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The Clinical Use of Small-Dose Tetracaine Spinal Anesthesia for Transurethral Prostatectomy

Chen, Tsung-Ying MD; Tseng, Chia-Chih MD; Wang, Li-Kai MD; Tsai, Tong-Ying MD; Chen, Bing-Shuo MD; Chang, Chuan-Lin MD

doi: 10.1097/00000539-200104000-00040
Regional Anesthesia And Pain Medicine: Research Report
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In a double-blinded study, we compared conventional dose tetracaine (8 mg), small-dose tetracaine (4 mg) with added fentanyl and epinephrine, and small-dose tetracaine (4 mg) with added fentanyl subarachnoid anesthesia. Forty-five patients scheduled for transurethral resection of prostate (TURP) under subarachnoid anesthesia were randomly assigned to Group 1 (8 mg hyperbaric tetracaine), Group 2 (4 mg hyperbaric tetracaine, 10 μg fen-tanyl, and 0.2 mg epinephrine), and Group 3 (4 mg hyperbaric tetracaine, 10 μg fentanyl, and 0.2 mL saline). Evaluations were performed after spinal anesthesia. Subarachnoid block was successful in all patients except one in Group 1, who required general anesthesia by mask. The median peak sensory levels 10 min after the induction of spinal anesthesia in Group 1 was T8, which was significantly higher than Group 2 and Group 3 (P < 0.05). The time of sensory and motor recovery in Group 3 was less than in Groups 1 and 2 (P < 0.05). Hypotension was observed in four patients in Group 1 and none in Groups 2 and 3. We conclude that small-dose 4-mg hyperbaric tetracaine plus 10 μg fentanyl might provide adequate anesthesia and fewer side effects for TURP when compared with the conventional (8 mg) dose.

Department of Anesthesiology, College of Medicine, National Cheng Kung University, Tainan, Taiwan

December 11, 2000.

Implications: Small-dose hyperbaric tetracaine (4 mg with 10 μg fentanyl added) may provide adequate anesthesia and fewer side effects for transurethral resection of the prostate.

Address correspondence and reprint requests to Tsung-Ying Chen, MD, Department of Anesthesiology, College of Medicine, National Cheng Kung University, 138 Sheng-Li Rd., Tainan City, Taiwan 70101, R.O.C. Address e-mail to chenyt@mail.ncku.edu.tw.

There is still disagreement as to what constitutes the ideal anesthesia for transurethral resection of the prostate (TURP). Spinal anesthesia is considered by many anesthesiologists to be the method of choice and, generally, a subarachnoid sensory block extending to the 10th thoracic dermatome is necessary to provide adequate anesthesia (1). However, patients undergoing TURP are often elderly, and sometimes they have compromised cardiac or pulmonary reserve or both. It may be important to limit the distribution of block to reduce adverse hemodynamic and pulmonary effects in such patients. Beers et al. (2), in a prospective study of 23 patients, found that a spinal block higher than L1 (1 mL bupivacaine 0.75% in dextrose 8.5%) is adequate during TURP, but only when bladder pressure is monitored and kept low (<15 mm Hg). However, it is not convenient to monitor intravesical pressure for every TURP patient. The combination of local anesthetics and opiates administered intrathecally has a synergistic effect (3–6). For example, the clinical utility of a small-dose hyperbaric lidocaine-fentanyl spinal technique has been documented for short-duration outpatient laparoscopy (7,8). Therefore, the purpose of this study was to compare the intraoperative conditions and clinical effects of a small-dose tetracaine added to fentanyl spinal anesthetic versus a conventional dose of spinal tetracaine in elderly patients undergoing TURP.

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Methods

After IRB approval and informed consent, 45 patients who were ASA physical status I or II and who were scheduled for TURPs were enrolled in the study. Excluded from this study were patients who had chronic analgesia therapy, scoliosis, history of previous back surgery, diabetes, coagulopathy, or peripheral neuropathies.

Patients received no premedication. Upon arrival at the operating room, patients were administered IV lactated Ringer’s solution 500 mL per bottle kept in line. Every patient had automatic blood pressure, electrocardiogram, and pulse oximetry monitoring. After baseline hemodynamic data were obtained, the patient was positioned in the left lateral decubitus position for spinal blockade. A 25-gauge Quincke needle was introduced at the L3-4 level by using the median or paramedian approach. Patients were assigned randomly, on the basis of a sealed-envelope technique, to receive one of three subarachnoid doses of tetracaine. Group 1 patients received 8 mg hyperbaric tetracaine (20 mg diluted in 3 mL 10% dextrose solution) in 1.2 mL 10% dextrose solution. Group 2 patients received 4 mg hyperbaric tetracaine mixed with 0.8 mL 10% dextrose, combined with 0.2 mL (10 μg) fentanyl and 0.2 mL 0.1% epinephrine. Group 3 patients received 4 mg hyperbaric tetracaine mixed with 0.8 mL 10% dextrose, combined with 0.2 mL (10 μg) fentanyl and 0.2 mL normal saline. Injections were made over a span of 10 to 15 s with cephalad orientation of the spinal needle bevel. Patients were returned to the supine position immediately after completion of the block, and the patient’s legs were wrapped with elastic bandage and placed in the lithotomy position.

Complications during surgery were treated as follows: hypotension (defined as a systolic blood pressure of <90 mm Hg) was treated with 4-mg increments of ephedrine, bradycardia (defined as a heart rate of <50 bpm) was treated with 0.3 mg of atropine, and oxygen desaturation (defined as pulse oximetry oxygen saturation <90% on room air) was treated with oxygen via face mask. If a patient complained about discomfort or pain, midazolam 0.1 mg/kg and meperidine 0.5 mg/kg were administered by the anesthesiologist. In the event of inadequate spinal block (defined as pain severe enough to interfere with the surgical procedure), general anesthesia was induced by mask by using N2O and oxygen (1:1) and 1% isoflurane. Side effects were recorded during operation and recovery.

Hemodynamic data, including systolic pressure, diastolic pressure, and heart rate, were recorded every 2 min in the first 10 min after spinal anesthesia, then every 30 min until motor and sensory recovery. Sensory dermatomal level obtained with pinprick testing was also recorded. The anesthesiologist who did the testing, the surgeon, the patients, and the nursing staff were all blinded to patient group assignment. The highest dermatomal level of sensory blockade, the extent of sensory level at 10 min, duration of sensory blockade (from onset of spinal anesthesia to regression to L4 level), and duration of motor blockade (from onset of spinal anesthesia to Bromage scale 1 [full ability to flex the knees and resist gravity with full movement of the feet]) were recorded.

Statistical analysis was performed with SPSS 9.0 (SPSS, Inc., Chicago, IL) Analysis of variance was applied to analyze demographic data, including age, weight, height, mass of resected prostate tissue, and IV fluid administered during surgery. Intergroup differences of duration of sensory and motor blockade were compared with the Bonferroni correction of the unpaired t-test. Median peak sensory block level was compared with the Mann-Whitney U-test. Side effects were compared with nonparametric Fisher’s exact test. Results were considered significant if P < 0.05.

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Results

There were no differences in age among Groups 1, 2, and 3 (72 ± 5, 73 ± 10, and 69 ± 6 yr, respectively), weight (63 ± 8, 66 ± 10, and 67 ± 11 kg, respectively), height (161 ± 3, 164 ± 5, and 164 ± 9 cm, respectively), or duration of surgery (75 ± 30, 66 ± 24, and 58 ± 21 min, respectively). Study results are summarized in Table 1. The median peak sensory block level after spinal anesthesia was significantly higher in Group 1 (T8) than in other two groups (both T10). Progression of sensory block level in all groups is shown in Figure 1. The duration of both sensory and motor blockade in Group 3 was significantly shorter than Groups 1 and 2 (Table 1). In Group 1, one patient required general anesthesia. However, this case involved a perforation of the bladder during surgery (confirmed by the surgeon). In Group 1, seven patients, in Group 2, three patients, and in Group 3, two patients felt discomfort and requested sedation (Table 2). The incidence of hypotension was significant when Group 1 was compared with Groups 2 and 3. Although not statistically significant, a slightly larger number of patients suffered from bradycardia in Group 1 than in Groups 2 and 3 after spinal anesthesia (Table 2). In Groups 1–3, vital signs, including systolic pressure (141 ± 10, 148 ± 5, and 148 ± 7 mm Hg, respectively), diastolic pressure (76 ± 5, 78 ± 7, and 77 ± 5 mm Hg, respectively), and heart rate (68 ± 5, 66 ± 5, and 74 ± 6 bpm, respectively), were stable throughout surgery and recovery, after treatment of hypotension and bradycardia. But in Group 3, no hypotension occurred; even the intraoperatively administered fluid was significantly less than the other two groups (Table 1). Postoperative follow-up revealed no spinal headaches and no complaints of other adverse effects.

Table 1

Table 1

Figure 1

Figure 1

Table 2

Table 2

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Discussion

Our study demonstrated that the use of small-dose 4 milligrams of hyperbaric tetracaine plus 10 micrograms fentanyl spinal anesthesia provides sufficient anesthesia and fewer side effects in elderly patients undergoing TURP compared with conventional (8 mg) dose spinal anesthesia. The hemodynamic stability of these patients was demonstrated by the small amount of IV fluid administered and the absence of significant hypotension. There were also fewer other side effects seen in these patients, although this result did not reach statistical significance.

The prostate is innervated by both the parasympathetic and the sympathetic division of the autonomic nervous system. Parasympathetic visceral efferent preganglionic fibers arising from S2 through S4 enter the plexus by way of the pelvic splanchnic nerve. The sympathetic component of the pelvic plexus originates from the thoracolumbar center (T11 through L2) and enters the plexus via the hypogastric nerve, the sacral sympathetic chain (S4 through S5), and the inferior mesenteric plexus (9). Conventionally, a subarachnoid sensory block extending to the T10 is necessary to provide adequate anesthesia during TURP (1). In 1994, Beers et al. (2) reported that a midlumbar block level (L1) provided adequate anesthesia for TURP. However, bladder distension elicited pain under a low or intermediate block. They suggested monitoring and controlling bladder pressure during TURP for block levels lower than T10 (2).

In our results, the addition of intrathecal fentanyl provided successful surgical anesthesia with a smaller dose of tetracaine during TURP. These results are consistent with those studies demonstrating that intrathecal opioids enhance analgesia when added to subtherapeutic doses of local anesthetic (6–8). Animal models have also shown potentiation of analgesic effect when small doses of opiate are combined with local anesthetic (10). Intrathecal opioids appear to produce analgesia by inhibition of synaptic transmission in nociceptive afferent pathways (Aδ and C fibers) (6,11). We theorize that blockade of Aδ and C afferents allowed the small-dose hyperbaric tetracaine (4 milligrams) to maintain surgical anesthesia during regression of spinal anesthesia. Blockade of Aδ and especially C fibers by intrathecal fentanyl may explain the increased dermatomal spread and tolerance of pain elicited by bladder distension.

The addition of intrathecal fentanyl to spinal anesthesia has been shown to improve the quality of block, increase duration of sensory block, and provide postoperative analgesia without affecting motor function (7,8,12). Opioids added to intrathecal local anesthetics also reduce the incidence of lower extremity tourniquet pain (13). Adding opioids to epidural local anesthetics alleviates visceral discomfort during cesarean delivery (14). By increasing the spread or intensity of the subarachnoid block, intrathecal fentanyl may improve the efficacy of small-dose spinal block (12,15). Intrathecal opioids appear to produce analgesia by inhibition of synaptic transmission in nociceptive afferent pathways (Aδ and C fibers) (6,15). Our results show that intrathecal fentanyl added to tetracaine has a practical application in TURP surgery.

Epinephrine is frequently added to local anesthetics to augment spinal anesthesia. It produces vasoconstriction that can decrease vascular absorption of local anesthetic and increase the concentration of local anesthetic in the spinal cord (14,15). Epinephrine may also directly produce analgesia (16–18). The addition of epinephrine to tetracaine (6 milligrams) decreases the incidence of pain during surgery and increases tetracaine’s effectiveness as a spinal anesthetic (19). Our results showed that 4 milligrams of tetracaine, 10 micrograms of fentanyl, and 0.2 milligrams of epinephrine produce almost the same duration of blockade as 8 milligrams of tetracaine.

Sympathetic efferent blockade results in a reduction in both cardiac preload and afterload (20). We found that there was an increased incidence of hypotension and bradycardia in the tetracaine (8 milligrams) group than in the added fentanyl groups. Small-dose tetracaine (4 milligrams) with 10 micrograms fentanyl (and 0.2 milligrams epinephrine or not) may provide better hemodynamic stability in elderly patients undergoing TURP. Although not statistically significant, the rate of other side effects, such as bradycardia, nausea, vomiting, and shivering, were also less in the 4 milligrams tetracaine with fentanyl groups.

In conclusion, we have shown that a subarachnoid block with small-dose tetracaine 4 milligrams plus 10 micrograms fentanyl may provided adequate analgesia during TURP. This technique may be useful in clinical application for elderly patients undergoing TURP.

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