Colonoscopy Preparation and Blood Pressure
Colonoscopy preparation itself does not directly increase blood pressure; however, hypertension is commonly observed during the endoscopic procedure, often aggravated by patients not taking their antihypertensive medications on the day of the procedure. 1
Blood Pressure Changes During Colonoscopy
Hypotension is More Common Than Hypertension
Colonoscopy typically causes decreased blood pressure and heart rate, not elevation. 2 A prospective randomized study of 618 patients found that colonoscopy resulted in decreased BP and HR, with hypotension occurring in 6% of monitored patients. 2
The bowel preparation process itself can lead to volume depletion from catharsis and inadequate oral hydration, which manifests as baseline tachycardia and hypotension when patients arrive for the procedure. 1
Lower pre-procedure systolic BP (OR=0.97,95% CI=0.95-0.99; p=0.004) and diastolic BP (OR=0.95% CI=0.92-0.97; p<0.001) are the main risk factors for procedural hypotension during colonoscopy. 3
When Hypertension Does Occur
Hypertension during endoscopic procedures is commonly seen and is often aggravated by patients not taking their antihypertensive medications on the day of the procedure. 1
Tachycardia and hypertension during colonoscopy may indicate inadequate sedation, particularly when the procedure is started before the patient is adequately sedated. 1
In one prospective study, hypertension occurred in 30% of monitored patients during routine endoscopy, though these hemodynamic aberrations were clinically insignificant and did not affect outcomes. 2
Mechanism of Blood Pressure Changes
Volume Depletion from Bowel Preparation
The most common complications of bowel preparation in lower GI bleeding patients are hypotension and vomiting, though no patients experienced aspiration pneumonia or volume overload in retrospective reviews. 1
Baseline tachycardia and hypotension in patients presenting for colonoscopy likely represent volume depletion resulting from catharsis and/or inadequate oral hydration during the preparation phase. 1
Sedation Effects
Sedation medications are more likely to cause hypotension than hypertension. Premedication with midazolam increased the risk for hypotension (19% vs 3% in placebo group, p<0.01) and caused significantly lower systolic and diastolic blood pressure during colonoscopy. 4
Mean blood pressure fell significantly in premedicated patients (97.6 ± 2.6 vs. 89.5 ± 2.7 mmHg before and after colonoscopy, respectively; p<0.05). 5
Vagal Response
- Individual patients have susceptibility to vagally mediated bradycardia and hypotension that can be precipitated by stretching the sigmoid mesentery during passage of a colonoscope. 1
Clinical Significance
Although hypotension and hypertension during endoscopy very rarely result in permanent complications, they occasionally reach levels for which corrective action is appropriate. 1
Cardiovascular complications are less commonly life-threatening during endoscopy, and when life-threatening, they most often follow a period of inadequate ventilation and hypoxemia rather than direct BP effects. 1
Hemodynamic aberrations occurred in 71% of monitored patients during routine endoscopy, but no monitored or control patient had an adverse result, indicating these changes are clinically insignificant. 2
Management Recommendations
Antihypertensive Medications
Patients should continue their antihypertensive therapy leading up to endoscopy. 3 Taking a BP medication, regardless of class, was not associated with an increased risk of procedural hypotension (all p>0.05). 3
The American Gastroenterological Association recommends that management of antihypertensive agents should be individualized with the assistance of the prescribing clinician based on the timing of the colonoscopy. 1
Common Pitfalls to Avoid
Do not instruct patients to hold all antihypertensive medications on the day of the procedure, as this contributes to intraprocedural hypertension without reducing hypotension risk. 1, 3
Recognize that lower pre-procedure BP is the main risk factor for procedural hypotension, not the use of antihypertensive medications. 3
Be aware that volume depletion from bowel preparation is a more significant contributor to hemodynamic instability than the preparation itself causing hypertension. 1