Venous embolization after deflation of lower extremity tourniquets

Massive pulmonary embolism has been reported to occur with the use of lower extremity tourniquets. We used transesophageal echocardiography to determine the incidence of venous embolism during lower extremity orthopedic surgery performed with a pneumatic tourniquet. The hemodynamic and respiratory consequences of all embolic events were assessed. Venous emboli were detected after tourniquet deflation in 8 of 30 procedures. The incidence of embolism was unrelated to the type of surgical procedure performed or the duration of tourniquet inflation. There were no significant differences in preoperative characteristics or postdeflation hemodynamic and respiratory responses between patients with and without emboli. Venous embolization is a relatively common event after tourniquet deflation. The clinical significance of these events remains to be determined.

Transdermal fentanyl for postoperative pain management in patients recovering from abdominal gynecologic surgery

The current placebo-controlled double-blinded study was undertaken to assess the safety and efficacy, as well as the potential clinical role, of the transdermal therapeutic system (TTS) of fentanyl delivery in the postoperative setting. TTS patches releasing 25 micrograms.h-1 or 50 micrograms.h-1 or placebo were applied to 95 women 1 h before abdominal gynecologic surgery during general anesthesia. Postoperatively, patients self-administered intravenous morphine as required using patient-controlled analgesia with a 1-mg incremental dose and a 6-min lockout interval. Each was assessed upon admission to the postanesthesia care unit and at intervals over the following 72 h with respect to vital signs, visual analogue scale pain and satisfaction scores, side effects, and cumulative morphine use. Data were analyzed using analysis of variance, Kruskal-Wallis, and chi-square. P less than 0.05 was considered significant. There were no demographic differences among groups. Beginning 32 h after TTS application, a statistically significant morphine-sparing effect was seen with the 50 micrograms.h-1 patch. There were no significant differences among groups with regard to visual analogue scale pain scores at rest, patient satisfaction, or the incidence of side effects; a significant reduction in pain upon movement was noted at 24 h in patients treated with TTS 50 micrograms.h-1. This finding constituted the only benefit noted with this form of analgesic therapy in the present investigation.

The clinical pharmacology of antihypertensive drugs

Antihypertensive drugs act centrally (methyldopa, clonidine, guanabenz), peripherally (prazosin, guanadrel, guanethedine, hydralazine, minoxidil), centrally and peripherally (beta-adrenergic blocking drugs) and systemically [angiotensin converting enzyme (ACE) inhibitors and diuretics]. Centrally-acting antihypertensives decrease blood pressure by diminishing sympathetic outflow from the vasomotor centre. Peripherally-acting antihypertensives act by depleting or inhibiting the release of catecholamines from the peripheral nerve ending or altering the response at alpha 1- and alpha 2-receptor sites. Beta-adrenergic blocking drugs act through a variety of mechanisms by either decreasing cardiac output, decreasing renin release, inhibiting prejunctional release of norepinephrine or through central mechanisms. Diuretics act as indirect vasodilators by depleting salt and water not only within the intravascular compartment but within the intramural portion of the arteriole, thereby diminishing its responsiveness to catecholamine and angiotensin II stimulation. ACE inhibitors such as captopril and enalapril act by inhibiting the conversion of angiotensin I to angiotensin II thereby decreasing the vasoconstrictor effect of angiotensin II and the aldosterone production secondary to angiotensin II stimulation. The main differences between captopril and enalapril is that enalapril does not possess the potentially toxic sulphydryl group and can be given twice-daily. Both drugs may show accumulation in patients with impaired renal function.

Mechanisms of action and the clinical pharmacology of beta-adrenergic blocking drugs

At present more than 20 beta-adrenergic blocking drugs are commercially available in Western Europe, and six are available in the United States. The clinical indications for their usage include hypertension, arrhythmias, ischemic heart disease, thyrotoxicosis, migraine headaches, glaucoma, and anxiety states. We will review the mechanisms suggested for the antihypertensive action of beta-adrenergic blocking drugs as well as these agents' clinical pharmacologic aspects. In general, the pharmacodynamic effects of the beta blocking drugs are quite similar, yet the properties of biotransformation, including pharmacokinetics, tend to be distinguishing features.