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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Low-flow anesthesia provides benefits of ecologic advantages, reduction of pollution of operating room, increased economy and prevention of airway dessication. It is worthy to gain popularity of application. In this review article, certain aspects of low-flow anesthesia are included: 1) how to avoid hypoxemia, 2) how to prevent carbon dioxide retention, 3) how to use Lin's method in calculating the metered concentration of inhalational anesthetics during maintenance period, 4) how the time constant to affect the time to surgical level of anesthesia, and 5) the indications of low-flow anesthesia for surgery. Finally, clinical experience in low-flow anesthesia will be discussed in terms of halothane, enflurane or isoflurane with or without nitrous oxide.
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PMID:[Low-flow anesthesia]. 175 64

Microsurgical endoscopic interventions of the larynx offer an optimal approach to the surgeon by providing an unrestricted operative field. During such operations, ventilating the patient should in no way be impaired. For this reason we have developed a new type of tubeless jet ventilation which consists of both low-frequency and superimposed high-frequency jet ventilation. In addition, we have integrated two specifically sized jets into a Kleinsasser laryngoscope, placing them at different sites. This technique guarantees adequate ventilation with an oxygen-air blend. Due to the Venturi effect, air and tidal volumes are also enhanced when passing through the external open end of the laryngoscope. This type of tubeless jet ventilation was applied to more than 60 patients, using a prototype jet. Anesthesia consisted of a continuous intravenous administration of propofol, with sufentanil and vecuronium given as needed. Clinical results revealed optimal ventilation of all patients without hypercapnia or other complications. Operative conditions for the surgeon were also very satisfactory. Findings demonstrated that this type of tubeless jet ventilation is also particularly suited for laryngeal laser surgery, thus avoiding flammable tubes and noxious anesthetics.
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PMID:Tubeless translaryngeal superimposed jet ventilation. 176 10

To determine whether the intensity of dyspnea at a given level of respiratory motor output differs between bronchoconstriction and the presence of an external resistance, we compared the sensation of difficulty in breathing during isocapnic voluntary hyperventilation in six normal subjects. An external resistance of 1.9 cmH2O.1-1.s was applied during both inspiration and expiration. To induce bronchoconstriction, histamine aerosol (5 mg/ml) was inhaled until airway resistance (Raw) increased to a level approximately equal to the subject's control Raw plus the added external resistance. To clarify the role of vagal afferents on the genesis of dyspnea during both forms of obstruction to airflow, the effect of airway anesthesia by lidocaine aerosol inhalation was also examined after histamine and during external resistive loading. The sensation of difficulty in breathing was rated at 30-s intervals on a visual analog scale during isocapnic voluntary hyperpnea, in which the subjects were asked to copy an oscilloscope volume trace obtained previously during progressive hypercapnia. Histamine inhalation significantly increased the intensity of the dyspneic sensation over the equivalent external resistive load at the same levels of ventilation and occlusion pressure during voluntary hyperpnea. Inhaled lidocaine decreased the sensation of dyspnea during bronchoconstriction with no change in Raw, but it did not significantly change the sensation during external resistive loading. These results suggest that afferent vagal activity plays a role in the genesis of dyspnea during bronchoconstriction.
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PMID:Effects of bronchoconstriction and external resistive loading on the sensation of dyspnea. 177 11

Phrenic and cervical sympathetic nerve responses to hypercapnia were examined before and after anesthesia in twelve midcollicularly decerebrated, vagotomized, glomectomized, paralyzed and ventilated cats. We measured responses of integrated phrenic and cervical sympathetic nerve activities to increases in end-tidal PCO2 (PETCO2) from apneic threshold to approximately 30 torr above threshold. All cats were studied first in the unanesthetized state. Six cats were then restudied after a quarter of a usual dose of chloralose/urethane (10 mg/kg and 62.5 mg/kg, respectively) and then after half the usual dose of chloralose/urethane (20 mg/kg and 125 mg/kg). The other six animals were restudied after quarter of a standard dose of pentobarbital (9 mg/kg), after half the standard dose (18 mg/kg) and then after the full (35 mg/kg) dose. Both anesthetic agents led to significant increases in apneic thresholds for both phrenic and sympathetic nerve activities. These agents also caused dose-dependent decreases in peak, tonic and respiratory-related sympathetic nerve activities. Peak (tidal) phrenic nerve activities, in comparison, were much less affected by the anesthetic agents. CO2 response curves showed that both of these anesthetic agents depressed, at any given level of PETCO2, respiratory-related sympathetic nerve responses more than the responses found in the phrenic nerve. We conclude that the relations between peak, tonic (i.e. between phasic bursts) and respiratory-related sympathetic nerve activities and phrenic nerve activity can be altered by anesthesia.
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PMID:Anesthesia affects respiratory and sympathetic nerve activities differentially. 178 59

Cough responses evoked by mechanical stimulation of the tracheobronchial mucosa in anesthetized and tracheostomized dogs were studied. The most common response was a group of coughs. Phase relationships between coughing and spontaneous respiration during the cough initiation and resolution periods were categorized as either synchronized or unsynchronized. We defined the synchronization as the coincidence of an expiratory thrust and the early-expiratory phase of respiration. During the cough initiation period, the incidence of synchronization increased as central respiratory activity was enhanced by hypercapnia or as the cough center's activity was suppressed by deep anesthesia. Synchronization decreased as central expiratory activity was enhanced by expiratory threshold loading. During the cough resolution period, synchronization occurred in conjunction with a gradual decrease in the cough center's activity. Coughing could be evoked when the dog was made apneic either by hyperventilation or by the Hering-Breuer reflex. In either case, apnea persisted after coughing subsided. These findings suggest that mechanical stimulation directly activates the cough center rather than the respiratory center; and that synchronization is determined by the relative strengths of the respiratory and cough center's activities.
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PMID:Influence of central respiratory activity on the cough response in anesthetized dogs. 180 71

Sufentanil, a synthetic opioid that is 5-10 times as potent as fentanyl, has been suggested for use during neurosurgical procedures because it maintains cardiovascular stability and produces hypnosis without the use of additional anesthetic agents. Doses as low as 2.5 micrograms.kg-1 are reported to create deep levels of anesthesia as demonstrated by EEG changes to high-amplitude delta-waves. However, there are no reports concerning the effects of sufentanil on blood flow and metabolism in the human brain. The present study was designed to investigate the influence of high-dose sufentanil-O2 anesthesia on the cerebral circulation, metabolism, and the cerebrovascular response to CO2 in man. METHODS. Nine male and 2 female patients between 41 and 60 years of age who were scheduled for coronary artery bypass surgery were studied. Premedication consisted of flunitrazepam 2 mg orally and piritramide 15 mg and promethazine 50 mg i.m. 1 h before arrival in the induction room. Measurements were performed with the patients awake (I), after sufentanil 10 micrograms.kg-1 as an induction dose followed by 0.15 micrograms.kg-1.min-1 as an infusion with normocapnia (pa CO2 42.1 +/- 2 mmHg) (II), during hypercapnia (pa CO2 53.7 +/- 3.5 mmHg) (III), and during hypocapnia (pa CO2 31.7 +/- 2 mmHg) (IV). Cerebral blood flow (CBF) was measured using the argon wash-in technique. Cerebral venous blood was obtained from a catheter in the superior bulb of the right internal jugular vein. Cerebral metabolic rates of oxygen (CMRO2) glucose (Mgluc) lactate (CMlac) were calculated by multiplying the arterial-cerebral venous oxygen and substrate differences by CBF. The Anaerobic Index was calculated from the equation avD lactate x 100/2 x avD glucose = ANI (%) Cerebral electrical activity was recorded by aperiodic analysis of the EEG (Lifescan). RESULTS AND DISCUSSION. In the EEG sufentanil anesthesia was characterized by a decrease in the number of high-frequency waves and an increase in the number and amplitude of delta-waves, a pattern that did not change throughout the study period. Concomitantly, under normocapnic conditions high-dose sufentanil led to the significant decrease in CBF by 29% accompanied by an 18% increase in cerebral vascular resistance (CVR). CMRO2 decreased by 22% while CMRgluc and CMRlac changed only insignificantly such that the ANI, which represents the percentage of anaerobically metabolized glucose, essentially remained unchanged. Mean perfusion pressure declined by 18% but stayed within the range of autoregulation. Hypoventilation (III) was followed by an 82% increase in CBF as a result of a 55% reduction in CVR, whereas cerebral metabolic parameters did not show important changes when compared to measurement II. Hyperventilation (IV), on the other hand, produced a distinct fall in CBF by 56% to a value that was 21% below the one obtained under normocapnia. This was due to an increase in CVR of the same magnitude. There was a 31% rise in CMRO2, resulting in a decrease in cerebral venous oxygen tension, but in no case did it fall below the critical value of 20 mmHg at which tissue hypoxia becomes severe. Although CMRlac increased and CMRgluc did not significantly change, the ANI remained essentially unchanged, which suggests a predominantly aerobic metabolism. The increase in metabolic activity with sufentanil during hypocapnia might be caused by an alkalosis-induced stimulation of glycolysis. It might also be related to a reduction in the depth of anesthesia, although neither the EEG nor the hemodynamic parameters indicated this. This study shows that the coupling between CBF and metabolism is well maintained and that the cerebrovascular response to CO2 is unimpaired during high-dose sufentanil anesthesia.
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PMID:[The effect of sufentanil on cerebral blood flow, cerebral metabolism and the CO2 reactivity of the cerebral vessels in man]. 182 62

This study was conducted to evaluate the different change in arterial blood gases and cardiovascular system in 50 healthy females during laparoscopic sterilization procedure performed under general or local anaesthesia. Women who had laparoscopic sterilization under local anaesthesia, showed an increase in respiratory rate by 17% in response to hypercarbia produced by carbon dioxide insufflation. Subjects undergoing laparoscopic sterilization under general anaesthesia showed significant rise in pulse rate by 6% and systolic and diastolic blood pressure by 8% and 14%, respectively. Also arterial blood gas analysis showed increase in PaO2 by 22.7% which was highly significant. However, PaCO2, pH and base were maintained within normal limits as compared to the other group done under local anaesthesia, where no changes were observed.
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PMID:Studies of cardiovascular and arterial blood gas changes during carbon dioxide pneumoperitoneum for laparoscopic sterilization under general anaesthesia versus local anaesthesia. 182 6

Blood gas changes after laparoscopy under general anesthesia were examined. Thirty-six ASA I or II women were allocated to one of the two groups: carbon dioxide was used for pneumoperitoneum in group C and nitrous oxide in group N. Anesthesia was maintained with enflurane, buprenorphine, and supplemental midazolam. Arterial blood gases were measured in patients breathing room air. A significant fall in PaO2 (from 92.8 mmHg to 71.5 mmHg) was observed 5 minutes after extubation in group N as compared with the preoperative level and with group C, but there is no change in PaO2 in group C. PaCO2 showed no significant changes in both groups. In 6 out of 36 patients, PaO2 decreased below 60 mmHg. Possible causes of the difference between the two groups are diffusion hypoxia produced by nitrous oxide, gas embolism, or postoperative hyperventilation in response to hypercarbia during laparoscopy by carbon dioxide insufflation, and the last one is most probable. This may have prevented hypoxia in group C.
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PMID:[Blood gas changes after laparoscopy]. 183 21

Single lung transplantation was performed in several steps: laparotomy to prepare an omentopexy, followed by pneumonectomy and implantation of a pulmonary graft, both by postero-lateral thoracotomy. The patients suffered from lymphangiomyomatosis (1), panacinar emphysema (2) and idiopathic pulmonary fibrosis (1). Immunosuppressive treatment was started before surgery. Anaesthesia was induced and maintained with alfentanil, midazolam and vecuronium. The patients were intubated with a Carlens endotracheal tube. Ventilation was carried out using an oxygen-air mixture, without any nitrous oxide or halogenated anaesthetic agent. Besides the usual parameters, expired CO2 concentrations, and oxygen saturation in the pulmonary artery were monitored. Partial femoro-femoral cardiopulmonary bypass was not required. Three major problems were encountered: hypoxia, hypercapnia, and pulmonary arterial hypertension. Hypoxia first occurred during the period of one-lung ventilation, during pneumonectomy, and again after unclamping of the graft vessels before the bronchus had been anastomosed. It was treated either by increasing the FiO2, inflating the lungs with pure oxygen, or partial clamping of the homolateral pulmonary artery. Hypercapnia occurred in three of the four patients until the graft was ventilated again. Except in one patient with preoperative pulmonary hypertension, the increase in pulmonary vascular resistances remained moderate after clamping of the pulmonary artery. Sufficient oxygen delivery, with more than 50% venous oxygen saturation, was maintained at this time by the infusion of dopamine and dobutamine. Two other specific problems were encountered in the emphysematous patients: severe hypotension following the start of artificial ventilation and after placing the patient in lateral position; thoracic asymetry with overdistension of the emphysematous lung, and mediastinal shift.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Anesthesia in unilateral pulmonary transplantation]. 185 49

We present herein clinical experience of neurosurgical anesthesia and cerebral protection in 66 cases, including 27 with supratentorial mass, 28 posterior fossa tumor and 11 cerebral vascular deformity. Our methods for the control of intracranial pressure (ICP) and cerebral blood flow (CBF) during neurosurgical anesthesia were as follows: (1) avoidance of the drugs adversely influenced on ICP; (2) use of lidocaine iv. infusion; (3) prevention of hypercapnia; (4) maintenance of adequate perfusion of vital organs; (5) drainage of cerebrospinal fluid if necessary; (6) use of free radical clearing agents. We conclude that they are key points of effective control of ICP and maintenance of CBF so as to prevent cerebral ischemic effect on neurological function.
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PMID:[Cerebral protection in neurosurgical anesthesia]. 187 98


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