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Abstract

Abstract


This study aims to determine the frequency of perioperative hypertension and its types (pre, intra and post-operative) hypertension in patients admitted for surgical procedures. This was a cross-sectional study conducted between the years 2012-2013 at the Aga Khan University Hospital, Karachi. Patients admitted for any surgical procedure during this time were included. Perioperative hypertension has been defined as systolic blood pressure of >140 mm Hg or a diastolic blood pressure of >90 mm Hg or whose blood pressure increased by 20% during surgery. A total of 428 surgical procedures were reviewed for the study. Overall perioperative hypertension was present in 231 (54%) of the patients. In the sample, 91 (21.7%) had pre-operative hypertension, 126(29.4%) reported pre-surgery hypertension, 24(5.6%) had intra-operative hypertension and 63(14.7%) had post-operative hypertension. Mean pain score was 1.43(1.4) v 1.25(1.2) in those with postoperative hypertension v no post-operative hypertension (p value 0.009).
Keywords: Hypertension, Per operative, Surgery.

Introduction

Perioperative hypertension occurs in 25% of hypertensive patients that undergo surgery.1,2 Hypertension is commonly encountered in pre-operative assessments. 3 Perioperative hypertension is defined as a sustained elevated blood pressure (BP) typically >140/90mm Hg immediately before, during or after a surgical procedure. 2,4 In a survey conducted amongst anaesthesiologists, Preoperative Hypertension was recognised as the most common avoidable medical indication for postponing anaesthesia and surgery. Though widely investigated in the 90s, we were unable to find more recent data on the prevalence of perioperative hypertension and no data of its prevalence in Pakistan. It is therefore important to determine the frequency of perioperative hypertension in patients admitted for surgical procedures and also to determine the prevalence of the types of preoperative hypertension. Additionally we wanted to see the proportion of patients with white coat hypertension in the study and to what degree pain plays a role in increasing blood pressure post-operatively.

Methods and Results

This was a cross-sectional study, conducted from December 2012 to December 2013 at the Aga Khan University Hospital Karachi, Pakistan, after taking approval from the Aga Khan University's ethical committee (ERC letter: 2403- Med-ERC-12). International classification of diseases ICD 9 CM was used to compile medical record data of patients admitted at the hospital for any surgical procedure. A minimum sample size of 237 patients was required for a proportion of patients to have 19% perioperative hypertension presented in the OR, with bound on error of 5% and alpha of 5%.5 All adult patients aged 18 years and above, admitted for any surgical procedure were included. Patients were further divided into two age groups of 18-40 years and >40 years of age. Perioperative hypertension has been defined as a consistent BP measured at systolic blood pressure >140 mm Hg or a diastolic blood pressure at>90 mm Hg, recorded before, during or immediately after surgical procedures.6 It was further divided into pre, intra and post-operative hypertension. Pre-operative hypertension is defined as patients with elevated BP >140/90 mm Hg recorded before surgery, measured during pre-operative anaesthesia assessment or in the ward the night before surgery. Pre-surgery hypertension is defined as elevated BP >140/90 mm Hg recorded in the surgical preparation room immediately before surgery. Intra-operative hypertension is defined as a rise in patients' blood pressure during surgery while under anaesthesia. A preoperative measurement of >20% rise in blood pressure or when the blood pressure is recorded at>140/90,is considered as intra-operative hypertension. 4  Postoperative hypertension has been defined as a significant increase in BP immediately after surgery with a blood pressure of>140/90 mm Hg. Pain was measured using the numerical rating scale of pain (Numeric Rating Scale-11) where the patient scores his/her pain rating from 0 (no pain) to 10 (worst imaginable pain). 7 Pain scores were recorded immediately after surgery, in recovery room and within 24 hours. Frequency and percentage was used to report categorical variables and mean and standard deviation for quantitative variables. Student t-test was used to compare those with and without perioperative hypertension. Statistical package for social sciences was used for analysis (version 19.1). The data of all the 428 patients was included in the final analysis. This included data from 334 (87%) elective and 87 emergency surgeries. The mean age8 of patients was 41.3 (16.2%) and 163(38.1%) were males. Out of these 97 (22.7%) were known hypertensive, 20 (4.7%) were known diabetic and 20(4.7%) had known ischaemic heart disease. In the types of general anaesthesia: 344 (80.4%) were given general anaesthesia, 35(8.2%) were given regional and 49(11.4%) were given local anaesthesia. Pain control was well managed with only 4.3% reporting a pain score of >3 in recovery. Overall perioperative hypertension was recorded in 231 (54%) of the cases. Further classification of perioperative hypertension is detailed in Table-1.



The stratification of patients in ages 18-40 years and >40 years, revealed out of these 95 (41.3%) and 136(58.7 %) respectively had perioperative hypertension.



Table-2 compares post-operative pain scores in recovery after 12 and 24 hours in patients with and without postoperative hypertension. Pain score was relatively high in patients with post-operative hypertension in recovery room; Mean pain score 1.43(1.4) v 1.25(1.2) in those with post-operative hypertension v no post-operative hypertension (p = 0.009).

Discussion

Our study reports the frequency of perioperative hypertension at 54%, which is significantly higher than previously reported prevalence ranging from 4-35%.9 The prevalence of intra-operative hypertension in our study is 5.4% which is lower than the previously reported figure of 50% of patients, whose hypertension was not known, showed preoperative hypertension during clinic anaesthesia assessment. One possible explanation is that hypertension is being under-reported in Pakistan, with majority of people only getting a full work up done only during clinic visits prior to surgery. This might be one reason for the high frequency of undiagnosed hypertension reported in this study. Advanced anaesthetic agents, better post-operative pain control medications and devices have revolutionized pain management in the past two decades. 11 Although the pain score in our study was