Venipuncture is a mandatory requirement for the administration of safe general anesthesia. Insertion of an IV cannula is very distressing for many patients. A clinical study revealed that discomfort from IV catheter insertion ranked fifth among the 33 low morbidity clinical outcomes by expert anesthesiologists when both clinical importance and frequency were considered (1).
The pain experienced during venous cannulation has both somatic and psychological components. Pharmacological measures, such as the application of local anesthetics, treat only the somatic component of pain, whereas attention-diverting measures(e.g., “cough trick”) address only the psychological component of pain (2,3).
A literature search revealed laboratory studies showing that baroreceptor activation induces nociception but there was no clinical study exploring the effect of the Valsalva maneuver on pain (4,5). We therefore planned this study to evaluate the efficacy of the Valsalva maneuver on pain associated with venous cannulation and compare it with that of attention-diverting.
After approval from the institute’s ethical committee and written informed consent from the patients, this prospective, randomized study was conducted. The present study consisted of 75 consecutive adult patients, ASA physical status I and II patients of either sex, undergoing elective surgery. Patients having problems in communication, and those with an abnormal skin condition, such as infection at the site of proposed venous cannulation, scars, and eczema, were excluded from the study. Patients who could not hold the mercury column up to 30 mm Hg for a period of at least 20 s and whose vein could not be cannulated in the first attempt were also excluded from the study.
Initially, we conducted a pilot study on 25 surgical patients and observed that during venous cannulation patients had a median visual analog score (VAS) of 3 (2). VAS was assessed on a continuous scale of 0–10 where 0 stands for “no pain” and 10 stands for “worst imaginable pain.” Assuming that after therapy the median VAS would reduce by 50%, one would need to enroll 23 patients in each group for the results to be statistically significant at a power of 80% with a level of confidence of 5%. In considering any dropouts, we included 25 patients in each group.
Patients were randomized with the help of a computer-generated table of random numbers into 3 groups of 25 each. Group I (C) acted as control and did not perform the Valsalva maneuver and were not asked to press a rubber ball; Group II (V) patients were asked to blow into a rubber tubing connected to a sphygmomanometer and raise the mercury column up to 30 mm Hg for a period of at least 20 s; whereas group III (B) patients were given a rubber ball in the palm of the hand, which was not to be cannulated and were asked to press it as hard as they could. All patients were premedicated with tablet lorazepam 2 mg the night before surgery and repeated at 6 am with sips of water.
In the operating room, patients were placed in the supine position. A vein on the dorsum of the nondominant hand was identified and patients were asked to turn their head to the opposite direction. Then, depending on the group allocation, patients were asked to perform Valsalva or press the ball or were advised nothing. Twenty seconds later, a venous tourniquet was applied and peripheral venous cannulation was attempted. If the proposed vein was still not prominent enough to be cannulated, it was gently tapped upon and the time taken was recorded. Peripheral venous cannulation was performed by the same senior registrar in all the patients by an 18-gauge cannula (Angiocath SP™, Becton Dickinson India, Ltd.). During the process of venous cannulation, patients were observed and questioned by an independent anesthesiologist. Pain was graded using a 4-point scale: 0 = no pain, 1 = mild pain (pain reported only in response to questioning without any behavioral signs such as facial grimacing, arm withdrawal, or tears), 2 = moderate pain (pain reported in response to questioning and accompanied by a behavioral sign or pain reported spontaneously without questioning), and 3 = severe pain, i.e., strong vocal response or response accompanied with behavioral signs (6).
After peripheral venous cannulation, pain during the process of cannulation was also assessed on a VAS of 0–10 where 0 stands for “no pain” and 10 stands for “worst imaginable pain” by the same anesthesiologist. The number of patients in whom one needed to make the vein prominent before venous cannulation and the time taken were also recorded.
Results were analyzed by comparing two proportions by normal approximation (“Z” test). When the distribution of data was not normal, i.e., the data regarding grading of pain, Fisher’s exact test was applied. For comparison of VAS score, Kruskal-Wallis and Mann-Whitney test were used. The package SPSS 9.0 (SPSS Inc., Chicago, IL) was used for statistical analysis. P < 0.05 was considered as significant.
There was no difference in the demographic profile among groups (P > 0.05) (Table 1).
A significant reduction in the incidence of pain was observed in the Valsalva group: 72% as compared with the other 2 groups at 100% (P < 0.001) (Table 2). Regarding severity of pain during venipuncture, all the patients in the Valsalva group had mild pain (P < 0.001), whereas none of the patients experienced moderate pain (P < 0.001) when compared with the other 2 groups (Table 2). The median VAS was reduced in the Valsalva group when compared with control and ball groups (P < 0.001) (Fig. 1). The number of patients in whom it was required to make the vein prominent before venous cannulation was less in the Valsalva group (15 of 25) as compared with 25 of 25 both in the control and the ball groups (P < 0.001) (Table 3). The time taken for making the vein prominent was also less in the Valsalva group (7.0 ± 3.8 s) when compared with control (13.8 ± 5.2 s) and ball (13.5 ± 4.8 s) groups (P < 0.001) (Table 3).
The incidence of pain during venipuncture in the Valsalva group was 72% as compared with 100% in the other 2 groups (P < 0.001). All of the patients in the Valsalva group had mild pain, whereas none of the patients experienced moderate or severe pain when compared with the other two groups. There was also a reduction in the number of patients in whom it was necessary to make their veins prominent and also the time taken was reduced in the Valsalva group when compared with the other 2 groups (P < 0.001).
The Valsalva maneuver is performed by having the subject conduct a maximal, forced expiration against a closed glottis and holding this for at least 16 seconds (7). Similar changes occur whenever a person conducts forced expiration against either a closed glottis or high pulmonary outflow resistance, or when the thoracic and abdominal muscles are strongly contracted. Whenever Valsalva is applied, contraction of the thoracic cage compresses the lungs and causes a large increase in intrathoracic pressure. This increase in the intrathoracic pressure results in compression of the vessels within the chest and in turn results in baroreceptor activation (7).
The reduction in pain observed during venous cannulation in the Valsalva group could have been multifactorial. Pharmacological, neuro-anatomical, electrophysiological, and behavioral data indicate that systems controlling cardiovascular function are closely coupled to those modulating the perception of pain. This view is directly supported by experiments from a laboratory showing that activation of either the cardiopulmonary baroreceptor reflex arc or the sinoaortic baroreceptor reflex arc induces antinociception (4,5). Distraction, by directing attention to a non-noxious stimulus in the immediate environment, is also a way to reduce pain, although the results of distraction on prevention of venous cannulation pain are controversial (8,9). Activation of the segmental pain inhibitory pathways could be the other potential mechanism (10).
The increase in intrathoracic pressure results in a decrease in venous return (5), and thus might make the veins prominent. This may explain the significant reduction observed in the number of patients in whom it was necessary to make the vein prominent before venous cannulation in the Valsalva group when compared with the other groups. However, we did not find any effect of distraction in the form of pressing the rubber ball on the pain associated with venous cannulation.
In conclusion, we observed that the Valsalva maneuver performed before venous cannulation decreased the incidence and severity of pain associated with venipuncture. Valsalva is easy to perform and an inexpensive method of reduction of pain during venous cannulation.
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