title: Haemodynamic changes during craniotomy monitored by a bioimpedance plethysmographic noninvasive cardiac output monitor.
abstract: BACKGROUND
  Profound cardiovascular changes may occur at various stages during a craniotomy. These changes require a detailed haemodynamic analysis including cardiac output. In the present study, we used a monitor based on electrical bioimpedance method for noninvasive cardiac output measurement.
  
  
  METHODS
  In 17 ASA I and II patients undergoing elective craniotomies for supratentorial tumours, the following haemodynamic parameters were measured noninvasively: heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR). Haemodynamic changes in response to the following events were studied: (a) induction of anaesthesia with thiopentone, (b) 15 min of air-O(2)-isoflurane anaesthesia, (c) infiltration of the scalp with lidocaine adrenaline mixture, and (d) change of inspired gas mixture to N(2)O-O(2)-isoflurane.
  
  
  RESULTS
  HR increased (P < 0.001) and SV decreased (P < 0.001) while CO remained unchanged, one min after administration of thiopentone. After 15 min of isoflurane anaesthesia, HR increased (P < 0.001) and, SBP (P = 0.02), DBP (P = 0.002) and SV (P = 0.003) decreased significantly without change in CO. Three minutes after infiltration of the scalp with lidocaine-adrenaline mixture, there was an increase in SBP (P = 0.001), DBP (P = 0.007), SV (P = 0.007) and CO (P = 0.001) and a decrease in SVR (P < 0.001). Addition of nitrous oxide (60%) to the inspired gas mixture decreased SBP (P = 0.003) and DBP (P = 0.001) with a trend for decrease in CO (P < 0.1). The changes recorded in the present study conform to those that have been documented earlier by using invasive monitoring.
  
  
  CONCLUSIONS
  Bioimpedance plethysmography is a useful noninvasive technique for monitoring and detailed analysis of the rapidly changing systemic haemodynamics during a craniotomy. The device could be useful for investigating important haemodynamic changes in specific neurosurgical settings.
authors.affiliation: Department of Neuroanaesthesia, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Zulfiqar
authors.initials: Z
authors.lastname: Ali
authors.forename: G S
authors.initials: GS
authors.lastname: Umamaheswara Rao
authors.forename: A
authors.initials: A
authors.lastname: Jaganath
mesh_terms: D000328:Adult; D002302:Cardiac Output; D003399:Craniotomy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D010992:Plethysmography, Impedance / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015173:Supratentorial Neoplasms / Q000175:diagnosis* / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000379:methods*