Careful patient evaluation before performing an elective, i.e., scheduled surgery, is essential to ensure the patient is adequately prepared for surgery, thereby reducing the morbidity associated with surgical procedures. In this context, the laboratory provides valuable information.

In recent years, we have witnessed an overuse of preoperative diagnostic investigations, resulting in increased health-care costs without significant benefits in terms of patient outcomes.

Although in many health-care settings, the choice of preoperative examinations is dictated by preestablished protocols, it would be more appropriate to modulate the choice of tests according to a careful assessment of surgical risk based on history, clinical data, and objective examination, as indicated by the American Society of Anesthesiologists (ASA) and the European Society of Anesthesiology. Recently, a Cochrane randomized controlled trial and meta-analysis has demonstrated the futility of predefined panels of preoperative examinations before cataract surgery. Thus, it is recommended that “routine investigations” should be replaced with targeted diagnostic tests tailored on the patient.

Furthermore, it should be noted that the objective of pre operative testing is not to define the risk of potential complications associated with surgical procedures.

Preoperative evaluation for elective procedures is usually performed 30 days to 12 weeks before surgery on an outpatient basis. It is always necessary when the surgical procedure requires anesthesia; it should not be performed for apparently healthy patients who undertake local anesthesia or sedation (dental, dermatological, and endoscopic procedures).

The National Institute for Health and Care Excellence (NICE) guidelines published in June 2003 have recently been updated. Once again, the tests to be performed must be evaluated according to the patient’s disease status and the degree of complexity of the surgical procedure. However, the recommendation to abandon the approach for routine investigations of the whole preoperative population is confirmed.

A preoperative evaluation can also use instrumental investigations, such as chest X-ray, electrocardiogram, and spirometry, and laboratory tests.

The main laboratory tests before elective surgery are:

• Complete blood count (CBC)

• Kidney function tests

 • Glycemia

 • HbA1c

 • Urine test

• Pregnancy test

• Immunohematological tests

In selected cases, blood gas analysis may also be included to complement the respiratory function assessment.

CBC should not be routinely requested but only when there is a high pretest probability of anemia, such as in chronic inflammatory diseases, chronic renal failure, or chronic liver disease, in the presence of clinical signs and symptoms of anemia. Thalassemia trait   is particularly important in surgical procedures. The decision to perform further tests, such as hemoglobin electrophoresis, should be evaluated according to the clinical and family history. The platelet count must be monitored in relation to the coagulation.

The assessment of coagulation status includes prothrombin time (PT), activated thromboplastin time (aPTT), and fibrinogen. It is evaluated to identify possible disorders of hemostasis. In particular, these tests help identify acquired conditions associated with bleeding risk during surgical procedures. Similarly to CBC, there is consensus that these tests should be performed in patients with bleeding risk factors, i.e., chronic liver disease or oral anticoagulants.

Renal function tests include serum creatinine and electrolytes (Na+, K+, Cl−, Ca2+). These investigations should be performed in patients with a clinical and medical history indicative of renal impairment, such as, chronic renal failure, hypertension, heart failure, decompensated diabetes, and chronic liver disease. Moreover, they should be performed in case of treatment with diuretics, angiotensin-converting enzyme inhibitors, non-steroidal anti-inflammatory drugs, and digoxin. Age must be considered when evaluating renal function. However, in the absence of any of the above conditions, advanced age alone does not support the performance of these tests.

Glycometabolic decompensation should be investigated by measuring blood glucose and HbA1c in diabetic patients because perioperative glycemic control significantly influences the patient outcome. The prevalence of misrecognized diabetes in the preoperative population is low (0.5%), so routine performance of these tests is not recommended.

The main indication for urine testing in the preoperative patient is identifying a urinary tract infection, which may be followed by further investigations such as urine culture and antibiogram. These examinations should be requested if an infection may affect surgical or anesthesiological procedures.

The usefulness of pregnancy testing (serum β-hCG) in women of childbearing age before surgery has long been debated. The need to ascertain the presence of pregnancy is based on the perioperative risks for the fetus and the mother. In 5.8% of cases, surgical and anesthesiological procedures in pregnant women lead to spontaneous pregnancy termination; the percentage rises to 10.5% if referred to the first trimester of pregnancy. Pregnancy tests should be carried out when a pregnancy cannot be excluded based on anamnesis. This test should always be performed after the risks associated with the procedure have been adequately explained to the woman if she is pregnant and she has given her consent.

In patients undergoing thoracic surgery, pneumonectomy, esophagectomy, or head and neck surgery, it is recommended to perform blood gas analysis.

Immunohematological tests (blood group determination and transfusion compatibility) are prescribed in order not to delay a transfusion that may be necessary during surgery.

Infectious screening (HBV, HCV, HIV) should not be per formed. Their relevance in this context is aimed exclusively at the safety of health-care workers because it is related to occupational exposure to potentially infected biological fluids.

Therefore, the choice of preoperative investigations must be evaluated according to the patient’s health status and the degree of complexity of the surgical procedure.

According to the American Society of Anesthesiologists (ASA)’s classification, there are six classes of global operative risk:

• ASA 1: Normal healthy patient

 • ASA 2: Patient with mild systemic disease

• ASA 3: Patient with a severe systemic disease that is not life-threatening

• ASA 4: Patient with a severe systemic disease that is a constant threat to life.

• ASA 5: Moribund subjects with life expectancy

While the usefulness of preoperative screening is well- established for patients in categories 3–6, its use in healthy or asymptomatic patients in categories 1 and 2 is controversial.

The complexity of surgery is classified into three degrees:

 • Grade 1: Minor surgery (e.g., excision of skin lesion, drainage of breast abscess)

• Grade 2: Intermediate surgery (e.g., reduction of inguinal hernia, saphenectomy, arthroscopy, tonsillectomy)

• Grade 3: Major or complex surgery (e.g., radical hysterectomy, endoscopic prostatectomy, total thyroidectomy, colon resection, lung surgery, cardiovascular surgery)

According to the most recent guidelines by NICE, preoperative laboratory assessment should be carried out according to the recommendations summarized in Table 1.

Table1. Preoperative laboratory tests according to the complexity of the surgery and the ASA class according to the NICE 2016 guidelines

اخر الاخبار

اخبار العتبة العباسية المقدسة

الهيأة العليا لإحياء التراث تصدر رسالة في أصول الفقه للمحقق السيد محمد الخسروشاهي

العتبة العباسية المقدسة تطلق محاضرات محفل نهج البلاغة الأسبوعي في بغداد

المجمع العلمي يجري الاختبارات النظرية للدورات القرآنية في النجف الأشرف

قسم التطوير يجري اختبارات الدفعة التاسعة لمنتسبي العتبة العباسية المقدسة المتقدمين لأكاديمية التطوير الإداري

المزيد

الآخبار الصحية

العين تحت المراقبة.. عدسات لاصقة تكشف خطرا قبل فوات الأوان

قائمة طعام تُرهق ضغط الدم.. تجنبها سريعاً

دراسة: تنويع الأنشطة الرياضية يطيل العمر

كشف علمي "مذهل": ماذا يحدث للمخ في حالة عدم النوم ليلا؟

المزيد

الآخبار التكنلوجية

اكتشاف الخلايا المسؤولة عن فقدان ذاكرة الطفولة

صور فضائية ترصد "ظاهرة" سببها السيارات الكهربائية

إقالة مدرب إسباني بسبب "Chat GPT".. ماذا حدث؟

بسبب إدمان الشباب.. منصات تواصل عالمية أمام القضاء الأميركي

المزيد

مواضيع ذات صلة

The Role of Laboratory in Urgency: Altered State of Consciousness

sputum culture and sensitivity (C&S, Culture and Gram stain)

sodium (Na), blood

small intestinal bacterial overgrowth test (SIBO test, Lactulose Breath Test)

Clinical Biochemistry of Exercise: The Benefits of Movement

Medium- to Long-term Effects of Physical Activity on Laboratory Parameters

Acute Effects of Sports Performance on Laboratory Parameters

ProstaScint scan (Radioimmunoscintigraphy of the prostate [RIS])

pregnanediol

prealbumin (PAB, Thyroxine-binding prealbumin [TBPA], Thyretin, Transthyretin)

Biomarkers of Sepsis

Role of the Laboratory in Sepsis