Technological Advancements in the Objective Assessment of Nociception

Technological Advancements in the Objective Assessment of Nociception

Ana Castro (University of Porto, Portugal) and Pedro Amorim (Investigação Clínica do Serviço de Anestesia – Hospital de Santo António, Centro Hospitalar do Porto, Portugal)
Copyright: © 2015 |Pages: 10
DOI: 10.4018/978-1-4666-5888-2.ch337
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Background

General anesthesia is a drug induced state, usually described as a triad of hypnosis, analgesia and paralysis (see Figure 1).

Figure 1.

General anesthesia triad of hypnosis, analgesia and paralysis, and some of the correspondent physiological signals used in clinical practice to assess the patients’ state in each component

For each component, the anesthesiologist administers specific drugs, aiming at an optimum combined state, conditioned by patient's characteristics, clinical background, and individual response to the treatment (Enderle, Blanchard, & Bronzino, 2005).

Both for the hypnosis and paralysis, simple and easy to use indexes have been developed (Jameson & Sloan 2006), nonetheless, for the analgesia component, this is still an open research question. Currently, anesthesiologists rely on physiological signals related to the autonomous nervous system to indirectly assess adequacy of analgesia (see Figure 1). Analgesia and pain are very difficult to objectively assess, and a tool, similar to what clinicians have available for the paralysis and hypnosis components, would most certainly aid them in the adequate control of this component, translating the noxious activation (nociception) and attenuation provided by the analgesic (anti-nociception), and allow for the quantification of the optimum state in the nociception/anti-nociception (Noc/ANoc) continuum, to assure patient’s homeostasis.

Nociception activity is initiated by nociceptors, sensors capable of detecting mechanical, thermal or chemical changes that rise above a certain threshold, triggering the nociceptive responses (Gannong, 2005; Rhoades & Bell, 2009), such as tachycardia, blood pressure (BP) increase, vasoconstriction, sweating, among others.

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Nociception Objective Monitoring

Most of the methods proposed in the literature are based on altered cardiovascular state, and electroencephalogram (brain electrical activity, EEG) derived indexes variability in response to noxious activation. In the following subsections, the different methods proposed will be reviewed and discussed.

Key Terms in this Chapter

Electroencephalogram (EEG): A recording of brain electrical activity.

Photoplethysmography (PPG): A recording of pulse wave as measured by blood flow and light absorption.

Nociception: The nervous activation that arises when a stimulus has enough energy for potential tissue damage.

Nociception/Anti-Nociception Monitoring: Noxious activation needs to be controlled by the use of potent analgesics, and the balance between noxious activation and the anti-noiception provided by these drugs needs to be monitored in order to prevent harmful consequences of excessive noxious activation and iatrogenic effects.

Evoked Potential: The nervous action potential elicited by a known precise stimulus, and measured along the anatomical pathway for higher processing.

Electrocardiogram (ECG): A recording of heart electrical activity.

General Anesthesia: A drug induced state usually described as a combined state of analgesia, hypnosis and paralysis, by the use of very potent anesthetic drugs.

Electromiography (EMG): A recording of muscle electrical activity.

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