Top-up for Cesarean section. Dr. Moira Baeriswyl, Prof. Christian Kern

Transcription

1 Top-up for Cesarean section Dr. Moira Baeriswyl, Prof. Christian Kern

2 In which situations? 2

3 What exactly is a Top-up? 3

4 C-section, NOW!! Emergency C-section requires a rapid onset of sustained analgesia 4

5 What should we know? Why CS? Degree of emergency? What is the neonatal status? Which local anesthestic to choose? What is the current practice? 2 nd 1 st 5

6 What is common practice? K.Regan and G. O Sullivan. Anaesthesia 2008, 63;

7 Which local anaesthetics? K.Regan and G. O Sullivan. Anaesthesia 2008, 63;

8 Which monitoring during maternal transfer (from DR to OR)? K.Regan and G. O Sullivan. Anaesthesia 2008, 63;

9 Adverse incidents? K.Regan and G. O Sullivan. Anaesthesia 2008, 63;

10 Which local anaesthetics? Prospective, single blind study ;plain 0.5% bupivacaine compared with lidocaine/ adrenaline/fentanyl for extending previous low-dose epidural analgesia in 68 patients for emergency CS. from the beginning of the test dose until the patient had a block of T7 to touch. from the start of drug preparation until the patient had a block of T7 to touch J. Goring-Morris, I. F. Russell. IJOA 2006; 15;

11 Low-dose epidural top up for emergency caesarean delivery: a randomised comparison of levobupivacaine versus lidocaine/epinephrine/fentanyl Survival curves for onset time of loss of touch sensation at T7 following epidural top up with 0.5% levobupivacaine or 2% lidocaine / epinephrine 100 µg/ fentanyl 100 µg mixture (LEF: dotted line) and levobupivacaine (Levo : continuous line). P. Balaji, P. Dhillon, I.F. Russell. IJOA 2009; 18;

12 Similar onset time of 2-chloroprocaine and lidocaine + epinephrine for epidural anesthesia for elective Cesarean section E.Bjornestad et al. Acta Anaesthesiol Scand 2006; 50;

13 BJA 2011 ; 107:

14 EpiduralTop-Up for Emergency Caesarean Section: a meta-analysis BJA 2011 ; 107; S.Hillyard et al. BJA 2011 ; 107:

15 Epidural top-up for emergency Caesarean section: conclusions of the meta-analysis Adding fentanyl to a local anaesthetic resulted in a significantly faster onset but did not affect the need for intraoperative supplementation. Bupivacaine or levobupivacaine 0.5% was the least effective solution. If the speed of onset is important, then a lidocaine and epinephrine solution, with or without fentanyl, appears optimal. If the quality of epidural block is paramount, then 0.75% ropivacaine is suggested. S.Hillyard et al. BJA 2011 ; 107:

16 Controversies and discussion Fœtal distress: 2-Chloroprocaine 3% or lidocaine 2% (+ adrenaline and fentanyl and bicarbonate or +CO 2 )? Which LA and how many do we need in our pharmacy? 16

17 Controversies and discussion? 17

18 Controversies and discussion T.Abboud et al. Anesth Analg 1983; 62:

19 Controversies and discussion T.Abboud et al. Anesth Analg 1983; 62:

20 Discussion: alkalinized lidocaine? Discussion: alkalinized lidocaine? M.Curatolo et al. Anesth Analg 1998;86:

21 Discussion: alkalinized lidocaine? M.Arakawa et al. Can J Anesth 2002;49:

22 Thank you! 22

23 some pharmacology Clinically, the onset of action is related to pka, dose, and concentration. pka when pka approximates the physiologic ph a higher concentration of non-ionized base is available, increasing onset of action. Local anesthetics are weak bases and contain a higher ratio of ionized medication compared to non-ionized. In the cell, the non-ionized and ionized forms equilibrate Dose- the higher the dose of local anesthetic administered, the faster the onset. Concentration- higher concentrations of local anesthetic will result in a more rapid onset. 23

24 some pharmacology 24

25 some pharmacology Local anesthetics with a pka closest to the physiological ph generally have a higher concentration of non-ionized molecules and a more rapid onset. Two notable exceptions are chloroprocaine and benzocaine. Chloroprocaine has a high pka and rapid onset. 25

26 some pharmacology Local anesthetics are prepared as a water soluble hydrochloride salt and generally have a ph of 5-6. If the commercial preparation contains epinephrine, the solution must be acidic to create a stable environment. The corresponding ph is in the range of 3-4. Commercial preparations with epinephrine have less free base, slowing the onset of action. To enhance clinical onset, carbonated solutions of epinephrine containing local anesthetics have been used instead of HCL solutions. Alternatively, adding sodium bicarbonate to commercial preparations of epinephrine containing local anesthetic solutions can hasten the onset. Altering the ph to a more basic solution will increase the amount of non-ionized compared to ionized which will speed onset. Sodium bicarbonate increases the amount of free base, increases onset, improves the quality of the block, and decreases pain associated with subcutaneous infiltration. 26

27 Lidocaine CO 2 LidoCO 2 : The onset of action with Xylocaine CO 2 is faster than regular lidocaine HCl solutions. The rapid diffusion of the carbon dioxide released from the injectate results in a lowering of intracellular ph. This, in turn, causes faster absorption of the lidocaine base, the active form of Xylocaine CO 2. In addition, the carbon dioxide may have an additive effect on the conduction block, resulting in a more intense motor block. Adding bicarbonate: The increase in ph increases the amount of nonionized local anesthetic which is the form that diffuses through the lipid phase of the neural membrane. CO 2, produced by the addition of bicarbonate and bicarbonate per se reduce the margin of conduction safety of the neural membrane. Moreover, CO 2 penetrates into the nerve, where it may determine trapping of the active cationic formof local anesthetic by acidifying the axoplasm. 27