Psychological heuristics of “peak-end rule” in labouring parturients: A prospective cross-sectional study

INTRODUCTION

The peak–end rule is a psychological heuristic in which people judge an experience largely based on how they felt at its peak (i.e., its most intense point) and at its end, rather than the total sum or average of every moment of the experience.[1] The principle was pioneered by the psychologist Daniel Kahneman and his colleagues in 1993 by their study titled “When More Pain Is Preferred to Less: Adding a Better End”, and it then provided a groundbreaking evidence for the peak–end rule.[2,3] In medical procedures, it suggests that a patient may have better satisfaction when peaks and ends are better managed. Thus, the satisfaction levels of a remembered procedure can drastically influence medical future.[4]

However, contrary to its envisioned and contemplated implications, especially in the branch of anaesthesiology, which is obsessed with pain relief, there is no literature till date evaluating its use in altering pain management strategies. Although we target a good pain relief during labour analgesia, significant breakthrough pain still occurs in almost 14–55% of patients.[4,5] Considering these facts, we decided to evaluate the data of parturients receiving epidural labour analgesia and hypothesised that the peak and end pain scores should have a correlation with the patient’s satisfaction rather than the average pain scores.

METHODS

The study was approved by our institutional ethics committee (vide approval number HFW (MC-II)B(12)ETHICS/2024/9321 dated 16/5/2024) and was registered with the Clinical Trials Registry-India (vide registration number CTRI/2024/09/074396). It was a prospective cross-sectional study to find the correlation between the patient’s satisfaction and the peak, mean, and end-stage pain intensity during labour. All patients were counselled for the ten-point visual analogue scale (VAS) for pain with 0 as no pain and 10 as worst unimaginable pain. The satisfaction scores were graded as 1 very satisfied and 5 very dissatisfied (Likert scale). Also, a written informed consent was taken from the participating patients. Epidural labour analgesia was administered in accordance with the departmental protocol wherein an initial bolus dose of 8 ml of 0.1% ropivacaine was given with fentanyl 2 μg/ml, followed by a patient control epidural analgesia regimen with basal infusion: 8 ml/h, a lockout interval of 10 min, and a demand bolus dose of 2 ml.

The sample size was calculated using OpenEpi software. Considering a finite population size of 6000 deliveries (normal vaginal deliveries done in a year at our institute) with a frequency of cephalic presentation around 97%, a confidence interval of 95%, and a design effect of 1, the approximate sample size came out to be 44. A total of 50 primigravidae parturients with established labour, in the age group of 18–35 years with singleton pregnancies and cephalic presentation, with a gestational age of 37 weeks or more, scheduled for normal vaginal delivery, and without having any antenatal comorbidities were finally included in the study.

Patients on entering active labour were monitored every 30 min and at the time of delivery for VAS scores. For each participant, the mean, highest, and end (of last 15 minutes before delivery) VAS scores were calculated. These values were then compared with the satisfaction scores documented 24 hours after delivery. The outcome assessor was blinded to the study hypothesis.

RESULTS

Out of a total of 50 patients, six underwent caesarean section; these were excluded, and 44 patients were finally analysed. The median pain scores at cervical dilatation <3 cm, 4–7 cm, and 8–10 cm increased with each stage and were median [interquartile range (IQR)] 2 [2], 4 [2], and 6 [2], respectively. The mean period of gestation and mean duration of labour [mean ± standard deviation (SD)] were 38.66 ± 1.08 weeks and 8.31 ± 0.99 hours, respectively. The mean (of 44 patients), peak, and end VAS scores (mean ± SD) were 3.92 ± 0.88, 6.15 ± 1.26, and 5.53 ± 0.97, respectively, while the mean satisfaction score was 2.88 ± 1.96. The peak VAS scores and end VAS scores showed a highly significant correlation with the satisfaction scores with Spearman correlation coefficient (ordinal data) Rs values of +0.5995 and +0.6157, respectively [Figure 1], while the median VAS scores of each patient showed a very weak correlation to satisfaction scores with a Spearman correlation coefficient Rs value of 0.0273 [Figure 1]. The end stage was implicated in most patients (79.4%) as the most distressing in the entire period of labour.

Figure 1.

Correlation between satisfaction scores along x-axis and median (a) peak (b) and end (c) pain scores along y axis respectively. Rs: Spearman correlation coefficient; Df: Degree of freedom

DISCUSSION

The concept of peak-end rule, which forms the basis of this research, was conceptualised, researched, and highlighted by Nobel laureate Daniel Kahneman.[2] As per the example given, clearly relatable to us all, whether it is a movie show or a play, it is the climax and the peak events only, which are remembered by the audience. This is thought to be an exaggerated influence of system I or the rapid reflex response system of the brain where it remembers explicitly only the main important parts and keeps other things securely in the memory stores only to be extracted by system II, which comes into the forefront by deep thinking.[6]

Keeping in mind all these psychological heuristics, we intended to analyse the data of labour analgesia patients and tried relating the satisfaction scores with peak, end, and median pain scores. We chose labour analgesia for the study as we hypothesised that the effect being variable with each patient and even within a labour process, this will provide apt data to evaluate whether these heuristics work in these patients.

Our study’s results align with the peak-end rule, and we found a positive correlation between satisfaction score and peak and end pain scores rather than mean pain scores. Also, the heuristic of duration neglect persisted in this practical experiment and most patients implicated the end of labour as the most distressing rather than the entire duration. This opens up the pandora box for thinking and re-imagining the way we manage our patients.

It is imperative that we should try to keep the pain scores less than 4, but sometimes, generalising this is not feasible as already discussed due to various factors contributing to breakthrough pain.[5,7,8] Individual variability in effect, different thresholds, an increase in contractions with augmentation using oxytocin infusions, foetal head rotation, decreasing concentrations, and/or infusion flow of local anaesthetic agents, especially in the end stages of labour, can lead to “peak” and high “end” decreasing the satisfaction scores for the patient.[8,9] If the clinician plays with these psychological heuristics positively like in this case, keeping the median VAS score stable and taking care of expected “peak” moments and the “end”, by combining different modalities, this can profoundly improve the patient’s satisfaction.

The same knowledge also teaches us that by keeping the peaks and end in check, we can ignore the duration if it comes in the “mean+/-SD” spectrum. The end needs to be taken care of with tailored efforts to reduce the intensity of pain and by simultaneously encouraging patients to maintain effective pushing.[9] We should stress upon pain and psychological relief using safe options from the analgesia armamentarium.

Patient psychology is a clone of human psychology, a scared, timid, and vulnerable one. But it is amenable to safe interventions that give better patient satisfaction if we give importance to these heuristics both theoretically and practically. Thus, by specifically targeting the predictable peaks in pain and also managing the end by a tailored regimen, we can have better patient satisfaction and a better memory formation thereof for labouring patients.

Our study has a few limitations, such as a small sample size, absence of control for confounders, and exclusion of caesarean delivery, and the study needs to be validated in the future on a larger scale.

We therefore suggest that the peaks and the end should be specifically targeted along with overall pain scores while administering labour analgesia in delivering parturients. Also, we recommend further large data-based studies to form protocols for the same.

Study data availability

Can be retrieved from the corresponding author.

Disclosure of use of artificial intelligence (AI)-assistive or generative tools

No AI tool used.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.