Anesthesia and analgesia
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Anesthesia and analgesia · Oct 1997
Baralyme dehydration increases and soda lime dehydration decreases the concentration of compound A resulting from sevoflurane degradation in a standard anesthetic circuit.
Soda lime and Baralyme brand carbon dioxide absorbents degrade sevoflurane to CF2 = C(CF3)OCH2F, a potentially nephrotoxic vinyl ether called Compound A. Dehydration of these absorbents increases both the degradation of sevoflurane to Compound A and the degradation of Compound A. The balance between sevoflurane degradation and Compound A degradation determines the concentration of Compound A issuing from the absorbent (the net production of Compound A). We studied the effect of dehydration on the net production of Compound A in a simulated anesthetic circuit. Mimicking continuing oxygen delivery for 1, 2, or 3 days after completion of an anesthetic, we directed a "conditioning" fresh gas flow of 5 L/min or 10 L/min retrograde through fresh absorbent in situ in a standard absorbent system for 16, 40, and/or 64 h. The conditioned absorbent was subsequently used (without mixing of the granules) in a standard anesthetic circuit in which a 3-L rebreathing bag substituted for the lung. Metabolism was mimicked by introducing 250 mL/min carbon dioxide into the "lung," and the lung was ventilated with a minute ventilation of 10 L/ min. At the same time, we introduced sevoflurane in a fresh gas inflow of 2 L/min at a concentration sufficient to produce an inspired concentration of 3.2%. Because of increased sevoflurane destruction by the absorbent, progressively longer periods of conditioning (dehydration) and/or higher inflow rates increased the delivered (vaporizer) concentration of sevoflurane required to sustain a 3.2% concentration. Dehydration of Baralyme increased the inspired concentration of Compound A by up to sevenfold, whereas dehydration of soda lime markedly decreased the inspired concentration of Compound A. ⋯ Economical delivery of modern inhaled anesthetics requires rebreathing of exhaled gases after removal of carbon dioxide. However, carbon dioxide absorbents (Baralyme/soda lime) may degrade anesthetics to toxic substances. Baralyme dehydration increases, and soda lime dehydration decreases, degradation of the inhaled anesthetic sevoflurane to the toxic substance, Compound A.
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Anesthesia and analgesia · Oct 1997
Comparative StudyThe Yale Preoperative Anxiety Scale: how does it compare with a "gold standard"?
Evaluating the effectiveness of interventions directed toward the treatment of preoperative anxiety in children has been hindered by the absence of a statistically valid measurement tool. In a previous investigation, we developed an instrument (Yale Preoperative Anxiety Scale [YPAS]) that can be used to assess anxiety in children undergoing induction of anesthesia. The purpose of the present investigation was to modify and expand the applicability of the instrument to the preoperative holding area and to validate the modified instrument (m-YPAS) against a recognized "gold standard" (State-Trait Anxiety Inventory for Childrens [STAIC]). Videotapes of children in a preoperative holding area were analyzed by the investigators. The existing five categories of the YPAS were found to reflect most of the behaviors observed. Several items, however, were modified to describe new behaviors observed. Reliability analysis using weighted kappa statistics revealed that inter-observer agreement ranged from 0.68 to 0.86, whereas intraobserver weighted kappa ranged from 0.63 to 0.90. Concurrent validity between the YPAS and the STAIC was acceptable (P = 0.01, r = 0.79). Construct validity was high as assessed by increased m-YPAS scores from the preoperative holding area (28 +/- 8) to entering the operating room (35 +/- 12), to introduction of the anesthesia mask (43 +/- 15;F [1,36] = 0.6, P = 0.001]. Showing good to excellent observer reliability and high concurrent and construct validity, the m-YPAS proved to be an appropriate tool for assessing children's anxiety during the perioperative period. ⋯ The absence of a statistically valid measurement tool that can be applied easily in perioperative settings hinders the evaluation of interventions directed toward treatment of preoperative anxiety in children. The authors describe the development of such a tool, the modified Yale Preoperative Anxiety Scale.
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Postoperative pain is a common reason for the delayed discharge and unanticipated hospital admission of out-patients. In this study, we examined the pattern of pain in ambulatory surgical patients and determined those factors that predict postoperative pain. Ten thousand eight consecutive ambulatory surgical patients were prospectively studied. Preoperative patient characteristics, intraoperative variables, and pain in the postanesthesia care unit (PACU) and the ambulatory surgical unit (ASU) and 24 h postoperatively were documented. The incidence of severe pain was 5.3% in the PACU, 1.7% in the ASU, and 5.3% 24 h postoperatively. In the PACU, younger male adults (36 +/- 13 vs 47 +/- 22 yr), ASA physical status I patients, and patients with a higher body mass index (26 +/- 5 vs 25 +/- 5 kg) had a higher incidence of severe pain. In the group with severe pain, the duration of anesthesia, the duration of stay in the PACU and the ASU, and the time to discharge was longer than in the group without severe pain. In the PACU, orthopedic patients had the highest incidence of pain (16.1%), followed by urologic (13.4%), general surgery (11.5%), and plastic surgery (10.0%) patients. In patients who had general anesthesia, the intraoperative dose of fentanyl was significantly smaller in the group with severe pain than in the group without severe pain when body mass index and duration of anesthesia were taken into consideration. Body mass index, duration of anesthesia, and certain types of surgery were significant predictors of severe pain in the PACU. This knowledge will allow us to identify those patients at risk of severe postoperative pain and manage them prophylactically. ⋯ The pattern of pain was examined in 10,008 consecutive ambulatory surgical patients. The incidence of severe pain was 5.3% in the postanesthesia care unit, 1.7% in the ambulatory surgical unit, and 5.3% 24 h postoperatively. Body mass, duration of anesthesia, and certain types of surgery were significant predictors of pain in the postanesthesia care unit. These data will allow us to better predict those patients who need intense prophylactic analgesic therapy.
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Anesthesia and analgesia · Oct 1997
Randomized Controlled Trial Clinical TrialTransfusion of autologous, hydroxyethyl starch-cryopreserved red blood cells.
In this prospective, randomized study, we investigated the safety and efficacy of the transfusion of hydroxyethyl starch (HES) cryopreserved red blood cells (RBC) compared with the transfusion of liquid-stored RBC in patients undergoing major orthopedic or urologic surgery. Thirty-six patients donated autologous blood 35 +/- 6 days before elective surgery. Only the first of 3.5 +/- 1.3 donated units of RBC was randomly assigned to be stored in the liquid state at 4 degrees C in phosphate/adenine/guanosine/glucose/saline-Mannitol or frozen below -130 degrees C by means of liquid nitrogen after the addition of HES (molecular weight 200,000 Dalton, degree of substitution 0.5, final concentration 11.5% wt/wt) as a cryoprotectant. After induction of anesthesia, patients donated 900 mL of autologous blood before they received one unit of liquid-stored RBC in Group 1. In Group 2, one unit of cryopreserved autologous RBC was transfused after removal of the cryoprotectant HES. In Group 3, patients received one unit of cryopreserved RBC without any manipulation after thawing. Patients in Groups 1 and 2 received additional 500 mL of 10% HES. Hemodynamic variables, arterial blood gases, plasma hemoglobin, and arterial lactate concentrations were measured after the induction of anesthesia, after hemodilution, and at 10-min intervals after transfusion of the respective RBC concentrate over a period of 40 min. Skeletal muscle tissue oxygen tension was measured in the quadriceps muscle using an automatically stepwise-driven oxygen partial pressure electrode. We found no differences among groups concerning demographics, arterial blood gas values, and lactate concentrations and observed no adverse reactions after transfusion of the conventionally stored or cryopreserved RBC. Hemodynamic variables did not differ among groups, with the exception of an increased mean arterial blood pressure after the transfusion of cryopreserved unwashed RBC. In all groups, the skeletal muscle tissue oxygen tension remained constant after hemodilution and increased after transfusion of either washed or unwashed cryopreserved RBC. Although the free plasma hemoglobin concentration remained constant after the transfusion of liquid-stored RBC (26 +/- 8 mg/dL), the plasma hemoglobin concentration increased twofold after the transfusion of cryopreserved washed RBC (60 +/- 12 mg/dL) and threefold after transfusion of cryopreserved unwashed RBC (98 +/- 20 mg/dL). The authors conclude that transfusion of one unit of RBC after cryopreservation with HES is safe and well tolerated by patients. Intravascular volume replacement and skeletal muscle oxygenation characteristics by erythrocytes did not differ between liquid-stored and cryopreserved RBC. ⋯ This study examined whether a colloid should be used to store blood. Our data suggest that the transfusion of one unit of red blood cells after cryopreservation with hydroxyethyl starch is safe and well tolerated by patients. The effects of intravascular volume replacement and skeletal muscle oxygenation provided by red blood cells after liquid storage or cryopreservation were not different.
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Anesthesia and analgesia · Oct 1997
Randomized Controlled Trial Comparative Study Clinical TrialSplanchnic and renal deterioration during and after laparoscopic cholecystectomy: a comparison of the carbon dioxide pneumoperitoneum and the abdominal wall lift method.
Carbon dioxide (CO2) pneumoperitoneum together with an increased intraabdominal pressure (IAP) induces a hemodynamic stress response, diminishes urine output, and may compromise splanchnic perfusion. A new retractor method may be less traumatic. Accordingly, 30 ASA physical status I or II patients undergoing laparoscopic cholecystectomy were randomly allocated to a CO2 pneumoperitoneum (IAP 12-13 mm Hg) (control) or to a gasless abdominal wall lift method (retractor) group. Anesthesia and intravascular fluids were standardized. Direct mean arterial pressure (MAP), urine output, urine-N-acetyl-beta-D-glucosaminidase (U-NAG), arterial blood gases, gastric mucosal PCO2, and intramucosal pH (pHi) were measured. Normoventilation was instituted in all patients. MAP increased (P < 0.001) only with CO2 pneumoperitoneum. Minute volume of ventilation had to be increased by 35% with CO2 insufflation. PaCO2 was significantly higher (P < 0.05) for 3 h postoperatively in the control group. Diuresis was less (P < 0.01) and U-NAG levels (P < 0.01) higher in the control group. The pHi decreased after induction of pneumoperitoneum up to three hours postoperatively and remained intact in the retractor group. We conclude that the retractor method for laparoscopic cholecystectomy ensures stable hemodynamics, prevents respiratory acidosis, and provides protection against biochemical effects, which reveal the renal and splanchic ischemia caused by CO2 insufflation. ⋯ A mechanical retractor method (gasless) was compared with conventional CO2 pneumoperitoneum for laparoscopic cholestectomy. The gasless method ensured stable hemodynamics, prevented respiratory acidosis, and provided protection against the renal and splanchnic ischemia seen with CO2 pneumoperitoneum.