A 45 year old male was admitted to ICU following an exploratory laparotomy which showed a ruptured appendix and peritonitis. The procedure began as a laparoscopic cholecystectomy but the initial finding was pus throughout the peritoneal cavity and a normal gallbladder. An open exploratory laparotomy where a ruptured appendix was discovered which was removed and a washout was performed. The patient had a two day history of abdominal pain prior to his admission through A&E. He had no previous medical or surgical history. The patient smoked 20/day and drank alcohol at the weekends. Once admitted to ICU, he was intubated and ventilated on bilevel ventilation and sedated with propofol and fentanyl. In theatre he received two litres of hartmanns solution as a fluid load, however in ICU was commenced on maintenance of normal saline at 100mls/hr. Feeding was ruled out on admission as it was thought that the patient would have extubated the following day. However, the patient was in ICU six days prior to extubation, therefore TPN was commenced. Noradrenaline was used for a MAP above 70mmhg rather than a fluid load.
The patients clinical scenario was more in depth as outlined above. However, these are outside the scope of this case study. The medical and nursing interventions discussed in this assignment is mechanical ventilation, total parental nutrition and vasopressors.
Bilevel ventilation is a relatively new setting. (Mireles-Cabodevila et al, 2009) The ventilator maintains a high pressure setting for the bulk of the respiratory cycle, which is followed by a release of low pressure. (Mireles-Cabodevila et al, 2009) The release to a low PEEP is the expiration phase and aids the elimination of CO₂. The release periods are kept short to prevent derecruitment of alveoli and encourage spontaneous breathing. (Mireles-Cabodevilla et al, 2009) The advantages of bilevel include an increase in mean alveolar pressure with recruitment, haemodynamic and ventilatory benefits and reduced sedation requirements. (Putensen et al, 2006) Analgesia and sedation is not only used for pain relief and anxiety but for mechanical ventilation comfort. (Putensen et al, 2006) This level can reduced to aim of a Riker of 4, which a co-operative, responsive patient. (Putensen et al, 2006) This reduces the need for more vasopressors to maintain a stable cardiovascular system. (Putensen et al, 2006) When first admitted the patients ventilatory settings were:
FiO2 0.4 Rate 12 HiPeep 22 LoPEEP 5 PS 10 CXR showed bibasal atelectasis/consolidation
ABG - pH 7.43 paCO₂ 33 paO₂ 74 HCO₃ 23 BE -0.5
The pH is within normal limits, on the lower end, i.e. between 7.35 - 7.45. Therefore it is normal/alkalotic. The paCO₂ indicates an alkalotic range. This is used to assess the effectiveness of ventilation. (Coggon, 2008) PaO₂ is 74, which is low as normal range is 80-110, which shows hypoxemia. PaO₂ is not interpreted in the patients acid-base status but indicates O₂ binding to haemoglobin. (Coggon, 2008) The HCO₃ is normal. The next step is to match the CO₂, HCO₃ to the pH. The CO₂ and pH is on the alkalotic side of normal. Therefore it shows a respiratory disturbance. (Woodruff, 2009) The next step is to see if either compensation is occurring. To do this, the interpretor must look to see if either the CO₂ or HCO₃ go in the opposite direction of the pH. In which, in the ABG above, you can clearly see that it does although the HCO₃ is within normal range, which means no compensation is occurring. (Woodruff, 2009) The full diagnosis is uncompensated respiratory alkalosis with hypoaxemia. The patient is more than likely hyperventilating with poor gas exchange in view of the CXR. In response to this ABG result ventilatory setting were changed to:
FiO2 0.4 Rate 8 HiPEEP 22 LoPEEP 8 PS 14
ABG post setting change - pH 7.39 paO₂ 103 paCO₂ 36 HCO₃ 22
The rate was changed as the patient was blowing off...