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From the Departments of *Anaesthesiology and Biostatics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India.
Address correspondence and reprint requests to Dr. Anil Agarwal, Department of Anaesthesiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow 226014, India. Address e-mail to aagarwal{at}sgpgi.ac.in.
Abstract
BACKGROUND: Venous cannulation is often performed without any analgesia, even though pain experienced during this procedure is at times very distressing. Various pharmacological and nonpharmacological measures have been tried with variable results to minimize venous cannulation pain. We designed the present study to evaluate the efficacy of a flash of light on attenuating venous cannulation pain.
METHODS: Ninety adults (15–60 yr), ASA physical status I and II, of either sex, undergoing elective laparoscopic cholecystectomy, were included in this prospective and randomized study. Patients were divided into three groups of 30 each. Group I (control); Group II (distraction): photographed without a flash of light; and Group III (flash): photographed with a flash of light just before venous cannulation of a vein on the dorsum of the nondominant hand. Immediately after the photograph, venous cannulation was performed using an 18-gauge cannula.
RESULTS: Two patients from each group could not be cannulated on their first attempt and were therefore dropped from subsequent analysis. The incidence of venous cannulation pain in the flash group was lower, i.e., 50% (14 of 28) when compared to 100% (28 of 28) observed in the other two study groups (P < 0.01). Severity of venous cannulation pain as assessed by the Visual Analog Scale scores (between 0 and 100; where 0 = no pain and 100 = worst imaginable pain) presented as median (interquartile range) were reduced in the flash [10(20)] and distraction [20(10)] groups compared with the control group [40(20)] (P < 0.01). The severity of venous cannulation pain was also reduced in the flash group compared with the distraction group (P < 0.01).
CONCLUSION: We conclude that a flash of light before venous cannulation is a safe, effective, and easy-to-use method for minimizing venous cannulation pain.
Venous cannulation often is performed without any analgesia, even though the pain associated with this procedure is at times very distressing. Various pharmacological and nonpharmacological measures have been tried, with variable results, to minimize venous cannulation pain.1,2 Virtual reality and audiovisual distraction are promising analgesic techniques for reduction of pain and discomfort during medical procedures.3 There are, however, few inexpensive, simple, effective methods, which are devoid of any associated pain and side effects. The present study was designed to evaluate the efficacy of a flash of light on the incidence and severity of venous cannulation pain.
METHODS
This prospective, randomized, and placebo-controlled study included 90 adult patients (15–60 yr), ASA physical status I and II, of either sex, undergoing elective laparoscopic cholecystectomy. Approval from our institute's ethical committee and written informed patient consent were obtained. Patients with peripheral neuropathy, long-term consumption of analgesics, blindness, seizures, and those having difficulty in communication were excluded from the study.
Calculation of sample size was done before commencement of this study with the presumption that therapy would reduce venous cannulation pain by 30%; power analysis, with 
= 0.05 and β = 0.80 revealed that we would need to enroll 24 patients in each group. We enrolled 30 patients in each group to compensate for dropouts.
After randomization, venous cannulation was performed and patients who could not be cannulated in the first attempt were excluded from further analysis, considering that the incidence and severity of venous cannulation pain associated with repeated attempts would differ from that of a single attempt and maintaining the same level of distraction for subsequent venous cannulation would be difficult.
Eligible patients were identified during the preanesthetic check-up, and after the initial workup, all patients were premedicated with oral lorazepam 2 mg the night before surgery and again at 6 am with sips of water. The participants were posted as first case in the operation room and the study was conducted between 9 and 11 am so as to minimize the influence of circadian difference on pain sensitivity.4 Patients were randomized into three equal groups of 30 each with the help of a computer-generated table of random numbers. Group I (control): served as control; Group II (distraction): patients were photographed without a flash of light from a distance of 2 m just before venous cannulation; and Group III (flash): patients were photographed with a flash of light from a distance of 2 m just before venous cannulation. Patients belonging to Groups II and III were informed that they would be photographed before venous cannulation. Patients were asked to turn their head away from the side of venous cannulation and to turn their attention to the camera. A venous tourniquet was applied and a vein on the dorsum of the nondominant hand was made prominent. Depending on the results of the randomization, the patient's face was photographed. The photograph was taken with a camera [(Sony HVL-HFL1 with luminance intensity approximately 100 cd, lighting distance approximately 11 Lux, flash shooting distance (1–5 m)]. Immediately after the photograph, venous cannulation was performed by a registrar (G.S.Y.) using an 18-gauge cannula (Poly Medicure Ltd., India).
The primary outcome was defined as the incidence of venous cannulation pain, whereas the secondary outcome was defined as the severity of venous cannulation pain and was assessed using a Visual Analog Scale (between 0 and 100; where 0 = no pain and 100 = worst imaginable pain). Both these outcomes were assessed by an anesthesia registrar (M.T.) who was called into the operating room for assessment of incidence and severity of venous cannulation pain after venous cannulation, and thus was blinded to patient group allocation.
The method of analysis was decided prospectively. The incidence of venous cannulation pain was assessed by comparing two proportions by normal approximation (Z test). Data regarding severity of venous cannulation were assessed by Fisher's exact test. The package SPSS 14.0 (SPSS Inc., Chicago, IL) was used for statistical analysis. P < 0.05 was considered as significant.
RESULTS
From October 2006 to December 2006, we enrolled 90 patients in three equal groups. In six patients, venous cannulation could not be achieved on the first attempt, and therefore these patients were dropped from the study (two in each group). Thus, the number of evaluated patients for the study was 84. There were no differences in patient demographics among groups (P > 0.05) (Table 1).
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The incidence of venous cannulation pain in the flash group was lower, i.e., 50% (14 of 28) compared with 100% (28 of 28) observed in the control and distraction groups (P < 0.01). The severity of venous cannulation pain as assessed by median (interquartile range) Visual Analog Scale scores were reduced in the flash [10(20)] and distraction [20(10)] groups compared with the control group [40(20)] (P < 0.01) (Fig. 1). Further, there was a significant reduction in the severity of venous cannulation pain in the flash group when compared with distraction group (P < 0.01) (Fig. 1).
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Absolute risk reduction in the flash group was 50% and the number-needed-to-treat was 2, whereas absolute risk reduction in the distraction group was 0% and number-needed-to-treat was infinite.
DISCUSSION
We observed significant reduction in the incidence and severity of venous cannulation pain in the flash of light group compared with the control and distraction groups.
Somatosensory thalamic stimulation has been reported to activate thermal pathways leading to modulation of nociceptive information.5 The thalamus is an integral part of the light reflex. We therefore presumed that a flash of light, by initiating a light reflex, might cause thalamic stimulation and thus decrease venous cannulation pain. The present study was therefore planned to evaluate the efficacy of a flash of light to attenuate venous cannulation pain.
During chronic pain conditions, thalamic stimulation causes modulation of nociceptive information, leading to reduction in pain perception.5,6 Audiovisual entrainment (AVE) has been reported to be effective in promoting relaxation, hypnotic induction, and restoring somatic homeostasis, plus improving cognition, and for treating migraine headache, chronic pain, anxiety, depression, and hypertension.7 An increase in blood serum levels of endorphin and melatonin have also been observed after AVE with its associated antinociception.8,9 However, for entrainment to occur, constant, repetitive stimuli of sufficient strength are necessary so as to excite the thalamus. Distraction is another very important component of AVE, which, in itself, is a promising analgesic technique that may be used safely and effectively for reduction of pain and discomfort during medical procedures.7
A literature search did not reveal any studies on the effect of thalamic stimulation or AVE on acute pain. The observed reduction in the incidence and severity of venous cannulation pain after a flash of light in the present study could have been because of any or all of the above-mentioned mechanisms, even though the stimulus was given only once and thus was not repeated. Further, a flash of light may have a component of distraction, which appears to involve competition for attention between highly salient pain sensations and directs focus on some other information processing activity. Further research is suggested in this area.
Various pharmacological and nonpharmacological methods such as application of eutectic mixture of local anesthetic cream, ethyl chloride spray, distraction tactics, valsalva, and inflation of a balloon have been tried to minimize venous cannulation pain with variable success.1,2,10–14 AVE is a promising analgesic technique for reduction of pain and discomfort during medical procedures.7 There are no inexpensive, simple, effective methods, which are devoid of any associated pain and side effects.
Some limitations of our study are that it could not be performed in a double-blind manner, and it required coordination between the person igniting the flash of light and the person performing venous cannulation. We could not measure the time lag between the ignition of the flash and venous cannulation; however, we presume it must have been >200 ms, the desired time lag for the flash to produce antinociception.15 We therefore conclude that a flash of light before venous cannulation is an effective, simple, and inexpensive method, which is devoid of any associated pain and side effects for attenuating venous cannulation pain.
Footnotes
Accepted for publication November 20, 2007.
REFERENCES
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