Hypobaric spinal anesthesia: a review of the literature and some clinical observations.
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We conducted a double-blinded examination of the effects of norepinephrine as a vasoconstrictor on the onset and duration of tetracaine spinal anesthesia in 80 surgical patients. The patients were randomly allocated to four groups (n = 20 in each group). Each patient received 10 mg of tetracaine in a volume of 2.0 mL which contained either 0 micrograms/mL, 5 micrograms/mL, 10 micrograms/mL, or 15 micrograms/mL of norepinephrine. The onset of spinal anesthesia was determined by the time to reach Th-10 level as well as by the time required to obtain the highest level of sensory analgesia. The time for two-segment regression and full-motor recovery were defined as the duration of spinal anesthesia. The time to reach Th-10, the highest analgesia level, and the time to obtain the highest analgesia level did not differ among the groups. Two-segment regression was prolonged significantly by 175%, 103%, and 106% as compared with the plain tetracaine group, in 5 micrograms/mL, 10 micrograms/mL, and 15 micrograms/mL of norepinephrine groups, respectively. Motor recovery also was extended significantly by 111%, 152%, and 121% as compared with the plain tetracaine group, in 5 micrograms/mL, 10 micrograms/mL, and 15 micrograms/mL of norepinephrine groups, respectively. There were no differences in the changes of arterial blood pressure and heart rate associated with the addition of norepinephrine among the groups. We conclude that norepinephrine provides a clinically meaningful prolongation of the duration of tetracaine spinal anesthesia.
BACKGROUND AND OBJECTIVES: Intraspinal administration of neostigmine has been shown to prevent induction of hypotension in rats by bupivacaine spinal block, and thus to provide greater hemodynamic stability. This study was undertaken to determine whether subarachnoid neostigmine would prevent bupivacaine spinal anesthesia from causing hypotension or bradycardia in patients undergoing abdominal hysterectomy. METHODS: Of 40 patients scheduled for abdominal hysterectomy under spinal anesthesia, 20 were randomly assigned to each of two groups. The control group (CG) received 1.5 mL subarachnoid saline followed by 15 mg (3 mL) of hyperbaric bupivacaine 0.5%. The neostigmine group (NG) received 75 micrograms (1.5 mL) of subarachnoid neostigmine followed by 15 mg (3 mL) of hyperbaric bupivacaine 0.5%. No preload was given. Hypotension was treated with 4-mg intravenous boluses of ephedrine to keep blood pressure above 75% of the baseline value. The skin body temperature was measured with probes at the suprascapular region and at the foot. RESULTS: Spinal neostigmine (75 micrograms) failed to prevent bupivacaine-induced hypotension. There was no statistical difference in the incidence of brady-cardia between the groups (NG, 2/20; CG 1/20), although the bradycardia appeared to be qualitatively different, being somewhat delayed in the NG. Spinal neostigmine did not alter the onset or duration of sensory block and did not affect skin body temperature in either anesthetized or unanesthetized sites. The incidence of intraoperative nausea was 20% in the NG and 5% in the CG. CONCLUSION: A 75-micrograms subarachnoid neostigmine dose does not affect blood pressure or heart rate during bupivacaine spinal anesthesia.
BACKGROUND AND OBJECTIVES: The use of thin single-hole pencil-point (SHPP) spinal needles may be a reason for subarachnoid maldistribution of local anesthetic. A new double-hole pencil-point (DHPP) needle may be preferable because of a theoretic more uniform initial distribution of local anesthetic. METHODS: This was a prospective, double-blinded study of 50 patients randomly selected to have spinal anesthesia using either single-hole 27-gauge (B. Braun, Melsungen, Germany) or double-hole 26-gauge (A.L.B. Medical Inc., U.S.A.) pencil-point needles. The former were inserted with the side port directed caudally and the latter with openings in both caudal and cranial direction. Two milliliters of hyperbaric 0.5% bupivacaine were injected in 1 minute, and sensory and motor block were studied at regular intervals during spinal anesthesia. All patients were interviewed on the first (personal) and the seventh (mailed questionnaire) postoperative day. Furthermore, microscopic inspection of the spinal needles was performed. RESULTS: There were no statistically significant differences in sensory or motor block levels between the two needle types at any time during spinal anesthesia. Likewise, there was no difference in the duration of spinal block. The postanesthetic side effects (headache, backache, pricking, numbness, weakness) were similar in both groups. Light and electron microscopic examination showed resistance of the SHPP needles to tip damage. On the other hand, the DHPP needle tips seemed to be distorted quite frequently, and, even in unused needles, the tip was blunt and asymmetric. CONCLUSION: There was no difference between the spread of analgesia using either SHPP or DHPP spinal needles. The DHPP needles appear to be vulnerable to tip damage from mechanical contact.
The effect of added sodium bicarbonate on plain bupivacaine spinal anesthesia is unknown. Forty patients aged 75 years or older, ASA II or III, undergoing orthopedic lower limb surgery under spinal anesthesia were randomly classified into two groups. Just before injection, either 0.2 ml normal saline (group I) or 0.2 ml 0.42% NaHCO3 solution (group II) was added to 20 ml 0.5% bupivacaine hydrochloride. All patients then received intrathecally 3 ml (14.85 mg) of the bupivacaine solution in the lateral decubitus position. The segmental level of sensory loss was tested using forceps. The median time required to achieve maximal height of the sensory blockade and the median highest level of sensory anesthesia did not differ in the two groups. Alkalinized bupivacaine increased significantly the median times for regression to the T12 and L2 segments by 15 and 25 minutes, and the duration of complete motor block by 15 minutes, as compared to the hydrochloride salt. The clinical importance of such modest prolongations seems limited.
Epidural anesthesia is a widely accepted technique for cesarean section in the preeclamptic patient with normal coagulation. Regional anesthetic techniques avoid the hazards associated with tracheal intubation in the preeclamptic or eclamptic patient. To date, continuous spinal anesthesia in the preeclamptic parturient has not been described. We present a case in which continuous spinal anesthesia was administered for cesarean section in a morbidly obese parturient with severe preeclampsia. Continuous spinal anesthesia was successfully administered without significant hemodynamic consequences or maternal or fetal morbidity. This case suggests that continuous spinal anesthesia may be a viable alternative anesthetic technique for operative delivery in the preeclamptic parturient when epidural anesthesia cannot be established.
BACKGROUND AND OBJECTIVES: The PENCAN 25-gauge spinal needle is a new pencil-point needle with an inner diameter of 0.32 mm resulting in a relatively high cerebrospinal fluid (CSF) flow. The PENCAN 25-gauge needle was tested for ease of identification of a successful dural puncture, the failure rate of spinal anesthesia, and the incidence of postdural puncture headache (PDPH). METHODS: In a multicenter trial, the needle was tested in patients undergoing spinal anesthesia. A questionnaire evaluated the characteristics of the dural puncture. A second questionnaire was used to assess postspinal side effects (PDPH, atypical headache, audiovisual disturbances). RESULTS: In 1,193 patients, dural puncture was evaluated as easy in 85.2%, as moderate in 6.2%, as difficult in 6.7%, and as impossible in 1.9%. Needle performance was assessed as excellent or satisfactory in 96.9%. In 95.9% of patients, CSF appeared within 2 seconds. A perceptible "click" was noticed in 78.4% of patients. In 1.9%, CSF could not be obtained, because of spine deformities, obesity, or bending of the needle. In 1,166 patients, postpuncture complaints were evaluated, involving 635 women (54.5%), 773 patients (66.3%) under the age of 50 years old, and 170 (14.6%) cesarean deliveries. The overall incidence of PDPH was 1.3% (n = 15). A bloodpatch was needed in five patients. After cesarean delivery the incidence of PDPH was 3.4%, all responding to conservative treatment. Atypical headache and isolated audiovisual disturbances occurred in 7.5% and 1.5% of patients, respectively. CONCLUSIONS: A failure rate of 1.9% together with a 1.3% incidence of PDPH were comparable to other 25-gauge pencil-point needles. The rapid appearance of CSF and a perceptible "click" made prompt recognition of successful dural puncture possible.