Cardiovascular Depressant Effect of Protamine Sulphate: Experimental Study and Clinical Implications

Thorax: first published as 10.1136/thx.31.3.320 on 1 June 1976. Downloaded from

Thorax (1976), 31, 320.

Cardiovascular depressant effect of protamine sulphate: experimental study and clinical implications

MONEIM A. FADALI, CHARLES A. PAPACOSTAS, JAMES J. DUKE, MARK LEDBETTER, and MARY OSBAKKEN Department of Surgery, Section of Thoracic and Cardiac Surgery, and Department of Pharmacology, Temple University Health Sciences Center, Philadelphia, Pennsylvania, USA

Fadali, M. A., Papacostas, C. A., Duke, J. J., Ledbetter, M., and Osbakken, Mary (1976). Thorax, 31, 320-323. Cardiovascular depresant elEect of protamine sulphate: experimental study and clinical implications. The mechanisms underlying protamine-induced hypotension and bradycardia were the subject of this investigation. Six groups of dogs with intact circulation were tested in controlled circumstances with various drugs. The following parameters were observed: femoral arterial pressure, central venous pressure, left ventricular pressure and its rate of rise, left ventricular contractile element velocity of shortening, maximal Vce, and cardiac output. The six groups were studied under these pharmacological conditions: ganglionic and adrenal medullary block with hexa- parasympathetic blockade by atropine sulphate, methonium chloride, postganglionic http://thorax.bmj.com/ alpha and beta adrenergic receptor block by phenoxybenzamine and propranolol respectively, and depletion of endogenous histamine by compound 48/80 (a condensation product of p-methoxyphenethyl methylamine with formaldehyde). The last group was put on extracorporeal circulation to isolate the vascular tree from the heart. The effect of the drug on this isolated vasculature was observed by recording the femoral arterial pressure. Our findings show that the hypotension and bradycardia are produced by a direct effect of protamine on the myocardium and peripheral vascular system. on October 1, 2021 by guest. Protected copyright.

Heparin is necessary for the performances of extra- total cardiopulmonary bypass. All dogs were corporeal circulation. Protamine sulphate is used anaesthetized with thiopental sodium, intubated to neutralize heparin at the completion of cardio- and ventilated by a Harvard mechanical respirator. pulmonary bypass (Hurt et al., 1956). Hypotension and bradycardia, the common side effects of DOGS WITH INTACT CIRCULATIONS In groups A-F protamine, can be detrimental to postcardiotomy a transsternal incision through the left fifth and patients (Jaques, 1949; Egerton and Robinson, right fourth interspaces was used to expose the 1961). The mechanism of action of protamine on heart. An electromagnetic flow probe (Statham) the intact cardiovascular system and isolated was placed around the ascending aorta to measure peripheral vasculature has been investigated and is cardiac output (CO). Polyethylene catheters were the subject of this paper. introduced into the left ventricular cavity, left femoral artery, and left femoral vein to measure METHODS left ventricular pressure (LVP), its rate of rise A total of 40 adult mongrel dogs weighing 14 to (dp/dt), the femoral arterial pressure (FAP), and 23 kg were divided into seven groups. Six groups central venous pressure (CVP) respectively. The (A-F) of six dogs each had intact circulations, left ventricular contractile element velocity (Vce) and the seventh group (G) of four dogs was put on was determined from isovolumic pressure (IP) and 320 Thorax: first published as 10.1136/thx.31.3.320 on 1 June 1976. Downloaded from

Cardiovascular depressant eflect of protamine sulphate 321 dp/dt; maximal Vce (V max) was obtained by RESULTS construction of an IP to Vce curve and extra- The results are summarized in the Table. Group polation to zero load (Mason, Spann, and Zelis, A dogs receiving no premedication had an appreci- 1970). Electrocardiograms were always recorded. able reduction of all measured indices: a mean Each animal in groups A-F received intraven- drop of 39% in mean FAP, 44% in IP, 38% in ous heparin, 5 mg/kg, followed by protamine dp/dt, 31% in Vmax, and 33% in CO. These re- sulphate, 10 mg/kg. Group A animals had both duced values were noted in every animal and carotid arteries exposed and clamped proximal were statistically significant. Simultaneous to the sinus region to test the carotid sinus reflex bilateral clamping of the carotid arteries proximal after heparin-protamine administration. Groups to the carotid sinus reversed the hypotensive B-F were pretreated intravenously with these bradycardic effect of protamine in all six dogs. drugs: group B was given hexamethonium However, the hypotension and bradycardia re- chloride, 10mg/kg, to block the autonomic ganglia curred after removing the clamps. and epinephrine release by the adrenal medulla. Medication with hexamethonium in group B, Group C received atropine sulphate, 0.5 mg/kg, to atropine in group C, phenoxybenzamine in group block postganglionic parasympathetic receptors D, propranolol in group E, and compound 48/80 (vagal block). Norepinephrine, 2 ,tg/kg, was given in group F failed to abolish or reverse the pro- after 10 minutes to test the vagal block. Ordin- tamine effects noted in control animals, group A. arily, an increase in blood pressure would be In each group shown in the Table the mean de- followed by reflex bradycardia; however, an creases are reproducible and significantly differ atropinized dog would have no reflex bradycardia from zero. The small differences among the mean following an increased blood pressure. Group D percentage decreases for FAP in the six groups dogs were given phenoxybenzamine (Dibenzyline) just met statistical significance at the 5% level 5 mg/kg and a 30-minute waiting period to but were not clinically important (one-way analysis achieve complete alpha blockade. In group E, of variance applied to logarithms). Differences propranolol (Inderal), 1 mg/kg, was given with a among the mean percentage decreases in CO, IP, 10-minute waiting period for complete sym- dp/dt, and Vmax were smaller and of no statistical pathetic beta blockade. Group F dogs were given significance. http://thorax.bmj.com/ compound 48/80 (a condensation product of p- In group G animals with isolated peripheral methoxyphenethyl methylamine with formalde- vasculature, protamine continued to reduce FAP hyde), 0-1 mg/kg, slowly over a period of 20 at an average of 24% which is similar to that in minutes to deplete endogenous histamine (Paton, the other groups. 1951; Papacostas, Loew, and West, 1959). Before In all seven groups there were no significant and after heparin-protamine administration the pH changes after heparin-protamine administra- blood pH was tested in one animal of each group. tion. The four dogs in group G were cannulated and put on extracorporeal circulation. The heart was on October 1, 2021 by guest. Protected copyright. isolated by clamping the ascending aorta and DISCUSSION pulmonary artery. The effect of protamine on the The mechanism responsible for the hypotensive vascular tree was measured by observing the FAP and bradycardic effects of protamine sulphate before and after injection of 10 mg/kg of pro- remains a controversial topic. To answer some of tamine into the arterial inflow of the extra- these questions the clinical situation was simulated corporeal pump. in dogs by giving the heparin followed by pro-

T A B L E MEAN PERCENTAGE CHANGE IN DIFFERENT PARAMETERS FOLLOWING HEPARIN.PROTAMINE ADMINISTRATION IN SEVEN ANIMAL GROUPS _ Group A Group B Group C Group D Group E Group F Group G Premedication None Hexa- Atropine Phenoxy- Propranolol Compound Extracorporeal methonium benzamine 48/80 circulation Mean FAP (mmHg) -39 -24 -29 -29 -31 -25 -24 IP (mmHg) -44 -33 -42 -38 -30 -41 - dp/dt -38 -32 -40 -36 -45 -41 _ V(mdlsec)max -31 -27 -33 -27 -30 -27 CO (ml/min) -33 -26 -29 -28 -32 -32 __ Thorax: first published as 10.1136/thx.31.3.320 on 1 June 1976. Downloaded from

322 M. A. Fadali, C. A. Papacostas, J. J. Duke, M. Ledbetter, and Mary Osbakken tamine., Group A animals tested the concept of tated. The techniques of Mason et al. (1970) were neurogenic reflex by some authors (Egerton and used in the present study, and the maximal Robinson, 1961; Minker and Koltai, 1964). Proxi- velocity was computed from the instantaneous mal carotid artery clamping reversed the hypo- correlation of the rate of pressure developed in tension and bradycardia produced by protamine the left ventricular cavity during the isovolumic which attests to the integrity of the carotid sinus phase of contraction. All animals in groups reflex mediated by autonomic pathways. To test A-F showed a marked decrease in myocardial further the neurogenic reflex concept different contractility after protamine injection. steps of the autonomic pathways were blocked The findings in group G provided further through premedication. In group B, the autonomic evidence for the direct effect of protamine on the ganglia and the adrenal medulla were blocked by vascular tree. Protamine administration into the hexamethonium chloride. The femoral arterial arterial inflow of the extracorporeal circulation pressure, left ventricular pressure, its rate of rise, was followed by a significant drop of femoral isovolumic pressure, maximal left ventricular con- arterial pressure. tractile element velocity, and cardiac output were Acid-base changes are not involved because no substantially reduced following protamine adminis- significant pH changes were recorded after tration, a response similar to that in dogs with heparin-protamine injection. intact ganglia (group A). Thus protamine does not From the results we conclude that the cardio- produce its cardiovascular effects through blocking vascular responses to protamine sulphate the autonomic ganglia. Atropine sulphate was administration are due to a direct effect of the used to block postganglionic parasympathetic drug on the myocardium and vasculature. receptors in group C dogs to eliminate possible This experimental conclusion was clinically reflex cholinergic effect of protamine. Again, as in applied to our patients receiving protamine in- group A, the animals showed hypotension and fusion at the termination of cardiopulmonary depression of myocardial contractility when pro- bypass. To prevent hypotension, the following tamine was given. Alpha blockade by phenoxy- measures were successful in the majority of cases: benzamine in group D and beta blockade by (1) Administration of inotropic agents, in propranolol in group E both failed to avert the particular calcium chloride or calcium gluconate;http://thorax.bmj.com/ hypotension and bradycardia after protamine in- isoproterenol or epinephrine to patients without jection. The findings in groups A-E do not support serious tachycardia or significant arrhythmias. the involvement of neurogenic reflexes or Norepinephrine might be used since it reverses the adrenergic receptors in protamine-induced peripheral vasodilating effects of protamine with- hypotension and bradycardia. out producing tachycardia. (2) If central venous Sensitivity and histamine release due to pro- and left atrial pressures permit, a fluid load is tamine was proposed by Shelley, Hodgkins, and administered to compensate for the expanded Visscher (1942). Kern and Langner (1939) could capacity of the vascular tree. not produce protamine sensitivity in guinea-pigs on October 1, 2021 by guest. Protected copyright. despite several intraperitoneal injections. Jaques We are grateful to Dr. Stanley Schor (Ph.D.), chief (1949) found that histamine-free protamine pre- and professor, Department of Biometrics, Temple parations could still elicit hypotension. Presently, University Health Sciences Center, for the statisttal depletion of endogenous histamine was produced analyses. in group F dogs by premedication with compound Support for this work was received partly from the 48/80. The hypotension and bradycardia was again Department of Surgery, Temple University Health elicited following protamine injection. This Sciences Center. reinforces the findings of Jaques (1949) and Kern and Langner (1939) that histamine has no significant etiological role in these effects of protamine. REFERENCES Myocardial contractility depression following Egerton, W. S. and Robinson, C. L. N. (1961). The protamine administration was demonstrated by anti-heparin, anticoagulant and hypotensive pro- Goldman, Joison, and Austen (1969) but disputed perties of hexadimethrine and protamine. Lancet, by Gourin et al. (1971a), who even advocated an 2, 635. inotropic effect of the drug on dog's myocardium. Goldman, B. S., Joison, J., and Austen, W. G. (1969). Cardiovascular effects of protamine sulfate. By estimating the maximal velocity of left Annals of Thoracic Surgery, 7, 459. ventricular contractile element shortening, the Gourin, A., Streisand, R. L., Greineder, J. K., and contractile state of an intact heart can be quanti- Stuckey, J. H. (1971a). Protamine sulfate admin- Thorax: first published as 10.1136/thx.31.3.320 on 1 June 1976. Downloaded from

Cardiovascular depressant ejfect of protamine sulphate 323

istration and the cardiovascular system. Journal Minker, E. and Koltai, M. (1964). Effect of protamine of Thoracic and Cardiovascular Surgery, 62, 193. sulphate on the transmission processes in per- and Stuckey, J. H. (1971b). Total cardio- ipheral sympathetic ganglia. Acta Physiologica pulmonary bypass, myocardial contractility, and Academiae Scientiatum Hungaricae, 24, 365. the administration of protamine sulfate. Journal Papacostas, C. A., Loew, and West, G. B. (1959). of Thoracic and Cardiovascular Surgery, 61, 160. Studies on the toxicity of a histamine liberator, Hurt, R., Perkins, H. A., Osborn, J. J., and Gerbode, compound 48/80. Archives Internationales de F. (1956). The neutralization of heparin by pro- Pharmacodynamies, 120, 353. tamine in extracorporeal circulation. Journal of Paton, W. D. M. (1951). Compound 48/80: A potent Thoracic and Cardiovascular Surgery, 32, 612. histamine liberator. British Journal of Pharma- Jaques, L. B. (1949). A study of the toxicity of the cology, 6, 499. protamine, salmine. British Journal of Pharma- Shelley, W. B., Hodgkins, M. P., and Visscher, M. B. cology, 4, 135. (1942). Studies on the toxicity of protamine. Pro- Kern, R. A. and Langner, P. H. (1939). Protamine ceedings of the Society of Experimental Biology and allergy. Journal of the American Medical and Medicine, 50, 300. Association, 113, 198. Mason, D. T., Spann, J. F., Jr., and Zelis, R. (1970). Quantification of the contractile state of the in- Requests for reprints to: Dr. Moneim A. Fadali, tact human heart. American Journal of Cardi- 2661 Locksley Place, Los Angeles, California 90039, ology, 26, 248. USA. http://thorax.bmj.com/ on October 1, 2021 by guest. Protected copyright.