Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 2022
Non-invasive measurement of pulse pressure variation using a finger-cuff method (CNAP system): a validation study in patients having neurosurgery.
The finger-cuff system CNAP (CNSystems Medizintechnik, Graz, Austria) allows non-invasive automated measurement of pulse pressure variation (PPVCNAP). We sought to validate the PPVCNAP-algorithm and investigate the agreement between PPVCNAP and arterial catheter-derived manually calculated pulse pressure variation (PPVINV). This was a prospective method comparison study in patients having neurosurgery. PPVINV was the reference method. ⋯ Deming regression showed a slope of 0.85 (95%-CI 0.78 to 0.91) and intercept of 0.10 (95%-CI -0.34 to 0.55). The predictive agreement between PPVCNAP and PPVINV was 82% and Cohen's kappa was 0.48. The PPVCNAP-algorithm reliably calculates pulse pressure variation compared to manual offline pulse pressure variation calculation when applied on the same arterial blood pressure waveform. The absolute and predictive agreement between PPVCNAP and PPVINV are moderate.
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J Clin Monit Comput · Apr 2022
Needle insertion forces and fluid injection pressures during targeting of nerves in a soft embalmed cadaver model.
Forceful needle-nerve contact and high subepineural pressures and are recognised causes of nerve damage. Pressure and force measurements are necessary to inform the mechanisms of nerve injury, build virtual simulator environments and provide operator feedback during simulation training. However, the range of pressures and forces encountered at tissue layers during targeted needle insertion and fluid injection are not known. ⋯ Pressure was greater at epineurium and within subepineurium than perineural tissue, geometric ratio (95% CI) 4.7 (3.0-7.3) kPa and 3.8 (2.5-5.7) kPa, respectively, both P < 0.0001. Force on nerve contact and on nerve penetration was greater than force in perineural tissue, geometric ratios (95% CI) 3.0 (1.9-4.7) N and 3.6 (2.2-7.5) N, respectively, both P < 0.0001. On nerve contact, 1 in 6 insertions were ≥ 5 N CONCLUSIONS: Despite valid infusion pressures, anaesthetists exerted excessive force on nerves.
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J Clin Monit Comput · Apr 2022
Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT).
Electrical impedance tomography (EIT) is used in lung physiology monitoring. There is evidence that EIT is linearly associated with global tidal volume (VT) in clinically healthy patients where no positive end-expiratory pressure (PEEP) is applied. This linearity has not been challenged by altering lung conditions. ⋯ The variance in VTEIT was best described by peak inspiratory pressure (PIP) and PEEP (adjusted R2 0.82) while variance in VTSpiro was best described by PIP and airway deadspace (adjusted R2 0.76). The relationship between VTEIT and VTSpiro remains linear with changes in tidal volume, and stable across altered lung conditions. This may have application for monitoring and assessment in vivo.
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J Clin Monit Comput · Apr 2022
Randomized Controlled TrialIntraarterial catheter diameter and dynamic response of arterial pressure monitoring system: a randomized controlled trial.
The dynamic response (DR) of the arterial pressure monitoring system (APMS) may depend on the intraarterial catheter (IAC) diameter. We hypothesized that adequate DR would be more common when using a smaller IAC. We compared the DR of the AMPS (Auto Transducer™) between three IACs (BD Angiocath Plus™) with different diameters. 353 neurosurgical patients were randomized into three groups undergoing catheterization with a 20-, 22-, or 24-gauge IAC: 20G (n = 119), 22G (n = 117), and 24G (n = 117) groups, respectively. ⋯ Registration Registry: ClinicalTrials.gov. Registration number: NCT03642756. Date of Registration: July 27, 2018.
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J Clin Monit Comput · Apr 2022
Observational StudyMechanisms contributing to hypotension after anesthetic induction with sufentanil, propofol, and rocuronium: a prospective observational study.
It remains unclear whether reduced myocardial contractility, venous dilation with decreased venous return, or arterial dilation with reduced systemic vascular resistance contribute most to hypotension after induction of general anesthesia. We sought to assess the relative contribution of various hemodynamic mechanisms to hypotension after induction of general anesthesia with sufentanil, propofol, and rocuronium. In this prospective observational study, we continuously recorded hemodynamic variables during anesthetic induction using a finger-cuff method in 92 non-cardiac surgery patients. ⋯ Anesthetic induction with sufentanil, propofol, and rocuronium reduced arterial pressure and systemic vascular resistance index. Heart rate, stroke volume index, and cardiac index remained stable. Post-induction hypotension therefore appears to result from arterial dilation with reduced systemic vascular resistance rather than venous dilation or reduced myocardial contractility.