50th Annual Regional Anesthesiology and Acute Pain Medicine Meeting

Only a Matter of Timolol: A Case Report of a False Negative Epidural Test Dose

Alexander Linse MD, Keleigh McLaughlin MD, Aidan Hoie MD

University of Colorado

Background

Epidural placement requires confirmation of correct catheter positioning.
A common safety check involves administering lidocaine with epinephrine to detect intravascular or intrathecal placement.
Expected response to intravascular injection :
Heart rate increase: ≥20 bpm
Systolic blood pressure increase: ≥15 mmHg
Various factors can alter expected responses.
This case highlights a false negative test dose in a patient using timolol eye drops for glaucoma.

Methods

Patient consent obtained for case reporting.
Comprehensive review of anesthetic and medical records.
Literature review conducted to explore systemic effects of ophthalmic beta blockers.
Institutional Review Board (IRB) review not required per Colorado Multiple Institutional Review Boardguidelines and no identifiable patient data is presented.

Case Presentation

Patient: 71-year-old female with hypertension, glaucoma, and duodenal adenocarcinomascheduled for a Whipple procedure.
Epidural Placement:
Thoracic epidural placed without complications.
Test dose: 3 mL 1.5% lidocaine with epinephrine (1:200,000) administered.
No significant change in heart rate or blood pressure.
Findings:
Blood aspirated from the catheter in the operating room before infusion.
Retesting showed transient blood pressure increase on arterial line within next 30 seconds
No heart rate change.
Review of patient’s medications revealed timolol eye drops use.
Intervention:
Epidural removed and replaced postoperatively without complications.
Postoperative pain control was uneventful, catheter removed on POD 5.

Discussion

Ophthalmic beta blockers, such as timolol, are often prescribed to patients with glaucoma.
They can cause systemic effects due to absorption through multiple routes:
Conjunctival epithelium
Lacrimal channels
Nasal mucosa
GI tract
These medications may lead to blunted heart rate responses while maintaining blood pressure via compensatory vasoconstriction.
Clinical implications:
A 2012 study showed patients on systemic beta blockers often fail to reach the 20 bpm increaseexpected after intravascular epinephrine administration.
Epidural placement safety checks may be less reliable in these patients.
Institutional Practice Considerations:
Blood pressure cycling every 5 minutes may miss transient responses.
Morefrequent blood pressure monitoring could improve detection of false negative test doses in patients on beta blockers.
Reinforces the importance of multiple safety measures in epidural placement.

ONLY A MATTER OF TIMOLOL: A CASE REPORT OF A FALSE NEGATIVE EPIDURAL TEST DOSE