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65: Hypotension and Shock

I. PROBLEM

The nurse reports that an infant may be hypotensive and is showing signs of shock. Hypotension (diminished blood pressure [BP]) is distinct from shock, a clinical syndrome of inadequate tissue perfusion with the clinical signs noted in Section II.B. While hypotension frequently accompanies shock, there is no consensus on the exact definition of hypotension in the neonate. Normal BP values for extremely premature infants are also debated. Data are conflicting for the exact BP that requires treatment for every gestational, postnatal age, and infant weight. Some define hypotension as a BP >2 standard deviations below normal for age or below the fifth percentile. For a rapid reference for premature and term infants BP ranges, see Table 65–1 and for more detailed BP values, see Appendix C.

Table 65–1.RAPID REFERENCE BLOOD PRESSURE RANGES IN PREMATURE INFANTS ACCORDING TO BODY WEIGHT AND TERM INFANTS BASED ON BIRTH (DETAILED BLOOD PRESSURE VALUES ARE FOUND IN APPENDIX C)
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Table 65–1.RAPID REFERENCE BLOOD PRESSURE RANGES IN PREMATURE INFANTS ACCORDING TO BODY WEIGHT AND TERM INFANTS BASED ON BIRTH (DETAILED BLOOD PRESSURE VALUES ARE FOUND IN APPENDIX C)
Birthweight (g) Mean (mm Hg) Systolic (mm Hg) Diastolic (mm Hg)

Premature infants
501–750 38–49 50–62 26–36
751–1000 35.5–47.5 48–59 23–36
1001–1250 37.5–48 49–61 26–35
1251–1500 34.5–44.5 46–56 23–33
1501–1750 34.5–45.5 46–58 23–33
1751–2000 36–48 48–61 24–35

Term infants
Day 1 31–63 46–94 42–57
Day 2 37–68 46–91 27–58
Day 3 36–70 51–93 26–61
Day 4 41–65 60–88 34–57

Based on data from Hegyi T, Carbone MT, Anwar M, et al. Blood pressure ranges in premature infants: I. The first hours of life. J Pediatr. 1994;124:627; and Kent A, Kecskes Z, Shadbolt B, Falk MC. Normative blood pressure data in the early neonatal period. Pediatr Nephrol. 2007;22:1335–1341.

II. IMMEDIATE QUESTIONS

  1. What method of measurement was used? If a BP cuff was used, be certain that it was the correct width (ie, covering two-thirds of the upper arm). A cuff that is too large gives falsely low readings. If measurements were obtained from an indwelling arterial catheter, a “dampened” waveform suggests air in the transducer or tubing or a clot in the system, and the readings are inaccurate (see also Selected Reference).

  2. Are signs of shock present? Signs of shock include tachycardia, poor/reduced perfusion, prolonged capillary refill time (>3–4 seconds), respiratory distress, poor tone, poor color, cold extremities (with a normal core temperature), lethargy, narrow pulse pressure, apnea and bradycardia, tachypnea, metabolic acidosis, and weak pulse.

  3. Is the urine output acceptable? Normal urine output is ∼1–2 mL/kg/h and is decreased in shock due to decreased renal perfusion. If the BP is low but the urine output is adequate, aggressive treatment may not be necessary as renal perfusion is adequate. (Note: An exception involves the infant with septic shock and hyperglycemia with osmotic diuresis.)

  4. Is ...

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