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Biomedical subjects

R E Barnette

Publications and source records attributed to R E Barnette.

16 recordsLinked to original sources
PubMed1997

Sequestration of vecuronium bromide during extremity surgery involving use of a pneumatic tourniquet.

BACKGROUND: We hypothesized that sequestration of a neuromuscular blocking agent could occur during surgery involving use of an extremity tourniquet and cause changes in neuromuscular function after tourniquet release. METHODS: Sixteen patients scheduled for total knee replacement were randomized to one of two groups. In Group I, 10 patients were administered 0.1 mg/kg of vecuronium 5 minutes prior to inflation of a pneumatic tourniquet; in Group II, 6 patients were administered 0.1 mg/kg of vecuronium after inflation of the tourniquet. The twitch (T1) and train-of-four (TOF) were analyzed before and after release of the tourniquet, as was the rate of recovery of T1 and TOF. Serial vecuronium plasma levels were drawn during the study. RESULTS: The T1 and TOF responses and the T1 and TOF recovery rates were not significantly different between groups at tourniquet deflation. In Group I, after release of the tourniquet, T1 and TOF recovery rate decreased significantly over a 10-min period (10% +/- 3 to 4% +/- 4 and 0.12 +/- 0.06 to 0.06 +/- 0.04, mean +/- SD, respectively); in Group II, T1 and TOF recovery rate increased significantly over a 10-min period following deflation of the tourniquet (10% +/- 6 to 14% +/- 7 and 0.10 +/- 0.03 to 0.18 +/- 0.02, respectively). Changes in pharmacodynamics were temporally associated with transient but statistically significant changes in vecuronium plasma levels. Overall pharmacokinetics during the study period were comparable between groups. After administration of neostigmine 30-40 micrograms/kg i.v. all subjects in both groups showed complete TOF recovery within 15 min. CONCLUSIONS: Sequestration of a bolus dose of vecuronium, by a pneumatic tourniquet, causes transient changes in pharmacokinetics and pharmacodynamics. These changes are of limited clinical importance and do not affect reversibility of neuromuscular block.

Hemostasis, Surgical↗
PubMed1997

Intravenous vitamin K1 prior to orthotopic heart transplantation: effects in vivo and in vitro.

BACKGROUND: Vitamin K1 is used to reverse warfarin's anticoagulant action. It is unclear whether intravenous vitamin K1 is safe or efficacious prior to urgent cardiac surgery. METHODS: We retrospectively and prospectively examined the effects of preoperative intravenous vitamin K1 in vivo (administered for warfarin reversal immediately before heart transplantation) on intraoperative blood product utilization, hemodynamics and coagulation parameters. We also determined the direct effects of vitamin K1 in vitro on rings of human saphenous vein and internal mammary artery. RESULTS: In the retrospective limb, 29 of 67 patients were administered vitamin K1 preoperatively via slow intravenous infusion. Vitamin K1 administration produced no adverse outcome but did not affect subsequent perioperative use of blood products. In the prospective limb (n = 10), vitamin K1 significantly (P < or = 0.01, Student t-test) altered mean arterial pressure (from 85 +/- 15 to 76 +/- 16 mmHg), systemic vascular resistance (from 1364 +/- 308 to 1078 +/- 252 dyn.s.cm-5), and cardiac index (from 2.3 +/- 0.3 to 2.7 +/- 0.3 L/min/m2) (mean +/- SD). Significant decreases in prothrombin time (19.8 +/- 2.7 to 17.7 +/- 1.8 s) and activated clotting time (164 +/- 26 to 137 +/- 24 s) were observed at 60 min. In vitro vitamin K1 (10(-7) to 10(-4) M) had no effect on the tone of noradrenaline-constricted rings. CONCLUSIONS: Vitamin K1, administered by intravenous infusion prior to heart transplantation, did not alter subsequent perioperative blood product administration. Vitamin K1 rapidly reversed the anticoagulant effect of warfarin and produced modest hemodynamic changes. The decrease in systemic vascular resistance is probably not due to a direct effect of vitamin K1 on vascular smooth muscle.

Anticoagulants↗
PubMed1992

Interpleural placement of central venous catheter. Failure of preventive practices.

An attempt to access the central venous circulation in a patient with a persistent left pleural effusion resulted in positioning the catheter within the pleural space. Chest roentgenograms with injection of contrast material revealed catheter location. Compliance with standard preventive practices may not assure correct placement of a central venous catheter via the internal jugular route in a patient with a hemothorax or effusion of unknown composition.

Catheterization, Central Venous↗
PubMed1991

Isradipine for treatment of acute hypertension after myocardial revascularization.

OBJECTIVE: To evaluate the efficacy and duration of action of iv isradipine in the control of postoperative hypertension immediately after myocardial revascularization. DESIGN: Prospective, phase 2 trial. SETTING: Surgical ICU, university hospital. PATIENTS: Twenty-one (15 male, six female) patients, ages 49 to 75 yr (mean 65 +/- 5), undergoing elective myocardial revascularization. INTERVENTIONS: Twenty-one patients with postoperative hypertension after coronary artery bypass graft surgery received iv isradipine, a new dihydropyridine calcium-channel antagonist. Mean duration of the isradipine infusion was 96.9 +/- 29 min. Mean dose of isradipine, indexed to weight, was 16.63 +/- 6.66 micrograms/kg (n = 20). MEASUREMENTS AND MAIN RESULTS: Twenty of the 21 patients achieved satisfactory BP control. The reduction in mean arterial pressure (MAP), first noted at the 15-min point, was maximal at 1 hr when MAP decreased from 102 +/- 9 mm Hg baseline to 81 +/- 5 mm Hg (p less than .01), accompanied by a significant (p less than .01) decrease in systemic vascular resistance from 1753 +/- 339 baseline to 1180 +/- 229 dyne.sec/cm5. The CVP, pulmonary artery diastolic pressure, and pulmonary artery occlusion pressure did not change significantly. Heart rate and cardiac index increased; however, stroke volume index did not change. CONCLUSIONS: Isradipine is an acceptable agent for the treatment of hypertension in this setting.

Aged↗
PubMed1988

In vitro effect of fresh frozen plasma on the activated coagulation time in patients undergoing cardiopulmonary bypass.

The in vitro effect of fresh frozen plasma (FFP) on the whole blood activated coagulation time (ACT) was examined in 18 patients undergoing cardiopulmonary bypass (CPB) during coronary artery bypass graft surgery. The addition of FFP to whole blood in vitro, after systemic heparinization, significantly prolonged the ACT from 451 +/- 21 seconds (mean +/- SE) to 572 +/- 41 seconds (P less than 0.05). There was no significant correlation between the plasma antithrombin III activity and the prolongation in ACT after systemic heparinization, with or without addition of FFP. The addition of FFP to whole blood in three of the six patients who exhibited heparin resistance (ACT less than 400 seconds after administration of 350 unit/kg heparin) did not prolong the ACT to greater than 400 seconds. These observations suggest that infusion of FFP will further prolong the ACT after heparin administration in most patients including some with initial heparin resistance.

Adult↗
PubMedDate not supplied

Modification of fresh-frozen plasma transfusion practices through educational intervention.

The effect of an educational program designed to address misconceptions about the perioperative transfusion of fresh-frozen plasma (FFP) was examined. Results of a baseline audit of FFP use were compared to those of a study subsequent to the educational process. Statistical analysis of the data revealed that the decrease in the number of patients transfused with FFP, from 32 of 2077 operative cases in Group A (baseline) to 18 of 2540 operative cases in Group B (after education), was significant (p less than 0.01). Analysis of the justifications given for transfusion of FFP revealed that the increase in acceptable indications from 47 percent in Group A to 78 percent in Group B was also significant (p less than 0.05). There was no significant difference between the two groups in units of FFP transfused per patient (Group A, 3.66 +/- 3.2, vs. Group B, 2.47 +/- 1.7) or red cells (Group A, 2.84 +/- 5.2, vs. Group B, 5.22 +/- 4.4), and the patterns of platelet transfusion were similar in the two groups. There was a significant difference in the postoperative partial thromboplastin time (Group A, 38.2 +/- 8.7 vs. Group B, 56.3 +/- 24 seconds, p less than 0.01) but no significant difference in postoperative prothrombin time (Group A, 14.1 +/- 2.6 vs. Group B, 15.4 +/- 3.3 seconds). It can be concluded that an educational program designed to address misconceptions in transfusion practice can alter physician performance and thereby reduce the inappropriate use of FFP.

Blood Transfusion↗