Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_208_библиотеки_им_акад_М_И_Перельмана
.pdf
42 Laboratory Medicine in Psychiatry and Behavioral Science
Blood gases
Type of test Blood (arterial)
Background and explanation
of test
A sampling of blood gases reveals the amount of dissolved
oxygen and carbon dioxide (CO
2
) in arterial blood along with
information on acid-base status and a measure of how well
oxygen is carried to the body. The partial pressure of carbon
dioxide (PaCO
2
) reflects the degree of alveolar ventilation.
The partial pressure of oxygen (PaO
2
) reflects the status of
alveolar gas exchange with inspired air. Oxygen saturation
(SaO
2
) is the percentage of oxygen bound to hemoglobin and
thus available for transport.
Relevance to psychiatry and Several psychiatric and psychotropic-related conditions re-
behavioral science sult in blood gas abnormalities. Patients with CO
2
retention
because of chronic obstructive pulmonary disease (COPD)
can develop severe somnolence or confusional states, par
-
ticularly after a sedative such as a benzodiazepine is given. In
anxiety states, hyperventilation is both a cause of respiratory
alkalosis and a symptom of the condition and can be accom
-
panied by paresthesias, muscle twitching and spasm, diz-
ziness, palpitations, and seizures. Understandably, patients
may become panicked, with further escalation of symptoms.
Salicylate overdose causes overbreathing and respiratory
alkalosis. Opioid or barbiturate overdose causes under-
breathing and respiratory acidosis.
Preparation of patient Potential complications of arterial puncture (bleeding, hema-
toma, infection, nerve damage, occlusion) should be ex-
plained to the patient. A test for collateral circulation such as
a modified Allen test is recommended prior to the procedure.
Indications •
Evaluating oxygenation or acid-base status
•
Evaluating patients with dyspnea or respiratory distress
• Evaluating patients with hea d o r n ec k tr au ma tha t c oul d
compromise breathing
• Monitoring the effectiveness of oxygen therapy or arti-
ficial ventilation
• Monitoring the effects of prolonged anesthesia
• Workup of delirium or other mental status changes
• Workup of hyperventilation in patients with severe
anxiety
• Workup of hypoventilation in overly sedated patients
Reference ranges pH 7.35–7.45
PaCO
2
35–40 mmHg
PaO
2
80–100 mmHg
HCO
3−
22–31 mEq/L
SaO
2
96%–100%
Critical value(s) pH ≤ 7.2 or >7.6
PaCO
2
<20 mmHg
https://t.me/med1917
43 Laboratory Tests
Blood gases (continued)
Critical value(s) (continued) PaO
2
<40 mmHg
HCO
3−
<10 mEq/L
SaO
2
<60%
Abnormal test Respiratory acidosis: pH low, PaCO
2
high; due to underbreath-
ing or poor gas exchange. Causes include COPD, pneumonia,
COVID-19 infection, asthma, airway obstruction, myasthenia
gravis, and oversedation by medications such as benzodiaz
-
epines or opioids.
Respiratory alkalosis: pH high, PaCO
2
low; due to hyperventi-
lation. Causes include anxiety or emotional distress, TBI,
pain, aspirin overdose, and certain lung diseases.
Metabolic acidosis: pH low, HCO
3–
low; due to metabolic or
renal disease causing acidity of the blood. Causes include
shock, renal failure, ethanol intoxication, aspirin ov erdose,
and diabetic ketoacidosis.
Metabolic alkalosis: pH high, HCO
3–
high. Causes include
heart failure, cirrhosis, chronic vomiting, hypokalemia, and
overdose of sodium bicarbonate.
Interfering factors Improper specimen handling invalidates results.
Fever causes decreased SaO
2
.
Leukocytosis causes a rapid decline in pH.
Cross-references None
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed June 2021.
Fauci AS, Braunwald E, Kasper DL, et al (eds): Harrison’s Principles of Internal Medicine, 17th Edition.
New York, McGraw-Hill, 2008
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
https://t.me/med1917
44 Laboratory Medicine in Psychiatry and Behavioral Science
Blood urea nitrogen (BUN)
Type of test Blood
Background and explanation
of test
Urea produced in the liver as a product of protein metabolism
circulates in the bloodstream and is eliminated by the kid
-
neys. When the kidneys are not functioning normally, urea
levels in the blood increase, and this increase can be mea
-
sured by the BUN test. This increase in BUN is called azote-
mia and, when severe enough to produce clinical symptoms,
uremia.
The ratio of BUN to creatinine level may be increased when
renal blood flow is compromised, as with dehydration or
congestive heart failure. Excessive protein intake and GI
bleeding are other causes of an increased ratio.
Relevance to psychiatry and
behavioral science
Elevation of the BUN level in renal failure is associated with
psychiatric signs and symptoms ranging from fatigue, lassi
-
tude, and somnolence to acute confusional states and delir-
ium. Seizures can occur. In chronic renal disease, the BUN
level correlates more closely with these uremic symptoms
than does the creatinine level.
Preparation of patient No fasting necessary. Dietary history may be needed to eval-
uate recent protein intake.
Indications • Component of metabolic panels (BMP and CMP)
• Evaluating renal function (with creatinine)
• Monitoring adequacy of dialysis and other interven-
tions for kidney disease
Reference range Adults ≤60 years: 6–20 mg/dL
Adults >60 years: 8–23 mg/dL
BUN-to-creatinine ratio normally between 10:1 and 20:1
Critical value(s) > 100 mg/dL indicates severe impairment of renal function
Increased levels •
Renal disease (acute or chronic)
• Renal injury
•
Decreased renal blood flow in the context of congestive
heart failure, dehydration, shock, stress, burns, or acute
MI
•
Rapid protein breakdown in the context of fever, burns,
or cancer
• Urinary tract obstruction
• Hemorrhage into the GI tract
• Diabetic ketoacidosis
• Excessive protein intake
• Anabolic steroid use
• Pregnancy
https://t.me/med1917
45 Laboratory Tests
Blood urea nitrogen (BUN) (continued)
Decreased levels • Hepatic failure
• Malnutrition, with low protein intake
• Celiac disease with impaired absorption
• SIAD
• Overhydration
• Pregnancy
Ratio of BUN to creatinine may also be decreased (<10:1) in
liver disease or malnutrition.
Interfering factors Low-protein, high-carbohydrate diets result in lower BUN
level. High-protein diets result in elevated levels.
BUN is decreased in late pregnancy.
Higher BUN levels are found in elderly adults and in males.
Many drugs cause increased or decreased BUN levels.
Cross-references Basic Metabolic Panel
Comprehensive Metabolic Panel
Creatinine
Syndrome of Inappropriate Antidiuresis
Uremic Syndrome
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed June 2021.
Fauci AS, Braunwald E, Kasper DL, et al (eds): Harrison’s Principles of Internal Medicine, 17th Edition.
New York, McGraw-Hill, 2008
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
https://t.me/med1917
46 Laboratory Medicine in Psychiatry and Behavioral Science
Bone mineral density scan
Type of test Imaging
Background and explanation
of test
This scan—also known as bone densitometry or a DEXA
scan—is an X ray of several body areas (e.g., spine, hip, fore
-
arm) to determine bone mineral density and thereby assist
in diagnosing osteoporosis and osteopenia. The latter is a
milder condition that may presage the development of oste
-
oporosis. Several types of scans are available, but the DEXA
scan is preferred because of its low radiation exposure and
precision of results. Test results are reported using a T-score
(density compared with that of healthy young adults) or a
Z-score (density compared with that of healthy age-peers).
Relevance to psychiatry and
behavioral science
Psychiatric disorders associated with reduced bone mineral
density include substance abuse, schizophrenia, dementia,
and depression. Psychotropic medications may also be im
-
plicated; for example, there is some evidence that SSRIs con-
fer an increased risk of osteoporosis and fracture. Smoking
is a well-known risk factor for reduced bone density. The
DEXA scan is a commonly used test in the preventive care
for adult and geriatric patients, particularly females. It is
probably underutilized by psychiatrists who provide pri-
mary care to patients, particularly in geriatrics.
Preparation of patient None needed
Indications • Evaluation of bone density in females ≥ 65 years, post-
menopausal females with risk factors such as smoking,
males ≥70 years, and younger males with risk factors
• Prediction of fracture risk
Reference range T-score <1.0 SD below normal
Critical value(s) None
Abnormal test T-score 1.0–2.5 SD below normal: osteopenia
T-score >2.5 SD below normal: osteoporosis
Interfering factors Nuclear medicine imaging within past 72 hours (longer for
gallium or indium) interferes with bone mineral density
scanning.
Any barium study with
in past 10 days interferes with spine
imaging.
Prosthetic devices or metal implants in areas being imaged
interfere with scanning.
Cross-references Osteoporosis
Anam AK, Insogna K: Update on osteoporosis screening and management.Med Clin North Am
105(6):1117–1134, 2021
ARUP Consult: Osteoporosis, in ARUP Consult: The Physician's Guide to Laboratory Test Selection and
Interpretation. Salt Lake City, UT, ARUP Laboratories, 2018. Available at: https://arupconsult.com/
content/osteoporosis. Accessed June 2021.
Lane NE: Epidemiology, etiology, and diagnosis of osteoporosis. Am J Obstet Gynecol 194:S3–S11, 2006
https://t.me/med1917
47 Laboratory Tests
Brain natriuretic peptide (BNP)
Type of test Blood
Background and explanation
of test
BNP and N-terminal pro B-type natriuretic peptide (NT-
proBNP) are hormones produced in the ventricles of the
heart (primarily the left ventricle) that increase in abun
-
dance when the ventricle stretches or suffers pressure over-
load. BNP measured in plasma is used to diagnose
congestive heart failure (CHF) and gauge its severity. When
BNP is ordered, the lab will perform either BNP or NT
-
proBNP testing, depending on instrument availability, al-
though the two tests are not interchangeable. These tests are
very accurate in distinguishing heart failure from other
causes of shortness of breath.
Relevance to psychiatry and
behavioral science
This test may be indicated in older patients reporting exces-
sive fatigue and inability to perform usual activities, symp-
toms that could be related to CHF but are sometimes
mistaken for depression. The presence of shortness of breath
is a critical feature.
Preparation of patient Patients should fast overnight before testing. If the sample
is nonfasting, this should be noted on the lab request form.
Indications • Evaluating symptoms of ventricular dysfunction:
fatigue, shortness of breath, cough, palpitations, and
hypertension
• Diagnosing CHF
• Determining the severity of CHF
• Monitoring the effects of therapy for heart failure
Reference range Normal result*
• BNP <125 pg/mL for patients <75 years
• BNP <450 pg/mL for patients ≥75 years
Levels will gr eatly exceed these reference values in most
patients with CHF. Levels of 100–500 pg/mL are said to be
inconclusive and require clinical correlation and further
testing.
BNP >500 pg/mL represents a positive test for CHF in
patients <75 years.
Threshold values for NT-proBNP depend on age and sex.
See reference range for your laboratory.
Critical value(s) >500 pg/mL
Increased levels • CHF
• Decrease in left ventricular ejection fraction
• Diastolic dysfunction
Decreased levels Patients taking medications used to treat heart failure,
including ACE inhibitors, β-blockers, and diuretics
https://t.me/med1917
48 Laboratory Medicine in Psychiatry and Behavioral Science
Brain natriuretic peptide (BNP) (continued)
Interfering factors Improper sampling invalidates BNP results; samples must
be collected in EDTA tubes. No special handling is needed
for NT-proBNP (serum or plasma).
Levels may be increased with age and kidney disease, and
levels are generally higher in females.
Cross-references Chest X-Ray
Echocardiogram
*BNP levels are significantly lower in obese individuals, so 50% lower cutoff values should be used to
determine abnormality.
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com
. Ac-
cessed June 2021.
Fauci AS, Braunwald E, Kasper DL, et al (eds): Harrison’s Principles of Internal Medicine, 17th Edition.
New York, McGraw-Hill, 2008
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Mueller C, McDonald K, de Boer RA, et al: Heart Failure Association of the European Society of Cardiol-
ogy practical guidance on the use of natriuretic peptide concentrations.Eur J Heart Fail 21(6):715–731,
2019
https://t.me/med1917
49 Laboratory Tests
Calcium
Type of test Blood
Background and explanation
of test
Calcium has essential roles in neurotransmission, cardiac
function, muscle contraction, blood clotting, and bone for
-
mation. The calcium level is maintained within a physio-
logical range through the actions of PTH and vitamin D.
Most calcium is stored in the bones and teeth; only 1% cir
-
culates in blood, half bound to albumin and half free (ion-
ized form).
When the albumin level drops, the total calcium level drops
as well, but the concentration of free calcium is unaffected.
For this reason, the total calcium value is corrected when
the albumin level is low, using the following formula:
[4 g/dL– plasma albumin]×0.8+total serum calcium
Alternatively, free calcium can be measured directly, but in
this case, the specimen requires special handling and expe
-
dited processing.
Relevance to psychiatry and
behavioral science
An abnormal calcium level may be found during routine
health screening and in the workup of various psychiatric
signs and symptoms. Abnormal calcium levels may be as
-
sociated with irritability, anxiety, depression, fatigue, leth-
argy, weakness, apathy, loss of appetite, delirium, nausea,
vomiting, constipation, polyuria, polydipsia, bone pain,
cardiac toxicity (including QTc prolongation and dysrhyth
-
mias), seizures, and coma. In patients with eating disor-
ders, low calcium levels may result from chronic laxative
abuse. Lithium increases the calcium level.
Preparation of patient Patients should avoid taking lithium, antacids, thiazide
diuretics, and vitamin D before testing. In drawing blood,
application of the tourniquet should be as brief as possible.
Indications •
Routine screening (BMP and CMP)
•
Evaluation of parathyroid function
•
Evaluation of renal function
•
Symptoms of hypocalcemia: skeletal muscle cramps, ab-
dominal cramps, paresthesias
• Symptoms of hypercalcemia: upset stomach, constipa-
tion, nausea, vomiting
• Workup for kidney stones
• Workup for Paget’s disease and other bone diseases
• Calcium monitoring after kidney transplant
• Calcium monitoring in certain cancers (breast, lung,
multiple myeloma, kidney, or head/neck)
• Monitoring treatment for abnormal calcium levels
https://t.me/med1917
50 Laboratory Medicine in Psychiatry and Behavioral Science
Calcium (continued)
Reference range Total serum calcium
• Adults <60 years: 8.6–10.0 mg/dL
• Adults 60–90 years: 8.8–10.2 mg/dL
• Adults >90 years: 8.2–9.6 mg/dL
Ionized serum calcium
• Adults: 4.64–5.28 mg/dL
Critical value(s) Total serum calcium
• <6 mg/dL: tetany, seizures
• >13 mg/dL: cardiac toxicity, dysrhythmias, coma
Ionized serum calcium
• <2 mg/dL: tetany, seizures
• >7 mg/dL: coma
Increased levels Total serum calcium >12 mg/dL
• Hyperparathyroidism
• Malignancy
• Granulomatous disease (tuberculosis, sarcoidosis)
• Prolonged immobilization with fracture (in children)
• Excessive vitamin D intake
• Paget’s disease (with elevated ALP)
Other diseases that can cause hypercalcemia but rarely se-
vere enough to be symptomatic include thyrotoxicosis,
milk-alkali syndrome, and adrenocortical insufficiency.
Increased ionized calcium
• Hyperparathyroidism
•Cancer
• PTH-producing tumors
• Excessive vitamin D intake
Decreased levels Total serum calcium <4.0 mg/dL
• Hypoalbuminemia (causing pseudohypocalcemia)
• Hypoparathyroidism
• Increased phosphorus level due to laxative abuse, renal
failure, or cytotoxic drugs
• Acute pancreatitis
•Renal failure
• Malabsorption due to GI disease
• Malnutrition, extreme dietary deficiency
• Severe osteomalacia
https://t.me/med1917
51 Laboratory Tests
Calcium (continued)
Decreased levels (continued) • Vitamin D deficiency, rickets
• Magnesium deficiency
• Alkalosis
• Alcoholism, cirrhosis
• Heritable resistance to PTH
Decreased ionized calcium levels
• Hyperventilation to treat increased intracranial pressure
(total calcium may be normal)
• Bicarbonate administration to treat metabolic acidosis
• Hypoparathyroidism
• Acute pancreatitis
• Vitamin D or magnesium deficiency
• Toxic shock syndrome
• Syndrome of multiple organ failure
Interfering factors Lithium and thiazide diuretics increase the calcium level.
Calcium-containing antacids or vitamin D taken just before
testing could transiently increase the calcium level.
Fluctuations in serum protein levels affect the interpretation
of total calcium levels but not ionized calcium levels.
Cross-references Anxiety Disorder Due to Another Medical Condition
Delirium
Depressive Disorder Due to Another Medical Condition
Hypercalcemia
Hypocalcemia
Psychotic Disorder Due
to Another Medical Condition
Seizures
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed June 2021.
Barstow C, Braun M: Electrolytes: calcium disorders. FP Essent 459:29–34, 2017
Carrick AI, Costner HB: Rapid fire: hypercalcemia.Emerg Med Clin North Am 36(3):549–555, 2018
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Pepe J, Colangelo L, Biamonte F, et al: Diagnosis and management of hypocalcemia. Endocrine 69(3):485–
495, 2020
Zagzag J, Hu MI, Fisher SB, Perrier ND: Hypercalcemia and cancer: differential diagnosis and treat-
ment.CA Cancer J Clin 68(5):377–386, 2018
https://t.me/med1917
Соседние файлы в папке Библиотека им академика М.И. Перельмана