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C D Mazer

Publications and source records attributed to C D Mazer.

At least 19 recordsLinked to original sources
PubMed2006

Beta2 adrenergic antagonist inhibits cerebral cortical oxygen delivery after severe haemodilution in rats.

BACKGROUND: Haemodilution has been associated with neurological morbidity in surgical patients. This study tests the hypothesis that inhibition of cerebral vasodilatation by systemic beta2 adrenergic blockade would impair cerebral oxygen delivery leading to tissue hypoxia in severely haemodiluted rats. METHODS: Under general anaesthesia, cerebral tissue probes were placed to measure temperature, regional cerebral blood flow (rCBF) and tissue oxygen tension (P(Br)O2) in the parietal cerebral cortex or hippocampus. Baseline measurements were established before and after systemic administration of either a beta2 antagonist (10 mg kg(-1) i.v., ICI 118, 551) or saline vehicle. Acute haemodilution was then performed by simultaneously exchanging 50% of the estimated blood volume (30 ml kg(-1)) with pentastarch. Arterial blood gases (ABGs), haemoglobin concentration (co-oximetry), mean arterial blood pressure (MAP) and heart rate (HR) were also measured. Data were analysed using a two-way anova and post hoc Tukey's test [mean (sd)]. RESULTS: Haemodilution reduced the haemoglobin concentration comparably in all groups [71 (9) g litre(-1)]. There were no differences in ABGs, co-oximetry, HR and MAP measurements between control and beta2 blocked rats, either before or 60 min after drug or vehicle administration. In rats treated with the beta2 antagonist there was a significant reduction in parietal cerebral cortical temperature, regional blood flow and tissue oxygen tension, relative to control rats, 60 min after haemodilution (P<0.05 for each). These differences were not observed when probes were placed in the hippocampus. CONCLUSION: Systemic beta2 adrenergic blockade inhibited the compensatory increase in parietal cerebral cortical oxygen delivery after haemodilution thereby reducing cerebral cortical tissue oxygen tension.

Adrenergic beta-2 Receptor Antagonists↗
PubMed2004

A phase II dose-response study of hemoglobin raffimer (Hemolink) in elective coronary artery bypass surgery.

BACKGROUND: We performed this study to determine the dose-response of hemoglobin raffimer administered in conjunction with intraoperative autologous donation in patients undergoing coronary artery bypass grafting surgery. A secondary objective was to evaluate hemoglobin raffimer for reducing the incidence of allogeneic red blood cell transfusions. METHODS: This was a phase II, single-blind, multicenter, placebo-controlled, open-label study. Patients undergoing coronary artery bypass grafting with cardiopulmonary bypass and intraoperative autologous donation were randomized to receive a single dose of hemoglobin raffimer or control (10% pentastarch). Patients were sequentially enrolled in a dose block of 250, 500, 750, and 1000 mL. RESULTS: Sixty patients received hemoglobin raffimer (n = 30) or control (n = 30). Hemoglobin raffimer was well tolerated. Most (98%) adverse events were mild or moderate in severity. There was an expected dose-dependent increase in the incidence of blood pressure increases and jaundice in hemoglobin raffimer-treated patients. In a dose-pooled analysis of hemoglobin raffimer versus control, increased blood pressure (43% vs 17%), nausea (37% vs 33%), and atrial fibrillation (37% vs 17%) were the most frequently reported adverse events. All serious adverse events were considered unrelated or unlikely to be related to study drug. No hemoglobin raffimer-treated patient required an intraoperative allogeneic red blood cell transfusion, compared with 5 (17%) pentastarch-treated patients (P =.052). This advantage of hemoglobin raffimer was maintained at 24 hours after surgery (7% vs 37%; P =.010) and up to 5 days after surgery (10% vs 47%; P =.0034). CONCLUSIONS: Hemoglobin raffimer was not associated with any serious adverse events in patients undergoing primary coronary artery bypass grafting with cardiopulmonary bypass and intraoperative autologous donation in a dose-response study up to 1000 mL. Hemoglobin raffimer was effective in facilitating decreased exposure or avoidance of allogeneic red blood cell transfusions when used in conjunction with intraoperative autologous donation.

Adult↗
PubMed2001

Effect of NaHCO3 on cardiac energy metabolism and contractile function during hypoxemia.

OBJECTIVE: To examine the impact of administration of NaHCO3 on contractility and energy metabolism of the myocardium during hypoxemia. METHODS: Regional myocardial hypoxia was induced in the left anterior descending (LAD) artery myocardium in anesthetized, open-chest dogs, using a perfusion circuit between the right atrium and the LAD artery, and a membrane oxygenator. The rate of flow in LAD artery was maintained constant with the use of a roller pump. During hypoxia, eight dogs were administered isotonic NaHCO3 in the circuit and six other dogs received equimolar NaCl. Myocardial contractile function was assessed using sonomicrometry for measurement of percentage of systolic shortening and preload recruitable stroke work. Oxygen consumption and the rate of appearance of lactate were measured. Clamp-frozen tissue samples were obtained at the end of the experiment from the hypoxic LAD myocardium and the nonhypoxic circumflex myocardium for measurement of tissue lactate level. RESULTS: During hypoxia, there was a significant decrease in oxygen consumption by the LAD myocardium (35 +/- 7 micromol/min in the NaCl group and 40 +/- 7 micromol/min in the NaHCO3 group during hypoxia vs. 131 +/- 11 micromol/min during aerobic perfusion). There was also a significant decrease in myocardial contractility as measured by percentage of systolic shortening (14 +/- 3% to -8 +/- 3%); NaHCO3 infusion during hypoxia did not improve myocardial contractility (-7 +/- 2%). Similar results were obtained with measurements of preload recruitable stroke work. The rate of production of lactate during hypoxia was substantially lower than expected, based on the calculated oxygen deficit, and was not significantly increased by the administration of NaHCO3 (33 +/- 9 micromol/min in the NaCl group and 51 +/- 5 micromol/min in the NaHCO3 group). Tissue lactate was not statistically different in the hypoxic myocardium supplied by the LAD artery and the nonhypoxic myocardium supplied by the circumflex artery in either group. CONCLUSION: The response of the myocardium to hypoxia is to decrease its mechanical work and metabolic demand. The infusion of NaHCO3 did not enhance myocardial contractile function or flux in glycolysis during hypoxia. We speculate that this diminished mechanical work and metabolic demand may represent an adaptive response to preserve cellular integrity until oxygen delivery is restored.

Acidosis, Lactic↗
PubMed2000

Distribution of pulmonary blood flow in the perfluorocarbon-filled lung.

OBJECTIVE: Partial liquid ventilation (PLV) improves gas exchange in animal studies of lung injury. Perfluorocarbons (PFCs) are heavy liquids and are therefore preferentially delivered to the most dependent areas of lung. We hypothesised that improved oxygenation during PLV might be the consequence of a redistribution of pulmonary blood flow away from poorly ventilated, dependent alveoli, leading to improved ventilation/perfusion (V/Q) matching. This study investigated whether partially filling the lung with PFC would result in a redistribution of pulmonary blood flow. DESIGN: Prospective experimental study. SETTING: Hospital research institute laboratory. PARTICIPANTS: Six anaesthetised pigs without lung injury. INTERVENTIONS: Animals were anaesthetised and ventilated (gas tidal volume 12 ml/kg, PEEP 5, FIO2 1.0, rate 16). Whilst the pigs were maintained in the supine position, regional pulmonary blood flow was measured during conventional gas ventilation and repeated during PLV. Flow to regions of lung was determined by injection of radioactive microspheres (Co(57), Sn(113), Sc(46)). Measurements were performed with ventilation held at end-expiratory pressure and, in two PLV animals only, repeated with ventilation held at peak inspiratory pressure. RESULTS: During conventional gas ventilation, blood flow followed a linear distribution with the highest flow to the most dependent lung. In the lung partially filled with PFC a diversion of blood flow away from the most dependent lung was seen (p = 0.007), resulting in a more uniform distribution of flow down the lung (p = 0.006). Linear regression analysis (r2 = 0.75) also confirmed a difference in distribution pattern. On applying an inspiratory hold to the liquid-containing lung, blood flow was redistributed back towards the dependent lung. CONCLUSIONS: Partially filling the lung with PFC results in a redistribution of pulmonary blood flow away from the dependent region of the lung. During PLV a different blood flow distribution may be seen between inspiration and expiration. The clinical significance of these findings has yet to be determined.

Animals↗
PubMed2000

The use of transesophageal echocardiography for preload assessment in critically ill patients.

UNLABELLED: IV volume is often administered to patients in an intensive care unit (ICU) to improve cardiovascular function. We investigated the relationship between stroke volume (SV) and left ventricular (LV) size by using transesophageal echocardiography (TEE) in a population of 20 ICU patients and 21 postoperative cardiac surgical patients. We also examined whether LV end diastolic area (EDA), by TEE, could identify patients who increased SV by 20% or more (responders) after 500 mL of pentastarch administration. There was only a modest relationship (r = 0.60) between the EDA and the SV in all patients. No relationship could be found between the pulmonary capillary wedge pressure (PCWP) and the EDA in all patients. Both responder and nonresponder PCWP increased significantly after volume administration. Only responder EDA increased significantly after volume administration. Responders had significantly lower EDA (15.3 +/- 5.4 cm(2)) and PCWP (12.2 +/- 2.2 mm Hg) when compared with nonresponders (20.2 +/- 4.8 cm(2)) and 15.9 +/- 3.1 mm Hg, respectively). Few ICU patients and only those with a small EDA responded to volume administration. It was not possible to identify an overall optimal LV EDA below which most patients demonstrate volume-recruitable increases in SV. IMPLICATIONS: In a ventilated intensive care unit and cardiac surgical population, transesophageal echocardiography and pulmonary artery catheter are sensitive in detecting changes in preload after volume administration. Few patients demonstrate volume-recruitable increases in stroke volume when compared to cardiac surgical patients. It is not possible to establish an overall end diastolic threshold below which a large proportion of ventilated patients respond to volume administration.

Blood Volume↗
PubMed2000

Death in two Canadian intensive care units: institutional difference and changes over time.

OBJECTIVE: To study and compare the mode of death in two different institutions' intensive care units (ICUs) for the two time periods, 1988 and 1993. DESIGN: Retrospective chart review. SETTING: Medical/surgical/trauma ICUs in two tertiary care teaching hospitals. PATIENTS: Patients dying in the medical/surgical/trauma ICUs between January 1, 1988 and December 31, 1988; and January 1, 1993 and December 31, 1993. Data collection included demographics, origin of admission, date of ICU admission, date of death, Acute Physiology and Chronic Health Evaluation (APACHE) III diagnostic categories, APACHE II physiologic variables, organ system failures present at the time of admission and 24 hrs before death, and mode of dying. APACHE II scores and mortality risk were calculated. Data analysis included a multiple analysis of variance to assess overall effect, with subsequent analyses of variance to assess the effect of institution and year on each individual dependent variable. All results are reported as mean +/- SEM values. RESULTS: A total of 439 charts were reviewed. Gender, age, and origin of admission were not different between the 2 yrs or the two institutions. Mean APACHE II scores and organ system failures were lower at Hospital A in 1998 vs. Hospital B, as was predicted mortality. These factors increased at Hospital A in 1993 and were similar to those at Hospital B. Withdrawal of support was much more common in 1993 than 1988 at both institutions (43% at Hospital A and 46% at Hospital B in 1988 vs. 66% at A and 80% at B in 1993), increasing to a greater extent in 1993 at Hospital B (p<.05). Length of stay in the ICU was significantly longer at Hospital A than at Hospital B in 1988 (9.4+/-1.4 vs. 4.3+/-0.6 days; p<.05) and in 1993 (8.2+/-2.9 vs. 3.8+/-0.5 days; p < .05). CONCLUSIONS: There has been an increase in withdrawal of life support, in recent years, at both the institutions studied. Differences exist between institutions with respect to end-of-life decisions in the ICU. These differences are likely representative of widely prevalent regional differences and are the result of many factors.

APACHE↗
PubMed1998

Phase 2 studies of adenosine cardioplegia.

BACKGROUND: Laboratory evidence supports the use of adenosine-supplemented cardioplegia. An initial phase 1 dose-ranging clinical evaluation demonstrated that an adenosine concentration of 15 mumol/L could be safely administered with warm blood cardioplegia and suggested that phase 2 studies were warranted. METHODS AND RESULTS: Two separate double-blind, randomized, placebo-controlled trials were performed in patients undergoing primary, isolated, nonemergent coronary artery bypass graft surgery. Patients were randomized to receive adenosine 15 mumol/L versus placebo in the first study (n = 200) and adenosine 50 or 100 mumol/L versus placebo in the second study (n = 128). Adenosine was infused with both initial and final doses of warm antegrade blood cardioplegia. The data from the 2 trials were combined using the methods of Mantel and Haenszel, and the results of the meta-analysis are presented as the relative risk with their associated 95% confidence intervals (CI). The different study groups were comparable with respect to all preoperative clinical characteristics, angiographic findings, and intraoperative variables. In both trials 1 and 2, no differences were found between groups in the incidence of the individual primary or secondary outcomes. Similarly, when both studies were combined, there was no significant evidence of any consistent treatment benefit (primary: death: relative risk [RR] = 1.02, 95% CI = 0.06, 16.6; myocardial infarction by CK-MB: RR = 0.84, CI = 0.54, 1.31; low output syndrome: RR = 1.38, CI = 0.29, 6.42; any of the above: RR = 0.98, CI = 0.78, 1.25; secondary: Q-wave myocardial infarction: RR = 1.30, CI = 0.41, 4.13; myocardial infarction by troponin T: RR = 0.7, CI = 0.40, 1.21; inotrope requirement: RR = 0.9, CI = 0.46, 1.79; intra-aortic balloon pump requirement: RR = 0.6, CI = 0.07, 4.81; P > 0.20). CONCLUSIONS: Despite promising experimental data, adenosine supplementation of warm blood cardioplegia did not demonstrate any statistically significant benefit in patients undergoing elective coronary artery bypass graft surgery. Although sample sizes were relatively small, based on our interim analyses, it is unlikely that increased patient enrollment would reveal any substantive clinical differences between groups.

Adenosine↗
PubMed1998

Evaluation of a ventilation strategy to prevent barotrauma in patients at high risk for acute respiratory distress syndrome. Pressure- and Volume-Limited Ventilation Strategy Group.

BACKGROUND: A strategy of mechanical ventilation that limits airway pressure and tidal volume while permitting hypercapnia has been recommended for patients with the acute respiratory distress syndrome. The goal is to reduce lung injury due to overdistention. However, the efficacy of this approach has not been established. METHODS: Within 24 hours of intubation, patients at high risk for the acute respiratory distress syndrome were randomly assigned to either pressure- and volume-limited ventilation (limited-ventilation group), with the peak inspiratory pressure maintained at 30 cm of water or less and the tidal volume at 8 ml per kilogram of body weight or less, or to conventional ventilation (control group), with the peak inspiratory pressure allowed to rise as high as 50 cm of water and the tidal volume at 10 to 15 ml per kilogram. All other ventilatory variables were similar in the two groups. RESULTS: A total of 120 patients with similar clinical features underwent randomization (60 in each group). The patients in the limited-ventilation and control groups were exposed to different mean (+/-SD) tidal volumes (7.2+/-0.8 vs. 10.8+/-1.0 ml per kilogram, respectively; P<0.001) and peak inspiratory pressures (23.6+/-5.8 vs. 34.0+/-11.0 cm of water, P<0.001). Mortality was 50 percent in the limited-ventilation group and 47 percent in the control group (relative risk, 1.07; 95 percent confidence interval, 0.72 to 1.57; P=0.72). In the limited-ventilation group, permissive hypercapnia (arterial carbon dioxide tension, >50 mm Hg) was more common (52 percent vs. 28 percent, P=0.009), more marked (54.4+/-18.8 vs. 45.7+/-9.8 mm Hg, P=0.002), and more prolonged (146+/-265 vs. 25+/-22 hours, P=0.017) than in the control group. The incidence of barotrauma, the highest multiple-organ-dysfunction score, and the number of episodes of organ failure were similar in the two groups; however, the numbers of patients who required paralytic agents (23 vs. 13, P=0.05) and dialysis for renal failure (13 vs. 5, P= 0.04) were greater in the limited-ventilation group than in the control group. CONCLUSIONS: In patients at high risk for the acute respiratory distress syndrome, a strategy of mechanical ventilation that limits peak inspiratory pressure and tidal volume does not appear to reduce mortality and may increase morbidity.

Barotrauma↗
PubMed1998

Hyperglycemia during normothermic cardiopulmonary bypass: the role of the kidney.

BACKGROUND: Hyperglycemia commonly occurs during cardiopulmonary bypass. We studied the quantitative impact of glucose input and its renal excretion on hyperglycemia during cardiopulmonary bypass. METHODS: The quantity of glucose infused and metabolite and hormone concentrations in plasma, as well as oxygen consumption, carbon dioxide production, and renal glucose excretion, were determined before, during, and after cardiopulmonary bypass in 8 patients. RESULTS: Hyperglycemia (14 to 29 mmol/L) was accompanied by an increase in plasma insulin levels. The degree of hyperglycemia was directly related to the amount of glucose infused. The rate of oxygen consumption did not decrease and the rate of urea appearance (gluconeogenesis) did not rise. Despite a very high filtered load of glucose, there was very little glucosuria, indicating a markedly enhanced renal absorption of glucose. CONCLUSIONS: Hormonal and metabolic factors permit the development of hyperglycemia during cardiopulmonary bypass but its severity depends on the quantity of glucose infused and, what appears to be a new finding, a markedly enhanced renal reabsorption of filtered glucose. Thus the kidney plays an important role in the development of severe hyperglycemia during cardiopulmonary bypass.

Absorption↗
PubMed1998

Effect of aortic cannula characteristics and blood velocity on transcranial doppler-detected microemboli during cardiopulmonary bypass.

OBJECTIVES: Cerebral microemboli are responsible to a large extent for the neuropsychiatric deficits after cardiac surgery. Differences in cannula size during cardiopulmonary bypass (CPB) will result in different velocities of blood exiting the aortic cannula. This study determined whether the number of transcranial Doppler (TCD)-detected emboli in the middle cerebral artery (MCA) during CPB correlated with blood speed or the direction of flow as determined by the shape of the aortic cannula. DESIGN: Patients were studied prospectively for evidence of TCD-detected emboli. If patients met the inclusion criteria, the choice of cannula was determined by surgical preference. SETTING: All studies were conducted at a single tertiary care academic cardiac surgery hospital by a single observer. PARTICIPANTS: Thirty-two patients undergoing first-time elective aortocoronary bypass surgery who were free of neurologic dysfunction or peripheral vascular disease and weighed 60 to 85 kg were studied. Patients who had other concurrent cardiac operations or who were in cardiogenic shock were excluded. INTERVENTIONS: Three aortic cannula types for elective aortocoronary bypass surgery were used: 24F curved (n = 19), 24F straight (n = 6), and 22F straight (n = 7), with internal diameters (IDs) of 7.2, 6.6, and 5.9 mm, respectively. TCD-detected emboli were identified in the MCA. MEASUREMENTS AND MAIN RESULTS: The rate of TCD-detected emboli (0.02 to 11.4 emboli per minute) was not related to the velocity of blood (46 to 77 cm/s) and was not affected by the choice of either a straight or curved aortic cannula. CONCLUSIONS: The choice of a straight or curved aortic cannula or of a 24F versus 22F cannula may not be important with respect to the number of cerebral microemboli.

Blood Flow Velocity↗
PubMed1997

Postoperative hyponatremia despite near-isotonic saline infusion: a phenomenon of desalination.

BACKGROUND: It is widely presumed that the development of postoperative hyponatremia (which may be severe) results from administration of hypotonic fluids while antidiuretic hormone is acting. OBJECTIVE: To show that hyponatremia would occur in patients 24 hours after surgery if only near-isotonic solutions are given and to evaluate the mechanisms responsible for hyponatremia in this setting. DESIGN: Prospective cohort study. SETTING: University medical center. PATIENTS: 22 women who were having uncomplicated gynecologic surgery with infusion of near-isotonic solutions only (sodium chloride, 154 mmol/L, or Ringer lactate [sodium, 130 mmol/L, and potassium, 4 mmol/L]). MEASUREMENTS: Plasma electrolyte levels were measured at the time of induction of anesthesia and 24 hours later. Data on the balance of water and electrolytes were obtained for the same 24-hours period. RESULTS: At the time of induction of anesthesia, the plasma sodium concentration was 140 +/- 1 mmol/L; 24 hours later, it decreased in 21 of 22 patients (mean decrease, 4.2 +/- 0.4 mmol/L [P < 0.001]; lowest level, 131 mmol/L in 2 patients). The urine remained hypertonic (peak sodium plus potassium concentration in urine, 294 +/- 9 mmol/L) in all patients for the first 16 hours after induction of anesthesia. CONCLUSIONS: Postoperative hyponatremia occurred within 24 hours of induction of anesthesia when only near-isotonic fluids were infused. Hyponatremia was generally caused by generation of electrolyte-free water during excretion of hypertonic urine-a desalination process. This electrolyte-free water was retained in the body because of the actions of antidiuretic hormone. If the pathophysiology of this hyponatremic state is understood, recommendations for its prevention and treatment can be deduced.

Adult↗
PubMed1997

Transcutaneous T wave shock: a universal method for ventricular fibrillation induction.

Our objective was to develop a universal noninvasive method for VF induction. ICD implantation requires VF induction. Conventional rapid ventricular stimulation may fail to induce VF. Some ICDs can deliver low energy shocks on the T wave to induce VF. We hypothesized that an external dual chamber pacemaker and an external defibrillator could be configured to allow reliable VF induction with any ICD system. A surface ECG signal was delivered to the atrial channel of an external dual chamber DDD pacemaker. The 'AV' delay was adjusted so that the ventricular output of the pacemaker was delivered to an external defibrillator synchronized to deliver 5-50 J. Twenty-six patients at ICD implant or follow-up had VF induced in native rhythm (sinus rhythm or atrial fibrillation), or during a ventricular pacing train (3-8 beats at cycle length 500-880 ms). VF was successfully induced in 14 of 25 (56%) patients in native rhythm; and in 16 of 17 (94%) patients during pacing (P = 0.013). VF induction success rate was 36% in native rhythm (31/86 attempts) and 88% during pacing (69/78 attempts) (P < 0.001). The 'R' to shock interval was 269 +/- 31 ms in native rhythm and 257 +/- 48 ms during pacing. Energy delivered from the external defibrillator was 19 +/- 3 J in native rhythm and 21 +/- 6 J during pacing. We concluded that VF induction by synchronizing a small external shock to the T wave is a fast, effective way to reliably ensure arrhythmia induction with any ICD at implant or follow-up. This method is more successful during pacing than in sinus rhythm.

Defibrillators, Implantable↗
PubMed1996

Ketamine concentrations during cardiopulmonary bypass.

PURPOSE: To describe the serum concentrations of ketamine following a clinically relevant dosing schedule during cardiopulmonary bypass (CPB). METHODS DESIGN: Prospective case series. SETTING: Tertiary care teaching hospital. PATIENTS: Six patients undergoing coronary artery bypass grafting and over age 60 yr. INTERVENTION: Following induction of anaesthesia each patient received a bolus of ketamine 2 mg.kg-1 followed by an infusion of 50 micrograms.kg-1.min-1 which ran continuously until two hours after bypass. MAIN OUTCOME MEASURES: Ketamine serum concentrations were measured at five minutes after bolus, immediately following aortic cannulation, 10 and 20 min on CPB, termination of CPB, termination of the drug infusion and three and six hours after infusion termination. RESULTS: At the time of aortic cannulation, ketamine concentrations were 3.11 +/- 0.81 micrograms.ml-1, these levels decreased by one third with the initiation of CPB. By the end of CPB the concentrations had returned to levels roughly equivalent to those observed at the time of aortic cannulation. Following cessation of the infusion, ketamine concentration declined in a log-linear fashion with a half-life averaging 2.12 hr. (range 1.38-3.09 hr). CONCLUSION: This dosage regimen maintained general anaesthetic concentrations of ketamine throughout the operative period. These levels should result in brain tissue concentrations in excess of those previously shown to be neuroprotective in animals. Thus we conclude that this infusion regimen would be reasonable to be use in order to assess the potential neuroprotective effects of ketamine in humans undergoing CPB.

Aged↗
PubMed1996

Can clinicians predict ICU length of stay following cardiac surgery?

PURPOSE: To determine whether a group of experienced clinicians can predict intensive care unit (ICU) length of stay (LOS) following cardiac surgery. METHODS: A cohort of 265 adult patients undergoing cardiac surgery at St. Michael's Hospital, Toronto, Ontario, between January 2, 1992, and June 26, 1992, were seen preoperatively by the clinicians participating in the study and ICU length of stay was predicted based on the clinicians' preoperative assessment and/or information recorded in the patient's chart. RESULTS: Five hundred and ten ICU length of stay predictions were obtained from a group of eight experienced clinicians (anaesthetists/intensivists, cardiologists, nurses). The clinicians predicted the exact ICU length of stay (in days) correctly 51.2% of the time and were within +/- 1 day 84.5% of the time. The clinicians correctly predicted short ICU stays (< or = 2 days) for 87.6% of the patients who had short ICU stays but only predicted long ICU stays (> 2 days) in 39.4% of the patients who had long ICU stays. CONCLUSIONS: Experienced clinicians can predict preoperatively with a considerable degree of accuracy patients who will have short ICU lengths of stay following cardiac surgery. However, many patients who had long ICU stays were not correctly identified preoperatively. Unidentified preoperative risk factors or unanticipated intraoperative/postoperative events may be causing these patients to have longer than expected ICU stays.

Adult↗
PubMed1996

Effect of alkali therapy with NaHCO3 or THAM on cardiac contractility.

We examined the impact of alkali therapy on myocardial contractility in a model of myocardial ischemia in dogs using direct measurements of myocardial contractile function. Myocardial ischemia in the left anterior descending (LAD) artery territory was induced using a perfusion circuit from the internal carotid artery to the LAD artery. Myocardial contractile function was assessed using sonomicrometry for measurement of percent systolic shortening (%SS), preload recruitable stroke work (PRSW) slope, and end-systolic pressure-length relationship (ESPLR) area. Because the blood flow in LAD artery was diminished by approximately 70%, there was a significant decrease in O2 delivery and uptake by the ischemic myocardium. Ischemia led to a significant fall in LAD regional contractile function with %SS decreasing from 15 +/- 2 to 7 +/- 2%, PRSW slope from 82 +/- 10 to 37 +/- 5 mmHg, and ESPLR area from 121 +/- 2 to 48 +/- 14 mmHg.mm (P < 0.05). In six dogs, the intracoronary administration of NaHCO(3) resulted in a significant increase in pH in LAD arterial and venous blood. There was, however, no significant increase in %SS (6 +/- 2), PRSW slope (43 +/- 10 mmHg), or ESPLR area (60 +/- 13 mmHg.mm). Since administration of NaHCO(3) resulted in a significant increase in PCO2 in LAD arterial and venous blood, similar experiments were carried out in five dogs, but with the intracoronary infusion of the amine buffer THAM [tris(hydroxymethyl)aminomethane (Tris) buffer; 2-amino-2-hydroxyl-1,3-propandiol] instead of NaHCO3. Although administration of THAM resulted in a significant increase in pH and a significant decrease in PCO2, in both LAD arterial and venous blood, there was no significant improvement in any of the parameters used to assess myocardial contractile function. In conclusion, administration of alkali (NaHCO3 or THAM) does not enhance the contractile function of the ischemic myocardium.

Alkalies↗
PubMed1995

Intermittent warm blood cardioplegia. Warm Heart Investigators.

BACKGROUND: Warm heart surgery implies continuous perfusion with normothermic blood cardioplegia. Interruption of cardioplegia, however, facilitates construction of distal coronary anastomoses and is the method practiced by many surgeons. To determine whether intermittency is harmful, we present results from 720 coronary bypass patients, protected with intermittent antegrade warm blood cardioplegia, that were derived from a previous study of normothermic versus hypothermic cardioplegia. METHODS AND RESULTS: Mean +/- SD age was 60.8 +/- 9.0 years; 27% of cases were urgent; 16% of patients had > 50% left main stenosis, and 19% had grade III or IV ventricles. A mean of 3.2 +/- 0.9 grafts was constructed. The average aortic cross-clamp time was 61.8 +/- 22.2 minutes. The longest single time off cardioplegia (LTOC) averaged 11.4 +/- 4.0 minutes per patient. The cumulative time off cardioplegia as a percentage of the cross-clamp time (PTOC) was 48.2 +/- 18.6% per patient. LTOC and PTOC were divided into quartiles (LTOC, < 10, 10 to 11, 12 to 13, and > 13 minutes; PTOC, < 36%, 36% to 49%, 50% to 62%, and > 62%) and related to the prespecified composite outcome of mortality, myocardial infarction according to serial CK-MB sampling, and low-output syndrome (LOS). Longer LTOC was harmful (event rates per quartile, 13.5%, 10.3%, 10.9%, and 19.0%; P = .046), whereas longer PTOC was protective (16.1%, 17.2%, 9.4%, and 10.6%; P = .07). Stepwise logistic regression was performed, controlling for demographic and angiographic predictors. In the multivariate models, LTOC remained detrimental (P = .07) and PTOC remained beneficial (P = .053). Additional modeling after entering surgeon identity (P < .001) into the risk equation eliminated the PTOC effect, whereas LTOC remained predictive of adverse outcomes (P = .053; odds ratio, 1.06; 95% CI, 1.00, 1.13). CONCLUSIONS: The data indicate that a reasonable margin of safety exists with intermittent, antegrade warm blood cardioplegia. Repeated interruptions of warm blood cardioplegia are unlikely to lead to adverse clinical results if single interruptions are < or = 13 minutes.

Aged↗