Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2000
Clinical TrialSequential changes of arterial oxygen tension in the supine position during one-lung ventilation.
To investigate how surgical positions affect the severity and progress of hypoxemia during one-lung ventilation (OLV), we studied 33 adult patients undergoing right thoracotomy with left OLV. The patients were divided into three groups according to the positions during surgery as follows: the supine position (SP) group (n = 11), the left semilateral decubitus position (LSD) group (n = 9), and the left lateral decubitus position (LLD) group (n = 13). Analysis of arterial blood gases was sequentially determined every 5 min for 30 min during OLV (fractional ratio of inspiratory oxygen = 1.0) in each position. OLV was promptly terminated and switched to bi-lung ventilation if Spo2 declined to 90%. Pao2 progressively decreased with time in all three groups (P < 0.01). The incidence of termination of OLV within 30 min was higher in the SP group (82%), compared with that in the LSD (11%) and LLD (8%) groups (P < 0.01). Final Pao2 (65+/-12 mm Hg, mean +/- SD, P < 0.01 versus LLD, P < 0.05 versus LSD) and SaO2 (91%+/-4%, P < 0.01 versus LLD and LSD) at the termination of OLV in the SP group were the lowest. There was no difference between these values in the LSD and LLD groups (128+/-54 mm Hg, 96%+/-2%, and 167+/-69 mm Hg, 97%+/-4%, respectively) 30 min after the start of OLV. The time for Pao2 to decrease to 200 mm Hg calculated from each regression curve was 354 s in the SP group, 583 s in the LSD group, and 798 s in the LLD group. The time for Pao2 to decline to 100 mm Hg was 794 s in the SP group. In the regression curves of the LSD and LLD groups, the Pao2 did not decrease to 100 mm Hg. Heart rate was slow at baseline in the SP group (P < 0.05 versus LSD), but other hemodynamic variables did not differ among the three groups throughout this study. The LSD was as effective as the LLD in avoiding life-threatening hypoxemia during OLV. ⋯ Close observation and prompt counteractions including termination of one-lung ventilation (OLV) are crucial for patients under OLV in the supine position, because life-threatening hypoxemia frequently occurs approximately 10 min after starting OLV, even under 100% oxygen inhalation. The left semilateral decubitus position was as effective as the left lateral decubitus position in avoiding life-threatening hypoxemia during OLV.
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Anesthesia and analgesia · Jan 2000
The anticonvulsant effects of volatile anesthetics on lidocaine-induced seizures in cats.
Large concentrations of sevoflurane and isoflurane, but not halothane, induce spikes in the electroencephalogram. To elucidate whether these proconvulsant effects affect lidocaine-induced seizures, we compared the effects of sevoflurane, isoflurane, and halothane in cats. Fifty animals were allocated to 1 of 10 groups: 70% nitrous oxide (N2O), 0.6 minimum alveolar anesthetic concentration (MAC) + 70% N2O, 1.5 MAC + 70% N2O, and 1.5 MAC of each volatile agent in oxygen. Lidocaine 4 mg x kg(-1) x min(-1) was infused IV under mechanical ventilation with muscle relaxation. Electroencephalogram in the cortex, amygdala, and hippocampus and multiunit activities in the midbrain reticular formation (R-MUA) were recorded. Lidocaine induced spikes first from the amygdala or hippocampus in the 70% N2O and halothane groups and from the cortex in the sevoflurane and isoflurane groups. Lidocaine induced seizures in all cats in the 70% N2O and 0.6 MAC + N2O groups. Seizure occurrence was reduced in the 1.5 MAC + N2O group (P < 0.05 versus 70% N2O). The onset of seizure was delayed in the 0.6 MAC + N2O and 1.5 MAC groups for sevoflurane and isoflurane, but not for halothane, compared with the 70% N2O group (P < 0.05). Lidocaine increased R-MUA with seizure by 130%+/-56% in the 70% N2O group. The increase of R-MUA with seizure was more suppressed in the volatile anesthetic groups than in the 70% N2O group (P < 0.05). In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased. ⋯ Increasingly, epidural blockade is combined with general anesthesia to achieve stress-free anesthesia and continuous pain relief in the postoperative period. In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased.
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Anesthesia and analgesia · Jan 2000
Cardiopulmonary resuscitation during severe hypothermia in pigs: does epinephrine or vasopressin increase coronary perfusion pressure?
The American Heart Association does not recommend epinephrine for management of hypothermic cardiac arrest if body core temperature is below 30 degrees C. Furthermore, the effects of vasopressin administration during hypothermic cardiac arrest are totally unknown. This study was designed to assess the effects of vasopressin and epinephrine on coronary perfusion pressure in a porcine model during hypothermic cardiac arrest cardiopulmonary resuscitation (CPR). Pigs were surface-cooled until their body core temperature was 26 degrees C. After 30 min of untreated cardiac arrest, followed by 3 min of basic life support CPR, 15 animals were randomly assigned to receive, at 5-min intervals, either vasopressin (0.4, 0.4, and 0.8 U/kg; n = 5), epinephrine (45, 45, and 200 microg/kg; n = 5), or saline placebo (n = 5). Compared with epinephrine, mean +/- SEM coronary perfusion pressure was significantly higher (P < 0.05) 90 s and 5 min after the first (35+/-4 vs 22+/-3 mm Hg and 37+/-2 vs 16+/-2 mm Hg) and the second vasopressin administration (40+/-5 vs 26+/-5 mm Hg and 36+/-5 vs 18+/-2 mm Hg, respectively). After the third drug administration, coronary perfusion pressure in the epinephrine group increased dramatically and was comparable to vasopressin. In the saline placebo group, coronary perfusion pressure was significantly lower (P < 0.05) than in the vasopressin and epinephrine groups. Six animals treated with epinephrine or vasopressin had transient return of spontaneous circulation, whereas all placebo animals died (P < 0.05). During CPR in severe hypothermia, administration of both vasopressin and epinephrine resulted in significant increases in coronary perfusion pressure when compared with placebo. ⋯ Our study was designed to assess the effects of vasopressin and epinephrine in a porcine model simulating cardiac arrest during severe hypothermia. This study demonstrates that the administration of both emergency drugs results in an increased perfusion pressure in the heart.
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Anesthesia and analgesia · Jan 2000
Comparative StudyInhaled nonimmobilizers do not alter the middle latency auditory-evoked response of rats.
General anesthetics cause surgical immobility and oblivion (unconsciousness and amnesia). A class of compounds known as "nonimmobilizers" were predicted to be anesthetic, based on their physiochemical properties, but found to cause only amnesia. In humans, cerebrocortical electrical activity after auditory stimulation is depressed by concentrations of anesthetics which impair auditory recall. We sought to use these evoked responses to characterize the effects of the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (2N) and conventional inhaled anesthetics on early sensory processing in rats. Unrestrained rats with chronically implanted epidural silver screw electrodes were put into a chamber. On separate days, the same population of rats were exposed to isoflurane, desflurane, nitrous oxide, or 2N, each at several subminimum alveolar concentration of anesthetic required to eliminate movement in response to a noxious stimulus concentrations. After equilibration at each concentration, auditory-evoked responses were obtained. The behavioral state (activity and righting reflex) and electroencephalogram were also examined. 2N did not significantly change the middle latency auditory-evoked response, whereas the anesthetics all slowed conduction and depressed amplitude in a dose-dependent fashion. 2N neither depressed the righting reflex, nor induced epileptiform activity. ⋯ Although the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (2N) suppresses learning, we find that 2N does not depress middle latency auditory-evoked responses. This suggests that 2N may suppress learning by depressing transmission through rostral subcortical structures, such as the amygdala, rather than by acting on the brainstem or neocortical structures.
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Anesthesia and analgesia · Jan 2000
Clinical TrialRapid tracheal intubation with large-dose rocuronium: a probability-based approach.
There are situations in anesthesia in which it may be desirable to achieve rapid tracheal intubation with perfect conditions, i.e., no coughing or straining. To determine the dose of rocuronium that gives a high probability of achieving perfect conditions for rapid (within 60 s) tracheal intubation, we administered a range of doses of rocuronium, some larger than used previously. Sixty adults, anesthetized with thiopental 4 mg/kg IV and alfentanil 10 microg/kg IV, received rocuronium 0.4 to 2.0 mg/kg IV. We used logistic regression to define the relationship of rocuronium dose to probability of achieving perfect intubation conditions. We estimated the doses giving 90% and 95% probability of achieving perfect intubation and used resampling to determine confidence limits for these estimates. Rocuronium 1.85 and 2.33 mg/kg gave, respectively, 90% and 95% probability of perfect intubation conditions. The confidence limits (5th and 95th percentile) for these estimates were 1.15 to 2.31 and 1.23 to 3.22 mg/kg, respectively. In conclusion, it is possible to achieve perfect intubation conditions with large doses of rocuronium, but the long duration of action and expense may limit the usefulness of the technique. ⋯ We found that it is possible to have a 90% probability of achieving perfect conditions for rapid tracheal intubation with large (up to 2.0 mg/kg) doses of rocuronium. These large doses of rocuronium may be useful in, for instance, head trauma or open globe injuries if succinylcholine is contraindicated.