Spinal anesthesia for cesarean section: isobaric versus hyperbaric solution

The present study was undertaken to compare the outcomes of hyperbaric versus isobaric spinal anesthesia in Cesarean delivery.

The anesthetic solution was administered in sitting position as this posture is commonly used in this clinical setting. Except for the baricity of the anesthetic solution, identical technique was employed for every parturient in the study. Following administration of anesthetic solution the parturient immediately resumed horizontal supine position. The solutions used were 2.0 mL of 0.5% tetracaine in 5% dextrose (hyperbaric) for Group H (n = 30) and in cerebrospinal fluid (isobaric) for Group I (n = 30).

Both hyperbaric and isobaric tetracaine given in sitting position provided adequate analgesic levels. However, hyperbaric tetracaine solution produced a slightly higher median peak level of wilder range, and caused a higher incidence of hemodynamic changes and subjective sensation of "feeling sick" than isobaric tetracaine. Additionally, the duration of surgical anesthesia was shorter and the sacral block was longer for hyperbaric tetracaine solution than for isobaric tetracaine solution at same dose and concentration. Only one mother in Group H needed supplemental inhalation anesthesia for a subsequent hysterectomy due to uncontrollable bleeding. There were no complications, including postpuncture headache in either group.

Our results indicated that numerous variables must be taken into consideration in predicting the outcome of a spinal anesthesia. Alternation in the technique and individual patient factor may individually or collectively produce different results.