A. Oduro

An Entirely Subcutaneous Implantable Cardioverter–Defibrillator

BACKGROUND Implantable cardioverter-defibrillators (ICDs) prevent sudden death from cardiac causes in selected patients but require the use of transvenous lead systems. To eliminate the need for venous access, we designed and tested an entirely subcutaneous ICD system. METHODS First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients. RESULTS The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous ICD for terminating induced ventricular fibrillation, albeit with a significantly higher mean (+/-SD) energy requirement (36.6+/-19.8 J vs. 11.1+/-8.5 J). Among patients who received a permanent subcutaneous ICD, ventricular fibrillation was successfully detected in 100% of 137 induced episodes. Induced ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two consecutive tests. Clinically significant adverse events included two pocket infections and four lead revisions. After a mean of 10+/-1 months, the device had successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. CONCLUSIONS In small, nonrandomized studies, an entirely subcutaneous ICD consistently detected and converted ventricular fibrillation induced during electrophysiological testing. The device also successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. (ClinicalTrials.gov numbers, NCT00399217 and NCT00853645.)

Endotoxin-induced organ injury

ObjectiveTo review the effects of endotoxemia on the major organ systems of the body and discuss potential mechanisms of tissue injury. DesignAppraisal of 60 articles representing a cross section of studies relating to in vivo and in vitro responses to endotoxin. Main MethodsCell cultures, isolated tissue preparations, animal and human studies. ResultsEndotoxemia results in the activation of numerous cellular and hematogenous mediators. These mediators range from prostaglandins, thromboxanes, and leukotrienes, to complement components. Tumor necrosis factor may be responsible for initiating many of the observed responses to endotoxin. Species and tissue specificity are a prominent feature of the response to endotoxin. ConclusionsNo single agent can yet be implicated as the common mediator of endotoxin-induced organ injury. Endotoxin initiates the elaboration of a cascade of secondary mediators that amplify the response to the initial insult. The relative importance of individual agents as mediators of the response to endotoxin varies with the experimental model studied. (Crit Care Med 1993; 21:S19-S24)

Effect of aspirin in coronary artery bypass grafting

OBJECTIVES To evaluate the effect of aspirin (ASA) therapy on postoperative blood loss, transfusion requirements, reoperation for bleeding, duration of stay in the intensive care unit and in the hospital in a selected population undergoing a first coronary artery bypass grafting (CABG) surgery. DESIGN Prospective observational study in consecutive patients during a 3-month period. SETTING A teaching cardiothoracic center. PARTICIPANTS Two hundred forty consecutive patients undergoing elective coronary artery bypass grafting surgery for the first time. INTERVENTIONS Two hundred forty consecutive patients admitted for a first CABG the day before surgery were visited. patients with an abnormal routine coagulation screen or taking drugs that might have affected their coagulation mechanisms were prospectively excluded (n = 96). The date of the last dose of ASA was recorded in the 144 remaining patients, and data were acquired prospectively. MEASUREMENTS AND MAIN RESULTS Total mediastinal blood drainage, blood products usage, reopening, and duration of intensive care unit and hospital stay were recorded. Patients were grouped by days free of ASA. There were no significant differences detected between groups. CONCLUSIONS In patients undergoing a first CABG and with no known factors affecting their coagulation, ASA therapy did not appear to increase blood loss, reopening for bleeding, or blood products usage requirements during the hospital stay. ASA therapy did not influence the duration of stay in intensive care or in the hospital.

Management of donors for heart and heart–lung transplantation

The quality of donor organs will determine the quality of life for the recipient and the importance of optimal management of the multi‐organ donor is that the organs may benefit up to five, critically ill, patients. The basic principle is to maintain sufficient preload to minimise the need for inotropic support and it is recommended that all multiple organ donors should have central venous and arterial pressure monitoring in addition to adequate venous access. The importance of the choice of fluid for volume expansion and the management of the hormonal disturbances which follow brain death are considered.

Dopexamine hydrochloride: pharmacology and use in low cardiac output states.

T HE TERM “INOTROPE” is broadly used to describe agents that enhance cardiac performance, although the mechanism by which some of these drugs improve myocardial function may be attributable less to their effect on myocardial contractility than to the other hemodynamic changes that are associated with their use. In the treatment of cardiac failure, agents with pharmacodynamic profiles that combine relatively mild direct effects on the myocardium with those resulting from a relatively greater effect on preload and afterload offer potential benefits from the standpoint of myocardial energy use. This is of prime concern in both the acutely or chronically ischemic heart and following cardiopulmonary bypass (CPB) when cardiac failure can, on occasion, be ascribed more to unavailability of energy reserves than to persisting ischemia. Dopexamine hydrochloride, a synthetic analog of dopamine, is characterized by just such a profile of action and may offer a favorable alternative to the more established therapeutic regimens of dopamine and dobutamine. The pharmacology of dopexamine and its use in the treatment of chronic or postoperative cardiac failure is reviewed here.

Management of low cardiac output syndrome after cardiac surgery using enoximone

This case report describes the use of enoximone, a potent phosphodiesterase F‐IV inhibitor with inotropic and vasodilator actions, to treat low output syndrome after cardiac surgery. The reduced cardiac output was unresponsive to a combination of inotropic drugs and intra‐aortic balloon counterpulsation was contraindicated. Cardiac output was increased dramatically by enoximone, but systemic vascular resistance and perfusion pressure remained low until the addition of metaraminol.

Effects of Intravenous Enoximone following Coronary Artery Bypass Surgery

The effects of intravenous enoximone were investigated in patients with reduced left ventricular ejection fraction following coronary artery bypass graft surgery. Pulmonary capillary wedge pressure was maintained at its original level during therapy. Results showed an improvement in cardiac index of approximately 35% and a reduction of systemic vascular resistance of approximately 30% in 10 out of 16 patients. In an attempt to explain the failure of 6 patients to respond to enoximone therapy, preliminary studies revealed that a repeat dose of enoximone may elicit a response. It is further suggested that postsurgical trauma may change the behaviour of the heart in response to this agent, perhaps due to a reduction in high-energy phosphate levels.

Mesenteric ischaemia and endotoxaemia during cpb may cause significant splanchnic injury in transplant patients

Under normal conditions endotoxins are retained within the lumen of the qut and are prevented from leaking into the portal circulation by the integrity of the qut mucosa.If small quantities permeate through the barrier and reach the liver they are filtered out by the Kupfer cells. Eowever it has been shown that during cardiopulmonary bypass (CPB) there is a significant level of endotoxin passing through the liver and reachinq the systemic circulation (1) , The mechanism for this is complex. The vasopressor response to CPB is well recognized and includes the combined effects of catecholamine release, activation of the renin anqiotensin system, increased secretion of vasopressin and local tissue agents such as thromboxane A2. The resulting low flow in the splanchnic circulation accompanied by reperfusion injury causes mucosal disruption and leakaqe of endotoxins (2). This low flow in the portal system also adversely effects the liver and the ability of the Kupfer cells to effectively deal with the endotoxin challenge, and so they respond by producing cytokines such as tumour necrosis factor.

Inotropic drugs, calcium, phosphodiesterase inhibitors

This review deals with developments in inotropic therapy over the past year. Papers of significant clinical interest are examined, concentrating on developments that may influence current clinical practice or improve our understanding of the mechanisms of action of these drugs.

Anesthesia and Analgesia for Hip Surgery

Key preoperative issues in anesthesia for hip surgery are the choice of regional or general anesthesia and optimization of the patients’ medical condition. Intraoperatively, attention should be focused on intraoperative fluid management, avoidance of hypothermia, and minimization of the possibility of allogenic blood transfusion. Postoperatively, the need for enhanced care in higher-risk patients must be recognized. If general anesthesia is used, ideally this should be performed in conjunction with a form of local anesthetic technique. Fixation of hip fractures should be undertaken with minimum delay.