- Email: [email protected]
Spinal opioids in the management of acute and postoperative pain
138
Joumal
Vol. 5 No. 3 June 1990
of Pain and Sympna Management
SpinalOpioids ~IIthe Management of Acute and PostoperativeP; L. Brian Ready,
MD
Department of Anesthesiology, Universi~ of Washington, Seattle, Washington
Abstract
The we of spinal opioids in the manag-: qf acute pain is now wideb accepted. Th,e dkve&ment of acute pain services bus provided standardized approaches to the management of thti modality This article dixusses technical considerations, monitoring, and beqits of this approach. J Pain Symptom Manage 1990;5:138-145.
Key words Spincrl opioi& acute pain, PostoperQtivepain, acute pain services
In 1979, Wang reported pain relief using subarachnoid morphine in cancer patients,’ and Behar achieved the same result ‘injecting the drug into the epidural space.2 Subsequent . auttiois ~d%xxx! that selective, long-duration analgesia was possible using these techniques in a variety of clinical settings. It soon became clear, however, that a number of side effects can occur, which range from the annoying (sedation, pruritus, nausea, vomiting, or urinary retention) to life-threatening (early and delayed respiratory depression). Notwithstanding, extensive clinical experience has now established that the benefits of spinal opioids can be obtained with a high degree of safety, given proper attention to education of ward nurses, patient selection, appropriate choice of drugs and their dosage, adequate pa.tient monitoring, and effective treatment of side effects.
A&ess r@nt rep& to: L. Brian Ready,, MD, FRCP(C), Direaor, Acute Pain Service, Department of Auesthesiology, University of Washington, Seattle, WA 98195.
@ U.S. Cancer Pain Relief Committee, 1990 Published by Elsevier. New York, New York
Spinal opioids have been used to control pain following a wide variety of surgical procedures. Subarachnoid opioids have the appeal of ease of administration, either at the time of spinal local anesthetic injection for surgical anesthesia, or as a separate technique when general anesthesia is administered. Since most clinicians give a single injection, this technique is best applied when surgical pain is expected to be of relatively short duration. Many patients will remain comfortable for 24 hs or more after a single injection of subarachnoid morphine. Some of these will require no additional pain relief during their postoperative course, or they will find their remaining pain easily managed by ordl analgesics. The epidural route has been used much more extensively for postoperative pain control. Reasons include popularity of the technique alone or in combination with light general anesthesia during surgery, willingness to leave an epidural catheter in place for extended periods to maintain analgesia, familiarity with postoperative analgesia using local anesthetics, and freedom from the risk of postlumbar puncture head-
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199G
Management of Acute and P&operative Pain
ache. Caudal epidural opioids have also been used effectively.3 Several reports regarding the use of epidural opioids for postoperative pain control are of special note. Stenseth and colleagues4 published a prospective report of the efficacy and side effects of ep?dural morphine in 1085 patients after thoxacic, abdominal, urologic, or orthopedic surgery. This large experience from a single institution provides a wealth of observations that are instructive to the clinician con.ternplating the use of epidural opioiids. In a randomized .&uble-blind stu.dy by Rawal and colleagues5 of obese patients undergoing gastroplasty for weight reduction, the effects of intramuscular and epidural morphine were compared with respect to analgesia, ambulation, gastrointestinal motility, early and late pulmonary function. duration of hospitalization, and occurrence of deep-vein thrombosis in the postoperative period. With a protocol designed to provide adequate analgesia by either route, the average dose of intramuscular morphine was up to seven times greater than that required by the epidural route. Patients receiving Lpidural morphine reported superior analgesia, ambulated rooner, h&d fewer pulmonary complications, had earlier return of bowel function, and were discharged from hospital earlier than patients receiving intramuscular morphine. Yeager and colleagues” randomized high-risk surgical patients to two groups: the first received general anesthesia and conventional postoperative analgesia (ie, intraK ::isular [IM] or intravenous [IV] opioids.), while the second group received combined epidurapgeneral anestnesia and epidural opio~&. for postoperative pain. Mortality, overall complication rate, infection rate, time to extubation, and hospital costs were significantly lower in the epidural grouP* Although not as effective as regional analgesia with local anesthetics for controlling pain associated with vaginal delivery, spin.1 opioids for control of pain following cesari.an section are widely used. These may be offered when spinal or epidural ane.%hesia is chosen for surgery. Although most reports focus on the latter application, good results have also been reported with the subarachnoid route.’ Pain after vaginal delivery originating from a large episiotomy or perineal tear may als,o be managed by spinal opioids.
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FQstQperative E*urd
t’@ideAnalgesia Patients undergoing a variety of surgical procedures may benefit from the superior analgesia possible with spinal opioids. This is particularly true in conditions in which uncontrolled pain may compromise pulmonary function, leading to atelectasis and pneumonia. Examples include patients with rib fractures, and pain resulting from abdominal and thoracic incisions. Patients with underlying medical conditions, such as respiratory insufficiency or obesity, may derive particular benefit. In patients receiving regional anesthesia for surgery, it is particularly easy to offer spinal opioids for postoperative pain. For example, a single dose of morphine may be added to the local anesthetic solution chosen for subarachnoid injection prior to transurethral prostatectomy. Similarly, an opioid may be injected repeatedly or infused continuously into a catheter that was placed in the epidural space co provide anesthesia for patients undergoing a wide variety of surgical procedures (eg, cholecystectomy, hip surgery, thoracotomy). If general anesthesia is used for surgery, an epidural catheter may be placed any time in the postoperative period, should pain control by conventional methods prove inadeqlaate. Because correct placement of fhe catheter in the epidural space is essential for postoperative analgesia, neural blockade with a local anesthetic should be demonstrated prior to opioid injection. An adhesive transparent dressing over the catheter insertion site facilitates daily inspection. To minimize the risk of accidental epidural injection of drugs intended for intravenous administration,8 we place a brightly colored intermittent injection cap (Product no. INlOOO, Burron Medical, Inc., Bethlehem, PA) on the epidural catheter connector and a brightly colored label that reads “EPIDURAL CATHETER” 311 the catheter near the injection cap. Micropore filters are used on intrathecal and epidural catheters by some practitioners. They may reduce the risk of contamination by pathogenic organisms and prevent injection of foreign material such as glass particles. However, infections have not proved to be a problem,
Ready
140
even when filters are not used. In additio; i, aspiration of epidural catheters to check for intravenous or subarachnoid migration is made difficult with some of these devices. The initial epidural narcotic dose should be given in the operating room at leas : hr before the expected completion of surgery. It appears to be easier to establish good pain control immediately after surgery than to treat severe pain once it is establLhed.g Standard Orders (Appendix A) are recommended. These should include a notation of the initial opioid dose, an order for subsequent doses, monitoring instructions, orders for the treatment of side effects, and definition of the physician to call if necessary. Our ward nurses have been provided with extensive in-service training to permit them to inject opioids safely into epidural catheters. Our Standard Orders provide for a fixed opioid dose with a variable injection interval (eg, preservative-free morphine 4 mg every 6-12 hr). This gives the nurse some discretion in determining how frequently the dose will be administered. Standard orders should be tailored to the patient nursing practices, and medical population, preferences found in each institution.
Table 1 lists a number of opioids, suggested dose ranges, expected latency, and duration of analgesia. Doses necesssay to produce analgesia and their duration of effect will vary considerably from one patient to another depending on age, medical condition, site of injection, type
Journal of Pain and SymptomManagement
of pain, and other factors. Incorporating some of these factors, Table 2 lists suggested startir’g doses of epidural morphine, the most wide!, used opioid for incisional I.ain. Thtt recommended doses are only rough guideline:,. A dynamic ongoing assessment of adequacy of pain relief for a particular patient, with changes in dose or frequency of injection as necessary, is the logical approach. Preservative-free morphine preparations have been used in a wide range of concentrations with no app:irent diZference in efficacy. We do not dilute the commercially available 0.1% solution. The addition of epinephrine to morphine is not recommended. Although most experience with morphine has involved intermittent injection, it has been used with success as a continuous infusion. Effective doses in our experience have ranged from less than 0.1 to 1.5 mg/hr. Elderly patients in particular may need remarkably small doses of epidural morphine. In reviewing our experience treating women after abdominal hysterectomy, we found a significant negative correlation between age and effective dose of epidural morphine needed per 24 hr. The relationship can be expressed by the following equation: effective 24-hr dose (mg) = H-age (0.15).l” A lipophilic agent such as fentanyl is useful when rapid onset of analgesia is important. Intermittrsnt epidural boluses of 50-75 p.g can be used to achieve analgesia promptly in the immediate postoperative period if the initial epidural morphine dose is not adequate. Used as the sole narcotic, a 25- 100~pg epidural bolus is
Table I Characteristics of Postoperative Analgesia Achieved with Spinal Opioids Drug
Dose* (mg)
Onset (min)
Duration** (hr)
Epidural Morphine Meperidine Methadone H ydromorphone Diamorphine Fentanyl
l-10 PO- 160 l-16 l-2 4-6 0,025-O. 15
30 5 10 15 5 5
6-24 6-8 6-10 lo-16 12 4-6
0.1-0.5 IO-30 l-2
5 ? ?
8-24 10-30 20
Subatachnoid Morphine Meperidine Diimorphine
*Low doses may be effective when administered to the elderly or when injected in the thoracic region. **Duration of analgesia varies widely; higher doses produce longer duration.
Vol. 5 No. 3 June 1990
Management of Acute and Postoperative Pain
Table 2 Starting Dose (mg) of Epidural Morphine for Incisional Pain*
Patieni
AiF (yr) 15-44 45-65 66-75 76+
Thoracic Surgery Nonthoracic Surrrerv (Lumbar or Thoracic Lumbar Caudal Catheter) Catheter Catheter ”
5 4 3 2
,
4 3 2 1
6 5 4 2
These doses should only be considexd as guidelines. Safe and effective doses for individual patients may vary considerably. *These doses are based on the USC’ of undiluted 0.1% preservative-free morphine.
fol.lowed by a continuous infusion of 25-150 pglhr with an accurately calibrated pump.
Until it is possible to identify and eliminate the factors that occasionally lead to severe respiratory depression in patients receiving spinal opioids, it must be assumed that all patients offered these techniques are at risk. The subarachnoid route may carry higher risk than the epidural route, although the relative risk of the two approaches has not been systematically addressed. However,, because a catheter in tht epidural space can migrate through the dura at any time, equal vigilance must be exercised with both techniques. Patiems at greatest risk a1.e those in the immediate postoperative period (< i 2 hr, see later). Tti prevent serious injury or death, there is no substitute for a high level of vigilance. This may be provided by a nurse trained to check rate and depth of respiration, as well as generai status and level of consciousness, at frequent intervals. Respiratory monitors that sound an alarm if ventilation is not detected may augment this process, but should not be viewed as substitutes for alert, well-trained human observers. Intensive care faci!tties are well suited to t%; level of monitoring and should be used for patients at special risk (advanced age, serious underlying conditions, extensive surgery). However, the expense and limited availability of the?.e facilities render them impractical for routine use. A “step-down unit,” intermediate between intensive care and a regular ward with
I41
regard to the level of monlitoring and nursing care available, is an appealing alternative. \EJe have demonstrated that with extensive nursing education, careful patient selection, frequent monitoring of ventilation, protocols for immediate treatment of complications, and immediate availability of medical personnel, spinai opioids can be offered safely on cozlventionai hospital wards. Delegation of all responsibility for pain control to one group of physicians within an institution can minimize errors of conflicting or duplicate orders, or inadvertent administration
of parenteral
opioids to patients
receiving intraspinal opioids. This is particularly impo.:Lant given that such concurrent dosing represents a frequently cited correlate of lifethreatening levels of respiratory depression (see later).
Under some circumstances, spinal opioids are best avoided. These include (a) inexperience in
performing lumbar puncture or epidural block-particularly in the cervical or thoracic regions, (b) inadequate nursing education ar monitoring capabilities, (c) infection at the site of needle insertion, and (d) known opioid allergies. It remains controversial whether these techniques should be used in patients with coagulopathies, including these receiving anticoagula:it therapy. Decisions should be based on the relative risks and benefits for ind.ividual patients. Ct.~~.lications
and
Their
Treabnmd
Depression. Early respiratory depression, occurring in the first 2 hours follow-
h!es@m
ing injection, is a feature only of epidural opioid administration and is a result of vascular up+dke and redistribution (ie, the same mechanism that follows intramuscular injection). Qelayed respiratory depression occurring 6- 12 hr after subarachnoid or epidural injection is likely the consequence of rostra1 spacad of opioid in cerebrospinal fluid. The target site is thought to he the respiratory center located superficially in the floor of the fourth ventricle. The actual incidence of this event is ncmtknown and depends on a number of factors, including the
population studied, how they are monitored, and the definition of respiratory depression. In a large, multiinstitutional Swedish question-
l?mfy
142
naire survey, the incidence of “depression reIn a quiring naloxone” was 0.25%-0.40%.11 questionnaire survey of 74 U.S. institutions, the incidence of “respiratory insufficiency” was 1.9%2.3%.‘* In a prospective study of 1,085 patients in a single institution, the incidence of “respiratory depression” was 0.9%.4 It is not actually known wheLher the risk of severe respiratory depression is greater after the spinal administration of analgesic concentrations of opioids or more conventional systemic routes. It has, for example, been reported that 860 hospitalized patients receiving morphine orally or parenterally (IV, IM, subcutaneously [SC]) demonstrated a 0.9% incidence of “life-threatening ,respiratory depression.“*3 The risk of delayed respiratory depression after spinal opioids appears to bc greatest early in the course of therapy. There ase no reported cases of this complication occurring later than 24 hr after administration of the initial dose of drug. Consistently impressive among predisposing risk factors are advanced age, concomitant use of systemic opioids or other central nervous system (CNS) depressants, and extensive surgery. Therefore, large doses of perioperative opioids, long-acting sedatives, and postoperative parenteral opioids should be avoided or used with caution in patients receiving spinal opioids. Respiratory rate alone is not an adequate indicator of ventilatory status in volunteers” or in postoperative patients’” receiving spinal opioids. A more global assessment is necessary, partkulariyduring the first 24 hr of treatment. This should include assessment of level of consciousness, since increasing sedation (presumably due to central drug effect and CO, narcosis) has been noted with advanced respiratory depressionP Healthy volunteers breathing CO,
T&ble3 Bxarnple of Bedside Sedation Scale Sedation 0 (None) 1 (Mild)
Description
2 (Moderate)
Patient alert Occasionally drowsy; easily aroused Frequently drowsy; easily
3 (Severe) S (None)
aroused Somnolent; diicult to arouse Normal skep; easily aroused
Jmnul of Pa& ad Sympnn Management
mixtures have h~en observed to lose consciousness at pCOp levels of -80 mm Hg.rb Every patient receiving spinal opioids whose level of consciousness deteriorates unexpectedly should be assumed to have respiratory depression until disproved by arterial blood gas analysis. A simple bedside sedation scale (Table 3) has proved to be a useful clinical tool in detecting respiratory depression in our practice. The immediate treatment of severe respiratory depression is support of ventilation. Equipment to deliver oxygen with positive pressure must be readily available, and personnel in the area must be familiar with its use. Naloxone 0.4 mg intrarenously will usually restore adequate spontaneaus ventilation, but, given the short half-life of the drugs relative to the spinal narcotic, repeated doses are sometimes necessary. This drug should be immediately available. Pru&us. This symptom is common but seldom bothersome. The incidence is particularly high in obstetric patients. Itching may be generalized or localized, with the face beir:g Lhc: most common site. Pruritus is seen both with opioids containing preservatives and preservative-free preparations. Although probably not caused by histamine release, antihistamines will often provide symptomatic relief. Naloxone is consistently effective but may have to be administered frequently or infused. Urinary Retentimt. The incidence of this prob. lem has been higher in volunteers than in patients, and higher in males. Naloxone may help prevent or reverse urinary retention, but doses approaching those that antagonize analgesia may be needed. Some patients will require bladder catheterization. Nausea and Vomiting. These distressing symptoms are believed to be the result of rostra1 spread of the opioid in the cerebrospinal fluid to the vomiting center and the chemoreceptor trigger zone located superficially in the floor of the fourtih ventricle. Relief is frequently possible with antiemetics, but these may also produce unwanted sedation or even contribute to the risk of respiratory depression.” Transdermal scopolamine patches applied to the mastoid area have beeu effective in many of our patients. A continuous naloxone infusion is usually effective and should be considered
Vol. 5 No. 3 June 1990
Management of Acute and Postoperative Pain
when nausea and vomiting do not resolve with other measures. Se&&m. When any patient receiving spinal opioids appears excessively sedated, hypercarbia should be suspected and, if present, treated. The possible contributing role of other drugs, such as antiemetics, should also be considered. Sedation produced by spinal opioids, rarely a significant problem with moderate drug doses, may be the result of rostra1 spread of the drug in cerebrospinal fluid. Pharmacologic treatment is seldom indicated, but physostigmine 1 mg intravenously may be effective.18
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whose pain was not adequately co;ltrolled with epidural opioids alone. In addition to the monitoring used for patieuts receiving only epidural opioids, frequent measurement of blood pressure and sensory and motor examinaG.,n is recommended. A sample of Standard Orders for epidural local anestheticiopioid mixtures is provided in Appendix B.
l. Wang JK, Nauss LA, ThomasJE.
Pain r&ef by
intrathecally applied morphine in man. Anesthesiology 1979;50:149-151.
Efkkd Awsthti
Local id iWktures
Although continuous infusion of local anesthetics in usual clinical concentrations produces effective analgesia, it may also produce undtsirable effects, including hypotension, sensory and motor block, nausea, and urinary retention. In an attempt to achieve postoperative analgesia free of side effects, combinations of very dilute local anesthetics and opioids infused continuously through an epidural catheter have been advocated. Nociceptive pathways may be in..c’rrupted at different sites with the two drbldsnamely., the nerve axon with the local anesthetic and the spinal opioid receptor with the opioid. Bupi.vacaine appears to be well suited to ;his application because dilute solutions product minimal motor block. Cullen and colleagues’g used a mixture OFbupivacaine 0.1% plus morphine 0.0 1% infused at a rate of 3-4 mL/hr and compared it to the same concentrations of bupivacaine or morphine infused alone. Pain scores in the morphine and combination group were superior to the bupivacaine group. The only significant difference in side effects was a higher incidence of pruritus in both morphine groups. Hypotension or difficulty witla ambulation were not apparent in the groups receiving bupivacaine. It remains unclear whether the combination of epidural opioids and local anesthetics are superior for certain patients. The author has used a combination of fentanyl 0.0002% (2 pg/mL) plus 0.0625% bupivacainc infused at a rate of 8-20 mL/hr with good effect in patients with known tolerance to opioids and in patients
2. Behar M, Olshwang D, Magora F, Davison JT. Epidural morphine in the treatment of pain. Lancet 1979;1:527-529. 3. Boskovaki N, Lei,inski A, Xuered J, Mercieca V.
Gaudal epidural morphine for post-operative pain relief. A Plaesthesia 1980;35:67-68. 4. Stenseti, R. Sellevoiid 0, Breivik H. Epidural morphine for ijostoperative pain: experience with 1085 patients. Acta Anaesthesiol Stand 1985;29:148- 156. 5. RawaI N, et al. Comparison of intramusculat and epidural morphine for postoperative analgesia in the grossly obese: influence on postoperative ambulation and pulmonary function. Anesth Analg 1984;63: 583-592. 6. Yeager MP, Glass DC, Neff RK, Brinck-Johnsen T. EpiduraI anesthesia and analgesia in high-risk surgical patients. Anesthesiology 1987;66:729-736. 7. Chadwick HS, Ready LB. Intrathecal and epidural morphine sulfate for postcesarean analgesia: a clinical comparison. Anesthesio!ogy 1988;68:925-929. 8. Lin D, Becker K, Shapiro HM. Neurologic changes foiIowing epidural injection of potassium chloride and diazepam: a case report witt laboratory correlations. Anesthesiology 1986;65:210-212. 9. Chambers WA, Sinclair CJ, Scott DB. Extradural morphine for pain after surgery. Br J Anaesth 1981;53:921-925. 10. Ready LB, Chadwick HS, Ross B. Age predicts effective epidural morphine dose after abdominal hysterectomy. Anesth Analg 1987;66:1215- 1218. 11. Custafsson LL, Schildt B, Jacobsen KJ. Adverse effects of extradural and intrathecal opiates: repart of a nationwide survey in Sweden. Br J Aalaesth 1982;54:479-486. 12. Mott JM, Eisele JH. A survey of monitoring practices foIlowing spinal opiate administration. Anesth Analg 1986;65:Sl-S170. 13. Miller RR, Greenblatt DJ, eds. Drug effects in hospitalized patients. New York: John Wiley and Sons, 1976:151-152.
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Journal of Pain and Symptom Management
14. Camporesi EM, et al. Ventilatory COs sensitivity after intravenous and epidural morphine in volunteem Anesth Analg 1983;62:633-640.
17. Cohen SE, Rothblatt AJ, Albright GA. Early respiratory depression with epidural opioid and intravenous droperidol. Anesthesiology 1983;59:559560.
15. Rawal N, Wattwil M. Respiratory depression after epidural morphine: an experimental and clinical study. Anesth Analg 1984;63:8-14.
18. Shulman MS, Sandler A, Brebner J. The reversal of epidural morphine induced somnolence with physostigmine. Can Anaesth Sot J 1984;31:678-680.
1E Sechzer PH, et al. Effects of CO2 inhalation on ‘al pressure, ECG and plasma catecholamines 17-OH corticosteroids in normal man. J Appl Phyciol 1960;15:454-458.
19. Cullen ML, et al. Continuous epidural infusion for analgesia after major abdominal operations: a randomized, prospective, doable-blind study. Surgery 1985;98:718-728.
Sample Epidural Opioid Standard Orders MgTime 1. Operating room dose: Drug Drug for continuing epidural analgesia: 2. mg every 6-12 hr A. PF morphine (1 mg/mL) B. Fentanyl(l0 pg/mL normal saline) Infuse -ClgrmL) per hr concentration _ C. Other: Druginterval DoSeFor inadequate analgesia with prescribed dose above, give fentanyl50 Fg (1 .O mL) into epidural catheter every 3. Shrprn 4. Maintain IV access (drip, heparin lock) for 24 hr after last dose of epidural opioid 5. Naloxone 0.4 mg at bedside 6. No opioids or other CNS depressants to be given except as ordered by the Acute Pain Service 7. Monitoring: Resp!.ratory rate and sedation scale every 1 hr for first 24 hr 8. Treatment of side effects: A. Call Acute Pain Service for sedation scale = 3 B. Call Acute Pain Service for RR C 8 per min C. Naloxone 0.4 mg IV stat for sedation scale = 3 plus RR C 8 per min; call Acute Pain Service D. Metoclopramide 10 mg IV q6h prn for nausea/vomiting. In aa’ditiun,ifage <6Oyears, transdermal scopolamine patch to either mastoid area for nausea/vomiting; change every 72 hr prn E. Naloxone 0.1 mg IV for severe itching; MR every 10 min x 5 F. For urinary retention, “in and out” bladder catheter For inadequate analgesia or other problems related to epidural, call Acute Pain Service
Vol. 5 No. 3 June 1990
Management of Acute and Postoperative Pain
Sample Orders for Epidural Local AnestheWOpioid
Infusions
hr 1. Infusion begun at: 2. Drug for continuing epidural analgesia: Bupivacaine l/16% (0.625 mg/mL normal saline) plus Fentanyl-2 pg/mL normal saline or PF morphine-O. 1 mg/mL normal saline or concentration Other: Local anesthetic _ Opioid _ concentration mUhr Infuse at 3. Fentanyl50 pg (1 .O mL) into epidural catheter every 3 hr prn for inadequate analgesia with prescribed dose above 4. Place at bedside: A. Ephedrine 25 mg/5 mL (ie 5 mg/mL) B. Naloxoxte 0.4 mgll mL 5. Maintain IV access (drip or heparin lock with flushes) 6. No opioids or other CNS depressants to be given except as ordered by the Acute Pain Service 7. Monitoring: A. BP/pulse (via automatic BP monitor) from start of infusion every 30 min x 3 hr; then every 1 hr B. Resp rate & sedation scale every 1 hr for first 24 hr; then every 2 hr C. Sensory level and motor function every 2 hr while awake D. Postural BP/P prior to first ambulation 8. PRN treatments: A. Nalox~e ri.4 mg IV stat for sedation scale = 3 plus RR C 8 per min; call Acute Pain Service B. Metoclopramide 10 mg IV every 6 hr pm for nausea/vomidng; in addition, if age <60 yr, Transdermal !$opolamine patch to either mastoid area; change every 72 hr pm C. Diphenhydramine 25 mg IV every 6 hr pm for severe itching D. For urinary :~ention, “ia and out” Madder c, theter prn E. Triazolam 0.125 mg every hr prc; MR X 1 9. Notify Acute Pain Service for the following: lmin A. BP< _mmHgand/orP<_ B. RR < 8lmin C. Sedation scale = 3 D. Numbness above nipples and/or inability to bend knees E. Posture BP drop > 15 mm Hg and/or HR increase >20/min F. Inadequate analgesia or other problems related to epidural
Joumal
Vol. 5 No. 3 June 1990
of Pain and Sympna Management
SpinalOpioids ~IIthe Management of Acute and PostoperativeP; L. Brian Ready,
MD
Department of Anesthesiology, Universi~ of Washington, Seattle, Washington
Abstract
The we of spinal opioids in the manag-: qf acute pain is now wideb accepted. Th,e dkve&ment of acute pain services bus provided standardized approaches to the management of thti modality This article dixusses technical considerations, monitoring, and beqits of this approach. J Pain Symptom Manage 1990;5:138-145.
Key words Spincrl opioi& acute pain, PostoperQtivepain, acute pain services
In 1979, Wang reported pain relief using subarachnoid morphine in cancer patients,’ and Behar achieved the same result ‘injecting the drug into the epidural space.2 Subsequent . auttiois ~d%xxx! that selective, long-duration analgesia was possible using these techniques in a variety of clinical settings. It soon became clear, however, that a number of side effects can occur, which range from the annoying (sedation, pruritus, nausea, vomiting, or urinary retention) to life-threatening (early and delayed respiratory depression). Notwithstanding, extensive clinical experience has now established that the benefits of spinal opioids can be obtained with a high degree of safety, given proper attention to education of ward nurses, patient selection, appropriate choice of drugs and their dosage, adequate pa.tient monitoring, and effective treatment of side effects.
A&ess r@nt rep& to: L. Brian Ready,, MD, FRCP(C), Direaor, Acute Pain Service, Department of Auesthesiology, University of Washington, Seattle, WA 98195.
@ U.S. Cancer Pain Relief Committee, 1990 Published by Elsevier. New York, New York
Spinal opioids have been used to control pain following a wide variety of surgical procedures. Subarachnoid opioids have the appeal of ease of administration, either at the time of spinal local anesthetic injection for surgical anesthesia, or as a separate technique when general anesthesia is administered. Since most clinicians give a single injection, this technique is best applied when surgical pain is expected to be of relatively short duration. Many patients will remain comfortable for 24 hs or more after a single injection of subarachnoid morphine. Some of these will require no additional pain relief during their postoperative course, or they will find their remaining pain easily managed by ordl analgesics. The epidural route has been used much more extensively for postoperative pain control. Reasons include popularity of the technique alone or in combination with light general anesthesia during surgery, willingness to leave an epidural catheter in place for extended periods to maintain analgesia, familiarity with postoperative analgesia using local anesthetics, and freedom from the risk of postlumbar puncture head-
-Vol. 5 No. 3June
199G
Management of Acute and P&operative Pain
ache. Caudal epidural opioids have also been used effectively.3 Several reports regarding the use of epidural opioids for postoperative pain control are of special note. Stenseth and colleagues4 published a prospective report of the efficacy and side effects of ep?dural morphine in 1085 patients after thoxacic, abdominal, urologic, or orthopedic surgery. This large experience from a single institution provides a wealth of observations that are instructive to the clinician con.ternplating the use of epidural opioiids. In a randomized .&uble-blind stu.dy by Rawal and colleagues5 of obese patients undergoing gastroplasty for weight reduction, the effects of intramuscular and epidural morphine were compared with respect to analgesia, ambulation, gastrointestinal motility, early and late pulmonary function. duration of hospitalization, and occurrence of deep-vein thrombosis in the postoperative period. With a protocol designed to provide adequate analgesia by either route, the average dose of intramuscular morphine was up to seven times greater than that required by the epidural route. Patients receiving Lpidural morphine reported superior analgesia, ambulated rooner, h&d fewer pulmonary complications, had earlier return of bowel function, and were discharged from hospital earlier than patients receiving intramuscular morphine. Yeager and colleagues” randomized high-risk surgical patients to two groups: the first received general anesthesia and conventional postoperative analgesia (ie, intraK ::isular [IM] or intravenous [IV] opioids.), while the second group received combined epidurapgeneral anestnesia and epidural opio~&. for postoperative pain. Mortality, overall complication rate, infection rate, time to extubation, and hospital costs were significantly lower in the epidural grouP* Although not as effective as regional analgesia with local anesthetics for controlling pain associated with vaginal delivery, spin.1 opioids for control of pain following cesari.an section are widely used. These may be offered when spinal or epidural ane.%hesia is chosen for surgery. Although most reports focus on the latter application, good results have also been reported with the subarachnoid route.’ Pain after vaginal delivery originating from a large episiotomy or perineal tear may als,o be managed by spinal opioids.
In-g
139
FQstQperative E*urd
t’@ideAnalgesia Patients undergoing a variety of surgical procedures may benefit from the superior analgesia possible with spinal opioids. This is particularly true in conditions in which uncontrolled pain may compromise pulmonary function, leading to atelectasis and pneumonia. Examples include patients with rib fractures, and pain resulting from abdominal and thoracic incisions. Patients with underlying medical conditions, such as respiratory insufficiency or obesity, may derive particular benefit. In patients receiving regional anesthesia for surgery, it is particularly easy to offer spinal opioids for postoperative pain. For example, a single dose of morphine may be added to the local anesthetic solution chosen for subarachnoid injection prior to transurethral prostatectomy. Similarly, an opioid may be injected repeatedly or infused continuously into a catheter that was placed in the epidural space co provide anesthesia for patients undergoing a wide variety of surgical procedures (eg, cholecystectomy, hip surgery, thoracotomy). If general anesthesia is used for surgery, an epidural catheter may be placed any time in the postoperative period, should pain control by conventional methods prove inadeqlaate. Because correct placement of fhe catheter in the epidural space is essential for postoperative analgesia, neural blockade with a local anesthetic should be demonstrated prior to opioid injection. An adhesive transparent dressing over the catheter insertion site facilitates daily inspection. To minimize the risk of accidental epidural injection of drugs intended for intravenous administration,8 we place a brightly colored intermittent injection cap (Product no. INlOOO, Burron Medical, Inc., Bethlehem, PA) on the epidural catheter connector and a brightly colored label that reads “EPIDURAL CATHETER” 311 the catheter near the injection cap. Micropore filters are used on intrathecal and epidural catheters by some practitioners. They may reduce the risk of contamination by pathogenic organisms and prevent injection of foreign material such as glass particles. However, infections have not proved to be a problem,
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even when filters are not used. In additio; i, aspiration of epidural catheters to check for intravenous or subarachnoid migration is made difficult with some of these devices. The initial epidural narcotic dose should be given in the operating room at leas : hr before the expected completion of surgery. It appears to be easier to establish good pain control immediately after surgery than to treat severe pain once it is establLhed.g Standard Orders (Appendix A) are recommended. These should include a notation of the initial opioid dose, an order for subsequent doses, monitoring instructions, orders for the treatment of side effects, and definition of the physician to call if necessary. Our ward nurses have been provided with extensive in-service training to permit them to inject opioids safely into epidural catheters. Our Standard Orders provide for a fixed opioid dose with a variable injection interval (eg, preservative-free morphine 4 mg every 6-12 hr). This gives the nurse some discretion in determining how frequently the dose will be administered. Standard orders should be tailored to the patient nursing practices, and medical population, preferences found in each institution.
Table 1 lists a number of opioids, suggested dose ranges, expected latency, and duration of analgesia. Doses necesssay to produce analgesia and their duration of effect will vary considerably from one patient to another depending on age, medical condition, site of injection, type
Journal of Pain and SymptomManagement
of pain, and other factors. Incorporating some of these factors, Table 2 lists suggested startir’g doses of epidural morphine, the most wide!, used opioid for incisional I.ain. Thtt recommended doses are only rough guideline:,. A dynamic ongoing assessment of adequacy of pain relief for a particular patient, with changes in dose or frequency of injection as necessary, is the logical approach. Preservative-free morphine preparations have been used in a wide range of concentrations with no app:irent diZference in efficacy. We do not dilute the commercially available 0.1% solution. The addition of epinephrine to morphine is not recommended. Although most experience with morphine has involved intermittent injection, it has been used with success as a continuous infusion. Effective doses in our experience have ranged from less than 0.1 to 1.5 mg/hr. Elderly patients in particular may need remarkably small doses of epidural morphine. In reviewing our experience treating women after abdominal hysterectomy, we found a significant negative correlation between age and effective dose of epidural morphine needed per 24 hr. The relationship can be expressed by the following equation: effective 24-hr dose (mg) = H-age (0.15).l” A lipophilic agent such as fentanyl is useful when rapid onset of analgesia is important. Intermittrsnt epidural boluses of 50-75 p.g can be used to achieve analgesia promptly in the immediate postoperative period if the initial epidural morphine dose is not adequate. Used as the sole narcotic, a 25- 100~pg epidural bolus is
Table I Characteristics of Postoperative Analgesia Achieved with Spinal Opioids Drug
Dose* (mg)
Onset (min)
Duration** (hr)
Epidural Morphine Meperidine Methadone H ydromorphone Diamorphine Fentanyl
l-10 PO- 160 l-16 l-2 4-6 0,025-O. 15
30 5 10 15 5 5
6-24 6-8 6-10 lo-16 12 4-6
0.1-0.5 IO-30 l-2
5 ? ?
8-24 10-30 20
Subatachnoid Morphine Meperidine Diimorphine
*Low doses may be effective when administered to the elderly or when injected in the thoracic region. **Duration of analgesia varies widely; higher doses produce longer duration.
Vol. 5 No. 3 June 1990
Management of Acute and Postoperative Pain
Table 2 Starting Dose (mg) of Epidural Morphine for Incisional Pain*
Patieni
AiF (yr) 15-44 45-65 66-75 76+
Thoracic Surgery Nonthoracic Surrrerv (Lumbar or Thoracic Lumbar Caudal Catheter) Catheter Catheter ”
5 4 3 2
,
4 3 2 1
6 5 4 2
These doses should only be considexd as guidelines. Safe and effective doses for individual patients may vary considerably. *These doses are based on the USC’ of undiluted 0.1% preservative-free morphine.
fol.lowed by a continuous infusion of 25-150 pglhr with an accurately calibrated pump.
Until it is possible to identify and eliminate the factors that occasionally lead to severe respiratory depression in patients receiving spinal opioids, it must be assumed that all patients offered these techniques are at risk. The subarachnoid route may carry higher risk than the epidural route, although the relative risk of the two approaches has not been systematically addressed. However,, because a catheter in tht epidural space can migrate through the dura at any time, equal vigilance must be exercised with both techniques. Patiems at greatest risk a1.e those in the immediate postoperative period (< i 2 hr, see later). Tti prevent serious injury or death, there is no substitute for a high level of vigilance. This may be provided by a nurse trained to check rate and depth of respiration, as well as generai status and level of consciousness, at frequent intervals. Respiratory monitors that sound an alarm if ventilation is not detected may augment this process, but should not be viewed as substitutes for alert, well-trained human observers. Intensive care faci!tties are well suited to t%; level of monitoring and should be used for patients at special risk (advanced age, serious underlying conditions, extensive surgery). However, the expense and limited availability of the?.e facilities render them impractical for routine use. A “step-down unit,” intermediate between intensive care and a regular ward with
I41
regard to the level of monlitoring and nursing care available, is an appealing alternative. \EJe have demonstrated that with extensive nursing education, careful patient selection, frequent monitoring of ventilation, protocols for immediate treatment of complications, and immediate availability of medical personnel, spinai opioids can be offered safely on cozlventionai hospital wards. Delegation of all responsibility for pain control to one group of physicians within an institution can minimize errors of conflicting or duplicate orders, or inadvertent administration
of parenteral
opioids to patients
receiving intraspinal opioids. This is particularly impo.:Lant given that such concurrent dosing represents a frequently cited correlate of lifethreatening levels of respiratory depression (see later).
Under some circumstances, spinal opioids are best avoided. These include (a) inexperience in
performing lumbar puncture or epidural block-particularly in the cervical or thoracic regions, (b) inadequate nursing education ar monitoring capabilities, (c) infection at the site of needle insertion, and (d) known opioid allergies. It remains controversial whether these techniques should be used in patients with coagulopathies, including these receiving anticoagula:it therapy. Decisions should be based on the relative risks and benefits for ind.ividual patients. Ct.~~.lications
and
Their
Treabnmd
Depression. Early respiratory depression, occurring in the first 2 hours follow-
h!es@m
ing injection, is a feature only of epidural opioid administration and is a result of vascular up+dke and redistribution (ie, the same mechanism that follows intramuscular injection). Qelayed respiratory depression occurring 6- 12 hr after subarachnoid or epidural injection is likely the consequence of rostra1 spacad of opioid in cerebrospinal fluid. The target site is thought to he the respiratory center located superficially in the floor of the fourth ventricle. The actual incidence of this event is ncmtknown and depends on a number of factors, including the
population studied, how they are monitored, and the definition of respiratory depression. In a large, multiinstitutional Swedish question-
l?mfy
142
naire survey, the incidence of “depression reIn a quiring naloxone” was 0.25%-0.40%.11 questionnaire survey of 74 U.S. institutions, the incidence of “respiratory insufficiency” was 1.9%2.3%.‘* In a prospective study of 1,085 patients in a single institution, the incidence of “respiratory depression” was 0.9%.4 It is not actually known wheLher the risk of severe respiratory depression is greater after the spinal administration of analgesic concentrations of opioids or more conventional systemic routes. It has, for example, been reported that 860 hospitalized patients receiving morphine orally or parenterally (IV, IM, subcutaneously [SC]) demonstrated a 0.9% incidence of “life-threatening ,respiratory depression.“*3 The risk of delayed respiratory depression after spinal opioids appears to bc greatest early in the course of therapy. There ase no reported cases of this complication occurring later than 24 hr after administration of the initial dose of drug. Consistently impressive among predisposing risk factors are advanced age, concomitant use of systemic opioids or other central nervous system (CNS) depressants, and extensive surgery. Therefore, large doses of perioperative opioids, long-acting sedatives, and postoperative parenteral opioids should be avoided or used with caution in patients receiving spinal opioids. Respiratory rate alone is not an adequate indicator of ventilatory status in volunteers” or in postoperative patients’” receiving spinal opioids. A more global assessment is necessary, partkulariyduring the first 24 hr of treatment. This should include assessment of level of consciousness, since increasing sedation (presumably due to central drug effect and CO, narcosis) has been noted with advanced respiratory depressionP Healthy volunteers breathing CO,
T&ble3 Bxarnple of Bedside Sedation Scale Sedation 0 (None) 1 (Mild)
Description
2 (Moderate)
Patient alert Occasionally drowsy; easily aroused Frequently drowsy; easily
3 (Severe) S (None)
aroused Somnolent; diicult to arouse Normal skep; easily aroused
Jmnul of Pa& ad Sympnn Management
mixtures have h~en observed to lose consciousness at pCOp levels of -80 mm Hg.rb Every patient receiving spinal opioids whose level of consciousness deteriorates unexpectedly should be assumed to have respiratory depression until disproved by arterial blood gas analysis. A simple bedside sedation scale (Table 3) has proved to be a useful clinical tool in detecting respiratory depression in our practice. The immediate treatment of severe respiratory depression is support of ventilation. Equipment to deliver oxygen with positive pressure must be readily available, and personnel in the area must be familiar with its use. Naloxone 0.4 mg intrarenously will usually restore adequate spontaneaus ventilation, but, given the short half-life of the drugs relative to the spinal narcotic, repeated doses are sometimes necessary. This drug should be immediately available. Pru&us. This symptom is common but seldom bothersome. The incidence is particularly high in obstetric patients. Itching may be generalized or localized, with the face beir:g Lhc: most common site. Pruritus is seen both with opioids containing preservatives and preservative-free preparations. Although probably not caused by histamine release, antihistamines will often provide symptomatic relief. Naloxone is consistently effective but may have to be administered frequently or infused. Urinary Retentimt. The incidence of this prob. lem has been higher in volunteers than in patients, and higher in males. Naloxone may help prevent or reverse urinary retention, but doses approaching those that antagonize analgesia may be needed. Some patients will require bladder catheterization. Nausea and Vomiting. These distressing symptoms are believed to be the result of rostra1 spread of the opioid in the cerebrospinal fluid to the vomiting center and the chemoreceptor trigger zone located superficially in the floor of the fourtih ventricle. Relief is frequently possible with antiemetics, but these may also produce unwanted sedation or even contribute to the risk of respiratory depression.” Transdermal scopolamine patches applied to the mastoid area have beeu effective in many of our patients. A continuous naloxone infusion is usually effective and should be considered
Vol. 5 No. 3 June 1990
Management of Acute and Postoperative Pain
when nausea and vomiting do not resolve with other measures. Se&&m. When any patient receiving spinal opioids appears excessively sedated, hypercarbia should be suspected and, if present, treated. The possible contributing role of other drugs, such as antiemetics, should also be considered. Sedation produced by spinal opioids, rarely a significant problem with moderate drug doses, may be the result of rostra1 spread of the drug in cerebrospinal fluid. Pharmacologic treatment is seldom indicated, but physostigmine 1 mg intravenously may be effective.18
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whose pain was not adequately co;ltrolled with epidural opioids alone. In addition to the monitoring used for patieuts receiving only epidural opioids, frequent measurement of blood pressure and sensory and motor examinaG.,n is recommended. A sample of Standard Orders for epidural local anestheticiopioid mixtures is provided in Appendix B.
l. Wang JK, Nauss LA, ThomasJE.
Pain r&ef by
intrathecally applied morphine in man. Anesthesiology 1979;50:149-151.
Efkkd Awsthti
Local id iWktures
Although continuous infusion of local anesthetics in usual clinical concentrations produces effective analgesia, it may also produce undtsirable effects, including hypotension, sensory and motor block, nausea, and urinary retention. In an attempt to achieve postoperative analgesia free of side effects, combinations of very dilute local anesthetics and opioids infused continuously through an epidural catheter have been advocated. Nociceptive pathways may be in..c’rrupted at different sites with the two drbldsnamely., the nerve axon with the local anesthetic and the spinal opioid receptor with the opioid. Bupi.vacaine appears to be well suited to ;his application because dilute solutions product minimal motor block. Cullen and colleagues’g used a mixture OFbupivacaine 0.1% plus morphine 0.0 1% infused at a rate of 3-4 mL/hr and compared it to the same concentrations of bupivacaine or morphine infused alone. Pain scores in the morphine and combination group were superior to the bupivacaine group. The only significant difference in side effects was a higher incidence of pruritus in both morphine groups. Hypotension or difficulty witla ambulation were not apparent in the groups receiving bupivacaine. It remains unclear whether the combination of epidural opioids and local anesthetics are superior for certain patients. The author has used a combination of fentanyl 0.0002% (2 pg/mL) plus 0.0625% bupivacainc infused at a rate of 8-20 mL/hr with good effect in patients with known tolerance to opioids and in patients
2. Behar M, Olshwang D, Magora F, Davison JT. Epidural morphine in the treatment of pain. Lancet 1979;1:527-529. 3. Boskovaki N, Lei,inski A, Xuered J, Mercieca V.
Gaudal epidural morphine for post-operative pain relief. A Plaesthesia 1980;35:67-68. 4. Stenseti, R. Sellevoiid 0, Breivik H. Epidural morphine for ijostoperative pain: experience with 1085 patients. Acta Anaesthesiol Stand 1985;29:148- 156. 5. RawaI N, et al. Comparison of intramusculat and epidural morphine for postoperative analgesia in the grossly obese: influence on postoperative ambulation and pulmonary function. Anesth Analg 1984;63: 583-592. 6. Yeager MP, Glass DC, Neff RK, Brinck-Johnsen T. EpiduraI anesthesia and analgesia in high-risk surgical patients. Anesthesiology 1987;66:729-736. 7. Chadwick HS, Ready LB. Intrathecal and epidural morphine sulfate for postcesarean analgesia: a clinical comparison. Anesthesio!ogy 1988;68:925-929. 8. Lin D, Becker K, Shapiro HM. Neurologic changes foiIowing epidural injection of potassium chloride and diazepam: a case report witt laboratory correlations. Anesthesiology 1986;65:210-212. 9. Chambers WA, Sinclair CJ, Scott DB. Extradural morphine for pain after surgery. Br J Anaesth 1981;53:921-925. 10. Ready LB, Chadwick HS, Ross B. Age predicts effective epidural morphine dose after abdominal hysterectomy. Anesth Analg 1987;66:1215- 1218. 11. Custafsson LL, Schildt B, Jacobsen KJ. Adverse effects of extradural and intrathecal opiates: repart of a nationwide survey in Sweden. Br J Aalaesth 1982;54:479-486. 12. Mott JM, Eisele JH. A survey of monitoring practices foIlowing spinal opiate administration. Anesth Analg 1986;65:Sl-S170. 13. Miller RR, Greenblatt DJ, eds. Drug effects in hospitalized patients. New York: John Wiley and Sons, 1976:151-152.
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Journal of Pain and Symptom Management
14. Camporesi EM, et al. Ventilatory COs sensitivity after intravenous and epidural morphine in volunteem Anesth Analg 1983;62:633-640.
17. Cohen SE, Rothblatt AJ, Albright GA. Early respiratory depression with epidural opioid and intravenous droperidol. Anesthesiology 1983;59:559560.
15. Rawal N, Wattwil M. Respiratory depression after epidural morphine: an experimental and clinical study. Anesth Analg 1984;63:8-14.
18. Shulman MS, Sandler A, Brebner J. The reversal of epidural morphine induced somnolence with physostigmine. Can Anaesth Sot J 1984;31:678-680.
1E Sechzer PH, et al. Effects of CO2 inhalation on ‘al pressure, ECG and plasma catecholamines 17-OH corticosteroids in normal man. J Appl Phyciol 1960;15:454-458.
19. Cullen ML, et al. Continuous epidural infusion for analgesia after major abdominal operations: a randomized, prospective, doable-blind study. Surgery 1985;98:718-728.
Sample Epidural Opioid Standard Orders MgTime 1. Operating room dose: Drug Drug for continuing epidural analgesia: 2. mg every 6-12 hr A. PF morphine (1 mg/mL) B. Fentanyl(l0 pg/mL normal saline) Infuse -ClgrmL) per hr concentration _ C. Other: Druginterval DoSeFor inadequate analgesia with prescribed dose above, give fentanyl50 Fg (1 .O mL) into epidural catheter every 3. Shrprn 4. Maintain IV access (drip, heparin lock) for 24 hr after last dose of epidural opioid 5. Naloxone 0.4 mg at bedside 6. No opioids or other CNS depressants to be given except as ordered by the Acute Pain Service 7. Monitoring: Resp!.ratory rate and sedation scale every 1 hr for first 24 hr 8. Treatment of side effects: A. Call Acute Pain Service for sedation scale = 3 B. Call Acute Pain Service for RR C 8 per min C. Naloxone 0.4 mg IV stat for sedation scale = 3 plus RR C 8 per min; call Acute Pain Service D. Metoclopramide 10 mg IV q6h prn for nausea/vomiting. In aa’ditiun,ifage <6Oyears, transdermal scopolamine patch to either mastoid area for nausea/vomiting; change every 72 hr prn E. Naloxone 0.1 mg IV for severe itching; MR every 10 min x 5 F. For urinary retention, “in and out” bladder catheter For inadequate analgesia or other problems related to epidural, call Acute Pain Service
Vol. 5 No. 3 June 1990
Management of Acute and Postoperative Pain
Sample Orders for Epidural Local AnestheWOpioid
Infusions
hr 1. Infusion begun at: 2. Drug for continuing epidural analgesia: Bupivacaine l/16% (0.625 mg/mL normal saline) plus Fentanyl-2 pg/mL normal saline or PF morphine-O. 1 mg/mL normal saline or concentration Other: Local anesthetic _ Opioid _ concentration mUhr Infuse at 3. Fentanyl50 pg (1 .O mL) into epidural catheter every 3 hr prn for inadequate analgesia with prescribed dose above 4. Place at bedside: A. Ephedrine 25 mg/5 mL (ie 5 mg/mL) B. Naloxoxte 0.4 mgll mL 5. Maintain IV access (drip or heparin lock with flushes) 6. No opioids or other CNS depressants to be given except as ordered by the Acute Pain Service 7. Monitoring: A. BP/pulse (via automatic BP monitor) from start of infusion every 30 min x 3 hr; then every 1 hr B. Resp rate & sedation scale every 1 hr for first 24 hr; then every 2 hr C. Sensory level and motor function every 2 hr while awake D. Postural BP/P prior to first ambulation 8. PRN treatments: A. Nalox~e ri.4 mg IV stat for sedation scale = 3 plus RR C 8 per min; call Acute Pain Service B. Metoclopramide 10 mg IV every 6 hr pm for nausea/vomidng; in addition, if age <60 yr, Transdermal !$opolamine patch to either mastoid area; change every 72 hr pm C. Diphenhydramine 25 mg IV every 6 hr pm for severe itching D. For urinary :~ention, “ia and out” Madder c, theter prn E. Triazolam 0.125 mg every hr prc; MR X 1 9. Notify Acute Pain Service for the following: lmin A. BP< _mmHgand/orP<_ B. RR < 8lmin C. Sedation scale = 3 D. Numbness above nipples and/or inability to bend knees E. Posture BP drop > 15 mm Hg and/or HR increase >20/min F. Inadequate analgesia or other problems related to epidural