13.3 Acid-Base, Pain & Healthcare-Acquired Conditions
Key Takeaways
- Shock commonly produces lactic metabolic acidosis; rising PaCO2 on top of metabolic acidosis signals fatigue or failure and demands urgent airway support.
- Interpret pediatric ABGs as pattern recognition—acidosis versus alkalosis, metabolic versus respiratory, and degree of compensation—then link the pattern to perfusion, ventilation, and electrolyte context.
- Developmentally appropriate pain assessment uses tools matched to age and cognition (NIPS/CRIES, FLACC, Wong-Baker, numeric scales) plus behavioral and physiologic cues.
- CLABSI, ventilator-associated events, and pressure injuries are preventable healthcare-acquired conditions with pediatric-specific bundle and skin-risk strategies.
- Nursing prevention—line care, head-of-bed and oral care for ventilated children, and scheduled pressure redistribution—directly protects outcomes and is heavily tested as systems-level critical care practice.
Acid-Base Patterns in the Shocked or Inflamed Child
Arterial blood gas (ABG) interpretation is a multisystem skill on the CCRN-Pediatric exam because shock, sepsis, and respiratory failure rewrite acid-base balance quickly. Start with pH, then decide whether the primary process is metabolic or respiratory, then judge compensation.
| Disorder | pH | Primary change | Common pediatric ICU context |
|---|---|---|---|
| Metabolic acidosis | ↓ | ↓ HCO3− (base deficit ↑) | Lactic acid from shock, ketoacidosis, diarrheal HCO3− loss, hyperchloremia after large saline loads |
| Metabolic alkalosis | ↑ | ↑ HCO3− | Prolonged vomiting, loop/thiazide diuretics, volume contraction |
| Respiratory acidosis | ↓ | ↑ PaCO2 | Hypoventilation, fatigue in bronchiolitis/asthma, opioid effect, inadequate ventilator support |
| Respiratory alkalosis | ↑ | ↓ PaCO2 | Pain, anxiety, early PE, iatrogenic overventilation |
In septic or hypovolemic shock, anaerobic metabolism generates lactic metabolic acidosis. A falling lactate with improving capillary refill is reassuring; a rising lactate despite "normal" blood pressure still means inadequate oxygen delivery. Infants may also develop hypoglycemia-related metabolic derangements during sepsis—always check glucose when interpreting a severe acidosis.
Compensation and Mixed Disorders
Respiratory compensation for metabolic acidosis is hyperventilation that lowers PaCO2. If a child with known lactic acidosis suddenly shows a rising PaCO2 and falling pH, suspect respiratory muscle fatigue or impending failure—prepare for airway support rather than attributing everything to "just metabolic acidosis." Metabolic compensation for chronic respiratory acidosis (renal HCO3− retention) takes longer and is less often the acute shock story. Mixed disorders are common: septic shock with pneumonia can combine metabolic acidosis and respiratory acidosis, producing profound acidemia. Base deficit and lactate complement the ABG by quantifying metabolic acid load from hypoperfusion.
Worked ABG Links to Shock Care
Example: pH 7.18, PaCO2 28 mmHg, HCO3− 10 mEq/L, lactate 6 mmol/L in a toddler with delayed refill. Pattern = partially compensated metabolic acidosis from hypoperfusion—treat shock, not the number alone. Example: pH 7.22, PaCO2 68 mmHg, HCO3− 27 mEq/L in a tiring infant with bronchiolitis = acute respiratory acidosis—support ventilation. Example: after massive 0.9% saline resuscitation, hyperchloremic metabolic acidosis can persist even as lactate falls; this is one reason balanced crystalloids are preferred when large volumes are required.
Developmentally Appropriate Pain Assessment and Management
Uncontrolled pain amplifies catecholamine release, impairs sleep and immunity, and confounds neurologic and perfusion exams. Because many PICU patients cannot self-report, tool selection by developmental stage is mandatory:
| Population | Typical tools / approach |
|---|---|
| Neonates | NIPS, CRIES, PIPP; watch facial tension, cry, tone, vital-sign shifts |
| Infants/nonverbal children | FLACC (Face, Legs, Activity, Cry, Consolability) |
| Preschool/early school age | Wong-Baker FACES when cognitively able |
| Older school age/adolescents | Numeric rating scale (0–10) plus self-report quality descriptors |
| Intubated / deeply sedated | Behavioral tools plus contextual cues; avoid assuming "no pain because quiet" |
Assess pain before and after procedures, with routine cares, and when vital signs change without a clear perfusion explanation. Nonpharmacologic strategies—swaddling, sucrose in eligible neonates, parental presence, positioning, distraction—complement analgesics. Opioids, acetaminophen, NSAIDs (when perfusion and renal/bleeding risk allow), regional techniques, and sedation plans should be goal-directed. Reassess with the same tool so trends are valid. A common trap is labeling a nonverbal child as "agitated from hypoxia only" without a structured pain score—hypoxia and pain often coexist and both need treatment.
Healthcare-Acquired Conditions: CLABSI, VAE, and Pressure Injury
Healthcare-acquired conditions (HACs) are largely preventable harms. Three high-yield pediatric critical-care HACs are central line–associated bloodstream infection (CLABSI), ventilator-associated events (VAE) / ventilator-associated pneumonia themes, and pressure injuries.
CLABSI Prevention
Pediatric ICU patients often need central venous access for vasoactive drugs, nutrition, and sampling—exactly the population at CLABSI risk. Prevention is bundle-based:
- Hand hygiene before every line contact
- Maximal sterile barrier precautions during insertion
- Chlorhexidine skin antisepsis (age- and product-appropriate use per policy)
- Optimal site selection and securement; avoid unnecessary femoral lines when alternatives exist
- Immediate sterile dressing care; change damp, loose, or soiled dressings
- Scrub-the-hub before every access
- Daily review of line necessity with prompt removal when no longer required
- Aseptic entry for blood draws and medication administration
Fever in a child with a central line is a sepsis evaluation trigger; do not dismiss it as "just postoperative" without considering CLABSI.
Ventilator-Associated Event Prevention
Mechanically ventilated children are at risk for infectious and noninfectious ventilator-associated complications. Nursing-focused prevention includes elevating the head of the bed when not contraindicated, oral care per protocol, managing condensate so it does not drain toward the patient, minimizing unplanned extubation with securement and sedation targets, using cuff management appropriate to the airway device, and advocating for daily readiness-to-extubate assessment. Avoid unnecessary circuit breaks. Early mobility and pulmonary hygiene, when safe, support recovery without replacing infection-prevention basics.
Pressure Injury Prevention
Critically ill children develop pressure injuries over occiput, ears, sacrum, heels, and under medical devices (BiPAP masks, tracheostomy ties, pulse-ox probes, boards, and tubing). Use a pediatric risk tool such as Braden Q (or institutional equivalent), redistribute pressure on a schedule, keep skin clean and dry, offload devices, and inspect skin with every turn and device check. Immobility from shock resuscitation, edema from capillary leak, vasopressor-related perfusion limits, and malnutrition raise risk—so skin prevention is part of multisystem nursing, not a separate cosmetic concern.
| HAC | High-yield nursing prevention themes |
|---|---|
| CLABSI | Insertion bundle, scrub-the-hub, dressing integrity, daily line necessity review |
| VAE / VAP themes | HOB elevation, oral care, circuit hygiene, sedation/extubation readiness |
| Pressure injury | Braden Q–type risk scoring, turning, device offloading, moisture management |
Integrating the Three Domains at the Bedside
A septic toddler on epinephrine with a femoral central line and invasive ventilation illustrates the section's unity: trending ABGs and lactate guide shock titration; FLACC scores prevent undertreated pain that mimics agitation or hypercarbia; CLABSI and VAE bundles plus occipital offloading prevent new organ insults that feed MODS. The CCRN-Pediatric exam rewards nurses who connect physiology, comfort, and prevention rather than treating them as unrelated checklists.
Common Traps
- Correcting ABG numbers without treating the perfusion or ventilation cause.
- Using an adult numeric pain scale for a nonverbal toddler.
- Leaving a central line in "just in case" after vasoactive drugs and TPN have stopped.
- Ignoring device-related pressure points while focusing only on the sacrum.
A child in septic shock has pH 7.16, PaCO2 30 mmHg, HCO3− 11 mEq/L, and lactate 5.5 mmol/L with delayed capillary refill. Which interpretation and priority pairing is BEST?
Which pain assessment approach is MOST appropriate for a nonverbal 18-month-old in the PICU?
Which nursing action BEST targets CLABSI prevention in a pediatric ICU patient whose shock has resolved and who no longer needs central vasoactive infusions or parenteral nutrition?