Patients with compromised cardiovascular function who are undergoing cardiothoracic or other lengthy surgical procedures are at risk of complications from the hemodynamic effects of the long-acting nondepolarizing neuromuscular blocking agents (NMBs), which have been in use for several decades. The development of agents that maintain a stable hemodynamic profile is a potential advantage to this patient population. This literature review, which was completed in May 1992, describes the profiles of doxacurium and pipecuronium, two recently developed long-acting NMBs with increased potency over d-tubocurarine, metocurine, and pancuronium. Doxacurium is a benzylisoquinolinium compound with an ED95 of 0.025 mg/kg. Pipecuronium, a steroidal agent, has an ED95 of 0.04 mg/kg. Twice the ED95 of either agent produces a duration of action comparable to that with 2 times ED95 of pancuronium, but neither doxacurium nor pipecuronium possesses vagolytic or histamine-releasing properties at therapeutic doses. Although no significant differences in serum elimination half-life or plasma clearance of doxacurium have been noted between young and elderly patients, as with other NMBs, the duration of action of doxacurium may be somewhat prolonged and seems to be more variable in older patients and in patients with impaired hepatic or renal function. A similar pattern appears to occur with pipecuronium. Children seem to require higher doses of doxacurium than adults to achieve the same degree of neuromuscular block but recover from the effects more rapidly. Doxacurium and pipecuronium produce no dose-dependent or clinically significant changes in heart rate, mean arterial pressure, or cardiac output either in patients with normal cardiac function or in those with coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)