ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Twenty patients requiring ventilation for acute respiratory failure were studied to determine whether intrapulmonary shunt fraction (Qs/Qt) measured at an inspired oxygen concentration (FIo2) of 1.0 differs from Qs/Qtmeasured at the clinically indicated FIo2and, if so, the mechanism by which this occurs. Qs/Qtincreased from 15.5 ± 1.8 per cent (mean ± SE) at the clinically indicated inspired oxygen fraction (FIo20.3–0.6) to 21.7 ± 2.1 per cent after 20 minutes at FIo21.0. Functional residual capacity (FRC) decreased by 6 ± 6 per cent and total compliance (CT) by 10 ± 6 per cent. Mean pulmonary arterial pressure fell from 21 ± 2 to 17 ± 2 Hg, whereas pulmonary capillary wedge pressure (PCWP) and cardiac output remained unchanged. Mixed venous oxygen tension increased from 37 ± 1 to 45 ± 2 mm Hg with 100 per cent oxygen. At 90 per cent oxygen, Qs/Qtincreased from the value at low FIo2but FRC and CTdid not change. Simultaneous application of 100 per cent oxygen and a positive end-expiratory pressure (6 cm H2O) increased FRC, CTand Qs/Qt. Patients with increased PCWP showed smaller increases in Qs/Qtwith 100 per cent oxygen. These findings suggest two mechanisms responsible for the increase in Qs/Qt: 1) redistribution of blood flow to nonventilated areas, resulting from the vasodilating effect of an increased oxygen tension in the vessels of hypoxic lung segments; 2) resorption atelectasis. Of the total change in Qs/Qtobserved during ventilation with oxygen, 63 per cent was calculated to be due to factors other than a decrease in FRC.

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The ventilatory responses to isocapnic hypoxia and hypercapnia were studied in seven chronically tracheostomized dogs awake and during anesthesia with pentobarbital (30 mg/kg, iv), ketamine, or thiopental (10 and 15 mg/kg, respectively, followed by infusion). Isocapnic hypoxic ventilatory drive (HVD) was expressed as the parameter A such that the higher the A, the greater the hypoxic drive. HVD(A) was significantly reduced from 259 ± 28 (mean ± SEM) in awake dogs, to 96 ± 14 after pentobarbital, 161 ± 27 after thiopental, and 213 ± 23 after ketamine. Hypercapnic ventilatory drive (HCVD) as measured by S (slope of the VE– PAco2response curve) was significantly reduced from 1.3 ± .32 in awake dogs to 0.4 ± .13 after pentobarbital, 0.5 ± .12 after thiopental, and 0.6 ± .11 after ketamine. In addition, hypercapnia-induced augmentation of hypoxic drive was markedly diminished by the two barbiturates but was unaffected by ketamine. Therefore, ketamine at this dose level afforded greater protection during exposure to hypoxia than did barbiturates.

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The effects of halothane, enflurane, and methoxyflurane on hypocapnic bronchoconstriction (increased airway resistance and decrea ed compliance of the lung) were studiedin cicoin the isolated left lower lobe of the canine lung. Hypocapnic bronchoconstriction, induced by altering the concentration of CO2in gas ventilating the lobe, was repeated in the presence and absence of various concentrations of anesthetic gases (halothane: 0.5, 1,0, and 3.0 per cent; enflurane: 1.0, 3.0, and 5.0 per cent; methoxyflurane: 0.25, 0.50, and 1.0 per cent). In the higher concentrations, all three drugs blocked the bronchoconstrictor effect produced when the inspired CO2was decreased from 5 to 0 per cent. In lower concentrations, halothane was the most effective blocking drug. Propranolol did not affect the ability of the three anesthetics to block hypocapnic bronchoconstriction, nor did the beta-receptor blocking drug sotalol affect the blocking effects of halothane. The ability of these anesthetics to block hypocapnic bronchoconstriction probably is mediated not through an adrenergic mechanism but by one that is nonspecific.

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The authors evaluated the efficacy of continuous positive-pressure ventilation (CPPV) and methyl-prenisolone alone and in combination as therapy for near-drowning in 80 dogs that had aspirated distilled water ml/kg or 44 ml/kg). Forty dogs were treated with mechanical ventilation for one hour and 40 for 24 hours. Blood-gas tensions, pH, cardiac output and intrapulmonary shunt (Qs/Qt) were measured frequently for 24 hours. Blood-gas tensions and pH were again measured 48 and 72 hours and seven days later in survivors. Arterial oxygen tension (Pao2) decreased and Qs/Qtincreased in all animals following aspiration and before therapy. Forty dogs received methylprednisolone intravenously (30 mg/kg) (20 breathed spontaneously and 20 had CPPV). There was a significant increase in Pao2and decrease in pulmonary shunt in dogs that were ventilated mechanically compared with animals that breathed spontaneously. Treatment with methylprednisolone made no difference in blood gases, pulmonary shunt, or survival rates. Thus, no evidence to support the use of methylprednisolone in the treatment of the pulmonary lesion of fresh-water near-drowning was found.

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The authors studied the effects of varying Na++and Ca++concentrations and of replacing H2O with D2O in Ringer's solution upon the actions of general and local anesthetics on isolated frog sciatic nerves. This experimental model was used to study whether general anesthetics affect excitable membranes in a manner similar to that of typical membrane stabilizers (local anesthetics). Procaine (2.5–7.5 mM), halothane (9, 18, and 36 mM), enflurane (8 mM), and ketamine (0.15 and 0.73 mM) raised threshold and lowered spike amplitude, and their effects were facilitated by reducing Na++concentration in the Ringer's solution. The local anesthetic effects of procaine (2.5–7.5 mM) and ketamine (0.73 mM) were antagonized by Ca++, while the axonal depressant effect of halothane was facilitated by increasing Ca++concentration in the Ringer's solution, indicating a different mode of action. General anesthetics also differed from local anesthetics in their interaction with water: replacement by D2O of H2O in the Ringer's solution selectively increased the axonal depressant effects of halothane and enflurane but not those of ketamine or procaine. Since D2O differs from H2O in its greater icelikeness, these results are consistent with the view that general anesthetics stabilize excitable membranes via stabilization of the water-biopolymer lattice, as predicted by the hydrate-microcrystal theory of anesthesia. In contrast, local anesthetics may stabilize excitable tissues by binding to the same fixed negative charges of the membrane to which Ca++is normally bound.

ISSN:0003-3022    

出版商:OVID    

年代:1975

数据来源: OVID