Opioids Used in Primary Care for the Management of Pain: A Pharmacologic, Pharmacotherapeutic, and Pharmacodynamic Overview
Mark V. Boswell, B. Eliot Cole in Weiner's Pain Management, 2005
Opioids, by a dose–response relationship depress ventilation through brainstem respiratory centers, particularly respiratory rate and depth of respiration (minute ventilation) in patients at risk, especially with comorbidity. PaCO2 (arterial partial pressure of carbon monoxide) increases and the response to a CO2 challenge is blunted. This results in a shift of the CO2 response curve down and to the right. These effects are mediated in the brainstem at the respiratory center. The hypoxic drive is decreased, and the apneic threshold (highest PaCO2 at which a patient remains apneic) is increased. These effects are not usually clinically significant at typical therapeutic doses in otherwise healthy patients. Opioids, such as morphine, may induce histamine release causing bronchospasm in susceptible patients. Also, opioids cause a depression of the cough reflex center in the medulla creating antitussive activity (Barkin & Barkin, 2001; Barkin et al., 2005; Bonica, 1990; Cherny et al., 2001; McEvoy, 2004; Reisine & Pasternak, 1996; Reves, 2002; Sabbe & Yaksh, 1990; Wickersham, 2003).
Battlefield Chemical Inhalation Injury
Jacob Loke in Pathophysiology and Treatment of Inhalation Injuries, 2020
Signs and symptoms of exposure generally are limited to the effects of cholinesterase inhibition. Generally within minutes of a topical exposure and within 30 sec or less of an inhalational exposure symptoms of nervousness, headache, blurred vision, weakness, nausea, intestinal cramping, diarrhea, chest tightness, and incoordination may be seen. The signs of excessive oropharyngeal secretions, tearing, sweating, increased respiratory secretions, vomiting, muscle twitching, cyanosis, muscle weakness, convulsions, loss of sphincter competence, areflexia, heart block, and cardiac arrest are seen. There may be rapid progression through these signs and symptoms to death within 5-15 min. Alternatively, with lower dose exposure and, depending on degree and competence of medical support, life may be sustained for days to weeks with ultimate full recovery unless a major organ system (liver, kidney, heart, CNS) has suffered hypoxic damage. It is difficult to separate the effects of atropine from the effects of OP compound on the quantity of saliva. Furthermore, the contribution of such thick saliva to the observed respiratory obstruction has not been well evaluated. Bronchospasm secondary to OP exposures has been shown to increase pulmonary resistance and decrease dead space. A report of severe dyspnea without measurable increase in airways resistance was thought to be due to changes in chest wall mechanics. Respiratory center inhibition may be of relatively short duration.
Forensic Pathophysiology of Asphyxial Death
Sudhir K. Gupta in Forensic Pathology of Asphyxial Deaths, 2022
Medulla and pons contain the central respiratory centers that are responsible for initiating, controlling and maintaining the respiratory pattern. The medullary center consists of a dorsal and a ventral respiratory group, and the pontine center consists of a pneumotaxic center and an apneustic center together forming the pontine respiratory group. The dorsal respiratory neurons initiate the process of inspiration and the ventral group controls expiration. The pneumotaxic center and the apneustic center provide negative and positive feedback to the dorsal respiratory group, respectively, thereby regulating the discharges from this center (Figure 1.5).
Respiratory disturbances in fibromyalgia: A systematic review and meta-analysis of case control studies
Published in Expert Review of Respiratory Medicine, 2021
Araceli Ortiz-Rubio, Irene Torres-Sánchez, Irene Cabrera-Martos, Laura López-López, Janet Rodríguez-Torres, María Granados-Santiago, Marie Carmen Valenza
Respiration is a complex function involving the absolute and strict cooperation of muscular, skeletal, and nervous systems [8]. It is rarely completely regular, except in deep non-REM sleep and under anesthesia [11]. Moderate instability reflects a mechanism that is termed dynamic homeostasis. Respiratory function can be influenced by biochemical, biomechanical, and psychological factors, showing an open loop system, vulnerable to adaptations [12–14]. The increased levels of baseline respiratory instability are often associated with pathophysiology either at the level of the sensors of the regulation system (such as hypersensitivity or hyposensitivity of peripheral and central CO2 sensors or proprioceptive afferents) or at the effectors (such as stiffness in the diaphragm or intercostals or inhibited nerve transmission to them) [15]. Additionally, there is a rich network for cortical and subcortical projections to the brain stem (the respiratory center) that can likely influence movement to moment breathing [16].
Dopamine β hydroxylase as a potential drug target to combat hypertension
Published in Expert Opinion on Investigational Drugs, 2020
Sanjay Kumar Dey, Manisha Saini, Pankaj Prabhakar, Suman Kundu
The arterial baro- and chemo-reflexes are negative feedback mechanisms to maintain the beat-to-beat homeostasis in ABP [21]. Sudden change in ABP is detected by baroreceptors in the circulatory walls of the carotid sinus and aortic arch. These afferent baroreceptors then induce a sympatho-inhibitory reflex, known as baroreflex from carotid sinus and aorta using glossopharyngeal and vagus nerves, respectively, toward NTS and normalizes BP by adjusting cardiac output and vascular resistance [22–24]. In case of chronic hypertension, baroreceptors loses sensitivity and remains unable to prevent sudden variation in BP [22–24]. On the other hand, chemoreflexes are induced by the chemoreceptors which sense the changes in arterial PO2, PCO2, and pH at their distinct vassal locations in the carotid bodies and aortic bodies [18,23]. Respiratory center in the brain is stimulated by chemoreflex due to decrease in PO2 and pH or increase in PCO2, which in turn induces the sympathetic outflow. In obstructive sleep apnea patients, repeated stimulation of chemoreflex by chronic hypoxia and hypercapnia increases the chance of hypertension [21,25].
Comparison between pericapsular nerve group block and morphine infusion in reducing pain of proximal femur fracture in the emergency department: A randomized controlled study
Published in Egyptian Journal of Anaesthesia, 2023
Abdelrhman Alshawadfy, Ahmed M. Elewa, Mahmoud Ahmed Mewafy, Ahmed A. Ellilly
Baseline characteristics including age, gender, body mass index, and ASA physical status were comparable in both groups. The total morphine consumption was significantly lower in the PENG group than in the PCA group (p < 0.001). The total morphine reduction was 3.6 mg less in the PENG group than in the PCA only group. Only one patient in the PENG group required rescue analgesia, while nine patients in the PCA group needed rescue analgesia with statistically significant difference (p = 0.007). The median value of the sleeping hours was 8 hours in the PENG group compared with 7 hours in the PCA group with a statistically significant difference (p = 0.01). The PCA group developed significantly greater respiratory center depression in comparison with the PENG group (61% vs 11%, respectively; p = 0.005). The incidence of nausea was significantly lower in the PENG group than the PCA group (17% vs 56%, respectively; p < 0.05). Meanwhile, vomiting was comparable in both groups (p = 0.121) (Table 1).