Plasma Concentrations of Levobupivacaine With and Without Epinephrine in Transversus Abdominis Plane Blocks

The aim of this study is to determine the effect of the addition of vasoconstrictor in the plasma concentrations achieved and the extent of the transversus abdominis plane block in healthy male volunteers.

Use of TAP blocks, decreases use of opioids and reduces pain scores during the postoperative period after surgeries involving the anterior abdominal wall. However, the information regarding the sensitive range of the blockade and its duration is still limited. Since that the area of administration is an intermuscular plane, it is possible to infer a large area of absorption. Knowing plasma concentrations is essential to balance the usefulness of this technique with potential systemic toxicity associated with its use.

As an additional effect, clinically, the use of vasoconstrictors may prolong the duration of the blockade significantly, depending on the drug used and site of administration. To date, no studies evaluating the effect of the addition of vasoconstrictor both in the plasma concentrations achieved, and the quality, extent and duration of the TAP block.

• Drug: Levobupivacaine with epinephrine
  The subjects were randomized to receive a unilateral TAP block. This was realized using a sterile technique, guided by ultrasound. Two operators with experience in ultrasound-guided regional blocks performed all procedures. A high-resolution linear U.S. transducer (L38x/10-5 MHz Sonosite M-Turbo®, Bothell, WA) and a Stimuplex 100 mm needle, 20 gauge (B. Braun Stimuplex, Melgusen, Germany) were used. After obtaining a clear view of the blocking plane, between internal oblique and transverse muscles, 20 ml of levobupivacaine 0.25% with 5 µg/mL epinephrine were injected.
• Drug: Levobupivacaine without epinephrine
  The subjects were randomized to receive a unilateral TAP block. This was realized using a sterile technique, guided by ultrasound. Two operators with experience in ultrasound-guided regional blocks performed all procedures. A high-resolution linear U.S. transducer (L38x/10-5 MHz, Sonosite M-Turbo ®, Bothell, WA) and a Stimuplex 100 mm needle, 20 gauge (B. Braun Stimuplex, Melgusen, Germany) were used. After obtaining a clear view of the blocking plane, between internal oblique and transverse muscles, 20 ml of levobupivacaine 0.25% were injected.
• Other: Monitoring
  Standard anesthetic monitoring was used, including continuous electrocardiogram, non invasive blood pressure and peripheral oxygen saturation. Later, under local anesthesia a permeable venous line and an arterial line were installed for blood sampling measures to determine local anesthetic plasma levels.
• Other: Determining the extent of the block
  The extent of sensory block was measured by assessment of temperature, soft and hard touch using alcohol, cotton and pin prick respectively. These measurements were made ​​every 10 minutes during the first hour and every 30 minutes to complete 4 hours.

• Active Comparator: Levobupivacaine without epinephrine
  Interventions:

  • Drug: Levobupivacaine without epinephrine
  • Other: Monitoring
  • Other: Determining the extent of the block
• Experimental: Levobupivacaine with epinephrine
  Interventions:

  • Drug: Levobupivacaine with epinephrine
  • Other: Monitoring

Inclusion Criteria:

• Healthy male volunteers
• ASA I-II

Exclusion Criteria:

• BMI > 30kg m-2
• Patients with allergy to study drugs