Fentanyl Pretreatment Does Not Impair the Reliability of an Epinephrine-Containing Test Dose During Propofol-Nitrous Oxide Anesthesia

Perfusion index versus non-invasive hemodynamic parameters during insertion of i-gel, classic laryngeal mask airway and endotracheal tube

Background:

Perfusion index (PI) is a non-invasive numerical value of peripheral perfusion obtained from a pulse oximeter. In this study, we evaluated the efficacy of PI for detecting haemodynamic stress responses to insertion of i-gel, laryngeal mask airway (LMA) and endotracheal tube and compare, its reliability with the conventional haemodynamic criteria in adults during general anaesthesia.

Methods:

Sixty patients scheduled for elective general surgery under general anaesthesia were randomised to three groups. (i-gel, LMA and ET groups (n=20/group). Heart rate (HR) (positive if ≥10 bpm), systolic blood pressure (SBP), diastolic blood pressure (DBP) (positive if ≥15 mm Hg) and PI (positive if ≤10%) were monitored for 5 min after insertion. Main outcome measures: SBP, DBP, HR and PI were measured before induction of anaesthesia and before and after insertion of the airway device.

Results:

Insertion of airway devices produced significant increases in HR, SBP and DBP in LMA and ET groups. Moreover, PI was decreased significantly by 40%, 100% and 100% in the three groups. Using the PI criterion, the sensitivity was 100% (CI 82.4-100.0%). Regarding the SBP and DBP criterions, the sensitivity was 44.4% (CI 24.6-66.3%), 55.6% (CI 33.7-75.4%) respectively. Also, significant change in the mean PI over time (from pre-insertion value to the 1^st min, 3^rd min, until the 4^th min after insertion without regard the device type), (P<0.001).

Conclusion:

PI is a reliable and easier alternative to conventional haemodynamic criteria for detection of stress response to insertion of i-gel, LMA and ET during propofol fentanyl isoflurane anaesthesia in adult patients.

The efficacy of hemodynamic and T-wave criteria for detecting intravascular injection of epinephrine test dose in propofol-anesthetized adults

A recent study demonstrated 100% effectiveness of hemodynamic criteria during propofol anesthesia, when a full dose of an epinephrine (15 microg)-containing test dose was injected intravascularly. We designed this dose-response study to determine minimal effective epinephrine doses and efficacies of hemodynamic and T-wave criteria for detecting intravascular injection of the epinephrine test dose in propofol-anesthetized adults. Eighty healthy adult patients were randomly assigned to one of four groups according to a simulated IV test dose using propofol (133 microg center dot kg(-1) center dot min(-1)) and nitrous oxide (FIO(2) = 0.33) anesthesia after endotracheal intubation (n = 20 each). The Saline group received 3 mL of normal saline IV; the Epinephrine-15 group received 3 mL of 1.5% lidocaine containing 15 microg epinephrine; and the Epinephrine-10 and -5 groups received 2 and 1 mL of the test dose of the identical components, respectively. Heart rate (HR), systolic blood pressure (SBP), and lead II of the electrocardiogram were recorded continuously for 5 min after the IV injection of the study drug via a peripheral vein. Sensitivities and specificities of 100% were obtained based on the modified HR (positive if greater-than-or-equal to 10 bpm increase) and the T-wave (positive if greater-than-or-equal 25% in amplitude) criteria if greater-than-or-equal 5 microg of epinephrine was injected IV. Based on the SBP criterion (positive if greater-than-or-equal 15 mm Hg increase), however, 100% sensitivity and specificity were associated only with greater-than-or-equal 10 microg of epinephrine doses. These results suggest that the minimal effective epinephrine doses for detecting unintentional intravascular injection are 5 microg based on the HR and T-wave criteria, and 10 microg based on the SBP criterion in adult patients anesthetized with propofol and nitrous oxide.

IMPLICATIONS

Accidental migration of an epidural catheter into a blood vessel is often detected by hemodynamic changes after injecting an epidural test dose containing epinephrine. Our results suggest that 5 microg of epinephrine is not adequate to reliably produce hemodynamic and T-wave alterations in adult patients during propofol anesthesia.

The efficacy of simulated intravascular test dose in sedated patients

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.