Palliative Sedierung im Lehrbuch für Palliative Care
Hg. Cornelia Knipping, Huber 2006 ( >>> PDF )

Pain and anxiety - an interrelation
D.Weixler, Dept. Anesthesia and Intensive Care, Landesklinikum Waldviertel Horn, Austria

According to the International Society of the Study of pain (IASP) pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

Pain has powerful emotional qualities . Any reasonable and unbiased observer studying mammals, particularly humans, would have to conclude that pain´s affective features, rather than it´s sensory properties, govern behavioural responses to injury. People who experience pain do not quietly report the fact: they express negative emotions.

As Chapman highlights in Chapter 24 in Bonica´s Management of Pain,
a) pain (awareness of tissue trauma) has emotional properties including negative emotional arousal
b) the brain creates bodily states and arousal (emotions) in response to threat to biologic integrity;
c) the affective dimension of pain involves hypervigilance, bodily arousal , and awareness of altered bodily states.

Protection of biological integrity is normally the mind´s highest priority. Injury-instigated physiologic processes involve the autonomic nervous system, the hypothalamo-pituitary-adrenocortical axis, and the immune system feed into the ongoing construction of somatic consciousness. Emotional responses to and cognitive appraisals of bodily changes that such process create threat into the fabric of pain, along with sensory awareness. Severe pain typically involves shifting one´s attention away from all else to one´s body, experiencing strong negative emotion, having an urge to escape injury, and mental preoccupation with the meaning of injury and disease. Pain is both a major mechanism for biologic protection and a powerful psychological experience. Severe pain takes over the mind by dominating the higher order processes of the brain and the behaviour that brain directs.

Emotions are complex states of physiologic arousal and awareness of input positive or negative hedonic qualities to a stimulus (event) in the internal or external environment. The objective aspect of emotion is autonomically and hormonally mediated physiologic arousal. The subjective aspects of emotion, feelings, are phenomena of consciousness. Emotion represents in consciousness the biological importance or meaning of an event to the perceiver.

Pain represents threat to the biological, psychosocial, or social integrity of the person. In this respect, the emotional aspect of pain is a protective response that normally contributes to adaption and survival. If uncontrolled or poorly managed in patients with severe or prolonged pain, it produces suffering. Because negative emotions , such as fear evolved to facilitate adaption and survival, emotion plays an important defensive role. The strength of emotional arousal with an injury indicates and expresses the magnitude of threat to the biological integrity of a person. Within the contents of consciousness, threat is a strong negative feeling state and not pure informational appraisal.

Pain captures and narrows attention, influencing attention, thinking ,processing and memory as well as forecasting and planning.
Pain is unpleasant, causes fatigue, impairs sleep and interferes with cognitive memory (as well as anxiety can cause the same).
Close association exists between thinking catastrophically, fear of pain and of reinjury, and attention (hypervigilance) to pain and other unpleasant somatic sensations Patient´s tendency to think the worst or to think catastrophically was positively associated with pain intensity and pain distress in acute burn patients.

Karl Jaspers, the philosopher said: "Anxiety is deriving of mortal fear, it is an expression of the narrowness, limitation, vulnerability and exhaustibility of our being. All fear for our position, our beloved, our health, all care is a symptome of the fundamental certainty, that our being is threatened and that we are exposed to omnipresent death" Fritz Riemann, German psychologist tells about anxiety, that "it is a reflection of our dependencies and mortality". Anxiety and pain are interrelated, pain generates the emotion anxiety - vice versa anxiety is augmenting pain. Pain and anxiety are triggers of the human stress response with hormonal, metabolic and immunologic consequences. Blood levels of cortisol, epinephrine, adiuretin-vasopressine, human somatotropic hormone, renin-angiotensin and cytokines will be elevated by the influence of pain and anxiety.

The neuroendocrine system and the immune-system have bidirectional connections: high levels of glucocorticoids alter immune response and augment the susceptibility of infections and tumors. Perioperative stress response can be triggered by stress, pain, trauma, hypothermia and surgery, leading to changes of the metabolic pathways (insulin-resistence, hyperglycemia etc.), to catabolism, negative nitrogen-balance and delayed wound healing. Oxygen demand will increase, changes in water and electrolyte balance (Retention of water and sodium, edema etc.) will occur in the presence of any trigger of human stress response.

The patient´s preoperative state influences intraoperative hemodynamics and postoperative demand of analgesics. Anxiety and sleep deprivation, hunger and thirst influence a patient´s wellbeing predominantly in the postoperative period. Pain significantly enhances the risk of pre- and postoperative anxiety in adults. Anxiety in the postoperative period can be reduced by regional anesthesia and spinal or epidural opioids. The risk of postoperative anxiety in children is increased 5-13-fold, when they will experience moderate to severe pain. One of the most predominant fears of a patient before surgery is fear of pain.

Analgesia has an important impact on wound healing, because it can decrease intensity of the posttraumatic stress response, epidural analgesia lessens protein catabolism and thus positively influences collagene formation. Pain is one of the major factors, delaying a patient´s recovery, pain management has priority for a patient´s outcome, good pain management will lower morbidity, mortality and increase patient´s satisfaction. Unfortunately many of the studies upon the effects of epidural anesthesia in major abdominal surgery lack an appropriate study design, as Holte and Kehlet point out.

A very nice review article on spinal and epidural anesthesia addresses the sedative effect of these methods. Liu et al. summarize, that spinal and epidural anesthesia have supraspinal effects, because it could be observed, that with a functioning centroaxial block the need for narcotics decreased. These effects could be demonstrated by using the bispectral-index-monitor, as an valid instrument for measuring depth of sedation.

The effects are seen under spinal in a double-peak manner: showing the first peak of sedation 30 minutes after spinal, the second after approximately 60 minutes. This phenomenon is dependent on the sensory level of the block, the higher the level, the deeper the sedative effect. The phenomenon was interpreted due to a reduction of afferent input to the "motor" of wakefulness, the ascending reticular system. Some authors hypothetize, that rostral spread of the local anesthetic may cause the sedative effects of spinal anesthesia.

It has to be taken into consideration, that additives contribute to sedation, when an epidural or spinal is used. Opioids (Fentanyl, Sufentanil, Morphine), the a-2-adrenoceptor-agonist Clonidine and the phenycyclidine-derivate S-+-Ketamine may lead to undue sedation, when added to any centroaxial technique. This must be taken into account, when anesthesiologists or the collegues on the wards want to add substances o therapy with sedative effects (antipsychotics, benzodiazepines, antihistaminics, opioids etc.).

Epidural opiods may ascend to the brainstem and cause respiratory depression, the more water-soluble morphine has a greater risk due to a broader spread of the substance. The more lipide-soluble agent sufentanil is more likely to be bound at the level of infusion, but delayed (12 hours)depression of the respiration may occur. Monitoring of respiratory rate has priority over observation of oxygen saturation, especially when a patient does not breath room air, but is on oxygen therapy. Monitoring is obligatory for more than 12 hours after the stop of an infusion, when opioids have been added to an epidural infusion.