Is General Anesthesia Safe for People With High Blood Pressure?
The answer to this question “Is general anesthesia safe for people with high blood pressure”, is, usually.
For elective surgery, blood pressure control should be optimized through lifestyle changes and medication if necessary. For emergency surgery, anesthesiologists will use their medications to control the blood pressure during anesthesia.
Like most issues in anesthesia, and medicine in general, there are many variables that determine the risk in different situations.
Among the determining factors are:
- The level of blood pressure elevation
- the type of surgery to be done
- the medication regimen used by the patient
- coexisting diseases
- other factors
Classifications of Blood Pressure
SYSTOLIC BLOOD PRESSURE
DIASTOLIC BLOOD PRESSURE
Normal Blood Pressure (Healthy)
Prehypertension - Stage 1
Prehypertension - Stage 2
Severe Hypertension (Stage 2 Hypertension)
Hypertension and Pre-Hypertension Defined
As the blood flows through your arteries, it exerts pressure on the walls of those arteries. Various medical devices can measure that pressure. The systolic (top) number is the highest pressure detectable during a cardiac pumping cycle. The diastolic (bottom) number is the number representing the pressure of the blood against the arteries when the heart rests between heartbeats.
Not long ago, hypertension was defined as anything higher than 140/90. As more data is collected about healthy blood pressure, new definitions have emerged.
Any systolic blood pressure between 120 and 139 is called prehypertension. Diastolic readings in the range of 80-89 also are ‘prehypertensive.’
More clinically significant might be the term "stage 2 prehypertension". This definition is reserved for blood pressures in the 130-139 systolic range and diastolic pressure between 85 and 89. Studies, as cited and summarized in an excellent review in the Nov 2010 issue of Cardiology Clinics* show that the risk of cardiac events (heart attack, stroke, etc) goes up 50 to 130 percent for people with blood pressure in this range!
*Brent M. Egan, MDa,, Daniel T. Lackland, DrPHa, Daniel W. Jones, MDb; “Prehypertension: An Opportunity for a New Public Health Paradigm”; Cardiol Clin 28 (2010): 561–569
Blood Pressure and Anesthesia
Although it may not be ideal, general anesthesia is usually going to be safe for people with high blood pressure (unless it is very high). During anesthesia, we are usually able to control the blood pressure with our medications. The risk after surgery, however, still exists.
Surgery and anesthesia cause stress on the body. During surgery, it is not unusual to have swings in blood pressure from very low to a bit too high. Anesthesia blunts these changes to some degree, but there are still ups and downs in blood pressure. We can treat these changes with medications.
Blood pressure is likely to be lowest right after the induction of anesthesia (when you go to sleep) It may stay low during the anesthetic, as well. This is related to the fact that anesthetics cause blood vessels to dilate--relax. It will be highest during anesthesia emergence (waking up).
In general, the less well-controlled your blood pressure, the more likely it is to cause problems during and after surgery and anesthesia. Even though anesthesiologists can control blood pressure to some degree under anesthesia, there can still be uncontrollable or unpredictable reactions when preop blood pressure is too high.
High Blood Pressure and Surgery Risks
In general, these risks are increased as blood pressure increases:
- Bleeding: As logic would tell you, if there is more pressure against the blood vessels, bleeding during – and potentially after-- surgery will be more brisk.
- Unstable Blood Pressure and Heart Rate: If your hypertension isn’t controlled and stable preoperatively, the risk of dangerous drops and spikes while under anesthesia increases.
- Heart Attack: Cardiovascular risk goes up with increases in blood pressure. If you have prehypertension, you are 3.5 times more likely to have a heart attack than if you had lower blood pressure. This risk would also be true for postoperative heart attack.
- Stroke: High blood pressure is always a risk factor for stroke, especially in those already at risk. If hypertension is not well controlled before surgery, this risk can be significant.
Most of the time, risk will increase proportionally with blood pressure. Most anesthesiologists will cancel your surgery if your blood pressure is in the range of 200/100. Often, and especially for some types of surgery (vascular surgery, for example), even lower values will result in cancellation or delay of surgery.