Charles W. Whitten

Anesthetic considerations for bariatric surgery.

According to the National Institutes of Health, obesity is a major health problem with clearly established health implications, including an increased risk for coronary artery disease, hypertension, dyslipidemia, diabetes mellitus, gallbladder disease, degenerative joint disease, obstructive sleep apnea, and socioeconomic and psychosocial impairment (1). The risk of developing one or more of these obesityrelated conditions is based on body mass index (BMI), with 25–30 kg/m 2 being low risk and 40 kg/m 2 being very high risk (2). The prevalence of obesity in the 18- to 29-yr-old group increased from 12% in 1991 to 18.9% in 1999 (3). Bariatric surgery encompasses a variety of surgical weight loss procedures used to treat morbid obesity. Obesity is clinically expressed in terms of BMI or Quetelet’s index (4), which is derived by dividing weight by the square of height to estimate the degree of obesity. Thus, BMI body weight (kg)/height 2 (m 2 ). Morbid obesity is a BMI more than 35 kg/m 2 , and super morbid obesity is BMI more than 55 kg/m 2 . The indications for surgical treatment of severe obesity, as outlined in the 1991 National Institutes of Health Consensus Development Conference Panel, include an absolute BMI more than 40 kg/m 2 or BMI more than 35 kg/m 2 in combination with lifethreatening cardiopulmonary problems or severe diabetes mellitus (1). Patients seeking surgical weight loss must have proven attempts at medically supervised weight loss. Documentation of loss of 5% to 10% excess body weight or weight gain after at least 6 mo of diet modification, exercise, and medical therapy or nonimprovement in comorbid conditions during this period indicates failure. Studies have shown that weight loss of 5%–10% of initial body weight improves glucose intolerance and Type II diabetes, hypertension, and dyslipidemia (5–7). The average expenditure is approximately

Aprotinin for Primary Coronary Artery Bypass Grafting: A Multicenter Trial of Three Dose Regimens

7000 per year per patient on weight loss programs and equipment. Unfortunately, long-term weight loss is the exception, and most patients regain weight, sometimes more than they initially lost.

Assessment of changes in coagulation in parturients with preeclampsia using thromboelastography

BACKGROUND High-dose aprotinin reduces transfusion requirements in patients undergoing coronary artery bypass grafting, but the safety and effectiveness of smaller doses is unclear. Furthermore, patient selection criteria for optimal use of the drug are not well defined. METHODS Seven hundred and four first-time coronary artery bypass grafting patients were randomized to receive one of three doses of aprotinin (high, low, and pump-prime-only) or placebo. The patients were stratified as to risk of excessive bleeding. RESULTS All three aprotinin doses were highly effective in reducing bleeding and transfusion requirements. Consistent efficacy was not, however, demonstrated in the subgroup of patients at low risk for bleeding. There were no differences in mortality or the incidences of renal failure, strokes, or definite myocardial infarctions between the groups, although the pump-prime-only dose was associated with a small increase in definite, probable, or possible myocardial infarctions (p = 0.045). CONCLUSIONS Low-dose and pump-prime-only aprotinin regimens provide reductions in bleeding and transfusion requirements that are similar to those of high-dose regimens. Although safe, aprotinin is not routinely indicated for the first-time coronary artery bypass grafting patient who is at low risk for postoperative bleeding. The pump-prime-only dose is not currently recommended because of a possible association with more frequent myocardial infarctions.

Thromboelastography: past, present, and future.

BACKGROUND Preeclampsia is associated with a risk of abnormal hemostasis that occurs most commonly secondary to thrombocytopenia. Thromboelastography measures whole blood coagulation and has been used to manage coagulation defects in obstetric patients. The authors conducted this investigation in a large number of preeclamptic women to assess changes in coagulation using thromboelastography. METHODS Thromboelastography and platelet counts were performed in 52 healthy pregnant women, 140 mild preeclamptic women, and 114 severe preeclamptic women in active labor using disposable plastic cups and pins and native whole blood. In preeclamptic patients with a platelet count <100,000/mm3, conventional coagulation tests were also performed. Epidural analgesia was provided in some women when they requested pain relief. RESULTS Fifteen percent of all preeclamptic women (38 of 254) and 2% (1 of 52) of healthy pregnant women had a platelet count <100,000/mm3. The incidence of thrombocytopenia <100,000/mm3 was 3% (4 of 140) and 30% (34 of 114) in mild preeclamptic patients and severe preeclamptic patients, respectively. Severe preeclamptic patients with a platelet count <100,000/mm3 were significantly hypocoagulable when compared to the other study groups. Ten severe preeclamptic women with a platelet count <100,000/mm3 had a maximum amplitude <54 mm (the lower limit of maximum amplitude in healthy pregnant women enrolled in this investigation). None of the mild preeclamptic women had a maximum amplitude <54 mm. Five severe preeclamptic women with a platelet count <100,000/mm3 had an abnormal coagulation profile, whereas all four mild preeclamptic women with a platelet count <100,000/mm3 had a normal coagulation profile. CONCLUSION This study shows that severe preeclamptic women with a platelet count <100,000/mm3 are hypocoagulable when compared to healthy pregnant women and other preeclamptic women.

Effects of three anesthetic induction techniques on heart rate variability

THIS issue of ANESTHESIOLOGY contains an article by Camenzind et al. regarding the influence of citrate storage on thromboelastography (TEG Haemascope Corp.). Although the TEG is most commonly performed on a native (uncitrated) sample, the use of citrated blood permits longer delays after sample acquisition, thus facilitating ancillary or research laboratory analysis. Camenzind et al. nicely outline some of the issues related to the impact of sample storage on the TEG. Anesthesiology, as a specialty, has taken a leading role in evaluating the TEG as a nearsite monitor of hemostasis in several clinical settings. Many issues, however, remain unresolved about how to use the TEG to guide clinical decision-making. The purpose of this Editorial View is to briefly review studies that have lead to current applications of the TEG and to outline future challenges that need to be addressed for its broader use.

Antifibrinolytic therapy during cardiopulmonary bypass reduces proinflammatory cytokine levels: a randomized, double-blind, placebo-controlled study of ϵ-aminocaproic acid and aprotinin

STUDY OBJECTIVE To investigate the effects of different clinical induction techniques on heart rate variability (HRV). DESIGN Two studies are reported. Study 1 prospectively compared the effects of two induction techniques (etomidate vs. thiopental sodium) known to have widely disparate effects on cardiovascular reflexes. Study 2 specifically investigated whether the vagotonic effects of sufentanil cause an increase in vagally mediated HRV. SETTING Elective surgery in a university-affiliated hospital. PATIENTS Study 1: 18 ASA physical status I patients having minor surgery; Study 2: 10 ASA physical status III and IV patients having cardiac surgery. INTERVENTIONS In Study 1, anesthesia was induced with either etomidate 0.3 mg/kg or thiopental sodium 4 mg/kg with 60% nitrous oxide in oxygen. In Study 2, anesthesia was induced with a sufentanil infusion (total dose 2.9 +/- 0.2 micrograms/kg). MEASUREMENTS AND MAIN RESULTS The electrocardiogram-derived heart rate signal was subjected to power spectral analysis (similar to electroencephalographic analysis) to obtain measurements of (1) absolute HRV power [units of (beats per minute)2] within defined frequency ranges (HRVLO = power between 0 and 0.125 Hz; HRVHI = power between 0.126 and 0.5 Hz; HRVTOT = HRVLO + HRVHI) and (2) normalized HRV power (the percentage of total power) within these same frequency ranges [e.g., %HRVHI = (HRVHI/HRVTOT) x 100%]. In Study 1, both techniques caused large reductions in HRVTOT. The reduction caused by the thiopental sodium technique (-89% +/- 2%) significantly exceeded that caused by the etomidate technique (-58% +/- 13%, p less than 0.02). In Study 2, sufentanil decreased absolute power measurements of vagally mediated HRV (-69 +/- 12 change in HRVHI) but increased corresponding normalized measurements of vagally mediated HRV (90% +/- 30% increase in %HRVHI). CONCLUSIONS In Study 1, the greater reduction in HRV with the thiopental sodium technique provides evidence that the depressant effects of anesthetics on HRV are related in part to their effects on cardiovascular reflexes. However, the significant depression in HRV caused by the etomidate technique suggests that mechanisms other than baroreflex depression (e.g., impaired consciousness) also are important in these depressant effects. In Study 2, the decrease in HRVHI caused by sufentanil documents that absolute power measurements of vagally mediated HRV are not correlated with changes in parasympathetic tone during a potent opioid induction. This lack of a correlation may result from the decrease in total HRV observed with loss of consciousness. The increase in %HRVHI suggests that normalized measurements of HRV may still provide an index of changes in sympathetic-parasympathetic balance, even when total HRV is decreased following anesthetic administration.

Dexamethasone in combination with dolasetron for prophylaxis in the ambulatory setting: effect on outcome after laparoscopic cholecystectomy.

OBJECTIVES Aprotinin is a broad-spectrum serine protease inhibitor that has been shown to attenuate the systemic inflammatory response in patients undergoing cardiac surgery with cardiopulmonary bypass. Although epsilon-aminocaproic acid is similar to aprotinin in its ability to inhibit excessive fibrinolysis (ie, plasmin activity and D-dimer formation), its ability to influence proinflammatory cytokine production remains unclear. This study was designed to compare the effects of epsilon-aminocaproic acid and aprotinin on plasma levels of interleukin-6 and interleukin-8 during and after cardiopulmonary bypass. METHODS Sixty patients were randomized in a double-blind fashion to receive epsilon-aminocaproic acid, aprotinin, or saline (placebo) in similar dosing regimens (loading dose, pump prime, and infusion). Arterial blood samples were collected before, during, and after cardiopulmonary bypass, and plasma levels of D-dimer, interleukin-6, and interleukin-8 were measured. Data were analyzed using repeated measures analysis of variance. RESULTS Both epsilon-aminocaproic acid and aprotinin administration resulted in significant (P <.05) reductions in D-dimer and interleukin-8 levels compared with saline. These reductions in D-dimer and interleukin-8 levels did not differ between the 2 drug-treated groups. The effect of these two antifibrinolytic agents on interleukin-6 was qualitatively similar to that noted with interleukin-8 but did not reach statistical significance. CONCLUSIONS When dosed in a similar manner, epsilon-aminocaproic acid seems to be as effective as aprotinin at reducing interleukin-6 and interleukin-8 levels in patients undergoing primary coronary artery bypass graft surgery. These data indicate that suppression of excessive plasmin activity or D-dimer formation or both may play an important role in the generation of proinflammatory cytokines during and after cardiopulmonary bypass.

Ventilation, Thermal Noise, and Errors in Cardiac Output Measurements after Cardiopulmonary Bypass

Background Postoperative nausea and vomiting after laparoscopic cholecystectomy remains a common problem despite routine antiemetic prophylaxis. Therefore, the authors investigated the effect of administering 4 mg intravenous dexamethasone as an adjunct to a 5-HT3 antagonist (12.5 mg intravenous dolasetron) with respect to patient outcome. Methods Outpatients (N = 140) were enrolled in this prospective, randomized, placebo-controlled, double-blind, institutional review board–approved protocol involving two antiemetic treatment groups. After induction of anesthesia, the control group received 1 ml intravenous saline, whereas the dexamethasone group received 4 mg intravenous dexamethasone. Both groups received 12.5 mg intravenous dolasetron at the time of gallbladder removal. A blinded observer recorded the recovery times, emetic episodes, rescue antiemetics, maximum nausea score, and time to achieve discharge criteria. Postdischarge side effects, as well as patient satisfaction and quality of recovery scores were assessed at 24 h after surgery. Results Although there was no difference in the incidence of postoperative nausea and vomiting in the early recovery period, the dexamethasone group had a shorter stay in the day-surgery unit (136 ± 57 vs. 179 ± 62 min) and more rapidly achieved discharge criteria (161 ± 32 vs. 209 ± 39 min). In addition, fewer patients in the dexamethasone group experienced nausea at home within 24 h after discharge (13 vs. 28%, P < 0.05). Finally, the dexamethasone group reported higher quality of recovery and patient satisfaction scores (P < 0.05). Conclusions The authors conclude that the adjunctive use of 4 mg intravenous dexamethasone shortened the time to achieve discharge criteria and improved the quality of recovery and patient satisfaction scores after laparoscopic cholecystectomy procedures in outpatients receiving prophylaxis with 12.5 mg intravenous dolasetron.

The influence of crystalloid and colloid replacement solutions in acute normovolemic hemodilution: a preliminary survey of hemostatic markers.

BackgroundThe authors observed transient increases in the amplitude of respiratory variations in pulmonary artery blood temperature in many patients after cardiopulmonary bypass (CPB). This increased “thermal noise” may significantly influence measurements of thermodilution cardiac outputs (TDCO) performed during this time. MethodsThe authors recorded the peak-to-peak amplitude of respiratory variations in pulmonary artery blood temperature in 15 patients during the first 35 min after CPB. Possible relationships between the amplitude of these variations and the magnitude of temperature differences between commonly monitored body temperature sites (nasopharyngeal, rectal, bladder, and pulmonary artery) were also examined. In ten additional patients, the authors investigated the influence of these increased respiratory variations on TDCO measurements by correlating the maximum variation in three successive TDCO measurements with the peak-to-peak amplitude of the respiratory variations in pulmonary artery blood temperature. Potential error in TDCO measurements caused by these increased respiratory variations in pulmonary artery blood temperature were also examined using model calculations of the effects of respiratory variations in pulmonary artery blood temperature on measured TDCO thermal areas. ResultsIn the first 15 patients, the mean amplitude of respiratory variations in pulmonary artery blood temperature after CPB (mean ± SEM) were: (1) within 5 min after CPB, 0.037 ± 0.004°C; (2) 10 min after #1, 0.025 ± 0.003°C; (3) 20 min after #1, 0.019 ± 0.003°C; and (4) 30 min after #1, 0.012 ± 0.002°C. There were no significant correlations between the magnitude of the respiratory variation in pulmonary artery blood temperature and the observed temperature differences between body sites. Four patients had pulmonary artery blood temperature variations in excess of the maximum amplitude previously reported in man (0.05°C). In the next ten patients, the maximum variation between three successive TDCO measurements taken at specified times in the respiratory cycle (end Inspiration, end exhalation, and 3 s after end exhalation) was significantly correlated with the amplitude of respiratory variations in pulmonary artery blood temperature (r = 0.83, P < 0.001). Four patients with increased respiratory variations in pulmonary artery blood temperature had variations in TDCO measurements exceeding 21/min. Subsequent model calculations demonstrated that the magnitude of potential error in TDCO measurements is dependent on both the amplitude of the respiratory variations in pulmonary artery blood temperature and the baseline cardiac output. On the basis of these thermal area calculations, potential errors of 15–50% could be caused by respiratory variations in pulmonary artery blood temperature > 0.05°C. ConclusionsThe authors concluded that respiratory variations in pulmonary artery blood temperature are transiently increased in many patients after CPB, and that this increased “thermal noise” may cause significant errors in TDCO measurements.

Does the duration of cardiopulmonary bypass or aortic cross-clamp, in the absence of blood and/or blood product administration, influence the IL-6 response to cardiac surgery?

Acute normovolemic hemodilution (ANH), in which blood for autologous use is collected immediately before the onset of surgical blood loss, is a recommended autologous blood procurement technique for blood conservation. Both crystalloid and colloid replacement fluids have been used to maintain normovolemia during ANH, but few data are available to justify the use of a particular replacement fluid. Therefore, we designed a prospective, randomized study to determine if the replacement fluid choice affects various coagulation variables and perioperative blood loss. Forty adult patients, ASA physical status 1-3, scheduled for ANH during radical prostatectomy were randomly assigned to one of four replacement fluid groups: (a) Ringers lactate, (b) 5% albumin, (c) 6% dextran 70 (DEX), or (d) 6% hetastarch (HES). After the induction of a standardized general anesthetic, all patients underwent ANH to a final hemoglobin level of 9 g/dL. Complete blood count, prothrombin time, partial thromboplastin time, fibrinogen, factors V and VIII levels, bleeding time, and thromboelastography (TEG measurements were obtained at similar time points in the procedure. When compared with baseline, activated partial thromboplastin time decreased and factor VIII levels increased in the postanesthesia care unit in both the Ringers lactate and 5% albumin groups. The DEX and HES groups demonstrated a decrease in TEG maximum amplitude between preoperative and postanesthesia care unit measurements and TEG alpha (angle) was decreased from baseline in the DEX group. The changes in factor VIII, activated partial thromboplastin time, and TEG measurements indicate that HES and DEX may attenuate the hypercoagulability related to surgery.