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Biomedical subjects

J C Horrow

Publications and source records attributed to J C Horrow.

At least 19 recordsLinked to original sources
PubMed1995

A multicenter, double-blind, placebo-controlled trial of aprotinin for reducing blood loss and the requirement for donor-blood transfusion in patients undergoing repeat coronary artery bypass grafting.

BACKGROUND: Aprotinin is a serine protease inhibitor that reduces blood loss and transfusion requirements when administered prophylactically to cardiac surgical patients. To examine the safety and dose-related efficacy of aprotinin, a prospective, multicenter, placebo-controlled trial was conducted in patients undergoing repeat coronary artery bypass graft (CABG) surgery. METHODS AND RESULTS: Two hundred eighty-seven patients were randomly assigned to receive either high-dose aprotinin, low-dose aprotinin, pump-prime-only aprotinin, or placebo. Drug efficacy was determined by the reduction in donor-blood transfusion up to postoperative day 12 and in postoperative thoracic-drainage volume. The percentage of patients requiring donor-red-blood-cell (RBC) transfusions in the high- and low-dose aprotinin groups was reduced compared with the pump-prime-only and placebo groups (high-dose aprotinin, 54%; low-dose aprotinin, 46%; pump-prime only, 72%; and placebo, 75%; overall P = .001). The number of units of donor RBCs transfused was significantly lower in the aprotinin-treated patients compared with placebo (high-dose aprotinin, 1.6 +/- 0.2 U; low-dose aprotinin, 1.6 +/- 0.3 U; pump-prime-only, 2.5 +/- 0.3 U; and placebo, 3.4 +/- 0.5 U; P = .0001). There was also a significant difference in total blood-product exposures among treatment groups (high-dose aprotinin, 2.2 +/- 0.4 U; low-dose aprotinin, 3.4 +/- 0.9 U; pump-prime-only, 5.1 +/- 0.9 U; placebo, 10.3 +/- 1.4 U). There were no differences among treatment groups for the incidence of perioperative myocardial infarction (MI). CONCLUSIONS: This study demonstrates that high- and low-dose aprotinin significantly reduces the requirement for donor-blood transfusion in repeat CABG patients without increasing the risk for perioperative MI.

Aged↗
PubMed1995

The incidence of venous emboli during extramedullary guided total knee arthroplasty.

During total knee arthroplasty (TKA), instrumentation of the marrow cavity with an intramedullary guide appears responsible for fatal intraoperative pulmonary embolism. Transesophageal echocardiography demonstrates venous emboli (VE) after tourniquet deflation during intramedullary guided TKA. Extramedullary guides avoid manipulating the marrow cavity. We determined the incidence of VE in 20 patients undergoing extramedullary guided TKA. Recordings of hemodynamic variables, mixed venous oximetry, end-tidal CO2 and N2 tensions, and echocardiograph images occurred after induction of anesthesia, after tourniquet inflation, during cementing, and for 15 min after tourniquet deflation. Large VE appeared in 14 patients and small VE in the other 6 patients. Large VE occurred only after deflation of the tourniquet. Beginning 3 min after tourniquet deflation, mean pulmonary arterial pressures increased from the baseline of 21 +/- 1.0 to 30 +/- 1.3 mm Hg and remained increased for the duration of the procedure. The incidence of large VE with extramedullary guided TKA did not differ compared to the previously reported incidence with intramedullary guided TKA. These data suggest that VE might arise from a thrombogenic effect of the tourniquet rather than from manipulation of the marrow cavity.

Aged↗
PubMed1995

The dose-response relationship of tranexamic acid.

BACKGROUND: Prophylactic administration of the antifibrinolytic drug tranexamic acid decreases bleeding and transfusions after cardiac operations. However, the best dose of tranexamic acid for this purpose remains unknown. This study explored the dose-response relationship of tranexamic acid for hemostatic efficacy after cardiac operation. METHODS: In prospective, randomized, double-blinded fashion, 148 patients undergoing cardiac operation with extracorporeal circulation were divided into six groups: a placebo group and five groups receiving tranexamic acid in loading doses before incision (range 2.5 to 40 mg.kg-1) and one-tenth the loading dose hourly for 12 h. The mass of blood collected by chest tubes over 12 h represented blood loss. Allogeneic transfusions within 12 h and within 5 d of surgery were tallied. RESULTS: The six groups presented similar demographics. Patients receiving placebo had increased postoperative D-dimer concentration compared to groups receiving tranexamic acid. Patients receiving at least 10 mg.kg-1 tranexamic acid followed by 1 mg.kg-1.h-1 bled significantly less (365, 344, and 369 g.12 h-1, respectively, for those three groups) compared with patients who received placebo (552 g, P < 0.05). Tranexamic dose did not affect transfusions. Only initial hematocrit affected whether a patient received an allogeneic transfusion within 5 days of operation (odds ratio 2.08 for each 3% absolute decrease in hematocrit). CONCLUSIONS: Prophylactic tranexamic acid, 10 mg.kg-1 followed by 1 mg.kg-1.h-1, decreases bleeding after extracorporeal circulation. Larger doses do not provide additional hemostatic benefit.

Adult↗
PubMed1994

Haemodynamic consequences of warm cardiac irrigation during cardiac surgery.

Following cardiopulmonary bypass (CPB) and prior to closing the chest, some surgeons irrigate the heart and pericardium with warm saline. This prospective study, using each patient as his own control, evaluated the haemodynamic effects of warm (44 +/- 5 degrees C) irrigation on the heart and pericardium following CPB. Following discontinuation of CPB, a Mon-a-therm model 6500 thermocouple monitor measured the myocardial septum and the irrigating fluid temperatures. Immediately before, during and two minutes after irrigation of the heart and pericardium, we measured heart rate (HR), systemic blood pressure (BP), pulmonary artery pressure (PAP), central venous pressure (CVP), thermodilution cardiac output, and calculated systemic vascular resistance (SVR). During warm irrigation, HR increased from 93 +/- 15 to 101 +/- 13 min-1 and systolic BP increased from 111 +/- 17 to 131 +/- 27 mmHg. After irrigation, HR decreased to 96 +/- 12 min-1 with no change in systolic BP. The calculated SVR after irrigation increased to 1117 +/- 413 dynes.sec.cm-5 from the pre-irrigation value of 821 +/- 243 dynes.sec.cm-5, while cardiac index decreased to 2.4 L.min-1.m-2 from its pre-irrigation value of 2.99 L.min-1.m-2. Warm irrigation of the pericardial pouch causes tachycardic and hypertensive responses in patients undergoing cardiac surgery.

Adult↗
PubMed1994

Price stickers do not alter drug usage.

Anaesthetists choose daily among wide varieties of neuromuscular blocking drugs and rapidly acting hypnotic agents. This study sought to determine whether definitive, immediate knowledge of drug cost might influence clinician choices, ultimately reducing the cost of anaesthesia care. Faculty anaesthetists, residents in training, and nurse anaesthetists served as subjects in this prospective, sequential, blinded study of prescribing habits. Weekly inventories of selected neuromuscular blocking and rapidly acting hypnotic agents were performed over 24 wk at a tertiary-care hospital. Supermarket style price stickers plainly indicating the hospital cost of each unit of drug appeared continually for 13 wk following an initial 11 wk control period. Both actual usage data in priced units as well as data normalized by total anaesthesia duration underwent comparison between control and priced periods. The usage of pancuronium, vecuronium, atracurium, mivacurium, succinylcholine, thiopentone, etomidate, and propofol did not differ in the control from the priced periods. Pipecuronium decreased after sticker placement (2 vs 1 vials.wk-1 median, P < 0.05), as did methohexitone (39 +/- 9.0 [SD] vs 29 +/- 11 syringes.wk-1, P < 0.05). Ketamine usage normalized by total anaesthesia duration increased (P < 0.05) following sticker placement. The weekly cost of all drugs inventoried normalized for caseload did not differ during the measurement periods. Immediate cost awareness, implemented simply as price stickers on drug units, had minimal impact on clinicians' drug usage in a tertiary care setting.

Anesthesia, General↗
PubMed1994

Echogenic emboli upon tourniquet release during total knee arthroplasty: pulmonary hemodynamic changes and embolic composition.

Echogenic venous emboli accompany tourniquet deflation during total knee arthroplasty. The associated pulmonary hemodynamic alterations and determined embolic composition were measured in 34 patients, undergoing 35 procedures. Ten patients received a femoral venous catheter on the operative side. Hemodynamic variables, heart rate and mixed venous oximetry, end-tidal CO2 and nitrogen tensions, and transesophageal echocardiograms were recorded after induction of anesthesia (baseline), after tourniquet inflation, after cementing, and for 15 min after tourniquet deflation. Echocardiograms revealed either showers of miliary echogenic material (Group S, 9 patients), or large echogenic masses superimposed on the showers (Group MS, 26 patients). In Group MS only, pulmonary vascular resistance index increased above baseline (205 +/- 16 [SEM] dyne.s.cm-2) beginning 5 min after tourniquet deflation (maximum 328 +/- 29, P < 0.05). Mean pulmonary arterial pressure increased above baseline (20 +/- 1.0 mm Hg) for both Groups S and MS beginning 3 min after tourniquet deflation (27 +/- 1.0, P < 0.05). Cardiac index did not change. Five of 10 patients demonstrated fresh thrombus from the catheter in the operative limb. Echogenic emboli occurred in all patients upon tourniquet deflation during knee arthroplasty. Pulmonary vascular resistance index increased only in patients with large echogenic material. Our data suggest that these emboli represent fresh thrombus formation during tourniquet inflation. Heparin administration prior to tourniquet inflation may diminish embolic showers.

Adult↗
PubMed1993

Thromboembolism coincident with tourniquet deflation during total knee arthroplasty.

Despite prophylactic therapy, pulmonary embolism remains the leading cause of perioperative mortality in patients undergoing total knee arthroplasty (TKA). We used transoesophageal echocardiography to monitor 29 consecutive patients during TKA. Showers of substantial amounts of echogenic material, lasting for 3-15 min, were visible in the right atrium and ventricle within 10-15 s of tourniquet deflation in all patients. A 3 x 6 mm fresh thrombus was aspirated from the central circulation of one patient. Another patient, who had had a Greenfield filter placed for previous thromboembolism, showed very little echogenic material after tourniquet deflation. The composition and importance of these echogenic emboli remain uncertain.

Adult↗
PubMed1992

Vomiting after alfentanil anesthesia: effect of dosing method.

This double-blind study correlated the association of nausea and vomiting after alfentanil with its method of administration (bolus dose vs continuous infusion). Of 40 women undergoing lower abdominal gynecologic or laparoscopic surgery, 20 received an intravenous alfentanil (30 micrograms/kg) bolus dose for induction of anesthesia, with subsequent bolus doses of 10 micrograms/kg every 10 min, and 20 received the same induction dose delivered over 1 min, followed by an intravenous infusion at 1.0 micrograms.kg-1.min-1. The infusion group experienced more frequent nausea and vomiting than the bolus dose group (50% vs 30%, respectively; P = 0.0001). Laparoscopic surgery affected the incidence of nausea and vomiting independently of the method of alfentanil administration (75% for laparoscopic vs 17% for incisional procedures; P = 0.0001). Laparoscopy and alfentanil infusion combined synergistically to worsen the incidence of nausea and vomiting. We conclude that alfentanil infusion for laparoscopic surgery entails a high risk for nausea and vomiting.

Adult↗
PubMed1991

Ventilatory compliance after three sufentanil-pancuronium induction sequences.

Poor ventilatory compliance, a predictable side effect of high-dose opioid induction techniques, is purportedly blunted by pretreatment with nondepolarizing muscle relaxant. This study used both total compliance and a subjective compliance score to compare three different sequences of opioid induction using a 2-min infusion of sufentanil 3 micrograms.kg-1. Nineteen patients in each of three groups received a total of 100 micrograms.kg-1 of pancuronium, in the following randomized double-blinded fashion: control, all pancuronium 1 min after sufentanil; pretreated, 1 mg pancuronium 1 min before sufentanil and the balance of pancuronium 1 min after sufentanil; and mixed, all pancuronium mixed with sufentanil. Topical lidocaine prior to induction permitted early oral airway insertion midway through the sufentanil infusion. Immediately at the conclusion of sufentanil infusion, a tightly fitted mask, anterior jaw thrust, and mechanical ventilator permitted measurement of plateau airway pressure and exhaled volume in five replicates. Pressure and volume measurements were repeated 5 min later. Total compliance was calculated as the median plateau airway pressure divided into its associated exhaled volume. Groups did not differ in demographics. In one control patient and two pretreated patients hemoglobin oxygen saturation as measured by pulse oximetry decreased below 90%. Immediately after sufentanil infusion, the total compliance for control patients of 4.1 ml.cmH2O-1 (mean [2.6-6.5, 95% confidence interval] ) did not differ from that of the pretreated group (6.3 [3.5-11.4] ml.cmH2O-1), but the mixed group exhibited higher compliance (40.3 [33.8-47.9] ml.cmH2O-1) than the other groups (P less than 10(-8]. All groups achieved similar total compliances several minutes after a total of 100 micrograms.kg-1 pancuronium had been administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Intravenous↗