Comparison of intrathecal and intravenous morphine for post-operative analgesia after single level spinal fusion surgery

Vlok, Adriaan Johannes (2020-12)

Thesis (PhD)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: The purpose of this study was to evaluate the efficacy, safety and cost effectiveness of a 0.005mg/kg, up to a maximum of 0.45mg, dose of intrathecal morphine in first-time single level spinal surgery. The study was conducted, and results apply, to a tertiary care public service hospital in South Africa. This experimental intervention was compared to the institutional standard of care being the use of intravenous morphine via a patient-controlled device, administering 1mg of morphine intravenously every 7 minutes as required. Efficacy was measured with reference to validated scoring systems which included the Oswestry disability index, Roland Morris questionnaire, EQ-5 score and visual analogue scale (VAS) to assess pain, analgesia and disability in the post-operative phase and subsequent follow up. A standardised physiotherapy regime was used to mobilize patients and the patients was discharged directly to their homes, specifically skipping a step-down facility. Safety was assessed by monitoring the known side-effects of morphine (nausea, vomiting, pruritis), oxygen saturation, respiratory rate and sedation during the stay in the ICU. Inter alia, blood gases were analysed on 11 occasions within the first 24 hours. General patient follow-up occurred at 6 weeks, 3 and 6 months. The study was conducted in a prospective double-blind, randomized placebo controlled fashion. 40 patients were enrolled (20 per group). The time to discharge for the intrathecal morphine group (IT) was statistically significantly shorter (3.68 days) compared to 5.61 days for the patient-controlled analgesia (PCA) group. This translated into a 43.5% saving for general ward stay costs. VAS was assessed when lying still and moving and the difference between these values was used to quantify the intensity of pain. A significant difference was noted at 24 hours favouring the IT group. Significantly less supplemental analgesia was used in the IT group during the first 24 post-operative hours. No significant difference in side-effects were noted between the groups. The initially elevated mean PaCO2 in the IT group demonstrated a significant decrease from 4 hours up to 24 hours. An increase in mean respiratory rate was demonstrated from 10 hours onwards in both groups. Seven incidents of hypoxia (PaO2 < 8kPa) were observed (IT=4, PCA=3). The 7 incidents were explained by either a low FiO2 or a decrease in functional residual capacity (FRC) as proven by the A-a gradient. No overt sedation was clinically demonstrated at the time the PaO2 was less than 8.0 kPa. Six week, 3-month and 6-month follow-up demonstrated significant improvement in all scoring modalities in both groups. The intrathecal use of morphine had a direct effect on the μ-receptors in the spinal cord resulting in segmental analgesia allowing the patients to mobilize faster compared to the more central acting analgesic effects offered by intravenous morphine. The proposed dose proved to be safe with minimal side-effects, all of which were comparable to the PCA group. The application will be particularly useful in obese patients where the calculation of a safe intravenous dose can be challenging because of excess adipose tissue. When using IT or PCA morphine, supplemental oxygen is suggested for the first 4 hours post-operatively and continuous monitoring of respiratory rate, saturation and sedation should be done. Finally, it is recommended that it will be safer practice to reset the minimum cut-off value for saturation at a higher value than the conventional 90% level.

AFRIKAANSE OPSOMMING: Die doel van die studie was om die effektiwiteit, veiligheid en koste-effektiwiteit van ‘n 0.005mg/kg, tot ‘n maksimum van 0.45mg, dosering van intratekale morfien te evalueer in eerste operasie, enkel vlak lumbale spinale fusie chirurgie. Die studie is uitgevoer in en resultate relevant tot ‘n tersiere vlak publieke diens hospitaal in Suid Afrika. Die eksperimentele intervensie was vergelyk met standaard sorg vir hierdie tipe gevalle wat bestaan uit intraveneuse morfien toegedien deur ‘n pasient-beheerde toestel wat 1mg intravenuese morfien elke 7 minute toedien soos benodig. Effektiwiteit is gemeet deur gevalideerde evaluerings sisteme wat insluit die “Oswestry disability index”, “Roland Morris questionnaire”, “EQ-5” telling asook die “visual analogue score (VAS)” om pyn en ongeskiktheid te evalueer, beide post-operatief asook tydens opvolg besoeke. ‘n Gestandardiseerde fisioterapie regime was gebruik om die pasiënte te mobiliseer en pasiënte is direk tuis ontslaan, sonder enige rehabilitasie fasiliteit. Veiligheid is evalueer deur monitering van die bekende newe-effekte van morfien (naarheid, braking, pruritis), suurstof saturasie, asemhalingspoed en sedasie gedurende die intensiewe sorgeenheid verblyf. Bloedgas analises is gedoen op 11 geleenthede gedurende die eerste 24 post-operatiewe ure. Pasiënt opvolg het geskied op 6 weke, 3maande en 6 maande. Die studie is uitgevoer as ‘n prospektiewe, dubbel-blind, gerandomiseerde placebo beheerde studie. 40 pasiënte is ingesluit (20 per groep). Die tyd tot ontslag vir die intratekale morfien (IT) groep was statisties beduidend minder (3.68 dae) as die 5.61 dae in die pasiënt-beheerde analgesie (PCA) groep. Dit het gelei tot ‘n 43.5% kostebesparing in algemene saal verblyf. VAS was gemeet beide as die pasiënt stil lê en as hulle beweeg. Die verskil in die waardes is gebruik om intensiteit van pyn aan te dui. ‘n Statisties beduidende verskil is op 24 uur identifiseer ten gunste van die IT groep. Betekenisvol minder reddings-analgesie is gebruik in die IT groep oor die eerste 24 uur. Geen beduidende verkil in newe-effekte kon identifiseer word nie. Die aanvanklike verhoogde gemiddelde PaCO2 in die IT groep het ‘n statisties betekenisvolle uur tot uur daling getoon vanaf 4 tot 24 uur. Beide groepe het ‘n gemiddelde asemhalingspoed verbetering getoon vanaf 10 ure post-operatief aanwaards. Sewe insidente van hipoksie (PaO2 < 8kPa) is identifiseer (IT=4, PCA=3). Die 7 insidente kon verduidelik word deur of ‘n lae FiO2, of ‘n lae funksionele residuele kapasiteit aangedui deur die A-a gradient. Geen sedasie was assosieer met die insidente van PaO2 < 8kPa nie. Die 6 weke, 3 maande en 6 maande opvolge het statisties beduidende verbetering getoon in al die evaluerings sisteme. Die intratekale gebruik van morfien het ‘n direkte effek op die μ-reseptore in die spinal koord wat lei tot segmentele analgesie wat die pasiente vinniger laat mobiliseer vergeleke met intraveneuse morfien wat ‘n meer sentrale meganisme van werking het. Die voorgestelde dosis is bewys as veilig met minimale newe-effekte vergeleke met die PCA groep. Dit is veral van belang in obees pasiënte waar dosis bepaling uitdagend is met die addisionele vetweefsel wat teenwoordig is. Supplementele suurstof word aanbeveel vir die eerste 4 ure vir beide groepe, met volgehoue monitering van asemhalingspoed, saturasie en sedasie. Laastens sal dit veiliger wees om die minimum aanvaarde waarde vir saturasie op ‘n hoër vlak te stel as die konvesionele 90%.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/108978
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