and treatment greatly reduce the morbidity and mortality of cancer of the cervix.

Box 9 ACOG 2009 Recommended Guidelines for Timing and Frequency of Pap Testing

• Cervical cytology screening is recommended every 2 years for women between the ages of 21 years and 29 years.

• Women aged 30 years and older who have had three consecutive negative cervical cytology screening test results and who have no history of CIN 2 or CIN 3, are not HIV infected, are not immunocompromised, and were not exposed to diethylstilbestrol in utero may extend the interval between cervical cytology examinations to every three years.

• Co-testing using the combination of cytology plus HPV DNA testing is an appropriate screening test for women older than 30 years. Any low-risk woman aged 30 years or older who receives negative test results on both cervical cytology screening and HPV DNA testing should be screened no sooner than 3 years subsequently.

• In women who have had a total hysterectomy for benign indications and have no prior history of high-grade CIN, routine cytology should be discontinued.

• Because cervical cancer develops slowly and risk factors decrease with age, it is reasonable to discontinue cervical cancer screening between 65 years and 70 years of age in women who have three or more negative cytology test results in a row and no abnormal test results in the past 10 years.

From American College of Obstetricians and Gynecologists. Cervical Cytology Screening. ACOG Practice Bulletin 109. Washington, DC: ACOG, 2009.

Paracentesis and ascitic fluid analysis

Also called: Abdominal Paracentesis; abdominal tap

How the test is done

Paracentesis

Ultrasound may be used to image the pooling of the fluid and locations of the abdominal organs and vascular tissues. This helps to avoid inadvertent puncture of these structures. Under local anesthesia, the physician inserts a long thin needle through the skin and into the peritoneal cavity. The insertion site is usually midline, about 2 inches (5 cm) below the umbilicus. Either a syringe or a three-way stopcock with polyethylene tubing is used to draw off the fluid. The diagnostic paracentesis takes 30 to 45 minutes to complete.

If the physician also wants to drain the peritoneal cavity of a large volume of ascitic fluid for therapeutic purposes, the nurse will assist in connecting sterile IV tubing to the needle or stopcock at one end and a large vacuum container at the other end (Figure 75). Volumes of 4 L or more may be collected.

Figure 75. Paracentesis. The three-way stopcock controls the direction of the flow of ascetic fluid into the syringe or the drainage tubing and collection container.

Interfering factors

• Coagulation disorder

• Intestinal obstruction

• Abdominal wall infection

• Uncooperative behavior

• History of multiple abdominal surgeries

• Portal hypertension

NURSING CARE

Pretest

• Because of the risk of bleeding, obtain the hematocrit, prothrombin time, partial thromboplastin time, and platelet values within 48 hours of this procedure. The laboratory values are entered into the patient ’s record and the nurse notifies the physician of abnormal results.

• After the physician has informed the patient about the procedure, and its risks and benefits, a signed consent is needed and is placed in the patient’s record.

• Before the procedure, the nurse records the patient’s baseline vital signs, including temperature. The patient’s weight and abdominal girth is also measured.

• Just before the procedure, have the patient void to empty the bladder completely. This helps prevent an inadvertent puncture of the organ during the procedure.

• The nurse positions the patient in full Fowler’s, supine, or lateral decubitus position according to the physician’s preference. The skin is cleansed, such as with povidone iodine solution, and a sterile drape is put into place.

During the test

• The nurse stands at the patient’s shoulder and provides reassurance to help alleviate fear. Some pain is felt by the patient as the needle penetrates the peritoneum. Encourage the patient to remain immobile.

• The nurse assists with the collection of the fluid. In addition, vital signs are taken and documented every 15 minutes. Because hypovolemic shock can occur when a large volume of fluid is removed, the nurse assesses the patient for signs of impending shock, including pallor, dizziness, diaphoresis (cold, moist skin, sweating), a rising pulse rate, and a falling blood pressure.

• Once the procedure is completed, the physician removes the needle, applies pressure and a small, sterile bandage to the puncture site. One or two sutures may be needed to close the opening.

Posttest

• Vital signs are taken immediately and at intervals thereafter until the patient is stable. The patient’s weight and measurement of abdominal girth are taken again, with a comparison to the pretest measurements. All data are recordedin the patient’s record. The nurse also documents the time that the paracentesis was done and the name of the physician who performed the procedure. The nurse describes the patient’s tolerance of the procedure. Generally, the patient feels better after the removal of excess fluid. Breathing is more comfortable and mobility improves. The nursing documentation includes the amount, color, odor, and characteristics of the fluid that was withdrawn. The amount of peritoneal fluid removed is also entered as output on the record of intake and output.

All specimens are labeled appropriately, including the patient’s name, identification number, date, physician’s name, and the identification of the specimen as peritoneal fluid. The collection bottles, specimens, and requisition form are sent to the laboratory, without delay.

• The dressing is checked for excess drainage or bleeding. With the removal of large amounts of fluid from the peritoneal cavity, there may be a rapid shift of fluid, albumin, and potassium from the blood to the peritoneal cavity. The nurse remains alert for hypotension, shock, and a rapid or irregular pulse as indicators of a serious shift of fluid and electrolytes.

• When the patient has the procedure done as an outpatient or in a medical office, he or she is taught to resume normal activities right away, but to restrict physical efforts for a few days. The patient maintains a dry sterile dressing on the puncture site for 5 to 7 days until the next visit with the physician. If the dressing becomes wet with small amounts of fluid leakage at the puncture site, the nurse shows the patient how to replace it with a dry bandage.

Parathyroid hormone

Also called: (PTH); Parathormone; Immunoreactive PTH

Specimen or type of test:

Serum, Plasma

Purpose of the test

A parathyroid hormone determination is performed to diagnose suspected parathyroid disorders. It may be performed to differentiate among clinical diagnoses that result in calcium and phosphate abnormalities. PTH is used as a biomarker for bone turnover for patients with kidney disease. High PTH indicates high bone turnover; however, lower levels are not reliable markers. PTH is used to manipulate plasma calcium and phosphate levels in chronic renal failure.

Basics the nurse needs to know

Parathyroid hormone is produced and secreted by the parathyroid glands. Its role in the body is the regulation of calcium. Its secretion is based on a negative feedback mechanism with calcium (Figure 76).

Figure 76. Regulation of parathyroid hormone (PTH) secretion.

Parathyroid hormone affects calcium levels by stimulating osteoclast activity and inhibiting osteoblast activity in the bone. This causes bone reabsorption, which shifts calcium and phosphate out of the bone into the blood. Parathyroid hormone also causes increased reabsorption of calcium at the kidney’s distal tubules and decreased reabsorption of phosphate at the proximal tubules. The result of parathyroid hormone activity is an increase in calcium in the blood with a decrease in plasma phosphate levels.

REFERENCE VALUES

(Interpreted in relation to serum calcium and phosphate levels)

Intact parathyroid hormone: 15-75 pg/mL or SI: 15-75 ng/L

N-terminal fraction: 50-330 pg/mL or SI: 50-330 ng/L

C-terminal fraction: 8-24 pg/mL or SI: 8-24 ng/L

How the test is done

Parathyroid hormone is measured by radioimmunoassay (RIA), which can measure biologically active intact parathyroid hormone. This fraction represents only a small portion of the total parathyroid hormone. Alternatively, RIA can measure C-terminal or N-terminal portions of the hormone. Two venous samples are needed.

Patch test, skin

Specimen or type of test:

Skin Sensitivity Test

Purpose of the test

This test is used to identify the particular allergen that causes contact dermatitis. It is also used to differentiate contact dermatitis from other causes of eczematous disease.

Basics the nurse needs to know

Allergic contact dermatitis causes an eczematous skin change. It is an inflammatory skin response that occurs when the skin is in contact with a particular antigen. The person is sensitized to the antigen over time, without the immediate development of a skin reaction. Eventually, reexposure to the antigen induces a vigorous allergic response at the site of contact with the antigen.

Because one part of the treatment of the skin eruption is to remove the antigen from further contact with the patient’s skin, the antigen must be identified. In some cases, a patch test is used to identify one or more suspected antigens by evoking a skin reaction to suspected allergens.

The patch test may be carried out by placing the suspected allergen, such as a small piece of clothing, a bit of a cosmetic substance, or a diluted solution of chemical components on the skin. Industrial substances or laboratory chemicals are never used in testing because they can produce an irritant dermatitis or a chemical burn. The most common allergens or sources of contact dermatitis are listed in the section of abnormal results.

The physician grades the results of the skin testing according to severity of the reaction. An erythematous (red), macular (flat), or papular (raised) lesion is labeled as an undecided, doubtful, or weak result. An erythematous, edematous, papular, or vesicular (fluid-filled) area of skin where a particular allergen was placed is identified as a strongly positive reaction. A raised, red, edematous area with large vesicles, bullae (fluid-filled blisters), or possible ulceration is identified as an extreme reaction.

REFERENCE VALUES

Negative; no abnormal skin reactions are noted.

How the test is done

Samples of selected allergens used by the patient or of a number of standard allergens are taped to the patient’s skin for 48 hours of contact exposure (Figure 77). The readings of the results are performed after 48 hours and again after 72 hours to 7 days, as prescribed.

Figure 77. Patch test, skin. Various allergens are applied to the skin of the patient’s back. Those substances that cause an allergic skin response are identified as sources of contact dermatitis.

Interfering factors

• Concurrent dermatitis from another source

• Exposure of the patch site to water or excessive perspiration

• Inaccurate interpretation of the results

• Inaccurate timing for reading of the results

NURSING CARE

Pretest

• Schedule this test after an episode of acute dermatitis has subsided and after treatment with corticosteroids has ceased. After the physician has informed the patient about the test, a written consent from the patient is needed. The consent is entered in the patient’s chart.

• If particular products that the patient uses are to be tested, instruct the patient to bring them in beforehand. The patch test must be prepared, and a detailed list of the ingredients must be written.

During the test

• The nurse or physician tapes the allergen patch to the patient’s upper back between the scapula and the spinal column. A diagram on paper is made to identify the location of each allergen.

Posttest

• Patient teaching.

The nurse instructs the patient to refrain from showers and physical exercise during the following 48 hours. This is because water and perspiration will loosen the tape of the patch. The patient is also told that if itching, irritation, or pain occurs under one of the discs of allergen, it should be removed immediately.

• Patient teaching.

The patient is instructed to return in 48 hours for the first evaluation of the results. The patch is removed at that time. After a 30-minute to 1-hour wait, the skin is assessed for any reaction in the area of the allergens. The nurse instructs the patient to return for the second appointment to reevaluate the skin because a delayed reaction can occur. This second reading is done at 96 hours (4 days) after the patch is applied. The patient is advised that exercise and showers are permitted while waiting for the second evaluation, but that soap must not be used, and that the patient must not scrub, scratch, or rub the skin in the test area.

Percutaneous umbilical blood sampling

Also called: PUBS; Cordocentesis

Specimen or type of test:

Blood

Purpose of the test

This procedure primarily is used to obtain a specimen of fetal blood for the assessment of Rh isoimmunization, a fetal anemia. It may also be used to identify chromosomal abnormality, detect fetal infection, measure acid-base balance, and to detect other hematologic abnormalities.

A small amount of the fetal blood is reserved for a complete blood count.

Basics the nurse needs to know

The percutaneous umbilical blood sampling can be performed in the second or third trimester. The normal values of fetal cord blood vary based on the gestational age of the fetus. Because of the risk of fetal death that can occur after the PUBS procedure, the test is reserved for conditions that require rapid diagnosis or to obtain data about the fetus’ condition that cannot be obtained in any other way.

Fetal blood analysis

Red cell isoimmunization

This occurs when the fetus has Rh-positive red blood cell antigens and the mother has Rh-negative erythrocytes. The maternal antibodies are transmitted to the fetus and cause fetal hemolysis of erythrocytes. If the erythrocyte incompatibility is not prevented or controlled, the fetus experiences a hemolytic anemia called erythroblastosis fetalis or Rh disease. The fetal cord blood is tested for blood type, the presence of Rh antigens, the hematocrit level, and the reticulocyte count. The treatment is individualized, but an intrauterine blood transfusion can be given to the fetus.

Prenatal chromosomal analysis

The karyotype consists of the characteristics of the chromosomes, their number, form, size, structure, and grouping. Chromosomal abnormality in the fetus is identified by analysis of the fetal blood cells using chromosomal-specific DNA probes.

Congenital infection

Infection in the pregnant woman can cross the placental barrier and infect the fetus. The fetal blood analysis for infection includes measurement of fetal antibodies, white blood cells, eosinophils, liver enzymes, and platelets. Viral culture of the fetal blood and the amniotic fluid may be performed to identify the infectious organism. Because fetal antibodies do not develop until the 22nd week of gestation, fetal cord blood samples cannot verify the infection before this time.

Thrombocytopenia

This is a low platelet count, which can cause fetal intracranial bleeding during pregnancy, labor, or the neonatal period. In most cases, the mother has immune thrombocytopenia and passively transmits the maternal antiplatelet antibodies to the fetus. If the fetus is affected severely, the fetus can receive an intrauterine platelet transfusion, administered via the umbilical vein.

REFERENCE VALUES

Hematologic evaluation: Within normal limits for gestational age

Chromosomal analysis: Normal karyotype

Biochemistry analysis: Within normal limits for gestational age

Immunoglobulin G (IgG) antibodies: Within normal limits

IgM antibodies: Within normal limits

Hemoglobin

Fetus of 18-20 weeks 11.47 ± 0.78 g/dL or SI: 115 ± 7.8 g/L

Fetus of 21-22 weeks 12.28 ± 0.89 g/dL or SI:123 ± 8.9 g/L

Fetus of 23-25 weeks 12.40 ± 0.77 g/dL or SI: 124 ± 7.7 g/L

Fetus of 26-30 weeks 13.35 ± 1.17 g/dL or SI: 134 ± 11.7 g/L

RBC

Fetus of 18-20 weeks 2.66 ± 0.29 × 10⁶ cells/μL or SI: 2.66 ± 0.29 ×¹² cells/L

Fetus of 21-22 weeks 2.96 ± 0.26 × 10⁶ cells/μL or SI: 2.96 ± 0.26 ×¹² cells/L

Fetus of 23-25 weeks 3.06 ± 0.26 × 10⁶ cells/μL or SI: 3.06 ± 0.26 ×¹² cells/L

Fetus of 26-30 weeks 3.52 ± 0.32 × 10⁶ cells/μL or SI: 3.52 ± 0.32 ×¹² cells/L

Hematocrit

Fetus of 18-20 weeks 35.86 ± 3.29% or SI: .036 ± 0.03 volume fraction

Fetus of 21-22 weeks 38.53 ± 3.21% or SI: 0.39 ± 0.03 volume fraction

Fetus of 23-25 weeks 38.59 ± 2.41% or SI: 0.39 ± 0.03 volume fraction

Fetus of 26-30 weeks 41.54 ± 3.31% or SI: 0.42 ± 0.03 volume fraction

How the test is done

Guided by ultrasound imaging, the physician inserts a sterile 20- to 22-gauge spinal needle through the maternal abdomen and uterus. The needle is then advanced into the umbilical cord until it is placed in one of the umbilical veins (Figure 78). Once the needle placement is verified, a syringe is used to aspirate 0.5 to 3 mL of venous blood. The blood is then transferred to microtubes for specific laboratory analyses.

Figure 78. Percutaneous umbilical blood sampling. Under ultrasound guidance, the needle is advanced through the skin and into the uterus. Once the needle punctures the umbilical cord and one of the umbilical veins, a small amount of cord blood is aspirated into the syringe.

Interfering factors

• Maternal obesity

• Uncooperative behavior

• Severe polyhydramnios

• Unfavorable fetal position

• Specimen contamination

NURSING CARE

During the test

• The nurse cleanses the woman’s abdomen with the appropriate povidone-iodine or surgical soap solution, and then places the surgical drape. As the physician administers the local anesthetic, the nurse provides reassurance to the patient. The injection causes a slight stinging sensation in the abdominal area.

• The nurse begins the frequent assessment and recording of the fetal heart rate. The fetal cardiac contractions can be counted during the imaging of the fetus on the ultrasound monitor.

• Prepare any additional medications, as prescribed. If the fetus moves excessively, the mother may receive intravenous sedation to limit fetal movement. As an alternative, the fetus may receive an intravenous sedative or muscle relaxant via the umbilical vein.

• Once the blood is obtained, the nurse assists with depositing it in the microtubes. Ensure that all blood samples are properly labeled with the patient ’s name, identification number, age, physician’s name, date and that the specimen is fetal blood (cord blood). The requisition form with its identifying information also states that the specimen is fetal blood (cord blood) obtained by percutaneous umbilical cord sampling. The gestation of the pregnancy is included.

Posttest

• Once the needle is removed, the nurse begins to monitor the fetal heart rate and takes the mother’s vital signs. In the recovery area, external fetal monitoring of the fetal heart rate and uterine contractions continues. It is common for the mother to have mild uterine cramping for a short while. The fetal monitoring is discontinued when the fetal heart rate remains stable in a normal range and the uterine contractions cease.

• At regular intervals, the nurse observes the abdomen for signs of bleeding. The small sterile dressing that covers the puncture site should remain dry and intact.

• Prophylactic antibiotics are administered, as prescribed. If indicated, the nurse also administers prescribed Rh_o(D) immune globulin (RhoGAM) to the Rh-negative mother. This will help prevent Rh disease of the newborn in a future pregnancy.

• Patient teaching.

In preparation for discharge, the nurse instructs the patient to rest for the remainder of the day. The patient should take her temperature at least two times per day. She should report a fever to her physician without delay. She is instructed to return to the physician for a follow-up evaluation and to learn the test results.

• Patient teaching.

When serious or severe chromosomal abnormality exists, the parents experience emotional distress. Genetic counseling is an essential component of care before testing and after the test results are known. This helps the parents make an informed choice about the continuation of the pregnancy. In obstetric management, the alternatives include continuation or termination of the pregnancy. If the pregnancy is continued, plans are made for intensive antepartal monitoring, for possible cesarean section for fetal distress during labor, and for the special postdelivery needs of the newborn.

♦ Nursing response to complications

The PUBS procedure is a potential risk for the fetus, with a fetal death rate of 1.6%. Continued bleeding from the puncture of the umbilical vein is the probable cause. Many patients do have minimal bleeding that ceases a few minutes after the needle is removed, but more severe bleeding can occur. Other complications include fetal bradycardia, maternal or fetal infection, and premature labor. The nurse assesses for complications and notifies the physician of abnormal findings.

Bleeding.

Prolonged bleeding from the umbilical cord is identified by continued staining or wetness from amniotic fluid on the mother’s abdominal dressing. The drainage is pink. Fetal movements may be hyperactive or lethargic.

Fetal bradycardia.

Fetal bradycardia can be observed on the fetal monitor. Bradycardia is identified by a fetal heart rate less than 120. In addition, the fetus is lethargic, with fewer than normal movements.

Maternal infection.

If the mother develops infection, she experiences chills and fever. She also may have uterine cramping. The nurse monitors the patient’s temperature and examines the abdomen for signs of redness, swelling, or purulent drainage. If the fetus develops an infection, it is lethargic, with fewer than normal movements.

Premature labor.

Premature labor may develop, as characterized by uterine contractions recorded on the fetal monitor. The mother may complain of backache, uterine cramping, or rhythmic contractions. There may be leakage of amniotic fluid from the vagina because of premature rupture of the membranes.

Perfusion studies, cardiac

Also called: Nuclear myocardial scans, perfusion imaging, thallium scan, myocardial perfusion imaging

Specimen or type of test:

Nuclear Imaging

Purpose of the test

Nuclear scanning or radionuclide imaging of the heart is done to determine the severity and location of coronary stenosis, the viability of the myocardium, to identify those at risk for an infarction and to determine treatment options for patients with coronary artery disease (CAD).

Basics the nurse needs to know

Varying techniques may be used to noninvasively assess the ability of the coronary arteries to maintain perfusion to the heart. These include single-proton emission computed tomography (SPECT) and positron emission tomography (PET). The procedure may be done at rest (no physiologic demand) or at stress (induced physiologic demand)

SPECT involves the use of a gamma camera, which produces a 3-dimensional image of the heart. The camera rotates around the patient and multiple images are obtained. It can accurately stratify patients at risk. It can locate sites of perfusion abnormalities. PET scans permit assessment of coronary artery disease, especially metabolic and chemical changes, which result in perfusion problems. While it has higher specificity than SPECT images, PET scans are more costly and have greater radiation exposure.

Commonly used radionuclides for these scans are thallium 201, Tc-99m sestamibi, and Tc-99m tetrofosmin. Thallium was the first agent used in myocardial perfusion studies, but Tc-99m (sestamibi or tetrofosmin) provide better gamma camera imaging.

Dual isotope imaging may also be done. While patient is at rest, thallium is given. Then exercise is done and sestamibi is given followed by a second set of images. The timing of the rest and poststress imaging varies with hospital protocols.

REFERENCE VALUES

Normal myocardial perfusion; no “cold” spots

How the test is done

SPECT scanning is performed with an Anger gamma camera combined with a computer. Continuous counts of emitted photons are made during the cardiac cycle. The scan identifies “cold” spots, areas of decreased uptake. Cold spots identify areas of ischemia and infarction. The radioisotope can be given under a state of no physical demand, which is known as a resting study, or it can be done after inducing stress on the heart, which is called stress imaging.

Stress on the heart may be induced by exercise or by pharmacologic agents. Stress imaging is done because blood flow abnormalities may not be evident at rest. Stress imaging distinguishes ischemic sites from infarcted areas.

Significance of test results

Abnormal values

Cold spots indicate and distinguish areas of infarction and ischemia.

Interfering factors

NURSING CARE

When a SPECT study is done:

Pretest

• Usually, long-acting nitrates are held for 8 to 12 hours before the test.

• Calcium channel blockers and β-blockers are held

• The patient fasts for 4 to 6 hours before the test but may drink water.

During the test

• The patient is placed supine on the table with arms over the head.

• The radiopharmaceutical agent is give intravenously and multiple scintigraphic images are taken.

• Stress is induced by exercise or a pharmacologic agent. A treadmill is preferred over a bicycle. Bruce or a modified Bruce protocol is used. The Bruce protocols are multistage maximal treadmill programs broken into 3-minute intervals. Between stages there is an increase in the grade (incline) of the treadmill. The radiopharmaceutical agent is given intravenously at peak stress. Exercise is continued for 30 to 60 seconds.

• If the patient is unable to perform an exercise stress test, pharmacologic stress may be induced with the intravenous administration of dipyridamole, adenosine, or dobutamine. Dobutamine is only used if the others are contraindicated.

• Dipyridamole may be given orally or intravenously, although intravenous is preferred. Imaging agent is given 3 to 4 minutes after the dipyridamole infusion is complete. Observe patient response. If pain, headache, dizziness, flushing, or nausea occurs, aminophylline may be ordered to relieve symptoms.

• Adenosine is given intravenously. The imaging agent is given halfway through the adenosine infusion. Common patient responses include flushing, shortness of breath, and chest pain. Reassure patients that these symptoms are transient. Heart block may also occur and is relieved when the infusion is stopped.

• If dobutamine is given, it is administered intravenously. The imaging agent is given during the infusion. The patient may complain of palpitations, chest pain, and flushing. Premature ventricular contractures may be observed. Less common is the incidence of ventricular tachycardia and atrial fibrillation.

• After the completion of the stress test, the patient is placed supine on the table and multiple scintigraphic images are taken.

Posttest

• Assess the patient’s response.

• Three to 4 hours later, the patient may return for a repeat scan.

Pericardiocentesis

Also called: Pericardial fluid analysis

Specimen or type of test:

Pathology

Purpose of the test

Analysis of pericardial fluid is performed to determine the cause of and appropriate therapy for acute pericarditis, subacute effusive-constrictive pericarditis, neoplastic pericardial disease, and pericardial effusion of unknown cause.

Basics the nurse needs to know

Pericardiocentesis is a diagnostic and therapeutic procedure in which the pericardial space is accessed with a needle or cannula, and fluid is aspirated (Figure 79). For diagnostic purposes, the fluid is then analyzed. For therapeutic purposes, either fluid is drained on a one-time basis or a catheter is inserted and left in place for 1 to 48 hours (rarely, it may be kept in for 72 hours).

Figure 79. Pericardiocentesis.

(From Custalow CB: Color atlas of emergency department procedures, Philadelphia, 2005, Saunders.)

Normally, the pericardial space between the visceral and parietal pericardium contains approximately 20 to 50 mL of clear serous fluid. If the pericardium becomes inflamed, diseased, or is disrupted, a pericardial effusion may occur. As fluid builds up in the pericardial space, cardiac tamponade may result. Cardiac tamponade will eventually lead to a decrease in cardiac output, with an increase in right atrial pressure, pulsus paradoxus, and hypotension. If progressive and untreated, cardiac tamponade will result in death.

REFERENCE VALUES

Pericardial fluid is sterile, clear, and colorless or straw-colored.

How the test is done

Pericardiocentesis for diagnostic purposes is not an emergency situation and can be performed in the controlled environment of an operating room or special procedure room. The procedure begins after skin preparation and infiltration of a local anesthetic, usually 1% lidocaine without epinephrine. A small incision is made in the skin, the site being determined by the desired approach.

The physician inserts a needle and approximately 20 mL of fluid is removed for analysis. Echocardiography is used to guide the needle into the pericardial sac. See Echocardiography, pp. 270. If cytologic studies are performed, a heparinized container is necessary. The fluid is usually analyzed for color; hemoglobin concentration; hematocrit value; red blood cell, white blood cell, and differential counts; and protein and glucose determinations. In addition, Gram stains and culture, fungal stains and culture, and cytologic studies are performed. Additional fluid is removed if viral and parasite studies, immunologic and serologic screens, or lipoelectrophoresis are planned.

If therapeutic pericardiocentesis is desired after the specimens are obtained, a catheter is inserted and positioned to allow drainage.