Abnormal labs: To treat or not to treat

Tampa, Fla—Laboratory tests performed on patients receiving chemotherapy often fall outside normal parameters, necessitating modifications to the plan of care.

“To reduce and delay treatment decreases the chance of a cure,” said Catherine Kefer, MSN, APRN, BC, ANP, an oncology nurse practitioner at Southern Illinois University in Springfield, at the Oncology Nursing Society’s Institutes of Learning.

Ms Kefer; Robert S. Mocharnuk, MD, an associate professor of clinical medicine at the SimmonsCooper Cancer Institute at Southern Illinois University; and Wendy H. Vogel, MSN, FNP, AOCNP, an oncology nurse practitioner at Kingsport Hematology Oncology Associates in Kingsport, Tenn, discussed common lab abnormalities and interventions that might allow treatment to continue.

Clinicians must determine if the abnormal laboratory studies are related to treatment or the disease, Ms Kefer advised. For instance, elevated liver or renal function tests could indicate disease or drug-associated damage. If it’s disease related, she recommended treating the patient and giving supportive care, but if therapy is the cause, it may require a dose reduction or holding the chemotherapy.

“Sometimes it’s clear cut, sometimes not,” she cautioned.

Complete blood counts

Ms Vogel encouraged nurses to know the normal ranges of labs and to keep in mind what a patient’s baseline results were when reviewing lab reports.

Clinicians use white blood cell counts to monitor response to therapy and to assess for the presence of infection or inflammation, Ms Vogel said. The differential is important for interpreting the results.

White cells can increase in response to stress but return to normal in about an hour. Smoking increases the count due to the chronic lung inflammation it produces. Medications, including herbs, can alter the count, so she urged nurses to ask about everything the patient is taking.

Chemotherapy, alcohol use, cachexia, and AIDS can lower white blood cells, with chemotherapy the most common cause of neutropenia, a low neutrophil count. The drugs kill rapidly reproducing cells, including healthy white cells.

The oncologist or oncology advanced practice nurse will determine the lowest level he or she considers safe to administer chemotherapy, but as a general rule, Ms Vogel said, the drug will be held when the absolute neutrophil count drops below 1,500. The nadir, the lowest point in the blood count, will occur within 10 to 14 days of administration for most drugs. A growth factor may be given to high-risk patients to prevent febrile neutropenia.

Cancer also can affect red blood cell levels, resulting in anemia due to inflammatory cytokines released by the tumor or the therapy, decreased erythropoiten production in the kidneys, or impaired iron utilization. During the 1990s, erythropoiten stimulating agents (ESA) frequently were used to treat anemia in cancer patients, but more recent research has associated their use with worse outcomes.

Now, if the treatment goal is curative, providers will transfuse rather than start patients on an ESA, Ms Vogel reported. However, if the goal is palliative, ESA may be used. Whether to transfuse depends more on how the anemia is affecting the patient’s life.

“We don’t treat the numbers; we treat the patient,” Ms Vogel advised. 

Platelet counts are often low in patients receiving chemotherapy. Ms Vogel said patients often do well even with low platelet levels. Patients should avoid activities that could lead to trauma, always wear shoes, and use a soft toothbrush. Nurses should not use a blood pressure cuff on the patient and not perform invasive procedures.

Chemistries

Cancer patients also can develop abnormal electrolyte levels, such as hypernatremia related to dehydration, and renal and kidney function indicators, including blood urea nitrogen, creatinine, and liver enzymes.

Clinicians treat the dehydration causing the hypernatremia. Liver enzymes should come down once treatment ends, unless there is liver metastasis, Ms Kefer said.

“There are no guidelines for dose reduction or holding drugs for liver or renal abnormal test results,” Ms Kefer added.

Hypercalcemia of malignancy may occur with bone cancer, metastasis to the bone, greater amounts of calcium absorbed from the bone, or an inability of the kidneys to excrete excess calcium. Treatment focuses on correcting the cause, hydrating the patient, and medicating to inhibit bone reabsorption.

Tumor lysis syndrome results in hyperkalemia, hyperphosphatemia, and hypocalcemia. Treatment involves hydration, alkalinization of the urine, allopurinol, and treatment of the hyperkalemia.

The syndrome of inappropriate antidiuretic hormone hypersecretion may be disease or chemotherapy related. The body retains excess water and develops hyponatremia. Treatment focuses on correcting the underlying problem and includes fluid restriction, diuretics, demeclocycline and hypertonic saline, if severe neurologic symptoms are present.