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Signa Vitae

A Journal In Intensive Care And Emergency Medicine

Tag: cardiac output

Comparison of haemodynamic parameters between the high and low spinal block in young healthy patients

Abstract

Background. For some surgical procedures a higher sensory block is needed. However, it is complicated by a higher incidence of hypotension, more bradycardia and nausea and a higher use of vasoactive drugs. In elderly and obstetric population complications have been attributed to the decrease in cardiac output and systemic vascular resistance, especially in a high block (above Th6). The aim of our study was to find the incidence of hypotension and bradycardia after a spinal anaesthesia in young, healthy patients. As young patients compensate more, we aimed to find the difference in haemodynamic variables between the group with a high and the group with a low spinal block and the underlying mechanisms of hypotension.

Methods. In a prospective, randomized study 44 American Society of Anaesthesiologists (ASA) 1 patients scheduled for knee arthroscopy under spinal anaesthesia were randomly distributed to a high (group H) and a low (group L) spinal block group. In a group H patients were placed into horizontal, whereas in a group L in 15-degree anti-Trendelenburg position immediately after the spinal block. Haemodynamic parameters were measured continuously noninvasively from 10 min before to 25 min after the spinal block using the CNAPTM device with the LiDCORapid monitor.

Results. The differences in haemodynamic parameters between the groups were not statistically significant at all measured times despite a significant difference in the spinal block level (18.5 vs 13.3 dermatomes above S5, p<0.001) and a significant difference in haemodynamic variables inside each group compared to the baseline value. With cardiac index (CI) as a dependent variable, a significant correlation between CI and stroke volume index (SVI) was found (β=0.849, p<0.001) and also between CI and heart rate (HR) (β=0.573, p<0.001). In group H the incidence of hypotension was 35%, whereas in group L it was 10%. The same difference was seen in the use of phenylephrine between the groups, however the difference was not significant.

Conclusion. In our study it was found that in young, healthy patients there are no significant differences in haemodynamic parameters and in incidence of hypotension between a high and low spinal block. Young, healthy patients compensate a decrease in systemic vascular resistance caused by the spinal anaesthesia with a compensatory increase in CI resulting from an increase in SVI and HR. However, a trend towards less hypotension, less bradycardia and less frequent phenylephrine use in a low spinal block was noted.

Key words: spinal anaesthesia, hyperbaric bupivacaine, haemodynamic parameters, cardiac output, hypotension

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Comparison of haemodynamic parameters between the high and low spinal block in young healthy patients

Abstract

Background: For some surgical procedures a higher sensory block is needed. However, it is complicated by a higher incidence of hypotension, more bradycardia and nausea and a higher use of vasoactive drugs. In elderly and obstetric population complications have been attributed to the decrease in cardiac output and systemic vascular resistance, especially in a high block (above Th6). The aim of our study was to find the incidence of hypotension and bradycardia after a spinal anaesthesia in young, healthy patients. As young patients compensate more, we aimed to find the difference in haemodynamic variables between the group with a high and the group with a low spinal block and the underlying mechanisms of hypotension.

Methods: in a prospective, randomized study 44 ASA 1 patients scheduled for knee arthroscopy under spinal anaesthesia were randomly distributed to a high (group H) and a low (group L) spinal block group. In a group H patients were placed into horizontal, whereas in a group L in 15-degree anti-Trendelenburg position immediately after the spinal block. Haemodynamic parameters were measured continuously noninvasively from 10 min before to 25 min after the spinal block using the CNAPTM device with the LiDCORapid monitor.

Results: The differences in haemodynamic parameters between the groups were not statistically significant at all measured times despite a significant difference in the spinal block level (18.5 vs 13.3 dermatomes above S5, p<0.001) and a significant difference in haemodynamic variables inside each group compared to the baseline value. With cardiac index (CI) as a dependent variable, a significant correlation between CI and stroke volume index (SVI) was found (β=0.849, p<0.001) and also between CI and heart rate (HR) (β=0.573, p<0.001). In group H the incidence of hypotension was 35%, whereas in group L it was 10%. The same difference was seen in the use of phenylephrine between the groups, however the difference was not significant.

Conclusion: In our study it was found that in young, healthy patients there are no significant differences in haemodynamic parameters and in incidence of hypotension between a high and low spinal block. Young, healthy patients compensate a decrease in systemic vascular resistance caused by the spinal anaesthesia with a compensatory increase in CI resulting from an increase in SVI and HR. However, a trend towards less hypotension, less bradycardia and less frequent phenylephrine use in a low spinal block was noted.

Keywords: spinal anaesthesia, hyperbaric bupivacaine, haemodynamic parameters, cardiac output, hypotension

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Multimodal monitoring (MMM) in the perioperative period

Abstract

Routine anaesthesia monitoring until the mid-1980s often consisted of just a finger on the pulse, primitive ECG and intermittent blood pressure (MAP) measurement using a cuff and aneroid gauge or mechanical oscillotonometer. Then in quick succession an explosion of new monitors was introduced including pulse oximetry (SpO2), end tidal carbon dioxide (EtCO2) and anaesthetic agent monitoring as well as automated non-invasive blood pressure (NIBP) machines. These were all routinely in place in many hospitals by the late 1980’s, but then progress came to a halt with no advances in routine anaesthetic monitoring for over 25 years.

This paper concentrates on three classes of non- or minimally invasive monitors which have become additionally available in the last 10 to 15 years and if used in combination their potential impact on improving outcome following surgery in high risk patients:

  1. Monitors which calculate stroke volume (SV, and thus cardiac output, CO) from a standard radial arterial line (e.g. LiDCO, UK), oesophageal probe (Deltex, UK), ECG pads or even from the finger
  2. Monitors which assess the degree of cortical suppression (e.g. BIS, Medtronic, USA) produced by anaesthetics thus potentially allowing the administrator to “fine tune” anaesthesia for individual patients
  3. Monitors which assess tissue oxygenation, usually of the brain (e.g. Invos, Medtronic, USA)

If used together they provide complementary information which should improve perioperative haemodynamic management and outcome and form part of a multi-modal monitoring (MMM) strategy which is the subject of this article.

Key words: cardiac output, minimally invasive, tissue oxygenation, depth of anaesthesia, multi-modal monitoring

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Mini invasive hemodynamic monitoring: from arterial pressure to cardiac output

Abstract

To evaluate the Cardiac Output (CO) the standard invasive pulmonary artery catheter (PAC) is considered today the gold standard. The major criticism to the PAC is that its level of invasiveness is not supported by an improvement in patient’s outcome. The interest to lesser and lesser invasive techniques is high. Therefore, the alternative techniques have been recently developed.
Cardiac Output can be monitored continuously by different devices that analyze the arterial waveform to track changes in stroke volume (SV) and CO. The analysis of the arterial pressure wave to determine cardiac output is classified as Pulse Contour analysis or Pulse Pressure Analysis. Starting from a similar principle three main devices are now available on the market, with different algorithms and features:

• PiCCO System (Pulsion Medical System, Munich, Germany)
• LiDCOTM plus System (LidCO, Cambridge, UK)
• Flotrac technology and Vigileo Monitor (Edwards Lifesciences, Irvine, CA, USA).

The algorithm used by all these devices has been also implemented even with the analysis of the variation of stroke volume (SVV) and of the pulse pressure (PPV). SVV and PPV represent the variation of stroke volume and of the pulse pressure during the respiratory cycle. In sedated ventilated patients these indexes have proven to predict the response to a fluid challenge. A high variation (>10-12%) identifies with good sensitivity and specificity responders and not responders.

Key words: cardiac output, arterial pressure, stroke volume variation, pulse pressure variation

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Thoracic electrical bioimpedance theory and clinical possibilities in perioperative medicine

Abstract

This article is a short review of thoracic electrical bioimpedance (TEB) theory and clinical capabilities. Cardiac output measurement is used primarily to guide therapy in complex, critically ill patients. Thoracic electrical bioimpedance is one of several noninvasive techniques that have been investigated to measure cardiac output and other hemodynamic parameters. Opinions in current literature continue to be conflicting as to the utility of thoracic electrical bioimpedance to that purpose. There is a limited number of good designed studies but they imply TEB is an accurate and reliable noninvasive method for determining cardiac output/cardiac index and it would be valuable for patients and circumstances in which intracardiac pressures and mixed venous blood samples are not necessary.

Key words: bioimpedance, non-invasive hemodynamic monitoring, cardiac output, pulmonary artery catheter, thermo dilution

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