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K Rehder

Publications and source records attributed to K Rehder.

At least 19 recordsLinked to original sources
PubMed1995

Comparison of the pharmacodynamics of ketamine in the isolated neonatal and adult porcine airway.

Ketamine inhibits contractions of adult airway smooth muscle by actions both within the smooth muscle cell and the vagal intramural ganglia. Its effects in the neonate are unknown, as physiological changes occur after birth in both of these structures. Isolated trachealis muscle strips from neonatal and adult pigs were contracted selectively by stimulation of the vagal intramural ganglia using dimethyl-phenyl-piperazinium (DMPP), the post-ganglionic vagus nerve using electrical field stimulation (EFS) and the smooth muscle cell itself using acetylcholine (ACh) in the presence of tetrodotoxin. The inhibitory effects of clinical concentrations of ketamine at each site were compared both within and between age groups. At both ages, ketamine 10(-4) mol litre-1 abolished (P < or = 0.001) and ketamine 10(-5) mol litre-1 attenuated (P < or = 0.001) the contractile responses to DMPP at the intramural ganglia. The inhibitory effect of ketamine 10(-4) mol litre-1 on ACh responses at the smooth muscle cell was greater in neonatal preparations (P = 0.025). Furthermore, only neonatal EFS and ACh responses were attenuated by ketamine 10(-5) mol litre-1 (P = 0.04 and P = 0.03). Ketamine 10(-4) mol litre-1 attenuated EFS responses in both age groups (P < or = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1995

Opioid agonists modulate release of neurotransmitters in bovine trachealis muscle.

BACKGROUND: Stimulation of opioid receptors in the airways can modulate cholinergic neurotransmission and thereby reduce bronchoconstriction. This protecting effect of opioids against bronchoconstriction may be of clinical interest. Inhalation of opioids as a method of analgesia is likely to result in an opioid concentration at airway receptors sufficient to protect against bronchoconstriction; the concentration may be insufficient when opioids are administered by conventional techniques. In addition, new selective opioids may be developed that could more selectively protect the airways against bronchoconstriction. METHODS: The effect of three selective opioid agonists on the contractile response to electric field stimulation (EFS) was studied in isolated muscle strips from four regions of the bovine trachea (upper, or laryngeal; upper middle; lower middle; lower, or carinal). RESULTS: The selective kappa agonist trans-3,4-dichloro-N-methyl-N-(2-1-pyrrolidinyl) cyclohexyl benzene acetamide (U-50488 H) and the selective mu-opioid agonist D-Ala2-N-MePhe4-Gly-ol5-enkephalin (DAMGO) reduced significantly (P < 0.001 and P < 0.001, respectively) the contractile response to EFS. The attenuation of the contractile response by U-50488 H was concentration-dependent (P < 0.0001) and tended to be larger at low stimulating frequencies (P = 0.055). The attenuation of the contractile response by DAMGO was frequency-dependent (P < 0.01). The selective delta-opioid agonist D-penicillamine2-D-penicillamine5-enkephalin had no significant effect on the contractile response to EFS (P = 0.71). There were no significant differences among the four regions of the trachea in their responses to the selective opioid agonists U-50488 H (P = 0.50) and DAMGO (P = 0.44). Neither U-50488 H nor DAMGO altered the contractile response to acetylcholine P > 0.11, P > 0.21, respectively), suggesting that the opioid agonists have a prejunctional effect. The attenuation of the contractile response to EFS by U-50488 H was partially but significantly antagonized by 10(-5) M naloxone (P < 0.01) and by 10(-5) and 10(-6) M of the selective kappa-opioid antagonist 2,2'-[1,1'-biphenyl] 4,4'-diyl- bis [2-hydroxy-4,4-dimethyl-morpholinium] (P < 0.05). Naloxone (10(-5) M) abolished the inhibitory effect of DAMGO, suggesting that opioid receptors are involved in the attenuation of the contractile response to EFS afforded by DAMGO and U-50488 H. CONCLUSIONS: We conclude that prejunctional kappa- and mu-opioid receptors attenuate the contractile response of isolated bovine trachealis muscle to EFS by inhibiting cholinergic neurotransmission. This effect is uniform throughout the trachealis muscle. delta-Opioid receptors are apparently not present in the bovine trachealis muscle. Caution must be used in extrapolating these results to the intact human. In this study little or no inhibitory effect of the opioids was observed at concentrations expected at airway receptor sites when administered by conventional techniques. However, the effect may be large enough to protect against bronchoconstriction when nebulized opioids are administered by inhalation.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1993

Mechanisms of the relaxant action of ketamine on isolated porcine trachealis muscle.

Ketamine is a potent bronchodilator, but its mode of action is unclear. We have studied the effect of ketamine on the peripheral vagus nerve motor pathway of isolated porcine trachealis muscle. Postsynaptic nicotinic cholinergic receptors of the intramural ganglia were stimulated selectively with 1,1-dimethyl-4-phenyl-piperazinium iodide, post-ganglionic nerve fibres with electrical field stimulation (in the presence of hexamethonium) and muscarinic cholinergic receptors with acetylcholine (in the presence of tetrodotoxin). Ketamine 10(-4) mol litre-1 significantly shifted the concentration-response curves of acetylcholine (P < 0.02) and electrical field stimulation (P < 0.001) to the right and abolished the response to 1,1-dimethyl-4-phenyl-piperazinium iodide (P < 0.02). Ketamine also caused a concentration-dependent relaxation of muscle strips precontracted with acetylcholine. This was unaffected by propranolol. Ketamine relaxed muscle strips precontracted with potassium chloride, in the absence and presence of atropine. We conclude that ketamine interacts with the peripheral vagus nerve by decreasing the excitability of the postsynaptic nicotinic receptors of the intramural ganglia, and by affecting the muscarinic receptor, smooth muscle, or both. Beta-2 adrenoceptors are not involved in the mechanism of relaxation.

Acetylcholine↗
PubMed1993

Factors influencing the direct actions of volatile anesthetics on airway smooth muscle.

BACKGROUND: The authors hypothesized that the ability of volatile anesthetics to relax airway smooth muscle (AWSM) depends on: 1) the agonist used to produce muscle contraction, 2) the preexisting level of contraction, and 3) the volatile anesthetic used. METHODS: To test the first hypothesis, isolated strips of canine trachealis muscle were precontracted with acetylcholine (ACh), McN-A-343 (McN, another muscarinic agonist), 5-hydroxytryptamine (5HT, a different receptor agonist), or potassium chloride (KCl, which induces contraction by cell depolarization) to 50% of maximal force, then exposed to halothane (0.2-1.6 MAC). To test the second and third hypotheses, other strips were precontracted to 25, 50, 75, and 100% of maximal force with ACh, or to 10, 30, or 50% of maximal force with KCl, and were then exposed to halothane or isoflurane (0.2-1.6 MAC). RESULTS: For AWSM contracted to 50% of maximal force, the amount of relaxation produced by halothane depended on the agonist used to elicit contraction in the following manner: 5HT = McN > ACh; the muscles contracted with KCL did not relax. For ACh-induced contractions, the absolute amount of relaxation produced by halothane did not depend on the level of precontraction. In muscles contracted with KCl, the volatile anesthetics caused significant relaxation only in muscles contracted to 10% of maximal force. Overall, halothane had a significantly greater relaxing effect as compared with isoflurane during ACh-mediated contractions; the effects of the two agents did not differ significantly during KCl-mediated contractions. CONCLUSIONS: When canine AWSM tone is increased by contractile agonists in vitro, the absolute amount of relaxation produced by halothane depends on the agonist used to elicit contraction, but not the degree of precontraction. In addition, there are small but significant differences between the effects of halothane and isoflurane on ACh-mediated contractions.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1992

Halothane alters the response of isolated airway smooth muscle to carbon dioxide.

Rings of canine bronchi were studied in vitro to determine the effects of halothane on the responses of airway smooth muscle to hypercapnia and hypocapnia. Bronchi were first contracted to 50% of maximal active force with acetylcholine (ACh), 5-hydroxytryptamine (5HT), potassium chloride (KCl), or the muscarinic agonist McN-A-343 (McN). The CO2 concentration of the bathing solution was then changed from 6% to either 1% (hypocapnia) or 10% (hypercapnia). In the absence of halothane, changes in CO2 concentration had no significant effect on muscles contracted with ACh. With all other contractile agonists, increasing the CO2 concentration caused bronchial relaxation, while decreasing the CO2 concentration caused contraction. In the presence of 2 MAC halothane, hypocapnia relaxed bronchi contracted with the muscarinic agonists ACh or McN; the responses to hypocapnia of bronchi contracted with KCl and 5HT were not significantly changed by halothane. Halothane had no effect on the responses of the bronchi to hypercapnia. We conclude that airway smooth muscle contracted with cholinergic agonist relaxes in response to hypocapnia when exposed to 2 MAC halothane; this mechanism may contribute to the depression of hypocapnic bronchoconstriction caused by halothane in vivo.

Animals↗
PubMed1992

Cemented versus noncemented total hip arthroplasty--embolism, hemodynamics, and intrapulmonary shunting.

Bone cement implantation syndrome is characterized by hypotension, hypoxemia, cardiac arrhythmias, cardiac arrest, or any combination of these complications. It may result from venous embolization that occurs in conjunction with intramedullary hypertension in the femur during insertion of the prosthesis in patients undergoing cemented total hip arthroplasty (THA). Intramedullary hypertension does not occur in patients undergoing noncemented THA. In this study, we sought to compare embolization between patients undergoing cemented and noncemented THA and to determine whether this state resulted in cardiorespiratory deterioration. In this prospective investigation of 35 patients undergoing elective THA, we used transesophageal echocardiography and invasive hemodynamic monitoring, and in 12 of them, we monitored distribution of pulmonary ventilation and perfusion intraoperatively. Embolization was significantly greater after insertion of the prosthesis in patients undergoing cemented than in those undergoing noncemented THA. Cemented THA was also associated with decreased cardiac output and increased pulmonary artery pressure and pulmonary vascular resistance. Increases in ventilation-perfusion mismatching, however, could not be demonstrated 30 minutes after insertion of the femoral prosthesis. Intraoperative monitoring for embolism may help physicians assess patients in whom cardiorespiratory function deteriorates during THA.

Aged↗
PubMed1992

Multicenter study of general anesthesia. III. Predictors of severe perioperative adverse outcomes.

Little information is available about the incidence of severe adverse outcomes, and even less information is available about the identification and quantification of independent predictors of severe perioperative adverse outcomes. The purpose of this study was to identify and quantitate independent predictors of severe perioperative adverse outcomes in a prospective randomized clinical trial of general anesthesia in 17,201 patients. Twenty-nine prognostic variables for 15 severe outcomes in 847 patients were tested by multiple stepwise logistic regressions from which 20 significant (P less than 0.05) predictors were identified. A history of cardiac failure or myocardial infarction less than or equal to 1 yr; ASA physical status 3 or 4; age greater than 50 yr; cardiovascular, thoracic, abdominal or neurologic surgery; and the study anesthetics were significant predictors of "any severe outcome, including death." There were 17 significant predictors for 10 severe cardiovascular outcomes in 608 patients, including a history of ventricular arrhythmia, hypertension, cardiac failure, myocardial ischemia, myocardial infarction less than or equal to 1 yr or myocardial infarction greater than 1 yr, and smoking; ASA physical status; age; cardiovascular, thoracic, abdominal, eyes-ears-nose-throat/endocrine, neurologic, musculoskeletal, or gynecologic surgery; and the study anesthetics. There were 9 significant predictors for 4 severe respiratory outcomes in 163 patients, including a history of cardiac failure, myocardial ischemia, or chronic obstructive pulmonary disease; obesity; smoking; male gender; ASA physical status; abdominal surgery; and the study anesthetics. Colinearity between related prognostic variables (such as disease and ASA physical status) was assessed using progressively segregated groups of variables in eight stepwise logistic regressions. We conclude that the comprehensive stepwise logistic regression of 29 prognostic variables reported here provides a valid estimate of the risks of severe perioperative outcomes associated with general anesthesia.

Anesthesia, General↗
PubMed1992

Halothane changes the relationships between lung resistances and lung volume.

The authors hypothesized that relaxation of airway smooth muscle by halothane lessens the dependence of airway resistance on lung volume, and that halothane alters the relationship between pulmonary resistance and lung volume by changing both the airway and tissue components of pulmonary resistance. The relationship among airway resistance, tissue resistance, and lung volume was examined in mongrel dogs before and during the administration of halothane, both in airways with reduced smooth muscle tone (after vagotomy) and during moderate increases in smooth muscle tone caused by vagus nerve stimulation (VNS). Resistance were measured at several levels of positive end-expiratory pressure (PEEP, 4-15 cmH2O) using an alveolar capsule technique. Before halothane administration, airway resistance increased at low PEEP; VNS accentuated this increase. Tissue resistance increased at low PEEP only during VNS. Halothane had no significant effect on any resistance before VNS. During VNS, halothane markedly blunted increases in airway resistance and tissue resistance as PEEP decreased. The authors conclude that during stimulation of airway smooth muscle in dogs, halothane attenuates increases in airway resistance and tissue resistance with reductions in lung volume in dogs. Thus, moderate changes in lung volume have little effect on these resistances during halothane anesthesia under these conditions.

Airway Resistance↗
PubMed1992

Electrical activation of expiratory muscles increases with time in pentobarbital-anesthetized dogs.

Although the pentobarbital-anesthetized dog is often used as a model in studies of respiratory muscle activity during spontaneous breathing, there is no information regarding the stability of the pattern of breathing of this model over time. The electromyograms of several inspiratory and expiratory muscle groups were measured in six dogs over a 4-h period by use of chronically implanted electrodes. Anesthesia was induced with pentobarbital sodium (25 mg/kg iv), with supplemental doses to maintain constant plasma pentobarbital concentrations. Phasic electrical activity increased over time in the triangularis sterni, transversus abdominis, and external oblique muscles (expiratory muscles). The electrical activity of the costal diaphragm, crural diaphragm, and parasternal intercostal muscles (inspiratory muscles) was unchanged. These changes in electrical activity occurred despite stable plasma levels of pentobarbital and arterial PCO2. They were associated with changes in chest wall motion and an increased tidal volume with unchanged breathing frequency. We conclude that expiratory muscle groups are selectively activated with time in pentobarbital-anesthetized dogs lying supine. Therefore the duration of anesthesia is an important variable in studies using this model.

Anesthesia↗
PubMed1992

Gas exchange in dogs in the prone and supine positions.

To determine the cause of the difference in gas exchange between the prone and supine postures in dogs, gas exchange was assessed by the multiple inert gas elimination technique (MIGET) and distribution of pulmonary blood flow was determined using radioactively labeled microspheres in seven anesthetized paralyzed dogs. Each animal was studied in the prone and supine positions in random order while tidal volume and respiratory frequency were kept constant with mechanical ventilation. Mean arterial PO2 was significantly lower (P less than 0.01) in the supine [96 +/- 10 (SD) Torr] than in the prone (107 +/- 6 Torr) position, whereas arterial PCO2 was constant (38 Torr). The distribution of blood flow (Q) vs. ventilation-to-perfusion ratio obtained from MIGET was significantly wider (P less than 0.01) in the supine [ln SD(Q) = 0.75 +/- 0.26] than in the prone position [ln SD (Q) = 0.34 +/- 0.05]. Right-to-left pulmonary shunting was not significantly altered. The distribution of microspheres was more heterogeneous in the supine than in the prone position. The larger heterogeneity was due in part to dorsal-to-ventral gradients in Q in the supine position that were not present in the prone position (P less than 0.01). The decreased efficiency of oxygenation in the supine posture is caused by an increased ventilation-to-perfusion mismatch that accompanies an increase in the heterogeneity of Q distribution.

Animals↗
PubMed1991

Halothane, enflurane, and isoflurane depress the peripheral vagal motor pathway in isolated canine tracheal smooth muscle.

Volatile anesthetics are potent bronchodilators, but the site of action for the dilation is unclear. To determine the site of action of halothane, enflurane, and isoflurane on the peripheral vagal motor pathway, isolated strips of canine trachealis muscle were stimulated before and during exposure to halothane at 0.3, 1.0, 1.7, or 2.4 MAC, enflurane at 1 MAC, or isoflurane at 1 MAC. The sites and methods of stimulation were: 1) postsynaptic nicotinic cholinergic receptors in the intramural parasympathetic ganglia, with 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP); 2) postganglionic cholinergic nerve fibers, with electrical field stimulation (EFS); and 3) muscarinic cholinergic receptors of the smooth muscle, with acetylcholine (ACh). The concentration-response curve to DMPP was significantly shifted to the right by 0.3 MAC halothane, whereas 0.3 MAC halothane had no significant effect on the concentration-response curves to ACh and EFS. At concentrations greater than 1 MAC of halothane, enflurane, or isoflurane, concentration-response curves to all three stimuli were shifted significantly to the right; i.e., the contractile responses to ACh, EFS, and DMPP were reduced. At all concentrations of halothane the force of contraction was significantly more reduced during stimulation with DMPP than during stimulation with ACh, and at halothane concentrations greater than or equal to 1.7 MAC the response to EFS was significantly more reduced than that to ACh. We conclude that halothane, enflurane, and isoflurane attenuated airway constriction by several mechanisms, including 1) reduced excitability of the postsynaptic nicotinic receptors of the intramural parasympathetic ganglia and 2) an effect on the smooth muscle and/or on the muscarinic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Bronchodilation by halothane is not modulated by airway epithelium.

Halothane relaxes airway smooth muscles. To test the hypothesis that this relaxation is modulated by airway epithelium, we studied the effects of halothane on isolated second- and third-order canine bronchial rings and second-order canine bronchial segments. Paired rings or segments were examined, with the epithelium removed from one ring or segment of each pair. The bronchial rings were suspended in organ chambers and contracted with 10(-8)-10(-3) M acetylcholine (ACh), 10(-8)-10(-5) M 5-hydroxytryptamine (5HT), or 0.5-16 Hz electrical field stimulation (EFS, 15 V, 0.5-ms pulse duration). The tissue was contracted in the absence of halothane and during exposure to 1 and 2 MAC halothane. The bronchial segments were perfused intraluminally with physiologic salt solution (PSS) and contracted with 10(-6) M carbachol added to the tissue-bath PSS. One or 2 MAC halothane was then added to the perfusate. In the absence of halothane, epithelium removal increased the sensitivity of the bronchial rings to ACh and 5HT but not to EFS. Addition of 1 or 2 MAC halothane to the bathing fluid of the rings with or without epithelium decreased the sensitivity of the rings to ACh and 5HT. One MAC halothane decreased the sensitivity of the rings with and without epithelium to EFS. The decrease in sensitivity caused by halothane was not significantly different in rings with or without epithelium for any method of stimulation. In the bronchial segments, relaxations evoked by 1 or 2 MAC were not different in segments with or without epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1991

Chest wall motion during epidural anesthesia in dogs.

To determine the relative contribution of rib cage and abdominal muscles to expiratory muscle activity during quiet breathing, we used lumbar epidural anesthesia in six pentobarbital sodium-anesthetized dogs lying supine to paralyze the abdominal muscles while leaving rib cage muscle motor function substantially intact. A high-speed X-ray scanner (Dynamic Spatial Reconstructor) provided three-dimensional images of the thorax. The contribution of expiratory muscle activity to tidal breathing was assessed by a comparison of chest wall configuration during relaxed apnea with that at end expiration. We found that expiratory muscle activity was responsible for approximately half of the changes in thoracic volume during inspiration. Paralysis of the abdominal muscles had little effect on the pattern of breathing, including the contribution of expiratory muscle activity to tidal breathing, in most dogs. We conclude that, although there is consistent phasic expiratory electrical activity in both the rib cage and the abdominal muscles of pentobarbital-anesthetized dogs lying supine, the muscles of the rib cage are mechanically the most important expiratory muscles during quiet breathing.

Anesthesia, Epidural↗
PubMed1991

The snRNP E protein multigene family contains five pseudogenes with common mutations.

Sequence data from three previously-uncharacterized members of the snRNP E protein multigene family suggest that each is a non-transcribed processed pseudogene, even though one clone has the potential to code for a full-length protein with greater than 90% similarity to previously-characterized E protein cDNAs. Each of the newly-analyzed family members is without introns, contains a tract of polyadenylic acid residues, and is flanked by short direct repeats. In addition, the three sequences all contain point mutations that distinguish them from the E protein coding sequence. Seven point mutations are common to the three sequences described here and to two previously-described E protein pseudogenes. Although all of these mutations are transitions, only 5 of 7 could have been generated by deamination of methylated cytosines in inactive genes. Thus, the common mutations in the pseudogenes suggest an origin other than the expressed gene that we have described. Allelic variants for two of the pseudogenes were detected and repetitive elements are located near four of the five E protein pseudogenes that have been characterized.

Amino Acid Sequence↗
PubMed1990

Multicenter study of general anesthesia. I. Design and patient demography.

A prospective randomized clinical trial of enflurane, fentanyl, halothane, and isoflurane is described. The 17,201 patients were stratified into two groups (preanesthetic medication and no preanesthetic medication) and were randomized to one of four study agents: enflurane, fentanyl, halothane, and isoflurane. Fifteen university-affiliated hospitals in the United States and Canada participated. All patients were first assessed preoperatively. Data were collected during anesthesia, in the immediate recovery period, and for up to 7 days after anesthesia/surgery. The mean age of the patients was 43 yr, the mean height 167 cm, and the mean weight 68 kg. Sixty-five percent of patients were female. In this study 90.7% of patients were classified as ASA Physical Status 1 or 2, and 34.7% of patients smoked. It is concluded that pooling of data across institutions was valid and does allow determination of the efficacy and relative safety of the four study agents.

Adult↗
PubMed1990

Multicenter study of general anesthesia. II. Results.

A prospective, stratified, randomized clinical trial of the safety and efficacy of four general anesthetic agents (enflurane, fentanyl, halothane, and isoflurane) was conducted in 17,201 patients (study population). Patients were studied before, during, and after anesthesia for up to 7 days. Nineteen patients died (0.11%), and in seven of these (0.04%) the anesthetic may have been a contributing factor. The rates of death, myocardial infarction, and stroke in the study population were so low (less than 0.15%) that no conclusions regarding the relative rates of these outcomes among the four anesthetic agents could be reached. The rates of 16 of 66 types of adverse outcomes in the study population were significantly different among the four study agents. Most of these outcomes were minor. However, severe ventricular arrhythmia (P less than 10(-6)) was more common with halothane, severe hypertension (P less than 10(-6)) and severe bronchospasm (P = 0.028) were more common with fentanyl, and severe tachycardia (P = 0.001) was more common with isoflurane. Recovery from anesthesia during the first 30 min was slowest in those patients who received halothane (P less than or equal to 0.001). In addition, patients who received fentanyl experienced less pain during the first hour in the recovery room (P less than 10(-6)). In conclusion, clinically important differences do exist for some outcomes among the four study agents.

Adult↗
PubMed1990

Direct and neurally mediated effects of halothane on pulmonary resistance in vivo.

It has been suggested that halothane inhibits contraction of airway smooth muscle in vivo mainly by reducing reflex activity in nerves innervating the muscle with only minimal direct effects on the muscle itself. To examine possible mechanisms of action of halothane at clinically relevant concentrations the authors studied the effect of halothane on increases in pulmonary resistance (RL) produced by either vagus nerve stimulation (VNS, which caused neurally mediated constriction) or the inhalation of nebulized acetylcholine (ACh, which directly stimulated the smooth muscle cell) in nine mongrel dogs. The frequency of bilateral VNS and the dose of nebulized ACh were adjusted to produce approximately equal increases in RL. Halothane reduced the response to both types of stimulation in a dose-dependent fashion. At halothane concentrations greater than or equal to 0.4 MAC, the VNS response was significantly less than the ACh response. When tetrodotoxin was given to block neural activity, the ACh response was unchanged, confirming that neural activation did not contribute significantly to smooth muscle contraction in response to ACh. The authors conclude that in addition to neurally mediated effects, halothane at clinically used concentrations has significant direct effects on airway smooth muscle stimulated by ACh. The relative importance of each factor in vivo should depend on the stimulus that causes contraction of airway smooth muscle.

Acetylcholine↗