Regional Anaesthesia for Caesarean Section

Transcription

1 Regional Anaesthesia for Caesarean Section "The Best Recipe" Warwick D. Ngan Kee Dept of Anaesthesia & Intensive Care The Chinese University of Hong Kong

2 What I will not do. Magic recipes One shoe to fit all

3 What I will do. Discuss selected controversial issues Practical recommendations

4 BASICS Preassessment Premedication Consent Monitoring Vascular access Postop analgesia

5 OUTLINE Techniques Drug Choice Drug Dose Fluids Vasopressors Oxygen

6 O P T I O N S Epidural Spinal CSE Time Simplicity Drug Dose Block Quality Hypotension Duration Recovery

7 OUTLINE Techniques Drug Choice

8 Local Anaesthetic Bupivacaine

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10 Onset Speed (time to T5 block) Sia et al. (Cochrane Review)

11 Conversion to General Anaesthesia Sia et al. (Cochrane Review)

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13 Block Height Coefficient of variation: 17.7% 21.9% Khaw et. Anesth Analg 2002;94:680-5.

14 Additives Opioids Adrenaline Clonidine Neostigmine Ketamine

15 Adding adjunct agents Possible advantages: 1. Decrease side effects 2. Increase efficacy

16 Adding adjunct agents Possible Disadvantages: 1. Drug error 2. Breach of sterility 3. Incompatibility 4. Cost 5. Safety (often off-label )

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18 Elective Spinal Caesarean (n=56) Height-adjusted IT Bupivacaine Added Fentanyl 0-50 µg Quality of Block Intraoperative Analgesic Requirement Hunt et al. Anesthesiology 1989;71:

19 Intraoperative Opioid Supplementation 100 Intraop Opioid (%) % 50% % 0% 0% 0% 0% 0% Fentanyl Dose (µg) Hunt et al. Anesthesiology 1989;71:

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21 Manullang et al. Anesth Analg 2000;90: Elective Spinal Caesarean (n=30) Hyperbaric Bupivacaine 12 mg IV Ondansetron 4 mg IT Fentanyl 15 µg FENTANYL: Less intraoperative pain FENTANYL: Less intraoperative nausea

22 OUTLINE Techniques Drug Choice Drug Dose

23 Single shot spinal Dose required for adequate spinal block

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25 Low Dose ( 8 mg bupivacaine) VS Conventional Dose (> 8 mg bupivacaine)

26 HYPOTENSION: Low Dose vs Conventional Dose Arzola and Wieczorek. Br J Anaesth 2011;107:308-18

27 NAUSEA/VOMITING: Low Dose vs Conventional Dose Arzola and Wieczorek. Br J Anaesth 2011;107:308-18

28 SUPPLEMENTATION: Low Dose vs Conventional Dose Arzola and Wieczorek. Br J Anaesth 2011;107:308-18

29 Low dose bupivacaine.compromises anaesthetic efficacy despite the benefit of lower maternal side effects Lower anaesthetic doses cannot be recommended unless an epidural catheter is in place (CSE)

30 ecommendation: Use smallest dose of LA for circumstances Add opioid (fentanyl/sufentanil) CSE: useful for high-risk or long surgery

31 OUTLINE Techniques Drug Choice Drug Dose Fluids

32 Intravenous fluids Uncertainties: Why? What? When? How much? How fast?

33 IV Fluid: Type and Timing Prehydration Cohydration Crystalloid Colloid ( )

34 CLINICAL INVESTIGATIONS Anesthesiology 1999; American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins, Inc Effects of Crystalloid and Colloid Preload on Blood Volume in the Parturient Undergoing Spinal Anesthesia for Elective Cesarean section Hiroshi Ueyama, M.D.,* Yan-Ling He, Ph.D., Hironobu Tanigami, M.D.,* Takashi Mashimo, M.D., Ikuto Yoshiya, M.D.

35 Ueyama et al. Anesthesiology 1999;91: Elective Caesareans (n=36) Lactated Ringers 1.5 L HES 0.5 L HES 1.0 L Hypotension Blood volume & cardiac output

36 Blood Volume increase (L) Blood volume increase Hypotension incidence LR 1.5L HES 0.5L HES 1.0L Hypotension incidence (%) Adapted from Ueyama H et al. Anesthesiology 1999; 91:1561-6

37 Colloid Prehydration: D I S A D V A N T A G E S Cost. Effects on coagulation. Fluid overload. Hemodilution. Allergic reactions.

38 Recommendation: Crystalloid: cohydration Colloid: prehydration or cohydration Don't rely on IV fluids Don't delay for IV fluids

39 OUTLINE Techniques Drug Choice Drug Dose Fluids Vasopressors

40 Phenylephrine

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42 % % 42% Vasopressors at Caesarean section 51% 4.5% 6% 0.4% Ephedrine Phenylephrine Other

43 Why use phenylephrine? Phenylephrine is more effective Ephedrine causes fetal acidosis

44 Ephedrine depresses fetal ph and BE Figure 1. Meta-analysis of trials - effect on umbilical arterial ph Favours ephedrine Favours phenylephrine Alahuhta Hall LaPorta Moran Pierce Thomas Overall effect Weighted mean difference (umbilical cord arterial blood ph) Lee A, Ngan Kee WD, Gin T. Anesth Analg 2002;

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46 Ngan Kee WD Anesthesiology 2009; 111: Placental Transfer of Ephedrine and Phenylephrine Umbilical Venous : Maternal Arterial 1.13 Ephedrine 0.17 Phenylephrine (Median values) * P < *

47 pg/ml pg/ml mmol/l mg/dl 5 UA Lactate UA Glucose (all P < 0.05) Ephedrine Phenylephrine 50 Ephedrine Phenylephrine UA Adrenaline UA Noradrenaline Ephedrine Phenylephrine Ephedrine Phenylephrine Ngan Kee WD Anesthesiology 2009; 111:506-12

48 Optimal Target Blood Pressure? Keeping blood pressure near baseline gives better maternal outcome

49 Elective Spinal Caesareans (n=75) Crystalloid Prehydration Phenylephrine Infusion Three Target Blood Pressures 80% of Baseline 90% of Baseline 100% of Baseline

50 Incidence of Nausea/Vomiting % 16% 4% 0 Gp80 Gp90 Gp100 Ngan Kee et al. Br J Anaesth 2004;92:469-74

51 How best to use phenylephrine? Preparation Method of administration Timing of administration

52 Dilute carefully..

53 Timing... Prevention versus Treatment Most effective management: Start administration immediately after intrathecal injection

54 Method. Infusion versus Boluses Both effective Intermittent bolus simple Infusion convenient Infusion less work

55 INFUSION: Less hypotension More hypertension Less nausea/vomiting Fewer physician interventions

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57 Recommendation: Infusion technique: Syringe pump Start 50 µg/min immediately after induction Measure BP Q1min Increase rate if BP falls Decrease/stop if BP increases

58 Recommendation: Bolus technique: Bolus dose: µg Begin immediately after IT injection Measure BP Q1min Further boluses when BP start to decrease

59 Recommendation: What about bradycardia? Associated with cardiac output Tolerate to bpm BP high/normal: stop and wait! BP low: IVF, ephedrine, atropine/glycopyrrolate* * Beware hypertension with anticholinergics!

60 Recommendation: What about high risk cases? Preeclampsia Fetal compromise Few studies Less vasopressor needed Use less aggressive dosing

61 OUTLINE Techniques Drug Choice Drug Dose Fluids Vasopressors Oxygen

62 O X Y G E N Should I (not) give oxygen? Does it do any good? Can it do any harm?

63 POTENTIAL B E N E F I T S Increase fetal oxygenation Reduce effects of hypoventilation Protection during prolonged U-D time Reduce effects of hypotension Safety in conversion to GA Decrease nausea & vomiting Decrease wound infection

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66 Elective C-sections (n=204) High flow venturi facemask Air 40% O 2 60% O 2 Cord gases & O 2 content. Subanalysis for U-D time >180 s Khaw, Ngan Kee et al. Br J Anaesth 2004; 92:

67 UV PO 2 (mmhg) % 40% 32 * 60% * P = UV Hb Saturation (%) % 40% ** 70 60% ** P = UV O 2 Content (ml/dl) % 40% *** % *** P = Khaw KS, Ngan Kee WD et al. Br J Anaesth 2004; 92:

68 O X Y G E N Should I (not) give oxygen? Does it do any good? Can it do any harm?

69 Oxygen free radical generation

70 It seems reasonable, based on current knowledge, to continue to give supplementary oxygen to mothers undergoing emergency/unplanned Caesarean section In healthy parturients undergoing elective Caesarean section, it would appear that additional oxygen is unnecessary.

71 Use spinal or CSE Summary Heavy bupivacaine + opioid Dose: empirical (low dose fentanyl 10-15µg)

72 Summary Crystalloid: cohydration Colloid: pre- or cohydration Don't rely on fluids Don't delay for fluids

73 Summary Phenylephrine or metaraminol Start early Keep BP near baseline Care with anticholinergics

74 Summary Routine O 2 unnecessary Be guided by pulse oximeter

75 Regional Anaesthesia for Caesarean Section "The Best Recipe" Warwick D. Ngan Kee Dept of Anaesthesia & Intensive Care The Chinese University of Hong Kong