Regional Anaesthesia for Caesarean Section "The Best Recipe" Warwick D. Ngan Kee Dept of Anaesthesia & Intensive Care The Chinese University of Hong Kong
What I will not do. Magic recipes One shoe to fit all
What I will do. Discuss selected controversial issues Practical recommendations
BASICS Preassessment Premedication Consent Monitoring Vascular access 1-2-3 Postop analgesia
OUTLINE Techniques Drug Choice Drug Dose Fluids Vasopressors Oxygen
O P T I O N S Epidural Spinal CSE Time Simplicity Drug Dose Block Quality Hypotension Duration Recovery
OUTLINE Techniques Drug Choice
Local Anaesthetic Bupivacaine
Onset Speed (time to T5 block) Sia et al. (Cochrane Review)
Conversion to General Anaesthesia Sia et al. (Cochrane Review)
Block Height Coefficient of variation: 17.7% 21.9% Khaw et. Anesth Analg 2002;94:680-5.
Additives Opioids Adrenaline Clonidine Neostigmine Ketamine
Adding adjunct agents Possible advantages: 1. Decrease side effects 2. Increase efficacy
Adding adjunct agents Possible Disadvantages: 1. Drug error 2. Breach of sterility 3. Incompatibility 4. Cost 5. Safety (often off-label )
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;71:535-40.
Intraoperative Opioid Supplementation 100 Intraop Opioid (%) 80 60 67% 50% 40 20 0 25% 0% 0% 0% 0% 0% 1 2 3 4 5 6 7 8 0 2.5 5 6.25 12.5 25 37 50 Fentanyl Dose (µg) Hunt et al. Anesthesiology 1989;71:535-40.
Manullang et al. Anesth Analg 2000;90:1162-6. 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
OUTLINE Techniques Drug Choice Drug Dose
Single shot spinal Dose required for adequate spinal block
Low Dose ( 8 mg bupivacaine) VS Conventional Dose (> 8 mg bupivacaine)
HYPOTENSION: Low Dose vs Conventional Dose Arzola and Wieczorek. Br J Anaesth 2011;107:308-18
NAUSEA/VOMITING: Low Dose vs Conventional Dose Arzola and Wieczorek. Br J Anaesth 2011;107:308-18
SUPPLEMENTATION: Low Dose vs Conventional Dose Arzola and Wieczorek. Br J Anaesth 2011;107:308-18
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)
ecommendation: Use smallest dose of LA for circumstances Add opioid (fentanyl/sufentanil) CSE: useful for high-risk or long surgery
OUTLINE Techniques Drug Choice Drug Dose Fluids
Intravenous fluids Uncertainties: Why? What? When? How much? How fast?
IV Fluid: Type and Timing Prehydration Cohydration Crystalloid Colloid - + + + ( )
CLINICAL INVESTIGATIONS Anesthesiology 1999;91 1571-6 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.
Ueyama et al. Anesthesiology 1999;91:1571-6. Elective Caesareans (n=36) Lactated Ringers 1.5 L HES 0.5 L HES 1.0 L Hypotension Blood volume & cardiac output
Blood Volume increase (L) 1.5 1.25 1.0 0.75 0.5 0.25 0 Blood volume increase Hypotension incidence LR 1.5L HES 0.5L HES 1.0L 100 90 80 70 60 50 40 30 20 10 0 Hypotension incidence (%) Adapted from Ueyama H et al. Anesthesiology 1999; 91:1561-6
Colloid Prehydration: D I S A D V A N T A G E S Cost. Effects on coagulation. Fluid overload. Hemodilution. Allergic reactions.
Recommendation: Crystalloid: cohydration Colloid: prehydration or cohydration Don't rely on IV fluids Don't delay for IV fluids
OUTLINE Techniques Drug Choice Drug Dose Fluids Vasopressors
Phenylephrine
% 100 90 80 70 60 50 40 30 20 10 0 95.2% 42% Vasopressors at Caesarean section 51% 4.5% 6% 0.4% Ephedrine Phenylephrine Other 1999 2007
Why use phenylephrine? Phenylephrine is more effective Ephedrine causes fetal acidosis
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 -0.10-0.05 0.00 0.05 0.10 Weighted mean difference (umbilical cord arterial blood ph) Lee A, Ngan Kee WD, Gin T. Anesth Analg 2002;94 920-6.
Ngan Kee WD Anesthesiology 2009; 111:506-12 Placental Transfer of Ephedrine and Phenylephrine 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 Umbilical Venous : Maternal Arterial 1.13 Ephedrine 0.17 Phenylephrine (Median values) * P < 0.0001 *
pg/ml pg/ml mmol/l mg/dl 5 UA Lactate UA Glucose (all P < 0.05) 4 3 2 1 65 60 55 0 Ephedrine Phenylephrine 50 Ephedrine Phenylephrine UA Adrenaline UA Noradrenaline 800 600 400 200 0 Ephedrine Phenylephrine 6000 5000 4000 3000 2000 1000 0 Ephedrine Phenylephrine Ngan Kee WD Anesthesiology 2009; 111:506-12
Optimal Target Blood Pressure? Keeping blood pressure near baseline gives better maternal outcome
Elective Spinal Caesareans (n=75) Crystalloid Prehydration Phenylephrine Infusion Three Target Blood Pressures 80% of Baseline 90% of Baseline 100% of Baseline
Incidence of Nausea/Vomiting 100 80 60 40 20 40% 16% 4% 0 Gp80 Gp90 Gp100 Ngan Kee et al. Br J Anaesth 2004;92:469-74
How best to use phenylephrine? Preparation Method of administration Timing of administration
Dilute carefully..
Timing... Prevention versus Treatment Most effective management: Start administration immediately after intrathecal injection
Method. Infusion versus Boluses Both effective Intermittent bolus simple Infusion convenient Infusion less work
INFUSION: Less hypotension More hypertension Less nausea/vomiting Fewer physician interventions
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
Recommendation: Bolus technique: Bolus dose: 50-100 µg Begin immediately after IT injection Measure BP Q1min Further boluses when BP start to decrease
Recommendation: What about bradycardia? Associated with cardiac output Tolerate to 50-60 bpm BP high/normal: stop and wait! BP low: IVF, ephedrine, atropine/glycopyrrolate* * Beware hypertension with anticholinergics!
Recommendation: What about high risk cases? Preeclampsia Fetal compromise Few studies Less vasopressor needed Use less aggressive dosing
OUTLINE Techniques Drug Choice Drug Dose Fluids Vasopressors Oxygen
O X Y G E N Should I (not) give oxygen? Does it do any good? Can it do any harm?
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
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: 518-22
40 30 20 10 0 UV PO 2 (mmhg) 28 29 21% 40% 32 * 60% * P = 0.003 UV Hb Saturation 100 80 60 (%) 40 63 67 20 0 21% 40% ** 70 60% ** P = 0.015 UV O 2 Content (ml/dl) 20 15 10 5 0 12.9 13.4 21% 40% *** 14.4 60% *** P = 0.015 Khaw KS, Ngan Kee WD et al. Br J Anaesth 2004; 92: 518-22.
O X Y G E N Should I (not) give oxygen? Does it do any good? Can it do any harm?
Oxygen free radical generation
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.
Use spinal or CSE Summary Heavy bupivacaine + opioid Dose: empirical (low dose fentanyl 10-15µg)
Summary Crystalloid: cohydration Colloid: pre- or cohydration Don't rely on fluids Don't delay for fluids
Summary Phenylephrine or metaraminol Start early Keep BP near baseline Care with anticholinergics
Summary Routine O 2 unnecessary Be guided by pulse oximeter
Regional Anaesthesia for Caesarean Section "The Best Recipe" Warwick D. Ngan Kee Dept of Anaesthesia & Intensive Care The Chinese University of Hong Kong