Case Studies

Author: Dr David P Coates MB BS FRCA , Consultant Anaesthetist, Bristol Royal Infirmary, England

Introduction

An 89 year-old man was admitted with a peri-prosthetic fracture of the femur following a fall 20 hours prior to admission. The patient had a hip replacement, 10 years previously, controlled left ventricular failure, aortic stenosis (as demonstrated by echo) with a 60mmHg gradient and chronic obstructive pulmonary disease (COPD). The patient’s medications included loop diuretics and calcium supplements for osteoporosis. On admission the patient was diagnosed with pneumonia with a temp of 37.6° C.

Lab results on admission demonstrated an incipient renal impairment with blood creatinine levels of 1.92 mg/dl (170 mcg/L ) and anaemia with Hb of 8.1g/dl and MCV of 80 fL.

Clinical findings suggested that the patient was dehydrated and prior to operative procedure the clinicians decided to optimize his fluid status.

Peri-Operative Management

On admission the patient received morphine 10mg PO that caused significant drowsiness and very little response to questions or even moving the fractured leg. It was decided that prior to the surgical procedure the patient should not receive more analgesia. The patient was treated with oxygen 4L/min by mask and, based on a clinical estimate; 3 L of normal saline were prescribed for the patient over the next 12 hours pending the availability of an operating slot.

Six hours later, the patient was connected to NICOM prior to induction with alfentanil 250 mcg, Target Controlled Intravenous Anaesthesia (TCIVA) Propofol 1 mcg/ml.

Entropy: RE and SE decreased to 35 after cumulative TCIVA Propofol 35 mg

By this time, the patient had received 1.5 L of crystalloids out of the 3 L that had been prescribed. In order to decide whether the patient needed additional fluid, 15 minutes post induction, and before the start of surgery, a fluid challenge was conducted using 300ml suspended blood cells (SAGM) over 10 minutes.

NICOM Results

During and immediately after the blood infusion the Cardiac index (CI) decreased from 4.5 L/min/m² to 2.0 L/min/m². This suggested that, allowing for the effects of the very light anaesthesia, the patient was not fluid responsive and would not benefit from more fluids (Figure 1).

_{Figure 1 – Negative effect of fluid challenge on cardiac index}

Surgery

No regional anaesthesia was used and no additional opioid was indicated by the Entropy values that were consistently less than 48. The thigh was extensively opened to reveal a ‘bi-valve’ fracture (30 cm long) that required plating and cabling.

Surgery proceeded uneventfully with mean blood pressure (non invasive) of 69 mmHg, the patient was stable throughout the 3 hour surgery (CI 2.5 L/min/m²) with an estimated blood loss of 600-700 ml. The patient received another 300 ml blood and 300 ml Voluven (6% hydroxyethyl starch 130/0.4 in 0.9% sodium chloride injection) during the procedure. Chirocaine 0.75% (30ml) was infiltrated in the wound by the surgeon at the conclusion of the procedure.

Recovery

The patient returned to the pre-operative level of consciousness (drowsy) 15 minutes after stopping TCIVA. There was no requirement for supplementary analgesia for at least 3 hours. The wound drains accumulated less than 100ml in the next 3 hours. A second fluid challenge (200 ml Voluven 6%) was performed soon after arrival in recovery under NICOM’s guidance, this time CI increased from 2.75 to 4.2 L/min/m² indicating that the patient was now fluid responsive and potentially would gain an increase in cardiac output when given additional fluids. Subsequent transfusion (blood / colloid) was directed by NICOM. The patient was transferred back to orthopaedic ward after receiving an additional 1.5L

Discussion

This case demonstrates the importance of hemodynamic monitoring for fluid optimization. At first, based on clinical assessment, a 12-hour fluid requirement of 3L crystalloid was made. However, about half-way into the plan a fluid challenge performed under NICOM monitoring demonstrated that the patient would not benefit from additional fluids and in fact, further fluids may worsen organ perfusion and tissue oxygenation. With this insight, the clinician was able to deduce on which part of the Starling curve the patient’s heart was operating at different points in time during the day and to optimize fluid management accordingly.

Hemodynamics manifest very differently from patient to patient and from one clinical scenario to another. Prescribing fluids based on generic ‘rule of thumb’ formulae is frequently the best we can do, however this is not trivial and in many cases leads us to make compromises or prescribe suboptimal fluid regimens. The advent of continuous non-invasive hemodynamic monitoring enables us to assess our clinical intuition very easily, make insightful decisions and fine tune as we go as often as necessary until the patient is stabilized.

Cheetah Medical wishes to thank Dr Coates for the contribution of this case