PATHOPHYSIOLOGY AND MANAGEMENT OF BACTEREMIC SHOCK Kathryn Lnmbert, R.N. , and Emil Bluir, M.D.

1 NTRO DUCTION Kacteremic shock continues to be a pretlomi- nant in-hospital problem with 66 per ctmt of the gram negative variety.* Although surgical patients are studied more often, bacteremic shock is more prevalent and serious in medical patients. (Table 1A) The urinary tract is the most common source of bact- eremia, but iii recent years the lungs have become an increasingly important source. (Table 1 B ) The predominant microorganism is E. coli with a low incidence of shock arid the lowest mortality rate. P. aeruginona has been rising in incidence and carries the gravest prognosis. (Table 1 C )

Kathryn Lambert, B.S.N., is a graduatc of (:olumliia Lniversity School of Nursing. Columbia 1 lni Nvw York, New York. She is presently Flratl o f t h e Special Care Iinit at the Medit,al Center Hospital of Verniont. I-lrr past cxperirn(,l, in(.luiles intcmsive r a r r nursing at N t w Yllrk Citj's l'reslij-

terian Hospital and responsiliilities with tlir I ( . S. Army Hospital in Frankfurl, Gerniany. Mi-s Lainlirrt will soon begin a leave of absence to work towartls her Masters Degree in Medical Surgical Clinical Specialty a t the LlnivrrFity of Washington in Svattlv, Wadiington.

Eniil Blair, M.D.. graduatcd from the Rledii.al ( : I I I I I > ~ ~ , of Grorgia in Augusta, Georgia. After internship. graduate work and rrsitlcncy, he was apl~iintetl 111-

structor-Assistant of Surycry at the Ilni\ersity of Maryland Srhool of Mrdicinc in Baltinicbre. Rlarylantl. Sulisequen~ly. he w a s appointed Pruft Chairman of the Division of Thoracic and Cardio- vascular Surgery, and Director of Researcli at the I'niversity of Vermont College of Medicine. D r . Blair is a niember of a nrim1)er of surgical societit.. includ- ing the American College of Surgeons and the Aiiierir,an Association for the Surgery { I f Trauiria.

Twenty patients who had been under treatment elsewhere in the hospital were teferred to the Special Study IJnit with a clinical diagnosis of advanced or refractory shock. The patients had been in shock from 3 to 24 hours. The overall hospital mortality rate for grani negative bacteremic shock was 10 per cent, uhile in this group it was 40 per cent.

PATHOPHYSIOLOGY Data upon admission appears in Tables 2 and n. The mean arterial Idood pressure was no index of the state of shock, except in patients with extremely 10% values ibelow 50 mm I-lgi . Tachycardia was not seen commonly. The caidiac output was low in one-third of the patients. while in the rest it was either nor- inal or elevated. High outputs have been noted I)y other i~ivestigators.~* The high output and persistent shock have been explained as being due to shunting of blood so that tissues were not being perfused." The peripheral resistance has been found to be uniformly low, as noted both experimentally and clinically.2* Hypo- < oagulability uas a persistent feature in these patients and worse in those demonstrating a greater probability of dying.

Metabolic changes prosed to be more c onsistently informative. Defects in oxygen itietabolisni 1% ere nianifested by increases of fixed acids such as lactic and pyruvic. These were uniformly elevated nith the highest levels in patients who subsequently died

N o w m b r r 1969 67

I Table 1. Statistics: Gram Negative Bacteremias and Shock

A. Discipline Medicine Dbst. Gyn. Surgery Urol. Surgery Miscellaneous

B. Microorganism E. coli P. aeruginosa P. mirabilis Kleb.-Aerobac. Paracolon

% Bacteremia 45 20 12 I D 5

% Shock 13 20 ia 14 24

(All disciplines. Overall mortality 70-75%)

% Shock 55 17 15 10 3

% Mortality 45

70

70

a5

ao

C. Isolates in Surgical Patients E. coli 37 % P. mirabil is 20 % P. aeruginosa 20 % Kleb.-Aerobact. 15%

Paracolon 10%

Table 2. Hemodynamic Studies in 20 Refractory Shock Patients. Values as Means and S.D. S = Survivors (11) D = Deaths (91

Total Blood Volume (L)

S D

Heart Rate (per min.)

S D

5.28 2 .a9 5.46 -c 1.5

99 f 17 a6 -e 13

Cardiac Index (L /m in /M4

S D

Mean Arterial Pressure (mm Hg)

S D

Clotting Time Index

S D

3.24 .7a 3.88 c 1.31

79 2 i a 69 -c 29

-.6 c 1.3 -2.7 k 2.8

Peripheral Resistance (Units)

S D

Central Venous Pressure (mm Hg)

S D

1.24 c .39

5.4 +- 3.1

.a2 -I- 3 7

3.8 -c 3.4

Admission Death or Discharge

Admission Death or Discharge

Admission Death or Discharge

Table 3. Metabolic Alterations in Bacteremic Shock S = Survived; D = Death or Discharge

Values as Means and S.D.

PH Pa,,,, (mm Hg) S D

Lactate (mM/L)

S D 7.41 ? .14 7.35 .14 7.47 lr . l l 7.30 t .16

Pat,,, (mm Hg) 35.3 -+ 8.8 31.9 k 8.8 38.8 2 8.5 40.7 12.3

S D S D a2 r 34 58 2 ia 1.8 c .5 4.7 k 2.3

103 c 35 a4 2 43 1.3 t .7 6.4 k 1.6 Base Deficit

(mEq/L) S D

+0.7 4.0 -3.0 2 7.5 +4.4 c 4.6 -4.9 ? 7.2

I ~

regardless of therapy.jZ6 Despite oxygen elevated and often low. Similarly the pH was therapy, over 50 per cent had an arterial p02 within normal limits or elevated. These of 70 mm Hg or lower. This was not findings demonstrate significant degrees of necessarily an index of irreversibility since compensation by the pulmonary system for many of these individuals subsequently sur- the metabolic acidosis. Buffer base was vived. The arterial pC0, was only rarely significantly low and correlated with lactic

Table 4. Stages of Shock

Hernodynamic* Metabolic* Prognosis Stage Homeostasis Impairment Disorder

Compensatory Intact + to ++ 0 to + Good Fair

Decompensatory Markedly +++ ++ to +++ Poor

Refractory Absent

Decompensatory Impaired +++ t o +++ + to ++ early

late impaired k++ ++ to +++ Nil

*+ to ++++ = moderate to complete.

acid elevations. Shock is usually determined on the hasis of

hemodynamic impairments. These are impor- tant, but serve as precursors to the eventual development of shock which is a manifestation of metabolic disorders. Studies in animals with induced peritonitis gram negative bar- teremic shock in association with findings i n patients permit a tentative staging of the varying levels of shock. (Table 4) Cornpensa- tory shock is manifested by hemodynamic impairments and minimal or no metabolic disorders. The prognosis is good. As nietabo- lic disorders become worse, a decompensatory stage develops. This is a critical stage since recognition and prompt, correct therapy may yet be effective. The prognosis is fair. Relentless progression leads to late clecompen- sation and then to refractory shock. Thc prognosis is poor.

Over the years the “target organ” concept has emerged. This purports to explain irreversibility or refractoriness on a particu- lar susceptibility of an organ to shock and its reaction by elaboration of substances (hista- niine, renin, VDE, VEM, serotonin, hardy- kinin, etc.) which aggravate the shock state. While these humoral agents have been isolated and found to have effects, their precise effect on outcome is not proven. The years hace witnessed a parade of indictments--kidney, liver, lung. While there is reasonable evidence that organ sensitivity to hypoxia varies, the hypothesis that the patient’s fate rests with the ieaction of one particulai organ is CI ipl)led by oversimplification. The problem in shock is at the level of the cell-not the organ.

REFRACTORY SHOCK Clinical criteria of refractory shock are based on continued fall of the blood pressure despite “adequate volume replacement and vasocon- strictors”, such as norepinephrine. The me- tabolic criteria proved more accurate in assessing “refractoriness” and probabilities of recovery.

THERAPY Approxiniately 38 of 100 patients with gram negative bacteremias go into shock. An initial and obvious step in therapy is to prevent infections, or if present, to control them. (Table 5) Judicious surgery is particularly important regardless of the state of shock. Exercising the axiom: “the patient is too ill for surgery” is contrary to the existing situation and requirement. Rather, the true axiom is “the patient is too ill not to operate.” Broad coverage antibiosis is used initially (keflin, kanamycin, and colistin) and ad- justed when specific microorganisms are identified.

Fluid therapy with correction of metabolic imbalance continues to be the single most important item in therapy. On the basis of the lxithophysiology and its progressive nature, the restitution of perfusion with subsequent restoration of oxygen is the primary aim in treatment. Since there is no effective clinical means of directly improving perfusion, the best recourse remains alert, aggressive, and full fluid treatment. Ringer’s lactate or a balanced salt solution of some kind is a prerequisite. Laboratory aids are extremely essential and must be constantly repeated. A

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Table 5. Therapy Program

1. CORRECT DIAGNOSIS AN0 SURGERY Reduce Contamination I I . BROAD-COVER ANTlBlOSlS 100 Bacteremia--100 Shock

Initial: Kefl in + Kantrex + Colistin Cultures and Sensitivities-Repeat often.

100 SHOCK 70 DEAD

PROCEDURE

Clinical: Signs and symptoms laboratory: Cardiac output, pressures, ECG, urine

Ringer’s lactate

I . DIAGNOSE SHOCK EARLY

Blood gases, pH, base, electrolytes, Hct II. CORRECT FLUIDS-TYPE AND VOLUME

10% glucose Whole blood-rarely

Corticoids 10+ gmlday lsoproterenol

111. CORRECT DRUGS No levophed (noradrenalin)

IV. WATCH THE LUNGS No mystery

Clear airway Prevent oneumonia

Avoid excessive oxygen 100 SHOCK 30 DEAD

BETTER, BUT CAN BE IMPROVED

significant aspect is that even in elderly patients in this group, the amount of fluid required is far greater than that anticipated, and as a consequence, the concept of “hypervolemic” therapy has evolved. Of all the drugs attempted, corticoids have proved to be extremely important and should be admin- istered in pharmacologic and not in physio- logic d o ~ a g e s . ~ This means ten grams or more a day. Isoproterenol has proved to be effective, particularly in those individuals in whom the cardiac output is low and the heart rate is not at the level expected of a patient who is toxic. Other drugs are not indicated, particularly noradrenalin, or are purely exper- imental.

Hyperbaric oxygen has proved to be effective experimentally, but the clinical trials have not been successful.’ Hypothermia is not used as much now as in the past because of a better understanding of physiology in these patients. It continues to be indicated in individuals with high fever that cannot he controlled otherwise or who are extremely toxic. Experimental studies of partial perfu- sion with extracorporeal systems have been highly successful and bear significant poten- tial in application to humans.

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NURSING CARE Nursing care constitutes the single most critical item with respect to the human element. This is due to the fact that the nurse is in constant attendance to the critically ill patient and, indeed, is in a much better position to note changes in the chronology of the severe illness or modification by virtue of therapy. A major contribution of the nurse in therapy of these patients is in pulmonary care. This includes, not only the critical matter of keeping the airway cleansed, but also keeping a careful eye on the mechanical devices utilized in respiratory assist and in oxygenation. The status of the lungs has proved to be extremely significant with respect to the outcome of the patient. This is particularly important in individuals who do not have an underlying debilitating and irreversible problem, but is a potential cure, since pulmonary complications are the most common cause of death. The critical nature of shock does not obviate the need for excellent physical care but rather emphasizes this. Because peripheral circula- tion is usually impaired, frequent turning and positioning is important, as well as brisk rubbing of the back and any pressure areas. The nurse can help the patient maintain a

AORN Journal

sense of dignity, jncluding cosmetic nieasui es in their plan of care. These patients, ~liough in a severe shock state, most often at‘ quite conscious and aware of their surrouritlings.

Many patients with gram negativr bac- teremic shock necessitate isolation foi protec- tion of other patients in the Intensi\r Care linit. This adds a challenge to the nuiw in the total care of the patient because she must he aware of and attempl to allay a patient’s fears, not only of being critically ill, but also of being isolated from the other patients arid his own family. The nurse-patient ratio with respect to time is highest in the Intensive Care IJnit with such critically ill patient.; and they

come to rely upon her far more than anyone else. Another important segment of the nurse’s role is to reassure the patient and serve as a buttress between him and the unknown fears precipitated by modern and often noisy contrik ances.

The care of the patient in gram negative shock requires the greatest skill, knowledge, and perseverence of the nurse. Her knowl- edge includes the highest standards of quality nursing care and also extends to skill with respect to the modern, highly complex, electronic and other mechanical devices com- monly utilized and urgently required in these severely ill individuals.

KEFERENCES

1. Eliert, R. V., and Abernathy, R. S., “Septic Shock,” Fed. Proc. (Suppl 91, Vol. 20, 1961, p. 170-184. 2. MacLean, L., et al., “Patterns of Septic. Sllock in hfan-A Detailed Study 56 patients,” ,4nrr, Surg,, Vol. 166, Oct., 1967, p. 543-562. 3. Del Guercio, L. R., et al., “Pulmonary and S) sternic Arteriovenous Shunting in Clinical Septic Shock,” Third Int’l Conf. Hyperbaric Med., Nat’l Arad. %I., Washington, D. C., 1966. 4. Blair, E., et al., “Hypothermia in narterelnic Shock,” A.M.A. Arch. Surg., Vol. 89, Oct. 1964, p. 619-629.

5. Weil, M. H., and Broder, G., “Excess Lactate. An Index of Irreversibility in Human Patients,” Nat’s Acad. Sci. Nat’l Res. Council Report, 1965. 6. Blair, E., CowleY, R. A., and Tait, M.7” Refractory Septic Shock in Man. Role of Lactate and Pyruvate Metabolism and Acid-Base Balance in Prognosis,” Am. Surg., Vol. 31, Aug., 1965, p. 537-54Q. 7. Schurner, W., and Sperling, R., “Shock and its Effect ol, the ,-.ell,>, 1, nm. ~ ~ d . A ~ ~ ~ . , vol. 205, July 22. 1968, p. 215-219. 8. Blair, E.. et al., “Hyperbalic Oxygenation in the Treatment of Experimental Shock,” Am. J . Surg., Vol. 110, Sept. 1965, p. 348-354.

DISINFECTANT F O R G R A h f - N E G A T I V E M I C R O O R G A N I S M S

Topical use o f a wide-spectrum tlisinjcctant such as povidone-iodine or chlorhexidine instead of hexachlorophene is (I potentially c.ffective zvay to prevent cross-contamina- t ion wi th gram-negative bacilli. Hexachlorophene is much less active against gram- negative bacilli t han against grani-positive cocci, and the gram-negative organisms apparently begin to flourish onc e the gram-poAitive cocci are effectively suppressed.

Antibiotics effective against gram-positive cocci control injt-ction wi th Stretococcus pyogenes and wi th Staphylocorc i i s aiLrc’u5, but pri mit the proliferation of gram- negative bacilli and development of grain-n<,gative injections.

Gram-negative bacilli, especially Pseudomonas aeruginosa, are the predominant pathogens of an increasing nurnlwr of pa t imt s treated with immunosuppressive drugs.

Such organisms also pose a ptrrticular hazard t o other high-risk patients including the newly-born and small infants.

MODERN MEDICINE (E . 1. L. I,owbury, M . B., Cram-negative bacilli on the skin, Brit. J. Derm. 81 ( suppl . I): 55-61, 1969)

November 1969 71