Page 319 - ACCCN's Critical Care Nursing

296 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

tube migration. Intensive care or theatre nursing staff may thorough monitoring and interpretation of variables, and
be a component of the transport team. The admission to managed according to specific needs. During the initial
intensive care requires a team approach, with the partici- two hours of recovery period, 95% of patients will experi-
pation of intensive care nursing and medical staff and/or ence haemodynamic instability. 18
technician input. The immediate postoperative decision
making on patient management is influenced by hand-
over from anaesthetists, settling in procedures and col- Hypertension
16
legial assistance. Admission activities are commonly Hypertension is present in up to 30% of patients
19
divided between nurses, with one nurse taking responsi- initially, as hypothermia, stress responses, pain and
bility for establishing monitoring and haemodynamic hypovolaemia contribute to vasoconstriction. 19-21 When
assessment and management, and a second nurse manag- the systemic vascular resistance is excessive, the high after-
19
ing ventilation and endotracheal tube security, as well as load may contribute to low cardiac output. Rewarming
managing chest drains, gastric tube and urinary catheter. to normothermia with space blankets or heated air
If staffing permits, additional nurses may take responsi- blankets, fluid administration, administration of seda-
bility for documentation, performing arterial blood gases, tion or analgesics, and infusion of IV vasodilators (glyc-
12-lead ECG and providing assistance as required. eryl trinitrate or sodium nitroprusside) are all commonly
used to overcome vasoconstriction when contribut-
The objectives of immediate post operative management 19-21
of cardiac surgical patients may include: ing to hypertension. Occasionally beta-blockers are
used. Hypertension increases myocardial workload and
● optimisation of cardiovascular performance contributes to bleeding.
● reestablishment and/or maintenance of normo-
thermia
● promotion of haemostasis Hypotension
● ventilatory support and management Transient hypotension requiring treatment is common
● prevention and management of arrhythmias at some stage during the postoperative period. Contribut-
● optimisation of organ perfusion ing factors to hypotension include hypovolaemia and
decreased venous return (from polyuria, bleeding, venti-
lation and positive end-expiratory pressure, and excess
Haemodynamic Monitoring and Support vasodilation), contractile impairment (from ischaemia or
Typical haemodynamic monitoring includes an intra- infarction, hypothermia, and negative inotropic influ-
arterial catheter for continuous blood pressure monitor- ences), pericardial tamponade, and vasodilation (from
ing and arterial blood sampling. Cardiac output and excess vasodilator therapy, or as part of an inflammatory
22
preload measurement are achieved most commonly with response to cardiopulmonary bypass).
either a pulmonary artery or central venous catheter Hypotension may present with reduced or elevated
configured for pulse contour cardiac output (PiCCO) preload, reduced or elevated cardiac output, and reduced
monitoring (see Chapter 9). or elevated systemic vascular resistance (SVR). When
hypovolaemia is present, cardiac output will be low and
Preload measures provided by the pulmonary artery
catheter include right atrial pressure (RAP) to approxi- SVR usually high. Hypovolaemia is diagnosed by measur-
mate right ventricular filling, and pulmonary artery pres- ing preload indicators, as pressure (RAP, PAP, PCWP) or
17,19
sure (PAP) to approximate right ventricular systole and volume (ITBVI, GEDVI). Colloids (e.g. normal serum
provide insight into pulmonary vascular resistance and albumin) are generally preferred for volume restoration
18
left heart function. The pulmonary capillary wedge pres- in the postoperative period. Blood returned from the
sure (PCWP) is available to approximate left ventricular cardiopulmonary bypass circuit (‘pump blood’) usually
filling and left heart function. Alternatively, the PiCCO accompanies the patient to ICU, and this should be read-
monitoring system represents preload by intrathoracic ministered at a rate suitable to filling indices and blood
blood volume index (ITBVI) and global end-diastolic pressure.
volume index (GEDVI). In addition, the extravascular Hypotension accompanied by elevated preload and low
lung water index (EVLWI) can demonstrate the accu- cardiac output usually represents cardiac dysfunction or
mulation of interstitial lung water. 17 pericardial tamponade, and the distinction should be
quickly sought. 20,23 When such left ventricular dysfunc-
Cardiac output is measured by either intermittent or
continuous thermodilution via pulmonary artery cathe- tion is present, there is usually compensatory vasocon-
ters, or measured intermittently and then approxi- striction and tachycardia, although heart rate responses
mated continuously on a beat-to-beat interpretation of may be unreliable due to cardioplegia, cold, conduction
21
pulse contour by the PiCCO monitoring system. Cardiac disease and preoperative beta-blocking agents. Inotro-
output measurement can be combined with other pic agents, including milrinone hydrochloride, adrena-
pressure variables to calculate systemic and pulmonary line, dopamine or dobutamine, may become necessary
vascular resistance, stroke volume and measures of ven- (these are covered more completely in Table 20.7 and its
tricular work. accompanying text). When the profile of severe left ven-
tricular dysfunction is persistent (either at the time of
Certain common haemodynamic patterns are seen in the coming off bypass or later in intensive care), intra-aortic
early postoperative phase. These must be detected through balloon pumping may be instituted. ECG assessment for