A blood test can be an important part of preparing for anesthesia and surgery. Blood tests can provide detailed information about the patient’s state of health, aiding surgeons and anesthesiologists in identifying potential issues that could affect the patient’s procedure.

The complete blood count (CBC) is perhaps the most fundamental blood test, offering a comprehensive overview of the patient’s hematological status, and is ordered before anesthesia and surgery for many patients. The components of the CBC, including hemoglobin, hematocrit, white blood cells (WBCs), and platelets, all provide invaluable information (1). For example, low hemoglobin and hematocrit levels can reveal anemia, which might necessitate a delay in surgery until the condition is appropriately managed. On the other hand, elevated WBCs (leukocytosis) might indicate an active infection, prompting further investigation and possible postponement of the procedure to prevent postoperative complications.

Blood chemistry tests, including the basic metabolic panel (BMP) and liver function tests (LFTs), assess the patient’s metabolic state and organ function. These tests can uncover issues such as electrolyte imbalances or renal insufficiency, which could affect the patient’s response to anesthesia and their ability to recover postoperatively. Because the liver plays a critical role in metabolizing medications used during surgery, it is important to perform a liver function test, as the liver’s impaired function can lead to unexpected drug interactions and complications (2).

Coagulation profiles, including prothrombin time (PT) and partial thromboplastin time (PTT), are vital for assessing the blood’s clotting ability. They are particularly relevant for patients with a history of bleeding disorders or those on anticoagulant therapy, as they are at an increased risk of perioperative bleeding. This information allows the surgical team to plan for potential blood product transfusions or to adjust anticoagulant medications as needed (3). Furthermore, the type and screen test is conducted to determine a patient’s blood type and screen for any antibodies that might react with donor blood. This is essential for surgeries with a significant risk of blood loss, as it ensures that compatible blood products are readily available if a transfusion becomes necessary (2).

After a blood test is performed before anesthesia, it is important for the perioperative team to adjust its strategy for surgery using the information gained. Blood tests must be interpreted within the broader context of the patient’s overall medical history and the specific demands of the planned procedure. False positives or incidental findings can lead to unnecessary delays or additional testing. Guidelines from medical societies, such as the American Society of Anesthesiologists, advocate for a patient-centered approach, recommending that preoperative tests be ordered based on the patient’s health status, clinical history, and the type of surgery being performed (1). A tailored approach helps to avoid unnecessary testing and reduce healthcare costs.

For many patients, a blood test before anesthesia and surgery is an important preoperative step, providing critical insights into their health status and identifying potential risks that could impact the surgery or postoperative recovery. A thoughtful, patient-specific approach to these tests, guided by clinical guidelines and interdisciplinary collaboration, is paramount to ensuring patient safety and optimizing surgical outcomes.

References

1. American Society of Anesthesiologists. Practice Advisory for Preanesthesia Evaluation: An Updated Report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Anesthesiology. 2012;116(3):522-538.
2. Kumar A, Srivastava U. Role of routine laboratory investigations in preoperative evaluation. Journal of Anaesthesiology Clinical Pharmacology. 2011;27(2):174-179.
3. Dzik WH, Blajchman MA, Fergusson D, Hameed M, Henry B, Kirkpatrick AW, et al. Clinical review: Canadian National Advisory Committee on Blood and Blood Products – Massive transfusion consensus conference 2011: report of the panel. Critical Care. 2011;15(6):242.