Biomedical subjects

L J Mark

Publications and source records attributed to L J Mark.

5 recordsLinked to original sources

PubMed1992

Heparin management protocol for cardiopulmonary bypass influences postoperative heparin rebound but not bleeding.

A group of 63 adult patients undergoing cardiac surgical procedures requiring cardiopulmonary bypass (CPB) were studied to examine the relationship between heparin doses administered and postoperative bleeding. Patients were randomly assigned either to receive heparin 200 U/kg and additional heparin as needed to reach and maintain an activated clotting time (ACT) greater than 400 s for CPB (group A, n = 30), or to receive heparin 400 U/kg and additional heparin as needed to reach and maintain a whole blood heparin concentration greater than 4.0 U/ml for CPB (group H, n = 33). Groups were compared for the amount of postoperative bleeding, heparin rebound, homologous transfusion requirements, and standard laboratory coagulation tests. In the last 33 patients studied, additional tests of platelet aggregation and plasma levels of beta thromboglobulin (BTG), antithrombin III, and several markers of fibrinolysis were measured and compared by group. The mean heparin dose was 28,000 +/- 4,800 U for group A and 57,000 +/- 10,700 U for group H (P less than 0.05 for group A vs. group H). At 8 and 24 h postoperatively, mediastinal drainage did not differ significantly between groups (mean 24-h drainage +/- SD = 901 +/- 414 ml in group A, 1035 +/- 501 ml in group H), nor did the incidence of transfusion with homologous blood products.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Calcium does not augment phenylephrine's hypertensive effects.

Ca and phenylephrine, both of which increase mean arterial pressure (MAP), are often administered concurrently during resuscitation of critically ill patients. To determine whether the response to phenylephrine is potentiated by Ca administration, we studied eight adult patients 24 h after aortocoronary bypass surgery. Each patient received three doses of phenylephrine (150, 300, and 450 ng/kg.min), administered both with and without CaCl2 (5 mg/kg bolus followed by a 2-mg/kg.h infusion). Phenylephrine alone at 150, 300, and 450 ng/kg.min increased MAP by 2%, 6%, and 17%, respectively. Ca alone increased serum ionized Ca levels from 1.00 +/- .03 (SEM) to 1.20 +/- .02 mM (p less than .05) and increased MAP from 84 +/- 1 to 90 +/- 2 mm Hg (p less than .05), but had no effect on cardiac index (CI). When administered concurrently with Ca, phenylephrine at 150, 300, and 450 ng/kg.min increased MAP by 6%, 7%, and 13%, respectively. Phenylephrine had no effect on CI, pulmonary capillary wedge pressure, CVP, or heart rate whether or not it was administered with Ca. We conclude that concomitant Ca administration does not augment the hypertensive response to phenylephrine in normotensive patients recovering from open heart surgery.

Aged↗

PubMed1990

Calcium attenuates epinephrine's beta-adrenergic effects in postoperative heart surgery patients.

Epinephrine and calcium possess both cardiac inotropic and vasopressor activity. In addition, epinephrine's cardiovascular effects are mediated via increases in intracellular calcium. As a result, many clinicians administer the two agents together in an attempt to augment their effects. Although this approach seems rational, it has never been proven effective. We evaluated the cardiovascular and hyperglycemic actions of epinephrine (10 and 30 ng/kg/min), with and without calcium chloride administration (10 mg/kg bolus followed by 2 mg/kg/hr infusion), in a prospective, randomized, blinded, crossover designed study. Twelve adult patients were studied 1 day after aortocoronary bypass surgery. Calcium chloride raised ionized calcium levels from 1.06 +/- 0.03 (mean +/- SEM) to 1.44 +/- 0.05 mM (p less than 0.05). Calcium raised mean arterial pressure from 85 +/- 1 to 94 +/- 2 mm Hg (p less than 0.05) but had no significant effect on cardiac index. Epinephrine alone at 10 and 30 ng/kg/min significantly raised cardiac index from 2.7 +/- 0.2 to 3.0 +/- 0.2 (p less than 0.05) and 3.6 +/- 0.3 (p less than 0.05) l/min/m2. After calcium, epinephrine failed to significantly increase cardiac index. Epinephrine at 30 ng/kg/min significantly increased mean arterial pressure from 87 +/- 1 to 95 +/- 2 mm Hg (p less than 0.05). After calcium, epinephrine had no significant effect on blood pressure. In addition, epinephrine's hyperglycemic effect was blunted by calcium. Plasma epinephrine levels were similar during control and calcium infusions. We conclude that calcium blunts epinephrine's beta-adrenergic actions in postoperative cardiac surgery patients.

Blood Glucose↗

PubMed1990

Baseline activated coagulation time should be measured after surgical incision.

The activated coagulation time (ACT) is widely used to guide heparin and protamine dosing during cardiac surgery. A common protocol involves establishing a baseline ACT before administering heparin, then using this ACT as a target value for assessing the adequacy of heparin neutralization after cardiopulmonary bypass. Results vary in previous comparisons of baseline ACT to postprotamine ACT, with some showing postprotamine ACT significantly below baseline values. The present study examined ACTs at three possible baseline intervals in 68 patients at two institutions: (a) before anesthetic induction; (b) after anesthetic induction; and (c) after sternotomy. Baseline ACT decreased significantly with anesthesia and surgery. The poststernotomy baseline ACT best matched the postprotamine ACT. It appears likely that surgery induces a thromboplastic response that decreases ACT. Establishing baseline ACT before anesthetic induction would predispose to false diagnoses of adequate protamine neutralization after cardiopulmonary bypass, because ACT is relatively insensitive to low concentrations of unneutralized heparin. Baseline ACTs should therefore be measured after surgical incision.

Aged↗

PubMedDate not supplied

The difficult airway: mechanisms for effective dissemination of critical information.

The perioperative management and dissemination of critical information regarding a patient with an unexpected difficult intubation, including successful application of a difficult airway algorithm (Figure 1), are described. Documentation and dissemination of critical information include entry of patient data into an in-hospital computerized Difficult Airway/Intubation Registry, simultaneous application of a highly visible Difficult Airway/Intubation Patient Wrist Band (coded for access to computer registry), summary reports distributed to health care providers, and enrollment of the patient in the Medic Alert Foundation International's newly established category difficult airway/intubation for 24-hour access. We postulate that the widespread use of the procedures described in this report may reduce the contribution of unexpected difficult airway/intubation to anesthetic morbidity and mortality.

Algorithms↗