Haemodynamic Monitoring during elective Caesarean section: the good, the bad & the ugly

1. Haemodynamic Monitoring during elective Caesarean section: the good, the bad & the ugly Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee, Bryan YW Ng, Floria F Ng, Lester AH Critchley. Department of Anaesthesia & Intensive Care The Chinese University of Hong Kong Hong Kong, China

2. Introduction • Spinal anaesthesia is now the most popular choice of anaesthesia for CS • High incidence of hypotension • Prompt treatment of hypotension will minimize maternal & neonatal morbidity

3. Background MAP = CO x SVR Spinal Anaesthesia • Reduction in SVR • Compensatory increase in CO to maintain MAP • Thus ∆ CO- early marker of hypotension

4. Objectives To evaluate the capability of • Finometer • RheoCardioMonitor (RCM) and • Ultrasonic cardiac output monitor (USCOM) to detect real-time haemodynamic changes in parturients receiving spinal anaesthesia for elective Caesarean section

5. CO Non-invasive Monitoring Finometer • BP, HR • Arterial volume-clamp method (Peñáz) • Continuous Waveform • Cardiac Output (CO) • Modelflow method (TNO-BMI, Wesseling) • Beat-to-beat continuous readings (SV, TPR) HR BP Arterial trace

6. Non-invasive Monitoring RheoCardioMonitor (RCM) • Trans-thoracic electrical bioimpedance (TEB) • Ohm’s law: ∆Z = ∆V/I • dZ/dt (Impedance changes): • Aortic blood flow • Proportional to SV • Continuous measurements of CO

7. Non-invasive Monitoring Ultrasonic cardiac output monitor (USCOM) • Continuous-wave Doppler ultrasound • Blood flow across heart valves • Through supra-sternal notch • Flow = Area x Velocity x cosθ • Intermittent measurements of CO

8. Methods • Ethics Committee approval • Informed written consent • ASA I-II term parturient • Elective Caesarean Section under spinal anaesthesia

9. Non-invasive Monitoring • Routine monitoring using anaesthetic machine (Narkomed-4) • 1-min cycle NIBP • SpO2 • ECG

10. Standard Monitor & PC for data capture Finometer USCOM RCM Spirit level

13. Anaesthetic Management • Routine, protocol-based spinal anaesthesia • 2.0ml heavy Bupivacaine 0.5% + Fentanyl 15µg (0.3ml) • Sensory dermatome of at least T7 (pinprick) • Management of hypotension - Phenylephrine 100µg bolus if systolic BP < 90mmHg

14. Methods • Hypotension: Narkomed (1-min) • Systolic BP < 90mmHg • Hypotension: Finometer (Beat-to-beat) • Systolic BP < 20% baseline • Non-invasive cardiac output measurements: • Cardiac output < 10% baseline • Finometer • RheoCardioMonitor (RCM) • Ultrasonic Cardiac Output Monitor (USCOM)

15. Results • 10 patients studied • 36 hypotensive episodes detected throughout surgery • No specific hypotension-induced complications

16. Results • Part I: Detection of compensatory increase of cardiac output (+10%) prior to hypotension

17. Results • Part II: Detection of decompensation (cardiac output -10%) prior to hypotension

18. Results • Part III: Finometer vs Standard 1-min NIBP Detection of Hypotension • 78.7s earlier than standard 1-min NIBP Normotension after Phenylephrine injection • 30.3s earlier than standard 1-min NIBP

19. Case Illustration

20. Spinal anaesthesia Phenylephrine injection Overshoots of BP Blood Pressure (mmHg) Blood Pressure (mmHg) 90mmHg Time

21. Non-invasive blood pressure by Narkomed

22. Non-invasive Systolic BP recorded by Narkomed

23. 200 180 160 140 120 100 Systolic BP (mmHg) 80 60 40 20 0 11:25:16 11:27:57 11:30:38 11:33:19 11:36:00 11:38:41 11:41:22 11:44:03 11:46:44 11:49:25 11:52:06 11:54:47 11:57:28 12:00:09 12:02:50 12:24:18 12:26:59 11:06:29 11:09:10 11:11:51 11:14:32 11:17:13 11:19:54 11:22:35 12:21:37 10:55:45 10:58:26 11:01:07 11:03:48 12:05:31 12:08:12 12:10:53 12:13:34 12:16:15 12:18:56 Narkomed SYS BP mmHg Fino SYS BP in mmHg Non-invasive SYS BP trend by Narkomed & Finometer

24. Evaluation - Finometer • The Good: • Simple setup & stable • Beat-to-beat • No risk & patient discomfort • Non-invasive • Patient shivering • Early detection of haemodynamic events • Reliable trending of blood pressure • The Bad & Ugly: • Absolute readings not accurate (cf. arterial line) • Drift - prolonged use (90 mins)

25. Evaluation - RheoCardioMonitor • The Good: • Simple & convenient • Non-invasive with no risk & discomfort • Continuous monitoring • The Bad & Ugly: • Inaccuracy - Cardiac conditions • Obesity (Poor electrode skin contact) • Patient movement • Surgical diathermy

26. Interference of RCM signal when surgical diathermy is used

27. Evaluation - USCOM • The Good: • Portable & safe • Non-invasive & easy to use • Minor patient discomfort • Instant readings of cardiac output and waveform • Dx of pathological conditions • The Bad & Ugly: • Intermittent readings • Highly operator-dependent • Difficult signal retrieval (Inter-patient variation)

28. Conclusions • Haemodynamic Monitoring during elective Caesarean section: the good, the bad & the ugly • 1. Finometer can track changes in blood pressure and promptly recognize hypotension earlier. • 2. Finometer & RCM are potentially useful for detecting cardiac output changes and allow rapid assessment & management of hypotension during elective CS. • 3. The USCOM is less capable for tracking rapid cardiac output changes but provides more accurate absolute measurements.

29. Haemodynamic Monitoring during elective Caesarean section: the good, the bad & the ugly Department of Anaesthesia & Intensive Care The Chinese University of Hong Kong Hong Kong, China.

31. Precision of Measurements • Correlation coefficient: Overall mean (range) r = 0.79 (0.59-0.93) • Bland and Altman Plot: Mean Bias: -17mmHg 95% Limits of agreement (-34 to 17 mmHg) Error (1.96 SD/mean) of ± 18%

32. Non-invasive blood pressure recorded by Narkomed