What is the difference between hypoxic and hypercapnic respiratory failure?

 

Intensive Care Nephrology

ESRD ptns are particularly vulnerable to severe COVID-19 (older age & high frequency of co-morbidity, e.g. DM & HT, in this cohort. The ASN & ISN hv issued guidelines and a list of resources to guide nephrologists to provide life-sustaining DX care. These resources that continue to evolve are frequently updated, including the following: early recognition & isolation of individuals with respiratory Sm(s); ptn separation & cohorting within waiting areas and within DX unit; use of personal protective equipment in DX unit; with added measures for ptns with confirmed/suspected COVID-19.  

Revise please the abbreviation list on:

https://draft.blogger.com/u/0/blog/post/edit/8610857019469578230/4564412989605988372

Q.429. What is the difference between hypoxic & hypercapnic respiratory failure?

 A. Hypoxic Resp. failure c Failure to maintain adequate oxygenation.

Hypercapnic Resp. failure c inadequate ventilation c Co2 retention.

Q.430. What are the possible modes of mechanical ventilation in I.C.U.?

A. Modes of Mch.v.:

I. Volume-cycled: certain “tidal volume” delivered by the ventilator: SIMV (Synchronized Intermittent Mandatory Ventilator) & CMV (Continuous Mandatory Ventilation).

II. Pressure-cycled ventilation: volume is delivered until pre-set maximum pressure is reached = P.C.V. = pressure controlled ventilation.

III. Flow-cycled ventilation : “inspiration” continued until a pre-set flow rate is reached ( P.S.V.) = Pressure Support Ventilation.

CMV: Minimizes the work of breathing done by the ptn., it is used in ptn. é  myocardial ischemia or profound hypoxemia, e.g. COPD & tachypnea ptn..

Q.431. What is the etiology of ARDS?

A. Causes of ARDS:                             

1)   Sepsis  Ø the most common Ø 40 % of cases.

2)   SIRS Ø  Systemic Inflammatory Respiratory Syndrome.

3)   Others Ø Trauma, pneumonia, burn, DIC, near drowning.

Q.432. What is the pathophysiology of ARDS?

A. Pulm. cpll. endothelium dge:Ø é its permeability + influx of fluid into alveoli.

      Neutrophils: activated by [C, IL1,6 ,8,10 & TNFa]Ø inflmm.  mediators & highly active oxidative sp. & proteolytic enz. & metabolites of arachidonic a. wch cn direct-ly injure alveoli & cpll. endothelial cellsØfluid leak é alveoli & edema formation.

      MacrophageØ Clear alveoli fr. neutrophil Ø Resolution of ARDS.

      Thromboxan A2Ø interact é neutrophil Ø Cell aggregation.

      Lipo-oxygenase productsØ Permeability ch.ch.Ø Pulm. Vsc. changes Ø Cpll. Leak.

Q.433. What is the effect of ARDS on renal function?

A. ARDS Ø20-40 %ØRenal dysfunction, due to: [Sepsis- Hemodynamic ins-tability] are accused, but Mechanical Ventilation  itself Ø is FStrong Predictor of Dgx. of R. dysfunction. (See next Q).

Q.434. What is the effect of “mechanical ventilation” on renal function?

A. Mechanical ventilation:  Ö  

1)   ê R.B.F.

2)   Na+ Retention.

3)   ê U.O.

 

Q.435. What else?

 A.  Hypercapnea:Ö

      Renal V.C. + Nor. release Ø ê RBF.

      Systemic V.D. & ê P.R Ø ê RBF.

Q.436. What is the effect of “positive  pressure” on renal function in this situation?

A. Positive pressure:Ø+ ve intrathoracic pressure Øê V.R. Øêeffective circulatory vol. & é pulm. Vsc. Pressure & é R.V. afterload Ø ê C.O. Ø ê RBF.

Q.437.What is the non-hemodynamic factors affecting renal function?

A. Non-hemodynamic: AKI & ALI Ø flattening of epithelial cells in canines & R. tub. apoptosis + Incr. biochemical markers of kid. dysfunction (Rabbit Model).

Q.438. What humoral changes can be expected due to mechanical ventilation?

A. Humoral changes due to mechanical ventilation:

1)   J ADH ð V.C. (mainly rather H2O retention).

2)   J Pl. renin activity ðK G.F.R. due to: K RBF & H2O retention.

3)   K V.R. & K Atrial pressure ð K ANP & K U.O.

- ARDS ð an early manifestation of a SYSTEMIC INFALAMM. process  ð MODF incl. F AKI.    BAL in ARDS ð  { éTNFa, IL1B, IL6} in BAL fluid.

Q.439. Can u please summarize the aforementioned factors affecting renal function in ARDS patient?   <

A. Factors affecting “renal function” in ARDS patients: — ¯¯

1)   Sepsis.

2)   Hemodynamic instability.

3)   Mechanical ventilation:Ø 

      ê R.B.F.

      Na+ Retention.

      ê U.O.

4)   Hypercapnea:Ø

                                 i.    Renal V.C. +Nor. release Ø ê RBF.

                                ii.    Systemic V.D. & ê P.R  Ø ê RBF.               

5)   Positive  pressureØ+ve intrathoracic pressure Øê V.R. Øê effective circ-ulatory vol. & é pulm. Vsc. pressure & é R.V. afterload Ø ê C.O.Ø ê RBF.

6)   Non-hemodynamic : AKI & ALIØ flattening of epithelial cells in canines & R. tub. apoptosis + incr. biochemical markers of kid. dysfunction.

7)   Humoral changes due to mechanical ventilation:

      J ADH ð V.C. (mainly rather H2O retention).

      J Pl. renin activity ðK G.F.R. due to :K RBF & H2O retention.

      K V.R. & K Atrial pressure ðK ANP & K U.O.

Q.440. What is the role of “pulmonary cytokines” in AKI?

A. Pulm. cytokinesØ [TNFa, IL. 1,2,8, ,فيات 128  , Interferon g , granulocyte,  macrophage colony stimulating f.] Ø All hv bn ass. é R. injury in isch./ reperfus-ion model.

Generally, during COVID-19 pandemic, ptns receiving home DX should hv their regular follow-up visits performed via telemedicine rather than in-clinic visits. Moreover, home visits by health care professionals shd be minimized or hold. Pnts should hv at least two weeks of DX supplies with proper medications in case they hv to self-isolation. If in-person visit is clinically indicated, proper infection control measures for the outpatient unit should be applied with limitation of the number of ptns seen per day. Non-urgent procedures should be postponed. The ASN has provided guidelines for nephrologists caring for hospitalized patients requiring DX for ESRD and AKI, adherence to the suggested guidelines is advised:

 

 

Ptns e COVID-19 should be co-localized on a floor or ICU, if possible. Co-localization within adjacent rooms can enable one DX nurse to simultaneously deliver DX for > one ptn. If ptn is in a negative-pressure isolation room, then one HDX nurse will need to be dedicated for the care of that ptn in a 1:1 nurse-to-ptn ratio. If possible, ptns with suspected/confirmed COVID-19 who’re not critically ill shd be dialyzed in their own isolation room rather than being transported to the in-ptn DX unit.

Video & audio streams should be used to troubleshoot alarms from outside the room to minimize the need for DX nurse or the nephrologist to enter an isolation room. CRRT is preferred among critically ill ptns in ICU who hv ESRD/AKI. Even among ptns who’re hemodynamically stable and who cd tolerate intermittent HDX (IHD), CRRT or prolonged intermittent renal replacement therapy (PIRRT), also called sustained low-efficiency DX (SLED), should be performed instead, depending upon machine & staffing availability. As CRRT or PIRRT can be managed without 1:1 HDX support. This would potentially help decrease wastage of personal protective equipment and limit exposure among HDX nurses. With CRRT capacity overwhelming, CRRT machines can be used to deliver prolonged intermittent ttt (eg, 10 hs rather than continuous) with higher flow rates (eg, 40-50 mL/kg/h). This will enable CRRT machine to be more available for care of another ptn after terminal dysinfection. If available, HDX or CRRT machines are scarce, clinicians may need to consider ttt of AKI with PD. Ptns with suspected/confirmed COVID-19 who develop AKI, and an emphasis should be placed on optimizing volume status to exclude and ttt pre-renal (functional) AKI while avoiding hypervolemia, wch may worsen ptn’s respiratory status. Ptns with AKI with no need for DX should be managed on a limited contact bases. Physical evaluation and U/S studies should be coordinated e primary/consulting teams to minimize contact, as much as possible. Ptns receiving ACEi/ARBs) should continue their therapy (unless there’s a contra-indication e.g. hyperkalemia or hypotension). There’s no evidence that stopping ACEi/ARBs limit the severity of COVID-19. Pts e stage 4/5 CKD who’re referred for DX access placement should undergo their procedures as planned (not hv their planned procedure deferred).