33 CASE 33 A 38-year-old man is transported to the emergency department after being found unconscious and in respiratory depression in his apartment. The paramedics intubate the patient and manually ventilate him with an Ambu bag. The patient is transported to the emergency department. On arrival, an arterial blood sample is obtained for blood gas analysis and for drug screen. The patient is placed on a ventilator with supplemental oxygen. PHYSICAL EXAMINATION VS: T 32.5°C, P 55/min, R 8/min, BP 80/50 mm Hg PE: Patient is in a coma and does not respond to painful stimuli. Pupils are small and reactive. Muscle tone is flaccid, and the deep tendon reflexes are depressed. There is a positive Babinski sign (toes curled outward). LABORATORY STUDIES On arrival: • Arterial blood gases: PO2 60 mm Hg, PCO2 80 mm Hg, HCO3− 26 mEq/L, pH 7.22 • Drug screen: Positive for short-acting barbiturate • Pulse oximetry: 50% saturated 15 minutes after arrival (while being ventilated with supplemental oxygen): • Arterial blood gases: PO2 195 mm Hg, PCO2 34 mm Hg, HCO3− 22 mEq/L, pH 7.48 DIAGNOSIS Barbiturate overdose PATHOPHYSIOLOGY OF KEY SYMPTOMS The primary symptoms for this patient are due to the barbiturate-induced depression of the central nervous system. The brain stem, including the respiratory centers, along with the reticular activating system, the cerebellum, and the cerebral cortex are particularly sensitive to the depressant effects of barbiturates. The rhythmic pattern of breathing is initiated in the pons and medulla of the brain stem. The dorsal respiratory neurons in the nucleus of the tractus solitarius generate a basic inspiratory respiratory rhythm. The pneumotaxic center of the pons controls the rate and the pattern of respiration. The brain stem control of breathing is modulated by ascending input from the carotid and aortic chemoreceptors, by input from the medullary chemoreceptors, and by descending input from the motor cortex, limbic system, and autonomic nervous system. Central nervous system depression diminishes or completely abolishes ventilation. Hypoventilation impairs alveolar gas exchange, resulting in an increase in carbon dioxide levels and a decrease in oxygen levels. Normally, hypercapnia and hypoxia, working through the aortic and carotid chemoreceptors, should stimulate an increase in ventilation. Because of the central nervous system depression, this homeostatic control mechanism is not functioning. Naloxone will help to block the action of opiates, which are commonly found in overdoses. There is no direct antidote to barbiturate overdose, so ventilation must be artificially maintained until the drugs are cleared from the body. Advanced trauma life support (ATLS) guidelines, created by the American College of Surgeons, recommend the standard approach to assessing trauma victims based on the acronym ABCDE: A = airway< div class='tao-gold-member'> Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Like this:Like Loading... Related Related posts: 21 39 58 71 Stay updated, free articles. Join our Telegram channel Join Tags: Problem-Based Physiology Jul 4, 2016 | Posted by admin in PHYSIOLOGY | Comments Off on 33 Full access? Get Clinical Tree
33 CASE 33 A 38-year-old man is transported to the emergency department after being found unconscious and in respiratory depression in his apartment. The paramedics intubate the patient and manually ventilate him with an Ambu bag. The patient is transported to the emergency department. On arrival, an arterial blood sample is obtained for blood gas analysis and for drug screen. The patient is placed on a ventilator with supplemental oxygen. PHYSICAL EXAMINATION VS: T 32.5°C, P 55/min, R 8/min, BP 80/50 mm Hg PE: Patient is in a coma and does not respond to painful stimuli. Pupils are small and reactive. Muscle tone is flaccid, and the deep tendon reflexes are depressed. There is a positive Babinski sign (toes curled outward). LABORATORY STUDIES On arrival: • Arterial blood gases: PO2 60 mm Hg, PCO2 80 mm Hg, HCO3− 26 mEq/L, pH 7.22 • Drug screen: Positive for short-acting barbiturate • Pulse oximetry: 50% saturated 15 minutes after arrival (while being ventilated with supplemental oxygen): • Arterial blood gases: PO2 195 mm Hg, PCO2 34 mm Hg, HCO3− 22 mEq/L, pH 7.48 DIAGNOSIS Barbiturate overdose PATHOPHYSIOLOGY OF KEY SYMPTOMS The primary symptoms for this patient are due to the barbiturate-induced depression of the central nervous system. The brain stem, including the respiratory centers, along with the reticular activating system, the cerebellum, and the cerebral cortex are particularly sensitive to the depressant effects of barbiturates. The rhythmic pattern of breathing is initiated in the pons and medulla of the brain stem. The dorsal respiratory neurons in the nucleus of the tractus solitarius generate a basic inspiratory respiratory rhythm. The pneumotaxic center of the pons controls the rate and the pattern of respiration. The brain stem control of breathing is modulated by ascending input from the carotid and aortic chemoreceptors, by input from the medullary chemoreceptors, and by descending input from the motor cortex, limbic system, and autonomic nervous system. Central nervous system depression diminishes or completely abolishes ventilation. Hypoventilation impairs alveolar gas exchange, resulting in an increase in carbon dioxide levels and a decrease in oxygen levels. Normally, hypercapnia and hypoxia, working through the aortic and carotid chemoreceptors, should stimulate an increase in ventilation. Because of the central nervous system depression, this homeostatic control mechanism is not functioning. Naloxone will help to block the action of opiates, which are commonly found in overdoses. There is no direct antidote to barbiturate overdose, so ventilation must be artificially maintained until the drugs are cleared from the body. Advanced trauma life support (ATLS) guidelines, created by the American College of Surgeons, recommend the standard approach to assessing trauma victims based on the acronym ABCDE: A = airway< div class='tao-gold-member'> Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Like this:Like Loading... Related Related posts: 21 39 58 71 Stay updated, free articles. Join our Telegram channel Join
