In Reply:—
Our finding of a 90% incidence of hypotension after single-dose (“conventional”) spinal anesthesia in elderly patients is consistent with the high incidence of hypotension reported in the literature. 1Others have reported a 100% incidence of hypotension necessitating vasopressor treatment. 2Buggy et al. 3found a 75% incidence of systolic hypotension even with a volume loading of 500 ml hetastarch, 6%, plus 500 ml Hartmann’s solution. The strong association of spinal hypotension with ST depression in this patient population is cause for concern. 4
Our choice of a 10-mg dose of spinal bupivacaine was intended to represent conventional practice and not necessarily the lowest dose of bupivacaine. This choice was arbitrary and, I suspect, underestimates the dosing used by many of our colleagues. The important point, however, is that, rather than treat hypotension, one can avoid it by using a low-dose local anesthetic plus an opiate spinal technique.
It is true that this technique provides a “nociceptive block” and does not provide a profound motor block. Certainly, there are surgeries in which the need for an intense motor block would necessitate higher doses of local anesthetic if one is to use spinal anesthesia. Likewise, there are surgeries (e.g. , ambulatory) in which the absence of a profound motor block may be advantageous.
Our article did not intend to suggest that there is no other way to reduce the hypotension of spinal anesthesia. Titrated dosing with continuous spinal anesthesia is fairly effective in this regard, 2but it is my impression that many practitioners prefer the speed and simplicity of a single-shot technique. Although unilateral spinal anesthesia might offer greater hemodynamic stability than bilateral blockade, at best it is impractical (time-consuming) when surgery is to be performed with the patient in the supine position.
