Mechanisms of controlled hypotension during propofolremifentanil or desflurane-remifentanil anaesthesia for paediatric ENT surgery

10AP3-2

Background and Goal of Study: Controlled hypotension (CH) with propofol-remifentanil (PRO-REM) or desflurane-remifentanil (DES-REM) is used in selected paediatric ENT procedures to reduce bleeding and improve visibility in surgical field.

To our knowledge, there are no studies showing haemodynamic mechanisms of CH. Therefore, we aimed to compare PRO-REM and DES-REM with regard to cardiovascular changes during CH.

Materials and Methods: After Ethics Comitee approval and parental informed consent, 41 children ASA I-II scheduled for nose, sinus or middle ear surgery were studied. We randomized patients to PRO (n=21, 12±3yrs, 41±11kg) or DES (n=20, 13±3yrs, 45±16kg) groups. In PRO gr anaesthesia was maintained with PRO 3-4 mg kg^-1h^-1, in DES gr with DES/O₂/air, ETconc 3-4%. We used REM 0.75 μg kg^-1min^-1 for analgesia and CH [1]. IPPV was used (ETCO₂35-40 mmHg).

We aimed to maintain controlled hypotension (MAP 50-65 mmHg) and analyse HR, CI, SVI, SVRI during this period. Haemodynamic parameters were measured with non-invasive cardiac output monitor (NICO, Philips-Respironix, USA).

Results and Discussion: Controlled hypotension can be achieved through reduction of CI and/or SVRI: MAP=CIxSVRI.

Table: [Haemodynamic parameters during CH]

CI was normal [2] (N) in 91% of measurements in DES gr; in PRO gr N in 72% and below N (< 3.5 l min^-1m^-2) in 27%. SVI was above N (>60 ml beat^-1m^-2) in 92% of measurements in DES gr and in 58% in PRO gr. SVRI was N in 84% of measurements in PRO gr; in DES gr N in 63% and below N (< 800 dyn s cm^-5m²) in 37%. ↑ SVI in response to ↓ HR and ↓ SVRI was more pronounced in DES gr.

Conclusion(s): Controlled hypotension in DES-REM gr results mainly from SVRI reduction, and in PRO-REM gr from CI reduction. While in both groups HR was decreased due to REM infusion, bradycardia was more pronounced and better compensated by SVI increase in DES group, which allowed for better maintenance of normal CI.