CHANGES IN SERUM ZINC LEVELS IN RELATION TO BLOOD PRESSURE DURING ANAESTHESIA

1. Associate Professor, Department of Pharmacology, Nepalgunj Medical College, Chisapani (Banke) 2. Senior Resident, Department of Anaesthesiology, J.N. Medical College, A.M.U., Aligarh (U.P.), India. 3. Lecturer, Department of Anaesthesiology, J.N. Medical College, A.M.U., Aligarh (U.P.), India. Address for correspondence : Dr. H. K. Garg, Associate Professor, Department of Pharmacology Nepalgunj Medical College, Chisapani (Banke) Nepal. Ph. No.: 081-29119, Fax: 081-21152


INTRODUCTION
Zinc is a trace metal which may have a close association with blood pressure.Serum zinc levels are likely to get disturbed in hypertension.The present study was designed to explore the possibility of a relationship between serum zinc levels and changing BP during G.A.

MATERIALS AND METHODS
Fifty patients of similar age and either sex were entered into the study.These patients, who were to be operated for various ailments, were divided into two groups of 25 subjects each.The control group (Group I) included normotensive subjects while the study group (Group II) included hypertensive subjects.Hypertensives were not operated till their BP came within normal range.Individuals with systemic or metabolic disorders or those receiving medications likely to affect serum zinc levels were excluded.Detailed history was taken and clinical examination and preoperative assessment was done in all cases.All patients were routinely investigated.Pulse rate and blood pressure were recorded in both upper limbs preoperatively, 10 minutes after intubation, at the maximum rise of BP and 24 hours after operation.BP was monitored every 10 min during operation, and the maximum increase ofBP was thus detected.5 ml.venous blood samples were drawn simultaneously for the purpose of correlating BP and serum zinc levels.Preanaesthetic medication was given using diazepam and pentazocine 15 mg, i.v, slowly.Induction was done with a sleep dose of thiopentone sodium I.V. slowly.Relaxation was done with succinylcholine, 1.5 mg/ kg of body weight.The flow-in oxygen and nitrous oxide were-maintained in a ratio of 40:60.Maintenance of anesthesia was achieved with vancuronium bromide and reversal was carried out using, neostigmine, 0.05mg/kg and inj.atropine, 0.02mg/kg body weight in all patients.Blood samples were kept at room temperature till serum separated, which was then stored at 4° C. Serum zinc was estimated by GBC 902 double beam, atomic absorption spectrophotometer.Statistical analysis of the data was done by Student's 'f test.

RESULTS
Mean systolic BP in the control group showed a rise ten minutes after intubation, (p < 0.001) No such change was seen in the study group.At maximum rise ofBP systolic BP increased in normotensives (p < 0.001, Table I), but no change was seen in the study group (Table II).In the postoperative period, however a different pattern

DISCUSSION
The importance of normal serum zinc levels in the body cannot be overemphasized, as zinc has been found to be essential for growth and development, as well as for the general well being of an individual. 2 Zinc has been found to play an important role in the maintenance of blood pressure in rats. 3In the present study an attempt has been made to find out whether operative stress or general anaesthesia alter serum Zn levels.The serum zinc levels were significantly higher in hypertensive subjects as compared to normotensive subjects before anaesthesia.
The alteration in serum zinc levels during anaesthesia could be due to many factors.It could be due to the mobilization and redistribution of zinc.Redistribution of zinc was observed in hypertensives undergoing treatment with clopramide.Plasma, erythrocyte and W.B.C. levels of zinc registered an increase 8 weeks after initiation of therapy. 4Genetic predisposition to the effects of anaesthetic agents may be another reason of changes in zinc levels.Hypertension induced by deoxycorticosterone acetate was associated with higher serum zinc levels only in spontaneously hypertensive rats and not in normal rats. 3Yet another reason could be surgical stress.Surgical stress triggers the release of various mediators, possibly increasing hepatic zinc deposition, thus decreasing plasma and skin zinc levels. 5Studies on diverse tissue trauma such as following coronary bypass surgery, myocardial infarction 7,8 and during fatigue 9 have shown that there is a significant decrease in serum zinc levels.
In the present study, the changes observed in serum zinc levels were uniform and correlated with specific events, namely, stress of intubation, stress of increase in blood pressure or with postoperative stress.Patterns in normotensives and hypertensives were also different.While a significant fall in zinc level at one time or the other was always observed in normotensives, serum zinc levels increased in hypertensive patients.Moreover, there are complex relations between zinc and arterial pressure, through the angiotensin converting enzyme (ACE) system and hormones like glucocorticoids and catecholamines used in the regulation of arterial pressure. 9Another factor, which may play a role in changes in serum zinc, is intraoperative hyperthermia. 10 However, determination of zinc levels in hair and saliva also may help to give a clearer picture.The Journal of Nepal Medical Association (JNMA) is consolidating all its efforts in upgrading the quality of the Journal that could subsequently lead to international recognition and indexing.The necessary changes in editorial policy have already come into effect and activities (e.g., peer reviewing, copy editing, statistical review etc) pertaining to it have been initiated.However, the Journal is currently short in funds to effectively conduct these activities.Hence, fund raising has become inevitable but as to how best funds could be raised and mobilized is still a question.Among those thought of are creating a revolving fund and/or acquiring a physical facility and renting them out so that the incurred interest and/or rent could be utilized to support the activities.
In this regard the Journal looks forward to the opinions of its valued readers.Comments and queries may be forwarded to the Chief Editor of Journal.

Table I Serum Zinc Levels in Normotensive Patients During Anaesthesia (Data are mean
± s.e.m., n = 25) * P < 0.001, vs pre-operative

Table II Serum Zinc Levels in Hypertensive Patients During Anaesthesia (Data are mean
± s.e.m., n = 25) * P < 0.02, ** p < 0.01, *** p < 0.001, vs pre-operative was observed.Systolic BP in the study group fell (p < 0.02), while no change was observed in the control group.

Table III Fall in Serum Zinc Levels (ug/dl) in Normotensive Patients (Data are mean
± s.e.m.) * P < 0.05, ** p < 0.01, *** p < 0.001, vs pre-operative On the basis of fluctuations in serum zinc levels, hypertensive subjects were divided into two subgroups: a) Subgroup I: -Twelve hypertensive subjects showed a rise in serum Zn level at maximum rise of BP (p < 0.01).In the postoperative period, serum Zn fell (TableIV).b)SubgroupII:-Thirteenhypertensives did not show any significant change in serum Zn throughout the study period (TableIV).