Most of us are used to taking our medications as part of the routine: A small pill in the morning for blood pressure, treatment for diabetes, maybe a pain reliever or a dietary supplement. But once surgery is involved, even one that seems “simple,” the picture can change.
While the doctors prepare for surgery, our body is dealing with unusual conditions that do not happen on a daily basis: Prolonged fasting, general anesthesia, possible bleeding, and changes in blood pressure and sugar levels. In such cases, medications that normally balance and maintain health can suddenly act too strongly, too weakly, or in a way that endangers the patient.
So what actually changes in the body during surgery?
What happens in the body?
Before surgery – fasting and changes in body balance
Preparation for surgery usually includes fasting for many hours. During this time, blood sugar levels drop, fluid balance changes, and sometimes there is also a decrease in blood electrolytes. Such a condition may cause medications normally taken to behave differently—some stronger than usual, others weaker. In addition, the stress and mental pressure surrounding the surgery also affect body systems, such as the heart and blood pressure.
During surgery – anesthesia, bleeding, and blood pressure fluctuations
During surgery, the body goes through conditions that do not exist in daily life: Cutting, blood loss, and anesthetic drugs that affect the activity of the brain, heart, and respiratory system. This combination changes the way medications work. Drugs that stabilize blood pressure or heart rate in daily life, for example, may affect differently when combined with anesthetics. The clotting system also functions differently, which makes the body more sensitive to the effects of medications or supplements related to blood.
After surgery – recovery and healing
After surgery is completed, the body focuses on healing the wound and recovering from anesthesia. The kidneys and liver—which break down and eliminate medications—may be under extra strain. In addition, many patients receive strong painkillers or other medications after surgery, creating new interactions with their regular medications. The immune system and blood are also busy in the healing process, which can change the way some medications work.
What do medications do in the body?
Blood-thinning drugs – helpful daily, risky during surgery
Blood thinners save lives and prevent strokes or heart attacks. But during surgery they may cause significant bleeding. Therefore, in many cases the medical team will consider adjusting or rescheduling the treatment, to balance between the risk of bleeding and protection of the heart and blood vessels.
Diabetes medications – fasting, insulin, and blood sugar levels
Diabetic patients know how important it is to maintain balance. But right before surgery, when fasting is required, sugar-lowering medications may work “too strongly” and cause hypoglycemia (especially low blood sugar). Therefore, it is important to inform the team so they can adjust treatment and prevent complications.
Blood pressure treatments – under anesthesia, everything changes
There are blood pressure medications that work great in daily life, but under general anesthesia they may cause blood pressure to drop too sharply. Therefore, doctors must know exactly which medications are taken and when, to decide whether to adjust the dosage or continue as usual.
Even “innocent” and routine over-the-counter medications can have an effect
It is important to know that not only “major medications” require attention. Painkillers and anti-inflammatories (NSAIDs), certain dietary supplements (such as Vitamin E or ginseng), and even simple painkillers can affect blood clotting or kidney function, and therefore are significant before surgery.
Who is at special risk?
Elderly patients, who often take several medications at once; diabetic patients, for whom fasting or the surgery itself may disrupt blood sugar levels; heart patients, whose cardiovascular system is especially sensitive; and oncology patients, who are treated with biological or chemotherapy drugs. All of these require careful medication coordination to undergo surgery safely.
To deal with all these challenges, hospitals conduct a process of personalized medication adjustment. This means a thorough review of all the medications and supplements the patient takes at home, checking them against the patient’s medical condition and test results, and optimizing treatment accordingly. Clinical pharmacists also take part, working alongside doctors to ensure that treatment is safe and effective. They place special emphasis on sensitive populations—elderly patients, heart patients, diabetic patients, and oncology patients—to reduce complications and improve the recovery process.
So what should be done?
The message is simple: Do not decide on your own. Do not stop or change treatment on your own. Do share with the family doctor, anesthesiologist, and surgeon about every medication and supplement—so the team can adapt recommendations personally.
This way, instead of risking unnecessary complications, it is possible to ensure the surgery is safer and recovery is faster and smoother.
The content in this article does not constitute medical advice or treatment instructions. For any medical question, consult your treating physician.
Dr. Kfir Bildman is Head of the Clinical Pharmacy Division, Assuta Medical Centers.