L

L




Lactate dehydrogenase (LDH)


See Cardiac Markers on p. 175.



Lactate dehydrogenase, isoenzymes


See Cardiac Markers on p. 175.



Lactic acid


Also called: Lactate; l-Lactate; Blood Lactate




Specimen or type of test:


Venous



Purpose of the test


Lactate levels are most frequently used to support the diagnosis of cellular hypoxia. Lactate levels can also predict survival in severe shock states.



Basics the nurse needs to know


Elevated lactic levels cause a form of metabolic acidosis called lactic acidosis. Lactate levels in the blood result from the balance of production and clearance. There are two types of lactic acidosis. Type A lactic acidosis is due to a lack of cellular oxygenation. If the cells do not receive adequate oxygen, anaerobic metabolism will occur. Lactic acid is the by-product of anaerobic metabolism. Rising lactate levels indicate a need to examine O2 transport and consumption. Type B lactic acidosis is due to the overproduction and/or decreased ability of the liver to remove lactate.




REFERENCE VALUES


8.1-15.3 mg/dl or SI: 0.9-1.7 mmol/L







image Critical values


>4 mmol/L



How the test is done


A venipuncture is performed. Arterial blood may also be used, but there is no significant difference between arterial and venous lactate measures.


For shock states, a random sample may be obtained.



Significance of test results






Elevated values



Type A



Shock states

Severe hypoxia

Severe anemia

Prolonged seizures/shivering

Mesenteric ischemia


Type B



Alcoholism

Diabetes mellitus

Liver failure

Malignancy

Renal failure

Many medications: metformin, salicylates carbonic anhydrase inhibitors


Decreased values



Hypothermia


Interfering factors



• Noncompliance with dietary and activity restrictions

• The drugs acetaminophen (large dose), ethanol (large dose), epinephrine, fructose, morphine, and sorbitol



NURSING CARE


Nursing measures are similar to those used in other venipuncture procedures (see Chapter 2), with the following additional measures.



Pretest





•   Patient teaching.


The nurse instructs the patient not to eat or drink for 12 hours before the test and to ingest no alcohol for 24 hours before the blood is drawn.



•   Patient teaching.


Instruct the patient to lie quietly for 2 hours before the blood is drawn.


• For shock states, a random sample may be obtained.


During the test



• No tourniquet should be applied, and the patient should not clench the fist.


Posttest



• Send the specimen to the laboratory immediately.

• Advise the patient to resume a normal diet and activity level.





image Nursing response to critical values


High lactate levels (>4 mmol/L) indicate higher mortality rates. Report elevated values to the physician.



Lactose tolerance test




Specimen or type of test:


Blood, Urine



Purpose of the test


This test identifies lactose intolerance-lactate deficiency. It is used in the workup for abdominal distention, chronic diarrhea, and abdominal cramps associated with the ingestion of milk. It is also used to investigate the cause of malabsorption.



Basics the nurse needs to know


Lactose is a sugar present in milk and milk products. For the intestinal absorption of lactose, the person must have lactase enzymes to break down the lactose into simpler sugars. These sugars are then absorbed through the villi of the small intestine and enter the blood circulation. This process results in a normal rise of the plasma glucose level to greater than 30 mg/dL (SI: >1.7 mmol/L) over the normal fasting value of glucose.


When the lactase enzyme is deficient, the client is lactose intolerant. Varying amounts of lactose cannot be absorbed and the sugar remains in the lumen of the intestine. Sugar attracts water into the lumen by osmosis, causing diarrhea. Bacterial fermentation of the sugar causes gas formation, bloating, abdominal cramps, and distention. The lactose intolerance may range from mild to severe, and often worsens with aging.




Abnormal findings


Glucose measurements

With lactase deficiency, only some of the simple sugar is absorbed and reaches the blood. There is a small increase in the plasma glucose, but it does not reach the reference value of this test. In the lactose tolerance test, the abnormal findings are described as a flat glucose curve or a decreased plasma glucose value. The test is often repeated 2 days later and the higher test result is the one that is used for diagnosis.


Abnormal test results may not indicate lactose intolerance, but can be the result of other causes of intestinal malabsorption or inflammatory disease.




REFERENCE VALUES


Plasma glucose: (an increase over the fasting serum glucose value)


>30 mg/dL or SI: >1.7 mmol/L



How the test is done



The fasting patient takes an oral dose of lactose mixed with 400 mL of water.

Venipuncture is used to take serial blood samples at timed intervals for 90 minutes.


Significance of test results



Lactose intolerance

Crohn’s disease

Ulcerative colitis

Small bowel resection

Sprue

Viral or bacterial bowel infection

Giardiasis


Interfering factors



• Failure to maintain dietary restrictions

• Delayed emptying of the stomach

• Vomiting

• Diabetes mellitus



NURSING CARE


Nursing measures are similar to those used in other venipuncture procedures (see Chapter 2), with the following additional measures.



Pretest





•   Patient teaching.


Instruct the patient to discontinue food intake for 8 hours before the test. In addition, there can be no eating during the test since food would alter the baseline glucose value. There can be no smoking or gum chewing before or during the test because these activities would alter the gastric motility and gastric emptying; both would alter the test results.



During the test



• Assess the patient for any signs of watery diarrhea, abdominal cramps, or nausea because the dosage of lactose can exacerbate symptoms.


Posttest



• The patient can resume eating in 2 hours, after all the blood test samples are obtained.

• For the patient who is medically diagnosed with lactose intolerance, there is a need for nutritional instruction to modify the diet. The goals are to alleviate the abdominal symptoms and, at the same time, maintain calcium intake.




•   Patient teaching.


If the patient is diagnosed with lactose intolerance, the nurse or dietitian can teach the patient to restrict the intake of milk (lactose). Milk and food that contain milk or milk products cause varying degrees of abdominal discomfort among people. A lactase enzyme supplement may be helpful, but does not substitute for lactose restriction in the diet. The patient should also be taught that many nondairy foods contain lactose, including bread, baked goods, and biscuit and pancake mixes, among others. The nurse also teaches the patient to read the ingredient labels to avoid hidden sources of lactose.


• Most adults can tolerate 8 to 12 oz (1 glass) of milk daily and should be encouraged to continue ingesting the amount that can be tolerated. This will provide some calcium and other needed vitamins and minerals (A, D, riboflavin, and phosphorus). Soy and rice milk are tolerated well. Calcium supplementation in tablet form can be given so that the patient receives 1200 to 1500 mg of calcium per day.


Laparoscopy, pelvic


Also called: Peritoneoscopy




Specimen or type of test:


Endoscopy



Purpose of the test


Laparoscopy is used to investigate the cause of pelvic pain, to detect infected fallopian tubes, endometriosis or an ectopic pregnancy, to identify a pelvic mass, or to determine if cancer is present.



Basics the nurse needs to know


The laparoscope is a fiberoptic endoscope used to visualize the size and shape of the ovaries, uterus, and fallopian tubes. The peritoneal cavity and peritoneum are observed for signs of infection, abscess, or adhesions. Biopsy of abnormal tissue may be performed.




REFERENCE VALUES


No abnormalities of the ovaries, fallopian tubes, uterus, or peritoneal cavity are noted.



How the test is done


When general or regional anesthetic is used, the surgeon inflates the peritoneal cavity with 2 to 3 L of carbon dioxide. When local anesthetic and conscious sedation are used, the abdomen is insufflated with nitrous oxide gas. The gas distends the abdominal wall and provides space for the instruments. The laparoscope is inserted through a small incision just below the umbilicus, and the organs are visualized. If a biopsy, culture, or other surgical procedure is performed, a second incision is made in the lower abdomen for insertion of additional instruments.



Significance of test results






Abnormal values



Ovarian cyst

Endometriosis

Ectopic pregnancy

Uterine fibroid tumors

Pelvic abscess

Pelvic inflammatory disease

Adhesions

Abnormality of the fallopian tubes

Malignancy


Interfering factors



• Failure to maintain a nothing-by-mouth status

• Obesity

• Adhesions

• Anticoagulation therapy



NURSING CARE



Pretest



• After the patient has been informed about the procedure by the physician, the nurse obtains written consent from the patient and places the form in the patient’s record. Ensure that all preoperative laboratory work is completed and that the results are posted in the record.




•   Patient teaching.


The nurse instructs the patient to discontinue all food and fluids for 8 hours before the procedure is performed.


• At the time of the surgery, the patient removes all clothes and puts on a hospital gown. The nurse identifies the patient by two forms of identification. Vital signs are taken and recorded, including temperature, blood pressure, pulse, and respirations. The nurse also verifies that the patient has not had anything to eat or drink in the past 8 hours.


During the test



• The nurse places the patient in the lithotomy position, with the legs supported in stirrups.

• An indwelling catheter is inserted into the bladder and connected to the urinary collection system. This keeps the bladder deflated and protects it from trauma or injury.

• The nurse provides reassurance to the patient until the anesthetic is administered.

• If a biopsy specimen is obtained, place the tissue in a glass container with preservative. The label is applied directly to the container with the patient’s name, identification number, the physician’s name, date, procedure, and type of the tissue. The requisition form has the same identifying information..


Posttest



• The nurse assesses the patient by monitoring the vital signs every 30 minutes for 4 hours or until they are stable. The small dressing(s) should remain dry and intact. Once the urinary catheter is removed, the nurse monitors the patient for resumption of voiding and urinary output.

• Once the patient is alert, the nurse encourages ambulation and the oral intake of fluids. Carbonated beverages are avoided for 24 to 36 hours. With the excess carbon dioxide in the abdomen, the intake of carbonated beverage can cause vomiting.

• The nurse provides pain medication as needed. Some pain in the abdomen and shoulder is to be expected for 24 to 36 hours. The cause is the carbon dioxide gas, which will gradually be absorbed and exhaled from the lungs.




•   Patient teaching.


The nurse instructs the patient to restrict physical activity for a few days until the incisions are healed. The patient is taught to notify the physician of increasing abdominal pain, fever, or abnormal drainage.



Lead, blood


Also called: Pb




Specimen or type of test:


Blood



Purpose of the test


This test is used to detect and measure the level of lead in the blood. It is also used as a screening test for people who are at risk for elevated lead levels.



Basics the nurse needs to know


Lead is a heavy metal in the environment that can enter the human body orally, through respiration of dust that contains lead, and by absorption through the skin. Plumbism, or lead toxicity, can occur as an acute condition because of recent exposure, or as a chronic accumulation of lead, over time. An elevated lead level in the body is highly toxic, causing damage to the bone marrow, the neurologic system, and kidneys. The blood test is able to measure recent exposure to lead but cannot evaluate the amount of lead already deposited in tissues from past exposure.


In children, the primary source of elevated lead levels is exposure to lead-based paint. The risk is highest for children of low socioeconomic status and with a history of inadequate nutrition including a lack of iron, calcium, and zinc. When a child is screened for a blood lead level, a value of greater than 45 to 69 μg/dL (SI: >2.17-3.33 μmol/L) indicates substantial exposure. At this level, current CDC guidelines for children recommend that an environmental investigation and control of hazard be done within 48 hours and that chelation therapy for the child be started immediately to help remove the lead from the body.


The majority of adults who have high blood lead levels were exposed through their work. Occupational exposure includes manufacturing of storage batteries, mining of lead and zinc ores, smelting, painting, wall paper hanging, and renovation, restoration or demolition of old houses (CDC, 2009). Based on Occupational Safety and Health Administration (OSHA) requirements, the adult with an occupational exposure and a blood lead level of greater than 50 mcg/dL (SI: >2.20 μmol/L) should be removed from the work setting to undergo medical evaluation and possible chelation therapy.




REFERENCE VALUES


Infant and Child: <10 μg/dL or SI: <0.48 μmol/L


Adult: <25 μg/dL or SI: <1.21 μmol/L







image Critical values


Children and Adult: >69 μg/dL or SI: >3.33 μmol/L



Toxic concentration


100 μg/dL or higher or SI: 4.83 μmol/L or higher



How the test is done



Venipuncture is used to collect a sample of blood.


Significance of test results



Exposure to lead

Lead toxicity, acute


Interfering factors



• None



NURSING CARE


Nursing measures are similar to those used in other venipuncture or capillary puncture procedures (see Chapter 2), with the following additional measures.



Pretest



Health promotion

For routine screening, the Centers for Disease Control and Prevention (CDC) currently recommends that all children ages 1 to 6 have an annual screening for lead levels. The nurse can teach parents the importance of the test and the need to detect lead content in the child’s body at an early stage.



Posttest



• When the lead level is elevated, the nurse should assess the patient for signs of toxicity. At low to moderate levels of lead in the blood, the child will develop loss of some mental acuity, developmental lags, hearing loss, and growth delay. At moderate elevations, the child develops anemia, abdominal colic, and neuropathy. A nutritional assessment may also be indicated. In the adult, moderate elevations cause an elevation of the systolic blood pressure, a loss of hearing, infertility, and neuropathy.




•   Patient teaching.


The nurse can teach the patient or family members about the sources of lead that may be in the patient’s environment and the importance of removing the contaminants. The nurse can also advise the family to seek the assistance of the local health department regarding detection of the sources of lead exposure and advice on how to correct the problem.



image Nursing response to critical values


At a blood lead level of 69 μg/dL (SI: >3.33 μmol/L) or higher, the patient is at serious risk for developing severe anemia and neurologic damage. The patient must be admitted to the hospital and undergo immediate chelation therapy for acute lead poisoning. The nurse notifies the physician of this elevated result.



Leukocyte count


See White Blood Cell Count on p. 637



Lipase




Specimen or type of test:


Blood



Purpose of the test


Lipase is a test to diagnose acute pancreatitis and can identify other sources of pancreatic disease.



Basics the nurse needs to know


Lipase is a pancreatic enzyme needed to help digest fatty acids. In pancreatic inflammation, this pancreatic enzyme cannot flow into the intestine because of inflammation or blockage in the pancreas, pancreatic duct, common bile duct, or intestine. Once there is obstruction of the flow, the lipase is secreted into the blood and the serum level rises. In pancreatic disorders, both serum lipase and serum amylase values are elevated on the first day of acute pancreatitis, but the lipase remains elevated in the blood for a few days longer than amylase.




REFERENCE VALUES


Adult: <200 units/L or SI: <3.4 μkat/L

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Feb 18, 2017 | Posted by in NURSING | Comments Off on L

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