Vancomycin plasma concentrations in cardiac surgery with the use of profound hypothermic circulatory arrest.

OBJECTIVE: This study was undertaken to compare the effect of deep hypothermic circulatory arrest, compared with moderate hypothermia, on the plasma concentrations and pharmacokinetic profile of vancomycin, administered as prophylaxis, in patients undergoing cardiac surgery with cardiopulmonary bypass. METHODS: Two groups of adult cardiac surgery patients were prospectively studied. One group consisted of 12 patients undergoing valvular surgery with moderate hypothermia, and another group was of 12 patients undergoing surgery with the use of profound hypothermic circulatory arrest. Vancomycin was administered before skin incision, and plasma levels were measured at regular intervals for 24h. RESULTS: The plasma concentrations of vancomycin showed a similar pattern in both groups. The pharmacokinetic profile showed a three-compartment model in both groups. CONCLUSION: The dosing of vancomycin, if used as antibiotic prophylaxis, does not need to be adjusted in cardiac surgery patients when undergoing profound hypothermic circulatory arrest, since the plasma concentrations and pharmacokinetic profile are similar to patients with moderate hypothermia. The pharmacokinetic profile, consisting of three compartments, was not changed by the differences in temperature.

Intraoperative fluid replacement and postoperative creatine phosphokinase levels in laparoscopic bariatric patients.

BACKGROUND: Morbid obesity and bariatric surgery are both risk factors for the development of postoperative rhabdomyolysis (RML). RML results from injury to skeletal muscle, and a serum creatine phosphokinase (CK) level >1,000 IU/L is considered diagnostic of RML. The aim of this study was to determine if intraoperative intravenous fluid (IVF) volume affects postoperative CK levels following laparoscopic bariatric operations. STUDY DESIGN: Prospective, single blinded, and randomized trial was conducted. METHODS: Patients scheduled to undergo laparoscopic sleeve gastrectomy, adjustable gastric band, or Roux-en-Y gastric bypass operations were randomized into two groups. Subjects in Group A received 15 ml/kg total body weight (TBW) of IV crystalloid solution during surgery, while subjects in Group B received 40 ml/kg TBW. Preoperative and postoperative CK and creatinine levels and intra- and postoperative urine output were monitored and recorded. RESULTS: Forty-seven patients were assigned to Group A and 53 patients to Group B. Group B patients had significantly higher urine output in the operating room, in the post-anesthesia care unit (PACU), and on postoperative days 0 and 1. Group B patients also had significantly lower serum creatinine level in the PACU and a trend towards lower creatinine levels on postoperative days 0, 1, and 2. There were no statistical differences in CK levels at any time between the two groups. Four patients in Group A and three patients in Group B developed postoperative RML. CONCLUSIONS: Conservative (15 ml/kg) versus liberal (40 ml/kg) intraoperative IVF administration did not change the incidence of RML in patients undergoing laparoscopic bariatric operations. Since the occurrence of RML in this patient population is relatively high, postoperative CK levels should be routinely obtained in patients at special risk.

Does a delay in performing an activated clotting (ACT) test really matter? A study in nonheparinized blood and a single ACT machine.

Activating clotting time (ACT) is a point-of-care, blood clotting test used to monitor anticoagulation. Recently, institutional requirements have required that ACT testing be completed outside the operating room with trained, certified personnel other than anesthesia staff. For this reason, in this study, we looked at whether a delay in processing an ACT makes a significant difference to the ACT results. Twenty patients between 18 and 65 years of age consented to the study, each undergoing non-cardiac surgery, with no intraoperative administration of heparin. The study was approved by our Institutional Review Board. A blood sample was taken from the patient's arterial line in the operating room. Immediately afterward, 1 mL was placed into each of two ACT cartridges and the measurement was done in a Medtronic ACT2 machine. The first ACT value was 126.9 +/- 14.5 seconds. The ACT value at approximately 30 minutes was 108.3 +/- 20.3 seconds (p < .0001). The time between the first and last measurements was 29.4 +/- 3.0 minutes. The results suggest that the ACT values decrease over time between sampling all measurements. At approximately 30 minutes, the ACT values average 15% less than the control measurements. Therefore, it would seem prudent to determine ACT values immediately in the operating room without any delay, using point-of-care testing.

Regional anesthesia and obesity.

The potential advantages of regional anesthesia include minimal airway intervention, less cardiopulmonary depression, excellent postoperative analgesia, less postoperative nausea and vomiting, and shorter recovery room and hospital stays. These concerns are particularly important for the obese surgical patient. This review discusses the application of regional anesthetic techniques in obesity. Further clinical studies are needed to fill the knowledge gap about regional anesthesia and outcome in obese and morbidly obese patients.

Intra-operative fluid volume influences postoperative nausea and vomiting after laparoscopic gastric bypass surgery.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass (RYGBP) is a commonly performed operation for morbid obesity. A significant number of patients experience postoperative nausea and vomiting (PONV) following this procedure. The aim of this study was to determine the effect, if any, of intra-operative fluid replacement on PONV. METHODS: Patients who underwent laparoscopic (RYGBP) for morbid obesity during a 12-month period were included in this retrospective analysis. Demographic data including age, gender, and body mass index (BMI) were collected. Perioperative data also included total volume of intra-operative fluids administered, rate of administration, urine output, length of surgery, and incidence of PONV as determined by nursing or anesthesia records in the postanesthesia care unit (PACU). Data were analyzed by t-test. RESULTS: The table below depicts demographic and perioperative data, comparing patients who experienced PONV (n=125) in the PACU with those who did not (n=55). Values are mean +/- standard deviation. CONCLUSIONS: PONV is a common complication after laparoscopic RYGB. Patient who did not experience PONV received a larger volume of intravenous fluid at a faster rate than similar patients who complained of PONV.

Estimating blood volume in obese and morbidly obese patients.

Preoperative assessment of blood volume (BV) is important for patients undergoing surgery. The mean value for indexed blood volume ((In)BV) in normal weight adults is 70 mL/kg. Since (In)BV decreases in a non-linear manner with increasing weight, this value cannot be used for obese and morbidly obese patients. We present an equation that allows estimation of (In)BV over the entire range of body weights.

Plasma cefazolin levels during cardiovascular surgery: effects of cardiopulmonary bypass and profound hypothermic circulatory arrest.

OBJECTIVES: We sought to assess the effects of cardiopulmonary bypass and profound hypothermic circulatory arrest on plasma cefazolin levels administered for antimicrobial prophylaxis in cardiovascular surgery. METHODS: Four groups (10 patients per group) were prospectively studied: vascular surgery without cardiopulmonary bypass (group A), cardiac surgery with a cardiopulmonary bypass time of less than 120 minutes (group B), cardiac surgery with a cardiopulmonary bypass time of greater than 120 minutes (group C), and cardiac surgery with cardiopulmonary bypass and profound hypothermic circulatory arrest (group D). Subjects received cefazolin at induction and a second dose before wound closure. Arterial blood samples were obtained preceding cefazolin administration, at skin incision, hourly during the operation, and before redosing. Cefazolin plasma concentrations were determined by using a radial diffusion assay, with Staphylococcus aureus as the indicator microorganism. Cefazolin plasma concentrations were considered noninhibitory at 8 microg/mL or less, intermediate at 16 mug/mL, and inhibitory at 32 microg/mL or greater. RESULTS: In group A cefazolin plasma concentrations remained greater than 16 microg/mL during the complete surgical procedure. In group B cefazolin plasma concentrations diminished to 16 microg/mL or less in 30% of the patients but remained greater than 8 microg/mL. In group C cefazolin plasma concentrations decreased to less than 16 microg/mL in 60% of patients and were less than 8 microg/mL in 50% of patients. In group D cefazolin plasma concentrations reached 16 microg/mL in 66% of the patients but decreased to 8 microg/mL in only 1 patient. CONCLUSIONS: For patients undergoing cardiac surgery with a cardiopulmonary bypass time of greater than 120 minutes, a single dose of cefazolin before skin incision with redosing at wound closure does not provide targeted antimicrobial cefazolin plasma levels during the entire surgical procedure. Patients undergoing profound hypothermic circulatory arrest are better protected, but the described protocol of prophylaxis is not optimal.

The dose of succinylcholine in morbid obesity.

The appropriate dose of succinylcholine (SCH) in morbidly obese patients is unknown. We studied 45 morbidly obese (body mass index >40 kg/m2) adults scheduled for gastric bypass surgery. The response to ulnar nerve stimulation of the adductor pollicis muscle at the wrist was recorded using the TOF-Watch SX acceleromyograph. In a randomized double-blind fashion, patients were assigned to one of three study groups. In Group I, patients received SCH 1 mg/kg ideal body weight, in Group II 1 mg/kg lean body weight, and in Group III 1 mg/kg total body weight. After SCH administration, endotracheal intubating conditions were scored. The recovery from neuromuscular block was recorded for 20 min. There was no difference in the onset time of maximum neuromuscular blockade among groups, but maximum block was significantly less in Group I. The recovery intervals were significantly shorter in Groups I and II. In one third of the patients in Group I, intubating conditions were rated poor, whereas no patient in Group III had poor intubating conditions. Our study demonstrates that for complete neuromuscular paralysis and predictable laryngoscopy conditions, SCH 1 mg/kg total body weight is recommended.

Estimating ideal body weight--a new formula.

A simple formula for estimating ideal body weight (IBW) in kilograms for both men and women is presented. The equation IBW = 22 x H2, where H is equal to patient height in meters, yields weight values midway within the range of weights obtained using published IBW formulae.

Tracheal width and left double-lumen tube size: a formula to estimate left-bronchial width.

STUDY OBJECTIVE: To determine which patient parameters best predict left bronchial width (LBW) when selecting the correct size double-lumen tube (DLT). If LBW is known, a DLT that will fit that bronchus can be chosen. DESIGN: Prospective study. SETTING: University medical center. PATIENTS: Three hundred twenty-one consecutive patients scheduled for thoracic surgery and for whom there was a chest radiograph and for whom tracheal width (TW) and LBW could be measured. MEASUREMENTS: Tracheal width and LBW were directly measured from the chest radiograph. Patient demographic data were recorded and then analyzed to see which factor(s) best predicted LBW. Parameters often used for DLT selection (age, sex, height, and weight) as well as TW were compared by univariate and multivariate statistical analysis to see which factor(s) most accurately predicted LBW. MAIN RESULTS: There were weak but significant correlations between age and height and LBW in men, and height and LBW in women. Multivariate statistical analysis showed that, for both men and women, TW was the best predictor of LBW. Sex, height, and weight did not improve predictability over TW alone. The equation that best predicts LBW for both sexes is: LBWmm = (0.50)(TWmm) + 3.7 mm. This model explains 46% of the variance in LBW. As structures measured from a chest radiograph are magnified by 10%, the formula to predict LBW, which normalizes for this magnification factor, is: LBWmm = (0.45)(TWmm(CXR)) + 3.3 mm. CONCLUSIONS: Direct airway measurement is the most accurate way to select an appropriate DLT. However, when direct measurement of LBW cannot be performed, estimating LBW from TW is a better predictor of LBW than either sex, height, or weight.

The intubating laryngeal mask airway: rocuronium improves endotracheal intubating conditions and success rate.

STUDY OBJECTIVE: To assess intubating conditions without neuromuscular blocking drugs, to determine the relation between the dose of rocuronium and the probability of achieving excellent or at least good (good or excellent) intubating conditions with the intubating laryngeal mask airway (ILMA), and finally, to determine the relationship between rocuronium use and the success rate of endotracheal intubation. DESIGN: Prospective, randomized, double-blinded, placebo-controlled study. SETTING: University-affiliated medical center. PATIENTS: Sixty American Society of Anesthesiologists physical status I and II patients undergoing elective surgery. INTERVENTIONS: Anesthesia was induced with propofol 2.5 mg/kg and fentanyl 1 microg/kg. One minute after loss of consciousness, patients received rocuronium 0.2 mg/kg or saline. In the rocuronium group, if intubating conditions were scored as poor, rocuronium dose in the next patient was increased by 0.05 mg/kg. If intubating conditions were scored as good, no change was made, but if conditions were scored as excellent, the dose was decreased by 0.05 mg/kg. One minute after rocuronium or saline administration, an ILMA was used to intubate the trachea. If intubation was unsuccessful, a second attempt was made using the ILMA. MEASUREMENTS: We recorded intubating conditions and the success rate of tracheal intubation. MAIN RESULTS: Without rocuronium, the probability of achieving at least good intubating conditions with the ILMA was 30%. A rocuronium dose of 0.2 mg/kg resulted in a probability of 80% to achieve at least good intubating conditions. Rocuronium significantly increased the success rate of the second intubation attempt. CONCLUSION: To achieve good or excellent intubating conditions with the ILMA, a rocuronium dose lower than the standard intubating dose of 0.6 mg/kg can be used. Neuromuscular blockade increases the success rate of intubation if a second attempt is necessary.

Laryngoscopy and morbid obesity: a comparison of the "sniff" and "ramped" positions.

BACKGROUND: The effect of patient position on the view obtained during laryngoscopy was investigated. METHODS: 60 morbidly obese patients undergoing elective bariatric were studied. Patients were randomly assigned into one of two groups. In Group 1, a conventional "sniff" position was obtained by placing a firm 7-cm cushion underneath the patient's head, thus raising the occiput a standard distance from the operating-table while the patient remained supine. In Group 2, a "ramped" position was achieved by arranging blankets underneath the patient's upper body and head until horizontal alignment was achieved between the external auditory meatus and the sternal notch. Following induction of general anesthesia, tracheal intubation was performed using a Video MacIntosh laryngoscope. The laryngoscopy and intubation sequences were recorded onto videotape. Three independent investigators, unaware as to which position the patient had been in at the time of tracheal intubation, then viewed the videotape and assigned a numerical grade to the best laryngeal view obtained. RESULTS: The "ramped" position improved the laryngeal view when compared to a standard "sniff" position, and this difference was statistically significant (P=0.037). CONCLUSION: The "ramped" position is superior to the standard "sniff" position for direct laryngoscopy in morbidly obese patients.

Kidney transplantation: recent developments and recommendations for anesthetic management.

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. After receiving a transplant, survival rates are higher and comorbidities may resolve. As a consequence, more patients with significant comorbidities such as advanced cardiovascular disease will present for transplantation. This review highlights commonly encountered issues in patients undergoing kidney transplantation and recommendations are made for their anesthetic management.