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Factors that influence pain intensity and fentanyl requirements after a gynecologic laparotomy

Seong Tan PC, Nik Mohamad NA, Gan SH

Pain Manag Nurs, 2013 Jun;14(2):102-9.
PMID: 23688364 DOI: 10.1016/j.pmn.2010.12.004

The association between pain intensity and its control by intravenous patient-controlled analgesia (IV-PCA) with fentanyl after a laparotomy for cystectomy/salphingoophorectomy, myomectomy, or hysterectomy was investigated. IV fentanyl infusion was administered to patients (n = 94) at 3 μg/kg/h to provide intraoperative analgesia after induction of general anesthesia. Postoperative fentanyl requirements were quantified via IV-PCA, and the amounts of rescue fentanyl required both during and after surgery were recorded. Mean values for PCA use as well as the visual analog scores (VAS) for pain were documented for up to 24 hours. The association between postoperative fentanyl requirements and VAS were then analyzed by using Mann-Whitney or Kruskal-Wallis tests. Patients with lower midline incisions had greater degrees of pain (p < .05) during the first 16 hours after surgery but did not consume more fentanyl compared with patients with Pfannenstiel incisions. Subjects who underwent operations lasting >4 hours required more rescue fentanyl during surgery (p < .05). However, this group consumed less fentanyl during the first 4 hours after surgery (p < .05). The demand at the fourth 4-hour period was lower among subjects undergoing myomectomy compared with cystectomy/salphingoophorectomy or hysterectomy (p = .045). Only a poor correlation was observed between pain intensity and analgesic usage. Postoperative pain intensity is influenced by the type of surgical incision but not the type of gynecologic surgery nor the duration of surgery. The relationship between subjective pain ratings with analgesic consumption is weak. Prolonged intraoperative administration of continuous IV fentanyl infusion may reduce fentanyl requirements in the immediate postoperative period.

Matched MeSH terms: Analgesia, Patient-Controlled/methods
Cytochrome P450 3A4 genetic polymorphisms and post-operative fentanyl requirements

Tan PC, Hassan SK, Mohamad NA, Gan SH

J Clin Pharm Ther, 2012 Feb;37(1):100-4.
PMID: 21128989 DOI: 10.1111/j.1365-2710.2010.01232.x

WHAT IS KNOWN AND OBJECTIVE: Interindividual variability in drug responses may be attributable to genetically determined alteration in enzyme activity. In this study, we investigated the association between cytochrome P450 3A4 (CYP3A4) genetic polymorphisms and post-operative fentanyl requirements.
METHODS: Patients (n = 94) scheduled for gynaecological laparotomy received i.v. fentanyl infusion (3 μg/kg/h) after induction of general anaesthesia. Post-operative fentanyl requirements were quantified by using a patient-controlled analgesia and the number of i.v. fentanyl rescue analgesia required were recorded. Pain control was assessed using visual analogue scores (VAS) and fentanyl's adverse effects were documented. CYP3A4*4, CYP3A4*5 and CYP3A4*18 alleles of cytochrome P450 3A4 were identified by polymerase chain reaction-restriction fragment length polymorphism. Differences in fentanyl requirements, VAS scores and adverse effects among the various genotypes were compared.
RESULTS AND DISCUSSION: No CYP3A4*4 and CYP3A4*5 alleles were detected. Eighty-nine patients (94·7%) were wild-type, five (5·3%) were heterozygous and none was homozygous. No significant difference was demonstrated between the genotype groups in terms of fentanyl consumption, pain control and adverse effects.
WHAT IS NEW AND CONCLUSION: CYP3A4*4 and CYP3A4*5 are rare in the Malaysian Malay population. Genetic polymorphism of CYP3A4*18 may not play an important role in influencing postoperative fentanyl requirements.

Matched MeSH terms: Analgesia, Patient-Controlled/methods
Ethnic differences in pain perception and patient-controlled analgesia usage for postoperative pain

Tan EC, Lim Y, Teo YY, Goh R, Law HY, Sia AT

J Pain, 2008 Sep;9(9):849-55.
PMID: 18550441 DOI: 10.1016/j.jpain.2008.04.004

There are reports suggesting that sensitivity to and tolerance of both clinical and experimental pain differ among ethnic groups. We examined self-rated pain score and morphine usage in 1034 women who underwent elective lower cesarian section (LSCS) for their deliveries. Data on pain scores and amount of total morphine use according to patient-controlled analgesia were collected every 4 hours. Overall, lowest pain scores were recorded 12 hours after surgery and highest at 24 hours. Morphine consumption was highest within the first 4 hours and lowest between 12 and 16 hours. There were statistically significant ethnic group differences in pain scores (P = 1.7 x 10(-7)) and morphine usage (P = 2.8 x 10(-15)) between ethnic groups, with Indians having the highest mean pain score and using the highest amount of morphine. The ethnic differences in pain score and morphine self-administration persisted after controlling for age, body mass index, and duration of operation.

Matched MeSH terms: Analgesia, Patient-Controlled/methods*
Pre-Emptive Topical Ketorolac Tromethamine 0.5% for Panretinal Photocoagulation

Chewa Raja JS, Singh S, Ismail F

J Ocul Pharmacol Ther, 2021 Jun;37(5):313-317.
PMID: 33794664 DOI: 10.1089/jop.2020.0089

Purpose: To evaluate the efficacy of topical ketorolac tromethamine 0.5% given pre-emptively a day before, for alleviating pain in patients undergoing panretinal photocoagulation (PRP) treatment. Methods: A controlled single-blinded study was conducted on 33 patients with diabetic retinopathy (DR; severe nonproliferative DR, proliferative DR, or advanced diabetic eye disease) who required PRP treatment in both eyes simultaneously. Each eye of the patients was randomly assigned for ketorolac tromethamine 0.5% eyedrop or placebo. Both eyedrop bottles were randomly labeled. Eyedrops were self-administered by the patients, 4 times a day before the procedure (at 6 am, 12 noon, 6 pm, and 12 midnight) and every 15 min for 1 h (4 times) before the laser. Each patient was subjected to PRP using a Visulas 532s Zeiss device set to spot size 200 μm, time 0.10 s, and ∼600 burns in each eye. The pain score was evaluated immediately after treatment in each eye independently with Scott's visual analog scale (VAS) and the McGill Pain Questionnaire (MPQ). Results: VAS pain score in ketorolac-treated eyes (median 3.0, interquatile range [IQR] ±2.5) was lower than in placebo-treated eyes (median 5.0, IQR ±3.0). Total Pain Rate Index score from MPQ was lower in ketorolac-treated eyes (median 3.0, IQR ±3.0) than in placebo-treated eyes (median 3.0, IQR ±2.5). Both pain score differences are statistically significant with P ˂ 0.05. Conclusion: Topical ketorolac tromethamine 0.5% given pre-emptively a day before is effective in alleviating pain in patients undergoing PRP treatment.

Matched MeSH terms: Analgesia, Patient-Controlled/methods