The emulsion formulation of propofol (Diprivan) evokes pain on i.v. injection, although its pH and osmolality are close to those of blood. The pain induced by serial dilutions of propofol in Intralipid and 5% glucose was examined in isolated vein segments and after intracutaneous injection. Propofol evoked pain in a concentration-related manner in six of eight subjects after i.v. perfusion and in all eight subjects after intracutaneous injections. Pain was maximal with propofol 56 x 10(-3) mol litre-1 when visual analogue pain scale was 60% of maximum (range 20-92%) for venous perfusion and 89% (range 66-100%) for intracutaneous injection. Dilution with 10% Intralipid reduced pain more than that with 5% glucose. We conclude that the intensity of pain after i.v. injection of propofol was related to its free aqueous concentration.
We have studied the intensity and time-course of pain during and after injection into an isolated vein segment in seven normal subjects of saline or glucose of different osmolalities (0-6 osmol kg-1) or pH (2-13). Pain scores were recorded continuously by a modified visual analogue scale apparatus. With osmolar stimulation, pain occurred at 1.0 osmol kg-1 during perfusion and 3.0 osmol kg-1 with rapid injection and increased with osmolar concentration of both saline and glucose solutions. Acidic and alkaline solutions evoked pain at a pH value less than 4 or greater than 11. We conclude that pain on i.v. injection of some sedative and hypnotic drugs is likely to be caused by formulations of extremely unphysiological osmolalities or pH values.
SUMMARY1. To explore the function of the sensory innervation of veins in humans we used a psychophysical approach to study painful and non-painful sensations by applying polymodal stimuli (electrical, stretch, cold/heat and osmotic) inside vascularly isolated hand vein segments before and after blockade of either venous or cutaneous afferents.2. All modes of stimulation elicited pain, which showed only slight adaptation during 10 min of maintained stimulation. Pain increased monotonically with stimulus intensity between threshold and the maximally tolerable pain.3. The exponents of the power functions of the pain magnitude-stimulus strength relations for five stimulus modes ranged between 2 5 and 3 3 but did not significantly differ from one another (P = 0-3).4. Pain evoked by all stimuli was reported to be of similar quality, i.e. sharp, aching and unpleasant; it was accompanied by non-painful sensations (skin movements on stretching, warm and cold sensation with intravenous thermal stimulation) unless the skin above the stimulated vein segment was numbed with benzocaine ointment.5. Pain could no longer be evoked in the presence of 0 4-0{8 % procaine within the stimulated vein segment.6. These observations are consistent with the view that veins are invested with polymodal nociceptors only, which in all likelihood are connected with thinly myelinated afferents of the Ad group.7. The vascularly isolated vein segment may open a new avenue for pain research in humans.
SUMMARY1. To test the hypothesis that nociceptors of cutaneous veins mediate cold pain, we studied in man the time course of pain intensity and skin sensibility in relation to both intracutaneous and vein wall temperature during cooling of the dorsum of the hand by ice water before and after perivenous and intravenous nerve block.2. Upon exposure to cold, intracutaneous temperatures fell exponentially (halflife/45-75 s) within 10 min to a median of 4°C (range 2-9°C) and returned to baseline with a similar time course during rewarming (half-life/40-85 s).3. Skin sensitivity to pin prick disappeared and returned at almost the same intracutaneous temperatures (16-26 9QC). Pain, however, occurred and even increased when the skin was already numb. 4. Pain occurred during cooling and disappeared during rewarming at vein wall temperatures between 23 and 28°C, and its intensity increased to a maximum of 72-100 % of visual analogue scale as vein wall temperature decreased to a minimum of 9°C (range 7-10-5°C).5. The pain intensity-vein wall temperature relations derived from skin cooling with threshold temperature changes between -5-5 and -9°C and slopes between 2-2 and 3-3 were congruent to those derived from intravenous cooling in a previous study to ours.6. Perivenous and intravenous nerve block, which did not alter the sensitivity of skin and periosteum, relieved cold pain markedly (perivenous block) or completely (intravenous block).7. These observations are consistent with the hypothesis that nociceptors of cutaneous veins mediate cold pain in humans.
We have compared the efficacy of two non-invasive methods of transdermal anaesthesia: application of EMLA cream and iontophoresis of 5% lignocaine with adrenaline 1:50,000 in six healthy subjects. We tested depth of tissue penetration (pinprick) and effect on pain evoked by i.v. injection. After iontophoresis, pain on i.v. injection was abolished in five of six volunteers, whereas EMLA had no effect. We conclude that local anaesthetics penetrate deeply enough to numb both veins and skin with iontophoresis only.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.