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PubMed1991

[The effect of continuous thoracic peridural anesthesia on the pulmonary function of patients undergoing colon surgery. Results of a randomized study of 116 patients].

In a prospective randomized clinical investigation, we examined the influence of continuous thoracic epidural analgesia (TEA) on pulmonary function and pathologic chest X-ray findings. METHODS. One hundred sixteen patients having resection and/or anastomosis of the colon participated in this study; 57 were randomly assigned to the epidural group, whereas 59 were given systemic analgesia. Both groups were comparable with regard to ASA classification and pre-existing disease, as well as operative procedures and surgeons. Bupivacaine 0.75% was given to the TEA patients pre- and intraoperatively (epidural catheter T8/9), and postoperatively they received bupivacaine 0.25% continuously by motor pump for 3 days. We aimed to reach an analgesic spread from T5 to L2. In order to maintain sufficient analgesia, we had to increase the dosage from 19.2 mg/h on the evening of the operative day to 22.2 mg on the 3rd postoperative day. However, under these conditions the number of blocked segments decreased from 9.3 postoperatively to 6.6 on the 3rd postoperative day. Balanced anesthesia (isoflurane plus fentanyl) was given to the control group. Postoperatively, these patients received systemic analgesia on request (piritramide i.m., tramadol, or a simple analgesic). Vital capacity and pain score (10-point nominal analog score) were evaluated at 1, 8, 24, 36, 48, 60 and 72 h postoperatively. Blood gas analyses were taken at 1, 8, 24, 48 and 72 h, and chest X-rays were performed on the 1st, 3rd, and 8th postoperative days. Statistically significant results are indicated by "*" (P less than 0.05) and "*" (P less than 0.005) and "***" (P less than 0.001). The standard deviations were shown in cases of statistical significance. RESULTS. There were significantly lower pain scores by 1.0-2.2 points at 1, 8, 24 and 36 h postoperatively in the TEA group. Fourteen patients in group I required adjustments of the postoperative pain treatment regime: 6 had a unilateral epidural block; in 4 the catheter was withdrawn involuntarily. Up to the 2nd postoperative day, patients in the control group received systemic analgesics significantly more often. The vital capacity (percentage of preoperative value) was significantly higher in the TEA group than in the control group after 1 h (58.5% vs 51.7%) and 8 h (63.9% vs 56.7%). From the 1st postoperative day on there was no difference between both groups with regard to arterial blood gases, there was no difference in pCO2 between both groups 1 h postoperatively; it was, however, significantly lower in patients receiving bupivacaine at 8, 24, 48 and 72 h. There was no difference in pO2 at any time. The number of pathologic chest X-ray findings showed no difference between both groups. Looking especially for infiltrates, dystelectasis, atelectasis, and congestion, we also could not demonstrate any difference between the groups. (ABSTRACT TRUNCATED AT 400 WORDS)

Anastomosis, Surgical↗
PubMed1986

Hemodynamic effects of metocurine during isoflurane anesthesia.

Anesthesia was induced in 42 adults with thiopentone 3-7 mg/kg i.v. and maintained with isoflurane at a constant inspired concentration of 1-2%. After 30 min of hemodynamic stabilization with continuous muscle relaxation and an absence of surgical stimulation, each patient was randomly assigned to one of four metocurine dosage groups: I - control (n = 11); II - 0.2 mg/kg (n = 10); III - 0.3 mg/kg (n = 10); and IV - 0.4 mg/kg (n = 11). There were no significant hemodynamic changes in Groups I or II. In Groups III and IV mean arterial pressure (MAP) decreased 32% and 26% respectively, and systemic vascular resistance (SVR) decreased 42% and 36%, respectively (P less than 0.01). In Group IV, an increase of 24% in cardiac output was also significant (P less than 0.05). These results, especially in Group IV patients, stand in marked contrast to the lack of hemodynamic effects produced by metocurine during balanced anesthesia.

Adult↗
PubMed2001

Dose-response relationship and infusion requirement of cisatracurium besylate in infants and children during nitrous oxide-narcotic anesthesia.

BACKGROUND: To determine the effect of age on the dose-response relation and infusion requirement of cisatracurium besylate in pediatric patients, 32 infants (mean age, 0.7 yr; range, 0.3-1.0 yr) and 32 children (mean age, 4.9 yr; range, 3.1-9.6 yr) were studied during thiopentone-nitrous oxideoxygen-narcotic anesthesia. METHODS: Potency was determined using a single-dose (20, 26, 33, or 40 microg/kg) technique. Neuromuscular block was assessed by monitoring the electromyographic response of the adductor pollicis to supramaximal train-of-four stimulation of the ulnar nerve at 2 Hz. RESULTS: Least-squares linear regression analysis of the log-probit transformation of dose and maximal response yielded median effective dose (ED50) and 95% effective dose (ED95) values for infants (29+/-3 microg/kg and 43+/-9 microg/kg, respectively) that were similar to those for children (29+/-2 microg/kg and 47+/-7 microg/kg, respectively). The mean infusion rate necessary to maintain 90-99% neuromuscular block during the first hour in infants (1.9+/-0.4 microg x kg(-1) x min(-1); range: 1.3-2.5 microg x kg(-1) x min(-1)) was similar to that in children (2.0+/-0.5 microg x kg(-1) x min(-1); range: 1.3-2.9 microg x kg(-1) x min(-1)). CONCLUSION: The authors conclude that cisatracurium is equipotent in infants and children when dose is referenced to body weight during balanced anesthesia.

Age Factors↗
PubMed1997

Bispectral index monitoring allows faster emergence and improved recovery from propofol, alfentanil, and nitrous oxide anesthesia. BIS Utility Study Group.

BACKGROUND: The bispectral index (BIS), a parameter derived from the electroencephalograph (EEG), has been shown to correlate with increasing sedation and loss of consciousness. This study determined whether addition of BIS monitoring to standard anesthetic practice results in improvements in the conduct of anesthesia or in patient outcomes. METHODS: Three hundred two patients receiving a propofol-alfentanil-nitrous oxide anesthetic were studied at four institutions. Thirty-four patients were initially enrolled to determine preexisting anesthetic practice and patient outcomes at each institution. Subsequent patients were randomized to either standard clinical practice (SP group), or standard practice plus BIS monitoring (BIS group). In all patients, the anesthesiologist attempted to provide a stable anesthetic with the fastest possible recovery. BIS was recorded for all patients, but viewed only in the BIS group. In the BIS group, propofol infusions were adjusted to achieve a target BIS between 45-60, increasing to 60-75 during the final 15 min of the case. In the SP group, propofol dose adjustments were made based only on standard clinical signs. Drug use, intraoperative responses, and patient recovery parameters were recorded. RESULTS: Demographics were similar between groups. Compared with the SP group, patients in the BIS group required lower normalized propofol infusion rates (134 vs. 116 microg x kg[-1] x min[-1]; P < 0.001), were extubated sooner (11.22 vs. 7.25 min; P < 0.003), had a higher percentage of patients oriented on arrival to PACU (43% vs. 23%; P < 0.02), had better postanesthesia care unit (PACU) nursing assessments (P < 0.001), and became eligible for discharge sooner (37.77 vs. 31.70 min; P <0.04). There was no significant difference in the incidence of intraoperative responses between the groups. CONCLUSIONS: Titrating propofol with BIS monitoring during balanced anesthesia decreased propofol use and significantly improved recovery. Intraoperative course was not changed. These findings indicate that the use of BIS may be valuable in guiding the administration of propofol intraoperatively.

Adolescent↗
PubMed2003

The prostaglandins epoprostenol and iloprost increase left ventricular contractility in vivo.

OBJECTIVE: The principal effects of prostaglandin I(2) are vasodilation and inhibition of platelet aggregation induced by a rise in the intracellular second messenger cAMP. In the heart a rise in intracellular myocardial cAMP increases contractility. We examined whether prostaglandin I(2) increases left ventricular contractility in vivo. The effects of epoprostenol and iloprost on left ventricular contractility were assessed in vivo and compared to the effects of adenosine and sodium nitroprusside, which exerts vasodilatory properties independently of cAMP. DESIGN AND SETTING: Prospective, randomized, cross-over in a university laboratory. SUBJECTS: Eleven pigs (25.9+/-2.8 kg, balanced anesthesia). INTERVENTIONS: Each animal was exposed to intravenous sodium nitroprusside, adenosine, and epoprostenol in randomized order. Iloprost was administered at the end due to its longer half-life. The dose was titrated to achieve a 25% reduction in diastolic aortic pressure. MEASUREMENTS AND RESULTS: Left ventricular contractility was assessed before, during, and after each intervention by determination of the endsystolic elastance with the conductance method. While there was no change in endsystolic elastance upon the infusion of adenosine and sodium nitroprusside; endsystolic elastance increased in the case of epoprostenol (57%) and iloprost (71%). CONCLUSIONS: Left ventricular contractility is increased in vivo by epoprostenol and iloprost but not by adenosine or sodium nitroprusside at equipotent hypotensive dose. A contribution of sympathetic reflex activation of cardiac nerves on the increase in left ventricular contractility cannot be completely ruled out.

Adenosine↗
PubMed2001

Perioperative medical management and outcome following thymectomy for myasthenia gravis.

PURPOSE: To describe the evolution of the perioperative management of myasthenia gravis (MG) patients undergoing thymectomy and to question the need for systematic postoperative ventilation. CLINICAL FEATURES: We collected data retrospectively from 36 consecutive MG patients who underwent thymectomy over a 21-yr period, via transthoracic, -cervical or -sternal incisions (n=5, n=7, n=24, respectively). From 1980 to 1993, a balanced anesthetic technique (n=24) included various inhalational agents with opiates and myorelaxants (in eight cases); 22 patients were admitted to the intensive care unit (ICU). Since 1994, i.v. propofol was combined with epidural bupivacaine and sufentanil (n=12); all patients were admitted to the postanesthesia care unit. Short-term postoperative ventilation (median time four hours, range from three to 48 hr) was required in eight patients who had longer hospital stay (median stay=12 days, range (8-28) vs five days (4-15) for patients with early extubation, P <0.05) but similar clinical improvement six months after thymectomy. Postoperative ventilatory support was required more frequently when a balanced anesthetic technique was used (odds ratio=4.2 (1.1-9.7), P=0.03) and particularly when myorelaxants were given (odds ratio=13.9 (2.1-89.8), P=0.009). Leventhal's scoring system had low sensitivity (22.2%) and positive predictive values (25%). CONCLUSIONS: Our data show that the severity of MG failed to predict the need for postoperative ventilation. A combined anesthetic technique was a safe and cost-effective alternative to balanced anesthesia as it provided optimal operating conditions and resulted in fewer admissions in ICU and shorter hospital stays.

Adolescent↗
PubMed2000

Experimental development and validation of a technique for lumboendoscopic anterior fusion of lumbar spine fractures: comparison of endoscopic and open surgery in a live porcine model.

BACKGROUND: Using a porcine model, this study describes the feasibility of a lumboendoscopically guided approach to the lumbar spine for anterior interbody fusion, and compares the results with that of the open procedure. The objectives of this study were to develop a minimally invasive approach to the lumbar spine for anterior fusion in pigs, and to test the validity and safety of the procedure in this porcine model. Besides posterior stabilization, considerable number of thoracolumbar spine (Th12-L5) fractures require intervention for anterior fusion to prevent loss of height of the injured segment and kyphotic deformation. Because anterior fusion needs major surgery (thoracophrenolumbotomy for Th12-L1), which is associated with high morbidity, this study aimed to develop a less traumatic minimally invasive approach. METHODS: Six pigs under balanced anesthesia were used to study the feasibility of the lumboendoscopic approach for bisegmental fusion (iliac crest bone block and dynamic compression plate) from Th15 to L6. In an additional six animals, lumboendoscopic fusion was performed at the level of diaphragm insertion (Th14-Th16), representing Th12-L1 in patients. For comparative analysis, six animals undergoing open thoracophrenolumbotomy and anterior Th14-Th16 fusion served as control subjects. RESULTS: Endoscopic anterior fusion could be successfully performed at all levels of the thoracolumbar spine without major complications. In three cases, unintended opening of the peritoneal cavity was observed, however, without the operative procedure being affected. Comparative analysis revealed a significantly longer p < 0.01 operation time (126 +/- 6.5 min) and increased femoral vein pressure (11.3 +/- 0.7 mmHg) in animals undergoing endoscopic surgery (open procedure, 76.0 +/- 11.6 min and 5.2 +/- 0.5 mmHg). However, the microvascular blood supply (perfusion) to the distal extremities, as assessed by laser Doppler flowmetry, was not affected. CONCLUSIONS: Our study demonstrates that lumboendoscopic anterior spine fusion in pigs is feasible at all levels from Th14 to L6, and can be performed in an acceptable operation time without major complications.

Animals↗
PubMed2000

Reliable noninvasive parameters for early detection of cardiopulmonary compromise induced by carbon dioxide thoracoretroperitoneum in minimally invasive thoracolumboendoscopic spine surgery.

BACKGROUND: Using a novel endoscopic retroperitoneal approach for thoracolumbar anterior spine fusion, we examined the cardiopulmonary effects of the inevitably associated carbon dioxide (CO2) thoracoretroperitoneum and evaluated noninvasive parameters, which may provide early and adequate recognition of cardiopulmonary dysfunction. METHODS: Under balanced anesthesia and paralysis, six pigs subjected to endoscopic CO2 thoracoretroperitoneal spine fusion underwent extensive pulmonary and hemodynamic online monitoring throughout the operative procedure. Open thoracophrenolumbotomy in six pigs served as a control procedure. RESULTS: In contrast to unchanged cardiopulmonary parameters during open thoracolumbar spine surgery, CO2 thoracoretroperitoneum caused significant hypercapnia, hypoxia, and acidemia with concomitant tachycardia, pulmonary hypertension, and systemic hypotension. Ventilatory adjustment, CO2 evacuation, or both promptly reversed the cardiopulmonary effects. Noninvasively assessed end-tidal CO2, peak respiratory pressure, and heart rate were early clues for detecting the tension pneumothorax-like cardiopulmonary dysfunction, as indicated by a significant correlation with the invasively assessed pulmonary hemodynamic parameters and arterial blood gases. CONCLUSIONS: During endoscopic thoracolumbar spine fusion, CO2 thoracoretroperitoneum induces cardiopulmonary dysfunction, which, however, can be detected reliably by changes in end-tidal CO2, peak respiratory pressure, and heart rate, and which can be corrected immediately by appropriate ventilatory adjustments. Therefore, endoscopic CO2 thoracoretroperitoneal spine fusion might not necessarily require extraordinarily extensive and invasive monitoring of systemic and pulmonary hemodynamics, but ventilatory adjustment and intrathoracic pressure evacuation should be readily available to reexpand the lung, and to facilitate rapid normalization of hemodynamic conditions.

Animals↗
PubMed2006

Morbidly obese patients are hemodynamically stable during laparoscopic surgery: a thoracic bioimpedance study.

PURPOSE: Morbid obesity caries an increased risk of cardiovascular morbidity and might be associated with intraoperative hemodynamic instability. Based on clinical observation, we hypothesized that during laparoscopic surgery, morbidly obese patients behave hemodynamically similar to the nonobese patients and remain hemodynamically stable. METHODS: In a prospective trial, thirty nonobese and tthirty morbidly obese (BMI > or = 35 kg/m(2)) patients scheduled for elective laparoscopic surgery were assigned to receive standard balanced anesthesia. We aimed at equianesthetic levels by keeping the BIS (bispectral index) value between 40-50 throughout surgery. End-tidal isoflurane was measured every 5 min. Noninvasive hemodynamic measurements included cardiac index (CI), mean arterial pressure (MAP) and heart rate (HR), recorded every 5 min and at specific predetermined times. Systemic vascular resistance (SVR) was calculated. Episodes of MAP < or = 60 and MAP > or = 130 mmHg or HR < or = 50 and HR > or = 110 bpm occurring throughout surgery and requiring pharmacological intervention were considered main end-points. Additionally, hemodynamic variables were compared at specific time points and overall throughout surgery. Secondary end-points were CI and SVRI. RESULTS: Heart rate was higher in obese patients in head-up position (79 +/- 15 mmHg vs. 65 +/- 12 mmHg - P=0.011). SVR was higher in the nonobese group with head-up position (1978 +/- 665 dynes s cm(-5) vs. 1394 +/- 496 dynes s cm(-5) P=0.01). Mean overall intraoperative MAP, HR, CI and SVR were similar. There were no episodes of MAP < or = 60 and > or =130 mmHg or HR < or = 50 and > or =110 bpm in either of the groups. CONCLUSION: Our study confirmed our hypothesis that for the most periods of laparoscopic surgery, obese patients are hemodynamically as stable as their nonobese counterparts.

Adult↗
PubMed1985

Butorphanol.

Butorphanol (Stadol) is a synthetic agonist-antagonist analgesic from the 14-hydroxymorphinan series. Animal studies display analgesia, antitussive effects, low gastrointestinal activity, limited respiratory depression, some cardiovascular and skeletal muscle actions, diuresis, slight miosis and opiate antagonism. Butorphanol is metabolized in the liver with renal excretion, yielding a half-life of 3-4 h. Pain relief is good to excellent with parenteral administration in 90% of patients with moderate to severe pain. Surgical anesthetic indications involve preoperative and preinduction supplementation, balanced anesthesia and postoperative pain. Side effects are sedation, nausea, elevated pulmonary vascular pressures and rarely CNS excitation. Limited respiratory depression exists. Butorphanol is a potent analgesic agent with a favorable side effect profile.

Anesthesia↗
PubMedDate not supplied

Intubating conditions after pipecuronium bromide: the influence of dose and time.

STUDY OBJECTIVE: To determine the intubating conditions following the administration of pipecuronium bromide in doses of two (0.07 mg/kg) or three (0.1 mg/kg) times ED95 (average dose that gives 95% block of the first twitch). DESIGN: To compare intubating conditions at 11/2 and 21/2 minutes in 41 patients receiving balanced anesthesia. SETTING: Surgical patients at Thomas Jefferson University Hospital. PATIENTS: Forty-one patients undergoing surgical procedure who received general anesthesia. INTERVENTIONS: After obtaining a stable baseline of train-of-four (TOF), 41 patients randomly received either 0.07 mg/kg or 0.1 mg/kg of pipecuronium as a single intravenous (IV) bolus dose, and the trachea was intubated either at 11/2 or 21/2 minutes. MEASUREMENTS AND MAIN RESULTS: Intubating conditions at 21/2 minutes appeared significantly better than those at 11/2 minutes, regardless of the pipecuronium dose. The mean time for T1 (first twitch of TOF) to reach 50% and 90% suppression was 1.36 +/- 0.51 minutes and 2.29 +/- 0.8 minutes, respectively, for the 0.07 mg/kg dose and 1.07 +/- 0.27 minutes and 1.72 +/- 0.45 minutes, respectively, for the 0.1 mg/kg dose. This did not make a significant difference in intubating conditions at either time. The time to 25% recovery of T1 was 68.2 +/- 22 minutes for the 0.07 mg/kg dose and 121.5 +/- 49 minutes for the 0.1 mg/kg dose. In patients who had spontaneous recovery of T1 to between 10% and 25% of control, administration of neostigmine or edrophonium resulted in identical recovery in 10 minutes. However, in patients with less than 10% spontaneous recovery of T1, neostigmine appeared to be superior to edrophonium. CONCLUSION: Pipecuronium has a relatively rapid onset. The trachea could be intubated successfully in 11/2 minutes with a dose of either 0.07 mg/kg or 0.1 mg/kg. If the clinical situation requires perfect relaxation with no movement or bucking, we recommend waiting at least 21/2 minutes.

Adult↗
PubMed2002

Enforced mobilization, early oral feeding, and balanced analgesia improve convalescence after colorectal surgery.

OBJECTIVE: A postoperative regimen using a multimodal approach with enforced mobilization and early oral nutrition has been reported to improve convalescence but has not been compared with other postoperative regimens. METHODS: Forty patients undergoing elective colorectal surgery were randomly allocated to an intervention group receiving comprehensive information on the importance of mobilization, balanced anesthesia, and postoperative analgesia including epidural local anesthetics and enforced postoperative mobilization or a control group receiving anesthesia without epidural local anesthetics, postoperative analgesia with epidural morphine, and mobilization without fixed goals. All patients were offered early oral nutrition. The regimens were compared by means of ambulation time and physical activity, voluntary muscle strength, pulmonary function, and body composition. RESULTS: The ambulation time improved substantially within 22 h in the intervention group versus 3 h in the control group on day 1 (P = 0.0004) and within 8 h versus 2 h on day 4 (P = 0.0003). The voluntary strength of the quadriceps muscle decreased by 3% in the intervention group versus 15% in the control group on day 7 (P = 0.04). Two months postoperatively, the difference between groups was the same (P = 0.02). CONCLUSION: This active per- and postoperative regimen based on a multimodal approach improved ambulation time and muscle function during admission and late convalescence.

Aged↗
PubMed1997

Remifentanil versus alfentanil in a balanced anesthetic technique for total abdominal hysterectomy.

STUDY OBJECTIVES: To compare the intraoperative effects and recovery characteristics of remifentanil hydrochloride and alfentanil when administered as part of balanced anesthesia, and to assess the effects of an additional remifentanil infusion administered as analgesic pretreatment before removal of the uterus. DESIGN: Multicenter, double-blind, randomized, parallel-group study. SETTING: Two university hospitals. PATIENTS: 35 ASA physical status I, II, and III women scheduled for elective total abdominal hysterectomy with general endotracheal anesthesia. INTERVENTIONS: Patients were premedicated with midazolam 0.05 mg/kg intravenously (i.v.). Anesthesia was induced with thiopental 2 mg/kg, vecuronium 0.15 mg/kg, and a single dose of opioid over 60 seconds (Pump 1): remifentanil 2 micrograms/kg (Remi/Placebo and Remi/Remi groups) or alfentanil 50 micrograms/kg (Alf/Placebo group). Anesthesia was maintained with a nitrous oxide/oxygen mixture (66:34 ratio) and a continuous opioid infusion: remifentanil 0.25 microgram/kg/min (Remi/Placebo and Remi/Remi) or alfentanil 0.5 microgram/kg/min (Alf/Placebo). At skin incision, a second blinded drug infusion was also initiated (Pump 2): remifentanil 0.25 microgram/kg/min (Remi/Remi) or saline placebo (Remi/Placebo and Alf/Placebo). Intraoperative responses were controlled with single doses of opioid and/or rate titrations via Pump 1. Pump 2 was terminated on removal of the uterus. Pump 1 was terminated at skin closure. MEASUREMENTS AND MAIN RESULTS: The mean (+/- SD) opioid infusion rates administered for the duration of Pump 2 to suppress responses to removal of the uterus were 0.49 +/- 0.27 microgram/kg/min, 1.99 +/- 1.34 micrograms/kg/min, and 0.49 +/- 0.07 microgram/kg/min for the Remi/Placebo, Alf/Placebo, and Remi/Remi groups, respectively. At these rates, similar proportions of patients in the Remi/Placebo (67%) and the Alf/Placebo (60%) groups had responses. Fewer patients had responses in the Remi/Remi group (8%) compared with the Remi/Placebo and Alf/Placebo groups (p < 0.05). The mean total opioid doses used during maintenance were 84.6 micrograms/kg (Remi/Placebo), 393 micrograms/kg (Alf/Placebo), and 68.7 micrograms/kg (Remi/Remi). Awakening times were significantly shorter (p < 0.05) in the remifentanil population compared with the alfentanil population, but discharge times were similar. More patients received naloxone to reverse opioid effects in the alfentanil population (60%) than in the remifentanil population (20%) (p < 0.05). CONCLUSIONS: A mean remifentanil infusion of 0.49 microgram/kg/min is as effective as a mean alfentanil infusion of 1.99 micrograms/kg/min in suppressing intraoperative responses. Doubling of the remifentanil infusion to 0.5 microgram/kg/min before the major stress event improves suppression of responses and lowers intraoperative use of remifentanil without prolonging recovery times. Remifentanil allows faster awakening times than alfentanil, but preemptive administration of postoperative analgesics is recommended to facilitate discharge.

Adult↗
PubMed2000

Use of an EEG-bispectral closed-loop delivery system for administering propofol.

Closed-loop control of propofol delivery was instituted in three patients who received a propofol infusion as part of: (Case 1) general "balanced" anesthesia, (Case 2) total intravenous anesthesia, and (Case 3) monitored anesthesia care. The bispectral index was the input variable used in a proportioned, integral and differential controller to determine the infusion rate of propofol required to maintain a stable level of hypnosis (Cases 1 and 2) or sedation (Case 3). This feedback control system provided intraoperative hemodynamic stability and a prompt recovery from the sedative-hypnotic effects of propofol.

Adjuvants, Anesthesia↗
PubMed2003

New mathematical model for the correct prediction of the exchangeable blood volume during acute normovolemic hemodilution.

BACKGROUND: The blood volume that has to be exchanged for crystalloids and/or colloids during acute normovolemic hemodilution (ANH) in order to reach a preset target hemoglobin concentration (hb) is usually predicted by the Bourke and Smith formula developed in 1974. This formula systematically overestimates the 'true' exchangeable blood volume (EBV), a fact that may potentially endanger patients because the target hb will be missed and the normovolemic anemia might turn out to be more severe than a priori intended. Our objective was to develop a more accurate mathematical model of hemodilution kinetics and to validate this new model in animals and in patients undergoing ANH. METHODS: Twenty-two anesthetized beagle dogs and 18 patients under balanced anesthesia underwent isovolemic hemodilution with hydroxyethyl starch (HAES 6%, 200 000) to a target hb of 7 g dl-1 or 9 g dl-1, respectively. Exchangeable blood volume predicted by use of the different mathematical models was compared with the blood volume actually exchanged to meet the preset target hb. RESULTS: Calculation of EBV by the Bourke and Smith formula (EBVB + S) systematically overestimated the volume actually exchanged (overestimation: dogs 15%, patients 20%), whereas our new iterative model predicted EBV (EBViterative) more reliably (overestimation: dogs 1%, patients 8%). In both cases EBVB + S differed significantly from the EBViterative. CONCLUSION: Exchangeable blood volume is predicted more accurately by the new iterative model than by the Bourke and Smith formula. The iterative model leads to an improvement in patient safety and provides a physiologically adequate basis for future studies investigating the efficacy of ANH in reducing allogenic blood transfusions.

Algorithms↗
PubMed1999

Cardiopulmonary dysfunction during minimally invasive thoraco-lumboendoscopic spine surgery.

UNLABELLED: The endoscopic retroperitoneal approach to thoracolumbar anterior spine fusion is associated with CO2 insufflation into the thoracic space. We studied the cardiopulmonary effects of this CO2 thoraco-retroperitoneal insufflation compared with the conventional open surgical procedure using thoraco-phreno-lumbotomy in 12 pigs under balanced anesthesia, paralysis, and mechanical ventilation. During open surgery of the thoracolumbar spine, animals exhibited unchanged systemic and pulmonary hemodynamics, as well as ventilation and oxygenation variables. Animals retroperitoneally insufflated with CO2 (12 mm Hg) exhibited a significant increase of PaCO2 and a moderate decrease of PaO2, SaO2, and pH, with insignificant changes of central venous filling pressures and systemic hemodynamics. Endoscopic phrenotomy with thoracic CO2 insufflation instantaneously and drastically affected hemodynamic status and pulmonary gas exchange with marked hypoxia, hypercapnia, systemic hypotension, tachycardia, and pulmonary hypertension within minutes. An increase of minute ventilation, inspiratory oxygen fraction, and positive end-expiratory pressure promptly reversed these cardiopulmonary effects. CO2 evacuation allowed the animals to completely recover and regain almost baseline cardiopulmonary status, except for a reduced arterial blood pressure. Appropriate monitoring and immediate CO2 desufflation may be beneficial in cases of therapy-resistant hemodynamic, oxygenation, and ventilation difficulties. IMPLICATIONS: For endoscopic thoraco-lumbar spine fusion, CO2 thoraco-retroperitoneum-induced cardiopulmonary dysfunction must be of concern, especially in patients with cardiopulmonary compromise. Appropriate monitoring and immediate CO2 desufflation may be beneficial in cases of therapy-resistant hemodynamic, oxygenation, and ventilation difficulties.

Animals↗
PubMed1997

Pharmacokinetics of mivacurium isomers and their metabolites in healthy volunteers after intravenous bolus administration.

BACKGROUND: Previous studies report the pharmacokinetics of mivacurium isomers after an infusion using venous blood sampling. Although the extent of the mivacurium arterial-venous gradient is not known, the sampling site is likely to influence mivacurium pharmacokinetic parameters because the drug is rapidly metabolized as it traverses the circulation. The objectives of this study were (1) to determine the pharmacokinetics of mivacurium isomers in healthy persons after intravenous bolus administration using intensive arterial blood sampling, and (2) to characterize the formation and elimination of mivacurium metabolites in human plasma. METHODS: Eight persons classified as American Society of Anesthesiologists physical status 1 or 2 who were scheduled to undergo elective surgery under balanced anesthesia received 0.15 mg/kg mivacurium chloride as an intravenous bolus. Arterial blood samples were collected every 10 s during the first 2 min and at frequent intervals for 4 h thereafter. Plasma concentrations of mivacurium isomers and their metabolites were determined by two stereoselective high-performance liquid chromatographic methods coupled with fluorometric detection and noncompartmental pharmacokinetic parameters. RESULTS: Mean elimination half-lives of the trans-trans, cis-trans, and cis-cis isomers were 2.4, 2, and 28.5 min, respectively, with corresponding mean plasma clearances of 29.2, 45.7, and 6.7 ml.min 1.kg-1. The volumes of distribution at steady state of the trans-trans, cis-trans, and cis-cis isomers were 0.047, 0.054, and 0.189 l/kg, respectively. Plasma concentrations of monoester and alcohol metabolites peaked 25 s (median) after mivacurium injection, with half-lives in the range of 90 min, except for the cis alcohol metabolite, which was only negligibly and transiently formed. CONCLUSIONS: Substantial hydrolysis of mivacurium isomers by cholinesterases was confirmed by the rapid appearance of mivacurium metabolites in plasma. The intensive arterial sampling proved to be critical for the trans-trans and cis-trans isomers because the area under the curve between 0 and 2 min accounted for 75% and 86% of the total, respectively.

Adolescent↗
PubMed1999

Optimal propofol-alfentanil combinations for supplementing nitrous oxide for outpatient surgery.

BACKGROUND: The combination of propofol and alfentanil with nitrous oxide provides balanced anesthesia with rapid recovery and minimal emetic side effects. The object of this study was to compare recovery parameters at varying proportions of propofol and alfentanil, and to determine the dosing rate and plasma concentration of propofol necessary to supplement nitrous oxide in the presence of varying concentrations of alfentanil METHODS: Forty-eight patients were anesthetized with nitrous oxide, targeted manual infusions of alfentanil (target plasma concentrations of 0, 50, 100, and 150 ng/ml), and propofol at rates that were varied up or down by 25% depending on the response (movement/no movement) of the preceding patient (at the same alfentanil target concentrations) to ulnar-nerve stimulation. The minimum concentrations of propofol and alfentanil required to prevent movement in 50% of patients (EC50) was determined by logistic regression. Speed of emergence and recovery of cognitive function, time to discharge, and incidence of side effects were compared for four different combinations of propofol and alfentanil with nitrous oxide. RESULTS: The EC50 for propofol alone with nitrous oxide was 6.1 microg/ml. AlfentaniL at concentrations of 41+/-17 (SD), 113+/-54, and 130+/-61 ng/mL reduced the EC50 of propofol to 3.3, 2.3, and 2.2 microg/ml, respectively, and decreased emergence time (eye opening) to 8.1, 4.9, and 3.4 min, compared with 24.3 min for propofol alone. Side effects did not differ between groups. CONCLUSIONS: The authors conclude that there is a synergistic effect between propofol and alfentanil, and that combining alfentanil with propofol is associated with faster early recovery.

Adolescent↗