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The efficacy of simulated intravascular test dose in sedated patients
1Department of Anesthesia, Akita University School of Medicine, Akita-City, Japan. mtanaka@med.akita-u.ac.jp
Insights
Systolic blood pressure increase and T-wave amplitude decrease are more reliable indicators than heart rate changes for detecting accidental intravascular test doses in sedated patients. This finding is crucial for patient safety during epidural procedures.
Area of Science:
- Anesthesiology
- Cardiology
- Pharmacology
Background:
- Sedation can impair subjective detection of intravascular test doses.
- Objective hemodynamic and T-wave criteria for detecting intravascular test doses require further evaluation.
- Accidental intravascular injection during epidural procedures necessitates reliable detection methods.
Purpose of the Study:
- To compare the efficacy of heart rate (HR), systolic blood pressure (SBP), and T-wave amplitude changes in detecting accidental intravascular injection of an epinephrine-containing test dose.
- To evaluate these criteria in healthy patients receiving different sedation regimens (midazolam, midazolam plus fentanyl, or no sedative).
Main Methods:
- Sixty healthy patients were randomized into three groups: midazolam, midazolam plus fentanyl, or no sedative.
- An intravenous test dose of saline followed by lidocaine with epinephrine (15 microg) was administered.
- Continuous monitoring of HR, SBP via arterial catheter, and ECG (lead II) was performed for 4 minutes post-injection.
Main Results:
- All subjects showed significant HR and SBP increases and T-wave amplitude decreases after the test dose.
- The HR increase was significantly less in the midazolam plus fentanyl group compared to other groups.
- SBP increase and T-wave amplitude decrease criteria demonstrated 100% sensitivity and specificity irrespective of sedation, unlike HR criteria.
Conclusions:
- Increased SBP and decreased T-wave amplitude are more reliable indicators than HR changes for detecting inadvertent intravascular injection of an epinephrine test dose.
- These findings are particularly relevant for patients sedated with midazolam and fentanyl.
- Objective measures like SBP and T-wave changes enhance safety in procedures using epidural test doses.
Unlabelled:
Sedation usually decreases the reliability of subjectively detecting an intravascular test dose, but the efficacies of objective hemodynamic and T-wave criteria remain undetermined. Sixty healthy patients were randomly assigned to receive IV midazolam in 1-mg increments until they were lightly sedated, fentanyl 2 microg/kg followed by incremental midazolam until they were similarly sedated, or no sedative (n = 20 each). Then, normal saline 3 mL was administered IV, followed 4 min later by 1.5% lidocaine 3 mL plus epinephrine 15 microg (1:200,000) in all subjects. Heart rate (HR), systolic blood pressure (SBP) measured by a radial arterial catheter, and lead II of the electrocardiogram were continuously recorded for 4 min after the saline and test dose injections. An IV test dose produced significant increases in HR and SBP and decreases in T-wave amplitude in all subjects. However, the mean maximum increase in HR in patients sedated with midazolam plus fentanyl (31 +/- 14 bpm [mean +/- SD]) was significantly less than in those administered midazolam alone or no sedative (42 +/- 12 and 44 +/- 10 bpm, respectively; P < 0.05). A sensitivity of 100% was obtained on the basis of the traditional HR criterion (positive if > or =20 bpm increase) in patients sedated with midazolam or no sedative, but it was 70% in those with midazolam plus fentanyl (P < 0.05 versus the other two groups). Irrespective of the treatment, sensitivities and specificities of 100% were obtained according to the SBP (positive if > or =15 mm Hg increase) and T-wave (positive if > or =25% decrease in amplitude) criteria. An increase in SBP and a decrease in T-wave amplitude are more reliable than an HR response for detecting accidental intravascular injection of the epinephrine-containing test dose in subjects sedated with midazolam and fentanyl.
Implications:
To determine whether an epidural catheter is in a blood vessel, an epidural test dose containing 15 microg epinephrine is used. We found that an increase in systolic blood pressure and a decrease in T-wave amplitude seem to be more reliable than a heart rate change for detecting inadvertent intravascular injection of an epinephrine-containing test dose in patients sedated with midazolam and fentanyl.
