J G Ramsay

University of Michigan, Ann Arbor, MI, United States

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Publications (41)167.07 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Although potassium is critical for normal electrophysiology, the association between abnormal preoperative serum potassium level and perioperative adverse events such as arrhythmias has not been examined rigorously. To determine the prevalence of abnormal preoperative serum potassium levels and whether such abnormal levels are associated with adverse perioperative events. Prospective, observational, case-control study of data collected from 24 diverse US medical centers in a 2-year period from September 1, 1991, to September 1, 1993. A total of 2402 patients (mean [SD] age, 65.1 [10.3] years; 24% female) undergoing elective coronary artery bypass grafting who were not enrolled in another protocol. The study population was identified using systematic sampling of every nth patient, in which n was based on expected total number of procedures at that center during the study period. Intraoperative and postoperative arrhythmias, the need for cardiopulmonary resuscitation (CPR), cardiac death, and death due to any cause prior to discharge, by preoperative serum potassium level. Perioperative arrhythmias occurred in 1290 (53.7%) of 2402 patients, with 238 patients (10.7%) having intraoperative arrhythmias, 329 (13.7%) having postoperative nonatrial arrhythmias, and 865 (36%) having postoperative atrial flutter or fibrillation. The incidence of adverse outcomes was 3.6% for death, 2.0% for cardiac death, and 3.5% for CPR. Serum potassium level less than 3.5 mmol/L was a predictor of serious perioperative arrhythmia (odds ratio [OR], 2.2; 95% confidence interval [CI], 1.2-4.0), intraoperative arrhythmia (OR, 2.0; 95% CI, 1.0-3.6), and postoperative atrial fibrillation/flutter (OR, 1.7; 95% CI, 1.0-2.7), and these relationships were unchanged after adjusting for confounders. The significant univariate association between increased need for CPR and serum potassium level less than 3.3 mmol/L (OR, 3.3; 95% CI, 1.2-9.5) and greater than 5.2 mmol/L (OR, 3.0; 95% CI, 1.1-8.7) became nonsignificant after adjusting for confounders. Perioperative arrhythmia and the need for CPR increased as preoperative serum potassium level decreased below 3.5 mmol/L. Although interventional trials are required to determine whether preoperative intervention mitigates these adverse associations, preoperative repletion is low cost and low risk, and our data suggest that screening and repletion be considered in patients scheduled for cardiac surgery.
    JAMA The Journal of the American Medical Association 07/1999; 281(23):2203-10. · 29.98 Impact Factor
  • J G Ramsay
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    ABSTRACT: Coronary artery disease (CAD) is common in the surgical population, with up to 50% of postoperative deaths due to cardiac events. Most of these events are ischemic, with some being exacerbations of underlying congestive heart failure (CHF). Recent data indicate that acute perioperative beta-adrenergic blockade can reduce ischemia and ischemic events. Postoperative monitoring should focus on myocardial ischemia, with preparation for rapid treatment using IV therapy. A few studies suggest that elderly patients with known CAD undergoing major procedures might benefit from perioperative treatment guided by information from a pulmonary artery catheter. Postoperative CHF, which is likely to present early after surgery, may need aggressive management with diuretics, vasodilators, and inotropic drugs. Mechanical ventilation should be considered. When the patient develops severe or refractory dysrhythmias, serum magnesium levels should be supplemented and consideration given to IV use of amiodarone. Postoperative hypertension is common and can precipitate ischemia, CHF, and arrhythmias as well as cause bleeding. Newer IV drugs are arterial specific and can lower BP in a smooth and predictable manner. All acute cardiac disorders can be precipitated or exacerbated by inadequate pain control, hypoxemia, and fluid or electrolyte disorders.
    Chest 06/1999; 115(5 Suppl):138S-144S. · 7.13 Impact Factor
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    ABSTRACT: Midazolam is commonly used for short-term postoperative sedation of patients undergoing cardiac surgery. The purpose of this multicenter study was to characterize the pharmacokinetics and intersubject variability of midazolam in patients undergoing coronary artery bypass grafting. With institutional review board approval, 90 consenting patients undergoing coronary artery bypass grafting were enrolled at three study centers. All subjects received sufentanil and midazolam via target-controlled infusions. After operation, midazolam was titrated to maintain deep sedation for at least 2 h. It was then titrated downward to decrease sedation for a minimum of 4 h more and was discontinued before tracheal extubation. Arterial blood samples were taken throughout the study and were assayed for midazolam and 1-hydroxymidazolam. Midazolam population pharmacokinetic parameters were estimated using NONMEM. Cross-validation was used to estimate the performance of the model. The pharmacokinetics of midazolam were best described by a simple three-compartment mammillary model. Typical pharmacokinetic parameters were V1 = 32.2 l, V2 = 53 l, V3 = 245 l, Cl1 = 0.43 l/min, Cl2 = 0.56 l/min, and Cl3 = 0.39 l/min. The calculated elimination half-life was 15 h. The median absolute prediction error was 25%, with a bias of 1.4%. The performance in the cross-validation was similar. Midazolam metabolites were clinically insignificant in all patients. The intersubject variability and predictability of the three-compartment pharmacokinetic model are similar to those of other intravenous anesthetic drugs. This multicenter study did not confirm previous studies of exceptionally large variability of midazolam pharmacokinetics when used for sedation in intensive care settings.
    Anesthesiology 01/1999; 89(6):1418-29. · 5.16 Impact Factor
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    ABSTRACT: Midazolam is used commonly for sedation in the surgical intensive care unit. A suboptimal dosing regimen may lead to relative overdosing, which could result in delayed extubation and increased cost. This multicenter trial characterized midazolam pharmacodynamics in patients recovering from coronary artery bypass grafting. Three centers enrolled 90 patients undergoing coronary artery bypass grafting. All patients received sufentanil and midazolam via target-controlled infusion. After surgery, midazolam was titrated to a Ramsay sedation score of 5 for 2 h and then decreased to maintain a sedation score of 3 or 4 for at least another 4 h. Pharmacodynamic parameters were derived using NONMEM. The model was cross-validated to test performance. The probability of a given level of sedation was related to the midazolam concentration by this equation: P(Sedation > or = ss) = Cn/(Cn + C(50,ss)n), where ss is the sedation score, C is the sum of the midazolam concentration and a term reflecting the dissipating effect of anesthesia: C = [midazolam] + theta x e(-Kt), where theta = 256 ng/ml and K = 0.19 h(-1). C(50,ss) values for Ramsay scores of 2 to 6 were 5.7, 71, 171, 260, and 659 ng/ml, respectively. The model predicted 57% of the data points correctly and 88% within one sedation score. Despite previous reports of high interindividual variability in midazolam pharmacodynamics in patients in the surgical intensive care unit, these cross-validation results suggest that, when midazolam is administered using a target-controlled infusion device, the level of sedation can be predicted within 1 sedation score in 88% of patients based on the target midazolam concentration and the time since the conclusion of the anesthetic.
    Anesthesiology 01/1999; 89(6):1430-43. · 5.16 Impact Factor
  • J M Erb, J G Ramsay
    Anesthesiology 09/1998; 89(2):543-4. · 5.16 Impact Factor
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    ABSTRACT: Acute changes in renal function after elective coronary bypass surgery are incompletely characterized and represent a challenging clinical problem. To determine the incidence and characteristics of postoperative renal dysfunction and failure, perioperative predictors of dysfunction, and the effect of renal dysfunction and failure on in-hospital resource utilization and patient disposition after discharge. Prospective, observational, multicenter study. 24 university hospitals. 2222 patients having myocardial revascularization with or without concurrent valvular surgery. Prospective histories, physical examinations, and electrocardiographic and laboratory studies. The main outcome measure was renal dysfunction (defined as a postoperative serum creatinine level > or = 177 mumol/L with a preoperative-to-postoperative increase > or = 62 mumol/L). 171 patients (7.7%) had postoperative renal dysfunction; 30 of these (1.4% overall) had oliguric renal failure that required dialysis. In-hospital mortality, length of stay in the intensive care unit, and hospitalization were significantly increased in patients who had renal failure and those who had renal dysfunction compared with those who had neither (mortality: 63%, 19%, and 0.9%; intensive care unit stay: 14.9 days, 6.5 days, and 3.1 days; hospitalization: 28.8 days, 18.2 days, and 10.6 days, respectively). Patients with renal dysfunction were three times as likely to be discharged to an extended-care facility. Multivariable analysis identified five independent preoperative predictors of renal dysfunction: age 70 to 79 years (relative risk [RR], 1.6 [95% CI, 1.1 to 2.3]) or age 80 to 95 years (RR, 3.5 [CI, 1.9 to 6.3]); congestive heart failure (RR, 1.8 [CI, 1.3 to 2.6]); previous myocardial revascularization (RR, 1.8 [CI, 1.2 to 2.7]); type 1 diabetes mellitus (RR, 1.8 [CI, 1.1 to 3.0]) or preoperative serum glucose levels exceeding 16.6 mmol/L (RR, 3.7 [CI, 1.7 to 7.8]); and preoperative serum creatinine levels of 124 to 177 mumol/L (RR, 2.3 [CI, 1.6 to 3.4]). Independent perioperative factors that exacerbated risk were cardiopulmonary bypass lasting 3 or mor hours and three measures of ventricular dysfunction. Many patients having elective myocardial revascularization develop postoperative renal dysfunction and failure, which are associated with prolonged intensive care unit and hospital stays, significant increases in mortality, and greater need for specialized long-term care. Resources should be redirected to mitigate renal injury in high-risk patients.
    Annals of internal medicine 02/1998; 128(3):194-203. · 13.98 Impact Factor
  • J Ramsay
    Advances in wound care: the journal for prevention and healing 01/1998; 11(3 Suppl):5-6.
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    ABSTRACT: Electrocardiographic (ECG) changes during coronary artery bypass graft surgery have not been described in detail in a large multicenter population. The authors describe these ECG changes and evaluate them, along with demographic and clinical characteristics and intraoperative hemodynamic alterations, as predictors of myocardial infarction (MI) as defined by two sets of criteria. Data from 566 patients at 20 clinical sites, collected as part of a clinical trial to evaluate the efficacy of acadesine for reducing MI, were analyzed at core laboratories. Perioperative ECG changes were identified using continuous three-lead Holter ECG. Systolic blood pressure, diastolic blood pressure, and heart rate were recorded each minute during operation. The occurrence of MI by Q wave or myocardial fraction of creatine kinase (CK-MB) or autopsy criteria, and by (Q wave and CK-MB) or autopsy criteria was determined. During perioperative Holter monitoring, episodes of ST segment deviation, major cardiac conduction changes > or = 30 min, or use of ventricular pacing > or = 30 min occurred in 58% patients, primarily in the first 8 h after release of aortic occlusion. Of the 25% patients who met the Q wave or CK-MB or autopsy criteria for MI, 19% had increased CK-MB as well as ECG changes. (Q wave and CK-MB) or autopsy criteria for MI were met by 4% of patients. The CK-MB concentration generally peaked by 16 h after release of aortic occlusion. In patients with (n = 187) and without a perioperative episode of ST segment deviation, the incidence of MI was 36% and 19%, respectively (P < 0.01), by Q wave or CK-MB or autopsy criteria, and 6% and 3%, respectively (P = 0.055), by (Q wave and CK-MB) or autopsy criteria. Multiple logistic regression analysis showed that intraoperative ST segment deviation, intraventricular conduction defect, left bundle branch block, duration of hypotension (systolic blood pressure < 90 mmHg) after cardiopulmonary bypass, and duration of cardiopulmonary bypass are independent predictors of Q wave or CK-MB or autopsy MI. The independent predictors of (Q wave and CK-MB) or autopsy MI are intraoperative ST segment deviation and duration of aortic occlusion. Major ECG changes occurred in 58% of patients during coronary artery bypass graft surgery, primarily within 8 h after release of aortic occlusion. Multicenter data collection revealed a substantial variation in the incidence of MI and an overall incidence of up to 25%, with most MI occurring within 16 h after release of aortic occlusion. Intraoperative monitoring of ECG and hemodynamics has incremental value for predicting MI.
    Anesthesiology 04/1997; 86(3):576-91. · 5.16 Impact Factor
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    ABSTRACT: Background: Electrocardiographic (ECG) changes during coronary artery bypass graft surgery have not been described in detail in a large multicenter population. The authors describe these ECG changes and evaluate them, along with demographic and clinical characteristics and intraoperative hemodynamic alterations, as predictors of myocardial infarction (MI) as defined by two sets of criteria.
    Anesthesiology 02/1997; 86(3):576–591. · 5.16 Impact Factor
  • Source
    J Ramsay
    Canadian Journal of Anaesthesia 06/1996; 43(5 Pt 2):R99-107. · 2.13 Impact Factor
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    ABSTRACT: Propofol sedation offers advantages for titration and rapid emergence in the critically ill patient, but concern for adverse hemodynamic effects potentially limits its use in these patients. The current study compares the cardiovascular effects of sedation with propofol versus midazolam during the first 12 h after coronary revascularization. Three hundred fifty-one patients undergoing coronary revascularization were anesthetized using a standardized sufentanil/midazolam regimen, and assigned randomly to 12 h of sedation with either propofol or midazolam while tracheally intubated. The incidence and characteristics of hemodynamic episodes, defined as heart rate less than 60 or greater than 100 beats/min or systolic blood pressure greater than 140 or less than 90 mmHg, were determined using data electronically recorded at 1-min intervals. The presence of myocardial ischemia was determined using continuous three-channel Holter electrocardiography (ECG) and of myocardial infarctions (MI) using 12-lead ECG (Q wave MI, Minnesota Code) or creatine kinase isoenzymes (CK-MB) analysis (non-Q wave MI, peak CK-MB > 70 ng/ml, or CK-MB > 70 IU/I). Ninety-three percent of patients in both treatment groups had at least one hemodynamic episode during the period of postoperative sedation. Propofol sedation resulted in a 17% lower incidence of tachycardia (58% vs. 70%, propofol vs. midazolam; P = 0.04), a 28% lower incidence of hypertension (39% vs. 54%; P = 0.02), and a greater incidence of hypotension (68% vs. 51%; P = 0.01). Despite these hemodynamic effects, the incidence of myocardial ischemia did not differ between treatment groups (12% propofol vs. 13% midazolam; P = 0.66), nor did its severity, as measured by ischemic minutes per hour monitored (8.7 +/- 5.8 vs. 6.2 +/- 4.6 min/h, propofol vs. midazolam; P = 0.19) or ischemic area under the curve (6.8 +/- 4.0 vs. 5.3 +/- 4.2; P = 0.37). The incidence of cardiac death (one per group), Q wave MI (propofol, n = 7; midazolam, n = 3; P = 0.27), or non Q wave MI (propofol, n = 16; midazolam, n = 18; P = 0.81) did not differ between treatment groups. Hemodynamic episodes occur frequently in the first 12 h after coronary revascularization. Compared with a standard sedation regimen (midazolam), propofol sedation appears to modulate postoperative hemodynamic responses by reducing the incidence and severity of tachycardia and hypertension and increasing the incidence of hypotension. Both sedation regimens appear similarly safe with respect to myocardial ischemia. These findings indicate that propofol infusion provides effective sedation without deleterious hemodynamic effects in patients recovering from cardiac surgery.
    Anesthesiology 06/1996; 84(6):1350-60. · 5.16 Impact Factor
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    ABSTRACT: Background: Propofol sedation offers advantages for titration and rapid emergence in the critically ill patient, but concern for adverse hemodynamic effects potentially limits its use in these patients. The current study compares the cardiovascular effects of sedation with propofol versus midazolam during the first 12 h after coronary revascularization.
    Anesthesiology 05/1996; 84(6):1350–1360. · 5.16 Impact Factor
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    ABSTRACT: This study was designed to assess, in a prospective, randomized, blinded fashion, the hemodynamic effects of different anesthetics used in the prebypass period during coronary artery bypass grafting (CABG) and the effect on incidence of ischemia. Seventy-five patients were randomly assigned to receive sufentanil increments, isoflurane, or enflurane after a standard premedication and anesthetic induction with sufentanil 5 micrograms/kg. Myocardial ischemia was monitored intraoperatively by the anesthesiologist with electrocardiogram (ECG) leads V5(CB5) and II, and by a Holter monitor of the same leads from which recordings were analyzed postoperatively by a cardiologist. A continuous recording of the blood pressure was analyzed to determine the duration of hypertensive responses. Arterial blood pressure control was best in the patients supplemented with anesthetic vapors; patients receiving beta-adrenergic blockers or those receiving isoflurane were less likely to require treatment for tachycardia. All episodes of myocardial ischemia occurred within 5 min of induction-intubation and were diagnosed more frequently by the anesthesiologist than on the Holter monitor (29% vs 9%), with no difference between groups. There were five perioperative myocardial infarctions with no difference between groups. After anesthetic induction with sufentanil 5 micrograms/kg, isoflurane or enflurane given during CABG provides better hemodynamic control than increments of sufentanil and is associated with a similar incidence of prebypass ischemia and perioperative infarction.
    Anesthesia & Analgesia 06/1994; 78(5):867-75. · 3.30 Impact Factor
  • Anesthesiology 01/1994; 81. · 5.16 Impact Factor
  • J. A. Wahr, J. G. Ramsay, U. Jain
    Anesthesiology 01/1994; 81. · 5.16 Impact Factor
  • J. G. Ramsay, U. Jain, A. Aggarwal, C. T. Mora
    Anesthesiology 01/1994; 81. · 5.16 Impact Factor
  • Source
    James G. Ramsay
    Canadian Journal of Anaesthesia 02/1993; 40(2):98-102. · 2.13 Impact Factor
  • James G. Ramsay
    Canadian Journal of Anaesthesia-journal Canadien D Anesthesie - CAN J ANAESTH. 01/1993; 40(2):98-102.
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    ABSTRACT: To validate the Reynolds Tracker II Holter system using newly described lead positions during both upright treadmill exercise and in the recumbent position following exercise. The specific lead positions HL1 and HL2 were chosen to detect anterior and postero-inferior myocardial ischemia, respectively, without interfering with the surgical field in the hypothetical situation of open-heart surgery. Similar lead positions have previously been used to monitor myocardial ischemia during induction of anesthesia, but have never been validated by comparison with 12-lead modified electrocardiogram (ECG) recording. To validate the authors' 'chosen' Holter lead positions (HL1 and HL2), both at the fifth intercostal space just lateral to the midclavicular line and on the back, 1.5 cm to the left of the vertebral column, respectively) 49 candidates for routine treadmill exercise testing underwent a simultaneous Holter monitor recording using the described lead positions. The Holter ECG recordings were separately analyzed by two physicians unaware of patients' identity. Using the modified 12-lead ECG as the 'gold standard', the sensitivity of Holter for detecting ischemia (defined as 0.1 mV or ST depression lasting at least 60 s) was 77 and 83%, and its specificity was 100 and 92%, respectively, for observers 1 and 2. Most episodes of myocardial ischemia were detected by the modified lead V5 for the 12-lead ECG and by HL1 for the Holter recording. Using the Holter Tracker II system and the chosen lead positions, it was possible to detect successfully most episodes of exercise-induced myocardial ischemia. Holter monitoring might be useful in detecting perioperative myocardial ischemia.
    The Canadian journal of cardiology 07/1992; 8(5):465-8. · 3.12 Impact Factor
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    ABSTRACT: One hundred patients were randomly allocated to receive saline or amrinone, 0.75 mg.kg-1, ten minutes before separation from cardiopulmonary bypass (CPB) after elective coronary artery bypass grafting, in order to determine the effects of this agent on haemodynamic variables and O2 utilization. Anaesthesia and CPB were managed in a standard fashion. Before induction of anaesthesia, at pericardiotomy, then at 1, 10, 20 and 30 min after CPB, haemodynamic profiles, haematocrit, and O2 saturation of arterial and mixed venous blood were measured. Incremental doses of ephedrine or phenylephrine, or an infusion of norepinephrine with phentolamine were administered when required. The groups were demographically similar and surgical variables were also similar. Haemodynamic measurements were similar between groups at all times; however, a higher dose of phenylephrine was given immediately before weaning from CPB in the amrinone group, and more patients in this group received phenylephrine in the first 30 min after CPB. Mixed venous saturation (SvO2) was higher in the amrinone patients at all times after CPB, leading to lower calculated oxygen consumption (VO2) (P less than 0.05). Insufficient dosage may explain the lack of haemodynamic effect, while possible reasons for the higher SvO2 and lower VO2 are either reduced whole body VO2 or peripheral shunting.
    Canadian Journal of Anaesthesia 05/1992; 39(4):342-8. · 2.13 Impact Factor

Publication Stats

709 Citations
167.07 Total Impact Points


  • 1996–1999
    • University of Michigan
      • Department of Anesthesiology
      Ann Arbor, MI, United States
  • 1991–1999
    • Emory University
      • Department of Anesthesiology
      Atlanta, GA, United States
  • 1998
    • Stanford University
      • Department of Anesthesia
      Palo Alto, CA, United States
  • 1997
    • University of California, San Francisco
      • Department of Anesthesia and Perioperative Care
      San Francisco, CA, United States
  • 1985–1994
    • McGill University
      • Department of Anesthesia
      Montréal, Quebec, Canada
  • 1988
    • University of Oxford
      • Nuffield Division of Anaesthetics (NDA)
      Oxford, ENG, United Kingdom