Continuous non-invasive BP monitoring : service evaluation during induction of anaesthesia and haemodialysis

Background Routine induction of anaesthesia and maintenance haemodialysis are two examples of clinical procedures that exert a direct effect on the cardiovascular system. The exact incidence of haemodynamic instability during such procedures is not well described, as it would have required invasive intra-arterial monitoring, which is not justified for routine use. As part of two service evaluations, i.e. routine induction of anaesthesia and maintenance haemodialysis, we utilised a noninvasive continuous beat-by-beat haemodynamic monitor, which works using a finger cuff (Finometer), to assess the incidence of haemodynamic instability encountered during these procedures in comparison to the conventionally used intermittent noninvasive blood pressure (NIBP) measurement protocols. Methods Using the Finometer, we recorded haemodynamic variables during induction of anaesthesia in 100 patients undergoing elective surgery, and during maintenance haemodialysis in 25 patients with established renal failure. Firstly, we assessed the feasibility of using the Finometer during induction of anaesthesia and haemodialysis by evaluating its success rate in providing measurements of haemodynamic variables, and by assessing its accuracy in comparison to the readings obtained by the conventional NIBP devices during our service evaluations. Secondly, we assessed the incidence of haemodynamic instability during both procedures as detected by the Finometer in comparison to the existing conventional intermittent NIBP measurement protocols. Results and discussion The Finometer was successful in providing adequate haemodynamic monitoring in 96% and 86% of the attempts to use it in our service evaluations during induction of anaesthesia and haemodialysis respectively. The Finometer showed comparable accuracy in terms of BP monitoring to the conventional NIBP monitors during induction of anaesthesia and haemodialysis. A high incidence of significant hypotension as well as significant hypertension was shown during both, routine induction of anaesthesia and maintenance haemodialysis, which were underestimated or even missed by the conventionally used intermittent NIBP monitoring protocols. During induction of anaesthesia, 19% of the patients sustained an episode of hypotension defined as SBP less than 80 mmHg for more than 1 min, and 53% showed a transient increase of the SBP of more than 20% from baseline values. During Haemodialysis, 28% of the patients sustained an episode of hypotension defined as SBP less than 90 mmHg for more than 10 min, and 16% sustained an episode of severe hypertension defined as SBP more than 180 mmHg for more than 10 min. Conclusion Haemodynamic instability is commonly encountered during routine induction of anaesthesia and maintenance haemodialysis. Continuous noninvasive finger arterial haemodynamic monitoring is more reliable than the conventionally used protocols of intermittent NIBP monitoring in detecting such haemodynamic instability, thus providing higher levels of patient safety. Extra and early information about haemodynamic variables, as provided by the Finometer, may provide a better insight on the exact cause of haemodynamic instability, which may aid the physicians in prompt and targeted management.