bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Alkyl Chain Dependence of the Effect of Normal Alcohols on Agonist-induced Nicotinic Acetylcholine Receptor Desensitization Kinetics
Authors: Raines Douglas E. , Zachariah Vinu T. 
Published: November 2003

Background
The nAcChoR is the prototypical member of a superfamily of ligand-gated ion channels that are all relevant targets of anesthetics and undergo desensitization upon prolonged exposure to agonist. This study was designed to investigate the effects of representative normal alcohols on the apparent rate of acetylcholine-induced nAcChoR desensitization.

Methods
Nicotinic acetylcholine receptors were obtained from the electroplax organ of Torpedo nobiliana. The apparent rate of acetylcholine-induced desensitization in the presence and absence of normal alcohols was measured using stopped-flow fluorescence.

Results
Normal alcohols as long as octanol (the longest studied) increased the apparent rate of desensitization induced by low concentrations of acetylcholine, shifting the agonist concentration-response curve for desensitization to the left Ethanol butanol, and, to a lesser extent, hexanol increased the maximal rate of desensitization induced by high, saturating concentrations of agonist. Beyond hexanol, heptanol and octanol had no effect on this maximal apparent rate of desensitization, even at concentrations that approach those that directly induce desensitization in the absence of agonist.

Conclusion
Normal alcohols ranging from ethanol to octanol increase the apparent affinity of nAcChoR for agonist with potencies that are proportional to their hydrophobicities. However, normal alcohol effects on the rate constant for desensitization show a cutoff beyond hexanoL This suggests that the effects of normal alcohols on the apparent agonist affinity and rate constant for desensitization of nAcChoR may be modulated by distinct sites that have different steric constraints; the site(s) responsible for increasing the maximal rate of desensitization are predicted to be smaller than those that increase the apparent agonist affinity.
The Effect of Prophylactic ε-Aminocaproic Acid on Bleeding, Transfusions, Platelet Function, and Fibrinolysis during Coronary Artery Bypass Grafting
Authors: Troianos Christopher A. , Sypula Richard W. , Lucas Donna M. , D'Amico Frank , Mathie Thomas B. , Desai Manish , Pasqual Roberta T. , Pellegrini Ronald V. , Newfeld Mark L. 
Published: November 2003

Background
Antifibrinolytic medications administered before skin incision decrease bleeding after cardiac surgery. Numerous case reports indicate thrombus formation with administration of epsilon-aminocaproic acid (epsilon-ACA). The purpose of this study was to examine the efficacy of epsilon-ACA administered after heparinization but before cardiopulmonary bypass in reducing bleeding and transfusion requirements after primary coronary artery bypass surgery.

Methods
Seventy-four adult patients undergoing primary coronary artery bypass surgery were randomized to receive 125 mg/kg epsilon-ACA followed by an infusion of 12.5 mg x kg(-1) x h(-1) or an equivalent volume of saline. Coagulation studies, thromboelastography, and platelet aggregation tests were performed preoperatively, after bypass, and on the first postoperative day. Mediastinal drainage was recorded during the 24 h after surgery. Homologous blood transfusion triggers were predefined and transfusion amounts were recorded.

Results
One patient was excluded for surgical bleeding and five patients were excluded for transfusion against predefined criteria One patient died from a dysrhythmia 2 h postoperatively. Among the remaining 67, the epsilon-ACA group had less mediastinal blood loss during the 24 h after surgery, 529+/-241 ml versus 691+/-286 ml (mean +/- SD), P < 0.05, despite longer cardiopulmonary bypass times and lower platelet counts, P < 0.05. Platelet aggregation was reduced in both groups following cardiopulmonary bypass but did not differ between groups. Homologous blood transfusion was similar between both groups.

Conclusions
Prophylactic administration of epsilon-ACA after heparinization but before cardiopulmonary bypass is of minimal benefit for reducing blood loss postoperatively in patients undergoing primary coronary artery bypass grafting.
Effect of Combined Spinal-Epidural Ambulatory Labor Analgesia on Balance
Authors: Pickering Anthony E. , Parry Martin G. , Ousta Basil , Fernando Roshan 
Published: November 2003

Background
Low-dose combined spinal-epidural analgesia in labor has proved popular with women because lower-limb motor power is preserved, allowing ambulation. However, there has been debate about the safety of allowing women to walk following low-dose regional analgesia because of somatosensory impairment. The authors undertook a prospective controlled observational study using computerized dynamic posturography to examine balance function in pregnant women after combined spinal-epidural analgesia.

Methods
The authors performed posturographic testing on 44 women in labor after institution of regional analgesia and compared them with a control group of 44 pregnant women. A separate group of six women were tested both before and after combined spinal-epidural analgesia.

Results
Neurologic examination after regional analgesia showed two parturients (4%) to have motor weakness (excluded from posturography). Four women (9%) had clinical dorsal column sensory loss; these women all completed posturography. The spinal-epidural analgesia group showed a small, statistically significant reduction in one of six posturographic sensory-organization tests; however, this difference was functionally minor. There were no other differences in posturography between the control and spinal-epidural groups. Similar results were found in the paired study, in which there was minimal change in balance function after spinal-epidural analgesia.

Conclusions
This is the first study to objectively examine the effect of spinal-epidural analgesia on balance function. Using computerized dynamic posturography, the authors were unable to find any functional impairment of balance function after spinal-epidural ambulatory analgesia in women in labor who had no clinical evidence of motor block.
Suppression of Central Nervous System Sodium Channels by Propofol
Authors: Rehberg Benno , Duch Daniel S. 
Published: November 2003

Background
Previous studies have provided evidence that clinical levels of propofol alter the functions of voltage-dependent sodium channels, thereby inhibiting synaptic release of glutamate. However, most of these experiments were conducted in the presence of sodium-channel activators, which alter channel inactivation. This study electrophysiologically characterized the interactions of propofol with unmodified sodium channels.

Methods
Sodium currents were measured using whole-cell patch-clamp recordings of rat brain IIa sodium channels expressed in a stably transfected Chinese hamster ovary cell line. Standard electrophysiologic protocols were used to record sodium currents in the presence or absence of externally applied propofol.

Results
Propofol, at concentrations achieved clinically in the brain, significantly altered sodium channel currents by two mechanisms: a voltage-independent block of peak currents and a concentration-dependent shift in steady-state inactivation to hyperpolarized potentials, leading to a voltage dependence of current suppression. The two effects combined to give an apparent concentration yielding a half-maximal inhibitory effect of 10 microM near the threshold potential of action potential firing (about -60 mV). Propofol inhibition was also use-dependent, causing a further block of sodium currents at these anesthetic concentrations.

Conclusions
In these experiments with pharmacologically unaltered sodium channels, propofol inhibition of currents occurred at concentrations about eight-fold above clinical plasma levels and thus at brain concentrations reached during clinical anesthesia. Therefore, the results indicate a possible role for sodium-channel suppression in propofol anesthesia.
Sevoflurane and Isoflurane Protect the Reperfused Guinea Pig Heart by Reducing Postischemic Adhesion of Polymorphonuclear Neutrophils
Authors: Heindl Bernhard , Reichle Florian M. , Zahler Stefan , Conzen Peter F. , Becker Bernhard F. 
Published: November 2003

Background
Polymorphonuclear neutrophils (PMNs) contribute to reperfusion injury. Because volatile anesthetics can reduce PMN adhesion in the reperfused, nonworking heart, the authors analyzed whether this action of volatile anesthetics affects cardiac performance after ischemia and reperfusion and further clarified the underlying mechanism.

Methods
Isolated guinea pig hearts perfused with crystalloid buffer and performing pressure-volume work were used. Hearts were subjected to 15 min global ischemia and 20 min reperfusion. In the intervention groups an intracoronary bolus of 3 x 10(6) PMNs was applied in the second min of reperfusion, either in the absence or presence of 0.5 or 1 minimum alveolar concentration sevoflurane or isoflurane. The number of sequestered PMNs was calculated from the difference between coronary input and output (coronary effluent) of PMNs. Performance of external heart work, determined pre- and postischemically, served as criterion for recovery of myocardial function. Additionally, the expression of the integrin CD11b on the cell surface of PMN was measured before and after coronary passage.

Results
Injection of PMN in the reperfusion phase, but not under nonischemic conditions, reduced recovery of external heart work significantly (from 55+/-7% to 19+/-11%). Addition of sevoflurane or isoflurane in concentrations of 0.5 and 1 minimum alveolar concentration to the perfusate reduced postischemic PMN adhesion from 36+/-8% to basal values (20+/-7%) and prevented decline of cardiac function. CD11b expression on PMNs increased significantly during postischemic coronary passage under control conditions. Again, both anesthetics in both concentrations inhibited that activation.

Conclusions
Volatile anesthetics reduce PMN adhesion in the reperfused coronary system and thereby preserve cardiac function. Reduced expression of the adhesion molecule CD11b on PMNs in the presence of sevoflurane or isoflurane is, at least in part, responsible for the cardioprotective effect.
Preoxygenation
Authors: Baraka Anis S. , Taha Samar K. , Aouad Marie T. , El-Khatib Mohamad F. , Kawkabani Nadine I. 
Published: November 2003

Background
Preoxygenation with tidal volume breathing for 3-5 min is recommended by Hamilton and Eastwood. This report compares tidal volume preoxygenation technique with deep breathing techniques for 30-60 s.

Methods
The study was conducted in two parts on patients undergoing elective coronary bypass grafting. In the first group (n = 32), each patient underwent all of the following preoxygenation techniques: the traditional technique consisting of 3 min of tidal volume breathing at an oxygen flow of 5 l/min; four deep breaths within 30 s at oxygen flows of 5 l/min, 10 l/min, and 20 l/min; and eight deep breaths within 60 s at an oxygen flow of 10 l/min. The mean arterial oxygen tensions after each technique were measured and compared. In the second group (n = 24), patients underwent one of the following techniques of preoxygenation: the traditional technique (n = 8), four deep breaths (n = 8), and eight deep breaths (n = 8). Apnea was then induced, and the mean times of hemoglobin desaturation from 100 to 99, 98, 97, 96, and 95% were determined.

Results
In the first group of patients, the mean arterial oxygen tension following the tidal breathing technique was 392+/-72 mm Hg. This was significantly higher (P<0.05) than the values obtained following the four deep breath technique at oxygen flows of 5 l/min (256+/-73 mm Hg), 10 l/min (286+/-69 mm Hg), and 20 l/min (316+/-67 mm Hg). In contrast, the technique of eight deep breaths resulted in a mean arterial oxygen tension of 369+/-69 mm Hg, which was not significantly different from the value achieved by the traditional technique. In the second group of patients, apnea following different techniques of preoxygenation was associated with a slower hemoglobin desaturation in the eight-deep-breaths technique as compared with both the traditional and the four-deep-breaths techniques.

Conclusion
Rapid preoxygenation with the eight deep breaths within 60 s can be used as an alternative to the traditional 3-min technique.
Effects of Morphine and Tramadol on Somatic and Visceral Sensory Function and Gastrointestinal Motility after Abdominal Surgery
Authors: Wilder-Smith Clive H. , Hill Lauren , Wilkins Justin , Denny Lynnette 
Published: November 2003

Background
Chronic nociceptive input induces sensitization and changes in regulatory reflexes in animal models. In humans, postoperative somatic and visceral sensitization and the secondary effects on reflex gut motility are unclear.

Methods
Somatic and visceral sensation and gastrointestinal motility were evaluated after abdominal hysterectomies in 50 patients who were randomized to receive double-blinded postoperative 48-h infusions of morphine or tramadol. Pain scores, rectal distension, skin electric sensation and pain tolerance thresholds, and gastrointestinal transit were assessed before and after operation, during and after analgesic infusions.

Results
Pain intensity scores decreased similarly with morphine and tramadol infusions (total doses, 66.8+/-20 mg and 732.4+/-152 mg [mean +/- SD], respectively). Skin pain tolerance thresholds in the incisional dermatome remained similar with morphine and tramadol throughout the study. During morphine infusions, pain tolerance thresholds on the shoulder increased (P<0.05) and then decreased after discontinuation on day 4 (P<0.02) compared with before operation. Rectal distension pain tolerance pressure thresholds increased after operation during morphine infusions (P<0.05). Similar but nonsignificant trends occurred with tramadol. Orocecal and colonic transit times increased after operation with both morphine and tramadol (P<0.005), but gastric emptying was prolonged only with morphine (P = 0.03). AU motility and sensory parameters had returned to preoperative levels by 1 month after operation.

Conclusions
Pain control was equally effective with morphine and tramadol infusions. No somatic or visceral sensitization was evident during morphine and tramadol infusions, but pain tolerance thresholds as markers of antinociception were increased more during morphine infusions. The significant sensitization seen only after morphine discontinuation may be due to convergent visceral input. Gut motility was prolonged significantly by visceral surgery itself and also by morphine.
Intravenous Regional Anesthesia Using Lidocaine and Clonidine
Authors: Reuben Scott S. , Steinberg Robert B. , Klatt Jonathan L. , Klatt Margaret L. 
Published: November 2003

Background
Clonidine has been added to local anesthetic regimens for various peripheral nerve blocks, resulting in prolonged anesthesia and analgesia. The authors postulated that using clonidine as a component of intravenous regional anesthesia (IVRA) would enhance postoperative analgesia.

Methods
Forty-five patients undergoing ambulatory hand surgery received IVRA with lidocaine, 0.5%, and were assigned randomly and blindly to three groups. The control group received intravenous saline, the intravenous clonidine group received 1 microg/kg clonidine intravenously, and the IVRA clonidine group received 1 microg/kg clonidine as part of the IVRA solution. After their operations, the patients' pain and sedation scores and analgesic use were recorded.

Results
Patients in the IVRA clonidine group had a significantly longer period of subjective comfort when they required no analgesics (median [range]) for 460 min (215-1,440 min), compared with 115 min (14-390 min) for the control group and 125 min (17-295 min) for the intravenous clonidine group (P<0.0001). The patients who received IVRA with clonidine reported significantly lower pain scores 1 and 2 h after tourniquet deflation compared with the other groups, and they required no fentanyl in the postanesthesia care unit. They also required fewer analgesic tablets (325 mg acetaminophen with 30 mg codeine) in the first 24 h (2+/-1, mean +/- SD) compared with the other two groups, 5+/-1 tablets (control) and 4+/-2 tablets (intravenous clonidine) (P<0.0001). No significant postoperative sedation, hypotension, or bradycardia developed in any of the patients.

Conclusion
The addition of 1 microg/kg clonidine to lidocaine, 0.5%, for IVRA in patients undergoing ambulatory hand surgery improves postoperative analgesia without causing significant side effects during the first postoperative day.
A New Noninvasive Method to Measure Blood Pressure
Authors: Belani Kumar , Ozaki Makoto , Hynson James , Hartmann Thomas , Reyford Hugo , Martino Jean-Marc , Poliac Marius , Miller Ronald 
Published: November 2003

Background
Blood pressure (BP) monitoring with arterial waveform display requires an arterial cannula. We evaluated a new noninvasive device, Vasotrac (Medwave, Arden Hills, MN) that provides BP measurements approximately every 12-15 beats and displays pulse rate and a calibrated arterial waveform for each BP measurement.

Methods
Surgical and critically ill patients (n = 80) served as subjects for the study. BPs, pulse waveforms, and pulse rates measured via a radial artery catheter were compared with those obtained by the Vasotrac from the opposite radial artery. Data were analyzed to determine agreement between the two systems of measurement.

Results
Blood pressure measured noninvasively by the Vasotrac demonstrated excellent correlation (P<0.01) with BP measured via a radial arterial catheter (systolic r2 = 0.93; diastolic r2 = 0.89; mean r2 = 0.95). Differences in BP measured by the Vasotrac versus the radial arterial catheter were small. The mean+/-SD bias and precision were as follows: systolic BP 0.02+/-5.4 mm Hg and 3.9+/-3.7 mm Hg; diastolic BP -0.39+/-3.9 mm Hg and 2.7+/-2.8 mm Hg; mean BP -0.21+/-3.0 mm Hg and 2.1+/-2.2 mm Hg compared with radial artery measurements. The Vasotrac pulse rates were almost identical to those measured directly (r2 = 0.95). The Vasotrac BP waveform resembled those directly obtained radial artery pulsatile waveforms.

Conclusions
In surgical and critically ill patients, the Vasotrac measured BP, pulse rate, and displayed radial artery waveform, which was similar to direct radial arterial measurements. It should be a suitable device to measure BP frequently in a noninvasive fashion.
Incision-induced Changes in Receptive Field Properties of Rat Dorsal Horn Neurons
Authors: Zahn Peter K. , Brennan Timothy J. 
Published: November 2003

Background
To learn more about pain mechanisms produced by surgery, responses of wide dynamic range (WDR) and high threshold (HT) dorsal horn neurons were studied before and after an incision. For this study, an incision was made in a mechanically insensitive area of the receptive field (RF) of the dorsal horn neuron in the plantar aspect of the foot and changes in mechanical response properties were studied.

Methods
Action potentials from single dorsal horn neurons were recorded in halothane anesthetized rats and these neurons were characterized as WDR or HT. Changes in background activity and responses to a variety of mechanical stimuli adjacent to the incision, distant to the injury, and in areas throughout the hindquarters were recorded.

Results
Fifty neurons were recorded (29 WDR, 21 HT cells); only nine of these had a sustained increase in background activity after incision. Marked decreases in threshold to von Frey filaments applied adjacent to the wound occurred in 9 of 28 WDR neurons but in none of 21 HT cells. Von Frey filament thresholds distant to the incision were largely not changed. A blunt mechanical stimulus activated 18 of 22 WDR neurons when applied directly on the incision. HT cells were largely not excited by this mechanical stimulus after incision. The RF to pinch was enlarged in 31 neurons to include areas outside the injury. Pinch RFs of both WDR and HT cells expanded.

Conclusion
These results suggest that incisions in mechanically insensitive areas of the RF of dorsal horn neurons produced little change in background activity; expansion of pinch RFs outside the injury was common. Changing a mechanically insensitive area of the RF of WDR neurons to a mechanically sensitive area by an incision could contribute to pain behaviors that indicate primary mechanical hyperalgesia in behavioral studies.
Trends in Quality of Anesthesia Care Associated with Changing Staffing Patterns, Productivity, and Concurrency of Case Supervision in a Teaching Hospital
Authors: Posner Karen L. , Freund Peter R. 
Published: November 2003

Background
The authors used continuous quality improvement (CQI) program data to investigate trends in quality of anesthesia care associated with changing staffing patterns in a university hospital.

Methods
The monthly proportion of cases performed by solo attending anesthesiologists versus attending-resident teams or attending-certified registered nurse anesthetist (CRNA) teams was used to measure staffing patterns. Anesthesia team productivity was measured as mean monthly surgical anesthesia hours billed per attending anesthesiologist per clinical day. Supervisory ratios (concurrency) were measured as mean monthly number of cases supervised concurrently by attending anesthesiologists. Quality of anesthesia care was measured as monthly rates of critical incidents, patient injury, escalation of care, operational inefficiencies, and human errors per 10,000 cases. Trends in quality at increasing productivity and concurrency levels from 1992 to 1997 were analyzed by the one-sided Jonckheere-Terpstra test.

Results
Productivity was positively correlated with concurrency (r = 0.838; P<0.001). Productivity levels ranged from 10 to 17 h per anesthesiologist per clinical day. Concurrency ranged from 1.6 to 2.2 cases per attending anesthesiologist. At higher productivity and concurrency levels, solo anesthesiologists conducted a smaller percentage of cases, and the proportion of cases with CRNA team members increased. The patient injury rate decreased with increased productivity levels (P = 0.002), whereas the critical incident rate increased (P = 0.001). Changes in operational inefficiency, escalation of care, and human error rates were not statistically significant (P = 0.072, 0.345, 0.320, respectively).

Conclusions
Most aspects of quality of anesthesia care were apparently not effected by changing anesthesia team composition or increased productivity and concurrency. Only team performance was measured; the role of individuals (attending anesthesiologist, resident, or CRNA) in quality of care was not directly measured. Further research is needed to explain lower patient injury rates and increases in critical incident reporting at higher concurrency and productivity levels.